Depth-coupled SOFC-SOEC integrated system

Abstract

The invention discloses a deep coupling SOFC-SOEC integrated system which comprises an SOFC system, an SOEC system and a fused salt heat storage and exchange system, the SOFC system is connected with the fused salt heat storage and exchange system, the fused salt heat storage and exchange system is connected with the SOEC system, and waste heat of the SOFC system is utilized in the SOEC system through the fused salt heat storage and exchange system. The system is simple in structure, the SOFC system is used for supplementing heat for the molten salt heat storage system, tail gas of the SOEC system is subjected to heat exchange through the preheater and the heat pump system, waste heat in the tail gas of the SOFC system is subjected to sufficient heat exchange and then is used for the SOEC system, and the energy utilization rate and conversion efficiency are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cells (SOFC) / solid oxide electrolyzers (SOEC), and specifically refers to a deeply coupled SOFC-SOEC integrated system. Background Art

[0002] SOFC is a highly efficient electrochemical power generation device that converts hydrogen or hydrogen-rich gas (such as gas from natural gas reforming) and oxygen into electricity and water vapor through a solid electrolyte at high temperature. The advantages of SOFC are high energy conversion efficiency, low emissions, and the ability to flexibly use a variety of fuels, including hydrogen, carbon monoxide, methane, etc.

[0003] SOEC is a device that decomposes water into hydrogen and oxygen under the action of electricity. When DC power is applied, SOEC can achieve efficient water electrolysis under high temperature conditions to generate high-purity hydrogen, which is exactly the opposite of SOFC. SOEC is considered to be an advanced technology for large-scale, efficient and sustainable production of hydrogen. It is particularly suitable for use in combination with intermittent renewable energy (such as wind power and solar energy) to solve the problem of peak-valley load regulation of the power grid and provide a clean hydrogen source for the hydrogen economy.

[0004] The coupling technology of SOFC-SOEC aims to build an integrated energy system that can generate electricity and produce hydrogen. Such a system can flexibly switch functions according to demand and resource conditions. In the case of surplus renewable energy, SOEC can generate hydrogen by electrolyzing water and store it; when needed, SOFC can consume the stored hydrogen and combine it with oxygen to generate electricity, thereby achieving effective storage and conversion of energy. In addition, the heat management of the SOFC-SOEC coupling system is also very critical, because it can recover and effectively utilize the waste heat generated during the operation of the system, further improving the energy utilization efficiency of the entire system. Traditional SOEC systems usually use electric heating from electric furnaces to supply heat to the SOEC system. Conventional SOEC systems and SOFC systems mostly work separately. The heat required by the SOEC system during operation needs to be provided by electric heaters, while the heat generated by the SOFC system is recovered by waste heat recovery devices. This will cause a certain degree of waste of heat, which will have a certain impact on the energy utilization and conversion efficiency of both SOEC electrolysis and SOFC power generation. Summary of the invention

[0005] The object of the present invention is to provide a deeply coupled SOFC-SOEC integrated system, which has a simple structure and can improve energy utilization and conversion efficiency.

[0006] To achieve the above objectives, the deeply coupled SOFC-SOEC integrated system of the present invention comprises a SOFC system, a SOEC system and a molten salt heat storage and heat exchange system, wherein the SOFC system is connected to the molten salt heat storage and heat exchange system, which is connected to the SOEC system, and the waste heat of the SOFC system is utilized in the SOEC system through the molten salt heat storage and heat exchange system.

[0007] As a further solution of the present invention: the molten salt heat storage and heat exchange system includes a startup heating system, a heat exchange system, and a heat supplement system. The tail gas generated by the SOFC system passes through the molten salt heat storage and heat exchange system, and the high temperature of the tail gas is used to supplement heat for the molten salt heat storage and heat exchange system. The heat exchange system provides high-temperature steam and high-temperature air to the SOEC system.

[0008] As a further solution of the present invention: it also includes a preheater, a balancing heat exchanger, a heat storage heat exchanger, a heat pump system, a dryer, a compressor, and a hydrogen storage tank. The preheater is connected to an external air pump and an exhaust device through air pipelines, respectively. The preheater is also connected to the balancing heat exchanger and the SOEC system through air pipelines, respectively. The tail gas generated by the SOEC system is connected to the preheater through an air pipeline, and the balancing heat exchanger is connected to the SOFC system through an air pipeline. The tail gas generated by the SOFC system enters the molten salt heat storage heat exchange system through an air pipeline, and the gas discharged from the molten salt heat storage heat exchange system is connected to the preheater through an air pipeline.

[0009] The SOFC system transports the tail gas from the fuel side to the molten salt heat storage and heat exchange system (101) through a hydrogen pipeline for heat exchange. The tail gas passing through the molten salt heat storage and heat exchange system and the hydrogen generated by the SOEC system are transported to the heat storage heat exchanger through the hydrogen pipeline. The hydrogen output by the heat storage heat exchanger is transported to the heat pump system through the hydrogen pipeline. The hydrogen output by the heat pump system passes through the dryer and the compressor in sequence through the hydrogen pipeline and enters the hydrogen storage tank. The hydrogen storage tank enters the molten salt heat storage and heat exchange system through the hydrogen pipeline and valve control I. The hydrogen storage tank also transports hydrogen into the heat storage heat exchanger through the hydrogen pipeline and valve control II. The hydrogen output by the heat storage heat exchanger is also transported to the balance heat exchanger through the hydrogen pipeline.

[0010] As a further solution of the present invention: the heat pump system includes a condenser and an evaporator. The pure water and water vapor generated in the condenser are transported to the pure water storage tank through the pure water and water vapor pipeline. The pure water in the pure water storage tank passes through the pure water and water vapor pipeline and passes through the evaporator to form high-temperature water. The high-temperature water enters the molten salt heat storage and heat exchange system through the pure water and water vapor pipeline to form high-temperature steam. The molten salt heat storage and heat exchange system transports the high-temperature steam to the SOCE system through the pure water and water vapor pipeline.

[0011] As a further solution of the present invention: the SOFC system includes a fuel cell stack T1, and the SOEC system includes a fuel cell stack T2; both the fuel cell stack T1 and the fuel cell stack T2 are placed in a fuel cell insulation box.

[0012] As a further solution of the present invention: the high temperature tail gas of the SOFC system is utilized in the SOEC system through the molten salt heat storage and heat exchange system, and the tail gas of the SOEC system is used for heat exchange between the preheater and the heat pump system.

[0013] As a further solution of the present invention: the fuel and air at the SOFC system inlet and the water vapor and air at the SOEC system inlet are heat exchanged through the molten salt heat storage and heat exchange system to heat the inlet gas to the operating temperature.

[0014] Compared with the existing technology, this system has a simple structure. The SOFC system and the SOEC system are deeply coupled through the molten salt heat storage and heat exchange system and the heat pump system. The tail gas of the SOEC system is heat exchanged using a preheater and a heat pump system, and the waste heat in the tail gas of the SOFC system is fully exchanged and reused in the SOEC system, thereby improving energy utilization and conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the deeply coupled SOFC-SOEC integrated system of the present invention.

[0016] In the figure: 101, molten salt heat storage and heat exchange system, 102, heat storage heat exchanger, 201, SOEC system, 202, dryer, 203, compressor, 204, hydrogen storage tank, 205, pure water storage tank, 206, preheater, 207, air pump, 301, SOFC system, 302, balanced heat exchanger, 401, heat pump system, 402, condenser, 403, evaporator, 501, valve control I, 502, valve control II, 601, molten salt heat storage and heat exchange supplementary heat system integration. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown in the figure, the deeply coupled SOFC-SOEC integrated system, the red lines in the figure represent the hydrogen pipeline, the blue lines represent the air pipeline, and the purple lines represent the pure water and steam pipeline. The large dotted box in the figure is the molten salt heat storage, heat exchange and heat supplement system integration 601 part.

[0019] A deeply coupled SOFC-SOEC integrated system includes a preheater 206, a balanced heat exchanger 302, a SOFC system 301, a SOEC system 201, a molten salt heat storage and heat exchange system 101, a heat storage and heat exchanger 102, a heat pump system 401, a dryer 202, a compressor 203, and a hydrogen storage tank 204; each device is interconnected through a hydrogen pipeline, an air pipeline, or a pure water and water vapor pipeline as needed; the SOFC system 301 includes a fuel cell stack T1, and the SOEC system 201 includes a fuel cell stack T2; both the stack T1 and the stack T2 are placed in a stack insulation box; the operating temperature of the SOFC system 301 is higher than that of the SOEC system 201, the SOFC system 301 is connected to the molten salt heat storage and heat exchange system 101, the molten salt heat storage and heat exchange system 101 is connected to the SOEC system 201, and the waste heat of the SOFC system 301 is utilized in the SOEC system 201 through the molten salt heat storage and heat exchange system 101; the molten salt heat storage and heat exchange system 101 is also connected to the heat pump system 401 through the heat storage heat exchanger 102;

[0020] The molten salt heat storage and heat exchange system 101 includes a startup heating system, a heat exchange system, and a supplementary heat system. The exhaust gas generated by the SOFC system 301 passes through the molten salt heat storage and heat exchange system 101, and the high temperature of the exhaust gas is used to supplement heat for the molten salt heat storage and heat exchange system 101, and the heat is released through the heat exchange system to provide high-temperature steam and high-temperature air to the SOEC system 201.

[0021] The preheater 206 is connected to the external air pump 207 and the exhaust device through air pipelines, and the preheater 206 is also connected to the balancing heat exchanger 302 and the SOEC system 201 through air pipelines. The tail gas generated by the SOEC system 201 is connected to the preheater 206 through an air pipeline, and the balancing heat exchanger 302 is connected to the SOFC system 301 through an air pipeline. The tail gas generated by the SOFC system 301 enters the molten salt heat storage heat exchange system 101 through the air pipeline, and the gas discharged from the molten salt heat storage heat exchange system 101 is connected to the preheater 206 through an air pipeline;

[0022] The SOFC system 301 transports the fuel side tail gas to the molten salt heat storage and heat exchange system 101 through the hydrogen pipeline for heat exchange. The tail gas passing through the molten salt heat storage and heat exchange system 101 and the hydrogen generated by the SOEC system 201 are transported to the heat storage heat exchanger 102 through the hydrogen pipeline. The hydrogen output by the heat storage heat exchanger 102 is transported to the heat pump system 401 through the hydrogen pipeline. The hydrogen output by the heat pump system 401 passes through the hydrogen pipeline in sequence through the dryer 202 and the compressor 203 into the hydrogen storage tank 204. The hydrogen storage tank 204 enters the molten salt heat storage and heat exchange system 101 through the hydrogen pipeline and valve control I501. The hydrogen storage tank 204 also transports hydrogen into the heat storage heat exchanger 102 through the hydrogen pipeline and valve control II502. The hydrogen output by the heat storage heat exchanger 102 is also transported to the balancing heat exchanger 302 through the hydrogen pipeline.

[0023] The heat pump system 401 includes a condenser 402 and an evaporator 403. The pure water and water vapor generated in the condenser 402 are transported to the pure water storage tank 205 through the pure water and water vapor pipeline. The pure water in the pure water storage tank 205 passes through the pure water and water vapor pipeline and passes through the evaporator 403 to form high-temperature water. The high-temperature water enters the molten salt heat storage and heat exchange system 101 through the pure water and water vapor pipeline to form high-temperature steam. The molten salt heat storage and heat exchange system 101 transports the high-temperature steam to the SOEC system 201 through the pure water and water vapor pipeline.

[0024] The high-temperature exhaust gas generated by the SOFC system 301 is utilized in the SOEC system 201 through the molten salt heat storage and heat exchange system. The exhaust gas of the SOEC system 201 is used for heat exchange between the preheater 206 and the heat pump system 401.

[0025] The fuel and air at the inlet of the SOFC system 301 and the water vapor and air at the inlet of the SOEC system 201 are heat exchanged through the molten salt heat storage and heat exchange system 101 to heat the inlet gas to the operating temperature.

[0026] The working method of the deeply coupled SOFC-SOEC integrated system includes the following steps: first, the startup heating system in the molten salt heat storage and heat exchange system 101 is turned on, heat is provided by hydrogen combustion, the molten salt heat storage and heat exchange system 101 is heated to a high temperature of 750°C for storage, and an external heat source is provided to the SOEC system 201 and the SOFC system 301 to heat up the stacks T2 and T1; the hydrogen produced by the SOEC system 201 preheats the pure water in the pure water storage tank 205 through the heat pump system 401, and the preheated pure water enters the molten salt heat storage and heat exchange system 101, and is heated to high-temperature steam of 700°C by high-temperature molten salt for electrolysis in the SOEC system 201; the tail gas of the SOEC system is preheated by the preheater 206 to the air and then completely emptied, the preheated air all enters the molten salt heat storage and heat exchange system 101 to be heated to high-temperature air of 700°C, and a part of it enters the SOEC system 201, and a circulation loop is formed after the SOEC system 201 runs stably;

[0027] When the SOFC system 301 is in operation, the high-temperature 800°C cathode tail gas passes through the molten salt heat storage and heat exchange system 101, and the waste heat in the tail gas is used to heat the molten salt heat storage and heat exchange system 101 into a high-temperature molten salt of 750°C, which is stored in the molten salt heat storage and heat exchange system 101. After the tail gas comes out of the molten salt heat storage and heat exchange system 101, it passes through the preheater 206 to preheat the air at the inlet, and then is exhausted; the high-temperature 800°C anode tail gas of the SOFC system 301 passes through the molten salt heat storage and heat exchange system 101 to use the heat to heat the molten salt, and then passes through the heat pump system 4 01 Preheat pure water for use in the SOEC system 201. The anode tail gas is condensed by the condenser 402 and then enters the dryer 202 for drying. The high-purity hydrogen is then recovered and stored in the hydrogen storage tank 204 through the compressor 203. The air at the entrance of the SOFC system 301 is heated to 700°C air through the preheater 206 and the molten salt heat storage and heat exchange system. The hydrogen in the hydrogen storage tank 204 is converted into high-temperature fuel after heat exchange in the heat storage heat exchanger. The air and fuel enter the SOFC system 301 through the balance heat exchanger 302.

[0028] The SOFC system and SOEC system are deeply coupled through the molten salt heat storage and heat exchange system and the heat pump system, so that the waste heat in the exhaust gas of the SOFC system is fully exchanged and reused with the SOEC system, thereby improving energy utilization and conversion efficiency.

Claims

1. A deeply coupled SOFC-SOEC integrated system, comprising a SOFC system (301) and a SOEC system (201), characterized in that: It also includes a molten salt heat storage and heat exchange system (101), the SOFC system (301) is connected to the molten salt heat storage and heat exchange system (101), the molten salt heat storage and heat exchange system (101) is connected to the SOEC system (201), and the waste heat of the SOFC system (301) is utilized in the SOEC system (201) through the molten salt heat storage and heat exchange system (101).

2. A deeply coupled SOFC-SOEC integrated system according to claim 1, characterized in that: The molten salt heat storage and heat exchange system (101) comprises a start-up heat supply system, a heat exchange system, and a supplementary heat system. The tail gas generated by the SOFC system (301) passes through the molten salt heat storage and heat exchange system (101), and the high temperature of the tail gas is used to supplement heat for the molten salt heat storage and heat exchange system (101). The heat is released through the heat exchange system to provide high-temperature steam and high-temperature air to the SOEC system (201).

3. A deeply coupled SOFC-SOEC integrated system according to claim 1 or 2, characterized in that: The system also includes a preheater (206), a balancing heat exchanger (302), a heat storage heat exchanger (102), a heat pump system (401), a dryer (202), a compressor (203), and a hydrogen storage tank (204). The preheater (206) is connected to an external air pump (207) and an exhaust device through air pipelines. The preheater (206) is also connected to the balancing heat exchanger (302) and the SOEC system (201) through air pipelines. The tail gas generated by the SOEC system (201) is connected to the preheater (206) through an air pipeline. The balancing heat exchanger (302) is connected to the SOFC system (301) through an air pipeline. The tail gas generated by the SOFC system (301) enters the molten salt heat storage heat exchange system (101) through the air pipeline. The gas discharged from the molten salt heat storage heat exchange system (101) is connected to the preheater (206) through an air pipeline. The SOFC system (301) transports the fuel side tail gas to the molten salt heat storage and heat exchange system (101) through a hydrogen pipeline for heat exchange. The tail gas in the molten salt heat storage and heat exchange system (101) and the hydrogen generated by the SOEC system (201) are transported to the heat storage heat exchanger (102) through a hydrogen pipeline. The hydrogen output by the heat storage heat exchanger (102) is transported to the heat pump system (401) through a hydrogen pipeline. The hydrogen output by the heat pump system (401) is then transported to the heat storage heat exchanger (102). The hydrogen pipeline passes through the dryer (202) and the compressor (203) in sequence and enters the hydrogen storage tank (204). The hydrogen storage tank (204) enters the molten salt heat storage heat exchange system (101) through the hydrogen pipeline and valve control I (501). The hydrogen storage tank (204) also transports hydrogen into the heat storage heat exchanger (102) through the hydrogen pipeline and valve control II (502). The hydrogen output from the heat storage heat exchanger (102) is also transported to the balancing heat exchanger (302) through the hydrogen pipeline.

4. A deeply coupled SOFC-SOEC integrated system according to claim 3, characterized in that: The heat pump system (401) comprises a condenser (402) and an evaporator (403). The pure water and water vapor generated in the condenser (402) are transported to the pure water storage tank (205) through the pure water and water vapor pipeline. The pure water in the pure water storage tank (205) passes through the pure water and water vapor pipeline and then passes through the evaporator (403) to form high-temperature water. The high-temperature water enters the molten salt heat storage and heat exchange system (101) through the pure water and water vapor pipeline to form high-temperature steam. The molten salt heat storage and heat exchange system (101) transports the high-temperature steam to the SOCE system (201) through the pure water and water vapor pipeline.

5. A deeply coupled SOFC-SOEC integrated system according to claim 1, characterized in that: The SOFC system (301) includes a cell stack T1, and the SOEC system (201) includes a cell stack T2; both the cell stack T1 and the cell stack T2 are placed in a cell stack insulation box.

6. A deeply coupled SOFC-SOEC integrated system according to claim 1, characterized in that: The high-temperature exhaust gas of the SOFC system (301) is utilized in the SOEC system (201) through the molten salt heat storage and heat exchange system, and the exhaust gas of the SOEC system (201) is used for heat exchange between the preheater (206) and the heat pump system (401).

7. A deeply coupled SOFC-SOEC integrated system according to claim 1, characterized in that: The fuel and air imported by the SOFC system (301) and the water vapor and air imported by the SOEC system (201) are heat exchanged through the molten salt heat storage and heat exchange system (101) to heat the inlet gas to the operating temperature.

Images