SOFC tail gas driven desulfurization and decarburization and carbon dioxide recovery system

Abstract

The application discloses a SOFC tail gas driven desulfurization and decarburization and carbon dioxide recovery system and belongs to the technical field of fuel cell tail gas treatment. The system comprises a SOFC stack, an input unit, an output unit, a pre-cooler, an absorption tower, a regeneration tower, a CO2 condensing unit and a lean-liquid and rich-liquid circulation supply assembly. The application realizes step-by-step utilization of SOFC high-temperature tail gas and low-energy-consumption operation of a desulfurization and decarburization process, and forms a complete energy closed loop of fuel purification and tail gas treatment.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a desulfurization, decarbonization, and carbon dioxide recovery system driven by SOFC exhaust gas. Background Technology

[0002] With the increasing maturity of solid oxide fuel cell (SOFC) power generation technology, the treatment and resource utilization of its high-temperature exhaust gas has become a key aspect of system integration design.

[0003] The cathode and anode exhaust gases emitted during SOFC stack operation reach temperatures exceeding 500°C, containing high-quality waste heat resources. Furthermore, the incompletely converted fuel components in the anode exhaust gas also have further utilization value. However, existing SOFC system exhaust gas treatment processes mostly employ simple waste heat recovery or direct combustion emissions, failing to deeply couple the thermal and chemical energy of the high-temperature exhaust gas with downstream separation processes. On the other hand, while the industrially mature chemical absorption desulfurization and decarbonization technology can effectively remove acidic components and recover CO2, its regeneration process has high energy consumption and requires a continuous external heat source, limiting its widespread application in distributed energy systems.

[0004] Therefore, designing a highly integrated desulfurization, decarbonization, and carbon dioxide recovery process system tailored to the characteristics of SOFC exhaust gas, to achieve efficient cascade utilization of high-temperature exhaust gas thermal energy, value recovery of unburned components in the exhaust gas, and low-energy capture of CO2, has become an important direction for technological development in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention relates to an SOFC tail gas driven desulfurization, decarbonization, and carbon dioxide recovery system. This system is simple and reliable, effectively solves the above-mentioned technical problems, and is suitable for widespread use. To achieve the above objectives, this invention employs the following technical solutions: A SOFC exhaust gas driven desulfurization, decarbonization, and carbon dioxide recovery system, including The SOFC stack has a cathode tail gas outlet and an anode tail gas outlet, which are used to output 500°C cathode tail gas and 500°C anode tail gas, respectively. The input unit is used to receive and distribute the following media into the system: 30°C cooling water, sulfur-containing fuel gas, 500°C cathode tail gas, and 500°C anode tail gas. The output unit is used to collect and export the following media discharged from the system: desulfurized and decarbonized fuel, water at 35°C, cathode tail gas at 120°C, and CO2 at 40°C. A precooler has its hot-side inlet connected to the input unit to receive 500°C anode tail gas and its cold-side inlet connected to the input unit to receive 30°C cooling water. The precooler is used to precool the 500°C high-temperature anode tail gas to 40°C using 30°C cooling water. The absorption tower has a fuel inlet and a rich liquid outlet at its lower part, and a purified fuel outlet and a lean liquid inlet at its upper part. The fuel inlet is connected to the input unit to receive sulfur-containing fuel gas, which flows from bottom to top within the absorption tower. The lean liquid inlet is connected to a lean-rich liquid circulation supply component to introduce 40°C lean amine liquid, which is sprayed from top to bottom within the absorption tower, coming into countercurrent contact with the sulfur-containing fuel gas and undergoing a gas-liquid phase mass transfer reaction to absorb acidic components from the sulfur-containing fuel gas. The purified fuel outlet of the absorption tower is connected to the output unit for discharging desulfurized and decarbonized fuel. The rich liquid outlet of the absorption tower is used to discharge amine liquid heated to 50°C after absorbing acidic components. The regeneration tower has a rich liquor inlet and a high-temperature CO2 outlet at the top, and a lean liquor outlet and a reboiler at the bottom. The rich liquor inlet is connected to a rich-lean-rich liquor circulation supply assembly to receive 110°C rich amine liquor, allowing it to flow downwards within the regeneration tower. The lean liquor outlet discharges lean amine liquor heated to 120°C after heating and desorption. The hot-side inlet of the reboiler is connected to the input unit to receive 500°C cathode tail gas, which is used to heat the amine liquor in the regeneration tower, causing it to boil and release 105°C CO2. The reboiler outlet discharges the cooled 120°C cathode tail gas and connects to the output unit. The high-temperature CO2 outlet of the regeneration tower discharges 105°C CO2. The CO2 condenser has a cold-side inlet connected to the input unit to receive 30°C cooling water, a cold-side outlet connected to the output unit to output cooling water that has absorbed heat and been heated to 35°C, and a hot-side inlet connected to the high-temperature CO2 outlet at the top of the regeneration tower. It is used to cool the 105°C CO2 that has been decomposed by the 30°C cooling water and separate the water, and output 40°C CO2. The lean and rich liquid circulation supply component is used to realize the closed-loop circulation of carbon-amine liquid between the absorption tower and the regeneration tower and the cascade utilization of heat.

[0006] Based on the above scheme and as a preferred embodiment of the above scheme: the lean and rich liquid circulation supply component includes The rich liquid transport path is provided with a first delivery pump and a first heat exchange channel of a lean-rich liquid heat exchanger. The inlet of the rich liquid transport path is connected to the rich liquid outlet at the bottom of the absorption tower, and is used to transport 50°C rich amine liquid to the lean-rich liquid heat exchanger via the first delivery pump to heat it to 110°C rich amine liquid. The outlet of the rich liquid transport path is connected to the rich liquid inlet of the regeneration tower, thereby introducing 110°C rich amine liquid into the regeneration tower. The lean liquor transport path includes a second delivery pump, a second heat exchange channel of a lean-rich liquor heat exchanger, and a lean liquor cooler. The inlet of the lean liquor transport path is connected to the lean liquor outlet at the bottom of the regeneration tower. It is used to sequentially send 120°C lean amine liquor into the second heat exchange channel of the lean-rich liquor heat exchanger via the second delivery pump to cool it to 70°C. Then, the 70°C lean amine liquor is sent to the lean liquor cooler for further cooling to 40°C. The outlet of the lean liquor transport path is connected to the lean liquor inlet at the top of the absorption tower to introduce the 40°C lean amine liquor into the absorption tower.

[0007] Based on the above scheme and as a preferred embodiment of the above scheme: the 40℃ CO2 discharged from the output unit is compressed and then transferred to a CO2 storage tank for storage, and the CO2 storage tank is connected to the output unit.

[0008] Based on the above scheme and as a preferred option, the desulfurized and decarbonized fuel discharged from the output unit is reintroduced into the SOFC stack as fuel input.

[0009] The outstanding and beneficial technical effects of this invention compared to the prior art are: This invention introduces the 500°C cathode tail gas discharged from the SOFC stack into the reboiler of the regeneration tower as a heat source for the desorption of carbon-rich amine liquid, avoiding the high energy consumption problem of traditional processes that rely on external steam or gas heating. At the same time, the 500°C anode tail gas is cooled to 40°C by heat exchange with 30°C cooling water in a precooler and output as 35°C water, realizing the cascade recovery of high-temperature waste heat and a significant improvement in the overall energy efficiency of the SOFC system.

[0010] This invention utilizes a lean-rich liquid heat exchanger to preheat a 50°C rich liquid to 110°C using a 120°C high-temperature lean liquid, which reduces both the heating load on the regeneration tower and the cooling burden on the lean liquid cooler. After two stages of cooling from 120°C to 70°C and then to 40°C, the lean liquid is returned to the absorption tower, ensuring full recovery of heat within the system and significantly reducing the operating costs of the desulfurization and decarbonization process.

[0011] This invention reintroduces the desulfurized and decarbonized fuel purified by the absorption tower into the SOFC stack as fuel input, realizing the resource reuse of fuel. It also condenses and dehydrates CO2, compresses and stores it, and connects it to the output unit, forming a complete process chain from tail gas treatment to carbon capture and storage.

[0012] This invention distributes 30°C cooling water uniformly to the precooler, lean liquid cooler, and CO2 condenser. After the three heat exchanges, the water is uniformly output as 35°C hot water. The cooling water system is simple and efficient, and the material flow direction and temperature of each unit are closely matched. The overall process design is compact. Attached Figure Description

[0013] Figure 1This is a schematic diagram of the system layout. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. However, the specific implementation methods and embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0015] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the appendix. Figure 1 The directions or positional relationships shown are for the purpose of describing the present invention only, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0016] In the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0017] To solve the above technical problems, such as Figure 1 As shown, this invention designs a SOFC exhaust gas-driven desulfurization, decarbonization, and carbon dioxide recovery system, including... SOFC stack 1 has a cathode tail gas outlet and an anode tail gas outlet, which are used to output 500°C cathode tail gas and 500°C anode tail gas, respectively. These are the cathode tail gas rich in heat and the anode tail gas containing unburned components discharged from the stack during the high-temperature operation of the solid oxide fuel cell. They provide two high-quality heat sources for the downstream desulfurization and decarbonization system. The cathode tail gas is used to drive regeneration energy consumption, and the anode tail gas recovers heat through pre-cooling, realizing the source utilization of waste heat from SOFC power generation.

[0018] Input unit 2 is used to receive and distribute the following media into the system: 30°C cooling water, sulfur-containing fuel gas, 500°C cathode tail gas, and 500°C anode tail gas, so as to realize the unified introduction and distribution management of multiple media, simplify the external interface of the system, and ensure that each unit can stably obtain the required media.

[0019] Output unit 3 is used to collect and export the following media discharged by the system: desulfurized and decarbonized fuel, 35°C water, 120°C cathode tail gas, and 40°C CO2, so as to realize the unified collection and external delivery of multiple products, which facilitates subsequent utilization or disposal and forms a complete input and output material balance.

[0020] The precooler 4 has its hot-side inlet connected to the input unit 2 to receive 500°C anode tail gas, and its cold-side inlet connected to the input unit 2 to receive 30°C cooling water. The precooler 4 is used to precool the 500°C high-temperature anode tail gas to 40°C using 30°C cooling water. It uses low-temperature cooling water to exchange heat with the high-temperature anode tail gas and recovers the sensible heat in the anode tail gas. On the one hand, it reduces the 500°C anode tail gas to 40°C, protecting downstream equipment and recovering heat; on the other hand, it produces 35°C hot water for external use, realizing the utilization of waste heat resources.

[0021] Absorption tower 5 has a fuel inlet and a rich liquid outlet at its lower part, and a purified fuel outlet and a lean liquid inlet at its upper part. The fuel inlet is connected to the input unit 2 to receive sulfur-containing fuel gas, allowing the sulfur-containing fuel gas to flow from bottom to top within the absorption tower 5. The lean liquid inlet is connected to a lean-rich liquid circulation supply assembly to introduce 40°C lean amine liquid, allowing the lean amine liquid to spray from top to bottom within the absorption tower 5, contacting the sulfur-containing fuel gas countercurrently and undergoing a gas-liquid phase mass transfer reaction to absorb the acidic components in the sulfur-containing fuel gas. The purified fuel outlet of the absorption tower 5 is connected to the output unit 3 for discharging desulfurized and decarbonized fuel. The rich liquid outlet of the absorption tower 5 is used to discharge the rich amine liquid, which has absorbed the acidic components and been heated to 50°C. By countercurrent contact between lean amine solution and sulfur-containing fuel gas, acidic components (sulfides, CO2) in the fuel gas are removed through chemical absorption reaction. The exothermic reaction raises the temperature of the solution, achieving efficient purification of sulfur-containing fuel gas and producing desulfurized and decarbonized fuel that can be used directly. At the same time, the absorbed acidic components are transferred to rich solution, providing conditions for subsequent regeneration.

[0022] The regeneration tower 6 has a rich liquor inlet and a high-temperature CO2 outlet at the top, and a lean liquor outlet and a reboiler at the bottom. The rich liquor inlet is connected to the rich-lean-rich liquor circulation supply assembly to receive 110°C rich amine liquor, allowing the rich amine liquor to flow from top to bottom within the regeneration tower 6. The lean liquor outlet is used to discharge the lean amine liquor, which has been heated to 120°C after desorption, thus regenerating the rich liquor and restoring its absorption capacity. Simultaneously, CO2 is desorbed from the liquid phase, forming a high-temperature CO2 gas stream sent to the post-processing stage. The hot-side inlet of the reboiler is connected to the input unit 2 to receive 500°C cathode tail gas for further processing. The amine hydrocarbon liquid in the regeneration tower 6 is heated by the 500℃ cathode tail gas to boil and decompose into 105℃ CO2. The outlet of the reboiler is used to discharge the cooled 120℃ cathode tail gas and is connected to the output unit 3. The high-temperature CO2 outlet of the regeneration tower 6 is used to discharge 105℃ CO2. The SOFC high-temperature cathode tail gas is used as a heat source to heat the amine hydrocarbon liquid at the bottom of the regeneration tower 6 to a boiling state, generating steam to drive the decomposition process. SOFC waste heat is used to replace traditional external steam or gas heating, which greatly reduces the regeneration energy consumption. The 500℃ tail gas is cooled to 120℃ and discharged, realizing the cascade utilization of heat.

[0023] The CO2 condenser 7 has a cold-side inlet connected to the input unit 2 to receive 30°C cooling water, and a cold-side outlet connected to the output unit 3 to output cooling water heated to 35°C after heat absorption. Its hot-side inlet is connected to the high-temperature CO2 outlet at the top of the regeneration tower 6. It is used to cool the 105°C CO2 decomposed by the 30°C cooling water and separate the water, outputting 40°C CO2. The low-temperature cooling water condenses the water vapor in the high-temperature CO2 gas flow to achieve gas-liquid separation, obtain dry CO2 gas, and produce pure 40°C CO2 for subsequent compression and storage. At the same time, the water separated by condensation can be reused or discharged, and the cooling water is heated to 35°C to recover waste heat.

[0024] The rich and lean liquid circulation supply component is used to realize the closed-loop circulation and heat cascade utilization of the ammonium carbonate solution between the absorption tower 5 and the regeneration tower 6. The rich liquid at the bottom of the absorption tower 5 is transported to the regeneration tower 6 for regeneration through pumps, heat exchangers and other equipment. The regenerated lean liquid is then cooled and sent back to the absorption tower 5 to form a closed loop. At the same time, heat is recovered through heat exchange during the circulation process to ensure the continuous recycling of the absorbent, reduce the need for fresh solution replenishment, and reduce the overall energy consumption of the system through heat recovery. This is the core guarantee for the system to achieve low energy consumption operation.

[0025] In this embodiment, it is further preferred that the lean and rich liquid circulation supply component includes... The rich liquid transmission path is provided with a first transfer pump 8 and a first heat exchange channel of a lean-rich liquid heat exchanger 9. The inlet of the rich liquid transmission path is connected to the rich liquid outlet at the bottom of the absorption tower 5, and is used to transport 50°C rich amine liquid to the lean-rich liquid heat exchanger 9 via the first transfer pump 8 to heat it to 110°C rich amine liquid. The outlet of the rich liquid transmission path is connected to the rich liquid inlet of the regeneration tower 6, thereby introducing 110°C rich amine liquid into the regeneration tower 6. The lean liquid transport path is equipped with a second delivery pump 10, a second heat exchange channel of the lean-rich liquid heat exchanger 9, and a lean liquid cooler 11. The inlet of the lean liquid transport path is connected to the lean liquid outlet at the bottom of the regeneration tower 6. It is used to send 120°C lean amine liquid into the second heat exchange channel of the lean-rich liquid heat exchanger 9 via the second delivery pump 10 to cool it to 70°C. Then, the 70°C lean amine liquid is sent to the lean liquid cooler 11 for further cooling to 40°C. The outlet of the lean liquid transport path is connected to the lean liquid inlet at the top of the absorption tower 5 to introduce 40°C lean amine liquid into the absorption tower 5. A closed-loop circulation of the ammonium carbonate solution is achieved through two independent transmission paths. In the rich solution path, the first transfer pump 8 sends the low-temperature rich solution from the bottom of the absorption tower 5 to the heat exchanger for heating, bringing it to the regeneration temperature. In the lean solution path, the second transfer pump 10 sends the high-temperature lean solution from the bottom of the regeneration tower 6 to the heat exchanger and cooler in sequence. Through two-stage cooling, the absorption capacity is restored. The heat exchanger 9 between the rich and lean solutions achieves heat exchange between the high-temperature lean solution and the low-temperature rich solution, completing the transfer of heat from the lean solution to the rich solution. This design enables the continuous recycling of the ammonium carbonate solution and avoids one-time consumption. By recovering the heat from the high-temperature lean solution through the heat exchange between the rich and lean solutions to preheat the rich solution, the heating load of the regeneration tower 6 and the cooling burden of the lean solution cooler 11 are significantly reduced. The 40°C lean solution precisely controls the inlet temperature of the absorption tower 5, ensuring absorption efficiency. The whole system forms a highly efficient and low-energy-consumption absorbent circulation system.

[0026] In this embodiment, it is further preferred that the 40℃ CO2 discharged from the output unit 3 is compressed and then transferred to the CO2 storage tank 12 for storage. The CO2 storage tank 12 is connected to the output unit 3 to realize the resource-based capture and storage of CO2, meet the emission reduction requirements under the background of carbon neutrality, and the high-pressure storage method facilitates subsequent transportation or utilization, provides conditions for CO2 storage, and forms a complete product collection chain with the output unit 3.

[0027] In this embodiment, it is further preferred that the desulfurized and decarbonized fuel discharged from the output unit 3 is reintroduced into the SOFC stack 1 as fuel input. The sulfur content and CO2 of the fuel purified by the absorption tower 5 have been removed, meeting the fuel quality requirements of the SOFC stack 1. The purified fuel is returned to the anode inlet of the stack to replace or supplement external fresh fuel, realizing the resource recycling of fuel, reducing external fuel consumption, lowering system operating costs, forming a complete energy closed loop from SOFC power generation to exhaust gas treatment and fuel reuse, and significantly improving the overall energy utilization efficiency of the system.

[0028] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made by those skilled in the art based on the structure, shape, and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A desulfurization, decarbonization, and carbon dioxide recovery system driven by SOFC tail gas, characterized in that: include The SOFC stack has a cathode tail gas outlet and an anode tail gas outlet, which are used to output 500°C cathode tail gas and 500°C anode tail gas, respectively. The input unit is used to receive and distribute the following media into the system: 30°C cooling water, sulfur-containing fuel gas, 500°C cathode tail gas, and 500°C anode tail gas. The output unit is used to collect and export the following media discharged from the system: desulfurized and decarbonized fuel, water at 35°C, cathode tail gas at 120°C, and CO2 at 40°C. A precooler has its hot-side inlet connected to the input unit to receive 500°C anode tail gas and its cold-side inlet connected to the input unit to receive 30°C cooling water. The precooler is used to precool the 500°C high-temperature anode tail gas to 40°C using 30°C cooling water. The absorption tower has a fuel inlet and a rich liquid outlet at its lower part, and a purified fuel outlet and a lean liquid inlet at its upper part. The fuel inlet is connected to the input unit to receive sulfur-containing fuel gas, which flows from bottom to top within the absorption tower. The lean liquid inlet is connected to a lean-rich liquid circulation supply component to introduce 40°C lean amine liquid, which is sprayed from top to bottom within the absorption tower, coming into countercurrent contact with the sulfur-containing fuel gas and undergoing a gas-liquid phase mass transfer reaction to absorb acidic components from the sulfur-containing fuel gas. The purified fuel outlet of the absorption tower is connected to the output unit for discharging desulfurized and decarbonized fuel. The rich liquid outlet of the absorption tower is used to discharge amine liquid heated to 50°C after absorbing acidic components. The regeneration tower has a rich liquor inlet and a high-temperature CO2 outlet at the top, and a lean liquor outlet and a reboiler at the bottom. The rich liquor inlet is connected to a rich-lean-rich liquor circulation supply assembly to receive 110°C rich amine liquor, allowing it to flow downwards within the regeneration tower. The lean liquor outlet discharges lean amine liquor heated to 120°C after heating and desorption. The hot-side inlet of the reboiler is connected to the input unit to receive 500°C cathode tail gas, which is used to heat the amine liquor in the regeneration tower, causing it to boil and release 105°C CO2. The reboiler outlet discharges the cooled 120°C cathode tail gas and connects to the output unit. The high-temperature CO2 outlet of the regeneration tower discharges 105°C CO2. The CO2 condenser has a cold-side inlet connected to the input unit to receive 30°C cooling water, a cold-side outlet connected to the output unit to output cooling water that has absorbed heat and been heated to 35°C, and a hot-side inlet connected to the high-temperature CO2 outlet at the top of the regeneration tower. It is used to cool the 105°C CO2 that has been decomposed by the 30°C cooling water and separate the water, and output 40°C CO2. The lean and rich liquid circulation supply component is used to realize the closed-loop circulation of carbon-amine liquid between the absorption tower and the regeneration tower and the cascade utilization of heat.

2. The SOFC tail gas driven desulfurization, decarbonization, and carbon dioxide recovery system according to claim 1, characterized in that: The lean-rich liquid circulation supply component includes: The rich liquid transport path is provided with a first delivery pump and a first heat exchange channel of a lean-rich liquid heat exchanger. The inlet of the rich liquid transport path is connected to the rich liquid outlet at the bottom of the absorption tower, and is used to transport 50°C rich amine liquid to the lean-rich liquid heat exchanger via the first delivery pump to heat it to 110°C rich amine liquid. The outlet of the rich liquid transport path is connected to the rich liquid inlet of the regeneration tower, thereby introducing 110°C rich amine liquid into the regeneration tower. The lean liquor transport path includes a second delivery pump, a second heat exchange channel of a lean-rich liquor heat exchanger, and a lean liquor cooler. The inlet of the lean liquor transport path is connected to the lean liquor outlet at the bottom of the regeneration tower. It is used to sequentially send 120°C lean amine liquor into the second heat exchange channel of the lean-rich liquor heat exchanger via the second delivery pump to cool it to 70°C. Then, the 70°C lean amine liquor is sent to the lean liquor cooler for further cooling to 40°C. The outlet of the lean liquor transport path is connected to the lean liquor inlet at the top of the absorption tower to introduce the 40°C lean amine liquor into the absorption tower.

3. The SOFC tail gas driven desulfurization, decarbonization, and carbon dioxide recovery system according to claim 1, characterized in that: The 40°C CO2 discharged from the output unit is compressed and then transferred to a CO2 storage tank for storage. The CO2 storage tank is connected to the output unit.

4. The SOFC tail gas driven desulfurization, decarbonization, and carbon dioxide recovery system according to claim 1, characterized in that: The desulfurized and decarbonized fuel discharged from the output unit is reintroduced into the SOFC stack as fuel input.

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