A methanol reforming hydrogen fuel cell system and a thermal control method thereof

Abstract

The application discloses a methanol reforming hydrogen fuel cell system and a heat control method thereof. The methanol reforming hydrogen fuel cell system mainly comprises a reformer, a stack, two start-up burners, a heat exchanger and the like. The reformer is formed by repeatedly overlapping a plurality of micro-channel reforming units and a plurality of micro-channel oxidation units. The two start-up burners respectively preheat the oxidation units and the stack in a start-up stage, accelerate the preheating speed of the system, and shorten the reforming start-up time. The heat exchanger is additionally arranged in a flue gas channel of the oxidation unit, so that the high-temperature flue gas is reused, the methanol water gas reaches a higher temperature, and the thermal efficiency of the fuel cell system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a fuel cell, in particular to a methanol reforming hydrogen fuel cell system based on a micro-channel reactor and a heat control method thereof, and belongs to the technical field of reforming hydrogen fuel cells. BACKGROUND

[0002] A fuel cell is a power generation device that mainly performs an oxidation-reduction reaction with oxygen or other oxidants to convert chemical energy in fuel into electrical energy, and the most common fuel is hydrogen. Since hydrogen is a gas at room temperature, it is transported by high-pressure or low-temperature liquid hydrogen, which is inconvenient and costly. In addition, the number of hydrogen filling stations worldwide, including domestic ones, is very limited, and the cost of hydrogen filling stations is high, with a complex construction approval process, making it difficult to establish a large-scale hydrogen infrastructure in a short period of time. Compared with hydrogen fuel cells, methanol is in a liquid state, which is easy to transport and has low cost. The technology and infrastructure for storing, refueling, and transporting methanol are already mature. Compared with hydrogen storage fuel cells, real-time hydrogen production fuel cells using methanol reforming can be used immediately and have many advantages.

[0003] Methanol reforming hydrogen uses a mixture of methanol and water as raw material, which is first heated to evaporate into a gaseous state, and then catalytically converted in a reformer to obtain reforming gas, of which hydrogen is used for fuel cells to generate electricity. The reforming reaction is an endothermic reaction that is sensitive to temperature, and the raw material and catalyst must be kept at the appropriate temperature range to ensure that the reforming reaction proceeds continuously, efficiently, and stably. Maintaining the temperature of the reformer stable and preventing the occurrence of local high temperature areas that cause the deactivation of the reforming catalyst is the focus of research on methanol reforming hydrogen fuel cells.

[0004] During the startup phase of the fuel cell, the reformer and the stack need to be preheated to the operating temperature. The existing method is to use a startup burner connected in series with the reformer and the stack. The operating temperature of the reformer is high, and the operating temperature of the stack is low, so the operating temperatures of the two are not the same. First, the reformer is heated to a higher operating temperature, and then methanol reforming hydrogen is started. Later, the stack is heated to the appropriate temperature, and the stack starts generating electricity after receiving the reforming gas. Using a single startup burner to sequentially heat the reformer and the stack takes a long time overall, which is not suitable for situations that require rapid startup of the fuel cell. SUMMARY

[0005] The technical problems to be solved by the present application are: the use of a single startup burner affects the startup speed of the entire fuel cell; and the heat management control of the methanol reforming hydrogen fuel cell system needs to be improved to increase the utilization efficiency of heat energy.

[0006] To solve the above technical problems, the first aspect of the present application provides a methanol reforming hydrogen fuel cell system, comprising:

[0007] a reformer, the reformer is formed by repeatedly interleaving a plurality of micro-channel reforming units and a plurality of micro-channel oxidation units; each oxidation unit oxidizes methanol to generate heat and transfers the heat to an adjacent reforming unit; each reforming unit performs a reforming reaction on a methanol and water feedstock to generate a reforming gas mainly composed of hydrogen;

[0008] a stack, the stack is connected to the reformer through a pipeline, and the stack is used to receive the reforming gas and react the reforming gas with air to generate electric energy;

[0009] a start-up burner, used to preheat the oxidation unit and the stack during a start-up phase of the fuel cell;

[0010] a plurality of heat exchangers, used for heat exchange and transfer within the fuel cell system.

[0011] In some embodiments, the heat generated by the start-up burner is at least divided into two parallel paths, wherein a first path supplies heat to the oxidation unit, and a second path supplies heat to the stack.

[0012] In some embodiments, two independent start-up burners are included, wherein a first start-up burner supplies heat to the oxidation unit, and a second start-up burner supplies heat to the stack.

[0013] In some embodiments, the heat exchanger includes a first heat exchanger, and the first heat exchanger adopts a four-way flow channel coupled heat exchanger, wherein,

[0014] a first flow channel of the first heat exchanger is used for a hot gas flow generated by the second start-up burner to pass through;

[0015] a second flow channel of the first heat exchanger is used for a heat transfer liquid to pass through, and the heat transfer liquid transfers heat to the stack;

[0016] a third flow channel of the first heat exchanger is used for the methanol and water feedstock to pass through, and the methanol and water feedstock is heated;

[0017] a fourth flow channel of the first heat exchanger is used for the reforming gas to pass through, and the reforming gas is cooled.

[0018] In some embodiments, the heat exchanger includes a second heat exchanger, and the second heat exchanger adopts a two-way flow channel coupled heat exchanger, wherein,

[0019] a first flow channel of the second heat exchanger is used for the heat transfer liquid to pass through;

[0020] a second flow channel of the second heat exchanger is used for air required for a reaction in the stack to pass through and the air is heated.

[0021] In some embodiments, the heat transfer liquid adopts triethylene glycol or D12 is a synthetic heat transfer oil.

[0022] In some embodiments, a third heat exchanger is included, which is connected to the heat transfer liquid pipeline between the first heat exchanger and the second heat exchanger, and is used to regulate the temperature of the heat transfer liquid.

[0023] In some embodiments, a fourth heat exchanger is included, which is used to recover heat in the flue gas of the oxidation unit and transfer it to the first heat exchanger.

[0024] In a second aspect of the present application, a heat control method for a methanol reforming hydrogen fuel cell system is provided, which includes a reformer and a stack, and two start-up burners are used to preheat the reformer and the stack respectively during the start-up stage of the fuel cell system.

[0025] In some embodiments, the reformer is formed by repeatedly overlapping a plurality of micro-channel reforming units and a plurality of micro-channel oxidation units, the oxidation unit oxidizes methanol and discharges exhaust gas, and a heat exchanger is used to recover the heat of the exhaust gas and provide it to the methanol and water raw material.

[0026] The present application has the following beneficial effects:

[0027] (1) Two start-up burners are used to separately heat the reformer and the stack, which accelerates the preheating speed of the system and shortens the reforming start-up time;

[0028] (2) The high-temperature tail gas generated by the oxidation unit of the reformer flows through the heat exchanger, and the heat in the high-temperature tail gas is used for reheating of the methanol and water vapor; in this way, the high-temperature tail gas is reused, the methanol and water vapor reach a higher temperature, and the thermal efficiency of the fuel cell system is improved;

[0029] (3) The reforming unit and the oxidation unit of the reformer are both micro-channel reactors, the catalyst is more stable on the surface of the micro-channel, can adapt to a certain dynamic environment, and has fewer side reactions. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of the overall architecture of a methanol reforming hydrogen fuel cell system in a preferred embodiment of the present application.

[0031] Figure 2 is a schematic diagram of the start-up burner preheating the reformer during the start-up stage in a preferred embodiment of the present application.

[0032] Figure 3 is a schematic diagram of the start-up burner preheating the stack during the start-up stage in a preferred embodiment of the present application.

[0033] Figure 4 is a schematic diagram of the methanol reforming hydrogen fuel cell system in a preferred embodiment of the present application working in a steady state.

[0034] 100 reformer assembly

[0035] 110 reforming unit

[0036] 120 oxidizing unit

[0037] 200 stack

[0038] 310 start-up burner

[0039] 320 start-up burner

[0040] 410 heat exchanger

[0041] 411 first flow passage

[0042] 412 second flow passage

[0043] 413 third flow passage

[0044] 414 fourth flow passage

[0045] 420 heat exchanger

[0046] 421 first flow passage

[0047] 422 second flow passage

[0048] 430 heat exchanger

[0049] 440 heat exchanger

[0050] 500 circulation pump DETAILED DESCRIPTION

[0051] Unless otherwise defined, technical and scientific terms used in the claims and specification of this patent shall have the meanings that are commonly understood by one of ordinary skill in the art to which this patent belongs. The terms "first," "second," and similar terms are used herein to describe various components, but do not imply a particular order or priority of use or importance. The terms "a" and "an" and "one or more" are defined to mean one or more than one, unless otherwise indicated. The terms "including," "has," "having" and "comprising" are defined to be open terms that do not exclude additional, unrecited elements or method steps. The terms "another," "additional" and the like are defined to mean at least one, unless otherwise indicated.

[0052] Figure 1The figure shows a simplified schematic diagram of the overall architecture of a methanol reforming hydrogen fuel cell system, which is a preferred embodiment. The methanol reforming hydrogen fuel cell system primarily consists of a reformer assembly 100, a fuel cell stack 200, a starter burner 310, a starter burner 320, heat exchangers 410, 420, 430, and 440. Furthermore, it includes various pipelines, pumps, and fans connecting these major components. Pipelines include air, fuel, hot air, heat transfer fluid, and flue gas lines, and pumps include circulation pumps and liquid inlet pumps. Sensors, such as pressure and temperature sensors, are installed as needed in the methanol reforming hydrogen fuel cell system. The various modules and components of the methanol reforming hydrogen fuel cell system are assembled into a single unit using bolts, compression fittings, and hose clamps.

[0053] The reformer assembly 100 consists of a reforming unit 110 and an oxidizing unit 120. The oxidizing unit 120 oxidizes methanol to generate heat, which is transferred to the adjacent reforming unit 110 to maintain the required temperature for the reforming reaction. The reforming unit 110 reforms the methanol-water feedstock to produce a reformed gas primarily composed of hydrogen.

[0054] The reforming unit 110 is a microchannel reactor, which can be composed of two flat plates, and the surface of the microchannel is coated with a catalyst. The oxidation unit 120 is also a microchannel reactor, which is also composed of two flat plates. The microchannel reactor as the reforming unit and the microchannel reactor as the oxidation unit are repeatedly overlapped to form a complete reformer assembly 100. Specifically, the two sides of a microchannel reaction plate have different functions, one side is used as a reforming function, and the other side is used as an oxidation function. The reforming sides of the two reaction plates are overlapped to form a reforming unit 110. The oxidation sides of the two reaction plates are overlapped to form an oxidation unit 120. After all the reaction plates of the reformer are overlapped in sequence, a form of repeated overlap of the reforming unit and the oxidation unit 1+1 is formed.

[0055] The stack assembly includes four flow channels: air flow channels, reforming flow channels, residual flow channels, and heat transfer liquid circulation channels. The reforming flow channels are connected to the reforming unit 110 through pipelines, and a heat exchanger flow channel is also included in between. After the reforming gas flows out of the reforming unit 110, it is cooled to a temperature suitable for the reaction through the heat exchanger, and then passes through the reforming flow channel to the stack. After being heated by the heat exchanger, the air enters the stack assembly through the air flow channel, and finally mixed with the reforming gas, an electrochemical reaction occurs under the action of the catalyst to generate electrical energy and heat energy. The electrical energy is output to the battery, the power grid, or directly supplied to electrical appliances through wires. The unreacted hydrogen and other gases in the reforming gas are discharged from the residual flow channel to the oxidation unit 120, and are oxidized again to generate heat.

[0056] The heat transfer fluid circulation channel is used for the circulation of heat transfer fluid, and the heat transfer fluid is preferably triethylene glycol or D12 synthetic thermal oil. D12 is a commercially available product of Eastman Chemical Company. In the start-up preheating stage, the heat conducting liquid absorbs the heat generated by the start-up burner 320, and through the heat conducting liquid circulation channel, the heat is transferred to the stack 200 to rapidly reach the required temperature for hydrogen reaction. In the steady state stage, the heat generated by the hydrogen and oxygen reaction is taken out of the stack 200 by the heat conducting liquid into the heat exchanger 410, which is used to heat the reforming gas, methanol water, etc. before the reaction. In this stage, the heat conducting liquid in the stack 200 is used as a cooling liquid.

[0057] In the start-up preheating stage of the fuel cell, the start-up burner is heated by electricity to heat itself, and then air and methanol are introduced. The combustion of methanol produces a large amount of hot gas, which is supplied to the reformer assembly 100 and the stack 200 through the pipeline, so that the reformer assembly 100 and the stack 200 are heated to their respective working temperatures. A start-up burner can be used in two parallel paths, one of which supplies heat to the reformer assembly 100, and the other of which supplies heat to the stack 200. More preferably, two independent start-up burners can be used, such as Figure 1 the start-up burner 310 and the start-up burner 320. The start-up burner 310 supplies heat to the reformer assembly 100, and the start-up burner 320 supplies heat to the stack 200. Because the required working temperatures of the reformer and the stack are different, two start-up burners are used to supply heat separately, which can accurately control the heating temperature and the heating time at the same time, thereby improving the heating efficiency and reducing the waiting time.

[0058] The methanol reforming hydrogen fuel cell system uses heat exchangers in multiple places. The heat exchanger 410 is located between the reformer assembly 100 and the stack 200, and a four-way flow channel coupling heat exchanger is used, which includes four flow channels: hot gas flow channel, heat conducting liquid flow channel, methanol water gasification flow channel, and reforming gas flow channel. In the start-up stage, the first flow channel 411 is used as a hot gas flow channel for the hot gas flow generated by the start-up burner 320 to pass through, and the hot gas flow releases heat to other flow channels. The second flow channel 412 is used as a heat conducting liquid flow channel for the heat conducting liquid to pass through, and the heat conducting liquid absorbs heat in the second flow channel 412 and then transfers the heat to the stack 200. The third flow channel 413 is used as a methanol water gasification flow channel, and the liquid methanol water raw material flows through this flow channel and is partially or completely gasified after being heated, and then is input to the reforming unit 110 through the methanol water pipeline for reforming to obtain reforming gas. The fourth flow channel 414 is used as a reforming gas flow channel, and the reforming gas output from the reforming unit 110 passes through the fourth flow channel 414 and is cooled before being input to the stack 200 for power generation.

[0059] The heat exchanger 420 is arranged between the stack 200 and the heat exchanger 410 by means of pipelines, and the heat exchanger 420 adopts a two-way flow channel coupling heat exchanger. The first flow channel 421 of the heat exchanger 420 is communicated with the first flow channel 411 of the heat exchanger 410, and both of them are part of the heat conducting liquid circulation pipeline. The second flow channel 422 of the heat exchanger 420 is used for passing air, which exchanges heat with the heat conducting liquid in the first flow channel 421, and the air is heated; the oxygen in the air is catalytically oxidized with the hydrogen in the hot reforming gas.

[0060] The heat exchanger 430 is arranged between the heat exchanger 410 and the heat exchanger 420 by means of pipelines, and is also part of the heat conducting liquid circulation pipeline. The heat exchanger 430 is used for cooling the reforming gas to a temperature suitable for the oxidation-reduction reaction. The heat exchanger 430 can adopt a forced air cooling device.

[0061] The heat exchanger 440 is arranged between the fuel flow channel and the flue gas flow channel, as shown in Figure 1 More specifically, the first flow channel of the heat exchanger 440 is communicated with the third flow channel 413 of the heat exchanger 410 through pipelines, and the second flow channel of the heat exchanger 430 is used for passing the high-temperature flue gas generated by the oxidation unit 120. The heat in the high-temperature flue gas is absorbed by the heat exchanger 440 and used to further heat the methanol water fuel to make it completely gasified, and then enter the reforming unit 110 for reforming. The addition of the heat exchanger 440 in the methanol reforming hydrogen fuel cell system makes the heat in the high-temperature flue gas (tail gas) be reused, and the methanol water vapor is reheated to a higher temperature, thereby improving the efficiency of the system.

[0062] The above describes in detail the connection mode and function of each main working unit of the methanol reforming hydrogen fuel cell system. Next, the collaborative working process among them will be described in detail in combination with different working stages of the methanol reforming hydrogen fuel cell system. The working stages of the system include a starting stage, a steady state stage and a shutdown stage.

[0063] Starting stage

[0064] In the starting stage of the methanol reforming hydrogen fuel cell system, the starting burner 310 and the starting burner 320 both participate in the work.

[0065] The working process of the starting burner 310 is shown in Figure 2 The starting burner 310 is electrically heated to a certain temperature, fuel and air are introduced, a catalytic oxidation reaction is generated, high-temperature gas is obtained, the high-temperature gas enters the reformer oxidation unit 120 through pipelines, then passes through the heat exchanger 440, and finally is exhausted. When passing through the heat exchanger 440, the heat in the high-temperature flue gas is recycled and reused.

[0066] The working process of the starting burner 320 is shown in Figure 3The electrically heated start-up burner 320 is connected to the first flow channel 411 of the heat exchanger 410. When the start-up burner 320 reaches a certain temperature, fuel and air are introduced to generate a catalytic oxidation reaction to obtain high-temperature gas, which is introduced into the first flow channel 411 of the heat exchanger 410 through a pipeline to heat the heat-conducting liquid in the second flow channel 412. The heat-conducting liquid is introduced into the heat exchanger 430 from the second flow channel 412 through the circulating pump 500, and then passes through the first flow channel 421 of the heat exchanger 420. Then, the heat-conducting liquid is introduced into the electric pile 200 to heat the electric pile. Finally, the heat-conducting liquid returns to the second flow channel 412 to form a heat-conducting liquid heating cycle.

[0067] Steady state phase

[0068] When the methanol reforming hydrogen fuel cell system is in the steady state operation phase, the start-up burner 310 and the start-up burner 320 stop working. The entire methanol reforming hydrogen fuel cell system works in the following lines, as shown in Figure 4

[0069] Line one: endothermic vaporization of methanol water

[0070] First, the methanol water is introduced into the third flow channel 413 of the heat exchanger 410, and the methanol water exchanges heat with the high-temperature heat-conducting liquid in the second flow channel 412 and the high-temperature reforming gas in the fourth flow channel 414. After absorbing heat, the methanol water is close to complete vaporization.

[0071] Then, the methanol water from the heat exchanger 410 enters the heat exchanger 440, and after being heated again, the methanol water vapor is heated to 370°C, at which point it is completely vaporized, and finally enters the reforming unit 110.

[0072] Line two: obtaining and reaction of reforming gas

[0073] First, under the action of the catalyst, the methanol water gas in the reforming unit 110 undergoes a reduction reaction to produce reforming gas (high-concentration hydrogen gas).

[0074] Then, the reforming gas is cooled to about 200°C and introduced into the fourth flow channel 414, and then cooled again to about 160°C and introduced into the electric pile 200 to generate electricity.

[0075] Line three: introduction and heating of air required by the electric pile

[0076] The air is generated by an air pump and introduced into the second flow channel 422 of the heat exchanger 420. After being heated by the heat-conducting liquid in the first flow channel 421, the air is introduced into the electric pile 200. The oxygen in the air reacts with the hydrogen in the reforming gas to generate electric energy and heat energy.

[0077] Line four: absorption and reuse of flue gas heat

[0078] ​The remaining unreacted hydrogen is discharged from the fuel cell stack 200, mixed with air and then enters the oxidation unit 120; under the action of the catalyst, an oxidation reaction occurs, providing heat for the reduction reaction occurring in the reforming unit 110, and the high-temperature exhaust gas is cooled by heat exchanger 440 and then discharged.

[0079] The heat exchanger 440 here allows the high-temperature exhaust gas to be reused to reheat the methanol water vapor to a higher temperature, closer to the temperature required for the reaction, thereby improving the thermal efficiency of the fuel cell system.

[0080] Line 5: Coolant circulation line

[0081] During this steady-state phase, the thermal fluid acts as a coolant, carrying the large amount of heat generated by the electrochemical reaction within the fuel cell stack 200 out of the fuel cell stack 200. The coolant (thermal fluid) is triethylene glycol, which has a boiling point of 285°C and is suitable as a heat transfer medium in fuel cells.

[0082] The coolant circulation path is as follows: circulation pump 500 → first flow channel 421 of heat exchanger 420 → fuel cell stack 200 → second flow channel 412 of heat exchanger 410 → heat exchanger 430 → circulation pump 500, where heat exchanger 430 is used to dissipate excess heat.

[0083] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A methanol reforming hydrogen fuel cell system, characterized by, The application relates to a fuel cell system, comprising: a reformer formed by repeatedly interlacing a plurality of micro-channel reforming units and a plurality of micro-channel oxidation units; each of the oxidation units oxidizes methanol to generate heat and transfers the heat to an adjacent reforming unit; each of the reforming units reforms a methanol water raw material to generate a reforming gas mainly composed of hydrogen; a stack connected to the reformer through a pipeline, the stack being used to receive the reforming gas and react the reforming gas with air to generate electric energy; a start-up burner used to preheat the oxidation units and the stack in a start-up stage of the fuel cell, the start-up burner comprising two independent start-up burners, wherein a first start-up burner is used to heat the oxidation units and a second start-up burner is used to heat the stack; a plurality of heat exchangers used for heat exchange and transfer in the fuel cell system; the heat exchangers comprise a first heat exchanger, which is a four-way flow channel coupling heat exchanger, wherein a first flow channel of the first heat exchanger is used for a hot gas flow generated by the second start-up burner to pass through; a second flow channel of the first heat exchanger is used for a heat transfer liquid to pass through, the heat transfer liquid transferring heat to the stack; a third flow channel of the first heat exchanger is used for a methanol water raw material to pass through and heat the methanol water raw material; a fourth flow channel of the first heat exchanger is used for the reforming gas to pass through and cool the reforming gas; the heat exchangers comprise a second heat exchanger, which is a two-way flow channel coupling heat exchanger, wherein a first flow channel of the second heat exchanger is used for the heat transfer liquid to pass through; a second flow channel of the second heat exchanger is used for air required for a reaction in the stack to pass through and heat the air; the heat exchangers comprise a third heat exchanger connected to a heat transfer liquid pipeline between the first heat exchanger and the second heat exchanger, the third heat exchanger being used to regulate the temperature of the heat transfer liquid; the heat exchangers comprise a fourth heat exchanger used to recover heat in flue gas of the oxidation units and transfer the heat to the first heat exchanger.

2. A methanol reforming hydrogen fuel cell system according to claim 1, wherein, The heat generated by the start-up burner is at least divided into two parallel paths, wherein a first path is used to heat the oxidation units and a second path is used to heat the stack.

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