A method for purifying hydrogen

Abstract

The present invention provides a hydrogen purification method, which relates to the technical field of hydrogen purification. A hydrogen purification method comprises the following steps: S1, passing raw gas into a pressure swing adsorption column to obtain preliminary purified gas; S2, passing the preliminary purified gas into a catalytic adsorption column to obtain high-purity hydrogen; in S1, when the pressure swing adsorption column is saturated with adsorption, stop passing raw gas into the pressure swing adsorption column, and pass high-purity hydrogen into the pressure swing adsorption column to regenerate it, and after the regeneration is completed, pass the raw gas into the pressure swing adsorption column again. The hydrogen purification method provided by the present invention has a hydrogen purity of more than 99.9995v%, which meets the purity requirements of hydrogen used in hydrogen fuel cells, and is also suitable for occasions where industrial by-product hydrogen is used to cool hydrogen-cooled generators to provide hydrogen for purification.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen purification, and in particular to a hydrogen purification method. Background Art

[0002] Hydrogen fuel cells require high-purity hydrogen. The purity of hydrogen directly affects the power and life of the fuel cell. In the relevant standards, there are very strict requirements for the purity of hydrogen. Most hydrogen energy comes from fossil fuels, which have a high impurity content. The impurities mainly contain N2, O2, H2S, SO2, CH4, CO, CO2, NH3, etc. Among them, ppb-level H2S, SO2, CO, etc. have a serious impact on the performance of PEMFC, causing an irreversible and continuous decline in battery performance. Therefore, the hydrogen used in fuel cell vehicles has very strict requirements on the content of impurities such as sulfur and carbon monoxide. Therefore, the raw hydrogen cannot be directly used for fuel cell power generation. Most of them use conventional pressure swing adsorption technology to purify the hydrogen raw materials.

[0003] In the field of power generation, hydrogen is the main cooling medium for large generators. Hydrogen cooling medium can reduce the ventilation loss of generators by 6.95%, and the friction loss of the rotor surface is only 0.1 of that of air cooling medium. The heat dissipation capacity is 4 times higher than that of air, so it can slow down the high-temperature aging of generators and improve the efficiency of generators. Hydrogen-cooled generators generally use hydrogen with a purity of more than 99% for heat exchange cooling. Due to leakage and other reasons, the purity of hydrogen in the generator will slowly decrease. It is generally necessary to discharge and replenish hydrogen in the generator within a certain period of time, and replace low-concentration hydrogen with high-purity hydrogen of more than 99.99% to relatively improve the purity of hydrogen in the generator, which is of great significance to improving the safety of generator operation.

[0004] Pressure swing adsorption hydrogen purification technology is relatively mature. It uses the characteristics of activated carbon and molecular sieves that have strong adsorption capacity for impurity gases and a small amount of hydrogen adsorption to separate hydrogen from impurity gases to achieve hydrogen purification. When the activated carbon and molecular sieve are saturated with the adsorption of impurity gases, the molecular sieve purification column is depressurized, and high-purity hydrogen is introduced under vacuum, normal pressure, and room temperature to be purged, replaced, or reduced to obtain regeneration, so that it regains the ability to adsorb impurity gases. Molecular sieve adsorption purification columns generally require moderate hydrogen pressure. If the pressure is too low, the molecular sieve's adsorption efficiency and capacity for impurity gases are low, and hydrogen purification is not thorough. If the pressure is too high, the adsorption of hydrogen will cause the purification effect to deteriorate. In addition, for impurity gases with weak adsorption properties such as O2 and CO, the molecular sieve has a low adsorption capacity and poor purification effect, and the hydrogen purity is low.

[0005] The TiO2 or Al2O3 matrix supports precious metal catalysts to catalyze the reaction of oxygen and hydrogen to produce water, thus achieving deep desorption of oxygen from hydrogen. +It forms a medium-strength π-bond complex with CO, but has no such effect on CO2, N2, H2, CH4, etc., achieving highly selective adsorption and removal of CO.

[0006] Therefore, it is of great significance to seek a hydrogen purification method that can deeply desorb impurities such as N2, O2, H2S, SO2, CH4, CO, CO2, NH3, etc. in hydrogen and further reduce the harmful impurities O2 and CO in hydrogen. Summary of the invention

[0007] Based on the technical problems existing in the background technology, the present invention proposes a method for purifying hydrogen.

[0008] A method for purifying hydrogen proposed by the present invention comprises the following steps:

[0009] S1. Pass the raw gas into a pressure swing adsorption column to obtain preliminary purified gas;

[0010] S2. Pass the preliminary purified gas into a catalytic adsorption column to obtain high-purity hydrogen.

[0011] Preferably, in S1, when the pressure swing adsorption column is saturated with adsorption, the introduction of raw gas into the pressure swing adsorption column is stopped, and high-purity hydrogen is introduced into the pressure swing adsorption column to regenerate it. After the regeneration is completed, the raw gas is introduced into the pressure swing adsorption column again.

[0012] Preferably, in S2, when the catalytic adsorption column is saturated with adsorption, the introduction of the preliminary purified gas into the catalytic adsorption column is stopped, and the catalytic adsorption column is regenerated. After the regeneration is completed, the preliminary purified gas is introduced into the catalytic adsorption column again.

[0013] More preferably, the regeneration treatment comprises introducing 150° C. high-purity hydrogen or evacuating the chamber.

[0014] Preferably, in S1, the raw gas includes impurity gas and hydrogen; the impurity gas includes one or more of N2, O2, H2S, SO2, CH4, CO, CO2, and NH3.

[0015] Preferably, in S1, the pressure of the pressure swing adsorption column is 0.5-2.0 MPa.

[0016] Preferably, in S1, the pressure swing adsorption column comprises one or more of silica gel, activated carbon, activated alumina, carbon molecular sieve, molecular sieve, and modified molecular sieve.

[0017] Preferably, in S2, the catalytic adsorption column comprises one or more of a porous carrier-supported precious metal catalyst, a molecular sieve or an activated carbon-supported Cu catalyst.

[0018] More preferably, the porous carrier-supported noble metal catalyst has a catalytic deoxygenation depth of 0.01 ppm, and the molecular sieve or activated carbon-supported Cu catalyst has a catalytic carbon monoxide desorption depth of 0.05 ppm.

[0019] More preferably, the porous carrier-supported noble metal catalyst is selected from one or more of a TiO2-supported palladium catalyst or an Al2O3-supported palladium catalyst.

[0020] More preferably, the method for preparing the porous carrier-loaded precious metal catalyst comprises the following steps: impregnating the carrier with an equal volume of PdCl2 solution at room temperature, drying at 180-220°C, performing hydrogen reduction at 600°C for 1-2h and cooling to room temperature.

[0021] More preferably, the carrier comprises one or more of active Al2O3 balls with a diameter of 2-5 mm and TiO2 balls with a diameter of 2 mm and a length of 3-6 mm.

[0022] More preferably, the mass fraction of the PdCl2 solution is 0.01-0.05wt%.

[0023] More preferably, the preparation method of the molecular sieve or activated carbon supported Cu catalyst comprises the following steps: drying the activated carbon or 5A molecular sieve as a carrier for later use; dissolving Cu(NO3)2·3H2O and Ce(NO3)3·6H2O in water to obtain an impregnation solution; impregnating an equal volume of the carrier in the impregnation solution, drying at 105-150°C, and then calcining at 250-350°C in a N2 atmosphere for 2-6 hours.

[0024] More preferably, the molar ratio of Cu(NO3)2·3H2O and Ce(NO3)3·6H2O is (1-4):4.

[0025] Preferably, in the S2, the purity of the high-purity hydrogen is higher than 99.9995v%.

[0026] The beneficial effects of the present invention are:

[0027] The purity of the high-purity hydrogen obtained by the hydrogen purification method provided by the present invention through the pressure swing adsorption column and the catalytic adsorption column is higher than 99.9995v%. Among them, N2, O2, H2S, SO2, CH4, CO, CO2, and NH3 in the raw gas are adsorbed by the pressure swing adsorption column; O2 and CO are deeply desorbed by catalytic adsorption, which solves the problem of low hydrogen purity caused by the small capacity of weakly adsorbed impurity gases such as O2 and CO in hydrogen due to single pressure swing adsorption, and obtains high-purity hydrogen to meet the purity requirements of hydrogen for hydrogen fuel cells. At the same time, it is suitable for the occasion of using industrial by-product hydrogen to cool hydrogen generators and provide hydrogen for purification. When the raw gas passes through the pressure swing adsorption, most of the impurity gases are physically adsorbed by molecular sieves, activated carbon, etc., and a small amount of impurity gases are discharged with the hydrogen outlet to complete the initial purification of hydrogen; then the porous carrier-loaded precious metal catalyst, molecular sieve or activated carbon-loaded Cu catalyst is selected to deeply desorb O2 and CO in hydrogen to obtain high-purity hydrogen. When the pressure swing adsorption column is saturated with impurity gas, the air inlet of the pressure swing adsorption column is closed to keep the pressure swing adsorption column at room temperature, and purified high-purity hydrogen is introduced for gas replacement reaction to completely desorb impurity gas from activated carbon, molecular sieve, etc. in the pressure swing adsorption column and regenerate. When the catalytic adsorption column is saturated with CO, 150°C hydrogen is introduced, or heated vacuum regeneration is performed. A group of pressure swing adsorption columns and a group of catalytic adsorption columns are the minimum components that can achieve hydrogen purification, and can achieve intermittent purification of hydrogen; in order to achieve continuous purification of hydrogen, two or more groups of pressure swing adsorption columns and catalytic adsorption columns can be included. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart of the hydrogen purification method proposed in the present invention.

[0029] Explanation of the reference numerals: S1 - pressure swing adsorption column; S2 - catalytic adsorption column; V1, V2, V3, V4, V5, V6, V7 are all valves. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in detail through specific embodiments.

[0031] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0032] Example 1

[0033] A method for purifying hydrogen comprises the following steps:

[0034] S1, passing the raw gas into the pressure swing adsorption column through valve V1 to obtain preliminary purified gas;

[0035] S2, passing the preliminary purified gas into the catalytic adsorption column through valve V2, and releasing it through valve V3 to obtain high-purity hydrogen;

[0036] When the pressure swing adsorption column is saturated, stop introducing the raw gas into the pressure swing adsorption column, close the V1 valve, open the V5 valve and the V4 valve, and when the pressure of the pressure swing adsorption column is reduced to normal pressure, introduce high-purity hydrogen into the pressure swing adsorption column to regenerate it. After the regeneration is completed, return to S1 operation;

[0037] When the catalytic adsorption column is saturated with adsorption, stop introducing the preliminary purified gas into the catalytic adsorption column, close the V2 valve, and introduce 150°C high-purity hydrogen through the V6 valve and discharge it from the V7 valve, or evacuate the V6 valve to reactivate it for regeneration. After the regeneration is completed, return to S2 operation.

[0038] The pressure swing adsorption column includes: silica gel, alumina, activated carbon and molecular sieve; the activated carbon occupies 2 / 5 of the column height, and the molecular sieve occupies 3 / 5 of the column height;

[0039] The catalytic adsorption column comprises: Al2O3 loaded palladium catalyst and molecular sieve loaded Cu catalyst; wherein the Al2O3 loaded palladium catalyst occupies 50% of the column height, and the molecular sieve loaded Cu catalyst occupies 50% of the column height.

[0040] The preparation method of Al2O3 supported palladium catalyst includes the following steps: impregnating an active Al2O3 ball with a diameter of 3 mm with a 0.02wt% PdCl2 solution at room temperature, drying at 200°C, performing hydrogen reduction at 600°C for 1h, and cooling to room temperature. The preparation method of molecular sieve supported Cu catalyst includes the following steps: drying 5A molecular sieve as a carrier for standby use; dissolving Cu(NO3)2·3H2O and Ce(NO3)3·6H2O in water at a molar ratio of 1:4 to obtain an impregnation solution; impregnating an equal volume of the carrier in the impregnation solution, drying at 120°C, and then calcining at 300°C in a N2 atmosphere for 3h.

[0041] Table 1 Raw gas composition

[0042] gas <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[H2S]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> <![CDATA[H2]]> content 100ppm 100ppm 100ppm 50ppm 50ppm 100ppm Remain

[0043] Table 2 High purity hydrogen composition

[0044] gas <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[H2S]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> <![CDATA[H2]]> content 0.1ppm 0.01ppm 0.05ppm 0.05ppm 0.01ppm 0.05ppm Remain

[0045] It can be seen that the purity of the high-purity hydrogen obtained in Example 1 is 99.99998%.

[0046] Example 2

[0047] A method for purifying hydrogen comprises the following steps:

[0048] S1, passing the raw gas into the pressure swing adsorption column through valve V1 to obtain preliminary purified gas;

[0049] S2, passing the preliminary purified gas into the catalytic adsorption column through valve V2, and releasing it through valve V3 to obtain high-purity hydrogen;

[0050] When the pressure swing adsorption column is saturated, stop introducing the raw gas into the pressure swing adsorption column, close the V1 valve, open the V5 valve and the V4 valve, and when the pressure of the pressure swing adsorption column is reduced to normal pressure, introduce high-purity hydrogen into the pressure swing adsorption column to regenerate it. After the regeneration is completed, return to S1 operation;

[0051] When the catalytic adsorption column is saturated with adsorption, stop introducing the preliminary purified gas into the catalytic adsorption column, close the V2 valve, and introduce 150°C high-purity hydrogen through the V6 valve and discharge it from the V7 valve, or evacuate the V6 valve to reactivate it for regeneration. After the regeneration is completed, return to S2 operation.

[0052] The pressure swing adsorption column includes: activated carbon and molecular sieve; the activated carbon occupies 2 / 5 and the molecular sieve occupies 3 / 5 of the column height;

[0053] The catalytic adsorption column comprises: a molecular sieve loaded with a Cu catalyst of 100%.

[0054] The preparation method of molecular sieve-supported Cu catalyst comprises the following steps: drying 5A molecular sieve as a carrier for later use; dissolving Cu(NO3)2·3H2O and Ce(NO3)3·6H2O in water at a molar ratio of 1:4 to obtain an impregnation solution; impregnating an equal volume of the carrier in the impregnation solution, drying at 120°C, and then calcining at 300°C in a N2 atmosphere for 3 hours.

[0055] Table 3 Raw material hydrogen composition

[0056] gas <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> <![CDATA[H2]]> content 50ppm 10ppm 50ppm 100ppm 100ppm Remain

[0057] Table 4 High purity hydrogen composition

[0058] gas <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> <![CDATA[H2]]> content 0.1ppm 0.1ppm 0.05ppm 0.01ppm 0.05ppm Remain

[0059] It can be seen that the purity of the high-purity hydrogen obtained in Example 2 is 99.99997%.

[0060] It can be seen from the results of the above embodiments that the hydrogen purification method provided by the present invention can achieve a hydrogen purity of more than 99.9995v%, which meets the hydrogen purity requirements for hydrogen fuel cells and is also suitable for use in hydrogen purification occasions using industrial by-product hydrogen to cool hydrogen-cooled generators.

[0061] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for purifying hydrogen, characterized in that: The following steps are involved: S1. Pass the raw gas into a pressure swing adsorption column to obtain preliminary purified gas; S2, passing the preliminary purified gas into a catalytic adsorption column to obtain high-purity hydrogen; In the S2, the catalytic adsorption column comprises a porous carrier-loaded precious metal catalyst and a molecular sieve-loaded Cu catalyst; the porous carrier-loaded precious metal catalyst is an Al2O3-loaded palladium catalyst; The preparation method of molecular sieve-supported Cu catalyst comprises the following steps: drying 5A molecular sieve as a carrier for standby use; dissolving Cu(NO3)2·3H2O and Ce(NO3)3·6H2O in water to obtain an impregnation solution; impregnating an equal volume of the carrier in the impregnation solution, drying at 105-150°C, and then calcining at 250-350°C in a N2 atmosphere for 2-6 hours, wherein the molar ratio of Cu(NO3)2·3H2O to Ce(NO3)3·6H2O is 1:

4.

2. The method for purifying hydrogen according to claim 1, characterized in that: In the S1, the raw gas includes impurity gas and hydrogen; the impurity gas includes one or more of N2, O2, H2S, SO2, CH4, CO, CO2, and NH3; the pressure of the pressure swing adsorption column is 0.5-2.0 MPa.

3. The method for purifying hydrogen according to claim 1, characterized in that: In the above S1, when the pressure swing adsorption column is saturated with adsorption, the feed gas into the pressure swing adsorption column is stopped, and high-purity hydrogen is introduced into the pressure swing adsorption column to regenerate it. After the regeneration is completed, the feed gas is introduced into the pressure swing adsorption column again.

4. The method for purifying hydrogen according to claim 1, characterized in that: In the above S2, when the catalytic adsorption column is saturated with adsorption, the introduction of the preliminary purified gas into the catalytic adsorption column is stopped, and the catalytic adsorption column is regenerated. After the regeneration is completed, the preliminary purified gas is introduced into the catalytic adsorption column again.

5. The method for purifying hydrogen according to claim 1, characterized in that: In S1, the pressure swing adsorption column includes one or more of silica gel, activated carbon, activated alumina, and molecular sieve.

6. The method for purifying hydrogen according to claim 1, characterized in that: The porous carrier-supported noble metal catalyst has a catalytic deoxidation depth of 0.01 ppm, and the molecular sieve-supported Cu catalyst has a catalytic carbon monoxide desorption depth of 0.05 ppm.

7. The method for purifying hydrogen according to claim 1, characterized in that: In the S2, the purity of the high-purity hydrogen is higher than 99.9995v%.

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