A method for preparing and purifying hydrogen for fuel cells and a system device thereof

Abstract

The present invention relates to the field of hydrogen purification, and in particular to a method for preparing and purifying hydrogen for fuel cells and a system device thereof. The raw hydrogen is respectively heat exchanged with the product gas and the regenerated gas after the expansion heat exchange through the heat exchange mechanism I, i.e., the N-stage heat exchanger, and a part of the hydrogen is separated and enters the refrigeration mechanism to obtain supercooled hydrogen. The raw hydrogen and the supercooled hydrogen are cooled by the heat exchange mechanism II and then enter the adsorption mechanism. The impurities in the raw hydrogen are purified to meet the requirements of hydrogen for fuel cells through the low adsorption mechanism, thereby obtaining hydrogen product gas for fuel cells; the cold hydrogen is heated by the heater, and the heated hydrogen is used as the medium for regeneration and reheating of the low-temperature adsorption mechanism and thermal regeneration. The purified product gas returns to the heat exchange mechanism I to exchange heat with the raw hydrogen, and is output to the storage device or other processing equipment after heating. The impurity content S in the obtained product gas is less than 0.004ppm, and CO is less than 0.02ppm, which ensures the long-term stable operation of the fuel cell.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen purification, and in particular to a method for preparing and purifying hydrogen for fuel cells and a system device thereof. Background Art

[0002] Proton membrane fuel cell is a new type of fuel cell, whose electrolyte is a solid organic membrane, which can conduct protons under humidification. Proton membrane fuel cell uses hydrogen as fuel and can convert hydrogen into electricity. It is a very important clean energy. Its characteristics require that the content of some impurities such as CO and sulfide in the hydrogen entering the fuel cell is very low, below the ppm level, reaching the ppb level, which is lower than the content standard of conventional pure hydrogen and high-purity hydrogen.

[0003] At present, the national standard for pure hydrogen content is 99.99%, of which the CO content is less than 5ppm. The hydrogen content in high-purity hydrogen is greater than 99.999%, the CO content is less than 1ppm, and there is no requirement for the S content. Therefore, it is necessary to purify the hydrogen produced by the existing hydrogen production equipment to purify CO, S compounds, alcohols, aldehydes and other oxygen-containing compounds in the hydrogen with high precision.

[0004] Proton membrane fuel cells have relatively high requirements for hydrogen purification, but because conventional adsorption purifiers have very small adsorption capacity for ppb-level hydrogen sulfide and carbon monoxide at room temperature, large amounts of adsorbent are used, hydrogen recovery rates are low, and it is even impossible to achieve the accuracy of removing hydrogen sulfide from hydrogen to 4ppb and carbon monoxide to below 20ppb.

[0005] Chinese patent application publication number CN102491272B discloses a high-purity hydrogen purification process, which uses room temperature adsorption plus low-temperature adsorption to obtain high-purity hydrogen of more than 99.99999%, and the cold source of the low-temperature adsorption comes from a liquid nitrogen evaporator.

[0006] Chinese patent application publication number CN101530717A discloses a method for continuously producing ultrapure gas by low-temperature adsorption, which uses liquid nitrogen as a cold source to cool hydrogen to -160 to -190°C through a liquid nitrogen evaporator to obtain ultrapure gas by low-temperature adsorption.

[0007] Chinese patent application publication number CN107364832A discloses a low-temperature hydrogen purification device and control method, which purifies hydrogen by catalytic deoxygenation, room-temperature adsorption denitrification and low-temperature adsorption purification, and the cold source of the low-temperature adsorption is liquid nitrogen.

[0008] None of the above disclosed purification schemes involve purifying the sulfides in hydrogen to 4 ppb, so that the hydrogen cannot reach the purification target of hydrogen for fuel cells. In addition, because liquid nitrogen is used as a continuous cold source for low-temperature adsorption, liquid nitrogen is easy to evaporate and requires special liquid nitrogen storage equipment for storage and transportation. At the same time, the continuous use of liquid nitrogen also causes technical problems such as high purification costs. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a method for preparing and purifying hydrogen for fuel cells and a system device thereof, so as to obtain hydrogen that meets the fuel cell standards, wherein the impurity content S in the hydrogen is less than 0.004ppm, and the CO is less than 0.02ppm, thereby ensuring the long-term stable operation of the fuel cell; and there is no need for continuous liquid nitrogen as a cold source. At the same time, the energy after the turbine expansion of part of the raw hydrogen is used to drive a fan to pressurize the regenerated gas so that the regenerated gas reaches a certain temperature, thereby reducing the energy consumption and cost of the system.

[0010] A method for preparing and purifying hydrogen for fuel cells in the present invention to solve the above technical problems is characterized by comprising the following steps:

[0011] (1) The raw hydrogen gas is cooled by the heat exchange mechanism I and the cooler to become low-temperature raw hydrogen gas;

[0012] (2) A portion of the low-temperature raw hydrogen gas, which accounts for 10% to 40% of the total gas mass percentage, enters the refrigeration mechanism to obtain cold hydrogen gas;

[0013] (3) The cold hydrogen enters the adsorption mechanism as regeneration gas after heat exchange through the heat exchange mechanism II, and / or is heated by the heater as medium gas for regeneration and thermal regeneration of the low-temperature adsorption mechanism;

[0014] (4) Another portion of the low-temperature raw hydrogen gas is cooled together with the cold hydrogen gas in step (2) by the heat exchange mechanism II and then enters the low-temperature adsorption mechanism to purify the impurities in the raw hydrogen gas to meet the requirements of hydrogen gas for fuel cells.

[0015] The raw gas is hydrogen with a pressure of 1.6-4.0 MPa after purification, a purity of more than 99.99%, and trace impurity indicators that do not meet the requirements for hydrogen used in fuel cells. The specific content of trace impurities in the product gas needs to meet the national standard for pure hydrogen.

[0016] The temperature of the low-temperature raw hydrogen is ≤-150~-160℃, and the cooler is a liquid nitrogen evaporative cooler. A cooler is set in front of the refrigeration mechanism to operate in the initial stage of operation, which cools the hydrogen entering the refrigeration mechanism to -150~-160℃ to ensure the operation of the hydrogen refrigeration mechanism in the initial stage of operation.

[0017] In the step (3), the cold hydrogen is heated to 120-300°C by a heater as a regeneration medium; the cold hydrogen is regenerated by heat exchange mechanism II to 30-200°C, and 60-80°C in the optimized solution.

[0018] In the step (4), the cold hydrogen is cooled to -170 to -190°C by the heat exchange mechanism II and then enters the low-temperature adsorption mechanism.

[0019] A system device for preparing and purifying hydrogen for fuel cells in the present invention comprises a heat exchange mechanism I, a heat exchange mechanism II, a cooling mechanism, an adsorption mechanism, a heater and a cooler. The heat exchange mechanism I is provided with N-stage heat exchangers, each heat exchanger is connected in series, the heat exchange mechanism I is connected to the cooler and the adsorption mechanism, the heat exchange mechanism II is connected to the cooling mechanism and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is connected to the heater, the heat exchange mechanism II and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I. The above devices are interconnected by pipelines.

[0020] The heat exchange mechanism I includes N stages of heat exchangers, where N≥1.

[0021] The cooler is a start-up liquid nitrogen evaporative cooler.

[0022] The refrigeration mechanism is a fan-operated turbine expansion refrigerator. The main principle of the fan-operated turbine expansion refrigerator is to use a certain pressure of gas in the turbine expansion machine to perform adiabatic expansion to work externally and consume the internal energy of the gas itself, so that the gas itself is strongly cooled to achieve the purpose of refrigeration. The structure is conventional equipment.

[0023] The raw hydrogen passes through the heat exchange mechanism I, i.e., the N-stage heat exchanger, and exchanges heat with the product gas and the regenerated gas after expansion heat exchange respectively. After the temperature is reduced, a part of the hydrogen is separated and enters the refrigeration mechanism to obtain supercooled hydrogen. The raw hydrogen and the supercooled hydrogen are cooled by the heat exchange mechanism II and then enter the adsorption mechanism. The impurities in the raw hydrogen are purified by the low adsorption mechanism to meet the requirements of hydrogen for fuel cells, thereby obtaining hydrogen product gas for fuel cells; the cold hydrogen is heated by the heater, and the heated hydrogen is used as the medium for regeneration and reheating of the low-temperature adsorption mechanism and thermal regeneration. The purified product gas returns to the heat exchange mechanism I to exchange heat with the raw hydrogen, and is output to the storage equipment or other processing equipment after cooling.

[0024] The low-temperature adsorption mechanism is composed of at least two low-temperature adsorbers connected in parallel, and adopts at least two-tower process, one tower adsorbs at low temperature, and the other tower reheats and regenerates; at any time, one adsorber is in the low-temperature adsorption step, so that the hydrogen product is continuously output, and the other adsorber is in one of the reheating, heating regeneration or temperature reduction precooling steps; wherein the operation is completed by a combination of programmable valves, flow meters and regulating valves, and the settings of each programmable valve, flow meter and regulating valve are conventional, and the adsorbent used is a conventional adsorbent.

[0025] The regeneration step in the adsorption mechanism can make the purification proceed continuously. After the low-temperature adsorber has adsorbed for a certain period of time, it switches to the regeneration heating step. The regeneration heating step is to use the low-pressure subcooled hydrogen after the turbine expansion refrigerator to recover the cold through a multi-stage heat exchanger as regeneration gas. The regeneration gas is pressurized by the fan driven by the turbine expansion refrigerator and then heated to 60-80°C.

[0026] Two or more adsorbers form an adsorption unit. Depending on the difficulty of desorption of the adsorbed impurities, the regeneration gas can directly enter the adsorber in the regeneration step for heating and regeneration at this temperature, or it can be heated to 120-300°C by a heater and enter the adsorber in the regeneration step to heat and regenerate the adsorbent. That is, after the adsorbent is heated and regenerated, it switches to the cold blowing step. The cold blowing step uses a small part of the product as the cold blowing gas. The gas after the cold blowing is mixed with most of the product hydrogen after the cold is recovered by the multi-stage heat exchanger, and after heat exchange with the raw hydrogen, it is output as the final product at room temperature.

[0027] When N=1, the heat exchange mechanism I is provided with one heat exchanger, the heat exchange mechanism II is provided with one heat exchanger, the heat exchange mechanism I is connected to the cooler and the adsorption mechanism, and the heat exchange mechanism II is respectively connected to the cooling mechanism, the adsorption mechanism and the cooler; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is respectively connected to the heater, the heat exchange mechanism II and the adsorption mechanism; wherein a regulating valve is provided between the cooler and the heat exchange mechanism II, and a flow meter is provided between the cooler and the cooling mechanism.

[0028] When N=5, the heat exchange mechanism I is provided with 5 heat exchangers, and the heat exchange mechanism II is provided with 1 heat exchanger, namely, the first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger and the fifth-stage heat exchanger. The heat exchange mechanism II is the sixth-stage heat exchanger. The first-stage heat exchanger is connected to the second-stage heat exchanger, the second-stage heat exchanger is connected to the third-stage heat exchanger, the third-stage heat exchanger is connected to the fourth-stage heat exchanger, the fourth-stage heat exchanger is connected to the cooler, the cooler is connected to the fifth-stage heat exchanger, the fifth-stage heat exchanger is respectively connected to the sixth-stage heat exchanger, the cooling mechanism and the second-stage heat exchanger, the sixth-stage heat exchanger is connected to the adsorption mechanism, the cooling mechanism is respectively connected to the adsorption mechanism, the heater, the sixth-stage heat exchanger and the second-stage heat exchanger; the third-stage heat exchanger is connected to the adsorption mechanism, the fourth-stage heat exchanger is connected to the adsorption mechanism; and the first-stage heat exchanger is also connected to the third-stage heat exchanger and the adsorption mechanism. To improve the heat exchange efficiency, a 6-stage heat exchanger is used. The heat exchanger may be a multi-pass heat exchanger, functioning like a 5-stage heat exchanger.

[0029] A regulating valve is provided between the fifth-stage heat exchanger and the sixth-stage heat exchanger; and a flow meter is provided between the fifth-stage heat exchanger and the cooling mechanism.

[0030] In the present invention, the raw hydrogen is subjected to multi-stage heat exchange and turbine expansion refrigeration to obtain a low-temperature adsorption method of a continuous cold source, and impurities such as sulfide and carbon monoxide are removed from the hydrogen to obtain hydrogen with an impurity content lower than the requirement for hydrogen used in fuel cells. Low-temperature adsorption is used to purify hydrogen to improve the purification accuracy and capacity of the adsorbent. The low-temperature cold source is hydrogen throttling and pressure reduction or hydrogen pressure reduction plus turbine refrigeration. The adsorbent is used to adsorb nitrogen, sulfur compounds, CO, CO2, alcohols and other oxygen-containing compounds in hydrogen in the range of -20 to -170°C to obtain hydrogen that meets the requirements of fuel cells, with sulfur less than 0.004ppm and CO less than 0.02ppm, to ensure the long-term stable operation of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0032] Figure 1 This is a schematic diagram of the structure of Embodiment 4 of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of Embodiment 5 of the present invention.

[0034] The specific symbols in the figure are:

[0035] 1. First stage heat exchanger, 2. Second stage heat exchanger, 3. Third stage heat exchanger, 4. Fourth stage heat exchanger, 5. Fifth stage heat exchanger, 6. Sixth stage heat exchanger, 7. Cooling mechanism, 7-1. Fan of cooling mechanism, 8. Adsorber, 9. Flow meter, 10. Regulating valve, 11. Program-controlled valve, 12. Heater, 13. Cooler, 14. Heat exchange mechanism II DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments:

[0037] Example 1

[0038] A method for preparing and purifying hydrogen for fuel cells, the specific steps are as follows:

[0039] (1) The raw hydrogen gas is cooled by the heat exchange mechanism I and the cooler to become low-temperature raw hydrogen gas; the raw gas is hydrogen gas with a pressure of 2.5 MPa after purification, a purity of more than 99.99%, and trace impurity indicators that do not meet the requirements for hydrogen gas used in fuel cells. The specific content of trace impurities in the product gas needs to meet the national standard for pure hydrogen.

[0040] The temperature of low-temperature raw hydrogen is ≤-150°C, and the cooler is a liquid nitrogen evaporative cooler. A cooler is set in front of the refrigeration mechanism to cool the hydrogen entering the refrigeration mechanism to -150°C, ensuring the operation of the hydrogen refrigeration mechanism in the initial stage of the start-up.

[0041] (2) A portion of the low-temperature raw hydrogen gas, which accounts for 10% of the total gas mass percentage, enters the refrigeration mechanism to obtain cold hydrogen gas;

[0042] (3) The cold hydrogen is heat-exchanged through heat exchange mechanism II and enters the low-temperature adsorption mechanism as regeneration gas, and / or is heated by the heater as the medium gas for regeneration, reheating and thermal regeneration of the low-temperature adsorption mechanism; the cold hydrogen is heated to 120°C by the heater and used as the regeneration medium; or the cold hydrogen is heat-exchanged to 30°C through heat exchange mechanism II for regeneration.

[0043] (4) Another part of the low-temperature raw hydrogen gas is cooled by the heat exchange mechanism II together with the cold hydrogen gas in step (2) and then enters the low-temperature adsorption mechanism to purify the impurities in the raw hydrogen gas to meet the requirements of hydrogen gas for fuel cells. The cold hydrogen gas is cooled to -170°C by the heat exchange mechanism II and then enters the low-temperature adsorption mechanism.

[0044] Example 2

[0045] A method for preparing and purifying hydrogen for fuel cells, the specific steps are as follows:

[0046] (1) The raw hydrogen gas is cooled by the heat exchange mechanism I and the cooler to become low-temperature raw hydrogen gas; the raw gas is hydrogen gas with a pressure of 1.6 MPa after purification, a purity of more than 99.99%, and trace impurity indicators that do not meet the requirements for hydrogen gas used in fuel cells. The specific content of trace impurities in the product gas needs to meet the national standard for pure hydrogen.

[0047] The temperature of low-temperature raw hydrogen is ≤-160°C, and the cooler is a liquid nitrogen evaporative cooler. A cooler is set in front of the refrigeration mechanism to cool the hydrogen entering the refrigeration mechanism to -160°C, ensuring the operation of the hydrogen refrigeration mechanism in the initial stage of the start-up.

[0048] (2) A portion of the low-temperature raw hydrogen gas, which accounts for 40% of the total gas mass percentage, enters the refrigeration mechanism to obtain cold hydrogen gas;

[0049] (3) The cold hydrogen enters the adsorption mechanism as the regeneration gas after heat exchange through the heat exchange mechanism II, and / or is heated by the heater as the medium gas for regeneration, reheating and thermal regeneration of the low-temperature adsorption mechanism; the cold hydrogen is heated to 300°C by the heater as the regeneration medium; or the cold hydrogen is heated to 200°C by the heat exchange mechanism II for regeneration.

[0050] (4) Another part of the low-temperature raw hydrogen gas is cooled by the heat exchange mechanism II together with the cold hydrogen gas in step (2) and then enters the low-temperature adsorption mechanism to purify the impurities in the raw hydrogen gas to meet the requirements of hydrogen gas for fuel cells. The cold hydrogen gas is cooled to -190°C by the heat exchange mechanism II and then enters the low-temperature adsorption mechanism.

[0051] Example 3

[0052] A method for preparing and purifying hydrogen for fuel cells, the specific steps are as follows:

[0053] (1) The raw hydrogen gas is cooled by the heat exchange mechanism I and the cooler to become low-temperature raw hydrogen gas; the raw gas is hydrogen gas with a pressure of 4.0 MPa, a purity of more than 99.99% after purification, and trace impurity indicators that do not meet the requirements for hydrogen gas used in fuel cells. The specific content of trace impurities in the product gas needs to meet the national standard for pure hydrogen.

[0054] The temperature of low-temperature raw hydrogen is ≤-155°C, and the cooler is a liquid nitrogen evaporative cooler. A cooler is set in front of the refrigeration mechanism to cool the hydrogen entering the refrigeration mechanism to -155°C, ensuring the operation of the hydrogen refrigeration mechanism in the initial stage of the start-up.

[0055] (2) A portion of the cryogenic raw hydrogen gas, which accounts for 25% of the total gas mass percentage, enters the refrigeration mechanism to obtain cold hydrogen gas;

[0056] (3) The cold hydrogen enters the adsorption mechanism as the regeneration gas after heat exchange through the heat exchange mechanism II, and / or is heated by the heater as the medium gas for regeneration, reheating and thermal regeneration of the low-temperature adsorption mechanism; the cold hydrogen is heated to 240°C by the heater as the regeneration medium; the cold hydrogen is heat exchanged to 120°C by the heat exchange mechanism II for regeneration.

[0057] (4) Another part of the low-temperature raw hydrogen gas is cooled by the heat exchange mechanism II together with the cold hydrogen gas in step (2) and then enters the low-temperature adsorption mechanism to purify the impurities in the raw hydrogen gas to meet the requirements of hydrogen gas for fuel cells. The cold hydrogen gas is cooled to -180°C by the heat exchange mechanism II and then enters the low-temperature adsorption mechanism.

[0058] Example 4

[0059] A system device for preparing and purifying hydrogen for fuel cells includes a heat exchange mechanism I, a heat exchange mechanism II, a cooling mechanism, an adsorption mechanism, a heater and a cooler. The heat exchange mechanism I is provided with a first-stage heat exchanger, and each heat exchanger is connected in series. The heat exchange mechanism I is connected to the cooler and the adsorption mechanism, and the heat exchange mechanism II is connected to the cooling mechanism and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is connected to the heater, the heat exchange mechanism II and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I. The above devices are interconnected by pipelines.

[0060] Specifically, the heat exchange mechanism I is provided with a heat exchanger, and the heat exchange mechanism II is provided with a heat exchanger. The heat exchange mechanism I is connected to the cooler and the adsorption mechanism, and the heat exchange mechanism II is respectively connected to the cooling mechanism, the adsorption mechanism and the cooler; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is respectively connected to the heater, the heat exchange mechanism II and the adsorption mechanism; wherein a regulating valve is provided between the cooler and the heat exchange mechanism II, and a flow meter is provided between the cooler and the cooling mechanism.

[0061] like Figure 1 As shown, the continuous operation system consists of 2 heat exchangers, 2 or more adsorbers and corresponding program-controlled valves, 1 fan brake turbine expansion refrigerator, start-up cooler, heater, flow meter, and regulating valve.

[0062] Hydrogen with a purity of more than 99.99% and trace impurity index that does not meet the requirements for hydrogen used in fuel cells is used as raw gas and enters the system at a pressure of 1.6-4.0MPa and a temperature of 30-40°C. First, it exchanges heat with the mixed gas of product gas and regenerated cold blow gas from the adsorber in the first-stage heat exchanger 1, which reduces its own temperature while also increasing the temperature of the product gas.

[0063] The low-temperature raw gas coming out of the heat exchanger 1 is controlled by the flow meter 9 and the regulating valve 10 to separate 10% to 40% of the raw gas with a temperature lower than -150 to -160°C and enter the fan brake turbine expansion refrigerator 7 to obtain supercooled hydrogen at -200°C. This part of the supercooled hydrogen is heat exchanged with the low-temperature raw gas in the heat exchanger 2 of the heat exchange mechanism II, so that the raw gas is reduced to -170 to -180°C and then enters the low-temperature adsorber 8. The impurities in the raw hydrogen are purified by low-temperature adsorption to meet the requirements of hydrogen for fuel cells, thereby obtaining product hydrogen for fuel cells. The low-temperature product hydrogen gas returns to the heat exchanger 1 of the heat exchange mechanism I for heat exchange with the raw hydrogen, and is output to the storage device or other processing equipment after reheating.

[0064] When the system just starts running, the startup cooler 13 is provided with a cold source by liquid nitrogen, so that the raw gas is reduced to -150--160°C, so that the turbine expansion refrigerator 7 is braked by the fan to obtain supercooled hydrogen at -200°C. After the subsequent system is operating normally, it is stopped.

[0065] The low-temperature adsorption mechanism 8 is composed of at least two low-temperature adsorbers connected in parallel, and adopts at least two-tower process, one tower adsorbs at low temperature, and the other tower reheats and regenerates; at any time, one adsorber is in the low-temperature adsorption step, so that the hydrogen product is continuously output, and the other adsorber is in one of the reheating, heating regeneration or cooling precooling steps; the operation is completed by a combination of programmable valves, flow meters and regulating valves, and the settings of each programmable valve, flow meter and regulating valve are conventional, and the adsorbent used is a conventional adsorbent.

[0066] The regeneration step in the adsorption mechanism can make the purification proceed continuously. After the low-temperature adsorber has adsorbed for a certain period of time, it switches to the regeneration heating step. The regeneration heating step is to recover the cold energy of the low-pressure subcooled hydrogen after the turbine expansion refrigerator through the multi-stage heat exchanger 2 as the regeneration gas. The regeneration gas is pressurized by the fan 7-1 driven by the turbine expansion refrigerator and then heated to 60-80°C.

[0067] Two or more adsorbers form an adsorption unit. Depending on the difficulty of desorption of the adsorbed impurities, the regeneration gas can directly enter the adsorber in the regeneration step for heating and regeneration at this temperature, or it can be heated to 120-300°C by the heater 12 and enter the adsorber in the regeneration step to heat and regenerate the adsorbent. After the adsorbent is heated and regenerated, it switches to the cold blowing step. The cold blowing step uses a small part of the product as the cold blowing gas. The gas after the cold blowing is mixed with most of the product hydrogen after the cold is recovered by the multi-stage heat exchanger, and after heat exchange with the raw hydrogen, it is output as the final product at room temperature.

[0068] Example 5

[0069] A system device for preparing and purifying hydrogen for fuel cells includes a heat exchange mechanism I, a heat exchange mechanism II, a cooling mechanism, an adsorption mechanism, a heater and a cooler. The heat exchange mechanism I is provided with a 5-stage heat exchanger, each heat exchanger is connected in series, the heat exchange mechanism I is connected to the cooler and the adsorption mechanism, the heat exchange mechanism II is connected to the cooling mechanism and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is connected to the heater, the heat exchange mechanism II and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I. The above devices are interconnected by pipelines.

[0070] Specifically, the heat exchange mechanism I is provided with 5 heat exchangers, and the heat exchange mechanism II is provided with 1 heat exchanger, namely, the first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger, the fourth-stage heat exchanger, the cooler, the fifth-stage heat exchanger, the sixth-stage heat exchanger, the cooling mechanism, and the second-stage heat exchanger, the sixth-stage heat exchanger, the cooling mechanism, the adsorption mechanism, the heater, the sixth-stage heat exchanger, and the second-stage heat exchanger, respectively; the third-stage heat exchanger is connected to the adsorption mechanism, the fourth-stage heat exchanger is connected to the adsorption mechanism; and the first-stage heat exchanger is also connected to the third-stage heat exchanger and the adsorption mechanism. To improve the heat exchange efficiency, a 6-stage heat exchanger is used. The heat exchanger can be a multi-channel heat exchanger, and its function is the same as that of a 5-stage heat exchanger. A regulating valve is provided between the fifth-stage heat exchanger and the sixth-stage heat exchanger; and a flow meter is provided between the fifth-stage heat exchanger and the cooling mechanism.

[0071] As an example, Figure 2 As shown, the continuous operation system consists of 6 heat exchangers, 2 or more adsorbers and corresponding program-controlled valves, 1 fan brake turbine expansion refrigerator, start-up cooler, heater, flow meter, and regulating valve.

[0072] Hydrogen with a purity of more than 99.99% and trace impurity index that does not meet the requirements for hydrogen used in fuel cells is used as raw gas and enters the system at a pressure of 1.6-4.0MPa and a temperature of 30-40°C. First, in the first-stage heat exchanger 1, it exchanges heat with the product gas after the cold is recovered by the third-stage heat exchanger 3 and the fourth-stage heat exchanger 4 and the mixed gas of the regenerated cold blow gas from the adsorber, while reducing its own temperature, and at the same time, the product gas temperature is raised to 20-30°C before output.

[0073] The raw gas coming out of the first-stage heat exchanger 1 enters the second-stage heat exchanger 2 and exchanges heat with the regenerated heating gas after the cold is recovered by the fifth-stage heat exchanger 5 and the sixth-stage heat exchanger 6. While lowering its own temperature, the temperature of the regenerated heating gas is also raised to 20-35°C.

[0074] The raw gas coming out of the second-stage heat exchanger 2 enters the third-stage heat exchanger 3 and exchanges heat with the product gas after the cold energy is recovered by the fourth-stage heat exchanger 4, so that its own temperature is further reduced to -40~-50℃.

[0075] The raw gas from the third-stage heat exchanger 3 enters the fourth-stage heat exchanger 4 to exchange heat with the product gas from the adsorber, thereby further reducing its own temperature and recovering the cold energy of the product gas.

[0076] The raw gas coming out of the fourth stage heat exchanger 4 enters the fifth stage heat exchanger 5 again, and further reduces its own temperature with the regenerated heating gas after the cold energy is recovered in the sixth stage heat exchanger 6, and at the same time recovers the cold energy of the regenerated heating gas.

[0077] The raw gas coming out of the fifth-stage heat exchanger 5 is controlled by the flow meter 9 and the regulating valve 10 to separate 10% to 40% of the raw gas with a temperature lower than -150 to -160°C and enter the fan brake turbine expansion refrigerator 7 to obtain supercooled hydrogen at -200°C. This part of the supercooled hydrogen exchanges heat with the raw gas in the sixth-stage heat exchanger 6, so that the raw gas is reduced to -170 to -180°C and then enters the low-temperature adsorber. The impurities in the raw hydrogen are purified by low-temperature adsorption to meet the requirements of hydrogen for fuel cells, thereby obtaining hydrogen for fuel cells.

[0078] When the system starts to run, the startup cooler 13 is provided with a cold source by liquid nitrogen to reduce the raw gas to -150 to -160°C. After the subsequent system is running normally, it is stopped.

[0079] The supercooled hydrogen gas from the sixth stage heat exchanger 6 after cold recovery is further recovered through the fifth stage heat exchanger 5 and the second stage heat exchanger 2, and then pressurized by the fan driven by the turbine expansion refrigeration machine (the fan of the refrigeration machine mechanism), and then heated to 60-80°C as the regeneration heating gas for the adsorber. Depending on the difficulty of desorption of the adsorbed impurities, it is heated to 120-300°C by the heater 12 and enters the adsorber in the regeneration step to heat and regenerate the adsorbent.

[0080] After the adsorbent is heated and regenerated, the process switches to the cold blowing step. In the cold blowing step, a small amount of the product is used as the cold blowing gas through the control of the flow meter 9 and the regulating valve 10. The gas after the cold blowing is mixed with the product hydrogen gas after most of the cold is recovered by the multi-stage heat exchanger, and after heat exchange with the raw hydrogen gas, it is output as the final product at room temperature.

[0081] The above description is only a preferred embodiment of the present invention, wherein the heat exchangers 1 to 6 may also be replaced by multi-channel heat exchangers.

[0082] In the present invention, the raw hydrogen is respectively heat exchanged with the product gas and the regenerated gas after the expansion heat exchange through a multi-stage heat exchanger, and after the temperature is reduced, 10% to 40% of the hydrogen with a temperature lower than -150 to -160°C is separated and enters the turbine expansion refrigerator to obtain supercooled hydrogen. The raw hydrogen is then cooled to -170 to -180°C by the heat exchanger with the supercooled hydrogen and then enters the adsorption unit. The impurities in the raw hydrogen are purified by the low-temperature adsorption unit to meet the requirements of hydrogen for fuel cells, thereby obtaining hydrogen product gas for fuel cells. The raw hydrogen is reduced in temperature by the heat exchange step, and a part of the hydrogen enters the refrigeration step to obtain supercooled hydrogen. The raw hydrogen is then heat exchanged with the supercooled hydrogen and then enters the adsorption step. The adsorption step purifies the impurities in the raw hydrogen to meet the requirements of hydrogen for fuel cells.

[0083] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which will fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A system device for preparing and purifying hydrogen for fuel cells, used in a method for preparing and purifying hydrogen for fuel cells, characterized in that : The device includes a heat exchange mechanism I, a heat exchange mechanism II, a cooling mechanism, an adsorption mechanism, a heater and a cooler. The heat exchange mechanism I is provided with N-stage heat exchangers, each heat exchanger is connected in series, the heat exchange mechanism I is connected to the cooler and the adsorption mechanism, the heat exchange mechanism II is connected to the cooling mechanism and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is connected to the heater, the heat exchange mechanism II and the adsorption mechanism respectively, and is also connected to the cooler or the heat exchange mechanism I; the low-temperature adsorption mechanism is composed of at least two low-temperature adsorbers connected in parallel, and at any time, one adsorber is in the low-temperature adsorption step, so that the hydrogen product is continuously output, and the other adsorber is in one of the steps of reheating, heating regeneration or cooling precooling; wherein the operation is completed by a combination of a programmable valve, a flow meter and a regulating valve; A method for preparing and purifying hydrogen for fuel cells comprises the following steps: (1) The raw hydrogen gas is cooled down to low-temperature raw hydrogen gas through the heat exchange mechanism I and the cooler. The temperature of the low-temperature raw hydrogen gas is ≤-150~-160℃; (2) A portion of the cryogenic raw hydrogen gas, which accounts for 10% to 40% of the total gas mass percentage, enters the refrigeration mechanism to obtain cold hydrogen gas; (3) The cold hydrogen enters the low-temperature adsorption mechanism as the medium gas for reheating and thermal regeneration after heat exchange through the heat exchange mechanism II, and / or is heated by the heater as the medium gas for regeneration, reheating and thermal regeneration of the low-temperature adsorption mechanism; The cold hydrogen is heated to 120-300℃ by the heater as the regeneration medium; the cold hydrogen is heated to 30-200℃ by the heat exchange mechanism II as the regeneration medium; (4) Another portion of the low-temperature raw hydrogen gas is cooled to -170~-190°C by heat exchange mechanism II together with the hydrogen gas in step (2) and then enters the low-temperature adsorption mechanism to purify the impurities in the raw hydrogen gas to meet the requirements of hydrogen gas for fuel cells.

2. A system device for preparing and purifying hydrogen for fuel cells according to claim 1, characterized in that: The heat exchange mechanism I includes N-stage heat exchangers, N≥1; the cooler is a start-up liquid nitrogen evaporative cooler, and the refrigeration mechanism is a fan-brake turbine expansion refrigerator.

3. A system device for preparing and purifying hydrogen for fuel cells according to claim 2, characterized in that: When N=1, the heat exchange mechanism I is provided with one heat exchanger, the heat exchange mechanism II is provided with one heat exchanger, the heat exchange mechanism I is connected to the cooler and the adsorption mechanism, and the heat exchange mechanism II is respectively connected to the cooling mechanism, the adsorption mechanism and the cooler; one end of the heater is connected to the adsorption mechanism, and the other end is connected to the cooling mechanism, and the heater and the adsorption mechanism form a circulation loop; the cooling mechanism is respectively connected to the heater, the heat exchange mechanism II and the adsorption mechanism; wherein a regulating valve is provided between the cooler and the heat exchange mechanism II, and a flow meter is provided between the cooler and the cooling mechanism.

4. A system device for preparing and purifying hydrogen for fuel cells according to claim 2, characterized in that: When N=5, the heat exchange mechanism I is provided with 5 heat exchangers, and the heat exchange mechanism II is provided with 1 heat exchanger, namely, a first-stage heat exchanger, a second-stage heat exchanger, a third-stage heat exchanger, a fourth-stage heat exchanger and a fifth-stage heat exchanger. The heat exchange mechanism II is a sixth-stage heat exchanger. The first-stage heat exchanger is connected to the second-stage heat exchanger, the second-stage heat exchanger is connected to the third-stage heat exchanger, the third-stage heat exchanger is connected to the fourth-stage heat exchanger, the fourth-stage heat exchanger is connected to the cooler, the cooler is connected to the fifth-stage heat exchanger, the fifth-stage heat exchanger is respectively connected to the sixth-stage heat exchanger, the cooling mechanism and the second-stage heat exchanger, the sixth-stage heat exchanger is connected to the adsorption mechanism, the cooling mechanism is respectively connected to the adsorption mechanism, the heater, the sixth-stage heat exchanger and the second-stage heat exchanger; the third-stage heat exchanger is connected to the adsorption mechanism, and the fourth-stage heat exchange mechanism is connected to the adsorption mechanism; at the same time, the first-stage heat exchanger is also connected to the third-stage heat exchanger and the adsorption mechanism.

5. A system device for preparing and purifying hydrogen for fuel cells according to claim 4, characterized in that: A regulating valve is provided between the fifth-stage heat exchanger and the sixth-stage heat exchanger; and a flow meter is provided between the fifth-stage heat exchanger and the cooling mechanism.

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