A methanol solid oxide fuel cell system and a startup temperature rise control method thereof

Abstract

The present invention discloses a methanol solid oxide fuel cell system and a startup temperature control method thereof, wherein the methanol solid oxide fuel cell system shunts the anode tail gas outputted by the anode of the stack and the cathode tail gas outputted by the cathode of the stack to different parts, wherein the tail gas entering the burner is mixed and burned to further heat up, and simultaneously assumes the functions of system startup temperature rise and stack tail gas treatment. Moreover, the burner is also connected to a methanol evaporator, which simultaneously provides energy for methanol evaporation during the system startup temperature rise stage, and the methanol evaporated in the methanol evaporator can also be input into the burner, and supplementary combustion is performed for the burner during the stable power generation stage. The tail gas further heated up after combustion in the burner provides heat for the vaporization reforming unit, and the shunt tail gas is shunt to different parts for heat exchange, and the air outputted by the air supply unit enters the stack after heat exchange and temperature rise with the tail gas, so that the system heat is fully utilized, and the energy utilization rate of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells, and more specifically to a methanol solid oxide fuel cell system and a startup temperature rise control method thereof. Background Art

[0002] Methanol, as a fuel for solid oxide fuel cells, has the advantages of high energy density and easy storage and transportation. However, the copper-based catalysts commonly used in methanol reforming to produce hydrogen have a narrow operating temperature range of 200°C to 300°C. Moreover, this temperature is different from the operating temperature of the SOFC stack (600°C to 800°C). If electric heating or combustion heating is used alone for methanol reforming, the energy utilization efficiency of the system will be reduced.

[0003] In the existing methanol SOFC battery system, a burner is used to undertake two functions: system startup and heating, and stack tail gas treatment. If a burner is used to heat methanol, methanol as a liquid fuel is not convenient to burn directly, and methanol is prone to carbon deposition when directly introduced into a high-temperature pipeline; in addition, when methanol is vaporized and reformed into hydrogen for combustion, additional heat is required. At present, a two-burner design of a startup burner and a tail gas burner is generally adopted, or when the system starts and heats up, a heater is used to heat methanol and water to heat the reformer. This method increases the complexity of the system and power consumption.

[0004] The exhaust gas generated by the SOFC stack has a high temperature. Currently, the high-temperature stack exhaust gas is generally passed directly into the burner for combustion. However, when the stack fuel utilization rate is low, the burner is at risk of overheating, and when the stack fuel utilization rate is high, the burner is at risk of flameout. Summary of the invention

[0005] In view of at least some problems in the prior art, the present invention provides a methanol solid oxide fuel cell system, which rationally utilizes the tail gas of the fuel cell stack and improves the energy utilization rate of the system.

[0006] A start-up temperature rise control method for a methanol solid oxide fuel cell system is also provided to reasonably control the tail gas flow of the fuel cell stack and effectively control the fuel utilization in the burner.

[0007] In order to achieve the above object, the technical solution provided by the present invention is:

[0008] A methanol solid oxide fuel cell system comprises a fuel supply unit, an air supply unit, a fuel cell stack, a burner, a methanol evaporator and a vaporization reforming unit;

[0009] The stack comprises a stack anode and a stack cathode. The anode tail gas outputted from the stack anode is divided into a B1 anode tail gas and a B2 anode tail gas after heat exchange. The B1 anode tail gas is inputted into the burner for combustion, and the B2 anode tail gas is returned and inputted into the stack.

[0010] The cathode tail gas outputted from the cathode of the stack is divided into A1 cathode tail gas, A2 cathode tail gas and A3 cathode tail gas after heat exchange. The A1 cathode tail gas is input into the burner and mixed with B1 anode tail gas for combustion. The A2 cathode tail gas is discharged after heat exchange. The A3 cathode tail gas is mixed with the tail gas after combustion in the burner and is discharged after providing heat to the vaporization reforming unit.

[0011] The outlet of the fuel supply unit is connected to the vaporization reforming unit and the methanol evaporator respectively, the vaporization reforming unit is connected to the anode inlet of the fuel cell stack, and the methanol evaporator is also connected to the burner;

[0012] The air outputted by the air supply unit is inputted into the cathode inlet of the fuel cell stack after heat exchange.

[0013] As a further improvement, it also includes one or more of an anode tail gas heat exchanger, a cathode tail gas heat exchanger, a combustion tail gas heat exchanger, and a fuel gas heat exchanger;

[0014] The anode tail gas heat exchanger is connected to the anode of the stack, the cathode tail gas heat exchanger is connected to the cathode of the stack, the combustion tail gas heat exchanger is connected to the methanol evaporator and the vaporization reforming unit, and the fuel gas heat exchanger is connected to the vaporization reforming unit and the stack;

[0015] The air output by the air supply unit exchanges heat with one or more of the anode tail gas heat exchanger, the cathode tail gas heat exchanger, the combustion tail gas heat exchanger, and the fuel gas heat exchanger in sequence.

[0016] As a further improvement, the anode tail gas heat exchanger is also connected to an anode tail gas gas-liquid separator, which condenses water vapor in the anode tail gas into liquid water and inputs it into the fuel supply unit. The tail gas output by the anode tail gas gas-liquid separator is divided into B1 anode tail gas and B2 anode tail gas.

[0017] As a further improvement, a gas cooler and a gas mixer are connected in sequence between the gasification reforming unit and the gas heat exchanger.

[0018] As a further improvement, a gas-liquid separator is also connected between the gas cooler and the gas mixer, and the gas-liquid separator condenses the methanol and water vapor in the fuel that are not completely reformed into liquid and inputs it into the fuel supply unit.

[0019] As a further improvement, a heater is also connected between the outlet of the fuel supply unit and the methanol evaporator.

[0020] As a further improvement, it also includes an exhaust gas mixer, and the cathode exhaust gas output from the cathode of the fuel cell stack enters the cathode exhaust gas heat exchanger and is divided into A1 cathode exhaust gas, A2 cathode exhaust gas and A3 cathode exhaust gas after heat exchange; the A2 cathode exhaust gas is input into the gas cooler for heat exchange with the reforming gas discharged from the vaporization reforming unit and then discharged, the A3 cathode exhaust gas enters the burner with the A1 cathode exhaust gas and the B1 anode exhaust gas and then is burned, and the exhaust gas enters the exhaust gas mixer and is mixed, and then is input into the vaporization reforming unit to provide heat for the vaporization reforming unit and then discharged.

[0021] As a further improvement, the calculation method for the distribution of the flow rate of the anode tail gas stream B1 and the anode tail gas stream B2 is:

[0022]

[0023]

[0024] Uf1 is the fuel utilization rate of the fuel stack, which is an inherent parameter of the fuel stack; Uf2 is the required fuel utilization rate of the methanol solid oxide fuel cell system, which is a pre-designed indicator. a is the proportion of the anode tail gas of B2 to the total output anode tail gas, is the mass flow rate of the total output anode tail gas, is the mass flow rate of anode tail gas of stream B1, is the mass flow rate of anode tail gas of stream B2;

[0025] The calculation method of the cathode tail gas flow rate of the A1 stream is:

[0026]

[0027] in, is the mass flow rate of cathode tail gas of stream A1, T B1 is the temperature of the anode tail gas B1 when it enters the burner, T A1 is the temperature of cathode tail gas A1 when it enters the burner, T burner is the required temperature at the burner outlet, h(T B1 ) is the anode tail gas of B1 at temperature T B1 The specific enthalpy (i.e. the enthalpy per unit mass) at A1 ) is the cathode tail gas of A1 at temperature T A1 The specific enthalpy at time, h(T burner ) is the exhaust gas at the burner outlet at temperature T burner The specific enthalpy at q B1 is the calorific value of the anode tail gas from stream B1 (i.e. the heat released by complete combustion of a unit mass of gas);

[0028] The calculation method of the cathode tail gas flow rate of A3 is:

[0029]

[0030] in, is the mass flow rate of cathode tail gas A3, T 21 is the temperature of the burner exhaust gas when it enters the exhaust gas mixer after passing through the exhaust gas heat exchanger, T A3 is the temperature of the cathode exhaust gas A3 when it enters the exhaust gas mixer, T 16 is the required temperature of the gasification reforming unit, h(T 21 ) is the burner exhaust gas at temperature T 21 The specific enthalpy at time, h(T A3 ) is the cathode tail gas of A3 at temperature T A3 The specific enthalpy at time, h(T 16 ) is the exhaust gas mixer exhaust gas at temperature T 16 Specific enthalpy at ;

[0031]

[0032] in, is the mass flow rate of the total output cathode tail gas, is the mass flow rate of cathode tail gas of stream A2.

[0033] As a further improvement, it also includes a first regulating valve, a second regulating valve, a third regulating valve, a fourth regulating valve, a fifth regulating valve, an air flow meter, a first exhaust gas flow meter and a second exhaust gas flow meter;

[0034] The first regulating valve is disposed between the outlet of the fuel supply unit and the vaporization reforming unit, and is used to control the amount of fuel entering the vaporization reforming unit;

[0035] The second regulating valve is arranged between the outlet of the fuel supply unit and the methanol evaporator, and is used to control the amount of fuel entering the methanol evaporator;

[0036] The third regulating valve and the first tail gas flow meter are arranged on the A3 cathode tail gas delivery path, and are used to control and measure the A3 cathode tail gas flow rate respectively;

[0037] The fourth regulating valve and the second tail gas flow meter are arranged on the A2 cathode tail gas delivery path, and are used to control and measure the A2 cathode tail gas flow respectively;

[0038] The fifth regulating valve is arranged on the B2 anode tail gas delivery path and is used to control the flow rate of the B2 anode tail gas;

[0039] The air flow meter is arranged at the outlet of the air supply unit and is used to measure the flow rate of the input air.

[0040] The present invention also provides a methanol solid oxide fuel cell system startup temperature rise control method for controlling the methanol solid oxide fuel cell system.

[0041] When the system starts to heat up, the fuel supply unit outputs methanol, which is heated and evaporated, and then enters the burner through the methanol evaporator for combustion, and the combusted gas is input into the methanol evaporator for vaporizing the subsequently input methanol;

[0042] When the system generates electricity stably, if the gas flow and temperature output by the burner do not meet the requirements, the fuel supply unit outputs methanol to the methanol evaporator to supplement the burner with fuel.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0044] (1) A methanol solid oxide fuel cell system of the present invention diverts the anode tail gas output from the anode of the stack and the cathode tail gas output from the cathode of the stack to different parts, wherein the cathode tail gas A1 and the anode tail gas B1 entering the burner are mixed and burned to further heat up, and at the same time assume the functions of system startup heating and stack tail gas treatment. In addition, the burner is also connected to the methanol evaporator, which provides energy for methanol evaporation during the system startup heating stage. The methanol evaporated in the methanol evaporator can also be input into the burner to supplement the burner during the stable power generation stage. The tail gas that is further heated after combustion in the burner is mixed with the cathode tail gas A3 and provides heat for the vaporization reforming unit. In addition, the diverted tail gas is diverted to different parts for heat exchange. The air output by the air supply unit is heated by heat exchange with the tail gas and then enters the stack, making full use of the system heat and improving the energy utilization rate of the system.

[0045] (2) A methanol solid oxide fuel cell system of the present invention is provided with an anode tail gas gas-liquid separator to condense water vapor in the anode tail gas into liquid water and input it into a fuel supply unit; a fuel gas gas-liquid separator is provided to condense water vapor in the fuel gas of the reforming reaction and unreacted methanol gas into liquid and input them into the fuel supply unit, and the materials input into the fuel supply unit are recycled, thereby achieving the goal of no additional water replenishment during the normal operation of the fuel stack and efficient use of fuel.

[0046] (3) In a methanol solid oxide fuel cell system of the present invention, a heater is used for preheating and evaporating methanol at the initial stage of system startup to avoid direct combustion of liquid methanol and generation of carbon deposits at this stage.

[0047] (4) A methanol solid oxide fuel cell system of the present invention is provided with only one burner, which can be fed with anode tail gas and cathode tail gas. In the stable power generation stage, the mixed gas of anode tail gas and cathode tail gas is burned to provide heat for air and methanol reforming reaction. In addition, the burner is connected to a methanol evaporator, which is connected to a fuel supply unit. In the stable power generation stage, if the burner temperature does not meet the requirements, the methanol evaporated in the methanol evaporator can also be fed into the burner to supplement the burner in the stable power generation stage.

[0048] (5) A methanol solid oxide fuel cell system of the present invention is also provided with various regulating valves and flow meters, and cooperates with the fuel stack fuel pump, the burner fuel pump, and the anode tail gas circulation pump to adjust the fuel supply flow, the flow of different tail gases and the air supply flow.

[0049] (6) A methanol solid oxide fuel cell system startup temperature control method of the present invention provides heat for the methanol reforming reaction by heat exchange and mixing of the fuel cell stack and the burner tail gas. The ratio of the two can be adjusted by adjusting the valve so that the vaporization reforming unit is stably at the temperature required for the reforming reaction. At the same time, the burner flow and temperature are monitored in real time, and the amount of tail gas and fuel entering the burner are adjusted by adjusting the valve and pump to achieve the adjustable burner flow and temperature, thereby avoiding overheating and flameout of the burner. In the startup temperature rise stage, the heater is first used for heating to avoid carbon deposits caused by methanol cracking, simplify the system startup process, and reduce system power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of a methanol solid oxide fuel cell system.

[0051] Description of labels:

[0052] 1. Fuel supply unit; 2. Air supply unit; 3. Heater; 401. Fuel pump for fuel cell stack; 402. Fuel pump for burner; 501. First regulating valve; 502. Second regulating valve; 503. Third regulating valve; 504. Fourth regulating valve; 505. Fifth regulating valve; 601. Air flow meter; 602. First tail gas flow meter; 603. Second tail gas flow meter; 7. Tail gas cooler; 8. Anode tail gas circulation pump; 9. Fuel cell stack; 901. Fuel cell stack anode; 902. Fuel cell stack cathode; 10. Anode tail gas heat exchanger; 11. Cathode tail gas heat exchanger; 12. Combustion tail gas heat exchanger; 13. Gas heat exchanger; 14. Burner; 15. Methanol evaporator; 16. Vaporization reformer; 17. Gas cooler; 18. Gas gas-liquid separator; 19. Anode tail gas-liquid separator; 20. Gas mixer; 21. Tail gas mixer. DETAILED DESCRIPTION

[0053] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0054] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so as to describe the embodiments of the present application described herein.

[0056] The terms "installed", "set", "provided with", and "connected" used in this application should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0057] like Figure 1 As shown, this embodiment provides a methanol solid oxide fuel cell system including a fuel supply unit 1 , an air supply unit 2 , a fuel cell stack 9 , a burner 14 , a methanol evaporator 15 and a vaporization reforming unit 16 .

[0058] Specifically, the stack 9 includes a stack anode 901 and a stack cathode 902. The anode tail gas outputted from the stack anode 901 is divided into B1 anode tail gas and B2 anode tail gas after heat exchange, wherein B1 anode tail gas is input into the burner 14 for combustion, and B2 anode tail gas is returned to the stack 9 for recycling. The cathode tail gas outputted from the stack cathode 902 is divided into A1 cathode tail gas, A2 cathode tail gas and A3 cathode tail gas after heat exchange, A1 cathode tail gas is input into the burner 14 and mixed with B1 anode tail gas for combustion, A2 cathode tail gas is discharged after heat exchange, A3 cathode tail gas is entered into the burner 14, and the tail gas is mixed with A1 cathode tail gas and B1 anode tail gas after combustion and is discharged after heating for the vaporization reforming unit 16. The outlet of the fuel supply unit 1 is connected to the vaporization reforming unit 16 and the methanol evaporator 15 respectively, the vaporization reforming unit 16 is connected to the anode inlet of the stack 9, and the methanol evaporator 15 is also connected to the burner 14. The air output by the air supply unit 2 is input to the cathode inlet of the stack 9 after heat exchange.

[0059] In the present methanol solid oxide fuel cell system, the anode tail gas outputted by the stack anode 901 and the cathode tail gas outputted by the stack cathode 902 are shunted to different parts, wherein the A1 cathode tail gas and the B1 anode tail gas entering the burner 14 are mixed and burned to further heat up, and at the same time assume the functions of system startup heating and stack tail gas treatment. Moreover, the burner 14 is also connected to the methanol evaporator 15, which provides energy for methanol evaporation at the system startup heating stage, and the methanol evaporated in the methanol evaporator 15 can also be input into the burner 14, and the burner 14 is supplemented with combustion in the stable power generation stage. The tail gas further heated up after combustion in the burner 14 is mixed with the A3 cathode tail gas and heats the vaporization reforming unit 16, and the shunted tail gas is shunted to different parts for heat exchange, and the air outputted by the air supply unit 2 enters the stack 9 after heat exchange and heating with the tail gas, so as to make full use of the system heat and improve the energy utilization rate of the system.

[0060] In addition, the methanol solid oxide fuel cell system further includes one or more of an anode tail gas heat exchanger 10, a cathode tail gas heat exchanger 11, a combustion tail gas heat exchanger 12, and a gas heat exchanger 13. When the anode tail gas heat exchanger 10 is included, the anode tail gas heat exchanger 10 is connected to the anode 901 of the stack. When the cathode tail gas heat exchanger 11 is included, the cathode tail gas heat exchanger 11 is connected to the cathode 902 of the stack. When the combustion tail gas heat exchanger 12 is included, the combustion tail gas heat exchanger 12 is connected to the methanol evaporator 15 and the vaporization reforming unit 16. When the gas heat exchanger 13 is included, the gas heat exchanger 13 is connected to the vaporization reforming unit 16 and the stack 9. The air output by the air supply unit 2 is sequentially heat exchanged with one or more of the anode tail gas heat exchanger 10, the cathode tail gas heat exchanger 11, the combustion tail gas heat exchanger 12, and the gas heat exchanger 13.

[0061] In this embodiment, the methanol solid oxide fuel cell system further includes an anode tail gas heat exchanger 10, a cathode tail gas heat exchanger 11, a combustion tail gas heat exchanger 12 and a gas heat exchanger 13 for specific description. In this case, the anode tail gas heat exchanger 10 is connected to the anode 901 of the stack and the air supply unit 2, the cathode tail gas heat exchanger 11 is connected to the anode tail gas heat exchanger 10 and the cathode 902 of the stack, the combustion tail gas heat exchanger 12 is connected to the cathode tail gas heat exchanger 11, the methanol evaporator 15 and the vaporization reforming unit 16, and the gas heat exchanger 13 is connected to the combustion tail gas heat exchanger 12, the vaporization reforming unit 16 and the stack 9. The air output by the air supply unit 2 is sequentially heat-exchanged with the anode tail gas heat exchanger 10, the cathode tail gas heat exchanger 11, the combustion tail gas heat exchanger 12 and the gas heat exchanger 13, and then input into the cathode inlet of the stack 9.

[0062] As a further improvement, the anode tail gas heat exchanger 10 is also connected to the anode tail gas-liquid separator 19. The stack 9 in this solution is a SOFC stack, and the anode tail gas mainly includes H2, CO, CO2 and water vapor. The anode tail gas-liquid separator 19 condenses the water vapor in the anode tail gas into liquid water and inputs it into the fuel supply unit 1. The anode tail gas output by the anode tail gas-liquid separator 19 is divided into B1 anode tail gas and B2 anode tail gas. The liquid water input into the fuel supply unit 1 here provides liquid water for the reforming reaction of the fuel supply unit 1, thereby recycling the liquid water.

[0063] Preferably, a gas cooler 17 and a gas mixer 20 are connected in sequence between the gasification reforming unit 16 and the gas heat exchanger 13. Furthermore, a gas gas-liquid separator 18 is connected between the gas cooler 17 and the gas mixer 20, and the gas gas-liquid separator 18 condenses the methanol and water vapor in the fuel that have not been completely reformed into liquid and inputs it into the fuel supply unit 1. In this scheme, the gas gas-liquid separator 18 first condenses the water vapor into liquid water and then inputs it into the fuel supply unit 1, and the liquid water condensed in the anode tail gas gas-liquid separator 19 is also input into the fuel supply unit 1, so that the water in the system is recycled, and there is no need to add water to the methanol reforming reaction in the fuel supply unit 1 during the normal operation of the fuel stack.

[0064] As a preferred embodiment, a heater 3 is also connected between the outlet of the fuel supply unit 1 and the methanol evaporator 15. During the system startup and temperature rise phase, the methanol output by the fuel supply unit 1 enters the heater 3, and after the methanol is vaporized in the heater 3, it enters the burner 14 through the methanol evaporator 15 for combustion. After the burner 14 burns, the tail gas is passed into the methanol evaporator 15 to heat the methanol that enters later. After the system combustion is stable, the burner 14 replaces the heater 3 to perform the function of methanol vaporization. Specifically, the heater 3 can be an electric heater, but other types of heaters can also be used in other ways.

[0065] In order to improve the utilization rate of exhaust gas heat, the methanol solid oxide fuel cell system also includes an exhaust gas mixer 21. The cathode exhaust gas output by the stack cathode 902 enters the cathode exhaust gas heat exchanger 11 for heat exchange and is divided into A1 cathode exhaust gas, A2 cathode exhaust gas and A3 cathode exhaust gas; the A2 cathode exhaust gas is input into the gas cooler 17 for heat exchange with the reformed gas discharged from the vaporization reforming unit 16 and then discharged, that is, the A2 cathode exhaust gas is used to cool the reformed gas, and the A3 cathode exhaust gas enters the burner 14 with the A1 cathode exhaust gas and the B1 anode exhaust gas. After combustion, the exhaust gas enters the exhaust mixer 21 for mixing and is input into the vaporization reforming unit 16 for heat supply to the vaporization reforming unit 16 and then is discharged.

[0066] Specifically, in the anode tail gas heat exchanger 10, cathode tail gas heat exchanger 11, combustion tail gas heat exchanger 12 and gas heat exchanger 13, the air output by the air supply unit 2 is sequentially heat-exchanged with the anode tail gas, cathode tail gas, tail gas after combustion and gas in the burner 14 and then input into the fuel cell stack 9. In the gas mixer 20, the anode tail gas B2 is returned and mixed with the gas obtained by the reforming reaction and then enters the gas heat exchanger 13, where it is preheated by the air input from the combustion tail gas heat exchanger 12 and enters the fuel cell stack 9, where the anode tail gas B2 is recycled. Regarding the gas cooler 17, the tail gas cooler 7 is also connected between the gas cooler 17 and the cathode tail gas heat exchanger 11. After the cathode tail gas A2 enters the tail gas cooler 7 and is cooled, it is passed into the gas cooler 17 as a cooling gas to cool the reforming gas entering the gas cooler 17, so that the unreacted methanol and water vapor in the reforming gas are condensed, and then the cathode tail gas A2 is finally discharged from the system through the gas cooler 17. The tail gas cooler 7 can be an air-cooled or water-cooled radiator to cool the cathode tail gas A2 from 100 to 200°C to room temperature. In the vaporization reforming unit 16, the tail gas mixed by the tail gas mixer 21 is input into the vaporization reforming unit 16 to provide heat for the vaporization reforming unit 16. Specifically, a fuel cell stack fuel pump 401 is also arranged between the fuel supply unit 1 and the vaporization reforming unit 16. The methanol aqueous solution output by the fuel supply unit 1 is pumped into the vaporization reforming unit 16 through the fuel cell stack fuel pump 401. The vaporization reforming unit 16 contains a copper-based catalyst required for the reforming reaction. The tail gas introduced by the tail gas mixer 21 provides heat for the vaporization and reforming reactions. Methanol and water are converted into a mixed gas of hydrogen and carbon monoxide, etc. in the vaporization reforming unit 16, which is used as fuel gas for the fuel cell stack reaction. The fuel gas is then introduced into the fuel gas cooler 17 for cooling. The methanol and water vapor that are not completely reacted in the fuel gas are condensed into liquid. The fuel gas and liquid are separated in the fuel gas-liquid separator 18, and the liquid flows back to the vaporization reforming unit 16. The remaining fuel gas enters the fuel gas mixer 20. In the fuel gas mixer 20, the reformed fuel gas is mixed with the recycled B2 anode tail gas, enters the fuel gas heat exchanger 13, is preheated by air, and then enters the fuel cell stack 9.

[0067] In the present invention, the calculation method for the distribution of the flow rate of the anode tail gas stream B1 and the anode tail gas stream B2 is:

[0068]

[0069] Uf1 is the fuel utilization rate of the fuel stack, which is an inherent parameter of the fuel stack; Uf2 is the required fuel utilization rate of the methanol solid oxide fuel cell system, which is a pre-designed indicator. a is the proportion of the anode tail gas of B2 to the total output anode tail gas, is the mass flow rate of the total output anode tail gas, is the mass flow rate of anode tail gas of stream B1, is the mass flow rate of anode tail gas of stream B2.

[0070] The calculation method of the cathode tail gas flow rate of the A1 stream is:

[0071]

[0072] in, is the mass flow rate of cathode tail gas of stream A1, T B1 is the temperature of the anode tail gas B1 when it enters the burner 14, T A1 is the temperature of the cathode tail gas A1 when it enters the burner 14, T burner is the required temperature at the burner 14 outlet, h(T B1 ) is the anode tail gas of B1 at temperature T B1 The specific enthalpy (i.e. the enthalpy per unit mass) at A1 ) is the cathode tail gas of A1 at temperature T A1 The specific enthalpy at time, h(T burner ) is the exhaust gas at the burner outlet at temperature T burner The specific enthalpy at q B1 It is the calorific value of the anode tail gas of stream B1 (i.e. the heat released by the complete combustion of unit mass of gas).

[0073] The calculation method of the cathode tail gas flow rate of A3 is:

[0074]

[0075] in, is the mass flow rate of cathode tail gas A3, T 21 is the temperature of the burner exhaust gas when it enters the exhaust gas mixer 21 after passing through the exhaust gas heat exchanger 12, T A3 is the temperature of the cathode tail gas A3 when it enters the tail gas mixer 21, T 16 is the required temperature of the gasification reforming unit 16, h(T 21 ) is the burner exhaust gas at temperature T 21 The specific enthalpy at time, h(T A3 ) is the cathode tail gas of A3 at temperature T A3 The specific enthalpy at time, h(T 16 ) is the exhaust gas from the exhaust mixer 21 at temperature T 16 The specific enthalpy at .

[0076]

[0077] in, is the mass flow rate of the total output cathode tail gas, is the mass flow rate of cathode tail gas of stream A2.

[0078] As a further improvement, the methanol solid oxide fuel cell system further includes a first regulating valve 501, a second regulating valve 502, a third regulating valve 503, a fourth regulating valve 504, a fifth regulating valve 505, an air flow meter 601, a first tail gas flow meter 602 and a second tail gas flow meter 603. Specifically, the first regulating valve 501 is arranged between the outlet of the fuel supply unit 1 and the vaporization reforming unit 16, and is used to control the amount of fuel entering the vaporization reforming unit 16. The second regulating valve 502 is arranged between the outlet of the fuel supply unit 1 and the methanol evaporator 15, and is used to control the amount of fuel entering the methanol evaporator 15. The third regulating valve 503 and the first tail gas flow meter 602 are arranged on the A3 cathode tail gas delivery path, and are respectively used to control and measure the A3 cathode tail gas flow. The fourth regulating valve 504 and the second tail gas flow meter 603 are arranged on the A2 cathode tail gas delivery path, and are respectively used to control and measure the A2 cathode tail gas flow. The fifth regulating valve 505 is arranged on the anode tail gas delivery path of the B2 stream, and is used to control the flow rate of the anode tail gas of the B2 stream. The air flow meter 601 is arranged at the outlet of the air supply unit 2, and is used to measure the flow rate of the input air.

[0079] In addition, a burner fuel pump 402 is provided between the fuel supply unit 1 and the heater 3. In the stable power generation stage of the system, when the exhaust gas flow rate and temperature at the outlet of the burner 14 do not meet the requirements, the burner fuel pump 402 can be turned on to supplement the methanol fuel to the burner 14. An anode tail gas circulation pump 8 is also provided between the anode tail gas-liquid separator 19 and the gas mixer 20 to pump the B2 anode tail gas into the gas mixer 20 after boosting the pressure and mixing it with the reforming gas.

[0080] The present invention also provides a methanol solid oxide fuel cell system startup temperature control method, which is used to control the methanol solid oxide fuel cell system. Specifically, when the system starts to heat up, the methanol output by the fuel supply unit 1 is heated and evaporated, and then enters the burner 14 through the methanol evaporator 15 for combustion, and the gas after combustion is input into the methanol evaporator 15 for vaporizing the methanol input subsequently. When the system is generating electricity stably, if the gas flow rate and temperature output by the burner 14 do not meet the requirements, the fuel supply unit 1 outputs methanol to the methanol evaporator 15 to supplement the burner 14 with fuel.

[0081] Combination Figure 1 As shown, the detailed steps of the methanol solid oxide fuel cell system startup temperature rise control method are as follows:

[0082] 1. Close the first regulating valve 501, the second regulating valve 502, the third regulating valve 503, the fourth regulating valve 504, and the fifth regulating valve 505, and open the air supply unit 2 to input air. The air flow rate supplied is Qa:

[0083] 2. Turn on heater 3 for preheating, so that the outlet temperature of heater 3 reaches the specified temperature of 200°C;

[0084] 3. Open the second regulating valve 502 and the burner fuel pump 402, set the methanol flow rate entering the burner 14 to Qf1 through the second regulating valve 502 and the burner fuel pump 402, and ignite the burner 14 at the same time;

[0085] 4. Monitor the outlet temperature of the burner 14 and the outlet temperature of the methanol evaporator 15. When the outlet temperature of the burner 14 reaches the preset stable temperature of 300°C and the outlet temperature of the methanol evaporator 15 reaches the preset stable temperature of 200°C, turn off the heater 3;

[0086] 5. Keep the air flow rate Qa unchanged, gradually increase the methanol fuel flow rate Qf1, and heat up the fuel cell stack 9, the tail gas mixer 21, and the vaporization reformer 16;

[0087] 6. Monitor the outlet temperature of the tail gas mixer 21 and when it reaches 350°C, stop increasing the methanol fuel flow rate Qf1, keep the flow rate Qf1 unchanged, increase the air flow rate Qa, and open and adjust the third regulating valve 503 and the fourth regulating valve 504 at the same time to ensure that the outlet temperature of the burner 14 remains unchanged, the outlet temperature of the tail gas mixer 21 remains at 350°C, and the outlet temperature of the gas cooler 17 remains at 60°C;

[0088] 7. Monitor the inlet temperature of the vaporization reforming unit 16 to reach 300° C. Open the first regulating valve 501 and the stack fuel pump 401. Set the methanol flow rate entering the vaporization reforming unit 16 to Qf2 through the first regulating valve 501 and the stack fuel pump 401. At the same time, adjust the flow rate Qf1 to ensure that the outlet temperature of the burner 14 remains unchanged.

[0089] 8. The flow rate Qf1 is gradually reduced to 0 through the second regulating valve 502 and the burner fuel pump 402, and the flow rate Qf2 is increased through the first regulating valve 501 and the stack fuel pump 401. In this process, the outlet temperature of the burner 14 is kept unchanged, the inlet temperature of the vaporization reforming unit 16 is kept at 300°C, and the outlet temperature of the gas cooler 17 is kept at 60°C;

[0090] 9. Continue to increase the fuel flow rate Qf2 and adjust the air flow rate Qa synchronously to ensure that the inlet temperature of the vaporization reforming unit 16 is maintained at 300°C and the outlet temperature of the gas cooler 17 is maintained at 60°C. The stack 9 is heated at the set temperature rise rate until the stack 9 reaches the specified temperature;

[0091] 10. After the fuel cell stack meets the power generation status requirements, current loading is performed and the system enters the stable power generation stage; in the stable power generation stage, if it is detected that the gas flow rate and outlet temperature output by the burner 14 do not meet the requirements, the fuel supply unit 1 promptly outputs methanol to the methanol evaporator 15 to supplement the burner 14 with fuel.

[0092] Regarding the above flow setting, real-time control and adjustment are carried out according to the temperature requirements of each location, and the temperature requirements are set manually. The temperature detection can be monitored by setting a temperature sensor at the outlet or inlet of each component.

[0093] The control method in this scheme provides heat for the methanol reforming reaction by heat exchange and mixing of the cathode tail gas of the stack 9 and the tail gas of the burner 14. The ratio of the two can be adjusted by adjusting the valve so that the vaporization reforming unit 16 is stably at the temperature required for the reforming reaction. At the same time, the flow rate and temperature of the burner 14 are monitored in real time, and the amount of tail gas and fuel entering the burner 14 are adjusted by adjusting the valve and pump to achieve the adjustable flow rate and temperature of the burner 14, avoiding overheating and flameout of the burner 14. After the anode tail gas of the stack and the reforming reaction gas are cooled, the water vapor and fuel therein can be condensed and circulated to the fuel supply unit 1, realizing the efficient use of fuel without additional water replenishment during the normal operation of the stack. In the startup and heating stage, the heater 3 is first used for heating, which avoids the carbon deposits produced by methanol cracking, simplifies the system startup process, and reduces the system power consumption.

[0094] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A methanol solid oxide fuel cell system, characterized in that: It comprises a fuel supply unit (1), an air supply unit (2), a fuel cell stack (9), a burner (14), a methanol evaporator (15) and a vaporization reforming unit (16); The cell stack (9) comprises a cell stack anode (901) and a cell stack cathode (902); the anode tail gas outputted from the cell stack anode (901) is divided into a B1 anode tail gas and a B2 anode tail gas after heat exchange; the B1 anode tail gas is inputted into the burner (14) for combustion, and the B2 anode tail gas is returned and inputted into the cell stack (9); The cathode tail gas outputted from the stack cathode (902) is divided into A1 cathode tail gas, A2 cathode tail gas and A3 cathode tail gas after heat exchange, the A1 cathode tail gas is input into the burner (14) and mixed with B1 anode tail gas for combustion, the A2 cathode tail gas is discharged after heat exchange, and the A3 cathode tail gas is mixed with the tail gas after combustion in the burner (14) and is discharged after providing heat to the vaporization reforming unit (16); The outlet of the fuel supply unit (1) is connected to the vaporization reforming unit (16) and the methanol evaporator (15) respectively, the vaporization reforming unit (16) is connected to the anode inlet of the fuel cell stack (9), and the methanol evaporator (15) is also connected to the burner (14); The air output by the air supply unit (2) is input into the cathode inlet of the fuel cell stack (9) after heat exchange.

2. The methanol solid oxide fuel cell system according to claim 1, characterized in that: It also includes one or more of an anode tail gas heat exchanger (10), a cathode tail gas heat exchanger (11), a combustion tail gas heat exchanger (12), and a fuel gas heat exchanger (13); The anode tail gas heat exchanger (10) is connected to the anode (901) of the stack, the cathode tail gas heat exchanger (11) is connected to the cathode (902) of the stack, the combustion tail gas heat exchanger (12) is connected to the methanol evaporator (15) and the vaporization reforming unit (16), and the fuel gas heat exchanger (13) is connected to the vaporization reforming unit (16) and the stack (9); The air output by the air supply unit (2) sequentially exchanges heat with one or more of the anode tail gas heat exchanger (10), the cathode tail gas heat exchanger (11), the combustion tail gas heat exchanger (12), and the fuel gas heat exchanger (13).

3. The methanol solid oxide fuel cell system according to claim 2, characterized in that: The anode tail gas heat exchanger (10) is also connected to an anode tail gas gas-liquid separator (19), and the anode tail gas gas-liquid separator (19) condenses water vapor in the anode tail gas into liquid water and inputs the liquid water into the fuel supply unit (1). The tail gas output by the anode tail gas gas-liquid separator (19) is divided into a B1 anode tail gas and a B2 anode tail gas.

4. The methanol solid oxide fuel cell system according to claim 2, characterized in that: A gas cooler (17) and a gas mixer (20) are also connected in sequence between the gasification reforming unit (16) and the gas heat exchanger (13).

5. The methanol solid oxide fuel cell system according to claim 4, characterized in that: A gas-liquid separator (18) is also connected between the gas cooler (17) and the gas mixer (20), and the gas-liquid separator (18) condenses methanol and water vapor in the fuel that have not been completely reformed into liquid and then inputs the liquid into the fuel supply unit (1).

6. The methanol solid oxide fuel cell system according to claim 4, characterized in that: A heater (3) is also connected between the outlet of the fuel supply unit (1) and the methanol evaporator (15).

7. The methanol solid oxide fuel cell system according to claim 4, characterized in that: It also includes an exhaust gas mixer (21), and the cathode exhaust gas output by the cathode of the battery stack (902) enters the cathode exhaust gas heat exchanger (11) for heat exchange and is divided into A1 cathode exhaust gas, A2 cathode exhaust gas and A3 cathode exhaust gas; the A2 cathode exhaust gas is input into the fuel gas cooler (17) for heat exchange with the reforming gas discharged from the vaporization reforming unit (16) and then discharged; the A3 cathode exhaust gas enters the burner (14) with the A1 cathode exhaust gas and the B1 anode exhaust gas and is burned. The exhaust gas enters the exhaust gas mixer (21) and is mixed. The exhaust gas is then input into the vaporization reforming unit (16) to provide heat for the vaporization reforming unit (16) and then discharged.

8. The methanol solid oxide fuel cell system according to claim 7, characterized in that: The calculation method for the distribution of the anode tail gas flow of B1 and B2 is: Uf1 is the fuel utilization rate of the fuel stack, which is an inherent parameter of the fuel stack; Uf2 is the required fuel utilization rate of the methanol solid oxide fuel cell system, which is a pre-designed indicator. a is the proportion of the anode tail gas of B2 to the total output anode tail gas, is the mass flow rate of the total output anode tail gas, is the mass flow rate of anode tail gas of stream B1, is the mass flow rate of anode tail gas of stream B2; Preferably, the calculation method of the A1 cathode tail gas flow rate is: in, is the mass flow rate of cathode tail gas of stream A1, T B1 is the temperature of the anode tail gas B1 when it enters the burner (14), T A1 is the temperature of cathode tail gas A1 when it enters the burner (14), T burner is the required temperature at the burner (14) outlet, h(T B1 ) is the anode tail gas of B1 at temperature T B1 The specific enthalpy at time, h(T A1 ) is the cathode tail gas of A1 at temperature T A1 The specific enthalpy at time, h(T burner ) is the exhaust gas at the burner outlet at temperature T burner The specific enthalpy at q B1 is the calorific value of the anode tail gas of B1; Preferably, the calculation method of the cathode tail gas flow rate of A3 is: in, is the mass flow rate of cathode tail gas A3, T 21 is the temperature of the burner exhaust gas after passing through the exhaust gas heat exchanger (12) and entering the exhaust gas mixer (21), T A3 is the temperature of the cathode tail gas A3 when it enters the tail gas mixer (21), T 16 is the required temperature of the vaporization reforming unit (16), h(T 21 ) is the burner exhaust gas at temperature T 21 The specific enthalpy at time, h(T A3 ) is the cathode tail gas of A3 at temperature T A3 The specific enthalpy at time, h(T 16 ) is the exhaust gas from the exhaust gas mixer (21) at temperature T 16 Specific enthalpy at ; in, is the mass flow rate of the total output cathode tail gas, is the mass flow rate of cathode tail gas of stream A2.

9. The methanol solid oxide fuel cell system according to any one of claims 1 to 8, characterized in that: It also includes at least one of a first regulating valve (501), a second regulating valve (502), a third regulating valve (503), a fourth regulating valve (504), a fifth regulating valve (505), an air flow meter (601), a first exhaust gas flow meter (602) and a second exhaust gas flow meter (603); The first regulating valve (501) is arranged between the outlet of the fuel supply unit (1) and the vaporization reforming unit (16), and is used to control the amount of fuel entering the vaporization reforming unit (16); The second regulating valve (502) is arranged between the outlet of the fuel supply unit (1) and the methanol evaporator (15), and is used to control the amount of fuel entering the methanol evaporator (15); The third regulating valve (503) and the first tail gas flow meter (602) are arranged on the A3 cathode tail gas delivery path, and are used to control and measure the A3 cathode tail gas flow rate, respectively; The fourth regulating valve (504) and the second tail gas flow meter (603) are arranged on the A2 cathode tail gas delivery path, and are used to control and measure the A2 cathode tail gas flow rate, respectively; The fifth regulating valve (505) is arranged on the B2 anode tail gas delivery path and is used to control the flow rate of the B2 anode tail gas; The air flow meter (601) is arranged at the outlet of the air supply unit (2) and is used to measure the flow rate of the input air.

10. A method for controlling the temperature rise during the start-up of a methanol solid oxide fuel cell system, characterized in that: Used to control the methanol solid oxide fuel cell system according to any one of claims 1 to 9, When the system starts to heat up, the fuel supply unit (1) outputs methanol, which is heated and evaporated, and then enters the burner (14) through the methanol evaporator (15) for combustion, and the gas after combustion is input into the methanol evaporator (15) for vaporizing the methanol input subsequently; When the system generates electricity stably, if the gas flow rate and temperature output by the burner (14) do not meet the requirements, the fuel supply unit (1) outputs methanol to the methanol evaporator (15) to supplement the fuel for the burner (14).

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