Title of Invention

METHOD AND APPARATUS FOR INTRODUCING SULPHUR DIOXIDE INTO AQUEOUS SOLUTIONS

Abstract

A fluidized-bed process for gas reduction of particulate iron oxide- containing ores, the process comprising the steps of: preheating, and also optionally pre-reducing the ore in the presence of a reducing gas produced from coal in a first fluidized-bed reactor designed as a pre-heating stage; then reducing the preheated ore to sponge iron in the presence of a reducing gas produced from coal in a reduction stage comprising at least one further fluidized-bed reactor; conducting reducing gas for the reduction step to the reduction stage via a first feed duct; conducting reducing gas for the preheating step from the reduction stage to the pre-heating stage via a second feed duct; maintaining the fluidized beds at a pressure of <5 bars, drawing off and purifying the reducing gas from the preheating stage as an export gas; heating the reducing gas fed to the reduction stage and/or pre-heating stage by combustion together with oxygen and/or air, of a quantity of combustible material; independently controlling the composition and/or temperature of the reducing gas provided to the fluidized-bed stages.

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See Section 10; rule 13] "A PROCESS FOR THE GAS REDUCTION OF PARTICULATE OXIDE-CONTAINING ORES AND A PLANT THEREOF" VOEST-ALPINE INDUSTRIEANLAGENBAU GMBH & CO., an Austrian company, of Turmstrasse 44, A-4020 Linz, Austria, POHANG IRON & STEEL CO., LTD., of 1 Geo Dong-dong, Pohang City, Kyong Sang, Book-do 790-300, Korea and RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, INCORPORATED FOUNDATION, of San-32 Hyoja-Dong, Pohang City, Kyong Sang Book-Do, 790-330, Korea The following specification particularly describes the invention and the manner in which it is to be performed: Process And Plant for the Gas Reduction of Particulate Oxide-containing Ores The invention relates to a process for the gas reduction of particulate oxide-containing ores, in particular iron-oxide-containing material, in the fluidized-bed process at a pressure of In case the reduction of the particulate oxide-containing ore takes place in several fluidized-bed reactors subsequently connected, the reducing gas being conducted from one reactor to the other in counterflow to the ore, the solid gets heated up stepwise while the enthalpy of the reducing gas decreases at the same time, partly due also to the reactions taking their course in the reduction. This may possibly lead, in the individual reduction stages for the solid, to temperatures that are so low that the reaction between reducing gas and oxide-containing ore is impeded kinetically and thermodynamically, i.e., the reduction of the ore is not done up to the desired degree during its temporal residence in the reduction reactor. In a process of the initially mentioned kind, known from AT 402 937 B, iron-oxide-containing material is reduced in four fluidized-bed reduction zones subsequently connected in series. In order to set a constant, more or less equally high temperature in all of the fluidized-bed reduction zones, freshly formed reducing gas is, in addition to the reducing gas flowing through the fluidized-bed reduction zones arranged in series, in part fed directly to the fluidized-bed reduction zones following the fluidized-bed reduction zone arranged first in the direction of flow of the reducing gas, so that the fluidized-bed reduction zones are connected both in series and in parallel with regard to the reducing-gas conduct. Here, the additionally fed, freshly formed reducing gas is preferably fed to the individual fluidized-bed reduction zones in an amount of 5 to 15%. However, a disadvantage connected therewith is that the pre-reduction stages have to be configured for gas amounts getting bigger and bigger towards the pre-heating stage as in each stage following the final reduction stage additional fresh reducing gas is added to the reducing gas leaving the preceding stage. Supposing further that in the final reduction zone a specific amount of reducing gas is in any case required for the complete reduction of the material used, irrespective of whether there is an additional parallel guidance of the reducing gas or not, an arrangement according to AT 402 937 B results, all in all, in a higher consumption of reducing gas. In WO 97/13880 A and WO 97/13878 A there is described a process in which a portion of a reducing gas flowing from a final reduction stage into a pre-reduction stage is branched off, scrubbed, purified from CO2 and heated and subsequently is recycled into the final reduction stage. In the pre-heating stage, oxygen is burnt with a portion of the reducing gas introduced into this stage, for the purpose of increasing its temperature. According to WO 97/13880 A and WO 97/13878 A, only the temperatures in the fluidized-bed reactors corresponding to the final reduction stage and the pre-heating stage are controlled by way of a gas recycling and/or partial combustion. The reactors located between these two stages are, however, dependent on the conditions in the final-reduction fluidized-bed reactor. From JP 58-34114 A there is known a process for the reduction of fine-grained iron ore, in which the reducing gas for the final reduction stage is produced by decomposition and reformation of hydrocarbon by means of the oxidizing off-gas drawn off the final reduction zone, the iron ore being pre-reduced in a first stage by carbon separated from the hydrocarbon. For providing the energy needed for the production of the reducing gas, the oxidizing off-gas is heated before being brought into contact with the hydrocarbon. In US 3,985,547 A there is described a process for the reduction of iron ore in a multiple fluidized-bed reactor, in which fresh reducing gas is produced by substoichiometric combustion of methane and oxygen in a burner associated with the reactor, which is arranged with its outlet opening between the lowermost fluidized bed and the fluidized bed located thereabove. The spent reducing gas leaving the uppermost fluidized bed is purified, liberated from water and CO2 and, in the heated state, fed to the lowermost fluidized bed as a recycling reducing gas. The invention has as its object to provide, in a process of the initially described kind, a possibility of independent temperature increase in the individual reduction stages without having to substantially increase the amount of reducing gas or needing an enlarged dimensioning of plant elements. The aim is to set the temperature in each individual fluidized-bed reduction stage and to set an optimum solid/gas-temperature profile as well as gas-quality profile above the fluidized-bed stages. According to the invention, this object is achieved in that heat is supplied to the reducing gas fed to the reduction stage and/or pre-heating stage, namely by combustion, together with oxygen and/or air, of a portion of the reducing gas provided for the gas reduction in the reduction stage and/or the pre-heating stage. The partial combustion of the reducing gas represents the most efficient enthalpy addition and further offers the advantage that no substantial increase in the gas amount is necessary. Furthermore, this object is achieved in that heat is supplied to the reducing gas by combustion of a portion of the export gas together with oxygen and/or air. A further possibility of achieving the inventive object consists in burning, together with oxygen and/or air, a portion of the cooling gas used for cooling the reducing gas to be introduced into the final reduction zone, whereby heat is supplied to the reducing gas fed to the reduction stage and/or pre-heating stage. Oxygen addition to the reducing gas allows for an individual energy distribution to the individual reactors, so that in for example three fluidized-bed reactors the inlet temperature of the reducing gas-when adding oxygen/air to all three reactors-could be as follows: 920°C(lst reactor)/890°C(2,ld reactor)/900°C(3rd reactor). In case an oxygen/air addition was done only before the fluidized-bed reactor corresponding to the pre-heating stage (3r reactor) and the final reduction stage (1st reactor), the inlet temperatures would have to change to 920°C/750°C/1140°C in order to obtain the same reduction result, which would lead to an increased thermal load on reactor 3 and the ore charged into reactor 3. This problem is avoided by a process according to the invention. By an increase in the reducing-gas temperature according to the invention, autoreforming reactions in the gas phase are preferred thermodynamically and kinetically, the dust present in the reducing gas optionally acting as a catalyst. In these autoreforming reactions, methane is reacted with carbon dioxide and/or water vapor to become carbon monoxide and/or hydrogen. This in situ generation of reducing constituents brings about an improvement of the reducing-gas analysis and thus also a thermodynamic improvement of the ore reduction. Preferably, the portion to be burnt of the reducing gas, export gas or cooling gas is subjected to a scrubbing operation before being burnt, whereby locally very high temperatures originating from a combustion of dust-loaded gases and susceptible of resulting in a fusing of the dust due to a Boudouard reaction are avoided. The oxygen and/or air necessary to the combustion of the reducing gas are fed into the reducing-gas feed duct or reducing-gas duct, which transports the reducing gas into the first fluidized-bed reduction zone and/or from one fluidized-bed reduction zone into the reduction zone arranged subsequently, advantageously via lances which at the same time act as burners. Thanks to this arrangement, the requirements as to equipment are kept very limited. Another possibility of setting the temperature in the reduction fluidized-bed stages consists in supplying heat to the reducing gas by burning external combustible gas and/or solid and/or liquid fuels together with oxygen and/or air. According to a preferred embodiment, the combustion of the combustible gases or solid and/or liquid fuels is done in a burner provided in the reducing-gas feed duct or reducing-gas duct. Suitably, the duct may have an enlarged site in this area. According to another preferred embodiment, the combustion of combustible gas or solid and/or liquid fuel is done in a combustion chamber separated from the reducing-gas feed duct or reducing-gas duct, the combustion gases and possibly not burnt solids subsequently being introduced into the reducing-gas feed duct or reducing-gas duct. Thereby, hot flame fronts that possibly appear are leveled before they get into contact with dust-loaded reducing gas and likewise cause a fusing of the dust in the ducts. Advantageously, combustible gas or solid and/or liquid fuel is burnt together with oxygen and/or air by means of at least one burner which is provided in the reduction fluidized-bed reactor. Here, the combustion gases are introduced directly into the fluidized-bed reactor. According to another preferred embodiment, only oxygen and/or air are fed into the fluidized-bed reactor via a burner, preferably a lance, and the reducing gas is directly burnt there. Here, the burner suitably may be arranged either below the fluidized bed formed in the fluidized-bed reactor, on the level of the fluidized bed or above the same, whereby the heat can be supplied to the reducing gas extremely selectively and particularly efficiently. The two latter alternatives are particularly advantageous because here, the thermal load on the distributor bottom is smaller and fouling of solid on and/or in nozzles or openings of the distributor bottom is prevented or at least reduced. According to a preferred embodiment of the process according to the invention, reducing gas and/or export gas and/or cooling gas and/or external combustible gas and/or solid and/or liquid and/or gaseous fuel on a hydrocarbon basis are additionally used for the combustion. This embodiment proves to be particularly advantageous when any fuel from the above-indicated group is present in excess or reducing gas, export gas and/or cooling gas are needed mainly for other purposes and therefore are not available in a sufficient quantity. Preferably, a material increasing the proportion of reductants in the reducing gas by at least partially reacting with the reducing gas, in particular natural gas and/or coal, is admixed to the reducing gas fed to the reduction stage and/or pre-heating stage. Hereby, the phenomenon of sticking, which impedes the reduction process, is avoided. The reason for it are directional, needle-like iron precipitations on the surfaces of the fine ore particles, which originate at higher temperatures and a low reduction potential. The reaction of the materials may also be done in a burner. Feeding additional fuels allows to positively influence the temperature setting, the oxidation degree of the reducing gas and optionally an increase in the total gas amount. Furthermore, the invention provides for a process in which a material increasing the proportion of reductants in the reducing gas by at least partially reacting with the reducing gas, in particular natural gas and/or coal, is admixed to the reducing gas fed to the reduction stage and/or pre-heating stage, wherein no combustion takes place. The advantages of this process are that sticking is avoided, as mentioned above. In the following, the invention will be explained in more detail with reference to the drawings, wherein Figs. 1 to 3 and 9 each show an embodiment of an inventive process in a block diagram, Figs. 4 and 5 each show a preferred embodiment of the processes represented in Figs. 2 and 3, respectively, in a block diagram and Figs. 6 to 8 show an enlarged detail of a preferred embodiment in diagrammatic representation. Fig. 1 shows three fluidized-bed reactors, 1 to 3, subsequently connected in series, wherein iron-oxide-containing material, such as fine ore, via an ore feed duct 4 is fed to the first fluidized-bed reactor, 1, in which in a pre-heating stage 5 pre-heating of the fine ore and, optionally, pre-reduction talte place, and subsequently via conveying ducts 6 is conducted from fluidized-bed reactor 1 to fluidized-bed reactors 2, 3. In fluidized-bed reactor 2, pre- WE CLAIM: 1. A fluidized-bed process for gas reduction of particulate iron oxide- containing ores, the process comprising the steps of: preheating, and also optionally pre-reducing the ore in the presence of a reducing gas produced from coal in a first fluidized-bed reactor designed as a pre-heating stage; then reducing the preheated ore to sponge iron in the presence of a reducing gas produced from coal in a reduction stage comprising at least one further fluidized-bed reactor; conducting reducing gas for the reduction step to the reduction stage via a first feed duct; conducting reducing gas for the preheating step from the reduction stage to the pre-heating stage via a second feed duct; maintaining the fluidized beds at a pressure of heating the reducing gas fed to the reduction stage and/or pre-heating stage by combustion together with oxygen and/or air, of a quantity of combustible material; independently controlling the composition and/or temperature of the reducing gas provided to the fluidized-bed stages. 2. A process as claimed in claim 1, wherein a portion of the gas fed to the reducing stage and/or the pre-heating stage is used as the combustible material. 3. A process as claimed in claim 1, wherein a portion of the export gas is used as the combustible material. 4. A process as claimed in claim 1, wherein a portion of a gas employed for cooling the final fmidized-bed of the reduction stage is used as the combustible material. 5. A process as claimed in claim 1, further including the step of: scrubbing a portion of the reducing-gas provided to the reduction stage and/or the pre-beating stage, or the export gas or gas used for coding the final fluidized bed of the reduction stage; and using the scrubbed gas as the combustible material. 6. A process as claimed in claim 1, wherein an externally supplied gas and/or a solid fuel and/or a liquid fuel is used as the combustible material. 7. A process as claimed claim 1, wherein reducing gas and/or export gas and/or cooling gas is used as the combustible material, together with an externally-supplied combustible hydrocarbon-based fuel in gaseous and/or solid and/or liquid form. 8. A process as claimed in claim 1, further including the step of admixing natural gas and/or coal with the reducing gas fed to the reduction stage and/or the pre-heating stage to increase the proportion of reductants in the reducing gas. 9. A process as claimed in claim 1, wherein the combustion is done in a burner provided in a duct for providing the reducing-gas. 10. A process as claimed in claim 1, wherein the reducing-gas is provided to the fluidized-beds by respective feed ducts; and combustion is done in a combustion chamber separated from the reducing-gas feed ducts, an outlet of the combustion chamber being connected to an inlet of at least one of the feed ducts.

Documents:

318-mumnp-2003-cancelled pages(26-10-2006).pdf

318-mumnp-2003-claims(granted)-(26-10-2006).doc

318-mumnp-2003-claims(granted)-(26-10-2006).pdf

318-mumnp-2003-correspondence(26-10-2006).pdf

318-mumnp-2003-correspondence(ipo)-(19-10-2006).pdf

318-mumnp-2003-drawing(26-10-2006).pdf

318-mumnp-2003-form 18(21-7-2005).pdf

318-mumnp-2003-form 1a(19-3-2003).pdf

318-mumnp-2003-form 2(granted)-(26-10-2006).doc

318-mumnp-2003-form 2(granted)-(26-10-2006).pdf

318-mumnp-2003-form 3(20-4-2006).pdf

318-mumnp-2003-form 3(25-1-2006).pdf

318-mumnp-2003-form 4(19-4-2006).pdf

318-mumnp-2003-form 5(20-4-2005).pdf

318-mumnp-2003-form-pct-ipea-409(26-10-2006).pdf

318-mumnp-2003-form-pct-isa-210(6-11-2001).pdf

318-mumnp-2003-power of attorney(8-2-20003).pdf

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