Methanol reforming fuel cell heat and power cogeneration system and control method

Abstract

The invention is suitable for the technical field of fuel cell heat and power cogeneration, and provides a methanol reforming fuel cell heat and power cogeneration system and a control method, and the methanol reforming fuel cell heat and power cogeneration system comprises a power supply module and a heat supply module; the power supply module comprises a methanol reforming fuel cell system used for catalytic combustion heating and reforming hydrogen production power generation; the energy storage cell is connected with the methanol reforming fuel cell system; the heat supply module comprises a heat exchanger which is connected with the methanol reforming fuel cell system and is used for exchanging heat and heating cold water; the water buffer tank is connected with the heat exchanger to form a circulating water path to continuously heat the water; and the hot water tank is connected with the water buffer tank and is used for supplying hot water to the outside. Chemical energy of the system is converted into electric energy to charge the energy storage battery, high-temperature waste gas at the temperature of about 170 DEG C generated by the system is subjected to heat exchange through the heat exchanger to supply heat to users, cascade application of energy is achieved, and the energy utilization efficiency of the whole system is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell cogeneration, and in particular relates to a methanol reforming fuel cell cogeneration system and a control method. Background Art

[0002] The fuel cell cogeneration system is an energy utilization system that organically combines hydrogen production, hot water supply and power generation processes. It makes full use of the waste heat from hydrogen production and power generation, greatly improves energy utilization, and has good economic benefits. The existing technology discloses that the pure power generation efficiency of fuel cells is about 50%, while the comprehensive efficiency through cogeneration can reach more than 85%. The cogeneration method allows hydrogen fuel cells to generate electricity for buildings while the waste heat can be recovered for heating and hot water. Compared with traditional thermal power generation and transmission, the overall efficiency is increased by about 2 times.

[0003] However, the difficulty in storing and transporting hydrogen is the key factor restricting the widespread application of hydrogen energy, and also affects the application of hydrogen fuel cell cogeneration systems. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a methanol reforming fuel cell cogeneration system, aiming to solve the problems raised in the above background technology.

[0005] The embodiment of the present invention is implemented as follows: a methanol reforming fuel cell cogeneration system includes a power supply module and a heating module; Wherein, the power supply module comprises: Methanol reforming fuel cell system, used for catalytic combustion heating and reforming hydrogen production and power generation; an energy storage battery connected to the methanol reforming fuel cell system; The heating module comprises: A heat exchanger connected to the methanol reforming fuel cell system for exchanging heat to heat cold water; The water buffer tank is connected to the heat exchanger to form a circulating water circuit to continuously heat the water; The hot water tank is connected to the water buffer tank and is used to supply hot water to the outside.

[0006] Preferably, the heating module further comprises: Water pump 1, connected between the heat exchanger and the water buffer tank, used to circulate the hot water in the water buffer tank to the heat exchanger to continuously increase the temperature; The second water pump is connected between the water buffer tank and the hot water tank and is used for introducing hot water into the hot water tank.

[0007] Preferably, the system further comprises a monitoring module for monitoring the voltage and power parameters of the energy storage battery, the operating status of the methanol reforming fuel cell system, the liquid level status of the water buffer tank and the hot water tank, the water temperature, and the water flow rate.

[0008] Preferably, the monitoring module includes: Liquid level sensor 1, connected to the water buffer tank; Liquid level sensor 2, connected to the hot water tank; The temperature sensor 3 is connected between the water pump 1 and the water buffer tank, and is used to monitor the outlet water temperature of the water buffer tank; Temperature sensor 4, connected between the heat exchanger and the water buffer tank, for monitoring the inlet water temperature of the water buffer tank; Temperature sensor five, installed on the water inlet pipe of the heat exchanger, used to monitor the temperature of the introduced cold water; a temperature sensor six, connected between the water buffer tank and the water pump two, for monitoring the water temperature in the water buffer tank; The temperature sensor seven is installed in the hot water tank and is used to monitor the water temperature in the hot water tank.

[0009] Preferably, the monitoring module further includes: Temperature sensor 1, connected between the methanol reforming fuel cell system and the heat exchanger, for monitoring the high-temperature exhaust gas temperature; Temperature sensor 2 is connected to the exhaust pipe of the heat exchanger and is used to monitor the exhaust gas temperature after heat exchange.

[0010] Another object of the embodiment of the present invention is to provide a control method for a methanol reforming fuel cell cogeneration system, comprising the following steps: Obtain the energy storage battery voltage and hot water tank liquid level status; Control the start and stop of the methanol reforming fuel cell system based on the energy storage battery voltage and hot water tank liquid level status information; Obtain required heat according to water temperature, liquid level status, and water flow status; The operating state of the methanol reforming fuel cell system is controlled according to the required heat information.

[0011] Preferably, the step of controlling the start and stop of the methanol reforming fuel cell system based on the energy storage battery voltage and the hot water tank liquid level status information is specifically as follows: When the energy storage battery is full, the methanol reforming fuel cell system is controlled to stop generating electricity; when the hot water tank is at a low liquid level or the water temperature is lower than the set value, electricity is taken from the energy storage battery to maintain the temperature of the hot water tank, or the methanol reforming fuel cell system is controlled to be in the methanol catalytic combustion heating mode to provide heat for the hot water tank; When the energy storage battery is not full, the methanol reforming fuel cell system is controlled to start generating electricity; when the hot water tank is at a high liquid level, there is no need to add water. According to the water temperature of the hot water tank, the working state of the methanol reforming fuel cell system is adjusted. When the water temperature is greater than or equal to the set value, the heating module is stopped, and the high-temperature exhaust gas generated by the methanol reforming fuel cell system is directly discharged into the atmosphere through the heat exchanger; when the hot water tank is at a low liquid level or the water temperature is lower than the set value, electricity is taken from the energy storage battery to maintain the temperature of the hot water tank, or the methanol reforming fuel cell system is controlled to be in the methanol catalytic combustion heating mode to provide heat for the hot water tank.

[0012] A methanol reforming fuel cell cogeneration system is provided in an embodiment of the present invention, wherein the methanol reforming fuel cell system includes a methanol reforming hydrogen production reactor, a high-temperature proton exchange membrane fuel cell, a fuel storage and control module, etc., using methanol water as fuel, and methanol and water undergo a reforming reaction under medium and low temperature conditions to generate hydrogen-rich synthesis gas. In a kilowatt-level high-temperature proton exchange membrane fuel cell, the stack uses high-temperature resistant heat transfer oil to achieve stack heat exchange, and the system thermal balance is achieved by using a fan to force heat exchange on the heat transfer oil. The chemical energy of the system synthesis gas is converted into electrical energy to charge the energy storage battery. The high-temperature exhaust gas of about 170°C generated by the system is heat exchanged through a heat exchanger to heat cold water to provide heating and heat supply for users, thereby realizing the cascade application of energy, taking into account the user's electricity and hot water needs, and realizing automatic liquid replenishment control of the hot water tank, which can meet the user's water needs in the entire temperature range, and improving the energy utilization efficiency of the entire system, which can be increased to 85%, solving the problem of difficulty in hydrogen energy storage and transportation, and realizing efficient and clean utilization of methanol fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A block diagram of a methanol reforming fuel cell cogeneration system provided by an embodiment of the present invention; Figure 2 A flow chart of a control method for a methanol reforming fuel cell cogeneration system provided by an embodiment of the present invention; Figure 3 A control main logic diagram of a methanol reforming fuel cell cogeneration system provided by an embodiment of the present invention; Figure 4 This is a curve showing how the 55°C hot water flow and overall efficiency of a 5kW methanol reforming fuel cell cogeneration system vary with the operating status of the fuel cell provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0016] like Figure 1 As shown, it is a block diagram of a methanol reforming fuel cell cogeneration system provided by an embodiment of the present invention, comprising: a power supply module and a heating module; Wherein, the power supply module comprises: Methanol reforming fuel cell system is used for catalytic combustion heating and reforming hydrogen generation. The electricity can be used to charge energy storage batteries, directly charged into the power grid, and also to supply power to loads. an energy storage battery connected to the methanol reforming fuel cell system; The heating module comprises: A heat exchanger connected to the methanol reforming fuel cell system for exchanging heat to heat cold water; The water buffer tank is connected to the heat exchanger to form a circulating water circuit to continuously heat the water; A hot water tank, connected to the water buffer tank, is used to supply hot water to the outside; The heat exchanger adopts a tube-fin heat exchanger, in which water flows through the tube side. The high-temperature exhaust gas generated by the methanol reforming fuel cell system is heat-exchanged through the fins, and the generated hot water is circulated to the water buffer tank. The low-temperature exhaust gas after heat exchange is directly discharged into the atmosphere. The temperature sensor 1 monitors the temperature T1 of the high-temperature exhaust gas, and the temperature sensor 2 monitors the temperature T2 of the exhaust gas after heat exchange. The water pump 1 P1 connects the heat exchanger and the water buffer tank. Through P1, the water in the water buffer tank is circulated to the heat exchanger and continuously heated. When the temperature sensor 6 monitors that the water temperature T6 in the water buffer tank reaches the user-set value, the hot water is introduced into the hot water tank through the water pump 2 P2 for standby use; Liquid level sensor 1 and liquid level sensor 2 are respectively installed on the water buffer tank and the hot water tank to realize liquid level monitoring; at the same time, the heating module is arranged with temperature sampling points T3, T4, T5, and T7, and temperature sensor 3, temperature sensor 4, temperature sensor 5, and temperature sensor 7 are respectively used to monitor the water buffer tank outlet water temperature T3, the water buffer tank inlet water temperature T4, the cold water temperature T5, and the hot water tank water temperature T7.

[0017] like Figure 2 FIG. 1 is a flow chart of a control method for a methanol reforming fuel cell cogeneration system according to an embodiment of the present invention, comprising the following steps: Obtain the energy storage battery voltage and hot water tank liquid level status; Control the start and stop of the methanol reforming fuel cell system based on the energy storage battery voltage and hot water tank liquid level status information; Obtain required heat according to water temperature, liquid level status, and water flow status; Control the operating state of the methanol reforming fuel cell system according to the required heat information; The main control logic diagram of the system is as follows Figure 3 As shown, the cogeneration system needs to monitor the status of both the power supply and heating modules at the same time. For the power supply module, it mainly monitors the voltage and power parameters of the energy storage battery and the operating status of the methanol reforming fuel cell system; for the heating module, it mainly monitors the liquid level status, water temperature, flow rate, circulation pump status and other information of the water buffer tank and the hot water tank. By obtaining the energy storage battery voltage and the hot water tank liquid level status, the methanol reforming fuel cell system is controlled to start and stop based on the energy storage battery voltage and the hot water tank liquid level status information. Specifically: When the energy storage battery is full, the methanol reforming fuel cell system stops generating electricity; if the hot water tank is not full at this time, that is, the hot water tank is monitored to be at a low liquid level or the hot water tank temperature T7 is less than the user-set value, power can be drawn from the energy storage battery to maintain the hot water tank temperature by auxiliary electric heating, or the methanol reforming fuel cell system can be controlled to be in a methanol catalytic combustion heating mode to provide heat to the hot water tank; When the energy storage battery is not full, the methanol reforming fuel cell power generation state is adjusted to provide electricity and heat to the user; at this time, if the hot water tank is full, that is, when the liquid level sensor 2 is detected to be at a high liquid level, there is no need to add water. According to the water temperature T7 of the hot water tank, the working state of the methanol reforming fuel cell system is adjusted. When T7 ≥ the user set value, the heating module is stopped, and the high-temperature exhaust gas generated by the methanol reforming fuel cell system is directly discharged into the atmosphere after passing through the heat exchanger; when the hot water tank is not full, the user can choose between two working modes: electric accompanying and thermal accompanying. According to the user's selection, the methanol reforming fuel cell system automatically matches the operating state.

[0018] The operating state of the methanol reforming fuel cell system corresponds to different power generation currents. Under different states, the fuel inflow, system energy efficiency, and system calorific value are calculated according to the following formula: Fuel cell power generation = power generation current × stack voltage; System energy efficiency = fuel cell power generation / total power provided by liquid fuel; The total power provided by the liquid fuel = the amount of liquid fuel × the calorific value of the fuel. The system uses methanol as fuel, and the calorific value of methanol is 638.514 kJ / mol (1 atm LHV at room temperature); System thermal power = total power provided by the incoming liquid fuel × (1-system energy efficiency); Required heat = (specific heat of water × flow rate × water temperature difference) / heat utilization rate, where the specific heat capacity of water is 4.2kJ / (kg℃); the system controls a fixed circulating water flow rate, and its flow rate is set slightly higher than the flow rate corresponding to a 30℃ rise in circulating water temperature at the rated power point of the methanol reforming fuel cell system to ensure system safety; water temperature difference = user set temperature - cold water temperature; the heat exchanger efficiency is measured in experiments, generally between 70 and 75%, and the system can be set to 72%.

[0019] The automatic water replenishment control method of the methanol reforming fuel cell cogeneration system is as follows: according to user needs, the system adopts the order of replenishing the water buffer tank first and then replenishing the hot water tank to realize automatic liquid replenishment of the system, that is, the status of the liquid level sensor 1 and the liquid level sensor 2 is detected at the same time. When it is detected that the liquid level sensor 1 is at a low liquid level, the solenoid valve is opened, and the cold water is replenished to the water buffer tank after passing through the heat exchanger; at this time, the water in the water buffer tank is stored in the hot water tank through the water pump 2 P2 after heat exchange, and this cycle is repeated until the hot water tank is full; the working state of the water pump 2 P2 is determined by the parameters and state of T6 and the liquid level sensor 2: when the two conditions of T6> the set value and the detection of the liquid level sensor 2 at a low liquid level are met at the same time, the water pump 2 P2 is started, that is, the user can realize the simultaneous replenishment of the water buffer tank and the hot water tank by reducing the set value of T6.

[0020] Taking the methanol reforming fuel cell cogeneration system with a rated power of 5kW as an example, the working process of the system is explained: By using the system and control method of the embodiment of the present invention, a 5kW methanol reforming fuel cell cogeneration system can provide nearly 100L / h 55℃ hot water, and the system comprehensive energy efficiency reaches 85%. Figure 4 As shown, its specific module structure and operation are as follows; Module structure: The 5Kw methanol reforming fuel cell cogeneration system consists of two modules: power supply and heat supply. The energy storage battery in the power supply module uses but is not limited to ternary lithium batteries, lead-acid batteries, etc. The voltage range is 42~58V, and the power is designed to be 5kWh; the maximum power of the methanol reforming fuel cell system is 5kW, and the rated power is 3.7kW; The rated heat exchange capacity of the heat exchanger in the heating module is 3kW, the volume of the water buffer tank is 60L, and the hot water tank is an electrically heated water tank with a volume of 200L; Liquid level sensors 1 and 2 are integrated with the system control to form a liquid level monitoring module that monitors the water level value in real time through a pressure transmitter; Considering the resistance of the heat exchanger, high-lift and high-flow pumps are selected for water pump 1 P1 and water pump 2 P2. This system uses 16-meter head, adjustable speed water pumps with a maximum temperature resistance of 110°C and a maximum flow rate of 25L / min. The heating module pipeline adopts four-branch pipe connection, and the system temperature sampling points T1~T7 are respectively fixed at the connection between the pipeline and the heat exchanger, water buffer tank, and hot water tank to ensure accurate temperature sampling; Operation status: The 5kW methanol reforming fuel cell cogeneration system is started, and the control system simultaneously monitors the power supply and heating modules, sets the hot water target temperature (55°C), obtains the energy storage battery voltage, hot water tank temperature / liquid level status, realizes automatic water replenishment, and switches the methanol reforming fuel cell operation status; When the lithium battery is not fully charged (voltage is between 42 and 57.5 V) and the hot water tank is not full (the liquid level sensor 2 is detected to be at a low level), the methanol reforming fuel cell provides power for the load, and the surplus power is charged to the lithium battery; the high-temperature exhaust gas generated by the system is passed into the heat exchanger, and at the same time, the water pump P1 starts to start, and its water flow rate is designed based on the following: The rated power of the 5kW methanol reforming fuel cell system is 3.7kW, and the corresponding fuel-electric state (stack current) is 50A. The measured fuel methanol water inflow at this state point is 2.75kg / h; The total power provided by the liquid fuel = 2.75kg / h*1000g / kg*0.543 / (32g / mol)*638.514(kJ / mol) / (3600s / h)=8.276kW (where the methanol mass fraction in the fuel is 54.3%); Energy efficiency of fuel-electric system = 3.7 / 8.276*100 = 44.7%; System thermal power = 8.276 × (1-44.7%) = 4.49 kW; Water flow rate = 4.49 kJ / s × 0.72 / 30 °C / (4.2 kJ / kg °C) × 3600 s / h = 92.3 L / h (calculated based on heat recovery efficiency of 72%, water temperature difference of 30 °C, and water specific heat capacity of 4.2 kJ / kg °C); Therefore, to ensure the safety of the system, the water flow rate of pump 1 P1 is set at 100L / h; After multiple cycles of heat exchange, when the water temperature T6 is monitored to rise to 55°C, the water pump P2 pumps the hot water in the water buffer tank into the hot water tank at a speed of 100L / h for standby use; When the liquid level sensor 2 is detected to be at a high liquid level and T7 ≥ 55°C, the water pump 1 P1 and water pump 2 P2 of the heating module stop working, and the high-temperature exhaust gas generated by the methanol reforming fuel cell system is directly discharged into the atmosphere after passing through the heat exchanger; When the lithium battery is fully charged (voltage ≥ 57.5V) and the hot water tank is not full (the liquid level sensor 2 is detected to be at a low level), there are two ways to obtain hot water: (1) switch the methanol reforming fuel cell system to standby mode, that is, use catalytic combustion to maintain the system temperature but not generate electricity, and use the waste heat from catalytic combustion to heat the water; (2) the electric hot water tank draws power from the lithium battery to heat the water. By comparison, it is found that the first method is more energy-saving and environmentally friendly; When the lithium battery and the hot water tank are fully charged, the entire combined heat and power system can be stopped.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A methanol reforming fuel cell cogeneration system, characterized in that: It includes a power supply module and a heating module; Wherein, the power supply module comprises: Methanol reforming fuel cell system, used for catalytic combustion heating and reforming hydrogen production and power generation; an energy storage battery connected to the methanol reforming fuel cell system; The heating module comprises: A heat exchanger connected to the methanol reforming fuel cell system for exchanging heat to heat cold water; The water buffer tank is connected to the heat exchanger to form a circulating water circuit to continuously heat the water; The hot water tank is connected to the water buffer tank and is used to supply hot water to the outside.

2. The methanol reforming fuel cell cogeneration system according to claim 1, characterized in that: The heating module also includes: Water pump 1, connected between the heat exchanger and the water buffer tank, used to circulate the hot water in the water buffer tank to the heat exchanger to continuously increase the temperature; The second water pump is connected between the water buffer tank and the hot water tank and is used for introducing hot water into the hot water tank.

3. The methanol reforming fuel cell cogeneration system according to claim 2, characterized in that: The system also includes a monitoring module for monitoring the voltage and power parameters of the energy storage battery, the operating status of the methanol reforming fuel cell system, the liquid level status of the water buffer tank and the hot water tank, the water temperature, and the water flow rate.

4. The methanol reforming fuel cell cogeneration system according to claim 3, characterized in that: The monitoring module comprises: Liquid level sensor 1, connected to the water buffer tank; Liquid level sensor 2, connected to the hot water tank; The temperature sensor 3 is connected between the water pump 1 and the water buffer tank, and is used to monitor the outlet water temperature of the water buffer tank; Temperature sensor 4, connected between the heat exchanger and the water buffer tank, for monitoring the inlet water temperature of the water buffer tank; Temperature sensor five, installed on the water inlet pipe of the heat exchanger, used to monitor the temperature of the introduced cold water; a temperature sensor six, connected between the water buffer tank and the water pump two, for monitoring the water temperature in the water buffer tank; The temperature sensor seven is installed in the hot water tank and is used to monitor the water temperature in the hot water tank.

5. The methanol reforming fuel cell cogeneration system according to claim 3, characterized in that: The monitoring module also includes: Temperature sensor 1, connected between the methanol reforming fuel cell system and the heat exchanger, for monitoring the high-temperature exhaust gas temperature; Temperature sensor 2 is connected to the exhaust pipe of the heat exchanger and is used to monitor the exhaust gas temperature after heat exchange.

6. A control method for a methanol reforming fuel cell cogeneration system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Obtain the energy storage battery voltage and hot water tank liquid level status; Control the start and stop of the methanol reforming fuel cell system based on the energy storage battery voltage and hot water tank liquid level status information; Obtain required heat according to water temperature, liquid level status, and water flow status; The operating state of the methanol reforming fuel cell system is controlled according to the required heat information.

7. The control method according to claim 6, characterized in that: The steps of controlling the start and stop of the methanol reforming fuel cell system based on the energy storage battery voltage and the hot water tank liquid level status information are specifically as follows: When the energy storage battery is full, the methanol reforming fuel cell system is controlled to stop generating electricity; when the hot water tank is at a low liquid level or the water temperature is lower than the set value, electricity is taken from the energy storage battery to maintain the temperature of the hot water tank, or the methanol reforming fuel cell system is controlled to be in the methanol catalytic combustion heating mode to provide heat for the hot water tank; When the energy storage battery is not full, the methanol reforming fuel cell system is controlled to start generating electricity; when the hot water tank is at a high liquid level, there is no need to add water. According to the water temperature of the hot water tank, the working state of the methanol reforming fuel cell system is adjusted. When the water temperature is greater than or equal to the set value, the heating module is stopped, and the high-temperature exhaust gas generated by the methanol reforming fuel cell system is directly discharged into the atmosphere through the heat exchanger; when the hot water tank is at a low liquid level or the water temperature is lower than the set value, electricity is taken from the energy storage battery to maintain the temperature of the hot water tank, or the methanol reforming fuel cell system is controlled to be in the methanol catalytic combustion heating mode to provide heat for the hot water tank.

Images