Treatment method of blast furnace tail gas

Abstract

The invention relates to a blast furnace tail gas treatment method. The method comprises the following steps: carrying out desulfurization and dechlorination treatment on tail gas generated by a total-oxygen blast furnace; carrying out decarburization treatment on the tail gas subjected to desulfurization and dechlorination treatment to obtain carbon monoxide gas and carbon dioxide gas; carbon monoxide obtained after decarburization treatment is supplied to a total-oxygen blast furnace, and urea or ammonium bicarbonate products are prepared from carbon dioxide gas obtained after decarburization treatment. According to the method, processes such as total-oxygen blast furnace, hydrogen production through water electrolysis, nitrogen production through air separation and ammonia synthesis are effectively coupled, and byproducts of the processes are effectively utilized, so that the method has remarkable economic benefits, the treatment and purification cost of the blast furnace tail gas is reduced, and near-zero-carbon production of steel is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of utilization of tail gas generated by an all-oxygen blast furnace, and specifically relates to a method for treating blast furnace tail gas. Background Technology

[0002] Ironmaking processes are mainly divided into two types: blast furnace ironmaking and non-blast furnace ironmaking. Non-blast furnace ironmaking includes direct reduction ironmaking and molten reduction ironmaking. Blast furnace ironmaking technology has the advantages of good economic indicators, simple process, large production capacity, and high labor productivity. Therefore, although this ironmaking technology has high carbon dioxide emissions, the iron produced by this technology still accounts for more than 95% of the world's total iron production.

[0003] Blast furnace ironmaking refers to the process where iron ore, coke, and flux (limestone) are charged into a blast furnace from the top. Preheated air (hot blast, mainly composed of nitrogen and oxygen) is blown in through tuyeres located at the bottom of the furnace. At high temperatures, the carbon in the coke (and sometimes auxiliary fuels such as pulverized coal, heavy oil, natural gas, or coke oven gas) burns with the oxygen in the blown air to produce carbon monoxide and hydrogen. As these gases rise within the furnace, they remove oxygen from the iron ore, thus reducing it to iron. The molten iron produced during blast furnace ironmaking is discharged from the taphole. Unreduced impurities in the iron ore combine with the flux, such as limestone, to form slag, which is discharged from the slag outlet. The generated gas is extracted from the top of the furnace, and after dust removal, it is used as fuel for hot blast stoves, heating furnaces, coke ovens, boilers, etc. During this process, nitrogen, which does not participate in the reaction, consumes a large amount of energy during its use in production. The gas used as fuel also carries a large amount of carbon, significantly increasing carbon dioxide emissions per ton of iron produced.

[0004] Due to the large number of blast furnaces in operation, the exhaust gas contains a large amount of inert gases that cannot be recovered with low energy consumption. In recent years, a process of circulating top gas from blast furnaces with full oxygen has been developed in order to achieve efficient carbon dioxide capture and utilization under full oxygen smelting conditions.

[0005] The all-oxygen blast furnace ironmaking process refers to a process in which, without fundamentally altering the blast furnace structure, the blast furnace blast is replaced with pure oxygen or a high-concentration oxygen-enriched gas. The byproduct gas, after purification and decarbonization, is returned to the blast furnace for the reduction reaction. This method of utilizing existing blast furnaces can reduce the resource waste associated with the dismantling of numerous existing blast furnaces. Furthermore, the reduction in inert gases in the gas makes carbon dioxide separation and removal easier. However, currently, the high costs of oxygen separation and decarbonization, coupled with the lack of specific uses for removed carbon dioxide leading to further cost increases, prevent it from achieving a cost advantage compared to conventional blast furnaces. Summary of the Invention

[0006] In order to solve all or some of the above problems, the present invention aims to provide a method for treating blast furnace tail gas. The present invention has significant economic benefits, reduces the cost of treating and purifying blast furnace tail gas, realizes near-zero carbon production of steel, and achieves effective utilization of the removed carbon dioxide.

[0007] According to one aspect of the present invention, a method for treating blast furnace exhaust gas is provided, comprising: Desulfurization and dechlorination treatment is carried out on the tail gas generated by the all-oxygen blast furnace; The exhaust gas that has undergone desulfurization and dechlorination is decarbonized to obtain carbon monoxide and carbon dioxide gas. The carbon monoxide obtained after decarburization is supplied to the all-oxygen blast furnace, and the carbon dioxide gas obtained after decarburization is used to produce urea or ammonium bicarbonate products.

[0008] Furthermore, the desulfurization and dechlorination treatment of the tail gas generated by the all-oxygen blast furnace specifically involves: using alkali spraying to dechlorinate the tail gas generated by the all-oxygen blast furnace, and then desulfurizing the dechlorinated gas.

[0009] Furthermore, after the desulfurization and dechlorination treatment of the tail gas generated by the all-oxygen blast furnace, the method further includes: using a compressor to pressurize the desulfurized and dechlorinated tail gas.

[0010] Furthermore, the step of using a compressor to pressurize the desulfurized and dechlorinated tail gas specifically involves using a compressor to pressurize the desulfurized and dechlorinated tail gas to 0.5-0.6 MPa.

[0011] Furthermore, the step of decarbonizing the tail gas after desulfurization and dechlorination to obtain carbon monoxide and carbon dioxide specifically involves decarbonizing the tail gas after pressurization to obtain carbon monoxide and carbon dioxide.

[0012] Furthermore, the step of supplying the carbon monoxide obtained after decarburization to the all-oxygen blast furnace, and the preparation of urea or ammonium bicarbonate products using the carbon dioxide gas obtained after decarburization, further includes: Hydrogen and oxygen are prepared by water electrolysis, and nitrogen and oxygen are obtained by air separation. The oxygen obtained by water electrolysis and air separation is supplied to the all-oxygen blast furnace. The carbon monoxide gas obtained after decarburization and the hydrogen gas produced by water electrolysis are used as a mixed gas and supplied to the all-oxygen blast furnace. Hydrogen obtained from water electrolysis and nitrogen obtained from air separation are mixed to produce ammonia; and urea or ammonium bicarbonate products are produced using ammonia and carbon dioxide gas obtained from decarbonization treatment.

[0013] Furthermore, the process of preparing hydrogen and oxygen using water electrolysis and obtaining nitrogen and oxygen using air separation, and supplying the oxygen obtained from water electrolysis and air separation to the all-oxygen blast furnace specifically involves: preparing hydrogen and oxygen using water electrolysis and obtaining nitrogen and oxygen using air separation, and supplying a portion of the oxygen obtained from water electrolysis and air separation to the all-oxygen blast furnace.

[0014] Furthermore, the step of supplying the carbon monoxide gas obtained after decarbonization and the hydrogen gas generated from water electrolysis as a mixed gas to the all-oxygen blast furnace specifically involves: taking a portion of the mixed gas and burning it in an oxygen-rich environment formed by the water electrolysis process and the oxygen obtained from the separation of air, so as to heat the remaining mixed gas to 800-1250°C through the combustion of part of the mixed gas and supply it to the all-oxygen blast furnace.

[0015] As can be seen from the above technical solution, the method for treating blast furnace tail gas provided by the present invention has the following beneficial effects: This invention effectively couples processes such as all-oxygen blast furnace, water electrolysis for hydrogen production, air separation for nitrogen production, and ammonia synthesis, and makes effective use of the by-products of each process. Therefore, the embodiments of this invention have significant economic benefits, reduce the cost of treating and purifying blast furnace tail gas, and achieve near-zero carbon production of steel. This invention avoids the waste of resources caused by large-scale demolition and construction; by producing fertilizer products, it realizes the effective utilization of the removed carbon dioxide, and can be perfectly coupled with green ammonia production to achieve carbon reduction, energy saving and cost optimization. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for treating blast furnace tail gas according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the implementation process of a method for treating blast furnace tail gas according to an embodiment of the present invention. Detailed Implementation

[0017] To better understand the purpose, structure, and function of this invention, a method for treating blast furnace tail gas according to the present invention will be described in further detail below with reference to the accompanying drawings.

[0018] The main components of the tail gas from existing blast furnace processes are carbon monoxide, nitrogen, and carbon dioxide. In contrast, the tail gas from an all-oxygen blast furnace mainly consists of carbon monoxide, carbon dioxide, and other small amounts of impurity gases, which primarily contain chlorine and sulfur. This invention focuses on the tail gas produced by an all-oxygen blast furnace.

[0019] The purpose of this invention is to develop an all-oxygen blast furnace production process and multi-product coupling technology to reduce carbon dioxide emissions, addressing the characteristics and current requirements of existing ironmaking processes. The methods of this invention are applicable to various scenarios, including new construction and utilization of existing blast furnaces with measures to reduce carbon dioxide emissions, and coupling processes such as ammonia synthesis using water electrolysis as a raw material. It is particularly suitable for situations where complete dismantling and adopting a new process would result in significant waste.

[0020] like Figure 1 , Figure 2 As shown, this invention illustrates a method for treating blast furnace tail gas according to an embodiment of the present invention, comprising the following steps: Step S001: Desulfurize and dechlorinate the tail gas generated by the all-oxygen blast furnace; Step S002: The tail gas after desulfurization and dechlorination is decarbonized to obtain carbon monoxide gas and carbon dioxide gas. Step S003: The carbon monoxide obtained after decarburization is supplied to the oxygen blast furnace, and the carbon dioxide gas obtained after decarburization is used to prepare urea or ammonium bicarbonate products.

[0021] For step S001, the desulfurization and dechlorination treatment of the tail gas generated by the all-oxygen blast furnace is specifically carried out by: using alkali spraying to dechlorinate the tail gas generated by the all-oxygen blast furnace, and then desulfurizing the gas after dechlorination treatment.

[0022] The specific desulfurization and dechlorination treatments are carried out in the purification facility. For example, the dechlorination treatment can be carried out by directly spraying alkali into the purification facility and purifying the tail gas. The desulfurization treatment can be carried out by dry hydrolysis with hydrogen sulfide removal, adsorption removal, or direct wet scrubbing removal. The desulfurization and dechlorination treatments here are existing, mature and directly applicable processes. In addition, the purification facility can also be used for dust removal treatment of blast furnace tail gas.

[0023] After desulfurization and dechlorination treatment, the remaining gas from the exhaust gas produced by the all-oxygen blast furnace is mainly carbon monoxide and carbon dioxide.

[0024] After the tail gas generated by the all-oxygen blast furnace is desulfurized and dechlorinated in step S001, the method of this embodiment of the invention further includes: using a compressor to pressurize the desulfurized and dechlorinated tail gas.

[0025] The exhaust gas from an all-oxygen blast furnace has a pressure of approximately 0.2-0.3 MPa. The purpose of pressurization at this point is to compensate for losses caused by system resistance. In practice, pressurization is achieved, for example, through a recirculating gas pressurization compressor. Specifically, the process of using a compressor to pressurize the desulfurized and dechlorinated exhaust gas involves using a compressor to pressurize the desulfurized and dechlorinated exhaust gas to 0.5-0.6 MPa.

[0026] The pressurization process is set after the desulfurization and dechlorination process in step S001 and before the decarbonization process in step S002. Alternatively, the pressurization process can be set after the decarbonization process.

[0027] For the scheme where the pressurization treatment is set after the desulfurization and dechlorination treatment in step S001 and before the decarbonization treatment in step S002, step S002 performs decarbonization treatment on the tail gas after desulfurization and dechlorination treatment to obtain carbon monoxide gas and carbon dioxide gas. Specifically, the tail gas after pressurization treatment is decarbonized to obtain carbon monoxide gas and carbon dioxide gas.

[0028] For the decarbonization treatment in step S002, mature processes such as pressure swing adsorption, low-temperature methanol method, and amine method can be used. In specific implementation, the selection can be made after comprehensive evaluation based on the purity of carbon dioxide products required by subsequent processes and the economic and technical benefits of decarbonization treatment.

[0029] Step S003, which involves feeding the carbon monoxide obtained after decarburization into an oxygen-rich blast furnace and using the carbon dioxide gas obtained after decarburization to produce urea or ammonium bicarbonate products, further includes: Step S0031: Hydrogen and oxygen are prepared by water electrolysis, and nitrogen and oxygen are obtained by air separation. The oxygen obtained by water electrolysis and air separation is supplied to the all-oxygen blast furnace. Step S0032: The carbon monoxide gas obtained after decarburization and the hydrogen gas generated by water electrolysis are used as a mixed gas and supplied to the all-oxygen blast furnace; Step S0033: Mix the hydrogen obtained from the water electrolysis process and the nitrogen obtained from the air separation process to prepare ammonia; and use the ammonia and the carbon dioxide gas obtained from the decarbonization treatment to prepare urea or ammonium bicarbonate products.

[0030] Regarding step S0031, the oxygen obtained from the water electrolysis process and air separation can be divided into multiple portions according to the output, which are then used to supply the production of the full oxygen blast furnace, to provide an oxygen-enriched combustion environment to heat the mixture of carbon monoxide and hydrogen entering the full oxygen blast furnace, and the surplus oxygen can also be sold externally; in addition, the oxygen obtained from the water electrolysis process and air separation is pure oxygen or a high concentration of oxygen enrichment, for example, an oxygen concentration greater than or equal to 80%.

[0031] That is, step S0031 uses water electrolysis to prepare hydrogen and oxygen, and uses air separation to obtain nitrogen and oxygen, and supplies the oxygen obtained from water electrolysis and air separation to the full oxygen blast furnace. Specifically, hydrogen and oxygen are prepared using water electrolysis, and nitrogen and oxygen are obtained from air separation using an air separation unit. A portion of the oxygen obtained from water electrolysis and air separation is supplied to the full oxygen blast furnace.

[0032] Accordingly, step S0032: supplying the carbon monoxide gas obtained after decarburization and the hydrogen gas generated by water electrolysis as a mixed gas to the full oxygen blast furnace specifically involves: taking a portion of the mixed gas and burning it in an oxygen-rich environment formed by the water electrolysis process and the other portion of oxygen obtained by separating air, so as to heat the remaining mixed gas to 800-1250℃ through the combustion of part of the mixed gas and supply it to the full oxygen blast furnace.

[0033] The purpose of heating the mixed gas to 800-1250℃ and supplying it to the oxygen-rich blast furnace in this embodiment is to maintain the thermal balance within the furnace and reduce fuel consumption. The heating of the mixed gas employs both indirect heating and partial direct oxidation.

[0034] For the setting of burning a portion of the mixed gas to heat another portion of the mixed gas, the part of the mixed gas that is burned can also be set to be treated by a flue gas decarbonization system to obtain carbon dioxide gas and the remaining inert gas, so that the carbon dioxide gas can be used in the process of preparing urea or ammonium bicarbonate products in step S0033.

[0035] In step S0031, the electrolysis of water utilizes external power, and the separation of air utilizes an air separation unit.

[0036] In step S0033, hydrogen and nitrogen are reacted under high temperature and high pressure to generate ammonia. The synthesized ammonia is then used to react with carbon dioxide from decarbonization to produce urea or ammonium bicarbonate.

[0037] Regarding the decarbonization process in step S002, when producing ammonium bicarbonate using carbon dioxide gas, the decarbonization process in step S002 may employ, for example, a pressure swing adsorption process. When producing urea using carbon dioxide gas, since relatively pure carbon dioxide is required, the decarbonization process in step S002 may employ, for example, a low-temperature methanol process or an amine process.

[0038] In step S002, the mixed gas returned to the oxygen-rich blast furnace includes carbon monoxide and hydrogen. The purpose of the hydrogen is to reduce the consumption of coke and pulverized coal. In addition, in specific implementation, the carbon-hydrogen ratio of the reducing gas inside the blast furnace can be controlled by adjusting the proportion of hydrogen in the circulating gas entering the blast furnace.

[0039] The method for treating blast furnace tail gas according to embodiments of the present invention specifically includes purification facilities, a circulating gas booster compressor, a circulating gas decarbonization facility, a circulating gas heating system, a flue gas decarbonization system, an electrolysis water system, an air separation unit, a synthetic ammonia system, and urea and ammonium bicarbonate units, etc.

[0040] In this embodiment of the invention, oxygen produced by electrolysis of water and nitrogen production from air separation is used in blast furnace production, and surplus oxygen is sold externally; hydrogen produced by electrolysis of water and nitrogen produced by air separation are used to synthesize ammonia; carbon dioxide produced in blast furnace production and ammonia are combined to produce ammonium bicarbonate or urea; the fuel used for heating the production process can be carbon monoxide produced by blast furnace production or external fuel, and the carbon dioxide produced by combustion is purified and incorporated into the carbon dioxide produced in blast furnace production for the production of ammonium bicarbonate and urea.

[0041] This invention effectively couples processes such as all-oxygen blast furnace, water electrolysis for hydrogen production, air separation for nitrogen production, and ammonia synthesis, and makes effective use of the by-products of each process. At the same time, it utilizes carbon dioxide to obtain urea or ammonium bicarbonate products. Therefore, this invention has significant economic benefits, reduces the cost of treating and purifying blast furnace tail gas, and achieves near-zero carbon production of steel.

[0042] In this embodiment of the invention, the all-oxygen blast furnace body and raw material and fuel system do not need to be modified. Existing blast furnaces can be used, avoiding the waste of resources caused by large-scale demolition and construction. By producing fertilizer products, the effective utilization of carbon dioxide after removal is realized, and it can be perfectly coupled with green ammonia production to achieve carbon reduction, energy saving and cost optimization.

[0043] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for treating blast furnace tail gas, characterized in that, include Desulfurization and dechlorination treatment is carried out on the tail gas generated by the all-oxygen blast furnace; The exhaust gas that has undergone desulfurization and dechlorination is decarbonized to obtain carbon monoxide and carbon dioxide gas. The carbon monoxide obtained after decarburization is supplied to the all-oxygen blast furnace, and the carbon dioxide gas obtained after decarburization is used to produce urea or ammonium bicarbonate products.

2. The processing method according to claim 1, characterized in that, The desulfurization and dechlorination treatment of the tail gas generated by the all-oxygen blast furnace specifically involves: using alkali spraying to dechlorinate the tail gas generated by the all-oxygen blast furnace, and then desulfurizing the dechlorinated gas.

3. The processing method according to claim 1, characterized in that, After the desulfurization and dechlorination treatment of the tail gas generated by the all-oxygen blast furnace, the method further includes: using a compressor to pressurize the desulfurized and dechlorinated tail gas.

4. The processing method according to claim 3, characterized in that, The specific method of using a compressor to pressurize the desulfurized and dechlorinated exhaust gas is as follows: the compressor is used to pressurize the desulfurized and dechlorinated exhaust gas to 0.5-0.6 MPa.

5. The processing method according to claim 3, characterized in that, The process of decarbonizing the tail gas after desulfurization and dechlorination to obtain carbon monoxide and carbon dioxide gas specifically involves decarbonizing the tail gas after pressurization to obtain carbon monoxide and carbon dioxide gas.

6. The processing method according to claim 5, characterized in that, The step of supplying the carbon monoxide obtained after decarburization to the all-oxygen blast furnace, and the preparation of urea or ammonium bicarbonate products using the carbon dioxide gas obtained after decarburization, further includes: Hydrogen and oxygen are prepared by water electrolysis, and nitrogen and oxygen are obtained by air separation. The oxygen obtained by water electrolysis and air separation is supplied to the all-oxygen blast furnace. The carbon monoxide gas obtained after decarburization and the hydrogen gas produced by water electrolysis are used as a mixed gas and supplied to the all-oxygen blast furnace. Hydrogen obtained from water electrolysis and nitrogen obtained from air separation are mixed to produce ammonia; and urea or ammonium bicarbonate products are produced using ammonia and carbon dioxide gas obtained from decarbonization treatment.

7. The processing method according to claim 6, characterized in that, The process of preparing hydrogen and oxygen using water electrolysis and obtaining nitrogen and oxygen using air separation, and supplying the oxygen obtained from water electrolysis and air separation to the all-oxygen blast furnace, specifically involves: preparing hydrogen and oxygen using water electrolysis and obtaining nitrogen and oxygen using air separation, and supplying a portion of the oxygen obtained from water electrolysis and air separation to the all-oxygen blast furnace.

8. The processing method according to claim 7, characterized in that, Specifically, the method of supplying the carbon monoxide gas obtained after decarbonization and the hydrogen gas generated by water electrolysis as a mixed gas to the all-oxygen blast furnace involves: taking a portion of the mixed gas and burning it in an oxygen-rich environment formed by the water electrolysis process and the oxygen obtained by separating air, so as to heat the remaining mixed gas to 800-1250°C through the combustion of part of the mixed gas and supply it to the all-oxygen blast furnace.

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