A high-efficiency methanol reforming fuel cell power generation method and system based on normal-temperature PEMFC

Abstract

The application relates to a high-efficiency methanol reforming fuel cell power generation method and system based on normal-temperature PEMFC, and belongs to the technical field of fuel cells. The high-efficiency methanol reforming fuel cell power generation method based on normal-temperature PEMFC takes methanol solution and high-purity methanol as input, and comprises the following steps: the methanol solution is directly introduced into an anode of a fuel cell after being reformed and purified; the high-purity methanol is subjected to a catalytic combustion reaction, and reaction heat is used for methanol solution reforming; air is directly introduced into a cathode of the fuel cell after being pressurized and humidified; and a cooling working medium is used for fuel cell cooling after being pressurized. The application retains the advantages of the normal-temperature PEMFC system, such as high power density, compact structure, rapid starting and the like, and has the characteristics of the high-temperature HPEMFC system, such as high stability, high overall machine efficiency and system simplification, can be used in more fields and under the environment with higher power generation power grade requirement, and has good low-temperature storage and starting adaptability.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology and relates to a high-efficiency methanol reforming fuel cell power generation method and system based on ambient temperature PEMFC. Background Technology

[0002] Hydrogen energy, as a clean and efficient energy source, boasts high energy density, is storable and transportable, has wide availability, and produces only water as a byproduct, resulting in zero pollution and zero carbon emissions. It is gradually becoming a global trend in the future energy sector. Hydrogen production, storage, and fuel cell technologies, as core technologies for hydrogen energy utilization, are of paramount importance in the development of hydrogen energy technology.

[0003] In recent years, alcohol reforming for hydrogen production has become a focus of attention in hydrogen energy production and storage. Methanol reforming proton exchange membrane fuel cell (PEMFC) technology has also emerged as a relatively feasible and safe hydrogen power generation technology. The principle of a methanol reforming PEMFC power generation system is as follows: methanol is reformed to obtain crude hydrogen, which is then purified to obtain pure hydrogen. This pure hydrogen is then passed through a PEMFC (proton exchange membrane fuel cell) to generate electricity. Based on operating temperature, PEMFCs can be classified into ambient temperature PEMFCs and high-temperature PEMFCs.

[0004] Room-temperature PEMFCs offer high power density, large power output per stack, rapid start-up, and compact power generation units. However, their system and process control are more complex, and they suffer from low reliability due to low CO tolerance, significant internal energy consumption, and low overall thermal and electrical efficiency. High-temperature HPEMFCs offer even higher overall electrical efficiency, exceeding 45%. However, limitations in membrane electrode technology currently restrict their power density, resulting in very limited power output per stack. Integrating them into large systems or hydrogen fuel cell engines may require multiple stacks, leading to a bulky system. Furthermore, high-temperature operation is accompanied by longer start-up times. Both types of PEMFCs share challenges related to low-temperature storage and the difficulty of starting at low temperatures, necessitating the use of energy storage batteries. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a high-efficiency methanol reforming fuel cell power generation system based on ambient temperature PEMFC, addressing at least one of the following technical problems: 1. Existing ambient temperature PEMFC power generation systems suffer from low overall thermal efficiency and are prone to poisoning; 2. High-temperature HPEMFC systems have low power density and are relatively bulky; 3. Both systems face common challenges such as low-temperature storage and difficulty in low-temperature start-up, requiring the use of energy storage batteries. This invention is applicable to applications with power levels of 10–30 kW and above, such as hydrogen fuel cell vehicles, large-scale combined heat and power plants, and emergency power supply systems.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] On one hand, this invention provides a high-efficiency methanol reforming fuel cell power generation method based on a room-temperature PEMFC, using methanol solution and high-purity methanol as inputs, including:

[0008] The methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell;

[0009] High-purity methanol undergoes catalytic combustion, and the heat of reaction is used for methanol solution reforming.

[0010] Air is pressurized and humidified before being directly introduced into the cathode of the fuel cell.

[0011] The cooling medium is pressurized and then used to cool the fuel cell.

[0012] Furthermore, the methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell, including: pressurizing, cooling, vaporizing and heating the methanol solution to the reforming temperature to obtain crude reformed gas; the crude reformed gas undergoes low-temperature conversion to obtain crude purified gas; the crude purified gas is cooled and subjected to a PROX reaction to obtain refined purified gas; and the refined purified gas is buffered and directly fed into the anode of the fuel cell for electrochemical reaction.

[0013] Furthermore, the high-purity methanol undergoes a catalytic combustion reaction, which includes the high-purity methanol being pressurized, vaporized, and heated before being combusted with fuel cell exhaust gas.

[0014] Furthermore, the high-purity methanol undergoes a catalytic combustion reaction to produce high-temperature combustion flue gas, which is divided into a first branch and a second branch.

[0015] The high-temperature combustion flue gas from the first branch is used to provide heat for the reforming of the methanol solution;

[0016] The high-temperature combustion flue gas from the second branch is used to heat the cooling medium in the cooling unit.

[0017] Furthermore, the cooling medium, after being pressurized, is used for cooling the fuel cell, including:

[0018] After being pressurized, the cooling medium is supplied to the fuel cell and the intercooler respectively. The cooling medium can be recycled through the cooling unit. The cooling medium exchanges heat with the high-temperature combustion flue gas generated by the catalytic combustion reaction of high-purity methanol through the second heat exchanger. The cooled medium after heat exchange heats the fuel cell stack, enabling the system to start at room temperature and low temperature.

[0019] Furthermore, the system's ability to start at room temperature and low temperature includes:

[0020] The high-temperature combustion flue gas in the second branch is used to heat and cool the working medium. The working medium is regulated by starting the second heat exchanger. The second heat exchanger is connected in parallel with an electric heater to achieve temperature regulation and meet the start-up conditions at normal and low temperatures.

[0021] Furthermore, the air, after being pressurized and humidified, is directly introduced into the cathode of the fuel cell, including:

[0022] After passing through compression, boosting, and intercooler, the air is divided into three branches;

[0023] The first branch is the main air path. After humidification, it enters the cathode of the fuel cell to carry out electrochemical reaction. The high humidity cathode tail gas produced is used to humidify the air again. At the same time, it is mixed with the refined gas and the anode tail gas produced after the reaction of the fuel cell anode. The mixed tail gas is heated and used as an oxidant to react with high-purity methanol. Meanwhile, the electrochemical reaction product liquid water carried out by the cathode gas is separated and discharged.

[0024] The second branch air participates in the purification reaction of the crude purified gas;

[0025] The third air path is the Air Bleed air path, which, after being fully mixed with the refined gas, enters the fuel cell anode together to participate in the reaction.

[0026] Furthermore, the methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell, comprising:

[0027] The methanol solution is stored in a methanol solution storage tank. After passing through the second peristaltic pump, it passes through the first buffer tank and the hydrogen cooler in sequence. It is then vaporized and heated to the reforming temperature by the first evaporator.

[0028] The gas exiting the first evaporator enters the reformer for reaction.

[0029] After the reaction is complete, a coarse, heavy, and purified gas is obtained.

[0030] The crude and heavy reformed gas is fed into a low-temperature shift reactor for crude purification.

[0031] The crude purified gas is cooled to the temperature required for the PROX reaction by a hydrogen cooler;

[0032] The cooled crude purified gas enters the PROX reactor for further purification.

[0033] The purified gas passes through the second buffer tank and enters the anode of the fuel cell for electrochemical reaction;

[0034] The anode exhaust gas enters the exhaust gas buffer tank and mixes with the cathode exhaust gas.

[0035] Furthermore, the high-purity methanol undergoes a catalytic combustion reaction, with the heat of reaction used for methanol solution reforming, including:

[0036] High-purity methanol is stored in a methanol storage tank. After being pressurized by the first peristaltic pump, it is vaporized by the second evaporator.

[0037] Methanol gas enters the catalytic combustor and reacts with the fuel cell exhaust gas. The heat from the reaction is used to heat the reformer and then to provide heat to the methanol solution for reforming.

[0038] On the other hand, the present invention provides a high-efficiency methanol reforming fuel cell power generation system based on ambient temperature PEMFC, comprising: a methanol solution reforming unit, a high-purity methanol catalytic reaction unit, a combustion flue gas unit, an air unit, and a cooling unit;

[0039] The methanol solution reforming unit is used to directly supply the reformed and purified methanol solution gas to the fuel cell anode.

[0040] The high-purity methanol catalytic reaction unit is used to provide heat to the reforming of methanol solution through catalytic combustion reaction;

[0041] The combustion flue gas unit is used to provide heat for methanol solution reforming and to provide heat for cooling working fluid temperature regulation to achieve system start-up at room temperature and low temperature.

[0042] The air unit includes a first branch, a second branch, and a third branch. The first branch is the main air path, and the air from the main air path enters the cathode of the fuel cell for electrochemical reaction. The air from the second branch participates in the purification reaction of the crude purified gas. The third branch is the Air Bleed air path, and the Air Bleed air path, after being fully mixed with the refined purified gas, enters the anode of the fuel cell together to participate in the reaction.

[0043] The cooling unit is used to cool the fuel cell and compressed air, and to regulate the temperature of the cooling medium by exchanging heat with the high-temperature combustion flue gas. The cooling medium after heat exchange heats the fuel cell stack, enabling the system to start up at room temperature and low temperature.

[0044] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0045] 1. The present invention is a high-efficiency methanol reforming fuel cell power generation method and system design based on ambient temperature PEMFC, which combines the characteristics of ambient temperature PEMFC and high temperature HPEMFC, and has high power generation (above 10kW) and power density (taking a rated power of 15kW as an example, the power generation unit is about 950W / kg, the whole machine is above 180W / kg, the rated power is higher and the power density is higher).

[0046] 2. Regarding raw material storage, a prepared methanol-water solution and high-purity methanol are used as inputs, and Ice River refrigerant is used as the working fluid, which has a low freezing point and strong adaptability to low-temperature storage.

[0047] 3. The fuel cell eliminates the hydrogen recirculation system, replacing it with a direct anode connection. Unused hydrogen is fed into the catalytic burner for waste heat utilization, and the anode is humidified with excess water from the reformed gas. This simplifies the fuel cell power generation system, increases power density, and saves space. Fuel cells have strict requirements for the pressure difference between the anode and cathode sides; excessive pressure difference can damage the system. This invention uses a mixture of anode and cathode exhaust gases to balance the pressure on both sides, improving system reliability.

[0048] 4. The high-purity methanol self-heating combustion adopts catalytic combustion, enabling rapid automatic ignition under low-temperature conditions without the need for external ignition facilities, thus improving the system's adaptability to extreme environments. The combustion aid utilizes fuel cell exhaust gas, taking advantage of both unused hydrogen and residual sensible heat from the cathode exhaust gas. The low oxygen content in the cathode exhaust gas reduces the combustion reaction rate, minimizes localized high-temperature points, and extends catalyst lifespan. The heat generated by combustion, besides supplying heat to the reforming and cryogenic shift processes, can further heat and vaporize the inlet methanol solution and high-purity methanol in the high-temperature flue gas. This fully utilizes residual heat, lowers the exhaust gas temperature, and improves the system's thermal efficiency. This invention requires only one air pressurization device, increasing system power density while reducing equipment internal losses and system complexity.

[0049] 5. After methanol steam reforming (200–350℃), it undergoes preliminary purification via a low-temperature shift reaction (180–250℃), followed by fine purification using PROX technology (70–100℃). The latent heat between the crude and fine purification processes is utilized by preheating the methanol-water solution through a heat exchanger, while simultaneously cooling the crude purified gas to the reaction temperature of the next stage, thus fully utilizing the system's latent heat. Compared to other purification methods, this approach is compact, consumes minimal energy, and further improves the system's thermal efficiency.

[0050] 6. Regarding system operation, an Air Bleed path is added. By introducing a small amount of air into the anode using Air Bleed technology, the potential for fuel cell poisoning due to substandard purification performance of the purification system is addressed. This significantly improves system stability. The system operates under pressure to mitigate the current density drop caused by CO2 dilution.

[0051] 7. By using methanol catalytic rapid self-ignition and starting the heat exchanger, combined with the characteristics of room temperature PEMFC, the system can achieve rapid start-up and can start without the aid of a battery, thus improving low-temperature start-up performance.

[0052] 8. The system's wastewater can be recycled, eliminating the need for high-purity water replenishment and reducing replenishment requirements.

[0053] 9. The overall electrical efficiency of a room-temperature PEMFC is about 25% to 30%. Through reasonable system design, this invention can make the overall operating efficiency of the room-temperature PEMFC system higher than 43%, reaching the electrical efficiency level of a high-temperature HPEMFC system, and combining the advantages of both room-temperature and high-temperature proton exchange membrane fuel cells.

[0054] In summary, this invention retains the advantages of high power density, compact structure, and fast start-up of warm PEMFC systems, while also possessing the high stability, high overall efficiency, and simplified system characteristics of high-temperature HPEMFC systems. It can be extended to be used in more fields and environments with higher power generation requirements, and also has good adaptability to low-temperature storage and start-up.

[0055] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0056] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0057] Figure 1 This is a schematic diagram of the methanol reforming fuel cell power generation system of the present invention;

[0058] Figure 2 This is an Aspen simulation flowchart of the methanol reforming fuel cell power generation system of the present invention;

[0059] Reference numerals: Air compressor B-01; Intercooler Z-01; Membrane humidifier M-01; First buffer tank T-01; Second buffer tank T-02; Exhaust gas buffer tank T-03; First heat exchanger E-01; Second heat exchanger E-02; Catalytic combustor F-01; Reformer R-01; Low-temperature shift reactor LTS-01; First evaporator V-01; Second evaporator V-02; Hydrogen cooler PH-01; First peristaltic pump P-01; Second peristaltic pump P-02; Coolant pump P-03; PROX reactor D-01; Separator S-01; First cooler C-01; Second cooler C-02; Third cooler C-03. Detailed Implementation

[0060] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0061] Methanol reforming PEMFC power generation systems can be categorized into ambient temperature PEMFCs and high-temperature HPEMFCs based on their operating temperature. Ambient temperature PEMFCs offer higher power density, larger power output per stack, faster start-up, and a more compact power generation unit. However, they are more complex in terms of system and process control, and suffer from lower reliability due to low CO tolerance, higher energy consumption, and lower overall thermal and electrical efficiency. High-temperature HPEMFCs offer even higher overall electrical efficiency, exceeding 45%. However, limitations in membrane electrode technology currently restrict their power density, resulting in limited power output per stack. Integrating them into large systems or hydrogen fuel cell engines may require multiple stacks, leading to a bulkier overall system. Furthermore, high-temperature operation is accompanied by longer start-up times. Both types of PEMFCs share challenges related to low-temperature storage and the difficulty of starting at low temperatures, necessitating the use of energy storage batteries.

[0062] This invention provides a high-efficiency methanol reforming fuel cell power generation method based on a room-temperature PEMFC, using methanol solution and high-purity methanol as inputs, including:

[0063] The methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell;

[0064] High-purity methanol undergoes catalytic combustion, and the heat of reaction is used for methanol solution reforming.

[0065] Air is pressurized and humidified before being directly introduced into the cathode of the fuel cell.

[0066] The cooling medium is pressurized and then used to cool the fuel cell.

[0067] This invention uses a prepared methanol-water solution and high-purity methanol as inputs. The heat generated by the combustion of high-purity methanol supplies heat to methanol reforming and provides the possibility of fully utilizing the waste heat from the high-temperature flue gas generated during combustion, thereby improving the system's thermal efficiency. The anode is humidified by excess water in the reformed gas, simplifying the fuel cell power generation system, increasing the system's power density, and saving space. Furthermore, the fuel cell adopts a direct-flow anode configuration, eliminating the need for a hydrogen recirculation system.

[0068] Specifically, the methanol solution is reformed and purified before being directly fed into the anode of the fuel cell. This process involves pressurizing, cooling, vaporizing, and heating the methanol solution to the reforming temperature to obtain crude reformed gas. The crude reformed gas undergoes low-temperature conversion to obtain crude purified gas. The crude purified gas is then cooled and subjected to a PROX reaction to obtain refined purified gas. After being buffered, the refined purified gas is directly fed into the anode of the fuel cell for electrochemical reaction.

[0069] It should be noted that the methanol solution, after reforming and purification, is directly fed into the fuel cell anode through a methanol solution reforming unit. The water-to-methanol molar ratio of the methanol solution is 1.3. The methanol solution is stored in a methanol solution tank and, after being pressurized by a peristaltic pump, passes through a pressure buffer, is cooled, and is vaporized and heated to the reforming temperature. The vaporized gas is the feed gas, which undergoes a reforming reaction. The product obtained after the reaction is crude reformed gas, which undergoes a low-temperature shift reaction for crude purification. The crude purified gas is then cooled to the temperature required for the PROX reaction. The cooled crude purified gas undergoes a PROX reaction for further purification. The purified gas is then buffered and enters the fuel cell anode for electrochemical reaction. The anode tail gas is buffered and mixed with the cathode tail gas to balance the pressure of the cathode and anode inside the fuel cell stack, reduce the risk of overpressure, and improve system reliability.

[0070] Since the system uses methanol reformed gas as fuel, the anode gas supply to the fuel cell contains approximately 30% CO2. To achieve the current density required for pure hydrogen conditions, the system needs to be pressurized to approximately 2 Bar. The operating pressure of the fuel cell can be controlled via an air compressor, pump, and back pressure valve after the exhaust gas buffer tank. Pressurized operation enhances the purging effect of gases inside the fuel cell stack and the partial pressure of water vapor, effectively preventing membrane electrode flooding and drying, and providing a benefit to water management. Because the methanol solution input to the system needs to be prepared according to a water-to-methanol molar ratio of 1.3, replenishment is somewhat difficult and costly. Therefore, after condensation, the system drainage can be recycled by connecting an external circulation pump to the feed tank, thus forming a pure methanol replenishment system without the need for additional water replenishment, reducing the difficulty of system replenishment. The drain valve on the exhaust gas buffer tank can also function as a purging valve, working in conjunction with the air compressor to purge liquid water generated within the fuel cell stack.

[0071] Specifically, high-purity methanol undergoes a catalytic combustion reaction, which involves pressurizing, vaporizing, and heating high-purity methanol before it is reacted with fuel cell exhaust gas.

[0072] It should be noted that the catalytic combustion reaction of high-purity methanol is achieved through a high-purity methanol catalytic reaction unit. High-purity methanol is stored in a methanol storage tank, pressurized by a peristaltic pump, and then vaporized to obtain methanol gas. The methanol gas undergoes a catalytic combustion reaction with the fuel cell exhaust gas, and the heat from the reaction is used to heat the reforming reaction, supplying heat to the methanol solution for reforming. Some unused hydrogen in the anode exhaust gas is recovered as waste heat. Under varying operating conditions, excess hydrogen is burned through an excess anode fuel supply, preventing fuel cell overload without affecting system efficiency, forming an energy buffer, and improving system stability. The catalyst used in the catalytic combustion reaction is the precious metal platinum (Pt), ensuring that the methanol gas and anode exhaust gas can undergo rapid self-ignition at low temperatures and without external ignition.

[0073] Specifically, high-purity methanol undergoes a catalytic combustion reaction to produce high-temperature combustion flue gas, which is divided into a first branch and a second branch. The high-temperature combustion flue gas from the first branch is used to provide heat for the reforming of the methanol solution, while the high-temperature combustion flue gas from the second branch is used as the cooling medium in the heating and cooling unit.

[0074] It should be noted that the catalytic combustion reaction produces high-temperature combustion flue gas, which circulates through the combustion unit. This high-temperature combustion flue gas is divided into two branches. In the first branch, the high-temperature combustion flue gas first undergoes evaporation, providing heat to vaporize the methanol solution and heat it to the reforming temperature. After further evaporation, it is heated and vaporized to produce high-purity methanol. This vapor then passes through a heat exchanger to heat the fuel cell exhaust gas, allowing for waste heat reuse. Finally, it is cooled to below the specified exhaust temperature and then discharged after vapor-liquid separation by a separator. In the second branch, the high-temperature combustion flue gas undergoes heat exchange to heat the cooling medium in the cooling system. The cooled medium then heats the fuel cell stack, enabling the system to start at room temperature and low temperatures. The remaining gas is discharged after its temperature drops below the specified exhaust temperature.

[0075] Specifically, the cooling medium is pressurized and used to cool the fuel cell. This includes pressurizing the cooling medium and supplying it to the fuel cell and intercooler respectively. The cooling medium can be recycled through the cooling unit. The cooling medium exchanges heat with the high-temperature combustion flue gas generated by the catalytic combustion reaction of high-purity methanol through a heat exchanger. The cooled medium after heat exchange heats the fuel cell stack, enabling the system to start at room temperature and low temperature.

[0076] Specifically, the system's normal temperature and low temperature start-up includes: the high-temperature combustion flue gas from the second branch is used to heat the cooling working fluid; the cooling working fluid's temperature is regulated by starting a heat exchanger; and an electric heater is connected in parallel to the heat exchanger to achieve temperature regulation and meet the normal temperature and low temperature start-up conditions.

[0077] Specifically, the coolant, after being pressurized, is used to cool the fuel cell through a cooling unit. Glacier refrigerant is used as the coolant due to its low freezing point and strong adaptability to low-temperature storage. The coolant is stored in a coolant tank and pressurized by a coolant pump, supplying it to the fuel cell stack and intercooler. The coolant removes the heat from the electrochemical reaction of the fuel cell and the heat of compression from air compression. The high-temperature coolant is cooled and then returned to the coolant tank for recycling. During low-temperature and normal-temperature startup, the coolant temperature can be regulated by starting a heat exchanger. The heat exchanger is connected in parallel with an electric heater circuit to achieve temperature regulation, meeting the requirements for normal-temperature startup. During startup, the intercooler supply can be stopped or reduced to quickly increase the air intake temperature and shorten the system startup time.

[0078] Specifically, the air, after being pressurized and humidified, is directly introduced into the fuel cell cathode. The air is compressed, pressurized, and then divided into three branches by an intercooler. The first branch is the main air path, which, after humidification, enters the fuel cell cathode for electrochemical reaction. The resulting high-humidity cathode exhaust gas is used again to humidify the air, and simultaneously mixes with the refined purified gas and the anode exhaust gas produced after the reaction at the fuel cell anode. This mixed exhaust gas, after heating, acts as an oxidant in a combustion reaction with high-purity methanol. Meanwhile, the liquid water, an electrochemical reaction product carried out by the cathode gas, is separated and discharged. The second branch of air participates in the purification reaction of the crude purified gas. The third branch of air is the Air Bleed air path, which, after being thoroughly mixed with the refined purified gas, enters the fuel cell anode to participate in the reaction.

[0079] It should be noted that the air, after being pressurized and humidified, is directly introduced into the fuel cell cathode via an air circulation unit. After being pressurized by the air compressor, the air temperature rises. Directly introducing this air into the humidifier and fuel cell may exceed their safe operating temperature. Therefore, it needs to be cooled to a safe temperature via an intercooler, after which it is divided into three branches. The first branch is the main air path, which humidifies the air sequentially through a membrane humidifier. It should be noted that other humidification methods can also be used; if a self-humidifying fuel cell is used, the membrane humidifier can be omitted. The humidified air enters the fuel cell cathode for the electrochemical reaction. The high-humidity cathode exhaust gas after the reaction re-enters the membrane humidifier to humidify the intake air. After buffering, it mixes with the anode exhaust gas to ensure pressure balance on the cathode and anode sides. The liquid water, an electrochemical reaction product carried out by the cathode gas, is separated and discharged here. Additionally, the cathode exhaust gas, which is low in oxygen after participating in the reaction, enters the heat exchanger through a pressure regulating back pressure valve for heat exchange. After heating, it enters the catalytic burner as an oxidant to participate in the reaction, simultaneously lowering the combustion reaction temperature, avoiding localized high-temperature points, extending catalyst life, and facilitating temperature control. Since the fuel cell exhaust still has a certain temperature, this waste heat can be reused. The second branch's air participates in the purification reaction of the crude purified gas, connected to the PROX reactor via a control valve to participate in the purification reaction. The third branch is the Air Bleed air path, which introduces a small amount of air (2% to 5% by volume) into the purified hydrogen at the anode, enabling the fuel cell to operate normally under conditions far exceeding the normal tolerance CO concentration. The air in this branch is connected to a buffer tank through a control valve to complete the buffering, and is fully mixed with the purified gas before entering the fuel cell anode to participate in the reaction. This solves the problem of increased fuel cell poisoning risk caused by the unsatisfactory purification effect of LTS+PROX.

[0080] The present invention also provides a high-efficiency methanol reforming fuel cell power generation system based on ambient temperature PEMFC to realize the fuel cell power generation method, comprising: a methanol solution reforming unit, a high-purity methanol catalytic reaction unit, a combustion flue gas unit, an air unit, and a cooling unit;

[0081] The methanol solution reforming unit is used to directly supply the reformed and purified methanol solution gas to the fuel cell anode.

[0082] The high-purity methanol catalytic reaction unit is used to provide heat to the reforming of methanol solution through catalytic combustion reaction;

[0083] The combustion flue gas unit is used to provide heat for methanol solution reforming and to provide heat for cooling working fluid temperature regulation to achieve system start-up at room temperature and low temperature.

[0084] The air unit includes a first branch, a second branch, and a third branch. The first branch is the main air path, and the air from the main air path enters the cathode of the fuel cell for electrochemical reaction. The air from the second branch participates in the purification reaction of the crude purified gas. The third branch is the Air Bleed air path, and the Air Bleed air path, after being fully mixed with the refined purified gas, enters the anode of the fuel cell together to participate in the reaction.

[0085] The cooling unit is used to cool the fuel cell and compressed air, and to regulate the temperature of the cooling medium by exchanging heat with the high-temperature combustion flue gas. The cooling medium after heat exchange heats the fuel cell stack, enabling the system to start up at room temperature and low temperature.

[0086] Specifically, the methanol solution reforming unit includes a methanol solution storage tank, a second peristaltic pump P-02, a hydrogen cooler PH-01, a reformer R-01, a cryogenic converter LTS-01, and a PROX reactor D-01 connected in sequence. The outlet of the PROX reactor D-01 is connected to the fuel cell anode pipeline, and the purified gas is directly introduced into the fuel cell anode through the pipeline.

[0087] Specifically, the high-purity methanol catalytic reaction unit includes a methanol storage tank, a first peristaltic pump P-01, and a catalytic burner F-01 connected in sequence. The outlet of the catalytic burner F-01 is connected to the inlet of the reformer R-01 of the methanol solution reforming unit. A portion of the high-temperature flue gas generated by catalytic combustion enters the reformer R-01.

[0088] Specifically, the air unit includes an air compressor B-01, an intercooler Z-01, and a membrane humidifier M-01 connected in sequence; the outlet of the membrane humidifier M-01 is connected to the cathode of the fuel cell. After being compressed by the air compressor B-01 and heat-exchanged by the intercooler Z-01, the air enters the membrane humidifier M-01, and the humidified air enters the cathode of the fuel cell.

[0089] Furthermore, after being compressed, pressurized, and cooled, the air is divided into three branches, and the air unit includes three branch pipelines. The first branch pipeline is the main air pipeline, where the air is humidified and enters the fuel cell cathode for electrochemical reaction. The resulting high-humidity cathode exhaust gas is used again to humidify the air, and at the same time, it is mixed with the refined purified gas and the anode exhaust gas produced after the reaction at the fuel cell anode. The mixed exhaust gas is heated and used as an oxidant to carry out a catalytic combustion reaction with high-purity methanol. Meanwhile, the liquid water, an electrochemical reaction product carried out by the cathode gas, is separated and discharged. The air in the second branch pipeline participates in the purification reaction of the crude purified gas. The third branch pipeline is the Air Bleed air pipeline, where the air is fully mixed with the refined purified gas and then enters the fuel cell anode to participate in the reaction.

[0090] Specifically, the cooling unit includes a coolant storage tank, a coolant pump P-03, and a second cooler C-02. The coolant is pumped into the fuel cell by the coolant pump P-03 for heat exchange and then discharged. The cooled coolant is cooled by the second cooler C-02 and then returned to the coolant storage tank.

[0091] Furthermore, a portion of the cooling working fluid from the cooling unit is pumped into the intercooler Z-01 of the air unit via the coolant pump P-03, where it exchanges heat with the air passing through the intercooler Z-01 before returning to the coolant storage tank.

[0092] Specifically, the combustion flue gas unit includes a first branch pipeline and a second branch pipeline; the outlet of the first branch pipeline is connected to the methanol solution reformer; the second branch pipeline is connected to the pipeline through which the cooling working fluid is pumped into the fuel cell via the coolant pump P-03, and the high-temperature flue gas in the second branch pipeline exchanges heat with the cooling working fluid.

[0093] The aforementioned high-efficiency methanol reforming fuel cell power generation system based on ambient temperature PEMFC also includes an evaporation unit, a heat exchange unit, and a buffer unit.

[0094] Specifically, the evaporation unit includes a first evaporator V-01, a second evaporator V-02, a first cooler C-01, and a separator S-01 connected in sequence.

[0095] Specifically, the heat exchange unit includes a first heat exchanger E-01 and a second heat exchanger E-02.

[0096] Specifically, the buffer unit includes a first buffer tank T-01, a second buffer tank T-02, and an exhaust gas buffer tank T-03.

[0097] Furthermore, the aforementioned high-efficiency methanol reforming fuel cell power generation system of ambient temperature PEMFC also includes a power generation unit and control components.

[0098] It should be noted that the high-temperature components in the system are placed in a high-temperature insulated box to form a near-thermal isolated system, including catalytic reactor F-01, reformer R-01, low-temperature shift reactor LTS-01, first evaporator V-01, second evaporator V-02, third cooler C-03, heat exchanger E-01, and heat exchanger E-02.

[0099] Specifically, the first evaporator V-01 of the evaporation unit is installed on the raw gas pipeline. The first evaporator V-01 includes multiple inlet ends and multiple outlet ends. One inlet end of the first evaporator V-01 is connected to one outlet end of the hydrogen cooler PH-01 of the methanol solution reforming unit. The other inlet end of the first evaporator V-01 is connected to one outlet end of the reformer R-01 of the methanol solution reforming unit. One outlet end of the first evaporator V-01 is connected in sequence to the second evaporator V-02, the first heat exchanger E-01, and the first cooler C-01.

[0100] The second evaporator V-02, the first cooler C-01, and the liquid separator S-01 of the evaporation unit are installed on the first branch pipeline of the combustion flue gas unit. The second evaporator V-02 is connected to the first evaporator V-01 and the first heat exchanger E-01 of the heat exchange unit through the first branch pipeline of the combustion flue gas. At the same time, it is connected to the catalytic burner F-01 and the first peristaltic pump P-01 through the high-purity methanol pipeline. The first cooler C-01 is connected to the liquid separator S-01 of the first heat exchanger E-01.

[0101] The first heat exchanger E-01 of the heat exchange unit is connected to the second evaporator V-02 and the first cooler C-01 of the evaporation unit through the first branch pipeline of the combustion flue gas, and is also connected to the tail gas buffer tank T-03 of the buffer unit and the catalytic burner F-01 of the high-purity methanol catalytic reaction unit through the main air pipeline of the air unit.

[0102] The first buffer tank T-01 of the buffer unit is connected to the second peristaltic pump P-02 and the hydrogen cooler PH-01 via methanol solution pipelines. The second buffer tank T-02 is connected to the intercooler Z-01 via the Air Bleed air pipeline of the air unit, and is also connected to the fuel cell anode and the third cooler C-03 via the reforming gas pipeline of the methanol solution unit. The exhaust gas buffer tank T-03 is connected to the fuel cell cathode and the first heat exchanger E-03 via the main air pipeline, and is also connected to the fuel cell anode via the reforming gas pipeline.

[0103] During operation, the methanol solution, after being pressurized by a pump, sequentially passes through the first buffer tank T-01 for preheating; the first evaporator V-01 vaporizes and heats the solution to the reforming temperature, where the reaction takes place; the product, crude reformed gas, enters the low-temperature shift reactor LTS-01 for crude purification; the crude purified gas is cooled to the temperature required for the PROX reaction by the third cooler C-03; the cooled crude purified gas enters the PROX reactor for fine purification; the finely purified gas passes through the second buffer tank T-02 and enters the anode of the fuel cell for electrochemical reaction; the anode tail gas enters the tail gas buffer tank T-03 and mixes with the cathode tail gas.

[0104] After being pressurized by the air compressor, the air is cooled by the intercooler Z-01 and then divided into three paths. The first path is the main air path, which sequentially passes through the membrane humidifier M-01 for humidification (optional, other humidification methods can be used; if a self-humidifying fuel cell is used, the membrane humidifier can be omitted); the fuel cell cathode undergoes an electrochemical reaction; the high-humidity cathode exhaust gas re-enters the membrane humidifier M-01 to humidify the intake air; it then enters the exhaust gas buffer tank T-03 to mix with the anode exhaust gas to ensure pressure balance on the cathode and anode sides, where the liquid water, an electrochemical reaction product carried out by the cathode gas, is separated and discharged; afterwards, it enters the first heat exchanger E-01 for heating before entering the catalytic combustor F-01 to participate in the reaction as an oxidant. Since the fuel cell exhaust still has a certain temperature, this waste heat can be reused. The second path is PROX purified air, which is connected to the PROX reactor D-01 through a control valve to participate in the purification reaction.

[0105] To address the issue of increased fuel cell toxicity risk due to unsatisfactory LTS+PROX purification performance, a third Air Bleed air path is introduced. Air Bleed technology involves introducing a small amount of air (2%–5% by volume) into the purified hydrogen at the anode, enabling the fuel cell to operate normally under conditions far exceeding the normal tolerance for CO concentrations. The Air Bleed air is connected to the second buffer tank T-02 via a control valve, where it is thoroughly mixed with the purified gas before entering the fuel cell anode together.

[0106] High-purity methanol, after being pressurized by the first peristaltic pump P-01, is vaporized sequentially through the second evaporator V-02. It then enters the catalytic combustor F-01, where it undergoes combustion with the fuel cell exhaust gas. The heat from the reaction is used to heat the reformer R-01. Some unused hydrogen in the anode exhaust gas is recovered here as waste heat. The low-oxygen air participating in the reaction lowers the combustion reaction temperature, preventing localized high-temperature points, extending catalyst life, and facilitating temperature control. High-temperature flue gas is produced after combustion. The catalyst used in the catalytic combustor F-01 is the precious metal Pt, ensuring that the fuel can undergo rapid self-ignition under low temperature and without external ignition.

[0107] The high-temperature flue gas generated by combustion sequentially passes through the first evaporator V-01, where the methanol solution is vaporized and heated to the reforming reaction temperature; then, it passes through the second evaporator V-02, where high-purity methanol is further vaporized; finally, it passes through the first heat exchanger E-01 to heat the fuel cell exhaust gas, allowing for waste heat reuse; and finally, it enters the cooling device to be cooled below the specified exhaust temperature, and is discharged after vapor-liquid separation in the drain tank. The combustion flue gas can be bypassed, and by activating the second heat exchanger E-02, it can heat the cooling medium in the cooling unit, which in turn heats the fuel cell stack, thus enabling the system to start up at both ambient and low temperatures.

[0108] The cooling unit pressurizes the coolant via pump P-03, supplying it to both the fuel cell stack and intercooler Z-01. The working fluid removes heat from the fuel cell's electrochemical reaction and the heat of air compression. The high-temperature coolant is then cooled in the second cooler C-02 and recycled. During low-temperature and normal-temperature startup, the coolant can be heated via a startup heat exchanger. The second heat exchanger E-02 is connected in parallel with an electric heater circuit for temperature regulation, ensuring normal-temperature startup conditions. During startup, the coolant supply to intercooler Z-01 can be stopped or reduced to increase the rapid air intake temperature.

[0109] This invention uses a room-temperature PEMFC as the power generation unit in a methanol reforming fuel cell power generation system. Compared to a high-temperature HPEMFC, it boasts higher power output (above 10kW) and power density (for example, with a rated power of 15kW, the power generation unit achieves approximately 950W / kg, and the entire unit exceeds 180W / kg; higher rated power results in higher power density). For feedstock storage, a pre-prepared methanol-water solution and high-purity methanol are used as inputs, and Glacier refrigerant is used as the working fluid, exhibiting a low freezing point and strong adaptability to low-temperature storage. Regarding the fuel cell power generation unit, the hydrogen circulation system is eliminated, replaced by a direct anode connection. Unused hydrogen is fed into the burner for waste heat utilization, and the anode is humidified with excess water from the reformed gas, simplifying the power generation unit system, increasing the system's power density, and saving space. Anode and cathode exhaust gases are mixed to balance the pressure on both sides, improving system reliability. Methanol auto-heating combustion employs catalytic combustion, enabling rapid automatic ignition under low-temperature conditions without external ignition facilities, thus improving the system's adaptability to extreme environments. The combustion aid utilizes fuel cell exhaust gas, taking advantage of both unused hydrogen and residual sensible heat. The low oxygen content in the exhaust gas reduces the combustion reaction rate, minimizes localized high-temperature points, and extends catalyst lifespan. The heat generated from combustion, besides supplying heat to the reforming and low-temperature shift reaction, allows the high-temperature flue gas to further heat and vaporize the inlet methanol solution and high-purity methanol. This fully utilizes residual heat, lowers the exhaust temperature, and improves system thermal efficiency. Furthermore, this design requires only one air pressurization unit, increasing system power density while reducing equipment consumption and system complexity. After methanol steam reforming (200–350°C), it undergoes preliminary purification via a low-temperature shift reaction (180–250°C), followed by fine purification using PROX technology (70–100°C). The latent heat between crude and fine purification is preheated in the methanol-water solution via a heat exchanger, simultaneously cooling the crude purified gas to the reaction temperature of the next stage. This fully utilizes the system's latent heat. Compared to other purification methods, this approach boasts a compact structure and minimal energy consumption, further enhancing system thermal efficiency. In terms of system operation, the addition of an AirBleed gas path, utilizing AirBleed technology to introduce a small amount of air into the anode, addresses the potential fuel cell poisoning issue caused by substandard purification performance, significantly improving system stability. The system operates under pressure to mitigate the current density drop caused by CO2 dilution. Through methanol catalytic rapid self-ignition and a start-up heat exchanger, combined with the characteristics of a room-temperature PEMFC, the system achieves rapid start-up and can be completed without a battery, improving low-temperature start-up performance.

[0110] Furthermore, the system's wastewater can be recycled, eliminating the need for high-purity water replenishment and reducing supply requirements. With the fuel cell power generation unit's electrical efficiency at the industry average of approximately 50%, the overall system thermal efficiency exceeds 43%, reaching the electrical efficiency level of high-temperature HPEMFC systems.

[0111] In summary, the present invention provides a high-efficiency methanol reforming fuel cell power generation method and system based on ambient temperature PEMFC. While retaining the advantages of ambient temperature PEMFC system such as high power density, compact structure and fast start-up, it also has the characteristics of high stability, high overall efficiency and system simplification of high temperature HPEMFC system. It can be used in more fields and environments with higher power generation requirements, and also has good adaptability to low temperature storage and start-up.

[0112] To verify the rationality of the system design, a process simulation model was built using Aspen software, and simulation calculations of the system's process flow were performed. (See modeling details below.) Figure 2 Taking a system with a net output of 15kW of electrical energy as an example (fuel cell output power minus the power consumed by pumps, fans, and control systems within the system), a typical output power condition is selected for system simulation calculations, where the air equivalence coefficient is 2.0. By adjusting the inlet flow rate of high-purity methanol, the heat released by the combustion of high-purity methanol is made equal to the sum of the heat absorbed by methanol solution preheating and vaporization, methanol reforming, methanol vaporization, and air preheating, thus achieving overall system thermal equilibrium. The system exhaust temperature is 70℃, the methanol reforming selectivity is 97%, and purification can reduce CO to below 5ppm. Considering the system heat loss and the impact of AirBleed technology on the output power, assuming the fuel cell electrical efficiency is approximately 50% (the industry average), and based on the given material inlet boundary conditions according to the system output power, the overall Gibbs free energy is minimized using Aspen software. The calculation shows that when the system's net output power is 15kW, its overall thermal efficiency is approximately 43%. Based on the fuel cell load and characteristics, the system's electrical efficiency increases when below the rated power; therefore, the overall operating efficiency of the system is higher than 43%. It is evident that through reasonable system design, the overall thermal efficiency of the room temperature PEMFC system can reach the level of the high temperature HPEMFC system, verifying the feasibility and rationality of the present invention, and demonstrating that the system has achieved the goal of combining the advantages of both room temperature and high temperature proton exchange membrane fuel cells.

[0113] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for generating electricity from a high-efficiency methanol reforming fuel cell based on a room-temperature PEMFC, characterized in that, Using a methanol solution and high-purity methanol as inputs, the method includes: The methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell; High-purity methanol undergoes catalytic combustion, and the heat of reaction is used for methanol solution reforming. Air is pressurized and humidified before being directly introduced into the cathode of the fuel cell. The cooling medium is pressurized and then used to cool the fuel cell. The methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell, including: Methanol solution is pressurized, cooled, vaporized and heated to the reforming temperature to obtain crude reformed gas. The crude reformed gas is subjected to low-temperature conversion to obtain crude purified gas. The crude purified gas is cooled and subjected to PROX reaction to obtain refined purified gas. The refined purified gas is buffered and then directly fed into the anode of the fuel cell for electrochemical reaction. The high-purity methanol undergoes a catalytic combustion reaction, and the heat of reaction is used for methanol solution reforming: this includes high-purity methanol being pressurized, vaporized, heated, and then reacted with fuel cell exhaust gas for combustion. The high-purity methanol is catalytically combusted to produce high-temperature combustion flue gas, which is divided into a first branch and a second branch. The high-temperature combustion flue gas from the first branch is used to provide heat for the reforming of the methanol solution; The high-temperature combustion flue gas from the second branch is used to heat the cooling medium in the cooling unit; The air is pressurized and humidified before being directly introduced into the cathode of the fuel cell, including: the air is divided into three branches after being compressed, pressurized and cooled by an intercooler; The first branch is the main air path. After humidification, it enters the cathode of the fuel cell to carry out electrochemical reaction. The high humidity cathode tail gas produced is used to humidify the air again. At the same time, it is mixed with the refined gas and the anode tail gas produced after the reaction of the fuel cell anode. The mixed tail gas is heated and used as an oxidant to react with high-purity methanol. Meanwhile, the electrochemical reaction product liquid water carried out by the cathode gas is separated and discharged. The second branch air participates in the purification reaction of the crude purified gas; The third branch air is the Air Bleed air path, which, after being fully mixed with the refined gas, enters the fuel cell anode together to participate in the reaction; The coolant is pressurized and used to cool the fuel cell. The pressurized coolant is supplied to the fuel cell and the intercooler respectively. The coolant can be recycled through the cooling unit. The coolant exchanges heat with the high-temperature combustion flue gas generated by the catalytic combustion reaction of high-purity methanol through the second heat exchanger. The cooled coolant after heat exchange heats the fuel cell stack, realizing the system's room temperature and low temperature start-up. The system achieves normal temperature and low temperature startup, including: The high-temperature combustion flue gas in the second branch is used to heat and cool the working medium. The working medium is regulated by starting the second heat exchanger. The second heat exchanger is connected in parallel with an electric heater to achieve temperature regulation and meet the start-up conditions at normal and low temperatures.

2. The power generation method according to claim 1, characterized in that, The methanol solution, after reforming and purification, is directly fed into the anode of the fuel cell, including: The methanol solution is stored in a methanol solution storage tank. After passing through the second peristaltic pump, it passes through the first buffer tank and the hydrogen cooler in sequence. It is then vaporized and heated to the reforming temperature by the first evaporator. The gas exiting the first evaporator enters the reformer for reaction. After the reaction is complete, a coarse and heavy rectified gas is obtained; The crude and heavy reformed gas is fed into a low-temperature shift reactor for crude purification. The crude purified gas is cooled to the temperature required for the PROX reaction by a hydrogen cooler; The cooled crude purified gas enters the PROX reactor for further purification. The purified gas passes through the second buffer tank and enters the anode of the fuel cell for electrochemical reaction; The anode exhaust gas enters the exhaust gas buffer tank and mixes with the cathode exhaust gas.

3. The power generation method according to claim 1, characterized in that, The high-purity methanol undergoes a catalytic combustion reaction, and the heat of reaction is used for methanol solution reforming, including: High-purity methanol is stored in a methanol storage tank. After being pressurized by the first peristaltic pump, it is vaporized by the second evaporator. Methanol gas enters the catalytic combustor and reacts with the fuel cell exhaust gas. The heat from the reaction is used to heat the reformer and then to provide heat to the methanol solution for reforming.

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