High-temperature PEM fuel cell waste heat refrigerating system and method based on heat integration

Abstract

The invention discloses a high-temperature PEM fuel cell waste heat refrigeration system and method based on heat integration. The system comprises a high-temperature PEM fuel cell unit and an absorption refrigeration unit, the high-temperature PEM fuel cell unit comprises a fuel cell pack; the absorption refrigeration unit comprises a generator, a condenser, an evaporator, an absorber, a pump, a first valve and a second valve; according to the invention, the waste heat of the high-temperature PEM fuel cell is recycled, the cooling medium of the high-temperature PEM fuel cell is recycled, and refrigeration without extra energy input is realized. And the energy utilization rate of the high-temperature PEM fuel cell is further improved. The effect of the high-temperature PEM fuel cell waste heat refrigerating system is compared with the effect of the low-temperature PEM fuel cell waste heat refrigerating system, so that the requirements in different scenes are met. According to the invention, efficient recovery and utilization of waste heat of the high-temperature PEM fuel cell can be realized, the waste heat recovery amount and the refrigerating capacity are greatly improved, and the energy efficiency of the whole system is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells and refrigeration, and in particular relates to a high-temperature PEM fuel cell waste heat refrigeration system and method based on heat integration. Background Art

[0002] Hydrogen is considered to be the main form of energy system for multi-purpose applications in the future because it can be used as an energy carrier and storage medium in fuel cells, as well as a fuel, and provides a carbon-free solution. As global energy consumption increases, requirements for different types of energy consumption are also being put forward, so the development of cogeneration systems based on fuel cells will become more meaningful.

[0003] Low-temperature PEM fuel cells, the fastest-growing fuel cell technology, have relatively low operating temperatures and use of precious metal electrodes, which place high demands on hydrogen concentration. High-temperature PEM fuel cells, on the other hand, can operate at temperatures up to 200°C, enabling them to process reformate gases containing small amounts of carbon monoxide, thereby overcoming some of the limitations of PEM fuel cells in terms of fuel purity.

[0004] From an application perspective, efficient utilization of high-temperature PEM waste heat can significantly improve overall system energy efficiency, making it more competitive in sectors such as distributed energy and industrial heating. By developing novel system integration solutions, not only can high waste heat recovery rates be achieved, but system operating costs can also be significantly reduced. Establishing a comprehensive waste heat utilization evaluation system in the future will be of great practical significance for promoting the commercial application of high-temperature PEM technology. Summary of the Invention

[0005] Purpose of the Invention: The present invention provides a high-temperature PEM fuel cell waste heat cooling system and method based on heat integration. This system recovers waste heat from the high-temperature PEM fuel cell, simultaneously recycling its cooling medium and providing refrigeration without requiring additional energy input. This improves the energy efficiency of the high-temperature PEM fuel cell.

[0006] Technical solution: A high-temperature PEM fuel cell waste heat refrigeration system based on heat integration of the present invention includes a high-temperature PEM fuel cell unit and an absorption refrigeration unit, wherein the high-temperature PEM fuel cell unit includes a fuel cell group; the fuel cell group includes input streams of hydrogen and air, output streams of unreacted mixed gas, and output electricity and circulating coolant, the input stream of hydrogen is connected to the first inlet of the fuel cell group, the input stream of air is connected to the second inlet of the fuel cell group, the output stream of unreacted mixed gas is connected to the first outlet of the fuel cell group, the output electricity is connected to the second outlet of the fuel cell group, the circulating coolant input stream is connected to the third inlet of the fuel cell group, and the circulating coolant output stream is connected to the third outlet of the fuel cell group; the absorption refrigeration unit includes a generator, a condenser, an evaporator, an absorber, a pump, a first valve, and a second valve. The first inlet of the generator is connected to the third outlet of the fuel cell group, and the The first outlet of the generator is connected to the third inlet of the fuel cell group, the second outlet of the generator is connected to the first inlet of the condenser, the second inlet of the generator is connected to the outlet of the pump, the third outlet of the generator is connected to the inlet of the second valve, the first outlet of the condenser is connected to the inlet of the first valve, the second inlet of the condenser is connected to the condenser cooling water input, the second outlet of the condenser is connected to the condenser cooling water output, the outlet of the first valve is connected to the first inlet of the evaporator, the second inlet of the evaporator is connected to the evaporator chilled water input, the first outlet of the evaporator is connected to the first inlet of the absorber, the second outlet of the evaporator is connected to the evaporator chilled water output, the second inlet of the absorber is connected to the outlet of the second valve, the third inlet of the absorber is connected to the absorber condensed water input, the first outlet of the absorber is connected to the inlet of the pump, and the second outlet of the absorber is connected to the absorber cooling water output.

[0007] Furthermore, the high-temperature PEM fuel cell waste heat cooling system directly exchanges heat between the high-temperature PEM fuel cell coolant and the absorption cooling steam generator through heat integration, thereby achieving efficient utilization of waste heat.

[0008] Furthermore, the high-temperature PEM fuel cell waste heat cooling system mainly includes two parts: power generation and cooling.

[0009] Furthermore, the high-temperature PEM fuel cell waste heat cooling system is an independent system that can simultaneously have the functions of power generation and cooling.

[0010] Furthermore, the coolant of the high-temperature PEM fuel cell unit of the high-temperature PEM fuel cell waste heat cooling system no longer exchanges heat with other cooling systems, but exchanges heat with the steam generator of the absorption refrigeration unit, and is indirectly recovered through heat integration, thereby reducing the cooling energy consumption of the high-temperature PEM fuel cell unit and realizing the recovery and utilization of the remaining heat.

[0011] Furthermore, the steam generator of the absorption refrigeration unit of the high-temperature PEM fuel cell waste heat refrigeration system no longer consumes additional heat and is driven only by waste heat, thereby reducing refrigeration energy consumption.

[0012] Furthermore, the evaporator of the absorption refrigeration unit of the high-temperature PEM fuel cell waste heat refrigeration system can achieve an external refrigeration function by absorbing heat through evaporation of the refrigerant in the absorption refrigeration unit.

[0013] The present invention also discloses a refrigeration cycle method based on a high-temperature PEM fuel cell waste heat refrigeration system, comprising the following steps:

[0014] Step 1: Heat generation process:

[0015] During the heat generation process of the high-temperature PEM fuel cell unit, hydrogen and air enter the fuel cell stack through the first and second inlets, respectively, to undergo an electrochemical reaction. The unreacted mixed gas is discharged through the first outlet of the fuel cell stack, and the generated electricity is output from the second outlet of the fuel cell stack. The heat generated during the reaction is carried by the coolant entering the fuel cell stack through the third inlet and discharged from the third outlet of the fuel cell stack by the coolant.

[0016] Step 2: Waste heat recovery refrigeration process:

[0017] In the waste heat recovery refrigeration process of the absorption refrigeration unit, the waste heat generated by the fuel cell stack is carried out from the coolant output from the third outlet of the fuel cell stack and enters from the first inlet of the generator, and then after heat exchange with the refrigerant from the pump outlet, it enters the third inlet of the fuel cell stack 1 from the coolant input from the first outlet of the generator, and the refrigerant liquid phase enters the inlet of the second valve from the refrigeration cycle stream from the third outlet of the generator, and enters the absorber from the second inlet of the absorber after pressure release, and the refrigerant gas phase enters the condenser from the second outlet of the generator from the refrigeration cycle stream through the first inlet of the condenser, and then exchanges heat with the condenser cooling water input from the second inlet of the condenser, the cooled refrigerant flows out from the refrigeration cycle stream from the first outlet of the condenser, and the condenser cooling water after heat exchange flows out from the second outlet of the condenser by the condenser cooling water output, and then It enters the first valve through the inlet of the first valve, expands and releases the pressure, and then flows out from the outlet of the first valve through the refrigeration cycle stream to the first outlet of the evaporator. After heat exchange and evaporation with the evaporator chilled water input from the second inlet of the evaporator, it flows out from the first outlet of the evaporator from the refrigeration cycle stream to the first inlet of the absorber. The cooled chilled water flows out from the evaporator chilled water output from the second outlet of the evaporator, and undergoes absorption reaction with the absorbent liquid phase that has been depressurized from the second inlet of the absorber. The heat of the reaction is input by the absorber condensed water and enters from the third inlet of the absorber, and is taken out from the second outlet of the absorber by the absorber condensed water output. The mixed liquid after the absorption reaction flows out from the first outlet of the absorber from the refrigeration cycle stream to the first inlet of the pump. After being pressurized, it flows out from the refrigeration cycle stream from the pump outlet to the second inlet of the generator, completing the refrigeration cycle.

[0018] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: The present invention utilizes an absorption refrigeration system to realize heat recovery and utilization, especially for the high-temperature waste heat of high-temperature PEM fuel cells. Under the condition of a certain amount of heat supply, the higher-quality fuel cell stack coolant can be used to heat the evaporator of the refrigeration system. This not only realizes the recycling of the fuel cell stack coolant, but also can use the high-temperature PEM fuel coolant to drive the refrigeration system, greatly improving the energy utilization rate of the entire system and further improving the operating performance of the system. The effects of the high-temperature PEM fuel cell waste heat refrigeration system and the low-temperature PEM fuel cell waste heat refrigeration system are compared to meet the needs of different scenarios. The present invention can realize the efficient recovery and utilization of the waste heat of the high-temperature PEM fuel cell, greatly improve the waste heat recovery amount and cooling capacity, and effectively improve the energy efficiency of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a high-temperature PEM fuel cell waste heat cooling system based on heat integration according to an embodiment of the present invention.

[0020] Reference numerals:

[0021] Fuel cell stack 1, generator 2, condenser 3, evaporator 4, absorber 5, pump 6, first valve 7, second valve 8, hydrogen S1, air S2, unreacted mixed gas S3, electricity S4, coolant input S5, coolant output S6, refrigeration circulation stream S7-S14, condenser cooling water input S16, condenser cooling water output S17, evaporator chilled water input S17, evaporator chilled water output S18, absorber cooling water input S19, absorber cooling water output S20.

[0022] Figure 2 This is the waste heat recovery diagram.

[0023] Figure 3 Energy efficiency diagram. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] A high-temperature PEM fuel cell waste heat refrigeration system based on heat integration according to an embodiment of the present invention includes a high-temperature PEM fuel cell unit and an absorption refrigeration unit, wherein the high-temperature PEM fuel cell unit includes a fuel cell stack 1. The fuel cell stack includes input streams of hydrogen S1 and air S2, output streams of unreacted mixed gas S3 and electricity S4, and circulating coolant S5-S6, the input stream of hydrogen S1 is connected to the first inlet of the fuel cell stack 1, the input stream of air S2 is connected to the second inlet of the fuel cell stack 1, the output stream of unreacted mixed gas S3 is connected to the first outlet of the fuel cell stack 1, the output electricity S4 is connected to the second outlet of the fuel cell stack 1, the circulating coolant input stream S5 is connected to the third inlet of the fuel cell stack 1, and the circulating coolant output stream S6 is connected to the third outlet of the fuel cell stack 1; the absorption refrigeration unit includes a generator 2, a condenser 3, an evaporator 4, an absorber 5, a pump 6, a first valve 7, and a second valve 8. The first inlet of the generator 2 is connected to the third outlet of the fuel cell stack 1, the first outlet of the generator 2 is connected to the third inlet of the fuel cell stack 1, and the second outlet of the generator 2 is connected to the condenser. The first inlet of the generator 3 is connected, the second inlet of the generator 2 is connected to the outlet of the pump 6, the third outlet of the generator 2 is connected to the inlet of the second valve 8, the first outlet of the condenser 2 is connected to the inlet of the first valve 7, the second inlet of the condenser 3 is connected to the condenser cooling water input S15, the second outlet of the condenser 3 is connected to the condenser cooling water output S16, the outlet of the first valve 7 is connected to the first inlet of the evaporator 4, the second inlet of the evaporator 4 is connected to the evaporator chilled water input S17, the first outlet of the evaporator 4 is connected to the first inlet of the absorber 5, the second outlet of the evaporator 4 is connected to the evaporator chilled water output S18, the second inlet of the absorber 5 is connected to the outlet of the second valve 8, the third inlet of the absorber 5 is connected to the absorber condensed water input S19, the first outlet of the absorber is connected to the inlet of the pump 6, and the second outlet of the absorber is connected to the absorber cooling water output S20.

[0026] The following describes in detail the working process of a high-temperature PEM fuel cell waste heat cooling system based on heat integration according to the above embodiment of the present invention. Figure 1 The working process of a high-temperature PEM fuel cell waste heat refrigeration system based on heat integration can be divided into a heat generation process and a waste heat recovery refrigeration process. In the heat generation process of the high-temperature PEM fuel cell unit, hydrogen S1 and air S2 enter the first and second inlets of the fuel cell stack 1 respectively to produce an electrochemical reaction. The unreacted mixed gas S3 is discharged through the first outlet of the fuel cell stack 1, and the generated electricity S4 is output from the second outlet of the fuel cell stack 1. The heat generated in the reaction process is taken out from the third inlet of the fuel cell stack 1 by the coolant S5 and is taken out from the third outlet of the fuel cell stack 1 by the coolant output S6.

[0027] In the waste heat recovery refrigeration process of the absorption refrigeration unit, the waste heat generated by the fuel cell stack 1 is taken out from the third outlet of the fuel cell stack 1 from the coolant output S6 and enters from the first inlet of the generator 2, and then after heat exchange with the refrigerant S12 from the outlet of the pump 6, it enters the third inlet of the fuel cell stack 1 from the first outlet of the generator 2 from the coolant input S5, and the refrigerant liquid phase enters the inlet of the second valve 8 from the third outlet of the generator 2 from the refrigeration circulation stream S13, and enters the absorber 5 from the second inlet of the absorber 5 after pressure release. The refrigerant gas phase enters the condenser 3 from the second outlet of the generator 2 from the refrigeration circulation stream S7 through the first inlet of the condenser 3, and then exchanges heat with the condenser cooling water input S15 from the second inlet of the condenser 3. The cooled refrigerant flows out from the first outlet of the condenser 3 from the refrigeration circulation stream S8, and the condenser cooling water after heat exchange flows out from the second outlet of the condenser 3 from the condenser cooling water output S17, and then passes. It enters the first valve 7 through the inlet of the first valve 7, and after expansion and pressure release, it flows out from the outlet of the first valve through the refrigeration cycle stream S9 to the first outlet of the evaporator 4, and after heat exchange and evaporation with the evaporator chilled water input S17 from the second inlet of the evaporator 2, it flows out from the first outlet of the evaporator 4 from the refrigeration cycle stream S10 to the first inlet of the absorber 5. The cooled chilled water flows out from the second outlet of the evaporator 2 from the evaporator chilled water output S18, and undergoes absorption reaction with the absorbent liquid phase whose pressure has been released from the second inlet of the absorber 5. The heat of the reaction enters from the third inlet of the absorber 5 by the absorber condensed water input S19, and is taken out from the second outlet of the absorber 5 by the absorber condensed water output S20. The mixed liquid after the absorption reaction flows out from the first outlet of the absorber 5 from the refrigeration cycle stream S11 to the first inlet of the pump 6. After being pressurized, it flows out from the outlet of the pump 6 from the refrigeration cycle stream S12 to the second inlet of the generator 2, completing the refrigeration cycle.

[0028] See also Figure 2 and Figure 3 The present invention carries out a calculation example to compare the effects of a high-temperature PEM fuel cell waste heat cooling system with a low-temperature PEM fuel cell waste heat cooling system, including the following steps:

[0029] Referring to the operating conditions described in Table 1, in the absorption refrigeration unit, the ambient temperature is 20°C, the absorber temperature is 30°C, the condenser temperature is 44°C, the expansion valve pressure drop is 8 kPa, and the throttle valve pressure drop is 8 kPa; in the PEM fuel cell stack, the high-temperature PEM fuel cell coolant temperature is 150°C, and the low-temperature PEM fuel cell coolant temperature is 80°C.

[0030] Under the working conditions described in Table 1, the waste heat recovery and cooling capacity of the high-temperature PEM fuel cell waste heat cooling system and the low-temperature PEM fuel cell waste heat cooling system are compared. Figure 2As shown in Figure 2, compared with the low-temperature PEM fuel cell waste heat cooling system, the high-temperature PEM fuel cell waste heat cooling system can recover 8.94 times the waste heat and generates 14.58 times the cooling capacity. Efficiency comparison Figure 3 As shown in Figure 2, the energy efficiency of the high-temperature PEM fuel cell waste heat cooling system is improved by 38.68% compared with the low-temperature PEM fuel cell waste heat cooling system. Efficiency increased by 2.51%.

[0031] Table 1

[0032]

[0033] In the description of the present invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the quantity of the technical features indicated. Therefore, a feature specified as "first," "second," or "third" may explicitly or implicitly include one or more of such features. "Multiple" means two or more, unless otherwise specifically defined.

[0034] In the present invention, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0036] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A high-temperature PEM fuel cell waste heat cooling system based on heat integration, characterized in that: Includes high-temperature PEM fuel cell unit and absorption refrigeration unit; Wherein, the high temperature PEM fuel cell unit comprises a fuel cell stack (1); The fuel cell stack (1) comprises input streams of hydrogen and air, and output streams of unreacted mixed gas, electricity, and circulating coolant; the input stream of hydrogen is connected to a first inlet of the fuel cell stack (1), the input stream of air is connected to a second inlet of the fuel cell stack (1), the output stream of unreacted mixed gas is connected to a first outlet of the fuel cell stack (1), the output electricity is connected to a second outlet of the fuel cell stack (1), the circulating coolant input stream is connected to a third inlet of the fuel cell stack (1), and the circulating coolant output stream is connected to a third outlet of the fuel cell stack (1); The absorption refrigeration unit comprises a generator (2), a condenser (3), an evaporator (4), an absorber (5), a pump (6), a first valve (7), and a second valve (8); The first inlet of the generator (2) is connected to the third outlet of the fuel cell group (1), the first outlet of the generator (2) is connected to the third inlet of the fuel cell group (1), the second outlet of the generator (2) is connected to the first inlet of the condenser (3), the second inlet of the generator (2) is connected to the outlet of the pump (6), the third outlet of the generator (2) is connected to the inlet of the second valve (8), the first outlet of the condenser (3) is connected to the inlet of the first valve (7), the second inlet of the condenser (3) is connected to the condenser cooling water input, and the second outlet of the condenser (3) is connected to the condenser. The first valve (7) is connected to the first inlet of the evaporator (4), the second inlet of the evaporator (4) is connected to the evaporator chilled water input, the first outlet of the evaporator (4) is connected to the first inlet of the absorber (5), the second outlet of the evaporator (4) is connected to the evaporator chilled water output, the second inlet of the absorber (5) is connected to the outlet of the second valve (8), the third inlet of the absorber (5) is connected to the absorber condensed water input, the first outlet of the absorber is connected to the inlet of the pump (6), and the second outlet of the absorber is connected to the absorber cooling water output.

2. A high-temperature PEM fuel cell waste heat cooling system based on heat integration according to claim 1, characterized in that: The circulating coolant of the high-temperature PEM fuel cell unit directly exchanges heat with the evaporator of the absorption refrigeration part.

3. The high-temperature PEM fuel cell waste heat cooling system based on heat integration according to claim 1, characterized in that: The high-temperature PEM fuel cell waste heat cooling system based on heat integration is an independent system that has both power generation and cooling functions.

4. A high-temperature PEM fuel cell waste heat cooling system based on heat integration according to claim 1, characterized in that: The steam generator of the absorption refrigeration part is driven only by waste heat generated by the high-temperature PEM fuel cell, without consuming additional energy.

5. A refrigeration cycle method based on the high-temperature PEM fuel cell waste heat refrigeration system according to claim 1, characterized in that: The steps include: Step 1: Heat generation process: During the heat generation process of the high-temperature PEM fuel cell unit, hydrogen and air enter the fuel cell stack through the first and second inlets, respectively, to undergo an electrochemical reaction. The unreacted mixed gas is discharged through the first outlet of the fuel cell stack, and the generated electricity is output from the second outlet of the fuel cell stack. The heat generated during the reaction is carried by the coolant entering the fuel cell stack through the third inlet and discharged from the third outlet of the fuel cell stack by the coolant. Step 2: Waste heat recovery refrigeration process: In the waste heat recovery refrigeration process of the absorption refrigeration unit, the waste heat generated by the fuel cell stack is carried out from the coolant output from the third outlet of the fuel cell stack and enters from the first inlet of the generator, and then after heat exchange with the refrigerant from the pump outlet, it enters the third inlet of the fuel cell stack 1 from the coolant input from the first outlet of the generator, and the refrigerant liquid phase enters the inlet of the second valve from the refrigeration cycle stream from the third outlet of the generator, and enters the absorber from the second inlet of the absorber after pressure release, and the refrigerant gas phase enters the condenser from the second outlet of the generator from the refrigeration cycle stream through the first inlet of the condenser, and then exchanges heat with the condenser cooling water input from the second inlet of the condenser, the cooled refrigerant flows out from the refrigeration cycle stream from the first outlet of the condenser, and the condenser cooling water after heat exchange flows out from the second outlet of the condenser by the condenser cooling water output, and then It enters the first valve through the inlet of the first valve, expands and releases the pressure, and then flows out from the outlet of the first valve through the refrigeration cycle stream to the first outlet of the evaporator. After heat exchange and evaporation with the evaporator chilled water input from the second inlet of the evaporator, it flows out from the first outlet of the evaporator from the refrigeration cycle stream to the first inlet of the absorber. The cooled chilled water flows out from the evaporator chilled water output from the second outlet of the evaporator, and undergoes absorption reaction with the absorbent liquid phase that has been depressurized from the second inlet of the absorber. The heat of the reaction is input by the absorber condensed water and enters from the third inlet of the absorber, and is taken out from the second outlet of the absorber by the absorber condensed water output. The mixed liquid after the absorption reaction flows out from the first outlet of the absorber from the refrigeration cycle stream to the first inlet of the pump. After being pressurized, it flows out from the refrigeration cycle stream from the pump outlet to the second inlet of the generator, completing the refrigeration cycle.

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