Polygeneration method of circulating IGCC with complete capture of carbon dioxide and recovery of flue gas water

Abstract

The present invention relates to a polygeneration method of a circulating IGCC for completely capturing carbon dioxide and recovering flue gas water. The present invention is a polygeneration method of carbon-containing raw materials, a power generation and polygeneration technology for clean utilization of carbon-containing materials, low carbon laying cost, high thermal efficiency, and recovery of flue gas water and recycling. It can be used as a public engineering center and synthesis gas supply center to provide nitrogen, oxygen, steam (different grades), CO, H 2 , carbonyl synthesis gas (CO and H 2 The present invention realizes polygeneration, high efficiency, flue gas water circulation, CO by rationally combining and configuring technologies and equipment such as air separation, gasification, conversion, desulfurization and decarbonization, membrane separation, PSA, gas turbine, steam heating furnace, steam turbine, ammonia synthesis, and efficient flue gas water recovery. 2 Highly efficient capture and complete recovery of sulfur-containing gases without generating NO X Gas, no pollution.

Description

Technical Field

[0001] The invention relates to a polygeneration method of a circulating IGCC for completely capturing carbon dioxide and recovering flue gas water. Background Art

[0002] The greenhouse effect caused by greenhouse gas emissions such as CO2 has led to a rapid rise in global temperatures (on a century scale), posing a major threat to the ecology and human survival. At the same time, the energy required for economic and social development continues to grow. In the foreseeable 20 years, carbon-containing raw materials will still be the main energy source. In my country, based on the resource endowment characteristics of rich coal, poor oil and little gas, the use of coal still has a guarantee and basic status.

[0003] There are two main ways to use coal as thermal coal: using supercritical boilers for power generation or using integrated gasification combined cycle power generation systems (IGCC), among which supercritical boiler power generation is the mainstream application. In the existing thermal power generation technology, carbon-containing raw materials are directly burned in the boiler, and flue gas treatment includes dust removal, desulfurization, and denitrification, which is the back-end treatment; the main gases in the flue gas are nitrogen, water vapor, CO2, oxygen, SO2, and NOx. The CO2 content in the flue gas is about 15%, the CO2 concentration is low, and the capture cost is high; because the flue gas contains trace amounts of SO2, in order to avoid dew point corrosion, the flue gas emission temperature is relatively high (usually above 130°C). In the existing IGCC power generation technology, carbon-containing raw materials are gasified to generate synthesis gas. After dust removal, desulfurization and decarbonization, the synthesis gas enters the gas turbine. The gas turbine uses air and synthesis gas to burn and generate electricity. The exhaust gas is directly discharged after recovering the waste heat and undergoing denitrification treatment. The exhaust gas temperature is about 120°C. The existing IGCC performs desulfurization and dust removal at the front end of combustion power generation. In the desulfurization and purification process, some CO2 can be captured. The concentration of captured CO2 is relatively high, but the CO in the synthesis gas is burned in the gas turbine to generate CO2, which becomes one of the main components of the flue gas. There is also nitrogen, trace amounts of oxygen, and NOx in the flue gas. To summarize the above, the main problems with existing thermal power generation and IGCC power generation are: low CO2 concentration in flue gas (no more than 20%), high capture cost; and the introduction of air, which inevitably produces NO in combustion. X ; The flue gas contains sulfur. In order to avoid dew point corrosion, the flue gas emission temperature is mostly above 110°C, and a large amount of low-level waste heat cannot be recovered.

[0004] In order to solve the above problems, CN113072422A discloses a multi-generation system based on IGCC, in which the oxygen outlet of the air separation system is divided into two routes, one of which is connected to the inlet of the gasifier, and the other is connected to the oxygen output pipeline, the argon outlet of the air separation system is connected to the argon output pipeline, and the nitrogen outlet of the air separation system is connected to the inlet of the synthetic ammonia system; the carbon-containing fuel pipeline is connected to the inlet of the gasifier, the synthetic gas outlet of the gasifier is connected to the heat release side inlet of the heat exchanger, the heat release side outlet of the heat exchanger is connected to the inlet of the conversion system and the inlet of the productization system, the outlet of the conversion system is connected to the inlet of the hydrogen and carbon dioxide separation system, the hydrogen outlet of the hydrogen and carbon dioxide separation system is connected to the inlet of the productization system and the inlet of the synthetic ammonia system, the system can realize the diversification of IGCC system products, but the overall energy utilization rate is low. The fuel of the combustion engine in CN113072422A is synthesis gas (mainly CO+H2). CO2 is mixed with water in the flue gas after combustion. The flue gas is directly discharged through a chimney. CO2 is not easy to capture, and the water consumption is large. At the same time, NOx is emitted, which is easy to cause harm to the environment. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a multi-generation method of a circulating IGCC for completely capturing carbon dioxide and recovering flue gas water in response to the current status of the prior art. The method can achieve complete capture of carbon dioxide, recover a large amount of low-level waste heat, and recover water vapor in the flue gas, thereby realizing water circulation in the entire process, saving water resources, and at the same time allowing high-purity gas to be used for multiple purposes.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A polygeneration method of a circulating IGCC for completely capturing carbon dioxide and recovering flue gas water, characterized by comprising the following steps:

[0008] (1) The carbon-containing raw materials and the oxygen provided by the air separation unit enter the gasifier at a set mass ratio of 0.5 to 2.5 for gasification reaction, converting the carbon-containing raw materials into synthesis gas with H2 and CO as the main components;

[0009] (2) According to the difference in the properties of carbon-containing raw materials, the reaction temperature in the gasifier ranges from 1000 to 1700°C; the outlet fuel gas of the gasifier enters the waste heat boiler to recover the heat in the high-temperature fuel gas and use it to produce steam. The temperature of the synthesis gas after heat recovery is reduced to 130 to 200°C depending on the sulfur content;

[0010] (3) After heat recovery, the fuel gas enters the desulfurization unit for desulfurization. The sulfur content of the fuel gas after desulfurization is reduced to below 1ppmv. The sulfur-rich gas released by the desulfurization unit is desulfurized and recovered by the unit. The fuel gas enters the membrane separation unit to separate 90% to 95% of hydrogen. The separated hydrogen enters the PSA unit for further hydrogen purification and is used as fuel gas for the hydrogen engine. The H2 content of the PSA unit is 5% to 20%. The tail gas used as fuel gas for the steam superheater;

[0011] (4) After hydrogen is separated from the synthesis gas by the membrane separation unit, the remaining gas, mainly CO and CO2, enters the conversion unit for CO conversion reaction, converting CO into H2 with a conversion rate of more than 99%; this reaction is an exothermic reaction, and the heat released during the reaction is used to produce steam and preheat boiler water;

[0012] (5) The fuel gas at the outlet of the conversion unit mainly contains H2 and CO2. The fuel gas enters the decarbonization unit to remove CO2. The removed high-purity CO2 is captured and used for other purposes. The remaining H2 is combined with the H2 produced by the PSA unit and enters the hydrogen engine for combustion and power generation.

[0013] (6) After H2 is burned with oxygen from the air separation unit 2 in the hydrogen engine 10, flue gas water with a temperature of 400-550°C is generated, which enters the waste heat boiler for heat recovery to generate steam; after the heat is recovered, the flue gas temperature drops to about 100°C and enters the high-efficiency flue gas water recovery equipment (also low-level heat recovery equipment) for water recovery. The recovered water is used as boiler water and enters the gasification, conversion, and HRSG steam generation systems for recycling. The exhaust gas temperature is below 60°C;

[0014] (7) Part of the saturated steam generated by the waste heat boiler, conversion unit, and waste heat recovery unit enters the steam superheater for superheating. The fuel of the superheater comes from the exhaust gas discharged by the PSA unit; the superheated steam enters the steam turbine for power generation.

[0015] Preferably, in step (4), the gas composition before entering the conversion unit is mainly CO, and this part of the gas can be removed without conversion and only CO2 can be obtained to obtain high-purity CO.

[0016] Preferably, in step (5), H2 is combusted in the hydrogen engine 10 with oxygen from the air separation unit and CO2 to generate flue gas water with a temperature of 400-550°C.

[0017] Preferably, the H2 produced by the PSA unit is further purified to obtain high-purity H2 above the product gas battery grade; the H2 produced by the PSA unit is synthesized with ammonia by the nitrogen produced as a by-product of the air separation unit to obtain the product NH3.

[0018] Preferably, high-purity CO is obtained through an auxiliary decarbonization unit, and this gas is used as a raw gas for carbonyl synthesis.

[0019] Preferably, the desulfurization unit, decarbonization unit and auxiliary decarbonization unit are process-integrated for independent absorption, but the desulfurization solvent regeneration and utilities including refrigeration are shared.

[0020] In the present invention, the method of desulfurization and decarbonization is:

[0021] 1) Use low-temperature methanol washing method to perform desulfurization and decarbonization respectively; or,

[0022] 2) Desulfurization and decarbonization by MDEA method; or,

[0023] 3) MEDA method is used for desulfurization and PSA method is used for decarbonization.

[0024] In each process of the IGCC of the present invention, desulfurization is performed first, and non-sulfur-resistant conversion is adopted, and then decarbonization is performed. After desulfurization, the material grade of subsequent equipment and pipelines can be greatly reduced, and non-sulfur-resistant materials can be adopted, and the investment in equipment and pipelines is greatly reduced; the non-sulfur-resistant conversion catalyst is cheaper, which is conducive to reducing investment; in addition, the non-sulfur-resistant conversion catalyst has a high active temperature and can produce higher-grade steam (steam above 10.0MPa); in the IGCC, the gas engine adopts hydrogen as fuel, and pure oxygen can be added with CO2 for combustion, and the existing gas turbine is fully applicable, and the main components of the combustion flue gas are CO2 and H2O; in the IGCC, hydrogen is produced by combining membrane separation and pressure swing adsorption with conversion.

[0025] The present invention adopts a high-efficiency flue gas water recovery (waste heat utilization) unit to recover water in the flue gas, and the flue gas temperature is reduced from more than 120°C in the prior art to 50-60°C, and the thermal efficiency of the entire process is high; the high-efficiency flue gas recovery can use desalted water, or 10-20°C cooling capacity of air separation, or desulfurization and decarbonization (such as low-temperature methanol washing technology) cooling capacity, or heat pipe technology to recover low-level waste heat; the full circulation of water in the flue gas is realized, and the water in the flue gas can be used as conversion reaction raw material (water) and boiler water, and the water consumption of the entire IGCC polygeneration process is greatly reduced;

[0026] The method of the present invention can produce steam of various grades commonly used in factories, including 10.0MPag, 4.0MPag, 1.0MPag, 0.3-0.5MPag and the like.

[0027] Compared with the prior art, the advantages of the present invention are: the present invention is a polygeneration method for carbon-containing raw materials, is a power generation and polygeneration technology with clean utilization of carbon-containing materials, low carbon laying cost, high thermal efficiency, and recovery of flue gas water and recycling. It can be used as a public engineering center and synthesis gas supply center to provide nitrogen, oxygen, steam (different grades), CO, H2, carbonyl synthesis gas (the proportion of CO and H2 can be adjusted as needed), and electricity.

[0028] The implementation idea of ​​the present invention in the process flow is: the synthesis gas produced by gasification is first desulfurized, and the desulfurized synthesis gas mainly contains: CO, H2, CO2, and then the characteristics of membrane separation are used to separate hydrogen from the synthesis gas, so as to prepare for the next step of hydrogen purification and CO purification; PSA is used for further hydrogen purification, and the purified hydrogen can be used for gas turbines or for synthetic ammonia and high-purity hydrogen; CO and CO2 gases after membrane separation can obtain high-purity CO after deCO2 removal, and can also be subjected to non-sulfur-resistant conversion to produce hydrogen and produce steam as a by-product; water in the flue gas of the gas turbine can be recycled as boiler water after recycling waste heat condensation, and PSA tail gas can be used as heating furnace fuel gas to heat saturated steam and drive steam turbines to generate electricity. That is, the present invention realizes polygeneration, high efficiency, flue gas water circulation, and CO2 efficient capture by reasonably combining and configuring technologies and equipment such as air separation, gasification, conversion, desulfurization and decarbonization, membrane separation, PSA, gas turbine, steam heating furnace, steam turbine, ammonia synthesis, and efficient flue gas water recovery. The present invention realizes the complete capture of CO2 and the complete recovery of sulfur-containing gas without generating NO. X Gas, no pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a process flow chart of an embodiment of the present invention;

[0030] Figure 2 It is a process flow chart of a comparative example of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings. Example

[0032] like Figure 1 As shown, the polygeneration method of the circulating IGCC for completely capturing carbon dioxide and recovering flue gas water in this embodiment is:

[0033] (1) Carbon-containing raw materials (coal, natural gas, biomass, petroleum coke, shale gas, residual oil, carbon-containing waste, carbon-containing substances, etc.) 1 and oxygen provided by the air separation unit 2 enter the gasifier 3 at a mass ratio of 0.5 to 2.5 for gasification reaction, converting the carbon-containing raw materials into synthesis gas with H2 and CO as the main components.

[0034] (2) According to the difference in the properties of carbon-containing raw materials, the reaction temperature in the gasifier ranges from 1000 to 1700°C. Therefore, the outlet fuel gas enters the waste heat boiler 9 to recover the heat in the high-temperature fuel gas and use it to produce steam. The temperature of the synthesis gas after heat recovery can be reduced to about 130 to 200°C depending on the sulfur content.

[0035] (3) After heat recovery, the fuel gas enters the desulfurization unit 4 for desulfurization, and the sulfur content of the fuel gas after desulfurization is reduced to below 1 ppmv. The sulfur-rich gas released by the desulfurization unit is desulfurized and recovered by the unit. The fuel gas enters the membrane separation unit 5 to separate 90-95% of hydrogen. The separated hydrogen enters the PSA unit 6 for further hydrogen purification and is used as the fuel gas of the hydrogen engine 10. The tail gas discharged by the PSA unit (H2 content is about 5-20%) is used as the fuel gas of the steam superheater 13.

[0036] (4) After hydrogen is separated from the synthesis gas by membrane separation 5, the remaining gas (mainly CO and CO2) enters the conversion unit 7 for CO conversion reaction (CO+H2O→CO2+H2), converting CO into H2 with a conversion rate of over 99%. This reaction is an exothermic reaction, and the heat released during the reaction is used to produce steam and preheat boiler water. The gas composition before entering the conversion unit is mainly CO. If only CO2 is removed without conversion, high-purity CO can be obtained.

[0037] (5) The fuel gas at the outlet of the conversion unit 7 mainly contains H2 and CO2. The fuel gas enters the decarbonization unit 8 to remove CO2. The removed high-purity CO2 can be captured for other purposes. The remaining H2, together with the H2 produced by the PSA unit 6, enters the hydrogen engine (gas turbine) 10 for combustion and power generation.

[0038] (6) The flue gas water generated by the combustion of H2 with oxygen (with CO2) from the air separation unit 2 in the hydrogen engine 10 has a temperature of about 400-550°C and enters the waste heat boiler (HRSG) 11 for heat recovery to generate steam. After the heat is recovered, the flue gas temperature drops to about 100°C and enters the high-efficiency flue gas water recovery equipment (also low-level heat recovery equipment) 12 for water recovery. The recovered water can be used as boiler water to enter the steam generation system such as gasification, conversion, HRSG, etc. for recycling, and the exhaust gas temperature is below 60°C.

[0039] (7) Part of the saturated steam generated by the waste heat boiler 9, the conversion unit 7, and the waste heat recovery unit 11 can enter the steam superheater 13 for superheating. The fuel of the superheater comes from the exhaust gas discharged from the PSA unit 6. The superheated steam enters the steam turbine 14 for power generation.

[0040] (8) The H2 produced by PSA unit 6 can be further purified to obtain high-purity H2 above the product gas cell grade.

[0041] (9) The H2 produced by PSA unit 6 can be synthesized with nitrogen produced as a by-product of air separation to obtain the product NH3.

[0042] (10) Through the auxiliary decarbonization unit 8-1, CO with higher purity can be obtained, and this gas can be used as the raw gas for carbonyl synthesis.

[0043] (11) The desulfurization unit 4, the decarbonization unit 8 and the auxiliary decarbonization unit 8-1 can be integrated in process. The absorption is independent, but the desulfurization solvent regeneration can be shared, and the public works including the cooling capacity can be shared.

[0044] In this embodiment, synthesis gas (H2+CO) is produced by gasification of carbon-containing raw materials (coal, natural gas, biomass, petroleum coke, shale gas, etc.). The synthesis gas (H2+CO) is completely converted into hydrogen by using unit technologies such as desulfurization, membrane separation, PSA, decarbonization, and conversion to carry out innovative combination of processes. The gas turbine uses hydrogen and oxygen for combustion (CO2 can be added to control the gas temperature), and the carbon dioxide is completely captured. A large amount of low-level waste heat is recovered, and water vapor in the flue gas is recovered, so that the whole process of water circulation is realized, saving a large amount of water resources. At the same time, high-purity gas has many uses. Hydrogen can be used for: (1) sending it to a hydrogen combustion engine for combustion and power generation. After the heat of the combustion engine flue gas is recovered, the water in the flue gas is recovered by an efficient flue gas water recovery unit; (2) further purifying the hydrogen to obtain high-purity hydrogen; (3) using hydrogen in the production process of chemicals such as ammonia synthesis. The steam generated by coal gasification, conversion, and HRSG is used for power generation. The whole system realizes energy recovery and utilization, full recovery and recycling of water, and full capture of CO2. This technology can achieve efficient and low-cost CO2 capture through unit combination and the use of hydrogen combustion engines through the cogeneration IGCC; through lower flue gas emission temperature (below 60°C), higher system thermal efficiency can be achieved, and water in the flue gas can be recovered for water recycling.

[0045] Comparative Example:

[0046] like Figure 2 As shown, this comparative example uses coal as raw material, and undergoes a gasification reaction with oxygen from air separation through a coal gasification unit to produce synthesis gas and steam; the synthesis gas enters a gas turbine for combustion and power generation after desulfurization; the high-temperature flue gas generated by the gas turbine is recovered through a waste heat boiler to produce steam, and enters a steam turbine together with the steam generated by coal gasification to generate electricity.

[0047] Using the same raw materials, production is carried out using the methods of this embodiment and the comparative example respectively, and the efficiency of the entire unit of the comparative example is about 43%; while this embodiment, while achieving power generation by recovering steam heat and synthesis gas heat, pays more attention to the separation and application of different products, realizes the capture of high-purity CO2 and the recycling of water in the entire unit, improves the quality of by-products and the utilization efficiency of water, and the efficiency of the entire unit can reach 50%-51%, which is significantly better than the efficiency of the comparative example.

Claims

1. A polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water, characterized in that The following steps are involved: (1) The carbon-containing raw materials and the oxygen provided by the air separation unit enter the gasifier at a set mass ratio of 0.5 to 2.5 for gasification reaction, converting the carbon-containing raw materials into synthesis gas with H2 and CO as the main components; (2) According to the difference in the properties of carbon-containing raw materials, the reaction temperature in the gasifier ranges from 1000 to 1700°C; the outlet fuel gas of the gasifier enters the waste heat boiler to recover the heat in the high-temperature fuel gas and use it to produce steam. The temperature of the synthesis gas after heat recovery is reduced to 130 to 200°C depending on the sulfur content; (3) After heat recovery, the fuel gas enters the desulfurization unit for desulfurization. The sulfur content of the fuel gas after desulfurization is reduced to below 1ppmv. The sulfur-rich gas released by the desulfurization unit is desulfurized and recovered by the unit. The fuel gas enters the membrane separation unit to separate 90% to 95% of hydrogen. The separated hydrogen enters the PSA unit for further hydrogen purification and is used as fuel gas for the hydrogen engine. The exhaust gas with a H2 content of 5% to 20% emitted by the PSA unit is used as fuel gas for the steam superheater. (4) After hydrogen is separated from the synthesis gas by the membrane separation unit, the remaining gas, mainly CO and CO2, enters the conversion unit for CO conversion reaction, converting CO into H2 with a conversion rate of more than 99%; this reaction is an exothermic reaction, and the heat released during the reaction is used to produce steam and preheat boiler water; (5) The fuel gas at the outlet of the conversion unit mainly contains H2 and CO2. The fuel gas enters the decarbonization unit to remove CO2. The removed high-purity CO2 is captured and used for other purposes. The remaining H2 is combined with the H2 produced by the PSA unit and enters the hydrogen engine for combustion and power generation. (6) After H2 is burned with oxygen from the air separation unit in the hydrogen engine, flue gas water with a temperature of 400 ~ 550 ° C is generated, which enters the waste heat boiler for heat recovery to generate steam; after the heat is recovered, the flue gas temperature drops to around 100 ° C, and enters the high-efficiency flue gas water recovery equipment for water recovery. The recovered water is used as boiler water and enters the gasification, conversion, and HRSG steam generation systems for recycling. The exhaust gas temperature is below 60 ° C; (7) Part of the saturated steam generated by the waste heat boiler, conversion unit, and waste heat recovery unit enters the steam superheater for superheating. The fuel of the superheater comes from the exhaust gas discharged by the PSA unit; the superheated steam enters the steam turbine for power generation.

2. The polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water according to claim 1, characterized in that: In step (5), H2 is combusted in the hydrogen engine with oxygen from the air separation unit and CO2 to generate flue gas water with a temperature of 400 to 550°C.

3. The polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water according to claim 1 or 2, characterized in that: The H2 produced by the PSA unit is further purified to obtain high-purity H2 above the gas battery grade. The H2 produced by the PSA unit is synthesized with ammonia by the nitrogen produced as a by-product of the air separation unit to obtain the product NH3.

4. The polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water according to claim 1 or 2, characterized in that: High-purity CO is obtained through the auxiliary decarbonization unit, and this gas is used as the raw gas for carbonyl synthesis.

5. The polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water according to claim 1 or 2, characterized in that: The desulfurization unit, decarbonization unit and auxiliary decarbonization unit are process-integrated for independent absorption, but the desulfurization solvent regeneration and utilities including cooling capacity are shared.

6. The polygeneration method of circulating IGCC for completely capturing carbon dioxide and recovering flue gas water according to claim 1, characterized in that: The methods of desulfurization and decarbonization are: 1) Use low-temperature methanol washing method to perform desulfurization and decarbonization respectively; or, 2) Desulfurization and decarbonization by MDEA method; or, 3) MEDA method is used for desulfurization and PSA method is used for decarbonization.

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