A fuel cell system directly utilizing methanol reforming gas and its working method

Abstract

A fuel cell system directly using methanol reforming gas and its working method disclosed by the present invention belong to the technical field of fuel cells. It mainly includes a methanol reforming reaction unit, a first heat exchange unit, a first gas-liquid separation unit, a second gas-liquid separation unit, a catalytic combustion unit, a second heat exchange unit, a third heat exchange unit, a fuel cell unit and a gas mixing device. The present invention directly uses methanol reforming gas as the anode raw material without performing hydrogen purification and separation treatment, shortening and simplifying the process flow; at the same time, the anode tail gas is catalytically combusted to fully release the heat of the unreacted hydrogen in the anode tail gas, improving the thermal efficiency of the fuel cell power generation system, and mixing the catalytically combusted anode tail gas with the cathode intake gas for recycling as the cathode raw material, improving the fuel utilization rate and the comprehensive thermoelectric efficiency of the molten carbonate fuel cell power generation system, and having good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a fuel cell system directly using methanol reformed gas and a working method thereof. Background Art

[0002] A molten carbonate fuel cell is a high-temperature fuel cell operating at 650˚C. Using a hydrogen-rich gas as a raw material, it can directly convert the chemical energy in the raw material into electrical energy, which is a clean, efficient, low-noise, and low-pollution power generation method.

[0003] Currently, the cost of molten carbonate fuel cell power generation systems using hydrogen, natural gas, and syngas as raw materials is relatively high. Methanol steam reforming for hydrogen production is a low-cost, clean, and efficient hydrogen production method. Combining it with a molten carbonate fuel cell and introducing the hydrogen produced by methanol reforming into the anode of the fuel cell to achieve a fuel cell power generation system using methanol as a raw material can reduce the power generation cost. However, traditional methanol steam reforming devices need to be equipped with gas separation devices to purify the hydrogen in the methanol reformed gas, with a complex and lengthy process and a relatively high cost, and the fuel utilization rate of molten carbonate fuel cells is low. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a fuel cell system directly using methanol reformed gas and a working method thereof, which shortens the process flow of a molten carbonate fuel cell power generation system using methanol as a raw material, reduces the cost of the molten carbonate fuel cell power generation system and the power generation cost, and fully utilizes the energy in the fuel.

[0005] The present invention is realized through the following technical solutions:

[0006] The present invention discloses a fuel cell system directly using methanol reformed gas, including a methanol reforming reaction unit, a first heat exchange unit, a first gas-liquid separation unit, a second gas-liquid separation unit, a catalytic combustion unit, a second heat exchange unit, a third heat exchange unit, a fuel cell unit, and a gas mixing device;

[0007] The inlet of the methanol reforming reaction unit is connected to a methanol feed pipe. The outlet of the methanol reforming reaction unit is connected to the hot side inlet of the first heat exchange unit. The hot side outlet of the first heat exchange unit is connected to the inlet of the first gas-liquid separation unit. The gas phase outlet of the first gas-liquid separation unit is connected to the cold side inlet of the second heat exchange unit. The cold side outlet of the second heat exchange unit is connected to the anode fuel inlet of the fuel cell unit. The anode tail gas outlet of the fuel cell unit is connected to the inlet of the catalytic combustion unit. The inlet of the catalytic combustion unit is also connected to an O2 inlet pipe. The outlet of the catalytic combustion unit is connected to the hot side inlet of the second heat exchange unit. The hot side outlet of the second heat exchange unit is connected to the inlet of the second gas-liquid separation unit. The gas phase outlet of the second gas-liquid separation unit is connected to the inlet of the gas mixing device. The inlet of the gas mixing device is also connected to an air inlet pipe and a CO2 inlet pipe. The outlet of the gas mixing device is connected to the cold side inlet of the third heat exchange unit. The cold side outlet of the third heat exchange unit is connected to the cathode fuel inlet of the fuel cell unit. The cathode tail gas outlet of the fuel cell unit is connected to the hot side inlet of the third heat exchange unit. The hot side outlet of the third heat exchange unit is connected to a cathode tail gas discharge pipe. The liquid phase outlets of the first gas-liquid separation unit and the second gas-liquid separation unit are both connected to a condensate discharge pipe.

[0008] Preferably, an anode gas flow detection and control device is provided on the connecting pipeline between the cold side outlet of the second heat exchange unit and the anode fuel inlet of the fuel cell unit. A cathode gas flow detection and control device is provided on the connecting pipeline between the cold side outlet of the third heat exchange unit and the cathode fuel inlet of the fuel cell unit. An air flow detection and control device is provided on the air inlet pipe. A CO2 flow detection and control device is provided on the CO2 inlet pipe. An anode tail gas flow detection and control device is provided on the connecting pipeline between the gas phase outlet of the second gas-liquid separation unit and the inlet of the gas mixing device. The anode gas flow detection and control device, the cathode gas flow detection and control device, the air flow detection and control device, the CO2 flow detection and control device, and the anode tail gas flow detection and control device are all respectively connected to the control unit of the system.

[0009] Preferably, a compression unit is provided on the connecting pipeline between the gas phase outlet of the second gas-liquid separation unit and the inlet of the gas mixing device.

[0010] Further preferably, a demisting device is provided before the inlet of the compression unit.

[0011] Preferably, the first heat exchange unit is a gas-liquid heat exchanger, and the second and third heat exchange units are gas-gas heat exchangers.

[0012] Preferably, the condensate outlets of the first gas-liquid separation unit and the second gas-liquid separation unit are respectively connected to the cold side inlet of the first heat exchange unit.

[0013] Further preferably, a temperature detection device is provided on the connecting pipeline between the outlet of the methanol reforming reaction unit and the hot side inlet of the first heat exchange unit, and flow rate detection and control devices are respectively provided on the connecting pipelines between the condensate outlets of the first gas-liquid separation unit and the second gas-liquid separation unit and the cold side inlet of the first heat exchange unit. The temperature detection device and the flow rate detection and control device are respectively connected to the control unit of the system.

[0014] Preferably, the inner wall surface of the gas mixing device is a smooth curved surface, and a flow disturbing component is provided inside the gas mixing device.

[0015] Preferably, a first waste heat exchanger is provided between the second heat exchange unit and the second gas-liquid separation unit, and a second waste heat exchanger is provided on the cathode tail gas discharge pipe. Both the first waste heat exchanger and the second waste heat exchanger are used to heat an external medium.

[0016] The working method of the fuel cell system directly using methanol reforming gas disclosed by the present invention is characterized by comprising:

[0017] The methanol reforming reaction unit conducts a methanol reforming reaction. The generated mixed gas enters the first heat exchange unit for heat exchange and condensation, and then enters the first gas-liquid separation unit to remove moisture, obtaining a low-temperature mixed gas containing hydrogen and carbon dioxide. The low-temperature mixed gas is heated and raised in temperature in the second heat exchange unit and then enters the anode fuel inlet of the fuel cell unit. The anode tail gas enters the catalytic combustion unit to remove unreacted H2, then enters the second heat exchange unit for heat exchange and condensation, and is then dewatered in the second gas-liquid separation unit. The remaining gas enters the gas mixing device, mixes with air and CO2, is heated and raised in temperature in the third heat exchange unit, and then enters the cathode fuel inlet of the fuel cell unit. The cathode tail gas enters the third heat exchange unit for heat exchange and cooling and is then discharged through the cathode tail gas discharge pipe.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] For the fuel cell system directly using methanol reforming gas disclosed by the present invention, the anode fuel required by the fuel cell unit is a hydrogen-rich gas, and the cathode fuel is carbon dioxide and air. It can make full use of the hydrogen and carbon dioxide generated by the methanol reforming hydrogen production process as fuels, and the cost of the methanol reforming hydrogen production process is low. By directly using methanol reforming gas, only water vapor is removed, and no separation and purification treatment is performed on the hydrogen and carbon dioxide therein, so the process route is simple. The anode tail gas of the fuel cell is subjected to catalytic combustion treatment, making full use of the heat of the unreacted hydrogen in the anode tail gas and improving the thermal efficiency of the power generation battery system. Subsequently, the anode tail gas after catalytic combustion is mixed with the cathode intake gas and used as the cathode raw material for reuse. The waste heat of the tail gas is comprehensively utilized, improving the comprehensive thermoelectric efficiency of the fuel cell power generation system and reducing the system energy consumption.

[0020] Furthermore, by installing flow detection and control devices at key positions in the system, the key operating parameters of the system can be controlled to ensure the efficient and stable operation of the system.

[0021] Furthermore, a compression unit is provided on the connecting pipeline between the gas-phase outlet of the second gas-liquid separation unit and the inlet of the gas mixing device, which can control the speed and flow rate of the circulating tail gas.

[0022] Even further, a demisting device is provided in front of the inlet of the compression unit to prevent the moisture that has not been completely removed from affecting the normal operation of the compression unit.

[0023] Furthermore, the first heat exchange unit uses a gas-liquid heat exchanger, and the second and third heat exchange units use gas-gas heat exchangers, which have high heat exchange efficiency and improve the utilization rate of waste heat.

[0024] Furthermore, the condensate water from the first gas-liquid separation unit and the second gas-liquid separation unit is used to cool the mixed gas, which improves the energy utilization rate and reduces the energy consumption of the system.

[0025] Furthermore, the inner wall surface of the gas mixing device adopts a smooth curved surface to ensure the uniform flow of the internal gas without dead ends, and at the same time, the flow disturbing components can improve the degree of gas mixing.

[0026] Furthermore, the setting of the first waste heat exchanger and the second waste heat exchanger can make full use of the remaining heat again for external heating, lithium bromide refrigeration, etc.

[0027] The working method of the fuel cell system directly using methanol reformed gas disclosed in the present invention has a simple process flow, makes full use of the reaction products and their waste heat in the system, has low system cost, low energy consumption, and high comprehensive thermoelectric efficiency, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the system of the present invention.

[0029] In the figure: 1 - methanol reforming reaction unit; 2 - first heat exchange unit; 3 - first gas-liquid separation unit; 4 - second gas-liquid separation unit; 5 - catalytic combustion unit; 6 - second heat exchange unit; 7 - compression unit; 8 - third heat exchange unit; 9 - fuel cell unit; 10 - gas mixing device; 11 - methanol storage tank; 12 - anode gas flow detection and control device; 13 - cathode gas flow detection and control device; 14 - air flow detection and control device; 15 - CO2 flow detection and control device; 16 - anode tail gas flow detection and control device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following further describes the present invention in detail with reference to the drawings. The content is an explanation of the present invention rather than a limitation:

[0031] As shown in Figure 1 , a fuel cell system directly utilizing methanol reformed gas according to the present invention mainly includes a methanol reforming reaction unit 1, a first heat exchange unit 2, a first gas-liquid separation unit 3, a second gas-liquid separation unit 4, a catalytic combustion unit 5, a second heat exchange unit 6, a third heat exchange unit 8, a fuel cell unit 9, and a gas mixing device 10.

[0032] The inlet of the methanol reforming reaction unit 1 is connected with a methanol feed pipe, the outlet of the methanol reforming reaction unit 1 is connected with the hot side inlet of the first heat exchange unit 2, the hot side outlet of the first heat exchange unit 2 is connected with the inlet of the first gas-liquid separation unit 3, the gas phase outlet of the first gas-liquid separation unit 3 is connected with the cold side inlet of the second heat exchange unit 6, the cold side outlet of the second heat exchange unit 6 is connected with the anode fuel feed port of the fuel cell unit 9, the anode tail gas outlet of the fuel cell unit 9 is connected with the inlet of the catalytic combustion unit 5, the inlet of the catalytic combustion unit 5 is also connected with an O2 inlet pipe, the outlet of the catalytic combustion unit 5 is connected with the hot side inlet of the second heat exchange unit 6, the hot side outlet of the second heat exchange unit 6 is connected with the inlet of the second gas-liquid separation unit 4, the gas phase outlet of the second gas-liquid separation unit 4 is connected with the inlet of the gas mixing device 10, the inlet of the gas mixing device 10 is also connected with an air inlet pipe and a CO2 inlet pipe, the outlet of the gas mixing device 10 is connected with the cold side inlet of the third heat exchange unit 8, the cold side outlet of the third heat exchange unit 8 is connected with the cathode fuel feed port of the fuel cell unit 9, the cathode tail gas outlet of the fuel cell unit 9 is connected with the hot side inlet of the third heat exchange unit 8, and the hot side outlet of the third heat exchange unit 8 is connected with a cathode tail gas discharge pipe; the liquid phase outlets of the first gas-liquid separation unit 3 and the second gas-liquid separation unit 4 are both connected with condensate discharge pipes.

[0033] In a preferred embodiment of the present invention, an anode gas flow rate detection and control device 12 is provided on the connecting pipeline between the cold side outlet of the second heat exchange unit 6 and the anode fuel feed port of the fuel cell unit 9, a cathode gas flow rate detection and control device 13 is provided on the connecting pipeline between the cold side outlet of the third heat exchange unit 8 and the cathode fuel feed port of the fuel cell unit 9, an air flow rate detection and control device 14 is provided on the air inlet pipe, a CO2 flow rate detection and control device 15 is provided on the CO2 inlet pipe, and an anode tail gas flow rate detection and control device 16 is provided on the connecting pipeline between the gas phase outlet of the second gas-liquid separation unit 4 and the inlet of the gas mixing device 10; the anode gas flow rate detection and control device 12, the cathode gas flow rate detection and control device 13, the air flow rate detection and control device 14, the CO2 flow rate detection and control device 15, and the anode tail gas flow rate detection and control device 16 are all connected to the control unit of the system respectively.

[0034] In a preferred embodiment of the present invention, a compression unit 7 is provided on the connecting pipeline between the gas-phase outlet of the second gas-liquid separation unit 4 and the inlet of the gas mixing device 10. Preferably, a demisting device, such as a demisting net or a demisting grid plate, is provided before the inlet of the compression unit 7.

[0035] In a preferred embodiment of the present invention, the first heat exchange unit 2 is a gas-liquid heat exchanger, and the second heat exchange unit 6 and the third heat exchange unit 8 are gas-gas heat exchangers.

[0036] In a preferred embodiment of the present invention, the condensate outlets of the first gas-liquid separation unit 3 and the second gas-liquid separation unit 4 are respectively connected to the cold-side inlets of the first heat exchange unit 2. Preferably, a temperature detection device is provided on the connecting pipeline between the outlet of the methanol reforming reaction unit 1 and the hot-side inlet of the first heat exchange unit 2, and flow detection and control devices are respectively provided on the connecting pipelines between the condensate outlets of the first gas-liquid separation unit 3 and the second gas-liquid separation unit 4 and the cold-side inlets of the first heat exchange unit 2. The temperature detection device and the flow detection and control devices are respectively connected to the control unit of the system.

[0037] In a preferred embodiment of the present invention, the inner wall surface of the gas mixing device 10 is a smooth curved surface, and turbulence components, such as turbulence columns and turbulence plates, are provided inside the gas mixing device 10.

[0038] In a preferred embodiment of the present invention, a first waste heat exchanger is provided between the second heat exchange unit 6 and the second gas-liquid separation unit 4, and a second waste heat exchanger is provided on the cathode tail gas discharge pipe. The first waste heat exchanger and the second waste heat exchanger are both used to heat external media and can be used for heating, lithium bromide refrigeration, etc.

[0039] The working method of the above system is as follows:

[0040] The methanol reforming reaction unit 1 undergoes a methanol reforming reaction, and the generated mixed gas enters the first heat exchange unit 2 for heat exchange and condensation, and then enters the first gas-liquid separation unit 3 to remove moisture, obtaining a low-temperature mixed gas containing hydrogen and carbon dioxide; the low-temperature mixed gas is heated and raised in temperature in the second heat exchange unit 6 and then enters the anode fuel inlet of the fuel cell unit 9. The anode tail gas enters the catalytic combustion unit 5 to remove unreacted H2 and then enters the second heat exchange unit 6 for heat exchange and condensation, and then enters the second gas-liquid separation unit 4 to remove moisture. The remaining gas enters the gas mixing device 10, is mixed with air and CO2, is heated and raised in temperature in the third heat exchange unit 8, and then enters the cathode fuel inlet of the fuel cell unit 9. The cathode tail gas enters the third heat exchange unit 8 for heat exchange and cooling and is discharged through the cathode tail gas discharge pipe.

[0041] The working principle of the present invention is as follows:

[0042] The system mainly consists of a fuel processing system, a fuel cell body, and an anode tail gas circulation and waste heat recovery and utilization system.

[0043] The fuel processing system mainly includes a methanol reforming hydrogen production unit and a steam condensation and separation unit. The methanol reforming hydrogen production unit mainly undergoes a reforming reaction with methanol and water, which generates a mixed gas (containing water) of hydrogen and carbon dioxide with respective proportions of approximately 75% and 25%, as shown in the following reaction equation, to produce a mixed gas mainly composed of hydrogen and carbon dioxide, and then the water in the methanol reformed gas is removed through condensation separation.

[0044]

[0045] The molten carbonate fuel cell stack body operates at 650˚C. The anode uses a hydrogen-rich gas as fuel, and in this patent, the methanol reformed gas is used as the anode fuel, and the carbon dioxide in the methanol reformed gas does not participate in the reaction; the cathode uses carbon dioxide and oxygen (from air) as raw materials and undergoes an electrochemical reaction inside the fuel cell.

[0046] The tail gas circulation unit mainly means that the anode tail gas first undergoes catalytic combustion to remove the unreacted hydrogen, and then the water vapor in the anode tail gas is removed through heat exchange and condensation separation. At this time, the main component of the anode tail gas is carbon dioxide. Then this anode tail gas is mixed with the cathode intake air and reused as the cathode raw material.

[0047] The waste heat recovery and utilization unit mainly utilizes the waste heat of the high-temperature anode tail gas and high-temperature cathode tail gas of the molten carbonate fuel cell. First, it recovers the waste heat of the anode intake air and cathode intake air of the molten carbonate fuel cell. After the waste heat recovery, the remaining low-grade heat in the fuel cell tail gas and the low-grade heat of the methanol reformed gas can be heat-exchanged with cold water for heating, lithium bromide refrigeration, etc.

[0048] As described above, it is only a part of the embodiments of the present invention. Although some terms are used in the present invention, the possibility of using other terms is not excluded. These terms are only used for the convenience of describing and explaining the essence of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention. The above description only further illustrates the content of the present invention with examples for easier understanding, but does not mean that the embodiments of the present invention are limited thereto. Any technical extension or re-creation based on the present invention is protected by the present invention.

Claims

1. A fuel cell system directly utilizing methanol reformed gas, characterized in that It includes a methanol reforming reaction unit (1), a first heat exchange unit (2), a first gas-liquid separation unit (3), a second gas-liquid separation unit (4), a catalytic combustion unit (5), a second heat exchange unit (6), a third heat exchange unit (8), a fuel cell unit (9) and a gas mixing device (10); The inlet of the methanol reforming reaction unit (1) is connected with a methanol feed pipe. The outlet of the methanol reforming reaction unit (1) is connected with the hot-side inlet of the first heat exchange unit (2). The hot-side outlet of the first heat exchange unit (2) is connected with the inlet of the first gas-liquid separation unit (3). The gas-phase outlet of the first gas-liquid separation unit (3) is connected with the cold-side inlet of the second heat exchange unit (6). The cold-side outlet of the second heat exchange unit (6) is connected with the anode fuel feed port of the fuel cell unit (9). The anode tail gas outlet of the fuel cell unit (9) is connected with the inlet of the catalytic combustion unit (5). The inlet of the catalytic combustion unit (5) is also connected with an O2 inlet pipe. The outlet of the catalytic combustion unit (5) is connected with the hot-side inlet of the second heat exchange unit (6). The hot-side outlet of the second heat exchange unit (6) is connected with the inlet of the second gas-liquid separation unit (4). The gas-phase outlet of the second gas-liquid separation unit (4) is connected with the inlet of the gas mixing device (10). The inlet of the gas mixing device (10) is also connected with an air inlet pipe and a CO2 inlet pipe. The outlet of the gas mixing device (10) is connected with the cold-side inlet of the third heat exchange unit (8). The cold-side outlet of the third heat exchange unit (8) is connected with the cathode fuel feed port of the fuel cell unit (9). The cathode tail gas outlet of the fuel cell unit (9) is connected with the hot-side inlet of the third heat exchange unit (8). The hot-side outlet of the third heat exchange unit (8) is connected with a cathode tail gas discharge pipe. The liquid-phase outlets of the first gas-liquid separation unit (3) and the second gas-liquid separation unit (4) are both connected with condensate discharge pipes; The condensate outlets of the first gas-liquid separation unit (3) and the second gas-liquid separation unit (4) are respectively connected with the cold-side inlets of the first heat exchange unit (2); Flow detection and control devices are respectively provided on the connecting pipelines between the condensate outlets of the first gas-liquid separation unit (3) and the second gas-liquid separation unit (4) and the cold-side inlets of the first heat exchange unit (2), and the flow detection and control devices are connected with the control unit of the system; The first heat exchange unit (2) is a gas-liquid heat exchanger, and the second heat exchange unit (6) and the third heat exchange unit (8) are gas-gas heat exchangers.

2. The fuel cell system directly utilizing methanol reformate gas according to claim 1, characterized in that, An anode gas flow detection and control device (12) is provided on the connecting pipeline between the cold-side outlet of the second heat exchange unit (6) and the anode fuel inlet of the fuel cell unit (9). A cathode gas flow detection and control device (13) is provided on the connecting pipeline between the cold-side outlet of the third heat exchange unit (8) and the cathode fuel inlet of the fuel cell unit (9). An air flow detection and control device (14) is provided on the air inlet pipe. A CO2 flow detection and control device (15) is provided on the CO2 inlet pipe. An anode tail gas flow detection and control device (16) is provided on the connecting pipeline between the gas-phase outlet of the second gas-liquid separation unit (4) and the inlet of the gas mixing device (10); the anode gas flow detection and control device (12), the cathode gas flow detection and control device (13), the air flow detection and control device (14), the CO2 flow detection and control device (15), and the anode tail gas flow detection and control device (16) are all connected to the control unit of the system respectively.

3. The fuel cell system directly utilizing methanol reformed gas according to claim 1, characterized in that, A compression unit (7) is provided on the connecting pipeline between the gas-phase outlet of the second gas-liquid separation unit (4) and the inlet of the gas mixing device (10).

4. The fuel cell system directly using methanol reformed gas according to claim 3, characterized in that, A demisting device is provided before the inlet of the compression unit (7).

5. The fuel cell system directly using methanol reformed gas according to claim 1, characterized in that, A temperature detection device is provided on the connecting pipeline between the outlet of the methanol reforming reaction unit (1) and the hot-side inlet of the first heat exchange unit (2), and the temperature detection device is connected to the control unit of the system.

6. The fuel cell system directly using methanol reformed gas according to claim 1, characterized in that, The inner wall surface of the gas mixing device (10) is a smooth curved surface, and a flow disturbing component is provided inside the gas mixing device (10).

7. The fuel cell system directly using methanol reformed gas according to claim 1, characterized in that, A first waste heat exchanger is provided between the second heat exchange unit (6) and the second gas-liquid separation unit (4), and a second waste heat exchanger is provided on the cathode tail gas discharge pipe. Both the first waste heat exchanger and the second waste heat exchanger are used to heat an external medium.

8. The working method of the fuel cell system directly using methanol reformed gas according to any one of claims 1 to 7, characterized in that, Including: The methanol reforming reaction unit (1) undergoes a methanol reforming reaction. The generated mixed gas enters the first heat exchange unit (2) for heat exchange and condensation, and then enters the first gas-liquid separation unit (3) to remove moisture, obtaining a low-temperature mixed gas containing hydrogen and carbon dioxide; the low-temperature mixed gas enters the anode fuel inlet of the fuel cell unit (9) after heat exchange and temperature rise in the second heat exchange unit (6). The anode tail gas enters the catalytic combustion unit (5) to remove unreacted H2 and then enters the second heat exchange unit (6) for heat exchange and condensation, and then removes moisture in the second gas-liquid separation unit (4). The remaining gas enters the gas mixing device (10), mixes with air and CO2, enters the cathode fuel inlet of the fuel cell unit (9) after heat exchange and temperature rise in the third heat exchange unit (8), and the cathode tail gas enters the third heat exchange unit (8) for heat exchange and temperature reduction and is discharged through the cathode tail gas discharge pipe.

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