Title of Invention	"REMEDIATION PROCESS AND APPARATUS"
Abstract	Process for remediation of a fluid contaminated with alkylene oxide, comprising contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, conferring intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide; preferably a process which is part of a process for the conversion of ethylene to ethylene oxide with formation of byproducts, water and C02, wherein the product EO is isolated from the recycle gas and C02 is removed from the recycle in the C02 removal section and is remediated by the process as defined; apparatus for remediation of said fluid which comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber; preferably as part of an apparatus for the conversion of ethylene to EO, more preferably part of an EO/EG apparatus, for the conversion of ethylene to ethylene oxide in which the apparatus is positioned in the vent stream.

Title of Invention

"REMEDIATION PROCESS AND APPARATUS"

Abstract

Process for remediation of a fluid contaminated with alkylene oxide, comprising contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, conferring intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide; preferably a process which is part of a process for the conversion of ethylene to ethylene oxide with formation of byproducts, water and C02, wherein the product EO is isolated from the recycle gas and C02 is removed from the recycle in the C02 removal section and is remediated by the process as defined; apparatus for remediation of said fluid which comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber; preferably as part of an apparatus for the conversion of ethylene to EO, more preferably part of an EO/EG apparatus, for the conversion of ethylene to ethylene oxide in which the apparatus is positioned in the vent stream.

Full Text	REMEDIATION PROCESS AND APPARATUS The present invention relates to a process for remediating a fluid containing minor amounts of ethylene oxide, apparatus therefor and the use thereof, in particular in remediating a CO2 vent stream from an ethylene oxide (EO) process. Background of the Invention Ethylene oxide is a substantial item of chemical commerce having utility both as a sterilisation agent and as a fumigant, but primarily as a starting material in the manufacture of a diversity of products such as antifreeze, cosmetics, lubricants, plastics and surfactants. The major process for manufacture of ethylene oxide is by the silver-catalysed oxidation of ethylene. Typically, the stream exiting the reactor comprises small quantities of ethylene oxide (for example 0.5 to 5 mol%) together with large amounts of residual gases including unconverted ethylene and oxygen as well as appreciable quantities of carbon dioxide, low molecular weight hydrocarbons 'and inert gases such as nitrogen. Customarily, the ethylene oxide product is recovered from the residual gases by absorption in water followed by processing of the ethylene oxide-fat absorbent in a variety of ways including fractionation, scrubbing, stripping and the like. An ethylene oxide plant may also be the site of production of monoethylene glycol derived by hydration of the product ethylene oxide. In such a plant, commonly the product ethylene oxide having been isolated by water absorption is then hydrated in a separate reactor. Variations of this process have been proposed in the past. GB-A-4 98,119 for example is an early proposal where the hydration may be effected thermally or, preferably, using an acidic catalyst which is added to the water absorbent. The glycol forms on heating the absorbent solution after the ethylene oxide is absorbed and the resulting solution is recycled as liquid absorbent until the glycol content is relatively high and is recovered. EP-A2-776890 proposes another variant where ethylene oxide absorbed in a solution containing ethylene carbonate and ethylene glycol is reacted with carbon dioxide to the carbonate form and hydrolysed with a separate catalyst. The Example shows that treatment of an ethylene oxidation product stream containing 3 mol% ethylene oxide left 100 ppm in the residual gases, following the particular absorption step and conditions used. DE-A1-19843721 uses ethylene oxide wash water as absorbent prior to the hydration step. The Example shows absorption in wash water of ethylene oxide from a gas mixture containing 2.7 mol% ethylene oxide, leaving 10 ppm ethylene oxide to be lost in the residual gases. The residual gases that remain after recovery of the bulk ethylene oxide product, are recycled to the ethylene oxidation reactor. Customarily, a small bleed stream is withdrawn from the recycled gases to prevent build-up of impurities such as argon, ethane or nitrogen in the recycle gas loop. A side stream, being part or all of the recycle gas, is usually scrubbed with an aqueous CO2 absorbent for removal of excess CO2 which is subsequently stripped from the absorbent and typically is vented, or if desired, recovered for use or sale as a by-product. A problem arises particularly in manufacturing plants of large capacity in that during scrubbing of the recycle gas side stream small amounts of hydrocarbon are dissolved and/or entrained in the CO2 absorbent and ultimately vented with the carbon dioxide. US 3,867,113 discloses a process improvement which is now conventional in EO processes, wnereby the CO2~fat absorbent obtained by contacting a sidestream from the recycle stream with a CO2 absorbent, is flashed to form a hydrocarbon - containing vapour stream and a hydrocarbon - lean fat absorbent, and the fat absorbent stripped to produce a CO2 stream substantially free of hydrocarbon which is suitable for venting, or use. Nevertheless, in conventional EO plants, despite flashing the fat absorbate, a small amount of residual EO remains in the vent gas from the CO2 stripper. In order to keep vented EO as small as possible for environmental reasons, the vent gas can therefore conventionally be subject to incineration. Such incineration can for example occur within a catalytic incinerator whereby one or more catalyst beds are heated to.high temperatures (in ranges from approx 300CC to 800°C) and various heat exchange mechanisms are incorporated to minimise energy loss and improve efficiency. This therefore presents a convenient solution which is effective in operation and, as an "end-of-pipe" process, requires minimal alteration to the existing process line up. Being operated at high temperatures and requiring the need for catalyst will however inevitably mean periods of time in which the incinerator cannot function through the need for maintenance, repair, replacement of catalyst, etc. Where environmental contamination is measured on an average basis, say as EO vented per week, such incinerator-downtimes are negligible, but increasingly environmental concerns require constant monitoring of EO venting with hourly measurement of contamination, and this means that the conventional incinerator system may not comply with environmental regulations all of the time. There is therefore a need to provide for an effective reduction of EO in CO2 vent gas from an EO plant, with or without the use of additional incineration, in which reduction is constantly maintained. The concentration of EO in vent gas is moreover dependent on a number of factors including the percent of recycle stream which is treated as a sidestream, and the operating conditions of the CO2 absorber and EO- absorber. A further need is therefore to provide a system for independent control of EO in CO2 vent gas from an EO plant, whereby the level of carbon dioxide to be vented can be varied without compromising the reduction in EO emission. Summary of the Invention We have now surprisingly found that chemicals present during CO2 absorption in the carbonate section may also be highly effective in catalysing the reaction of EO to glycol, under certain specific conditions. Even more surprisingly we have found that these specific conditions may be conveniently provided without major alteration of an existing EO plant, or without major design changes in a new plant, and this is of course of major importance as significant changes would affect other control and emission measures. While the combination of absorption of olefins and hydration to glycol is utilised extensively, eg in the combined production of ethylene oxide and monoethylene glycol as noted above, use of absorption and hydration has never previously been proposed to remove, for example, the very low levels of ethylene oxide that occurs as a contaminant in CO2~rich vent gas. Moreover, the removal can be continuously and effectively achieved in preferred embodiments without the addition of any other additive than the aqueous absorbent conventionally utilised in a commercial EO process for CO2 absorption. This is the more surprising since the contaminant levels of EO remain following an extensive absorption process in the conventional production of EO and it would normally be expected that a different or more rigorous teatment, such as the incineration of previous proposals, would be necessary to remove the low levels remaining. Against the conventional proposal of incineration, the process of the invention allows the removal of ethylene oxide from CO2 vent gas more cheaply, more reliably, and on a continuous basis to meet current day permit control requirements. Contamination of gas streams by alkylene oxides may also occur in ether commercial operations. However the most preferred application of the process, control system and apparatus of the present invention is the reduction of EO in CO2- vent gas, and throughout the specification the present invention will most frequently be described with reference to this use. In the broadest aspect of the invention there is therefore provided a process for remediation of a fluid contaminated with up to 1000 ppmv of alkylene oxide, comprising contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, to confer intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide, wherein the fat absorbent has a pH in the range of from 7 to 11. In a further aspect of the invention there is provided a method for calculating a required residence time of fat absorbent in a process for remediation of fluid as herein defined, from the moment of fluid absorption to the moment of fluid stripping to generate lean absorbent, in manner to convert a desired amount of ethylene oxide as herein defined. In a further aspect of the invention there is provided an apparatus for remediation of fluid as herein defined contaminated with an amount of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber, wherein the holding unit is shaped and configured and/or provides internals whereby fluid flow through the apparatus approaches plug flow. Detailed Description of the Invention The process of the invention comprises contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, conferring intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide. Absorption may be of all or part of the contaminated fluid which is contacted with absorbent, and is typically of part of the contaminated fluid. Preferably alkylene oxide is converted to glycol in the process of the invention. In a particular advantage glycol can be separated in subsequent stages as a liquid condensate, yielding remediated fluid. Reference herein to a fluid is to a fluid stream, reservoir or the like and is preferably a fluid stream. Fluid may be of gas or liquid form, such as a gas, vapour or condensed vapour, or other liquid. Preferably the fluid comprises a gas stream, comprising an amount of alkylene oxide. Alternatively or additionally the fluid may comprise condensed vapour, such as condensed steam, comprising an amount of alkylene oxide. Preferably the fluid comprises a CO2 containing stream, especially a C02~rich stream, contaminated with ethylene oxide (EO), more preferably from the partial oxidation of ethylene to ethylene oxide by the EO process in an EO unit in which the CO2 is intended for venting. A C02~rich stream suitably contains up to 10 mol%, for example in the range of from 0.1 to 6 mol%, preferably 0.5 to 6 mol%. Suitable examples are from 3 to 6 mol% CO2, but also 0.5 to 3 mol%. In a particular advantage the contaminated fluid is absorbed as hereinbefore defined and provides a suitable medium for combining contaminated fluid and converting alkylene oxide from other sources. Preferably therefore the process of the invention comprises contacting fluid and absorbent as hereinbefore defined and simultaneously or subsequently additionally combining one or more additional alkylene oxide contaminated fluids for conversion of alkylene oxide as hereinbefore defined. Such additional streams may for example include condensed steam which has been used for scrubbing or the like, such as absorber overhead gas knockout, absorbent which has been used to absorb alkylene oxide from other streams and the like. Combining fluids is preferably carried out with mixing, more preferably to provide a uniform fat absorbent composition. The process is suitable for converting alkylene oxide present in any amount up to 1000 ppmv, for example in the range of from 0.1 ppmv up to. 1000 ppmv, preferably 0.1 ppmv to 500 ppmv. It is of particular significance that the process is able to convert residual amounts of ethylene oxide of, or in excess of, 0.1 ppmv up to 40 ppmv. The process may be operated at any desired conversion. Conditions may be chosen to give a desired conversion depending on the level of alkylene oxide present. It is a particular advantage that the process is characterised by a very high conversion whereby the absorbed fluid may be substantially completely remediated by the process of the invention, preferably the process is characterised by conversion substantially greater than or equal to 50%, more preferably substantially greater than or equal to 80%, for example from 88% to substantially complete conversion, preferably from 90% to 99.9999%, more preferably from 95% to 99.999%. This enables reduction of alkylene oxide to below 1 ppmv and especially to below 0.1 ppmv. Suitably the process comprises in a further stage desorbing the absorbed fluid, thereby generating a lean absorbent stream, separating the alkylene oxide conversion product and recycling the lean absorbent. Preferably the process comprises separating any volatile hydrocarbons by flashing the fat absorbent, prior to desorbing the absorbed fluid by stripping. Preferably the absorbed fluid is a gas and the process comprises separating the alkylene oxide conversion product by phase separation for example condensation or knockout to form condensed liquids and a remediated fluid which is substantially free of alkylene oxide, preferably having a maximum residual alkylene oxide level of 1 ppmv or less, more preferably of 0.1 ppmv or especially less than 0.1 ppmv. Aqueous absorbent may be selected from any aqueous solution which is not deleterious to catalysts or other components if any, present in other stages of the process. Preferably the absorbent is selected from alkali metal carbonates such as sodium (bi) carbonate, potassium (bi) carbonate; water; methyl alcohol; acetone; and solvents such as propylene carbonates or ethylene carbonates; and the like; and mixtures thereof with other absorbents or fillers. More preferably the absorbent is a CO2 absorbent. The absorbent is especially an alkali metal carbonate. In a typical absorption system the lean absorbent solution may contain for example K2CO3 and KHCO3 in a ratio of about "70:30. When CO2 - containing gas is passed through the absorber, reaction of CO2 with the carbonate solution results in conversion of up to about 90% K2CO3, leaving about 10% KHCO3. The absorbent may contain activators and the like for improved absorption. Known and preferred activators include potassium or sodium salts of metal oxides such as vanadate, chrornate and borate and mixtures thereof. Preferably the absorbent is selected from commercially available CO? absorbents such as Catacarb or Benfield solutions. Benfield absorbents are disclosed for example in GB 1415036, US 3863003, US 3907969, the contents of which are incorporated herein by reference. The process is suitably carried out under conditions conducive to conversion of alkylene oxide. Conditions conducive to conversion of alkylene oxide include conditions selected from low or high pH, presence of activators, elevated temperature, extended residence time, and the like. alkaline and have a the fat absorbent is neutral to alkaline having a pH in the range of from 1 to 11, most preferably 9 to 11, and especially 10 to 11. The fat absorbent may be activated by the presence of an amount of activator selected from substances which promote or catalyse the conversion of alkylene oxide. Activator is preferably derived from an available process component, but may be added to the absorbent or the fluid. It is possible that CO2 present in a fluid to be remediated, for example, may promote conversion of alkylene oxide by virtue of its acidity in solution or by virtue of an activating effect. We have observed the conversion of ethylene oxide to glycol to take place with high conversion by a modification downstream of the CO2 absorption stage in the EO process, in which CO2, absorbent, activators and water are present as fat absorbent, the modification comprising intentionally increasing fat absorbent residence time beyond that required for conventional absorption and separation. Without being limited to this theory it is thought that the conversion of alkylene oxide to glycol may be facilitated by one or a number of conditions selected from the presence of activators, alkali, and/or other catalyst and water both for activation and being consumed in the conversion, and conditions such as elevated temperature, extended residence time and the like. The rate of conversion depends on conditions of temperature, presence of activators and the like, and this in turn determines the required residence time for conversion. The period for intimate contact of absorbent and alkylene oxide is conveniently expressed as the residence time of the fat absorbent, being the time between absorption and desorption stages. The required residence time for conversion of alkylene oxide depends on a number of factors including amount and concentration of alkylene oxide and activator prevailing temperature and pressure and the like. Typically residence time in prior practice conventional EO units is up to 3 minutes in the C02 absorber, 1 minute in piping and a further 3 minutes in the flasher. Preferably the absolute residence time in the process of the invention is greater than or equal to 11 minutes, more preferably greater than or equal to 15 minutes, more preferably is in excess of 18 minutes, for example up to 60 or 120 minutes. Most preferably residence time is in the range 18 to 67 minutes, such as 20 to 50 minutes. The residence time varies according to the process or operation from which the contaminated fluid is derived. It is therefore convenient in some cases in which the application of this invention is a retrofit, to express residence time as additional residence time representing the increase over prior practice. For example in an absorption stage of a conventional process, additional residence time represents the increase over the minimum residence time required to absorb and desorb fluid, including conducting fat absorbent to a flasher, flashing hydrocarbons and conducting the flashed absorbent to a desorber to desorb fluid. Expressed in this way preferably the process of the invention provides an additional residence time of greater than or equal to 4 minutes, more preferably greater than or equal to 8 minutes, more preferably in excess of 11 minutes, for example up to 53 or 113 minutes. Most preferably additional residence time is in the range 11 to 60 minutes, such as 13 to 43 minutes. Preferably the process of the invention is part of a continuous process whereby residence time is conveniently expressed as total fat absorbent volume divided by total fat absorbent flow rate, and a desired residence time is provided by selecting volume or rate accordingly. Preferably the fat absorbent is characterised by substantially uniform flow rate, more preferably substantially plug flow, thereby conferring narrow residence time distribution. By this means a desired conversion can be attained at a lower lean absorbent volume or shorter residence time than would otherwise be possible. The temperature of the fat absorbent may be any temperature conducive to conversion of alkylene oxide. Suitably fat absorbent temperature is in the range of from 80°C to 140°C, more preferably 90°C to 130°C. Preferably the fluid containing the contaminant level of alkylene oxide is absorbed from a recycled gas stream or a side stream thereof which is contacted with absorbent as hereinbefore defined, and a desired amount of fluid is absorbed and separated from the recycle stream or side stream thereof. The amount of fluid absorbed from the recycle or side stream determines the amount of alkylene oxide to be converted and thereby the required conditions such as residence time for fluid remediation. The absorption of fluid is typically both temperature and time dependent and is given as a measure of absorption efficiency. In the EO process a desired volume o'f CO2, containing an amount of C1 and C2 hydrocarbons, is absorbed from the recycle stream at a desired absorber temperature to achieve the required operating protocol in terms of conversion of the ethylene to EO and to ensure a desired catalyst lifetime. At a temperature of from 70°C to 130°C or 140°C the CO2 absorber absorbs in the region of 50% to 99.9% CO2 from the feed stream to the absorber, i.e. operates at a CO2 absorption efficiency of 50% to 99.9%. Preferably the CO2 absorber absorbs approximately 75% to 95% of CO2 from the feed stream i.e. operates at a CO2 absorption efficiency of 75% to 95% at a temperature in the range 70°C to 110°C and the remainder is returned to the recycle stream. We have however found that at this temperature the conversion of alkylene oxide according to the present invention is non-optimal, for example is less than 90%. For treatment of a CO2 vent gas, if the temperature of CO2 fat absorbent in the absorption stage is elevated to a temperature in the range of from 80°C to 140 °C, more preferably 90°C to 130°C as hereinbefore defined, then a higher conversion in the range 90% to substantially complete conversion of the contaminant alkylene oxide may be obtained. There is therefore a conflict in the optimum temperature for absorption of fluid at a desired fluid absorption efficiency, and that for conversion of alkylene oxide at a desired conversion according to the present invention, and it is therefore not appropriate to simply increase the temperature of the fluid absorption, since this reduces the absorption efficiency. In a preferred embodiment therefore the invention comprises a process for remediation of a fluid'as hereinbefore defined contaminated with up to 1000 ppmv of alkylene oxide comprising contacting the fluid with an aqueous absorbent at an absorption efficiency in the range 50% to 99.9% preferably 75% to 99.9% most preferably 90% to 99.9%, to yield a fat absorbent having absorbed fluid, if required heating the fat absorbent, and maintaining for a desired residence time for conversion of alkylene oxide, wherein the process includes subsequently desorbing absorbed fluid, cooling the lean absorbent to a temperature for the required absorption efficiency and recycling to the absorption stage. Preferably the process is for remediating a C02~rich stream and comprises absorbing at a first temperature in the range of from 60°C to 110°C, preferably 70°C to 110°C, and heating, if required to a second temperature in the range of from 80°C to 140°C for example 90°C to 130°C for conversion of alkylene oxide, desorbing and cooling to a first temperature as hereinbefore defined. The fat absorbent may be heated by any desired means and is preferably heated with a heat exchanger or other heat source in a way that is energy neutral to the process as a whole. In a particularly advantageous embodiment of the invention, fat absorbent is provided as a fluid stream whereby it is conducive to heat exchange. Preferably therefore heating is by heat exchange with a further process stream, such as steam, lean absorbent, stripper overhead and the like or a combination thereof, more preferably by heat exchange selected from: a fat / lean exchanger interchanging heat between hot aqueous lean absorbent from which fluid has been desorbed and fat absorbent with absorbed fluid which requires heating; a fat absorbent / fluid exchanger interchanging heat between hot desorbed fluid and fat absorbent with absorbed fluid which requires heating. Alternatively or additionally heating is by using an independent source such as: steam from another process stage, in particular steam for venting (waste steam) or cooling to water (process steam); or very hot condensate such as from the EO stripper bottom (lean absorbent); or other in-process heat sources such as EO stripper overhead and the like; and combinations thereof. Preferably heat exchange comprises a line-up of suitable available heat sources and cooling sources. Preferably the total heat exchange time is adapted for the heat exchange area and exchange volumes, and is for example 1 to 6 minutes. Preferably however heat exchange is with a fat absorbent/fluid heat exchanger such as a fat absorbent / CO2 heat exchanger. The temperature of fat absorbent leaving the heat exchanger is regulated by altering heat input to the exchanger by known means such as adjusting the flow rate of the interchange stream, such as the lean absorbent or desorbed fluid, or adjusting heat input to the interchange stream source, such as the fluid stripper or the like. Temperature regulation may be manual or automatic, for example the process may comprise a control mechanism which alters heat input to the fat absorbent in response to detecting a change in amount of alkylene oxide in t.he, fluid, or change in volume or flow rate of absorbed fluid. The fat absorbent stream containing absorbent, fluid, alkylene oxide conversion product and any unconverted alkylene oxide typically also contains an amount of volatile hydrocarbons such as methane, ethylene and ethane. In a preferred embodiment the process of the invention includes flashing the fat absorbent at reduced pressure) to remove volatiles before forwarding the fat absorbent to the CO2 stripper for contact with stripping medium. Volatiles removal may' be facilitated by adding a flashing agent and/or adding a stripping agent as known in the art. Stripping medium is selected from any suitable stripping gases such as methane, ethane, nitrogen, steam, air, O2, CO2 and the like. In the case that the process of the invention is part of a process for ethylene oxide/ethylene glycol (EO/EG) production, the condensate from the stripping of the fat absorbent stream, which comprises ethylene oxide conversion product glycol, may be sent directly for glycol recovery, or combined with the condensate from the EG production and forwarded for dewatering and glycol recovery or any other treatment in a combined or separate stage, or alternatively may be sent to waste. Preferably the heat of the stripped fluid stream is removed before venting the fluid or forwarding for further use. Heat removal is typically by heat exchange with the fat absorbent stream as hereinbefore defined, followed by aftercooling with different means, as conventional (chiller, cooler and the like). Accordingly the process preferably comprises regulating the flow of lean absorbent contacting the contaminated fluid, and regulating the residence time of fat absorbent, for example by addition.of inert gases and like techniques as known in the art for reduced flow rate and increased residence time, and/or comprises regulating the temperature of fat or aqueous absorbent by heat exchange or other means as hereinbefore defined. In a further aspect of the invention there is provided a method for calculating a required residence time of fat absorbent in a process for remediation of fluid as hereinbefore defined, from the moment of fluid absorption to the moment of fluid stripping to generate lean absorbent, in manner to convert a desired amount of ethylene oxide as hereinbefore defined. Preferably the method comprises compiling a set of kinetic data for the process in question relating to reduction in residual ethylene oxide with increasing residence time at a number of temperatures, compiling a relation as in Figure 5 and determining an appropriate temperature and/or time for operation for a particular ethylene oxide concentration in fluid to be remediated. The process of the invention has highlighted concerns over incidental release of EO in vent gas. In a further embodiment the process of the invention comprises an additional end-of-pipe incineration of the fluid stream after conversion of alkylene oxide as hereinbefore defined. End-of-pipe incineration which is the current practice for remediating a CO2 vent stream and is effective for combusting any levels of EO or other hydrocarbons, is not suited for full time operation, for the reasons described above. Preferably therefore the process provides for additional permanent, temporary or semi permanent end-of-pipe incineration. This is useful in the event of accidental release of high levels of ethylene oxide to the fluid stream for example in the case of process malfunction. It is also useful in the event of incidental increase of alkylene oxide levels, for example in processes adopting minimal additional residence time to achieve initial alkylene oxide reduction or alkylene oxide reduction at usual loading levels, and requiring an additional end-of-pipe solution to complete alkylene oxide reduction or in times of higher fluid loading or higher alkylene oxide contamination. In a further aspect of the invention there is provided a process for the conversion of ethylene to ethylene oxide (EO) with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle and the CO2 gas stream is remediated by the process as hereinbefore defined. Preferably the process comprises in an additional stage the conversion of product EO to EG. The amount or volume of fluid to be remediated and the concentration of alkylene oxide therein determine the amount or volume of alkylene oxide to be converted. The fluid absorption efficiency, for example CO2 absorption Inefficiency for absorption from the recycle stream of the EO process, and the concentration of alkylene oxide, for example in the recycle stream, determine the amount of alkylene oxide absorbed with fluid, for example C02 from the recycle stream and thereby the requirements for the process of the invention. However it would be desirable to operate the remediation process of the invention without impacting on the other stages of the process of which it forms a part. In a particular advantage of the invention we have found that we are able to operate the process of the invention at increasing alkylene oxide levels in the contaminated fluid stream and still obtain a remediated fluid stream having a desired maximum residual alkylene oxide level of 1 ppmv or preferably 0.1 ppmv by selection of operating conditions as hereinbefore defined. In a preferred embodiment of the invention there is therefore provided a process for remediation of a fluid contaminated with an amount of up to 1000 ppmv alkylene oxide, especially a CO2 vent gas in an EO unit, comprising contacting fluid with aqueous absorbent to form fat absorbent comprising fluid and alkylene oxide in any volume or at any rate, and converting alkylene oxide, wherein the process comprises determining suitable conditions at any time, selected from amount or temperature of aqueous absorbent, residence time or temperature of fat absorbent or the like, to convert a desired amount of alkylene oxide and maintain at a residual alkylene oxide level less than 0.1 ppmv, and without affecting volume or rate of further fluid absorption. Preferably the process comprises selecting an appropriate combination of fat absorbent temperature and residence time at any given moment, optionally together with incineration. Preferably the process for the conversion of ethylene of the invention is operated as known in the art in a multitubular fixed bed reactor, and comprises reacting gaseous ethylene and oxygen over a catalyst at a temperature in the range of 200°C to 300°C, and at a pressure in the range of 12 to 25 bara. The EO/EG process is illustrated as a block scheme in Figure 1. In Figure 1 and in the corresponding process sketch of Figure 3 the conventional C02 removal is illustrated. Ethylene and water are supplied (1) to the multitubular fixed bed reactor (2) where the EO reaction takes place by the silver-catalysed oxidation of ethylene to ethylene oxide. A large gas stream flows through the reactor tubes (2), which contain the catalyst. The heat generated by the chemical reaction is removed by evaporation of coolant at the shell side of the reactor, which is used for the production of steam. The generated steam is used as heat medium in the glycol reaction and recovery sections of the plant, in the case of a combined EO / EG process. Typically, the stream (3) exiting the reactor comprises small quantities of ethylene oxide together with large amounts of residual gases including unconverted ethylene and oxygen as well as appreciable quantities of carbon dioxide, low molecular weight hydrocarbons and inert gases such as nitrogen. Reaction products (ethylene oxide and water) are removed in the EO recovery section (4). Unconverted oxygen and ethylene are recycled back into the reactor via the recycle stream (5). In the EO recovery section (4), EO is recovered from the gaseous reactor effluent by absorption in water at a temperature in the range of from 15°C to 30°C (EO lean absorbent) and is processed in a variety of ways including fractionation, scrubbing and stripping at a temperature in the range of from 100°C to 135°C and the like. The diluted aqueous EO solution (EO fat absorbent) is concentrated in the EO stripper (part of 4, not shown) where an EO/water mixture leaves over the top and a lean absorbent from the bottom. After cooling the EO lean absorbent is-returned to the EO- absorber. A slipstream of the lean absorbent (not shown) is sent to the glycols recovery section for recovery of glycols that are formed by hydration of a small fraction of the absorbed EO. Product EO is removed as high purity EO or sent as feed to an EG reaction unit for reaction to form ethylene glycol (EG). A small bleed stream (6) is withdrawn from the recycled gases (5) to prevent build up of impurities such as argon, ethane or nitrogen in the recycle gas loop. The bleed stream can be used as fuel gas, and preferably all or part of the bleed stream is forwarded for ethylene recovery. A side stream (7), part or all of the recycle gas, is sent to the CO2 removal section (8) in which it is scrubbed (9) with an aqueous CO2 absorbent for removal of excess CO2 forming a CO2 fat absorbent which is subsequently flashed for light ends removal (10), CO2 is stripped (11) from the absorbent and typically is vented (12), or if desired, recovered for use or sale as a byproduct . Figure 3 illustrates this process in more detail, showing the side stream (7) conducted via a heat exchanger (90) in which it is contacted with and cools recycled hot lean carbonate (110). By this means the temperature in the CO2 absorber can be regulated to determine the desired degree of uptake of CO2 - high levels of absorption require cooling of lean absorbent. Residual unabsorbed gases exiting from the absorber overhead (91) are cooled and conducted to gas knockout drum (92) from which the overhead gases (93) are returned to the gas loop, and to the EO reactor (2) and the bottom stream (94) comprising condensed water is combined in the stripper (10) with fat absorbent (95) from the CO2 absorber. CO2 fat absorbent (95.) exits from the bottom, of absorber (S) and passes to flasher (10) from which volatiles (100) leave as overhead, and liquids including fat absorbent (101) leave at the bottom and enter the stripper (11). Lean absorbent (110) leaves at the bottom. Gaseous CO2 and steam forms the overhead (111), and is conducted to the overhead knockout (112) from which CO2 is vented (12) and condensed water (113) recycled to stripper (11) and/or sent for treatment. Returning to Figure 1 the recycle stream (5) containing unconverted oxygen and ethylene and other residual gases together with overhead gases from the CO2 removal unit (8) are recycled back to the reactor (2). Fresh feeds are supplied in the recycle stream (1). The oxygen is thoroughly mixed with the hydrocarbon recycle gas stream in a specially designed mixing device having safeguarding mechanisms and oxygen cut off and immediate nitrogen purge for safety. A ballast gas is used to ensure a maximum allowable oxygen concentration in the recycle gas loop. It is a particular advantage that the EO process may be minimally modified by the process of the invention. Preferably the process is modified by increasing the volume of lean absorbent in the CO2 removal section, to confer increased residence time and optionally additionally heating the fat absorbent in the CO2 removal section, for example by diverting a process stream such as the CO2 stripper overhead for heat exchange with the. fat absorbent. Additionally the process may include a mixing stage for mixing additional contaminated fluid streams. The increase in volume of lean absorbent which is reguired depends however on plant size and may be determined by those skilled in the art. A typical example for a world class year 2000 plant would require additional lean absorbent volume in the range of from 50 m3 to 350 m3, more preferably 80m3 to 300 m3, for example 100 m3 to 150 m3, depending on the capacity of the EO process, for example 300 - 400 kT/a. The CO2 removal section in a modified EO/EG process incorporating the process of the invention is illustrated as a block scheme in Figure 2 and as a process sketch in Figure 4. In this case the side stream (7), part or all of the• recycle gas, is sent to the CO2 removal section (8) in which it is scrubbed (9) with an aqueous CO2 absorbent for removal of excess CO2 as in the conventional process of Figures 1 and 3. In this case however the bottom stream (95) which comprises CO2 fat absorbent is conducted to an intermediate EO converter unit (13) . As in Figure 3 the lean carbonate is cooled by CO2 absorber gas feed in heat exchanger (90) for optimal CO2 absorption. However this means that fat absorbent exiting absorber (9) is at optimum absorption temperature but may not be at a temperature sufficient for EO conversion to glycol. In this case, and in a particularly advantageous manner, which is compatible with the process as a whole, the fat absorbent may be heated (120) on entry to the converter (13) and is held for a required residence time. The fat absorbent then exits the converter (13) and is subsequently flashed (10) for light ends removal (100). CO2 is stripped (11) from the absorbent as in the conventional process. Steam including entrained glycol exits from the overhead of the stripper (11) with the CO2 (111) and is conducted to a knockout drum (112), from which CO2 exits as the overhead stream and as in the conventional process is vented (12) , or if desired, recovered for use or sale as a by-product, and condensed water containing glycol exits from the bottom (113). The condensate stream is in its entirety or in part sent as a bleed stream for treatment. Figure 4 illustrates a preferred modification by which water (94) condensed from the CO2 absorber overhead gas knockout (92) is combined with fat carbonate exiting the bottom of absorber (9) which in a particular advantage additionally allows treatment of any EO present in the overhead condensate (92). Figure 4 illustrates one way, specifically heat exchange in exchanger (120) with CO2 stripper overhead (111) , in which the conventional process is modified for heat exchange to heat the fat absorbent. In fact the process may be modified for heat exchange in any suitable manner to heat the fat absorbent, and alternative modifications are illustrated in Figure 5. For example hot lean carbonate (110) may be used to heat fat carbonate. Alternative means make use of an independent heat source in combination with outlet / inlet fat absorbent heat exchange as hereinbefore defined. For example steam as an independent heat source may be used to heat CO2 fat absorbent stream (95) directly. Figure 5 also illustrates an alternative means whereby CO2 absorber overhead gas knockout condensate (94) may be treated to remove alkylene oxide independently, by heating with steam to a very high temperature in excess of 130°C up to 210°C at which EO reacts away immediately whereby purified condensate (940) can then be used directly in flasher (10), as in the conventional process. Preferably the process of the invention is used in an EO process for producing EO as a commercial product, for example selected from sterilisation agents, fumigants, and the like or may be used as a starting material in the manufacture of glycols and the like for the preparation of a diversity of products such as antifreeze, cosmetics, lubricants, plastics and surfactants. In a further aspect of the invention there is provided an apparatus for remediation of fluid as hereinbefore defined contaminated with up to 1000 ppmv of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber. Suitably the volume V of the holding unit is determined having regard to the flow rate of the fat absorbent, and other factors as relevant, to confer suitable residence time for conversion of alkylene oxide as hereinbefore defined. Preferably the apparatus is suitable for use in the process for converting alkylene oxide comprised in a fluid as hereinbefore defined. In the case that the apparatus is suitable for remediating more than one fluid, preferably fluids are combined upstream of the inlet or additional inlet means are provided upstream of the holding unit or at the upstream end thereof. Preferably the apparatus comprises means for mixing additional fluid streams, more preferably to provide substantially uniform fat absorbent composition, for example comprises a mixing pump at the combined inlet or additional inlets. Preferably the volume V of the holding unit is in the range of from 50 to 350 m3, and more preferably 100 m3 to 300 m3, and is selected having regard to the required volume of fat absorbent to provide the desired residence time distribution as hereinbefore defined. For the purpose of illustration, volumes are related to world scale plants as built in year 2000 with EOE (EO equivalent) capacities of 300 to 400 kT/a. Accordingly it is within the competence of the skilled person to determine a suitable volume for apparatus in other units or in units at different volumes. The holding unit is shaped and configured and/or provides internals whereby fluid flow through the apparatus approaches plug flow, whereby residence time distribution of the fat absorbent is substantially uniform. By this means a desired conversion can be attained at a lower holding unit volume than would otherwise be possible. Preferably therefore the holding unit comprises one or more elongate conduit means ensuring minimal back mixing and flow divergence. Conduit means has length 1 and diameter d providing a length to diameter ratio 1/d which may be greater than or equal to 10, preferably greater than or equal to 25, more preferably in the range of from 30 to 600, more preferably in the range 40 to 500 most preferably in the range 50 to 37 5, or 50 to 150. Accordingly diameter may be in the range 0.5m to 2m, preferably 0.7 5m to 1.90m, more preferably approximately 0.8m; and length may be in the range 10m to 600m, preferably 20m to 500m, more preferably approximately 300m or 400m. A plurality of conduits may be provided in parallel or in series thereby providing a compact holding unit and dispensing with thermal insulation and like considerations. Preferably one or more conduit means comprise one or more elongate pipes. Internals which may be provided in the holding unit as hereinbefore defined are suitably selected from baffles, structured or unstructured packing and other internals known to provide flow approaching plug flow and substantially uniform residence time distribution. Preferably packing, if present, has a high void fraction to avoid increasing the size of the holding unit whilst still providing the desired volume V, more preferably packing comprises a packed bed. A packed bed may have dimensions given as length / diameter greater than 2, for example having length in the range 10m to 50m and diameter in the range 3m to 6m. A plurality of conduit means may be provided for example as a horizontal or vertical aligned cluster of parallel aligned conduit means adapted for distribution of the fat absorbent stream uniformly across all conduits at the inlet means and adapted for the convergence of fat absorbent at the outlet means. Distribution means may comprise guide vanes or the like or may comprise fluting portions of each conduit having an initial diameter equal to the diameter of the inlet means divided by the number of conduits and having a final diameter equal to the conduit diameter, the fluting portion being straight or curved in manner to provide fluid association of the converter inlet with the conduit in question. Alternatively the holding unit may comprise one or more conduits configured in a plane as a circular or square spiral or as alternate linear and 180° bend sections in the form of a repeated folding configuration or the like. A holding unit comprising a plurality of planar configured conduits as defined is conveniently provided as a horizontal or vertical stack of planar conduits. The holding unit may have distribution and convergence means as hereinbefore defined, in the case that the holding. unit comprises combined conduit diameter in excess of inlet diameter, or may simply comprise packing or stream dividers to reduce turbulence, in the case that the combined conduit diameter is substantially equal to the inlet diameter. Preferably the holding unit is characterised by Peclet number, Pe, in excess of 10. Suitable Pe is the range of from 10 to 10,000, for example 100 to 2500, preferably 150 to 450, although other Pe values may be envisaged which provide for conversion of alkylene oxide, but at lower efficiencies of operation, and therefore not benefiting from synergies which are of particular advantage in the present invention. Peclet number is defined, for a conduit type holding unit, as Pe = x L/DL, where is the average fluid velocity, L the length of the tube and DL is the longitudinal (or axial) dispersion coefficient. The latter can be calculated by one of the correlations known in the art. For a packed bed Pe can be calculated using the well known so-called Bodenstein Bo=2 relation, where Pe=Bo x L/dp (dp being the particle diameter). In a preferred embodiment of the invention the apparatus comprises heating means associated with the inlet means of the holding unit, selected from heating means as known in the art. Preferably heating means comprises a heat exchanger providing heat exchange between fat absorbent and another process stream at higher temperature as hereinbefore defined such as steam, lean absorbent, stripper overhead and the like, or a combination thereof, more preferably by heat exchange selected from: a fat/lean exchanger interchanging heat between hot aqueous lean absorbent from which fluid has been desorbed and fat absorbent with absorbed fluid which requires heating; a fat absorbent / fluid exchanger interchanging heat between hot desorbed fluid and fat absorbent with absorbed fluid which requires heating. Alternatively or additionally heating is by using an independent source such as: steam from another process stage, in particular steam for venting (waste steam) or cooling to water (process steam); or very hot condensate such as from the EO stripper bottom (lean absorbent)'; or other in-process heat sources such as EO stripper overhead and the like; and combinations thereof. Preferably heat exchange comprises a line-up of suitable available heat sources and cooling sources. Preferably the total heat exchange time is adapted for the heat exchange area and exchange volumes, and is for example 1 to 6 minutes, with a heat exchange area of for example 750n\2. Preferably the unit comprises a heat exchanger section wherein the fat absorbent stream is brought into thermal communication with the stripper overhead comprising hot C02, thereby heating the fat absorbent at the upstream end of the holding unit and cooling the stripper overhead CO2 before venting or forwarding for other applications. A heat exchanger may be of any type as known in the art and is suitably of the shell and tube type or plate and frame type and is suitably provided at the upstream end or as part of the inlet means of the holding unit. Fat absorbent temperature may be regulated by heat exchanger factors such as selecting heat transfer area, and materials of heat exchanger (heat exchange coefficient) also selecting the temperature of the heat donating stream and the flow rates of respective streams. The apparatus of the invention may be part of any apparatus in which a fluid stream is produced having an amount of contaminating ethylene oxide. Preferably the apparatus is part of an EO unit for the conversion of ethylene to EO, more preferably part of an EO/EG unit, as hereinbefore defined. It is a particular advantage that an EO unit may be minimally modified by the apparatus of the invention. Preferably the unit is modified by incorporating the apparatus in the feed stream to CO2 vent, to confer increased residence time optionally additionally including a heat exchanger, for example by diverting a stream conduit such as the CO2 stripper overhead conduit for heat exchange with the fat absorbent. Additionally the unit may include means for mixing additional contaminated fluid streams. In a further aspect of the invention there is provided an EO unit for the conversion of ethylene to ethylene oxide with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle and is remediated using the apparatus as hereinbefore defined. The invention is now illustrated in non limiting manner with reference to the following examples. Examples Comparative Example - Conventional Process without treatment of SO in the feed stream for CO2 removal The process of the operation as shown in Figures 1 and 3 makes use of a multitubular fixed bed reactor to produce ethylene oxide, and comprises contacting gaseous ethylene and oxygen with a silver on alumina catalyst (CRI EO catalyst S382) at a temperature in the range of 200 to 300°C, and at a pressure in the range of 12 to 22 bar a . Unconverted oxygen and ethylene are recycled back into the reactor via the recycle stream. Reaction products (ethylene oxide and water) are removed in the EO recovery and removal section and fresh feeds are supplied. A small bleed stream is withdrawn from the recycle gas and vented. The process results in gas leaving the EO reactor which carries an undesirable by-product CO2, which has to be removed to avoid excessive build up that may impede EO production. A CO2 removal section therefore provides for an amount of CO2 to be removed from the recycle and vented. A feed stream to the CO2 removal section, is contacted with an aqueous carbonate absorbent solution which selectively absorbs CO2 from the recycle stream and which contains potassium carbonate, potassium bicarbonate with potassium vanadate and potassium borate as activators. The fat absorbent is then flashed and stripped to remove volatiles and yield CO2 which is suitable for venting. The feed stream for CO2 removal can contain EO of the order of up to 500 ppm volume or even higher if not treated properly. In this example the EO concentration in this stream is 32 ppmv. Conditions and results are shown in Table 1. Example 1 - Process of the Invention with increased residence time In the process of the invention the CO2 removal unit is modified by incorporating an EO Converter of the invention comprising a reactor with substantially plug flow characteristics and a volume of 255 m^, as shown in Figures 2 and 4, resulting in an additional residence time of about 23.75 minutes. The plug flow reactor is provided as a 0.8m diameter pipe of length 300m, and has a sufficient high maximum allowable operating pressure of about 2200kpa. In operating the apparatus an additional volume of the activated carbonate solution, as lean absorbent solution, of an amount of 225m3 is incorporated. The fat absorbent has a pH of from 10.2 to 10.5. In this example the condensed water from the CO2 absorber overhead gas knockout is added to the fat absorbent as shown in Figure 4. In the EO Converter the absorbed EO is converted to glycol and is removed from the CO2 removal unit with the condensed water from the CO2 absorber overhead (113) and is sent to waste water with the existing stream, as shown in Figures 4 and 5. Operation of the process and the apparatus of the invention guarantees sufficient conversion of absorbed EO in the CO2 removal unit to reach less than about O.OOlkg/hr EO in the CO2 vent. Conditions and results of Example 1 are shown in Table 1. Example 2 - Process of the Invention with increased residence time and heating of fat carbonate Operating the CO2 removal unit under the conditions as describee in Example 1 results in unfavorable CO2 absorption conditions. To reach high absorption efficiency the temperature in the CO2 absorber has to be lowered to a level as mentioned in the first column of Table 1 . That however would result in much lower EO conversions in the EO converter: with the apparatus of above Example 1 and under the same flow and same residence times, that would result in an amount of EO in the CO2 vent in excess of 0-.1 kg/h. In order to reach the required conversion in the CO2 removal unit the temperature of the fat carbonate has to be increased. This is preferably done in a way that is energy neutral to the process. Amongst others, two options are available: (1) a fat/lean heat exchanger interchanging heat between fat and lean carbonate or (2) a fat carbonate/CC>2 heat exchanger interchanging heat between CO2 stripper overhead and the fat carbonate. Other methods can use (waste) steam heat or very hot condensate as independent heat source with or without outlet / inlet heat integration. In this Example again the condensed water from the CO2 absorber overhead gas is added to the fat absorbent as shown in Figure 4. The surface area for a fat carbonate / CO2 heat exchanger was 750m2. With this heat exchanger the fat carbonate temperature was increased to 92(91)°C without substantially changing conditions elsewhere in the process. The fat carbonate has a residence time in the piping and carbonate flasher of about 10 minutes as well as up to about 1 or 2 minutes in the new fat carbonate / CO2 heat exchanger. In order to achieve the required EO conversion, additional residence time was provided in the new EO Converter, as described in Example 1. The conversion of absorbed EO in the CO2 removal unit was found to give less than about 0.001 kg/hr EO in the CO2 vent, as in Example 1. This is despite lowering the temperature in the CO2 absorber. The result, with a combination cf increased temperature and residence time, gives both excellent CC7 absorption and excellent EO conversion. Conditions and results of Example 2 are shown in Table 1. Table 1 - EO in vent gas under several different process conditions (Table removed) Figure 6 illustrates typical residual EO against residence time for conversion at a range of temperatures. Example 3 - Apparatus of the Invention - Design of EO Converter (Holding Unit) The design of an EO Converter was optimised to develop different configurations suitable for different reactors and operating conditions. The results are shown in Table 2. Table 2 - EO Converter configurations according to the invention with equivalent EO conversion of 99.92% for all cases. (Table removed) Alternative holding unit dimensions having Pe less than 450 include Pe = 419 or 208, a diameter of 0.8m or 1.0m and length is 300m or 400m. A single pipe is engineered into a "vessel" reactor by folding the pipe. The "vessel" reactor is illustrated in Figure 7. The depth of the channels are equal to the width and do not exceed 2 meters. Several of the slices as drawn in the Figure are stacked on top of each other with thv outlet of each slice connected to the inlet of the following one, such that all channels are connected in series. There is no preference for the channels running in horizontal or vertical direction. A variant "vessel" reactor is a cylindrical vessel packed with cylindrical pipes which are connected in series by 180° bends in similar manner to Figure 7. CLAIMS 1. Process for remediation of a fluid contaminated with up to 1000 ppmv of alkylene oxide, comprising contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed, fluid, conferring intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide, wherein the fat absorbent has a pH in the range of- from 7 to 11. 2. Process as claimed in claim 1, wherein the fluid comprises a CO2 containing stream contaminated with ethylene oxide (EO). Process as claimed in claim 1 or claim 2, .wherein absorbent is selected from alkaline metal carbonates, preferably sodium (bi) carbonate and potassium (bi) carbonate; water; methyl alcohol; acetone; and solvents such as propylene carbonates or ethylene carbonates; and mixtures thereof with another absorbent or an activator, preferably selected from potassium and sodum vanadate, chromate, borate and mixtures thereof. Process as claimed in any one of claims 1 to 3, which provides residence time of absorbent and alkylene oxide expressed as total residence time of greater than or equal to 11 minutes, for example up to 60 or 120 minutes; or expressed as additional residence time of greater than or equal to 4 minutes, for example up to 53 or 113 minutes. Process as claimed in any one of claims 1 to 4, wherein fat absorbent temperature is in the range of from 80°C to 140°C. Process for remediation of a fluid as claimed in any one of claims 1 to 5, contaminated with up to 1000 ppmv of alkylene oxide comprising contacting the fluid with an aqueous absorbent at an absorption efficiency in the range 50-99.9%, preferably 75-99.9%, most preferably 90-99.9%, to yield a fat absorbent having absorbed fluid, if required heating the fat absorbent, and maintaining for a desired residence time for conversion of alkylene oxide, wherein the process includes subsequently desorbing absorbed fluid, cooling the lean absorbent to a temperature for the required absorption efficiency and recycling to the absorption stage. Process as claimed in claim 6,. wherein heating is by heat exchange with a further process stream or a combination thereof. Process as hereinbefore defined in any one of claims 1 to 7, which is part of a process for the conversion of ethylene to ethylene oxide with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle in the CO2 removal section and is remediated by the process as defined in any one of claims 1 to 7. 9. Process as. claimed in claim 8, which is modified by increasing the volume of lean absorbent in the CO2 removal section to confer increased residence time; and optionally additionally by heating the fat absorbent .in the CO2 removal section. 10. Apparatus for remediation of fluid as hereinbefore defined in any one of claims 1 to 9, contaminated with up to 1000 ppmv of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for The fat absorbent, and outlet means connected to the inlet of a fluid desorber, wherein the holding unit is shaped and configured and/or provides internals whereby fluid flow through the apparatus approaches plug flow. Apparatus as claimed in claim, wherein the holding unit is selected from one or more conduit means for example one or more elongate pipes, optionally including internals selected from baffles, structured or unstructured packing and other internals known to provide flow approaching plug flow and substantially uniform residence time distribution. Apparatus as claimed in claim 10 or claim 11, wherein the holding unit is characterized by peclet number, pe, in excess of 10, preferably in the range 10- 10,000, more preferably 100-2500. Apparatus as claimed in any one of claims 10 to 12, which comprises heating means associated with the inlet means of the holding unit, preferably comprising a heat exchanger providing heat exchange between fat absorbent and another process stream at higher temperature or combination thereof Apparatus as claimed in any one of claims 10 to 13, which is part of an E0 unit for the conversion of ethylene to ethylene oxide, more preferably part of an E0/EG unit, in which the apparatus is position in the C02 vent stream.

Full Text

REMEDIATION PROCESS AND APPARATUS
The present invention relates to a process for remediating a fluid containing minor amounts of ethylene oxide, apparatus therefor and the use thereof, in particular in remediating a CO2 vent stream from an
ethylene oxide (EO) process. Background of the Invention
Ethylene oxide is a substantial item of chemical commerce having utility both as a sterilisation agent and as a fumigant, but primarily as a starting material in the manufacture of a diversity of products such as antifreeze, cosmetics, lubricants, plastics and surfactants. The major process for manufacture of ethylene oxide is by the silver-catalysed oxidation of ethylene. Typically, the stream exiting the reactor comprises small quantities of ethylene oxide (for example 0.5 to 5 mol%) together with large amounts of residual gases including unconverted ethylene and oxygen as well as appreciable quantities of carbon dioxide, low molecular weight hydrocarbons 'and inert gases such as nitrogen. Customarily, the ethylene oxide product is recovered from the residual gases by absorption in water followed by processing of the ethylene oxide-fat absorbent in a variety of ways including fractionation, scrubbing, stripping and the like.
An ethylene oxide plant may also be the site of production of monoethylene glycol derived by hydration of the product ethylene oxide. In such a plant, commonly the product ethylene oxide having been isolated by water absorption is then hydrated in a separate reactor.
Variations of this process have been proposed in the past. GB-A-4 98,119 for example is an early proposal where the hydration may be effected thermally or, preferably, using an acidic catalyst which is added to the water absorbent. The glycol forms on heating the absorbent solution after the ethylene oxide is absorbed and the resulting solution is recycled as liquid absorbent until the glycol content is relatively high and is recovered.
EP-A2-776890 proposes another variant where ethylene oxide absorbed in a solution containing ethylene carbonate and ethylene glycol is reacted with carbon dioxide to the carbonate form and hydrolysed with a separate catalyst. The Example shows that treatment of an ethylene oxidation product stream containing 3 mol% ethylene oxide left 100 ppm in the residual gases, following the particular absorption step and conditions used.
DE-A1-19843721 uses ethylene oxide wash water as absorbent prior to the hydration step. The Example shows absorption in wash water of ethylene oxide from a gas mixture containing 2.7 mol% ethylene oxide, leaving 10 ppm ethylene oxide to be lost in the residual gases.
The residual gases that remain after recovery of the bulk ethylene oxide product, are recycled to the ethylene oxidation reactor. Customarily, a small bleed stream is withdrawn from the recycled gases to prevent build-up of impurities such as argon, ethane or nitrogen in the recycle gas loop. A side stream, being part or all of the recycle gas, is usually scrubbed with an aqueous CO2
absorbent for removal of excess CO2 which is subsequently
stripped from the absorbent and typically is vented, or if desired, recovered for use or sale as a by-product.
A problem arises particularly in manufacturing plants of large capacity in that during scrubbing of the recycle gas side stream small amounts of hydrocarbon are dissolved and/or entrained in the CO2 absorbent and ultimately vented with the carbon dioxide.
US 3,867,113 discloses a process improvement which is now conventional in EO processes, wnereby the CO2~fat
absorbent obtained by contacting a sidestream from the recycle stream with a CO2 absorbent, is flashed to form a hydrocarbon - containing vapour stream and a hydrocarbon - lean fat absorbent, and the fat absorbent stripped to produce a CO2 stream substantially free of hydrocarbon
which is suitable for venting, or use.
Nevertheless, in conventional EO plants, despite flashing the fat absorbate, a small amount of residual EO remains in the vent gas from the CO2 stripper. In order to keep vented EO as small as possible for environmental reasons, the vent gas can therefore conventionally be subject to incineration. Such incineration can for example occur within a catalytic incinerator whereby one or more catalyst beds are heated to.high temperatures (in ranges from approx 300CC to 800°C) and various heat exchange mechanisms are incorporated to minimise energy loss and improve efficiency. This therefore presents a convenient solution which is effective in operation and, as an "end-of-pipe" process, requires minimal alteration to the existing process line up.
Being operated at high temperatures and requiring the need for catalyst will however inevitably mean periods of time in which the incinerator cannot function
through the need for maintenance, repair, replacement of catalyst, etc. Where environmental contamination is measured on an average basis, say as EO vented per week, such incinerator-downtimes are negligible, but increasingly environmental concerns require constant monitoring of EO venting with hourly measurement of contamination, and this means that the conventional incinerator system may not comply with environmental regulations all of the time.
There is therefore a need to provide for an effective reduction of EO in CO2 vent gas from an EO
plant, with or without the use of additional incineration, in which reduction is constantly maintained.
The concentration of EO in vent gas is moreover dependent on a number of factors including the percent of recycle stream which is treated as a sidestream, and the operating conditions of the CO2 absorber and EO- absorber. A further need is therefore to provide a system for independent control of EO in CO2 vent gas from an EO
plant, whereby the level of carbon dioxide to be vented can be varied without compromising the reduction in EO emission. Summary of the Invention
We have now surprisingly found that chemicals present during CO2 absorption in the carbonate section
may also be highly effective in catalysing the reaction of EO to glycol, under certain specific conditions. Even more surprisingly we have found that these specific conditions may be conveniently provided without major alteration of an existing EO plant, or without major design changes in a new plant, and this is of course of
major importance as significant changes would affect other control and emission measures.
While the combination of absorption of olefins and hydration to glycol is utilised extensively, eg in the combined production of ethylene oxide and monoethylene glycol as noted above, use of absorption and hydration has never previously been proposed to remove, for example, the very low levels of ethylene oxide that occurs as a contaminant in CO2~rich vent gas. Moreover,
the removal can be continuously and effectively achieved in preferred embodiments without the addition of any other additive than the aqueous absorbent conventionally utilised in a commercial EO process for CO2 absorption. This is the more surprising since the contaminant levels of EO remain following an extensive absorption process in the conventional production of EO and it would normally be expected that a different or more rigorous teatment, such as the incineration of previous proposals, would be necessary to remove the low levels remaining.
Against the conventional proposal of incineration, the process of the invention allows the removal of ethylene oxide from CO2 vent gas more cheaply, more reliably, and on a continuous basis to meet current day permit control requirements.
Contamination of gas streams by alkylene oxides may also occur in ether commercial operations. However the most preferred application of the process, control system and apparatus of the present invention is the reduction of EO in CO2- vent gas, and throughout the specification the present invention will most frequently be described with reference to this use.
In the broadest aspect of the invention there is therefore provided a process for remediation of a fluid contaminated with up to 1000 ppmv of alkylene oxide, comprising contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, to confer intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide, wherein the fat absorbent has a pH in the range of from 7 to 11.
In a further aspect of the invention there is provided a method for calculating a required residence time of fat absorbent in a process for remediation of fluid as herein defined, from the moment of fluid absorption to the moment of fluid stripping to generate lean absorbent, in manner to convert a desired amount of ethylene oxide as herein defined.
In a further aspect of the invention there is provided an apparatus for remediation of fluid as herein defined contaminated with an amount of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit
having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber, wherein the holding unit is shaped and configured and/or provides internals whereby fluid flow through the apparatus approaches plug flow. Detailed Description of the Invention
The process of the invention comprises contacting the contaminated fluid with an aqueous absorbent to yield a fat absorbent having absorbed fluid, conferring intimate contact of fat absorbent and alkylene oxide and conversion of alkylene oxide. Absorption may be
of all or part of the contaminated fluid which is contacted with absorbent, and is typically of part of the contaminated fluid.
Preferably alkylene oxide is converted to glycol in the process of the invention. In a particular advantage
glycol can be separated in subsequent stages as a liquid condensate, yielding remediated fluid.
Reference herein to a fluid is to a fluid stream, reservoir or the like and is preferably a fluid stream. Fluid may be of gas or liquid form, such as a gas, vapour or condensed vapour, or other liquid. Preferably the fluid comprises a gas stream, comprising an amount of alkylene oxide. Alternatively or additionally the fluid may comprise condensed vapour, such as condensed steam, comprising an amount of alkylene oxide. Preferably the fluid comprises a CO2 containing stream, especially a
C02~rich stream, contaminated with ethylene oxide (EO), more preferably from the partial oxidation of ethylene to ethylene oxide by the EO process in an EO unit in which the CO2 is intended for venting. A C02~rich stream suitably contains up to 10 mol%, for example in the range of from 0.1 to 6 mol%, preferably 0.5 to 6 mol%. Suitable examples are from 3 to 6 mol% CO2, but also 0.5 to 3 mol%.
In a particular advantage the contaminated fluid is absorbed as hereinbefore defined and provides a suitable medium for combining contaminated fluid and converting alkylene oxide from other sources. Preferably therefore the process of the invention comprises contacting fluid and absorbent as hereinbefore defined and simultaneously or subsequently additionally combining one or more additional alkylene oxide contaminated fluids for conversion of alkylene oxide as hereinbefore defined. Such additional streams may for example include condensed steam which has been used for scrubbing or the like, such as absorber overhead gas knockout, absorbent which has
been used to absorb alkylene oxide from other streams and the like.
Combining fluids is preferably carried out with mixing, more preferably to provide a uniform fat absorbent composition.
The process is suitable for converting alkylene oxide present in any amount up to 1000 ppmv, for example in the range of from 0.1 ppmv up to. 1000 ppmv, preferably 0.1 ppmv to 500 ppmv. It is of particular significance that the process is able to convert residual amounts of ethylene oxide of, or in excess of, 0.1 ppmv up to 40 ppmv.
The process may be operated at any desired conversion. Conditions may be chosen to give a desired conversion depending on the level of alkylene oxide present.
It is a particular advantage that the process is characterised by a very high conversion whereby the absorbed fluid may be substantially completely remediated by the process of the invention, preferably the process is characterised by conversion substantially greater than or equal to 50%, more preferably substantially greater than or equal to 80%, for example from 88% to substantially complete conversion, preferably from 90% to 99.9999%, more preferably from 95% to 99.999%. This enables reduction of alkylene oxide to below 1 ppmv and especially to below 0.1 ppmv.
Suitably the process comprises in a further stage desorbing the absorbed fluid, thereby generating a lean absorbent stream, separating the alkylene oxide conversion product and recycling the lean absorbent. Preferably the process comprises separating any volatile hydrocarbons by flashing the fat absorbent, prior to
desorbing the absorbed fluid by stripping. Preferably the absorbed fluid is a gas and the process comprises separating the alkylene oxide conversion product by phase separation for example condensation or knockout to form condensed liquids and a remediated fluid which is substantially free of alkylene oxide, preferably having a maximum residual alkylene oxide level of 1 ppmv or less, more preferably of 0.1 ppmv or especially less than 0.1 ppmv.
Aqueous absorbent may be selected from any aqueous solution which is not deleterious to catalysts or other components if any, present in other stages of the process. Preferably the absorbent is selected from alkali metal carbonates such as sodium (bi) carbonate, potassium (bi) carbonate; water; methyl alcohol; acetone; and solvents such as propylene carbonates or ethylene carbonates; and the like; and mixtures thereof with other absorbents or fillers. More preferably the absorbent is a CO2 absorbent. The absorbent is especially an alkali metal carbonate. In a typical absorption system the lean absorbent solution may contain for example K2CO3 and KHCO3 in a ratio of about "70:30. When CO2 - containing gas is passed through the absorber, reaction of CO2 with
the carbonate solution results in conversion of up to about 90% K2CO3, leaving about 10% KHCO3. The absorbent
may contain activators and the like for improved absorption. Known and preferred activators include potassium or sodium salts of metal oxides such as vanadate, chrornate and borate and mixtures thereof. Preferably the absorbent is selected from commercially available CO? absorbents such as Catacarb or Benfield solutions. Benfield absorbents are disclosed for example
in GB 1415036, US 3863003, US 3907969, the contents of which are incorporated herein by reference.
The process is suitably carried out under conditions conducive to conversion of alkylene oxide. Conditions conducive to conversion of alkylene oxide include conditions selected from low or high pH, presence of activators, elevated temperature, extended residence time, and the like.
alkaline and have a the fat absorbent is neutral to alkaline having a pH in the range of from 1 to 11, most preferably 9 to 11, and especially 10 to 11.
The fat absorbent may be activated by the presence of an amount of activator selected from substances which promote or catalyse the conversion of alkylene oxide. Activator is preferably derived from an available process component, but may be added to the absorbent or the fluid. It is possible that CO2 present in a fluid to be remediated, for example, may promote conversion of alkylene oxide by virtue of its acidity in solution or by virtue of an activating effect.
We have observed the conversion of ethylene oxide to glycol to take place with high conversion by a modification downstream of the CO2 absorption stage in the EO process, in which CO2, absorbent, activators and water are present as fat absorbent, the modification comprising intentionally increasing fat absorbent residence time beyond that required for conventional absorption and separation. Without being limited to this theory it is thought that the conversion of alkylene
oxide to glycol may be facilitated by one or a number of conditions selected from the presence of activators, alkali, and/or other catalyst and water both for activation and being consumed in the conversion, and conditions such as elevated temperature, extended residence time and the like. The rate of conversion depends on conditions of temperature, presence of activators and the like, and this in turn determines the required residence time for conversion.
The period for intimate contact of absorbent and alkylene oxide is conveniently expressed as the residence time of the fat absorbent, being the time between absorption and desorption stages. The required residence time for conversion of alkylene oxide depends on a number of factors including amount and concentration of alkylene oxide and activator prevailing temperature and pressure and the like.
Typically residence time in prior practice conventional EO units is up to 3 minutes in the C02 absorber, 1 minute in piping and a further 3 minutes in
the flasher.
Preferably the absolute residence time in the
process of the invention is greater than or equal to 11
minutes, more preferably greater than or equal to 15
minutes, more preferably is in excess of 18 minutes, for
example up to 60 or 120 minutes. Most preferably
residence time is in the range 18 to 67 minutes, such as
20 to 50 minutes. The residence time varies according to
the process or operation from which the contaminated
fluid is derived. It is therefore convenient in some
cases in which the application of this invention is a
retrofit, to express residence time as additional
residence time representing the increase over prior
practice. For example in an absorption stage of a conventional process, additional residence time represents the increase over the minimum residence time required to absorb and desorb fluid, including conducting fat absorbent to a flasher, flashing hydrocarbons and conducting the flashed absorbent to a desorber to desorb fluid. Expressed in this way preferably the process of the invention provides an additional residence time of greater than or equal to 4 minutes, more preferably greater than or equal to 8 minutes, more preferably in excess of 11 minutes, for example up to 53 or 113 minutes. Most preferably additional residence time is in the range 11 to 60 minutes, such as 13 to 43 minutes.
Preferably the process of the invention is part of a continuous process whereby residence time is conveniently expressed as total fat absorbent volume divided by total fat absorbent flow rate, and a desired residence time is provided by selecting volume or rate accordingly. Preferably the fat absorbent is characterised by substantially uniform flow rate, more preferably substantially plug flow, thereby conferring narrow residence time distribution. By this means a desired conversion can be attained at a lower lean absorbent volume or shorter residence time than would otherwise be possible.
The temperature of the fat absorbent may be any temperature conducive to conversion of alkylene oxide. Suitably fat absorbent temperature is in the range of from 80°C to 140°C, more preferably 90°C to 130°C.
Preferably the fluid containing the contaminant level of alkylene oxide is absorbed from a recycled gas stream or a side stream thereof which is contacted with absorbent as hereinbefore defined, and a desired amount
of fluid is absorbed and separated from the recycle stream or side stream thereof. The amount of fluid absorbed from the recycle or side stream determines the amount of alkylene oxide to be converted and thereby the required conditions such as residence time for fluid remediation. The absorption of fluid is typically both temperature and time dependent and is given as a measure of absorption efficiency. In the EO process a desired volume o'f CO2, containing an amount of C1 and C2
hydrocarbons, is absorbed from the recycle stream at a desired absorber temperature to achieve the required operating protocol in terms of conversion of the ethylene to EO and to ensure a desired catalyst lifetime. At a temperature of from 70°C to 130°C or 140°C the CO2 absorber absorbs in the region of 50% to 99.9% CO2 from the feed stream to the absorber, i.e. operates at a CO2 absorption efficiency of 50% to 99.9%. Preferably the CO2 absorber absorbs approximately 75% to 95% of CO2 from the
feed stream i.e. operates at a CO2 absorption efficiency of 75% to 95% at a temperature in the range 70°C to 110°C
and the remainder is returned to the recycle stream.
We have however found that at this temperature the
conversion of alkylene oxide according to the present
invention is non-optimal, for example is less than 90%.
For treatment of a CO2 vent gas, if the temperature of
CO2 fat absorbent in the absorption stage is elevated to
a temperature in the range of from 80°C to 140 °C, more preferably 90°C to 130°C as hereinbefore defined, then a higher conversion in the range 90% to substantially complete conversion of the contaminant alkylene oxide may be obtained.
There is therefore a conflict in the optimum temperature for absorption of fluid at a desired fluid absorption efficiency, and that for conversion of alkylene oxide at a desired conversion according to the present invention, and it is therefore not appropriate to simply increase the temperature of the fluid absorption, since this reduces the absorption efficiency.
In a preferred embodiment therefore the invention comprises a process for remediation of a fluid'as hereinbefore defined contaminated with up to 1000 ppmv of alkylene oxide comprising contacting the fluid with an aqueous absorbent at an absorption efficiency in the range 50% to 99.9% preferably 75% to 99.9% most preferably 90% to 99.9%, to yield a fat absorbent having absorbed fluid, if required heating the fat absorbent, and maintaining for a desired residence time for conversion of alkylene oxide, wherein the process includes subsequently desorbing absorbed fluid, cooling the lean absorbent to a temperature for the required absorption efficiency and recycling to the absorption stage. Preferably the process is for remediating a C02~rich stream and comprises absorbing at a first
temperature in the range of from 60°C to 110°C, preferably 70°C to 110°C, and heating, if required to a second temperature in the range of from 80°C to 140°C for example 90°C to 130°C for conversion of alkylene oxide, desorbing and cooling to a first temperature as hereinbefore defined.
The fat absorbent may be heated by any desired means and is preferably heated with a heat exchanger or other heat source in a way that is energy neutral to the process as a whole. In a particularly advantageous
embodiment of the invention, fat absorbent is provided as a fluid stream whereby it is conducive to heat exchange. Preferably therefore heating is by heat exchange with a further process stream, such as steam, lean absorbent, stripper overhead and the like or a combination thereof, more preferably by heat exchange selected from:
a fat / lean exchanger interchanging heat between hot aqueous lean absorbent from which fluid has been desorbed and fat absorbent with absorbed fluid which requires heating;
a fat absorbent / fluid exchanger interchanging heat between hot desorbed fluid and fat absorbent with absorbed fluid which requires heating.
Alternatively or additionally heating is by using an independent source such as:
steam from another process stage, in particular steam for venting (waste steam) or cooling to water (process steam); or
very hot condensate such as from the EO stripper bottom (lean absorbent); or
other in-process heat sources such as EO stripper overhead and the like;
and combinations thereof.
Preferably heat exchange comprises a line-up of suitable available heat sources and cooling sources. Preferably the total heat exchange time is adapted for the heat exchange area and exchange volumes, and is for example 1 to 6 minutes.
Preferably however heat exchange is with a fat absorbent/fluid heat exchanger such as a fat absorbent / CO2 heat exchanger.
The temperature of fat absorbent leaving the heat exchanger is regulated by altering heat input to the exchanger by known means such as adjusting the flow rate of the interchange stream, such as the lean absorbent or desorbed fluid, or adjusting heat input to the interchange stream source, such as the fluid stripper or the like. Temperature regulation may be manual or automatic, for example the process may comprise a control mechanism which alters heat input to the fat absorbent in response to detecting a change in amount of alkylene oxide in t.he, fluid, or change in volume or flow rate of absorbed fluid.
The fat absorbent stream containing absorbent, fluid, alkylene oxide conversion product and any unconverted alkylene oxide typically also contains an amount of volatile hydrocarbons such as methane, ethylene and ethane. In a preferred embodiment the process of the invention includes flashing the fat absorbent at reduced pressure) to remove volatiles before forwarding the fat absorbent to the CO2 stripper for contact with stripping medium. Volatiles removal may' be facilitated by adding a flashing agent and/or adding a stripping agent as known in the art. Stripping medium is selected from any suitable stripping gases such as methane, ethane, nitrogen, steam, air, O2, CO2 and the like.
In the case that the process of the invention is part of a process for ethylene oxide/ethylene glycol (EO/EG) production, the condensate from the stripping of the fat absorbent stream, which comprises ethylene oxide conversion product glycol, may be sent directly for glycol recovery, or combined with the condensate from the EG production and forwarded for dewatering and glycol
recovery or any other treatment in a combined or separate stage, or alternatively may be sent to waste.
Preferably the heat of the stripped fluid stream is removed before venting the fluid or forwarding for further use. Heat removal is typically by heat exchange with the fat absorbent stream as hereinbefore defined, followed by aftercooling with different means, as conventional (chiller, cooler and the like).
Accordingly the process preferably comprises regulating the flow of lean absorbent contacting the contaminated fluid, and regulating the residence time of fat absorbent, for example by addition.of inert gases and like techniques as known in the art for reduced flow rate and increased residence time, and/or comprises regulating the temperature of fat or aqueous absorbent by heat exchange or other means as hereinbefore defined.
In a further aspect of the invention there is provided a method for calculating a required residence time of fat absorbent in a process for remediation of fluid as hereinbefore defined, from the moment of fluid absorption to the moment of fluid stripping to generate lean absorbent, in manner to convert a desired amount of ethylene oxide as hereinbefore defined. Preferably the method comprises compiling a set of kinetic data for the process in question relating to reduction in residual ethylene oxide with increasing residence time at a number of temperatures, compiling a relation as in Figure 5 and determining an appropriate temperature and/or time for operation for a particular ethylene oxide concentration in fluid to be remediated.
The process of the invention has highlighted concerns over incidental release of EO in vent gas. In a further embodiment the process of the invention comprises
an additional end-of-pipe incineration of the fluid stream after conversion of alkylene oxide as hereinbefore defined. End-of-pipe incineration which is the current practice for remediating a CO2 vent stream and is effective for combusting any levels of EO or other hydrocarbons, is not suited for full time operation, for the reasons described above. Preferably therefore the process provides for additional permanent, temporary or semi permanent end-of-pipe incineration. This is useful in the event of accidental release of high levels of ethylene oxide to the fluid stream for example in the case of process malfunction. It is also useful in the event of incidental increase of alkylene oxide levels, for example in processes adopting minimal additional residence time to achieve initial alkylene oxide reduction or alkylene oxide reduction at usual loading levels, and requiring an additional end-of-pipe solution to complete alkylene oxide reduction or in times of higher fluid loading or higher alkylene oxide contamination.
In a further aspect of the invention there is provided a process for the conversion of ethylene to ethylene oxide (EO) with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle and the CO2 gas stream is remediated by the process as
hereinbefore defined. Preferably the process comprises in an additional stage the conversion of product EO to EG. The amount or volume of fluid to be remediated and the concentration of alkylene oxide therein determine the amount or volume of alkylene oxide to be converted. The fluid absorption efficiency, for example CO2 absorption
Inefficiency for absorption from the recycle stream of the EO process, and the concentration of alkylene oxide, for example in the recycle stream, determine the amount of alkylene oxide absorbed with fluid, for example C02 from the recycle stream and thereby the requirements for the process of the invention. However it would be desirable to operate the remediation process of the invention without impacting on the other stages of the process of which it forms a part.
In a particular advantage of the invention we have found that we are able to operate the process of the invention at increasing alkylene oxide levels in the contaminated fluid stream and still obtain a remediated fluid stream having a desired maximum residual alkylene oxide level of 1 ppmv or preferably 0.1 ppmv by selection of operating conditions as hereinbefore defined.
In a preferred embodiment of the invention there is therefore provided a process for remediation of a fluid contaminated with an amount of up to 1000 ppmv alkylene oxide, especially a CO2 vent gas in an EO unit, comprising contacting fluid with aqueous absorbent to form fat absorbent comprising fluid and alkylene oxide in any volume or at any rate, and converting alkylene oxide, wherein the process comprises determining suitable conditions at any time, selected from amount or temperature of aqueous absorbent, residence time or temperature of fat absorbent or the like, to convert a desired amount of alkylene oxide and maintain at a residual alkylene oxide level less than 0.1 ppmv, and without affecting volume or rate of further fluid absorption. Preferably the process comprises selecting an appropriate combination of fat absorbent temperature and

residence time at any given moment, optionally together with incineration.
Preferably the process for the conversion of ethylene of the invention is operated as known in the art in a multitubular fixed bed reactor, and comprises reacting gaseous ethylene and oxygen over a catalyst at a temperature in the range of 200°C to 300°C, and at a pressure in the range of 12 to 25 bara.
The EO/EG process is illustrated as a block scheme in Figure 1. In Figure 1 and in the corresponding process sketch of Figure 3 the conventional C02 removal is illustrated. Ethylene and water are supplied (1) to the multitubular fixed bed reactor (2) where the EO reaction takes place by the silver-catalysed oxidation of ethylene to ethylene oxide. A large gas stream flows through the reactor tubes (2), which contain the catalyst. The heat generated by the chemical reaction is removed by evaporation of coolant at the shell side of the reactor, which is used for the production of steam. The generated steam is used as heat medium in the glycol reaction and recovery sections of the plant, in the case of a combined EO / EG process.
Typically, the stream (3) exiting the reactor comprises small quantities of ethylene oxide together with large amounts of residual gases including unconverted ethylene and oxygen as well as appreciable quantities of carbon dioxide, low molecular weight hydrocarbons and inert gases such as nitrogen. Reaction products (ethylene oxide and water) are removed in the EO recovery section (4). Unconverted oxygen and ethylene are recycled back into the reactor via the recycle stream (5). In the EO recovery section (4), EO is recovered from the gaseous reactor effluent by absorption in water at a
temperature in the range of from 15°C to 30°C (EO lean absorbent) and is processed in a variety of ways including fractionation, scrubbing and stripping at a temperature in the range of from 100°C to 135°C and the like. The diluted aqueous EO solution (EO fat absorbent) is concentrated in the EO stripper (part of 4, not shown) where an EO/water mixture leaves over the top and a lean absorbent from the bottom. After cooling the EO lean absorbent is-returned to the EO- absorber.
A slipstream of the lean absorbent (not shown) is sent to the glycols recovery section for recovery of glycols that are formed by hydration of a small fraction of the absorbed EO.
Product EO is removed as high purity EO or sent as feed to an EG reaction unit for reaction to form ethylene glycol (EG).
A small bleed stream (6) is withdrawn from the recycled gases (5) to prevent build up of impurities such as argon, ethane or nitrogen in the recycle gas loop. The bleed stream can be used as fuel gas, and preferably all or part of the bleed stream is forwarded for ethylene recovery.
A side stream (7), part or all of the recycle gas, is sent to the CO2 removal section (8) in which it is scrubbed (9) with an aqueous CO2 absorbent for removal of excess CO2 forming a CO2 fat absorbent which is subsequently flashed for light ends removal (10), CO2 is stripped (11) from the absorbent and typically is vented (12), or if desired, recovered for use or sale as a byproduct .
Figure 3 illustrates this process in more detail, showing the side stream (7) conducted via a heat
exchanger (90) in which it is contacted with and cools recycled hot lean carbonate (110). By this means the temperature in the CO2 absorber can be regulated to determine the desired degree of uptake of CO2 - high levels of absorption require cooling of lean absorbent. Residual unabsorbed gases exiting from the absorber overhead (91) are cooled and conducted to gas knockout drum (92) from which the overhead gases (93) are returned to the gas loop, and to the EO reactor (2) and the bottom stream (94) comprising condensed water is combined in the stripper (10) with fat absorbent (95) from the CO2 absorber.
CO2 fat absorbent (95.) exits from the bottom, of absorber (S) and passes to flasher (10) from which volatiles (100) leave as overhead, and liquids including fat absorbent (101) leave at the bottom and enter the stripper (11). Lean absorbent (110) leaves at the bottom. Gaseous CO2 and steam forms the overhead (111), and is conducted to the overhead knockout (112) from which CO2 is vented (12) and condensed water (113) recycled to stripper (11) and/or sent for treatment.
Returning to Figure 1 the recycle stream (5) containing unconverted oxygen and ethylene and other residual gases together with overhead gases from the CO2 removal unit (8) are recycled back to the reactor (2). Fresh feeds are supplied in the recycle stream (1). The oxygen is thoroughly mixed with the hydrocarbon recycle gas stream in a specially designed mixing device having safeguarding mechanisms and oxygen cut off and immediate nitrogen purge for safety. A ballast gas is used to ensure a maximum allowable oxygen concentration in the recycle gas loop.
It is a particular advantage that the EO process may be minimally modified by the process of the invention. Preferably the process is modified by increasing the volume of lean absorbent in the CO2 removal section, to confer increased residence time and optionally additionally heating the fat absorbent in the CO2 removal section, for example by diverting a process stream such as the CO2 stripper overhead for heat exchange with the. fat absorbent. Additionally the process may include a mixing stage for mixing additional contaminated fluid streams.
The increase in volume of lean absorbent which is reguired depends however on plant size and may be determined by those skilled in the art. A typical example for a world class year 2000 plant would require additional lean absorbent volume in the range of from 50 m3 to 350 m3, more preferably 80m3 to 300 m3, for example 100 m3 to 150 m3, depending on the capacity of the EO process, for example 300 - 400 kT/a.
The CO2 removal section in a modified EO/EG process incorporating the process of the invention is illustrated as a block scheme in Figure 2 and as a process sketch in Figure 4.
In this case the side stream (7), part or all of the• recycle gas, is sent to the CO2 removal section (8) in which it is scrubbed (9) with an aqueous CO2 absorbent for removal of excess CO2 as in the conventional process of Figures 1 and 3. In this case however the bottom stream (95) which comprises CO2 fat absorbent is conducted to an intermediate EO converter unit (13) . As in Figure 3 the lean carbonate is cooled by CO2 absorber
gas feed in heat exchanger (90) for optimal CO2
absorption. However this means that fat absorbent exiting absorber (9) is at optimum absorption temperature but may not be at a temperature sufficient for EO conversion to glycol. In this case, and in a particularly advantageous manner, which is compatible with the process as a whole, the fat absorbent may be heated (120) on entry to the converter (13) and is held for a required residence time. The fat absorbent then exits the converter (13) and is subsequently flashed (10) for light ends removal (100). CO2 is stripped (11) from the absorbent as in the conventional process. Steam including entrained glycol exits from the overhead of the stripper (11) with the CO2 (111) and is conducted to a knockout drum (112), from which CO2 exits as the overhead stream and as in the conventional process is vented (12) , or if desired, recovered for use or sale as a by-product, and condensed water containing glycol exits from the bottom (113). The condensate stream is in its entirety or in part sent as a bleed stream for treatment.
Figure 4 illustrates a preferred modification by which water (94) condensed from the CO2 absorber overhead gas knockout (92) is combined with fat carbonate exiting the bottom of absorber (9) which in a particular advantage additionally allows treatment of any EO present in the overhead condensate (92).
Figure 4 illustrates one way, specifically heat exchange in exchanger (120) with CO2 stripper overhead (111) , in which the conventional process is modified for heat exchange to heat the fat absorbent.
In fact the process may be modified for heat exchange in any suitable manner to heat the fat
absorbent, and alternative modifications are illustrated in Figure 5. For example hot lean carbonate (110) may be used to heat fat carbonate. Alternative means make use of an independent heat source in combination with outlet / inlet fat absorbent heat exchange as hereinbefore defined. For example steam as an independent heat source may be used to heat CO2 fat absorbent stream (95)
directly.
Figure 5 also illustrates an alternative means whereby CO2 absorber overhead gas knockout condensate (94) may be treated to remove alkylene oxide independently, by heating with steam to a very high temperature in excess of 130°C up to 210°C at which EO reacts away immediately whereby purified condensate (940) can then be used directly in flasher (10), as in the conventional process.
Preferably the process of the invention is used in an EO process for producing EO as a commercial product, for example selected from sterilisation agents, fumigants, and the like or may be used as a starting material in the manufacture of glycols and the like for the preparation of a diversity of products such as antifreeze, cosmetics, lubricants, plastics and surfactants.
In a further aspect of the invention there is provided an apparatus for remediation of fluid as hereinbefore defined contaminated with up to 1000 ppmv of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for the fat absorbent, and outlet means connected to the inlet of a fluid desorber. Suitably the volume V of the holding unit
is determined having regard to the flow rate of the fat absorbent, and other factors as relevant, to confer suitable residence time for conversion of alkylene oxide as hereinbefore defined.
Preferably the apparatus is suitable for use in the process for converting alkylene oxide comprised in a fluid as hereinbefore defined. In the case that the apparatus is suitable for remediating more than one fluid, preferably fluids are combined upstream of the inlet or additional inlet means are provided upstream of the holding unit or at the upstream end thereof. Preferably the apparatus comprises means for mixing additional fluid streams, more preferably to provide substantially uniform fat absorbent composition, for example comprises a mixing pump at the combined inlet or additional inlets.
Preferably the volume V of the holding unit is in the range of from 50 to 350 m3, and more preferably 100 m3 to 300 m3, and is selected having regard to the required volume of fat absorbent to provide the desired
residence time distribution as hereinbefore defined. For
the purpose of illustration, volumes are related to world
scale plants as built in year 2000 with EOE (EO
equivalent) capacities of 300 to 400 kT/a. Accordingly it
is within the competence of the skilled person to
determine a suitable volume for apparatus in other units
or in units at different volumes.
The holding unit is shaped and configured and/or provides internals
whereby fluid flow through the apparatus approaches plug
flow, whereby residence time distribution of the fat absorbent is substantially uniform. By this means a desired conversion can be attained at a lower holding unit volume than would otherwise be possible.
Preferably therefore the holding unit comprises one or more elongate conduit means ensuring minimal back mixing and flow divergence. Conduit means has length 1 and diameter d providing a length to diameter ratio 1/d which may be greater than or equal to 10, preferably greater than or equal to 25, more preferably in the range of from 30 to 600, more preferably in the range 40 to 500 most preferably in the range 50 to 37 5, or 50 to 150. Accordingly diameter may be in the range 0.5m to 2m, preferably 0.7 5m to 1.90m, more preferably approximately 0.8m; and length may be in the range 10m to 600m, preferably 20m to 500m, more preferably approximately 300m or 400m. A plurality of conduits may be provided in parallel or in series thereby providing a compact holding unit and dispensing with thermal insulation and like considerations. Preferably one or more conduit means comprise one or more elongate pipes.
Internals which may be provided in the holding unit as hereinbefore defined are suitably selected from baffles, structured or unstructured packing and other internals known to provide flow approaching plug flow and substantially uniform residence time distribution.
Preferably packing, if present, has a high void fraction to avoid increasing the size of the holding unit whilst still providing the desired volume V, more preferably packing comprises a packed bed. A packed bed may have dimensions given as length / diameter greater than 2, for example having length in the range 10m to 50m and diameter in the range 3m to 6m.
A plurality of conduit means may be provided for example as a horizontal or vertical aligned cluster of parallel aligned conduit means adapted for distribution of the fat absorbent stream uniformly across all conduits
at the inlet means and adapted for the convergence of fat absorbent at the outlet means. Distribution means may comprise guide vanes or the like or may comprise fluting portions of each conduit having an initial diameter equal to the diameter of the inlet means divided by the number of conduits and having a final diameter equal to the conduit diameter, the fluting portion being straight or curved in manner to provide fluid association of the converter inlet with the conduit in question.
Alternatively the holding unit may comprise one or more conduits configured in a plane as a circular or square spiral or as alternate linear and 180° bend sections in the form of a repeated folding configuration or the like.
A holding unit comprising a plurality of planar configured conduits as defined is conveniently provided as a horizontal or vertical stack of planar conduits. The holding unit may have distribution and convergence means as hereinbefore defined, in the case that the holding. unit comprises combined conduit diameter in excess of inlet diameter, or may simply comprise packing or stream dividers to reduce turbulence, in the case that the combined conduit diameter is substantially equal to the inlet diameter.
Preferably the holding unit is characterised by Peclet number, Pe, in excess of 10. Suitable Pe is the range of from 10 to 10,000, for example 100 to 2500, preferably 150 to 450, although other Pe values may be envisaged which provide for conversion of alkylene oxide,
but at lower efficiencies of operation, and therefore not benefiting from synergies which are of particular advantage in the present invention. Peclet number is defined, for a conduit type holding unit, as Pe = x L/DL, where is the average fluid velocity, L the
length of the tube and DL is the longitudinal (or axial)
dispersion coefficient. The latter can be calculated by one of the correlations known in the art. For a packed bed Pe can be calculated using the well known so-called Bodenstein Bo=2 relation, where Pe=Bo x L/dp (dp being the particle diameter).
In a preferred embodiment of the invention the apparatus comprises heating means associated with the inlet means of the holding unit, selected from heating means as known in the art. Preferably heating means comprises a heat exchanger providing heat exchange between fat absorbent and another process stream at higher temperature as hereinbefore defined such as steam, lean absorbent, stripper overhead and the like, or a combination thereof, more preferably by heat exchange selected from:
a fat/lean exchanger interchanging heat between hot aqueous lean absorbent from which fluid has been desorbed and fat absorbent with absorbed fluid which requires heating;
a fat absorbent / fluid exchanger interchanging heat between hot desorbed fluid and fat absorbent with absorbed fluid which requires heating.
Alternatively or additionally heating is by using an independent source such as:
steam from another process stage, in particular steam for venting (waste steam) or cooling to water (process steam); or
very hot condensate such as from the EO stripper bottom (lean absorbent)'; or
other in-process heat sources such as EO stripper overhead and the like;
and combinations thereof.
Preferably heat exchange comprises a line-up of suitable available heat sources and cooling sources. Preferably the total heat exchange time is adapted for the heat exchange area and exchange volumes, and is for example 1 to 6 minutes, with a heat exchange area of for example 750n\2.
Preferably the unit comprises a heat exchanger section wherein the fat absorbent stream is brought into thermal communication with the stripper overhead comprising hot C02, thereby heating the fat absorbent at the upstream end of the holding unit and cooling the stripper overhead CO2 before venting or forwarding for other applications.
A heat exchanger may be of any type as known in the art and is suitably of the shell and tube type or plate and frame type and is suitably provided at the upstream end or as part of the inlet means of the holding unit. Fat absorbent temperature may be regulated by heat exchanger factors such as selecting heat transfer area, and materials of heat exchanger (heat exchange coefficient) also selecting the temperature of the heat donating stream and the flow rates of respective streams.
The apparatus of the invention may be part of any apparatus in which a fluid stream is produced having an
amount of contaminating ethylene oxide. Preferably the apparatus is part of an EO unit for the conversion of ethylene to EO, more preferably part of an EO/EG unit, as hereinbefore defined.
It is a particular advantage that an EO unit may be minimally modified by the apparatus of the invention. Preferably the unit is modified by incorporating the apparatus in the feed stream to CO2 vent, to confer
increased residence time optionally additionally including a heat exchanger, for example by diverting a stream conduit such as the CO2 stripper overhead conduit for heat exchange with the fat absorbent. Additionally the unit may include means for mixing additional contaminated fluid streams.
In a further aspect of the invention there is provided an EO unit for the conversion of ethylene to ethylene oxide with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle and is remediated
using the apparatus as hereinbefore defined.
The invention is now illustrated in non limiting manner with reference to the following examples.
Examples
Comparative Example - Conventional Process without
treatment of SO in the feed stream for CO2 removal
The process of the operation as shown in Figures 1 and 3 makes use of a multitubular fixed bed reactor to produce ethylene oxide, and comprises contacting gaseous ethylene and oxygen with a silver on alumina catalyst (CRI EO catalyst S382) at a temperature in the range of 200 to 300°C, and at a pressure in the range of 12 to 22 bar a .
Unconverted oxygen and ethylene are recycled back into the reactor via the recycle stream. Reaction products (ethylene oxide and water) are removed in the EO recovery and removal section and fresh feeds are supplied.
A small bleed stream is withdrawn from the recycle gas and vented. The process results in gas leaving the EO reactor which carries an undesirable by-product CO2,
which has to be removed to avoid excessive build up that may impede EO production.
A CO2 removal section therefore provides for an amount of CO2 to be removed from the recycle and vented. A feed stream to the CO2 removal section, is contacted
with an aqueous carbonate absorbent solution which selectively absorbs CO2 from the recycle stream and which
contains potassium carbonate, potassium bicarbonate with potassium vanadate and potassium borate as activators. The fat absorbent is then flashed and stripped to remove volatiles and yield CO2 which is suitable for venting. The feed stream for CO2 removal can contain EO of the order of up to 500 ppm volume or even higher if not treated properly. In this example the EO concentration in this stream is 32 ppmv. Conditions and results are shown in Table 1.
Example 1 - Process of the Invention with increased residence time
In the process of the invention the CO2 removal unit is modified by incorporating an EO Converter of the invention comprising a reactor with substantially plug flow characteristics and a volume of 255 m^, as shown in Figures 2 and 4, resulting in an additional residence time of about 23.75 minutes. The plug flow reactor is
provided as a 0.8m diameter pipe of length 300m, and has a sufficient high maximum allowable operating pressure of about 2200kpa. In operating the apparatus an additional volume of the activated carbonate solution, as lean absorbent solution, of an amount of 225m3 is incorporated. The fat absorbent has a pH of from 10.2 to 10.5.
In this example the condensed water from the CO2
absorber overhead gas knockout is added to the fat absorbent as shown in Figure 4.
In the EO Converter the absorbed EO is converted to glycol and is removed from the CO2 removal unit with the condensed water from the CO2 absorber overhead (113) and is sent to waste water with the existing stream, as shown in Figures 4 and 5.
Operation of the process and the apparatus of the invention guarantees sufficient conversion of absorbed EO in the CO2 removal unit to reach less than about O.OOlkg/hr EO in the CO2 vent.
Conditions and results of Example 1 are shown in Table 1.
Example 2 - Process of the Invention with increased residence time and heating of fat carbonate
Operating the CO2 removal unit under the conditions as describee in Example 1 results in unfavorable CO2 absorption conditions. To reach high absorption efficiency the temperature in the CO2 absorber has to be lowered to a level as mentioned in the first column of Table 1 . That however would result in much lower EO conversions in the EO converter: with the apparatus of above Example 1 and under the same flow and same
residence times, that would result in an amount of EO in the CO2 vent in excess of 0-.1 kg/h.
In order to reach the required conversion in the CO2
removal unit the temperature of the fat carbonate has to be increased. This is preferably done in a way that is energy neutral to the process. Amongst others, two options are available: (1) a fat/lean heat exchanger interchanging heat between fat and lean carbonate or (2) a fat carbonate/CC>2 heat exchanger interchanging heat between CO2 stripper overhead and the fat carbonate.
Other methods can use (waste) steam heat or very hot condensate as independent heat source with or without outlet / inlet heat integration.
In this Example again the condensed water from the CO2 absorber overhead gas is added to the fat absorbent
as shown in Figure 4.
The surface area for a fat carbonate / CO2 heat
exchanger was 750m2. With this heat exchanger the fat carbonate temperature was increased to 92(91)°C without substantially changing conditions elsewhere in the process. The fat carbonate has a residence time in the piping and carbonate flasher of about 10 minutes as well as up to about 1 or 2 minutes in the new fat carbonate / CO2 heat exchanger. In order to achieve the required EO
conversion, additional residence time was provided in the new EO Converter, as described in Example 1.
The conversion of absorbed EO in the CO2 removal unit was found to give less than about 0.001 kg/hr EO in the CO2 vent, as in Example 1. This is despite lowering the temperature in the CO2 absorber. The result, with a combination cf increased temperature and residence time,
gives both excellent CC7 absorption and excellent EO conversion.
Conditions and results of Example 2 are shown in Table 1.
Table 1 - EO in vent gas under several different process conditions

(Table removed)

Figure 6 illustrates typical residual EO against residence time for conversion at a range of temperatures.
Example 3 - Apparatus of the Invention - Design of EO Converter (Holding Unit)
The design of an EO Converter was optimised to develop different configurations suitable for different reactors and operating conditions. The results are shown in Table 2.
Table 2 - EO Converter configurations according to the invention with equivalent EO conversion of 99.92% for all
cases.

(Table removed)

Alternative holding unit dimensions having Pe less than 450 include Pe = 419 or 208, a diameter of 0.8m or 1.0m and length is 300m or 400m.
A single pipe is engineered into a "vessel" reactor by folding the pipe. The "vessel" reactor is illustrated in Figure 7. The depth of the channels are equal to the width and do not exceed 2 meters. Several of the slices as drawn in the Figure are stacked on top of each other with thv outlet of each slice connected to the inlet of the following one, such that all channels are connected

in series. There is no preference for the channels running in horizontal or vertical direction.
A variant "vessel" reactor is a cylindrical vessel packed with cylindrical pipes which are connected in series by 180° bends in similar manner to Figure 7.

CLAIMS
1. Process for remediation of a fluid contaminated
with up to 1000 ppmv of alkylene oxide, comprising
contacting the contaminated fluid with an aqueous
absorbent to yield a fat absorbent having absorbed,
fluid, conferring intimate contact of fat absorbent and
alkylene oxide and conversion of alkylene oxide, wherein
the fat absorbent has a pH in the range of- from 7 to 11.
2. Process as claimed in claim 1, wherein the fluid
comprises a CO2 containing stream contaminated with
ethylene oxide (EO).
Process as claimed in claim 1 or claim 2, .wherein absorbent is selected from alkaline metal carbonates, preferably sodium (bi) carbonate and potassium (bi) carbonate; water; methyl alcohol; acetone; and solvents such as propylene carbonates or ethylene carbonates; and mixtures thereof with another absorbent or an activator, preferably selected from potassium and sodum vanadate, chromate, borate and mixtures thereof.
Process as claimed in any one of claims 1 to 3, which provides residence time of absorbent and alkylene oxide expressed as total residence time of greater than or equal to 11 minutes, for example up to 60 or 120 minutes; or expressed as additional residence time of greater than or equal to 4 minutes, for example up to 53 or 113 minutes.
Process as claimed in any one of claims 1 to 4, wherein fat absorbent temperature is in the range of from 80°C to 140°C.
Process for remediation of a fluid as claimed in any one of claims 1 to 5, contaminated with up to 1000

ppmv of alkylene oxide comprising contacting the fluid with an aqueous absorbent at an absorption efficiency in the range 50-99.9%, preferably 75-99.9%, most preferably 90-99.9%, to yield a fat absorbent having absorbed fluid, if required heating the fat absorbent, and maintaining for a desired residence time for conversion of alkylene oxide, wherein the process includes subsequently desorbing absorbed fluid, cooling the lean absorbent to a temperature for the required absorption efficiency and recycling to the absorption stage.
Process as claimed in claim 6,. wherein heating is by heat exchange with a further process stream or a combination thereof.
Process as hereinbefore defined in any one of claims 1 to 7, which is part of a process for the conversion of ethylene to ethylene oxide with formation of byproducts, water and CO2, wherein the product EO is isolated from the recycle gas and CO2 is removed from the recycle in the CO2 removal section and is remediated by the process
as defined in any one of claims 1 to 7.
9. Process as. claimed in claim 8, which is modified by increasing the volume of lean absorbent in the CO2 removal section to confer increased residence time; and optionally additionally by heating the fat absorbent .in the CO2 removal section.
10. Apparatus for remediation of fluid as hereinbefore defined in any one of claims 1 to 9, contaminated with up to 1000 ppmv of alkylene oxide, wherein the apparatus comprises a converter having inlet means connected to the outlet of a fluid absorber for contacting fluid and aqueous absorbent, a holding unit having a volume V for
The fat absorbent, and outlet means connected to the inlet of a fluid desorber, wherein the holding unit is shaped and configured and/or provides internals whereby fluid flow through the apparatus approaches plug flow.
Apparatus as claimed in claim, wherein the holding unit is selected from one or more conduit means for example one or more elongate pipes, optionally including internals selected from baffles, structured or unstructured packing and other internals known to provide flow approaching plug flow and substantially uniform residence time distribution.
Apparatus as claimed in claim 10 or claim 11, wherein the holding unit is characterized by peclet number, pe, in excess of 10, preferably in the range 10- 10,000, more preferably 100-2500.
Apparatus as claimed in any one of claims 10 to 12, which comprises heating means associated with the inlet means of the holding unit, preferably comprising a heat exchanger providing heat exchange between fat absorbent and another process stream at higher temperature or combination thereof
Apparatus as claimed in any one of claims 10 to 13, which is part of an E0 unit for the conversion of ethylene to ethylene oxide, more preferably part of an E0/EG unit, in which the apparatus is position in the C02 vent stream.

Documents:

2529-delnp-2005-1-Correspondence Others-(08-01-2015).pdf

2529-delnp-2005-1-Others-(08-01-2015).pdf

2529-delnp-2005-abstract.pdf

2529-delnp-2005-assignment.pdf

2529-delnp-2005-claims.pdf

2529-delnp-2005-Correspondance Others-(24-12-2014).pdf

2529-delnp-2005-Correspondence Others-(08-01-2015).pdf

2529-delnp-2005-Correspondence Others-(15-03-2012).pdf

2529-DELNP-2005-Correspondence Others-(20-10-2011).pdf

2529-delnp-2005-Correspondence Others-(21-05-2014).pdf

2529-delnp-2005-Correspondence Others-(21-06-2013).pdf

2529-delnp-2005-Correspondence Others-(24-07-2012).pdf

2529-delnp-2005-Correspondence-Others-(06-09-2010).pdf

2529-delnp-2005-Correspondence-Others-(06-11-2012).pdf

2529-DELNP-2005-Correspondence-Others-(08-02-2011).pdf

2529-DELNP-2005-Correspondence-Others-(14-01-2011).pdf

2529-DELNP-2005-Correspondence-Others-(30-09-2009).pdf

2529-DELNP-2005-Correspondence-Others-(7-1-2010).pdf

2529-delnp-2005-correspondence-others.pdf

2529-delnp-2005-description (complete).pdf

2529-delnp-2005-drawings.pdf

2529-delnp-2005-form-1.pdf

2529-delnp-2005-form-18.pdf

2529-delnp-2005-form-2.pdf

2529-DELNP-2005-Form-3 (7-1-2010).pdf

2529-delnp-2005-Form-3-(06-09-2010).pdf

2529-DELNP-2005-Form-3-(08-02-2011).pdf

2529-delnp-2005-Form-3-(15-03-2012).pdf

2529-DELNP-2005-Form-3-(20-10-2011).pdf

2529-delnp-2005-Form-3-(21-05-2014).pdf

2529-delnp-2005-Form-3-(21-06-2013).pdf

2529-delnp-2005-Form-3-(24-07-2012).pdf

2529-DELNP-2005-Form-3-(30-09-2009).pdf

2529-delnp-2005-form-3.pdf

2529-delnp-2005-form-5.pdf

2529-delnp-2005-GPA-(08-01-2015).pdf

2529-DELNP-2005-GPA-(14-01-2011).pdf

2529-delnp-2005-pct-101.pdf

2529-delnp-2005-pct-105.pdf

2529-delnp-2005-pct-304.pdf

2529-delnp-2005-pct-306.pdf

2529-delnp-2005-pct-408.pdf

2529-delnp-2005-pct-409.pdf

2529-delnp-2005-pct-416.pdf

2529-delnp-2005-petition-others.pdf

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Patent Number

264675

Indian Patent Application Number

2529/DELNP/2005

PG Journal Number

03/2015

Publication Date

16-Jan-2015

Grant Date

14-Jan-2015

Date of Filing

11-Jun-2005

Name of Patentee

SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V

Applicant Address

CAREL VAN BYLANDTLAAN 30, NL-2596 HR THE HAGUE, NETHERLANDS.

Inventors:

#	Inventor's Name	Inventor's Address
1	BOS ALOUISIUS NICOLAAS RENCE	BADHUISWEG 3, NL-1031 CM AMSTERDAM NETHERLANDS.
2	REKERS DOMINICUS MARIA	BADHUISWEG 3, NL-1031 CM AMSTERDAM NETHERLANDS.
3	ROTS ARTHUR WILLIBRORDUS TITUS	BADHUISWEG 3, NL-1031 CM AMSTERDAM NETHERLANDS.

PCT International Classification Number

C07D 301/32

PCT International Application Number

PCT/EP2003/051095

PCT International Filing date

2003-12-23

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	02258881.8	2002-12-23	EPO