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EP-4735150-A1 - STEEL MILL OFFGAS SEPARATION AND PURIFICATION

EP4735150A1EP 4735150 A1EP4735150 A1EP 4735150A1EP-4735150-A1

Abstract

A method comprising contacting an offgas stream comprising H2, H2O, CO, CO2, and at least one impurity comprising COS with at least one metal oxide to catalyze a reaction of H2O and COS to form H2S and CO2 in the offgas stream; contacting the offgas stream with an H2S-adsorbent to remove H2S from the offgas stream to produce a treated gas stream; and separating the treated gas stream to produce a carbon dioxide-enriched stream and a carbon dioxide-depleted stream.

Inventors

  • GOLDEN, TIMOTHY CHRISTOPHER
  • MOCSARI, JEFFREY CARL
  • ALIMOHAMMADI-ZANJANI, Mozhgan
  • WEIST, JR., EDWARD LANDIS
  • REMIEZOWICZ, Eryk
  • DEWING, ROGER ANTHONY
  • ZHANG, YU
  • GIRAUD, THIERRY
  • GRAHAM, DAVID ROSS
  • AMOTT, Toby

Assignees

  • Air Products and Chemicals, Inc.

Dates

Publication Date
20260506
Application Date
20240625

Claims (15)

  1. 1. A method comprising: contacting an offgas stream comprising H2, H2O, CO, CO2, and at least one impurity comprising COS with at least one metal oxide to catalyze a reaction of H2O and COS to form H2S and CO2 in the offgas stream; contacting the offgas stream with an H2S-adsorbent to remove H2S from the offgas stream to produce a treated gas stream; and separating the treated gas stream to produce a carbon dioxide-enriched stream and a carbon dioxide-depleted stream.
  2. 2. The method of claim 1 , wherein the at least one metal oxide comprises at least one of alumina, titania, Mn02, CuO, CaO, MgO, and NiO; wherein the H2S-adsorbent comprises at least one of zinc oxide, iron oxide, magnesium oxide, chromium oxide, cobalt oxide, copper oxide, manganese oxide and activated carbon; and wherein the at least one impurity further comprises H2S, SOx, NOx, HCN, NH3, and/or BTEX.
  3. 3. The method of claim 2, further comprising contacting the offgas stream with an HCN hydrolysis catalyst to catalyze a reaction of HCN and H2O to form NH3 and CO in the offgas stream.
  4. 4. The method of claim 1 , wherein the absolute value of the total concentration of water in the offgas stream minus the total concentration of water in the treated gas stream is less than 500 ppmv; and wherein the absolute value of the total concentration of oxygen in the offgas stream minus the total concentration of oxygen in the treated gas stream is less than 500 ppmv .
  5. 5. The method of claim 1 , further comprising contacting the treated offgas stream with a water gas shift catalyst prior to separation to produce carbon dioxide-enriched stream and the carbon dioxide-depleted stream.
  6. 6. The method of claim 1 , wherein the offgas stream has a temperature ranging from 50 to 300 °C when contacted with the at least one metal oxide.
  7. 7. The method of claim 1 , wherein a pretreating adsorbent comprises the at least one metal oxide and the H2S-adsorbent.
  8. 8. The method of claim 1 , further comprising: separating the carbon dioxide-depleted stream or a stream derived from the carbon dioxide-depleted stream to produce a hydrogen product stream and a hydrogen- depleted tail gas stream; contacting the carbon dioxide-enriched stream with a dehydrating adsorbent to produce a dry carbon dioxide product and a spent dehydrating adsorbent; and regenerating the spent dehydrating adsorbent with a regeneration gas stream to produce the dehydrating adsorbent and a spent regeneration gas stream; wherein the regeneration gas stream comprises at least a portion of the hydrogen- depleted tail gas stream or a stream derived from the hydrogen-depleted tail gas stream.
  9. 9. The method of claim 8, further comprising recycling at least a portion of the hydrogen product stream to a blast furnace; wherein the hydrogen product stream has a purity ranging 50% to 95%.
  10. 10. The method of claim 8, further comprising separating a carbon monoxide product from the carbon dioxide-depleted stream prior to separating the carbon dioxide-depleted stream or a stream derived from the carbon dioxide-depleted stream to produce a hydrogen product stream and a hydrogen-depleted tail gas stream; and removing oxygen from the carbon dioxide-depleted stream prior to separating the carbon monoxide product from the carbon dioxide-depleted stream.
  11. 11. The method of claim 8, further comprising separating the hydrogen-depleted tail gas stream by selective permeation prior to regenerating the spent dehydrating adsorbent to produce a hydrogen-enriched permeate stream and a hydrogen-depleted retentate stream; and combining the hydrogen-enriched permeate stream with the offgas stream, wherein the regeneration gas stream comprises at least a portion of the hydrogen- depleted retentate stream.
  12. 12. The method of claim 8, wherein the dehydrating adsorbent also removes NH3 and BTEX from the carbon dioxide-enriched stream.
  13. 13. The method of claim 8, further comprising reacting the spent regeneration gas stream with an oxidant to produce a vent stream; wherein the vent stream comprises at least 85% N2 by volume.
  14. 14. A method comprising: contacting an offgas stream comprising H2, H2O, CO, CO2, and at least one impurity comprising COS with at least one metal oxide to catalyze a reaction of H2O and COS to form H2S and CO2 in the offgas stream; separating the offgas stream to produce a carbon dioxide-enriched stream and a carbon dioxide-depleted stream; contacting the carbon dioxide-enriched stream with an H2S-adsorbent to remove H2S from the carbon dioxide-enriched stream.
  15. 15. The method of claim 14 further comprising: separating the carbon dioxide-depleted stream or a stream derived from the carbon dioxide-depleted stream to produce a hydrogen product stream and a hydrogen- depleted tail gas stream.

Description

STEEL MILL OFFGAS SEPARATION AND PURIFICATION CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Non-Provisional Application 18/216,179 which was filed June 29, 2023 and is incorporated herein by reference. BACKGROUND [0002] The iron- and steel-making industries are a major emitter of CO2, responsible for around 6% of global emissions. Typically, iron and steel production involve several carbonintensive processes such as production of coke in coke ovens, production of pig iron in blast furnaces, and production of steel in basic oxygen furnaces. Each process produces an offgas with a CO2 component that may be captured, however each type of off-gas has a different composition, requiring a flexible pretreatment and separation process. BRIEF DESCRIPTION OF THE DRAWINGS [0003] The drawings illustrate certain aspects of some of the embodiments of the present invention and should not be used to limit or define the invention. [0004] FIG. 1 is a schematic view depicting an embodiment of an offgas separation process according to one or more aspects of the present disclosure. [0005] FIG. 2 is a schematic view depicting a modification of Fig. 1 in which a membrane section is used to separate a hydrogen purification tail gas stream. [0006] FIG. 3 is a schematic view depicting a modification of Fig. 1 in which a treated offgas stream undergoes a water gas shift reaction prior to separation. [0007] FIG. 4 is a schematic view depicting an embodiment of an offgas separation process according to one or more aspects of the present disclosure in which a compressed offgas stream is hydrolyzed before pretreatment. [0008] FIG. 5 is a schematic view depicting a modification of Fig. 4 in which desulfurization takes place downstream of carbon dioxide removal. DETAILED DESCRIPTION [0009] The present disclosure is directed to methods for treating and separating an offgas stream into carbon dioxide, carbon monoxide, and/or hydrogen streams. The methods may be utilized for recovering valuable products from an offgas stream in the iron- and steel-making industries. The methods may include a pretreatment step in which impurities such as COS, H2S, SOx, NOx, HCN, and BTEX may be removed in one or more unit operations. The pretreatment step may hydrolyze the COS to form H2S prior to removing H2S. The methods may include a carbon dioxide removal step in which a carbon dioxide-enriched stream may be produced by adsorption or absorption, which may require dehydration prior to sequestration. In some embodiments, the methods may include a carbon monoxide removal step in which a carbon monoxide-enriched stream may be produced by adsorption or cryogenic distillation. The methods may include a hydrogen purification step in which a hydrogen-enriched product stream may be produced by adsorption. The tail gas stream comprising waste gas from the hydrogen purification step may be used to regenerate the dehydration of the carbon dioxide stream. The method may comprise performing the carbon dioxide removal step after hydrolyzing the COS, wherein H2S may follow the carbon dioxide and may be removed from the carbon dioxide-enriched stream. [0010] Fig. 1 is a schematic view depicting an embodiment of an offgas separation process according to one or more aspects of the present disclosure. Process 1 separates offgas stream 102 to produce enriched CO2, CO, and H2 streams. Offgas stream 102 may comprise blast furnace gas (BFG), basic oxygen furnace gas (BOFG), coke over gas (COG), or any combination of the three. All three sources of offgas may comprise CO, CO2, H2, and N2. BFG may be relatively rich in N2, BOFG may be relatively rich in CO, and COG may be relatively rich in H2. The compositions of the offgas may vary over time, either by variation in the process and/or variation in the relative amounts of BFG, BOFG, and COG. Offgas stream 102 may first enter particle removal section 110 in which waste stream 112 comprising solid particles may be removed from offgas stream 102, yielding scrubbed offgas stream 114. The solid particles may negatively impact downstream equipment such as compressors and/or adsorption vessels. Particle removal section 110 may include a dry scrubber (cyclone separator), a wet scrubber, and an electrostatic precipitator (ESP) in any combination and order. [0011] Scrubbed offgas stream 114 may then be compressed if necessary for downstream processing in compressor K1. Compressor K1 may comprise multiple compressors in series or compressors with multiple stages as required to most efficiently compress scrubbed offgas stream 114 and produce compressed offgas stream 116. Water knockout stream 118 may be produced by compressor K1 comprising sulfur and nitrogen oxides. If the downsteam processing immediately following compressor K1 requires higher temperatures, for example ranging from 150 to 300 °C (300 to 570 °F), the final stage of compression may have a reduced cooling duty and/or a heater to bring