System and method for reducing carbon dioxide emission in coke production process

Abstract

The invention relates to a system and a method for reducing carbon dioxide emission in a coke production process, after coke oven flue gas is desulfurized and denitrated, CO2 which is absorbed and resolved and hydrogen which is prepared by electrolyzed water are synthesized into methane, heat released in the methane synthesis process exchanges heat to generate water vapor which is recycled, the synthesized methane is supplied to a coke oven again for heating, and the coke oven is heated. The method has the beneficial effects that two-way circulation is achieved, energy is fully utilized, emission of coke oven flue gas CO2 to the atmosphere can be effectively reduced, CO2 in the coke oven flue gas can be captured and converted into methane fuel, the methane fuel is used as heating fuel of a coke oven, CO2 generated by combustion of the coke oven is not discharged, and the method is environment-friendly and energy-saving. Therefore, cyclic utilization of CO2 is realized, and green development is realized.

Description

Technical Field

[0001] The present invention relates to the technical fields of coking and environmental protection, and particularly to a system and method for reducing carbon dioxide emissions during coke production. Background Art

[0002] Carbon dioxide is one of the main greenhouse gases, and its emissions can cause the temperature on the earth's surface to rise, leading to global warming. This change can result in the frequent occurrence of extreme weather events, such as natural disasters like floods, droughts, and storms. The steel industry, as the industry with the largest carbon dioxide emissions, currently faces huge carbon reduction pressures and challenges.

[0003] Most steel enterprises use a mixed gas doped with blast furnace gas (also known as lean gas) and coke oven gas as fuel during the coking production process. Therefore, the flue gas discharged during the coking process contains a large amount of toxic gases and carbon dioxide. The current chemical pollutant emission standards only limit the emissions of pollutants such as NO X and SO2 in coke oven flue gas, and currently most enterprises only treat NO X and SO2 in the flue gas, while paying little attention to the emissions of CO2 in coke oven flue gas.

[0004] Chinese invention patent with publication number CN110141947A discloses "a coke oven flue gas carbon dioxide emission reduction process and system", which uses ammonia water to absorb CO2 in coke oven flue gas. After removing CO2, it is discharged through the coke oven flue gas outlet. The ammonium bicarbonate solution formed by the reaction of ammonia water and CO2 enters the CO2 desorption system. In the CO2 desorption system, the ammonium bicarbonate solution reacts with sulfuric acid in the reactor to form ammonium sulfate and dissolve it in the aqueous solution, while releasing CO2 gas; the released CO2 gas enters the carbonization chamber of the coal high-temperature carbonization system and reacts with the coal coke material in the carbonization chamber. The generated CO enters the subsequent gas collection and purification system along with the gas evolved during the carbonization process. This emission reduction method consumes the content of coke during the process of generating CO, affecting coke production and being unfavorable for coking production. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a system and method for reducing carbon dioxide emissions during coke production. The CO2 absorbed and desorbed after desulfurization and denitrification of coke oven flue gas and the hydrogen produced by electrolyzing water are synthesized into methane. The heat released during the process of synthesizing methane is used to generate steam through heat exchange and recycled again. The synthesized methane is provided to the coke oven for heating again. The separated water after synthesizing methane is used for electrolyzing water to produce hydrogen again. Through two-way circulation, energy is fully utilized, which can effectively reduce the emission of CO2 in coke oven flue gas to the atmosphere, and can capture the CO2 in coke oven flue gas and convert it into methane fuel, which is used as the heating fuel for the coke oven. The CO2 generated by the combustion of the coke oven does not discharge to the outside, thus realizing the recycling of CO2 and green development.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] A system for reducing carbon dioxide emissions during coke production, comprising a coke oven heating system, a flue gas desulfurization and denitrification system, a CO2 absorption and desorption system, a methane synthesis system, a methane storage system, an electrolytic water hydrogen production system, a hydrogen storage system, a methane storage system, and a separated water purification system. The flue gas outlet of the coke oven heating system is sequentially connected to the flue gas desulfurization and denitrification system and the CO2 absorption and desorption system through pipelines; the electrolytic water hydrogen production system is connected to the hydrogen storage system through a pipeline; the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system are respectively connected to the methane synthesis system through pipelines. The methane outlet of the methane synthesis system is connected to the coke oven heating system through the methane storage system, and the separated water outlet of the methane synthesis system is connected to the electrolytic water hydrogen production system through the separated water purification system;

[0008] The methane synthesis system includes a methanation inlet tower heat exchanger, a methanation reactor, a waste heat boiler, a circulating water heat exchanger, and a gas-liquid separator. The methanation inlet tower heat exchanger is sequentially connected to the methanation reactor, the waste heat boiler, the circulating water heat exchanger, and the gas-liquid separator through pipelines. The gas inlet of the methanation inlet tower heat exchanger is connected to the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system; the methane outlet of the gas-liquid separator is connected to the methane storage system through a pipeline, and the separated water outlet is connected to the separated water purification system through a pipeline.

[0009] Furthermore, the system for reducing carbon dioxide emissions during coke production further includes a wind power / solar power generation system and an energy storage system. The power supply outlet of the wind power / solar power generation system is divided into two paths, one path is connected to the power supply inlet of the electrolytic water hydrogen production system, and the other path is connected to the power supply inlet of the energy storage system; the power supply outlet of the energy storage system is connected to the power supply inlet of the electrolytic water hydrogen production system.

[0010] Furthermore, the remaining flue gas of the CO2 absorption and desorption system is discharged through a chimney after passing through a dust collector.

[0011] Furthermore, the hydrogen storage system is provided with a hydrogen balloon tank for buffer storage of the hydrogen coming from the electrolytic water hydrogen production system.

[0012] Furthermore, the methane storage system is provided with a methane balloon tank for buffer storage of the methane coming from the methane synthesis system.

[0013] Furthermore, the chemical reaction formula in the methanation reactor is: CO2 + 4H2 → CH4 + 2H2O.

[0014] Furthermore, the separated water purification system adopts reverse osmosis + ion exchange to purify the separated water.

[0015] A method for reducing carbon dioxide emissions in a coke production process comprises the following steps:

[0016] 1) The coke oven flue gas generated by the coke oven heating system passes through the flue gas desulfurization and denitrification system to remove NO x After the removal of CO2 and SO2, it enters the CO2 absorption and analysis system to separate the CO2 in the coke oven flue gas. The separated CO2 enters the methane synthesis system through the carbon dioxide pipeline. The remaining flue gas after the removal of CO2 is dedusted by the dust collector and then discharged through the chimney;

[0017] 2) The wind power / photovoltaic power generation system converts wind energy or light energy into electrical energy, and a portion of the generated electrical energy is sent to the water electrolysis hydrogen production system for hydrogen production, and the other portion of the electrical energy is sent to the energy storage system for storage; when the amount of electricity directly delivered by the wind power / photovoltaic power generation system to the water electrolysis hydrogen production system is less than the set value, the electrical energy stored in the energy storage system is released and sent to the water electrolysis hydrogen production system, thereby achieving continuous and stable operation of the water electrolysis hydrogen production system;

[0018] 3) The water electrolysis hydrogen production system realizes water electrolysis hydrogen production through an electrolyzer, and purifies the hydrogen and sends it to the hydrogen storage system. The hydrogen storage system buffers and temporarily stores the purified hydrogen sent by the water electrolysis hydrogen production system, and then smoothly sends the purified hydrogen to the methane synthesis system;

[0019] 4) The hydrogen sent by the hydrogen storage system and the CO2 sent by the CO2 absorption and analysis system are mixed in the methanation inlet heat exchanger and then heated up. The heated mixed gas enters the methanation reactor. The reaction temperature of the methanation reactor is between 200 and 300 ° C and the pressure is 3MPa. A chemical reaction is carried out under the action of the catalyst Ni+Al2O3, and the reaction formula is CO2+4H2→CH4+2H2O, producing water and methane;

[0020] 5) The reaction of producing methane in the methanation reactor is an exothermic reaction. The generated methane and water mixture carries a large amount of heat. The methane and water are passed into the waste heat boiler for heat exchange. The waste heat boiler generates water vapor, which is recycled. The cooled methane and water mixture enters the circulating water heat exchanger for further cooling. The cooled methane and water mixture enters the gas-liquid separator for separation. The separated methane is sent to the methane storage system, and the separated water is sent to the separated water purification system.

[0021] 6) The methane storage system buffers and stores the methane delivered by the methane synthesis system, and then sends the methane to the coke oven heating system to prepare coke;

[0022] 7) The separated water purification system purifies the transported separated water by using the method of reverse osmosis + ion exchange. The physically and chemically purified separated water is transported to the electrolyzed water hydrogen production system for hydrogen production.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) Green electricity is used to produce green hydrogen, which is coupled with carbon dioxide separated from coke oven flue gas to produce methane. Methane is used as the heating fuel for the coke oven, enabling green and sustainable production of methane with no excess pollution emissions and improving the green production level of coking.

[0025] 2) The CO2 after methane combustion can be captured and reacted with the green hydrogen produced by green electricity to generate methane again. The methane is then sent back to the coke oven for heating, achieving the recycling of CO2 and increasing the reuse rate of CO2.

[0026] 3) The removal rate of CO2 in the coke oven flue gas is ≥85%, and the concentration of CO2 in the remaining flue gas can be reduced to below 50 PPM. The recycled CO2 is used to synthesize methane for coke oven heating, significantly reducing the external discharge of CO2, decreasing the CO2 in the discharged coke oven flue gas, reducing environmental pollution, and improving the ecological environment around the coke oven production.

[0027] 4) Coke oven gas is not used as the heating fuel, so that more coke oven gas can be used for the production of chemical products such as hydrogen, LNG, synthetic ammonia, methane, methanol, gasoline, blast furnace injection for steelmaking, power generation, etc., saving coke oven fuel resources, reducing the coke oven fuel cost, increasing the by-product volume of coke oven gas, and increasing the by-product income.

[0028] 5) The conversion rate of CO2 in the methanation reaction can reach more than 90%. The high CO2 conversion rate improves the utilization rate, produces fewer by-products, has a high methane cleanliness, and has a high thermal energy utilization rate for coke oven production and a high coke production rate.

[0029] 6) The heat released during the reaction of CO2 and hydrogen to produce methane is recycled without heat loss, achieving a high energy resource utilization rate. The generated methane is used for coke oven production, and the water produced by the reaction is reused for hydrogen production, realizing two-way circular reuse, making more full use of resources, having a higher utilization rate, saving coke production resources, and saving coke production costs. Description of the Drawings

[0030] Figure 1 It is a system flow chart of a system for reducing carbon dioxide emissions during coke production according to the present invention.

[0031] Figure 2 It is a system flow chart of the methane synthesis system according to the present invention.

[0032] Figure 3 It is a system flow chart of the wind power / solar power generation system energy supply system according to the present invention. Detailed implementation manners

[0033] The following further describes the detailed implementation manners of the present invention in conjunction with the accompanying drawings:

[0034] As Figures 1 - 3 shown, a system for reducing carbon dioxide emissions during coke production includes a coke oven heating system, a flue gas desulfurization and denitrification system, a CO2 absorption and desorption system, a methane synthesis system, a methane storage system, an electrolytic water hydrogen production system, a hydrogen storage system, a methane storage system, and a separated water purification system. The flue gas outlet of the coke oven heating system is sequentially connected to the flue gas desulfurization and denitrification system and the CO2 absorption and desorption system through pipelines; the electrolytic water hydrogen production system is connected to the hydrogen storage system through a pipeline; the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system are respectively connected to the methane synthesis system through pipelines. The methane outlet of the methane synthesis system is connected to the coke oven heating system through the methane storage system, and the separated water outlet of the methane synthesis system is connected to the electrolytic water hydrogen production system through the separated water purification system;

[0035] The methane synthesis system includes a methanation inlet tower heat exchanger, a methanation reactor, a waste heat boiler, a circulating water heat exchanger, and a gas-liquid separator. The methanation inlet tower heat exchanger is sequentially connected to the methanation reactor, the waste heat boiler, the circulating water heat exchanger, and the gas-liquid separator through pipelines. The gas inlet of the methanation inlet tower heat exchanger is connected to the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system; the methane outlet of the gas-liquid separator is connected to the methane storage system through a pipeline, and the separated water outlet is connected to the separated water purification system through a pipeline.

[0036] As Figure 3 shown, further, the system for reducing carbon dioxide emissions during coke production further includes a wind power / solar power generation system and an energy storage system. The power supply outlet of the wind power / solar power generation system is divided into two paths, one path is connected to the power supply inlet of the electrolytic water hydrogen production system, and the other path is connected to the power supply inlet of the energy storage system; the power supply outlet of the energy storage system is connected to the power supply inlet of the electrolytic water hydrogen production system.

[0037] Further, the remaining flue gas of the CO2 absorption and desorption system is discharged through a chimney after passing through a dust collector.

[0038] Further, the hydrogen storage system is provided with a hydrogen balloon tank for buffer storage of the hydrogen coming from the electrolytic water hydrogen production system.

[0039] Further, the methane storage system is provided with a methane balloon tank for buffer storage of the methane coming from the methane synthesis system.

[0040] Further, the chemical reaction formula in the methanation reactor is: CO2 + 4H2 → CH4 + 2H2O.

[0041] Further, the separated water purification system purifies the separated water by means of reverse osmosis + ion exchange.

[0042] As Figures 1 - 3 shown, a method for reducing carbon dioxide emissions during coke production includes the following steps:

[0043] 1) The coke oven flue gas generated after combustion in the coke oven heating system passes through the flue gas desulfurization and denitrification system. After removing NO x and SO2 in the coke oven flue gas, it enters the CO2 absorption and desorption system to separate CO2 in the coke oven flue gas. The separated CO2 enters the methane synthesis system through the carbon dioxide pipeline. The remaining flue gas after removing CO2 is dusted by the dust collector and then discharged through the chimney;

[0044] 2) The wind power / solar power generation system converts wind energy or light energy into electric energy. A part of the generated electric energy is sent to the electrolytic water hydrogen production system for hydrogen production, and the other part of the electric energy is sent to the energy storage system for storage; when the electric energy directly delivered by the wind power / solar power generation system to the electrolytic water hydrogen production system is less than the set value, the electric energy stored in the energy storage system is released and sent to the electrolytic water hydrogen production system to realize the continuous and stable operation of the electrolytic water hydrogen production system;

[0045] 3) The electrolytic water hydrogen production system realizes the electrolysis of water to produce hydrogen through the electrolytic cell, and after purifying the hydrogen, it is sent to the hydrogen storage system. After the hydrogen storage system buffers and temporarily stores the purified hydrogen sent by the electrolytic water hydrogen production system, it gently sends the purified hydrogen to the methane synthesis system;

[0046] 4) The hydrogen sent by the hydrogen storage system and the CO2 sent by the CO2 absorption and desorption system are mixed and heat-exchanged in the methanation inlet tower heat exchanger to increase the temperature. The heated mixed gas enters the methanation reactor. The reaction temperature of the methanation reactor is between 200 and 300 °C, and the pressure is 3 MPa; a chemical reaction takes place under the action of the Ni + Al2O3 catalyst, and the reaction formula is CO2 + 4H2 → CH4 + 2H2O, producing water and methane;

[0047] 5) The reaction of producing methane in the methanation reactor is an exothermic reaction. The mixture of methane and water produced carries a large amount of heat. The methane and water are passed into the waste heat boiler for heat exchange to heat the boiler to produce steam, and the steam is recycled. The cooled mixture of methane and water enters the circulating water heat exchanger to be cooled again. The further cooled mixture of methane and water enters the gas-liquid separator for separation. The separated methane is sent to the methane storage system, and the separated water is sent to the separated water purification system;

[0048] 6) The methane storage system buffers and stores the methane transported by the methane synthesis system, and then sends the methane to the coke oven heating system to prepare coke;

[0049] 7) The separated water purification system purifies the transported separated water by means of reverse osmosis + ion exchange. The separated water purified by the physical + chemical method is transported to the electrolytic water hydrogen production system for hydrogen production.

[0050] The present invention captures CO2 in the coke oven flue gas and converts it into methane fuel. Methane fuel is a low-carbon fuel. Using methane as the fuel for the coke oven heating system, the CO2 in the generated flue gas is recycled, which can significantly reduce the carbon emissions in the coking production process, thereby effectively reducing the CO2 emissions in the coke oven flue gas. The water generated during the production of methane is recycled for hydrogen production, achieving two-way recycling, with high resource utilization rate and full resource utilization.

[0051] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A system for reducing carbon dioxide emissions during coke production, comprising a coke oven heating system, a flue gas desulfurization and denitrification system, a CO2 absorption and desorption system, a methane synthesis system, a methane storage system, an electrolytic water hydrogen production system, a hydrogen storage system, a methane storage system, and a separated water purification system, characterized in that, The flue gas outlet of the coke oven heating system is connected to the flue gas desulfurization and denitrification system and the CO2 absorption and desorption system in sequence through pipelines; the electrolytic water hydrogen production system is connected to the hydrogen storage system through pipelines; the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system are respectively connected to the methane synthesis system through pipelines, the methane outlet of the methane synthesis system is connected to the coke oven heating system through the methane storage system, and the separated water outlet of the methane synthesis system is connected to the electrolytic water hydrogen production system through the separated water purification system; The methane synthesis system includes a methanation inlet tower heat exchanger, a methanation reactor, a waste heat boiler, a circulating water heat exchanger and a gas-liquid separator. The methanation inlet tower heat exchanger is connected to the methanation reactor, the waste heat boiler, the circulating water heat exchanger and the gas-liquid separator in sequence through pipelines. The gas inlet of the methanation inlet tower heat exchanger is connected to the CO2 outlet of the CO2 absorption and desorption system and the H2 outlet of the hydrogen storage system; the methane outlet of the gas-liquid separator is connected to the methane storage system through a pipeline, and the separated water outlet is connected to the separated water purification system through a pipeline.

2. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The system for reducing carbon dioxide emissions during the coke production process further includes a wind power / solar power generation system and an energy storage system. The power supply outlet of the wind power / solar power generation system is divided into two paths. One path is connected to the power supply inlet of the electrolytic water hydrogen production system, and the other path is connected to the power supply inlet of the energy storage system; the power supply outlet of the energy storage system is connected to the power supply inlet of the electrolytic water hydrogen production system.

3. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The remaining flue gas of the CO2 absorption and desorption system is discharged through a chimney after passing through a dust collector.

4. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The hydrogen storage system is provided with a hydrogen balloon tank to buffer and store the hydrogen from the electrolytic water hydrogen production system.

5. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The methane storage system is provided with a methane balloon tank to buffer and store the methane from the methane synthesis system.

6. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The chemical reaction formula in the methanation reactor is: CO2 + 4H2 → CH4 + 2H2O.

7. A system for reducing carbon dioxide emissions during coke production according to claim 1, characterized in that, The separated water purification system purifies the separated water by means of reverse osmosis + ion exchange.

8. A method for reducing carbon dioxide emissions during coke production, implemented based on the system for reducing carbon dioxide emissions during coking production described in claim 1, characterized in that, Including the following steps: 1) The coke oven flue gas generated after combustion in the coke oven heating system passes through the flue gas desulfurization and denitrification system. After removing NOx and SO2 in the coke oven flue gas, it enters the CO2 absorption and desorption system to separate CO2 in the coke oven flue gas. The separated CO2 enters the methane synthesis system through a carbon dioxide pipeline. The remaining flue gas after removing CO2 is discharged through a chimney after passing through a dust collector for dust removal; 2) The wind power / solar power generation system converts wind energy or solar energy into electrical energy. A part of the generated electrical energy is sent to the electrolytic water hydrogen production system for hydrogen production, and the other part of the electrical energy is sent to the energy storage system for storage; when the power directly supplied by the wind power / solar power generation system to the electrolytic water hydrogen production system is less than the set value, the electrical energy stored in the energy storage system is released and sent to the electrolytic water hydrogen production system to realize the continuous and stable operation of the electrolytic water hydrogen production system; 3) The electrolytic water hydrogen production system realizes the electrolysis of water to produce hydrogen through an electrolytic cell, purifies the hydrogen and sends it to the hydrogen storage system. After the hydrogen storage system buffers and temporarily stores the purified hydrogen sent by the electrolytic water hydrogen production system, it gently sends the purified hydrogen to the methane synthesis system; 4) The hydrogen delivered by the hydrogen storage system and the CO2 delivered by the CO2 absorption and desorption system are mixed and heat-exchanged in the methanation inlet tower heat exchanger, and the heated mixed gas enters the methanation reactor. The reaction temperature of the methanation reactor is between 200 and 300 °C, and the pressure is 3 MPa; a chemical reaction occurs under the action of the Ni + Al2O3 catalyst, and the reaction formula is CO2 + 4H2 → CH4 + 2H2O, producing water and methane; 5) The reaction of producing methane in the methanation reactor is an exothermic reaction. The mixture of methane and water produced carries a large amount of heat. The methane and water are passed into the waste heat boiler for heat exchange to heat the boiler to produce steam, and the steam is recycled. The cooled methane and water mixture enters the circulating water heat exchanger to be cooled again, and the further cooled methane and water mixture enters the gas-liquid separator for separation. The separated methane is sent to the methane storage system, and the separated water is sent to the separated water purification system; 6) The methane storage system buffers and stores the methane delivered by the methane synthesis system, and then sends the methane to the coke oven heating system to prepare coke; 7) The separated water purification system purifies the delivered separated water. By using the method of reverse osmosis + ion exchange, the physically and chemically purified separated water is transported to the electrolytic water hydrogen production system for hydrogen production.

Images