Title of Invention

"NEW DUPLEX ADSORPTION PROCESS FOR FRACTIONATION OF GAS MIXTURE"

Abstract

This invention discloses new duplex adsorption process for fractionation of gas mixture capable of getting both components with high purity and yield. The system consisting of two beds having at least one adsorption bed capable of adsorbing more selectively . adsrobable or heavy component from the said feed gas mixture consisting of said component and a less selectively adsorbable other component comprising: introducing feed to be fractionated to first bed having developed gradient to facilitate adsorption of heavy component, removing the raffinate/light component from the said bed as first product recycling part of the raffinate at the bottom of the second bed, and recycling out going stream, optionally in part, to the first bed, first optionally equalizing the gradient within two beds followed by resetting the gradient simultaneously to facilitate desorption of the heavy component/extract, and collecting the heavy component/extract from the top of the bed. Further the gradients are developed by temperature or pressure swing. The process is performed at three pressure levels or two temperature levels and the extract being withdrawn at the end of evacuation and not throughout evacuation; wherein the said evacuation of the bed is carried in two stages.

Full Text

This invention relates to new duplex adsorption process for fractionation of gas mixture. FIELD OF INVENTION: Particularly, the invention relates to a duplex adsorption process for the separation of feed gas mixture by selectively adsorbing at least one more readily adsorbable component in an adsorbent material housed in a bed. The process employs either a difference in pressure, or temperature, for selective adsorption of one component leaving the effluent rich with other component, when a gas mixture is introduced into the adsorbent bed; followed by dcsorption of adsorbed component either by pressure or temperature swing. Further, the process is accomplished in two identical adsorption beds involving six-step adsorption cycle in case of pressure swing and four-step in case of thermal swing. More particularly, the process of the present invention relates to sharp separation of a gaseous mixture by performing adsorption in a sequential manner operating at three pressures in case of pressure swing adsorption and two temperature gradients in case of thermal swing adsorption. Still more particularly, the separated products are drawn at different levels in the process of this invention. The process is more efficient in separation of gaseous mixtures preferably binary mixture thereby resulting in obtaining both the products with higher purity. This in turn makes the process cost effective and suitable for diverse applications such as fractionation of air in to pure oxygen and nitrogen; separation of carbon dioxide and nitrogen; ethane/ethylene; propane/propylene; and methane/hydrogen. Specifically the process results in almost complete capture of carbon dioxide from flue gas. The process is further adaptable to be integrated with pressure as well as thermal swing adsorption thereby further improving its efficiency. BACKGROUND OF TOE INVENTION: Separation and purification of gas mixtures has long been important in various process industries. Capture of carbon dioxide from flue gases, recovery and purification of hydrogen from refinery off-gases, fractionation of air into nitrogen and oxygen, fractionation of lower alkane/alkene mixtures - like ethylene/ethane and propylene/propane - are some gas separation of prime importance carried out in chemical process industries. Since global warming has become a major environmental issue, separation of carbon dioxide, a gas primarily attributed for global warming, takes up priority. Additionally, flue gas discharged from thermal power stations contribute to more than 70% of total carbon dioxide discharged to the atmosphere enhancing the need for sequestering carbon dioxide from flue gas. Pressure swing adsorption (herein after referred as PSA) as well as thermal swing adsorption (herein after referred as TSA) processes are well known in the aft and has gained prominence as promising alternate technologies over the conventional cryogenic technologies for the separation and purification of gas mixtures due to reduced energy requirement. In adsorptive separation processes, the adsorption of the preferred component increases with increase in pressure or decrease in temperature. Similarly, the adsorbed components are desorbed by either reducing pressure or increasing temperature. The swing in temperature or pressure allows the regeneration/re-utilization of adsorbent bed to facilitate the fractionation of gas mixtures. Moreover, the said pressure/temperature swing is carried out in a synchronized manner in a sequence of steps whose time periods arc based on the gas mixture to be fractionated and the choice of adsorbent available. Thus when the feed gas mixture is introduced into the adsorbent bed mentioned above, it gets selectively depleted in one component, and the resulting outlet stream can be withdrawn until the breakthrough occurs in the bed. The adsorbed material is desorbed from the bed on saturation by reducing pressure or increasing temperature as mentioned earlier. All PSA/TSA processes are operated in a cycle which involves several steps. The PSA cycle involves adsorption of more selectively adsorbable component in a bed containing selective adsorbent at a higher pressure, discharging less selectively adsorbable component, lowering the pressure in the bed to desorb the adsorbed component typically from the feed end, and repressurizing the bed to make it ready for the next cycle. The TSA cycle involves adsorption of more selectively adsorbable component in a bed containing selective adsorbent at a lower temperature, discharging less selectively adsorbable component, increasing the temperature in the bed to desorb the adsorbed component typically from the feed end, and again lowering the temperature of the bed to make it ready for the next cycle. Here forward, the component which is most preferentially adsorbed shall be referred to as the 'heavy' component and the one which is the least preferentially adsorbed shall be referred to as the 'light' component. For example, in the case of air fractionation, nitrogen is the heavy component and oxygen is the light component. The prior art, with regard to PSA, known to the inventor includes US Patents No. 3,717,974 ('974); 4,013,429 ('429); 4,589,888 ('888); and 5,032,150 ('150). All these patents teach to using conventional PSA cycle for the fractionation of air to produce oxygen, i.e. the patents cited above discloses processes that yield only the light component as the pure product. The technology fails to simultaneously recover nitrogen and oxygen from the air. Both '429 and ' 150 adopts cycles involving vacuum in the range of 30 - to 70 torr. On the other hand, US 4,359,328 describe an inverted Pressure Swing Adsorption process, which can yield the heavy component, i.e. nitrogen, as the pure product. The process is carried out in at least two beds and comprises a low pressure adsorption enabling adsorption of light component, pressurization to high pressure, purging at said high pressure and depressurization for release of adsorbed and desirable heavy component. The feed is introduced at low pressure. The part of the effluent from the bed is pressurized and used as countercurrent purge gas to recover the desired and adsorbed component. As the name indicates the process is just 'inverse' of normal PSA process. The main drawback of this process is that the heavy component gets concentrated in low-pressure effluent on the product end of the bed. This results in getting part of the undesirable less selectively adsorbable component in to the product thereby not only reducing efficiency of the process but also resulting in the need to be operated for many cycles and or with a high reflux, thereby making the process uneconomical. Another mechanism is to adopt cocurrent-displacement type of PSA - a blend of conventional and inverted processes. This comprises introducing feed gas to a high pressure adsorbent bed to adsorb heavy component (nitrogen in case of air fractionation) and discharging the effluent rich in light component/less adsorbable component, stopping the supply of feed gas before the heavy component reaches discharge end and loading the hcd with heavy component rich gas at feed end as cocurrent purge stream and desorbing the heavy component using counter current depressurization at feed end. Typical cocurrent processes are disclosed in US Patent numbers 4,599,094 and 4,810, 265. The purity of the . heavy component is dictated by the kind of vacuum that is employed and extend of breakthrough in the cocurrent purge step. Additionally, the process has limited applications and is also not suitable for the gas mixture having low concentration of heavy component. This in turn makes process cost extensive and less efficient for commercial purposes. US 4,354,859 advocates another approach, called the 'molecular-gate' process, for separation of gas mixture by imposing cyclic pressure changes on both ends of a bed and introducing feed at intermediate level. Though this process also enables in getting isolation of two product components, it poses problem in scale up to commercial size and maintaining the operational cost at low level. US 5,085,674 describe a duplex PSA process, which is economical, commercially feasible and capable of recovering two product streams. One section of the process is operated as normal PSA while the second one is operated as inverted PSA process. The feed gas is introduced at intermediate level. According to the disclosure, the low pressure effluent from the normal process is fed to the low pressure feed end of inverted section and the high pressure effluent from the inverted section is passed to the feed end of the normal section. The feed gas after pressurizing is introduced at an intermediate point of either bed through valves. The light component recovered from the upper end of the beds is collected through valves. A portion of the recovered component is reintroduced to either bed through valves. The heavy component is collected from the bottom of the beds through valves is compressed and recovered as one of the product. Part of this recovered product is introduced from the bottom of the bed to displace the light component from the top of the bed. Thus, the light component is displaced from the normal bed and heavy component get displaced from the inverted bed. The process inherently overcomes the draw backs of normal or inverted bed PSA processes only to some extent. The low pressure employed in the process was 570 torr. The prior art known to the inventor with regard to thermal swing adsorption (TSA) includes US 20040069144. According to this invention the feed gas mixture is passed through an adsorbent bed at a low temperature to adsorb one component selectively and collecting the other component as an effluent/raffinate followed by increasing the temperature of the bed enabling desorption of adsorbed component, which is collected as desired component. This is achieved by circulating a heat exchange fluid through the heat exchanger and exchanging heat with the adsorption layer. The heat exchange fluid, which is now cold, then flows into a second heat exchanger to exchange heat with a second adsorption layer and cools a second adsorption layer containing a second adsorption media. The main thrust of the invention is in eliminating the use of a microporous contactor assembly for mass transfer (interfacial diffusion) of a working compound from a first medium to a second medium disclosed in US Patent No. 6,126,723. Further the invention also advocates increasing contact surface by engaging various combinations of multiple channels with appropriate diameter. However, the process does not teach the recycling of outgoing stream to the other bed to develop partial pressure or vacuum to improve efficiency. Further, in the duplex systems the products are drawn simultaneously. As can be seen from the disclosure herein above the present PSA processes are less efficient in fractionating the feed mixture leading to one impure final product. Thus, these processes fail to yield both the products of desired purity. The processes require high vacuum application, which also results in requiring more infrastructures thereby making processes more energy and cost extensive. Additionally, most of the processes can yield only one component as a pure product and the processes that are able to recover both the products are less pure. Further, in the existing PSA processes, feed is normally introduced at the bed end and the products are generally drawn simultaneously requiring number of valves, high reflux ratio, and large number of cycles specifically where invert process is adopted. The existing TSA processes generally are operated by circulating the liquid to generate thermal swing. Additionally heat exchangers are employed to cither heat or cool the adsorbent material for desorplion or adsorption of the desired component. Thus there remains a need to develop effective adsorption process for the fractionation of gas mixtures. Either PSA or TSA or blend of two processes that is economic, energy effective, more efficient, capable of clean fractionation of gas mixture and high recovery of both the products to desired level of purity is desirable. One way to reduce cost is to increase efficiency by producing relatively high purity products, decrease number of beds or volume of beds, and decrease in operational cost and/or infrastructure cost. The inventors after prolonged and painstaking research have been able to develop a duplex pressure and/or thermal Swing adsorption process for sharp separation of gas mixture. The process of the present invention further relates to PSA, TSA and a blend thereof. The process is able to fractionate the mixture cleanly recovering both the components with high purity and yield. The process does not employ high vacuum like in the case of conventional PSA. The process also eliminates circulation of liquid used for heating or cooling adsorption bed in case of TSA. The major distinct feature is the introduction of feed at mid point, avoiding simultaneous withdrawal of both components and recycling the adsorbed component or effluent at the top or the bottom of each bed. The PSA process uses six-step cycle and TSA process requires four-step cycle for efficient fractionation. SUMMARY OF THE INVENTION: The main object of the present invention is to provide a new duplex adsorption process for the fractionation/sharp-separation of gas mixture, involving either pressure or thermal swing, to obtain both the products with higher purity without loss of desired purified products. Another object is to provide a duplex PSA/TSA process for efficiently separating binary gas mixture into pure gas fractions with very high recovery of both the components. Yet another object of the invention is to provide a PSA/TSA process accomplished in two identical adsorption beds involving six-step adsorption cycle in case of PSA and four-step adsorption cycle in case of TSA. Still other object is to provide PSA process for sharp separation of a gaseous mixture by performing adsorption in a sequential manner operating at three different pressures or two different temperature gradients. Further, the product streams are drawn at different levels, i.e. while one product is drawn as product continuously during the feed step and at high pressure, the other product is not drawn continuously during evacuation like in other PSA available in literature - the said evacuation is carried in tow stages, during first stage the stream resulting from evacuation is totally recycled and only during the second stage of evacuation the resulting stream is drawn as the second product. Still another object is to provide PSA process that does not require application of high vacuum and/or skilled personnel. The process thus in turn proves to be energy and cost effective and suitable for diverse applications such as fractionation of air into pure oxygen and nitrogen; separation of carbon dioxide and nitrogen; ethane/ethylene; propane/propylene; and methane/hydrogen. Specifically the process results in almost complete capture of carbon dioxide from flue gas. In case of TSA the thermal swing is developed & maintained by displacing a heat transfer liquid through multiple channels and not by entirely circulating. Additionally, the thermal gradient is further maintained by recycling the out-coming streams from one bed to the other bed. With these and other objects in mind, the invention is further described in detail. Adsorption process of the present invention is accomplished in two adsorbent beds in a cyclic manner by periodically loading and unloading the bed with a gas mixture whose components are to be separated as well as the streams evolving of various beds in a sequential manner. The sequence with which the gases flow in and out of the bed as well as between them is called cycle. Herein after the component that gets preferentially adsorbed is referred to as an 'extract' and the component that is less selectively adsorbed is termed as 'raffinate'. BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 depicts schematic diagram of six steps of the proposed cycle. Steps 1 -3 constitute the half-cycle of the process. Steps 3-6 are the mirror images of steps 1-3. In step 1, adsorbent bed-1 is at pressure P1 and adsorbent bed-2 is at pressure P3. The feed is introduced at a point somewhere along the length of adsorbent bed-1. The raffinate is drawn from the bottom end of adsorbent bed-1 as one product. A part of the raffinate is recycled to the bottom end of adsorbent bed-2. The outgoing stream from the top end of adsorbent bed-2 is recycled back to the top end of adsorbent bed-1 using a compressor. In step 2, adsorbent bed-2 is first pressure equalized with adsorbent bed-1. Further, adsorbent bcd-1 is evacuated to pressure P1 using a vacuum pump. At the same time, adsorbent bed-2 is pressurized to P1. In step 3, adsorbent bed-1 is evacuated to pressure P3 using a vacuum pump and the extract is drawn as the second product. The adsorbent bed-2 is frozen during step 3. In step 4, adsorbent bed-2 is at pressure P1 and adsorbent bed-1 is at pressure P3. The feed is introduced at a point somewhere along the length of adsorbent bed-2. The raffinate is drawn from the bottom end of adsorbent bed-2 as one product. A part of the raffinate is recycled to the bottom end of adsorbent bed-1. The outgoing stream from the top end of adsorbent bed-1 is recycled back to the top end of adsorbent bed-2 using a compressor. In step 5, adsorbent bed-1 is first pressure equalized with adsorbent bed-2. Further, adsorbent bcd-2 is evacuated to pressure P2 using a vacuum pump. At the same time, adsorbent bed-1 is pressurized to P1. In step 6, adsorbent bed-2 is evacuated to pressure P3 using a vacuum pump and the extract is drawn as the second product. The adsorbent bed-1 is frozen during step 6. Figure 2 depicts the schematic of the proposed thermal swing adsorption scheme. In step 1, in a priori, desired temperature gradient of AT| and AT2 is maintained across the two beds (bed-1 and bed-2 respectively) by circulating the heat transfer fluid through a bundle of tubes. Bed 1 is relatively colder than bed-2. The feed is introduced at a point somewhere along the length of adsorbent bed-1. The raffinate is drawn from the bottom end of adsorbent bed-1 as one product. A part of the raffinate is recycled to the bottom end of adsorbent bed-2. The outgoing stream from the top end of adsorbent bed-2 is recycled back to the top end of adsorbent bed-1. In step 2, the heat transfer fluid is circulated in such a way that the temperature difference across bed-1 and bed-2 are reversed, i.e. ΔT2 and ΔT1 respectively. Thereby, at the end of the step bed -1 is relatively hotter than bed-2. In step 3, in a priori from step 3, bed-1 is relatively hotter than bed-2 and a desired temperature gradient of ΔT2 and ΔT1 is maintained across the two beds (bed-1 and bed-2 respectively). The feed is introduced at a point somewhere along the length of adsorbent bed-2. The raffinate is drawn from the bottom end of adsorbent bed-2 as one product. A part of the raffinate is recycled to the bottom end of adsorbent bed-1. The outgoing stream from the top end of adsorbent bed-1 is recycled back to the top end of adsorbent bed-2. In step 4, the heat transfer fluid is circulated in such a way that the temperature difference across bed-1 and bed-2 are retraced back to ΔT1 and ΔT2 respectively such that bcd-1 is cold again and ready for the onset of the next cycle. Moreover, this process can accomplish very sharp separation with just two beds unlike in conventional pressure swing adsorption processes wherein a minimum of four beds is required for accomplishing similar kind of separation STATEMENT OF THE INVENTION: Accordingly the present invention provides New duplex adsorption process for fractionation of gas mixture, in a system consisting of two beds having at least one adsorption bed capable of adsorbing more selectively adsrobable or heavy component from the said feed gas mixture consisting of said component and a less selectively adsorbable other component comprising: (a) introducing feed to be fractionated to first bed having developed gradient to facilitate adsorption of heavy component, (b) removing the raffinate/light component from the said bed as first product recycling part of the raffinate at the bottom of the second bed, and recycling out going stream, optionally in part, to the first bed, (c) first optionally equalizing the gradient within two beds followed by resetting the gradient simultaneously to facilitate desorption of the heavy component/extract, and (d) collecting the heavy component/extract from the top of the bed. According to one of the embodiments of this invention the gradients may be developed either by altering pressure or temperature. According to other embodiment of this invention the feed may be introduced any where along the length of the bed depending on stoichiometry of the feed composition. According to another embodiment of this invention the gradients may be developed by altering pressure in PSA process comprising 2 beds and six-step cycle having two pressure equalization steps, and four evacuation steps. According to yet other embodiment of this invention the process preferably operated at three pressure levels P1, P2, and P3, wherein P1 is the highest and P3 is the lowest. According to yet another embodiment of this invention the gradients when arc developed by altering pressure comprises: (a) introducing feed to first bed having developed high pressure at level 1 to facilitate adsorption of extract/heavy component, (b) removing the raffinate/light component from the said bed as first product, recycling part of the raffinate at the bottom of the second bed having lowest pressure level 3, and recycling out going stream on compressing to the first bed, (c) first equalizing the pressure in second bed with the one in first bed then simultaneously depressurizing first bed to intermediate level 2 and pressurizing second bed to highest level 1 to facilitate desorption of the heavy component/extract, and (d) further depressurizing first bed to lowest pressure level 3 to facilitate desorption of the heavy component/ extract as second product followed by collecting the extract from the top of the first bed while freezing the second bed, (e) repeating steps (a) to (c) in a cyclic manner while introducing feed to second bed. Further, the process when involves developing gradient with pressure swing wherein the extract/heavy component product being withdrawn at the end of evacuation and not throughout evacuation; wherein the said evacuation of the bed is carried in two stages. According to yet another embodiment of this invention the gradients when arc developed by altering temperature comprising: a. introducing feed to first bed maintained at low temperature level 1 to facilitate adsorption of extract/heavy component, b. removing the raffinate/light component from the said bed as first product, recycling part of the raffinate at the bottom of the second bed maintained at high temperature level 2, and recycling out going stream in part to the first bed, while drawing the remaining part as second product, c. resetting the temperature gradient in two beds and, d. repeating cycles (a) to (c) in a cyclic manner while introducing feed to second bed. Further, the temperature gradient is developed by displacing a heat transfer liquid capable of increasing or reducing temperature through a bundle of tubes housed in adsorbent bed. The process is operated at two temperature gradients ΔT1 and ΔT2, which is dependant on the system to be fractionated and the choice of adsorbent available. DETAILED DESCRIPTION: The PSA cycle is operated at three different pressures designated as P1, P2, and P3 PI is greater than P2, and P2 is greater than P3 Thus, P| is highest and P3 is lowest. The choice of the above pressures is made depending on the system that is to be fractionated and the adsorbent available. The cycle comprises of six steps, the operation of which is described herein after. Step 1: The adsorbent bed 1 is at pressure P1 and adsorbent bed 2 is at pressure P3. The feed gas mixture to be fractionated is introduced at along the length of bed allowing the heavy component or the extract to get adsorbed and the raffmate is drawn from the bottom of bed 1. A part of the raffinatc is introduced at the bottom of the bed 2 The outgoing stream from the bed 2 is recycled back to bed 1 from the top end of bed 1 after compressing. Step 2: Bed 2 is pressure equalized with bed 1 and bed 1 is depressurized or evacuated to pressure P2. Simultaneously bed 2 is pressurized to pressure IV Step 3: Bed 1 is evacuated to pressure P3 applying vacuum and the extract is withdrawn as a second component. During step 3, bed 2 is frozen. Step 4: Bed 2 is pressurized to P1 and bed 1 is at pressure P3. The feed gas is introduced along length of the bed 2. The raffmate is drawn as one product from the bottom of bed 2. Part of the said raffmate is recycled in bed 1 from the bottom. The outgoing stream is introduced to bed 2 from the top after compression. Step 5: Bed 1 is first pressure equalized with bed 2.Then bed 2 is evacuated to pressure P2 using vacuum pump and bed 1 is pressurized to P1. Step 6: Bed 1 is kept frozen and bed 2 is further evacuated to pressure level P3 and the extract is drawn from Bed 2 as a second product. These six steps complete the cycle and the cycle can be repeated till a cyclic-steady state is reached. The TSA process is operated at two temperatures. The cycle is completed in 4 steps. Step 1: Temperature gradient ΔT1 and ΔT2 is maintained by displacing, not circulating, a heat transfer fluid such as Dowtherm fluid engaging a bundle of tubes adequate to create the temperature difference. Bed 1 is cooler than bed 2. The feed is introduced along the length of the bed allowing to get more adsorbable component adsorbed drawing other fraction as one of the product, or raffinate, from the bottom of the said bed. Part of the raffinate was recycled to the bottom of the bed 2. The outgoing stream from the top of bed 2 is partly recycled to the top of bed 1 and partly collected as extract. Step 2: The heat transfer fluid is displaced just enough to reverse the temperature difference in two beds thereby making bed 1 hotter than bed 2 at the end of the step. Step 3: The feed is introduced along length of bed 2. The raffinate withdrawn from the bottom of bed 2 is partly recycled to the bottom of bed land the outgoing stream from the top of bed 1 is partly recycled to the top of bed 2 and partly collected as extract. Step 4: The heat transfer fluid is displaced in such a manner that the temperature difference across the beds is retraced back to ΔT1 and ΔT2 for onset of the next cycle, It may be pertinent to indicate here that the feed is generally introduced anywhere along the length of the bed. For Example in case of equimolar feed composition, it is preferably introduced at mid point. The variation of the inlet position thus is governed by the proportion of heavy and light component in the feed. While the invention has been described with reference to capture of carbon dioxide, it should be recognized that the process is equally applicable to other gases as well as exemplified herein after where the two components have different adsorbing properties with regard to pressure or temperature. Further a person skilled in the art can modify the process conditions/parameters suitably to apply the principle to other gases. The following studies give comparative account of the efficiency of the process of the present invention and existing most relevant process with regard to fractionation of gases. Binary feed comprising 80 mol% nitrogen and 20 mol % carbon dioxide was fractionated by PSA process using zeolite 13X. The process of present invention gave both the extract and raffinate in excess of 99 mol%. Table 1, 2, and 3 shows the effect of feed flow rate, pressure P2 and the raffinate cycle ratio on the purities of carbon dioxide and nitrogen. TABLE 1 Effect of feed flow rate on purities of carbon dioxide and nitrogen. (L: 1 m;D: 2.5cm; T: 298.15K) (Table Removed) TABLE 2 Effect of pressure P2 on the purities of carbon dioxide and nitrogen.. (L: 1 m;D: 2.5cm; T: 298.15K) (Table Removed) TABLE 3 Effect of raffinatc recycle on purities of carbon dioxide and nitrogen. (L: 1m; D: 2.5cm; T:298.15K) (Table Removed) Studies were also conducted for fractionation of equimolar mixture of nitrogen and oxygen with zeolite 5A adsorbent Table 4 gives the comparative account. TABLE 4 Effect of feed flow rate on purities of oxygen and nitrogen. (L: 1m; D: 2.5cm; T: 298.15K) (Table Removed) TABLE 5Comparison of conventional PSA with PSA o the present invention for nitrogen/methane separation using clinoptilolites (Table Removed) Wli CLAIM: 1. New duplex adsorption process for fractionation of gas mixture in a system consisting of two beds having at least one adsorption bed capable of adsorbing more selectively adsrobable or heavy component from the said feed gas mixture consisting of said component and a less selectively adsorbable other component comprising: (e) introducing feed to be fractionated to first bed having developed gradient to facilitate adsorption of heavy component, (1) removing the raffinate/light component from the said bed as first product recycling part of the raffinate at the bottom of the second bed, and recycling out going stream, optionally in part, to the first bed, (g) first optionally equalizing the gradient within two beds followed by resetting the gradient simultaneously to facilitate dcsorption of the heavy component/extract, and (h) collecting the heavy component/extract from the top of the bed. 2. New duplex adsorption process as claimed in claim 1 wherein the gradients are developed either by altering pressure or temperature. 3. New duplex adsorption process as claimed in claims 1 & 2 wherein the feed is introduced any where along the length of the bed depending on stoichiometry of the feed composition. 4. New duplex adsorption process as claimed in claims 1 to 3 wherein the gradients are developed by altering pressure comprising 2 beds and six-step cycle having two pressure equalization steps, and four evacuation steps. 5. New duplex adsorption process as claimed in claims 1 to 4 wherein the process is operated at three pressure levels P1, P2, and P3, wherein P1 is the highest and P3 is the lowest. 6. New duplex adsorption process as claimed in claims 1 to 5 wherein the gradients are developed by altering pressure comprises: (a) introducing feed to first bed having developed high pressure at level 1 to facilitate adsorption of extract/heavy component, (b) removing the raffinate/light component from the said bed as first product, recycling part of the raffinate at the bottom of the second bed having lowest pressure level 3, and recycling out going stream on compressing to the first bed, (c) first equalizing the pressure in second bed with the one in first bed then simultaneously depressurizing first bed to intermediate level 2 and pressurizing second bed to highest level 1 to facilitate desorption of the heavy component/extract, and (d) further depressurizing first bed to lowest pressure level 3 to facilitate desorption of the heavy component/ extract as second product followed by collecting the extract from the top of the first bed while freezing the second bed, (e) repeating steps (a) to (c) in a cyclic manner while introducing feed to second bed. 7. A process as claimed in claims 1 to 4 developing gradient with pressure swing wherein the extract/heavy component product being withdrawn at the end of evacuation and not throughout evacuation; wherein the said evacuation of the bed is carried in two stages. 8. New duplex adsorption process as claimed in claims 1 &2 wherein the wherein the gradients are developed by altering temperature comprising: (a) introducing feed to first bed maintained at low temperature level 1 to facilitate adsorption of extract/heavy component, (b) removing the raffinate/light component from the said bed as first product, recycling part of the raffinate at the bottom of the second bed maintained at high temperature level 2, and recycling out going stream in part to the first bed, while drawing the remaining part as second product, (c) resetting the temperature gradient in two beds and, (d) repeating cycles (a) to (c) in a cyclic manner while introducing feed to second bed. 9. New duplex adsorption process as claimed in claims 1, 2, 3, and 7 wherein the wherein the temperature gradient is reset by displacing liquid capable of increasing or reducing temperature through multiple channels housed in adsorbent bed. 10. New duplex adsorption process for fractionation of gas mixture substantially as herein described.

Documents:

1567-del-2006-abstract.pdf

1567-del-2006-Claims (20-11-2012).pdf

1567-del-2006-Claims-(20-11-2012).pdf

1567-del-2006-claims.pdf

1567-DEL-2006-Correspondence Others-(01-03-2012).pdf

1567-del-2006-correspondence others-(17-04-2008).pdf

1567-del-2006-Correspondence-others (20-11-2012).pdf

1567-del-2006-Correspondence-Others-(07-08-2013).pdf

1567-del-2006-Correspondence-others-(20-11-2012).pdf

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1567-del-2006-description (complete).pdf

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1567-del-2006-form-1.pdf

1567-del-2006-form-18-(17-04-2008).pdf

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1567-DEL-2006-GPA-(01-03-2012).pdf

1567-del-2006-GPA-(07-08-2013).pdf

1567-del-2006-gpa.pdf