Process for producing hydrogen by coupling catalytic heating with methanol

Abstract

The invention belongs to the technical field of methanol hydrogen production, and discloses a process for catalytic heating coupling methanol hydrogen production. The process comprises the following steps: S1, providing a methanol cracking hydrogen production system; and S2, carrying out methanol steam reforming hydrogen production treatment based on a methanol cracking hydrogen production system. And S3, carrying out pressure swing adsorption treatment on the methanol decomposition gas prepared in S2 to obtain desorbed gas and purified hydrogen. S4, purified hydrogen flows through a product gas buffer tank with a filter element and then is fed into a gas using section. And S5, feeding the desorbed gas into a catalytic oxidation reactor for recovery treatment, and supplying released heat energy to a methanol cracking hydrogen production system for use. According to the invention, the organic combination of catalytic oxidation and methanol cracking hydrogen production is realized, the problems that the existing methanol hydrogen production process needs to discharge combustible tail gas and is unsafe and not environment-friendly are solved, extra fuel is not needed in the whole hydrogen production process, and only methanol needs to be provided; the method has the remarkable advantage of zero consumption of natural gas, diesel oil, coal and other fuels.

Description

Technical Field

[0001] The invention relates to the technical field of methanol hydrogen production, and in particular to a process for producing methanol hydrogen by catalytic heating coupling. Background Art

[0002] There are many methods for producing hydrogen, such as methanol, natural gas, water-gas conversion, ammonia decomposition, solvent fermentation, coking, electrolysis of salt and electrolysis of water. Currently, industrial hydrogen production mainly uses methanol, coal, natural gas and electrolysis of brine.

[0003] Natural gas hydrogen production is often used in large-scale hydrogen supply occasions. It consists of two parts: natural gas, steam reforming to produce reformed gas, and pressure swing adsorption to purify hydrogen. The technology is mature and the hydrogen production is large, but the system energy consumption and greenhouse gas release caused by the operation process of its hydrogen production reaction are large, and the environmental protection effect is low. Coal hydrogen production is a relatively traditional technology, which consists of four parts: coal, steam reforming to produce coal gas, coal gas purification, coal gas conversion, and pressure swing adsorption to purify hydrogen. It is often used in the gasification of synthetic ammonia or large-scale hydrogen supply occasions. It has the advantages of low cost, wide source, and suitable for large-scale production, but there are environmental problems such as serious pollution. Electrolytic hydrogen production passes direct current through platinum electrodes (or other inert materials) into water to obtain hydrogen with a purity of up to 99.5% to 99.8% at the cathode. Although the hydrogen produced by the above method is of high purity, low impurity content, sustainable, and low pollution, it has the problems of large investment, high comprehensive energy consumption, and high cost. The existing methanol hydrogen production process requires external heating to start, requires additional equipment, high energy consumption, large floor space, and requires the emission of combustible tail gas. Therefore, there is an urgent need to improve the hydrogen production process. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a process for producing hydrogen from methanol by coupling catalytic heating to organically combine catalytic oxidation and methanol cracking to produce hydrogen, save energy consumption, and achieve pollution-free emissions in the hydrogen production process.

[0005] A process for producing hydrogen from methanol by catalytic heating coupling, comprising the following steps:

[0006] S1 provides a methanol cracking hydrogen production system consisting of a methanol buffer tank, a desalted water buffer tank, a heat exchanger, a reformer, a vaporization superheater, a water cooler and a scrubber;

[0007] S2 is based on the methanol cracking hydrogen production system to carry out methanol steam reforming hydrogen production process;

[0008] S3 performs pressure swing adsorption treatment on the methanol decomposition gas obtained in S2 to obtain desorbed gas and purified hydrogen;

[0009] The hydrogen purified by S4 flows through the product gas buffer tank with a filter element and then is sent to the gas-using section;

[0010] The S5 desorbed gas is sent to a catalytic oxidation reactor for recovery and treatment, and the released heat energy is supplied to the methanol cracking hydrogen production system.

[0011] As a further improvement of the above scheme, a metering pump I is installed between the methanol buffer tank and the heat exchanger, and a metering pump II is installed between the desalted water buffer tank and the heat exchanger. In the present invention, methanol is fed into the heat exchanger through metering pump I, and unreacted methanol and water are fed into the heat exchanger through metering pump II.

[0012] As a further improvement of the above scheme, the method for producing hydrogen by methanol steam reforming is specifically operated as follows:

[0013] The methanol in the S21 methanol buffer tank, and the unreacted methanol and water recovered in the desalted water buffer tank, are sent to a heat exchanger to be mixed and heat exchanged with the reformed gas from the reformer;

[0014] S22 enters the vaporization superheater through the mixer after heat exchange and is heated by the heat transfer oil to obtain methanol water vapor;

[0015] S23 methanol water vapor enters the reformer and undergoes a reforming reaction through a methanol hydrogen production catalyst to obtain methanol decomposition gas;

[0016] S24 methanol decomposition gas returns to the heat exchanger for cooling;

[0017] The methanol decomposition gas after cooling in S25 is cooled by a water cooler and then enters a washing tower and is washed with desalted water to remove unreacted methanol.

[0018] As a further improvement of the above scheme, the inlet temperature of the reformer is 230-280°C, the inlet gauge pressure is 2.1 MPa, the outlet temperature is 235-285°C, and the outlet gauge pressure is 2.05 MPa.

[0019] As a further improvement of the above scheme, the methanol decomposition gas after cooling and washing is sent from the top of the washing tower to the pressure swing adsorption process, and the methanol and water removed by washing with desalted water enter the desalted water buffer tank for recycling.

[0020] As a further improvement of the above scheme, the pressure swing adsorption treatment is carried out in a pressure swing adsorption system, and the pressure swing adsorption system is composed of a plurality of adsorbers arranged in parallel, each of which is filled with an adsorbent. In the present invention, after the methanol decomposition gas enters the adsorber, impurities such as CO2, CO, CH4, H2O, etc. in the decomposition gas are adsorbed by the adsorbent, thereby achieving the purpose of purifying hydrogen.

[0021] As a further improvement of the above solution, the adsorbent is a solid material with a developed microporous structure, and the adsorbent is at least two of activated alumina, activated carbon, silica gel or molecular sieve.

[0022] As a further improvement of the above scheme, during the pressure swing adsorption treatment process, several adsorbers are selectively operated. In the present invention, when one adsorber is working, the other adsorbers are in a pressure reduction regeneration state, and each adsorber is switched regularly. For example, when the adsorption capacity of the adsorbent of the working adsorber reaches the set value, the currently working adsorber is depressurized and enters the regeneration state. At the same time, the regenerated adsorber is pressurized to the working pressure and then enters the adsorption state. By alternating adsorption and regeneration, high-quality treatment of the continuously input methanol decomposition gas is achieved, and the purpose of continuously outputting product hydrogen is achieved.

[0023] As a further improvement of the above scheme, the pressure swing adsorption treatment includes an adsorption stage and a pressure reduction analysis stage, the desorbed gas is obtained after the pressure reduction analysis stage, and the purified hydrogen is obtained after the adsorption stage. The present invention uses pressure swing adsorption technology to purify the methanol decomposition gas generated by methanol steam reforming hydrogen production to obtain higher purity hydrogen. The purity of the hydrogen obtained after pressure swing adsorption can reach 99.9995%, and the impurities adsorbed in the adsorbent are automatically desorbed under low pressure conditions. At this time, the originally adsorbed impurities exist in the form of desorbed gas, and the adsorbent is regenerated to facilitate the next adsorption treatment.

[0024] As a further improvement of the above solution, when hydrogen flows through a product gas buffer tank with a filter element, particles with a particle size greater than 0.3 μm are filtered out.

[0025] As a further improvement of the above scheme, a heat exchanger and a circulating fan are installed in the catalytic oxidation reactor, and a catalytic oxidation catalyst is arranged in the catalytic oxidation reactor. In the present invention, CO and CH4 in the desorbed gas are catalytically oxidized on the surface of the catalytic oxidation catalyst and converted into CO2 and H2O, which has the characteristics of sufficient reaction, no secondary pollution and safe operation. By arranging the circulating fan, the oxygen content in the catalytic oxidation reactor is always controlled below 8%.

[0026] As a further improvement of the above scheme, the catalytic oxidation catalyst is activated at low temperature, and the desorbed gas enters the catalytic oxidation reactor to undergo a redox reaction, releasing a large amount of low-level heat, and the desorbed waste gas is converted into thermal energy. The low-level thermal energy remaining in the flue gas is transferred to the heat transfer oil through the heat exchanger, and the heated heat transfer oil is sent to the reformer and the vaporization superheater through a circulation pump to release heat for methanol cracking, and the cooled heat transfer oil is returned to the catalytic oxidation reactor for recycling. In the present invention, the catalytic oxidation reactor can realize the oxidation treatment of organic matter without an external heat source, the operating temperature is low, it is a flameless reaction, and there is no open flame in the reactor. Therefore, there is no need to set up a safety distance with the methanol cracking hydrogen production system, the equipment is safe and reliable, and the safety risks caused by electric heating at startup can be completely eliminated.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention realizes pollution-free emission of hydrogen production process by recovering and treating desorbed gas released during pressure swing adsorption, thus overcoming the problem that the existing methanol hydrogen production process needs to discharge combustible tail gas, which is unsafe and environmentally unfriendly. In addition, desorbed waste gas released during pressure swing adsorption is recovered and treated by catalytic oxidation at room temperature, so that the waste gas is converted into heat energy to provide heat for methanol cracking hydrogen production reaction, thus saving energy consumption and realizing the organic combination of catalytic oxidation and methanol cracking hydrogen production.

[0029] The present invention does not require additional fuel during the entire hydrogen production process, and only methanol is required. Compared with traditional thermal oil furnaces, it has the significant advantage of zero consumption of fuels such as natural gas, diesel and coal.

[0030] The process of the present invention combines methanol cracking and pressure swing adsorption to produce hydrogen, and the process production technology is mature, the operation is safe and reliable, the degree of automation is high, and it is convenient for industrial operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Shown is a module block diagram of a methanol cracking hydrogen production system in a process of catalytic heating coupled methanol to hydrogen production provided by the present invention.

[0032] Figure 2 Shown is a hydrogen production flow chart of a process for producing hydrogen from methanol by catalytic heating coupled with methanol provided by the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Additional aspects and advantages of the present invention will be given in part in the following description, and will become apparent from the following description, or will be understood through the practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not intended to limit the present invention.

[0034] As used herein, the terms "comprises," "including," "contains," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0035] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range limited by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including a range of "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When a numerical range is described in this article, unless otherwise specified, the range is intended to include its end values ​​and all integers and fractions within the range.

[0036] The specific embodiments of the present invention are described in detail below.

[0037] This embodiment provides a process for producing hydrogen from methanol by catalytic heating coupling, characterized in that it includes the following steps:

[0038] S1 provides Figure 1 As shown, a methanol cracking hydrogen production system consisting of a methanol buffer tank, a desalted water buffer tank, a heat exchanger, a reformer, a vaporization superheater, a water cooler and a scrubber;

[0039] A metering pump I is installed between the methanol buffer tank and the heat exchanger, and a metering pump II is installed between the desalted water buffer tank and the heat exchanger. In the present invention, methanol is fed into the heat exchanger through the metering pump I, and unreacted methanol and water are fed into the heat exchanger through the metering pump II.

[0040] S2 is based on the methanol cracking hydrogen production system to carry out methanol steam reforming hydrogen production processing.

[0041] Please refer to Figure 2 The method for producing hydrogen through methanol steam reforming is specifically performed as follows:

[0042] The methanol in the S21 methanol buffer tank is mixed with the unreacted methanol and water recovered in the desalted water buffer tank and sent to the heat exchanger for heat exchange with the reformed gas from the reformer.

[0043] S22 enters the vaporization superheater through the mixer after heat exchange and is heated by the heat transfer oil to obtain methanol water vapor.

[0044] S23 methanol water vapor enters the reformer, passes through the methanol hydrogen production catalyst, undergoes a reforming reaction, and obtains methanol decomposition gas. The inlet temperature of the reformer is 230-280°C, the inlet gauge pressure is 2.1MPa, the outlet temperature is 235-285°C, and the outlet gauge pressure is 2.05MPa.

[0045] The mixture of methanol and water vapor undergoes dual reactions of CH3OH cracking and CO conversion in the reformer to generate H2 and CO2. The reaction equation is as follows:

[0046] The reaction process of methanol cracking is CH3OH=CO+2H2-90.7kJ / mol

[0047] The reaction process of CO conversion is CO+H2O=CO2+H2+41.2kJ / mol

[0048] The total reaction is CH3OH+H2O=CO2+3H2-49.5kJ / mol

[0049] In summary, methanol cracking to produce hydrogen is an endothermic process. The heat required for the reaction in this embodiment is provided by the circulation of circulating heat transfer oil, and the heating of the raw liquid, vaporization superheating, and the heat of the reaction all come from the heat generated by the catalytic oxidation of the desorbed gas.

[0050] S24 The methanol decomposition gas returns to the heat exchanger for cooling. In this embodiment, the methanol decomposition gas, i.e., hydrogen-rich gas, has a relatively high temperature. When the methanol decomposition gas returns to the heat exchanger, it exchanges heat with the raw material liquid (methanol + unreacted methanol and water) and is cooled.

[0051] S25 The cooled methanol decomposition gas is cooled by a water cooler and then enters a washing tower to be washed with desalted water to remove unreacted methanol. In this embodiment, the cooled and washed methanol decomposition gas is sent from the top of the washing tower to the pressure swing adsorption process, and the methanol and water removed by washing with desalted water enter the desalted water buffer tank for recycling.

[0052] S3 performs pressure swing adsorption treatment on the methanol decomposition gas obtained in S2 to obtain desorbed gas and purified hydrogen;

[0053] The pressure swing adsorption treatment is carried out in a pressure swing adsorption system, and the pressure swing adsorption system is composed of a number of adsorbers arranged in parallel; each adsorber is filled with an adsorbent, and after the methanol decomposition gas enters the adsorber, impurities such as CO2, CO, CH4, H2O, etc. in the decomposition gas are adsorbed by the adsorbent, thereby achieving the purpose of purifying hydrogen. The adsorbent is a solid material with a developed microporous structure, and the adsorbent is at least two of activated alumina, activated carbon, silica gel or molecular sieve.

[0054] During the pressure swing adsorption treatment process, several adsorbers are selected to operate. In this embodiment, when one adsorber is working, the other adsorbers are in a pressure-reducing regeneration state, and each adsorber is switched regularly. For example, when the adsorption capacity of the adsorbent of the working adsorber reaches the set value, the currently working adsorber is depressurized and enters the regeneration state. At the same time, the regenerated adsorber is pressurized to the working pressure and then enters the adsorption state. By alternating adsorption and regeneration, high-quality treatment of the continuously input methanol decomposition gas is achieved, and the purpose of continuously outputting product hydrogen is achieved.

[0055] The pressure swing adsorption treatment includes an adsorption stage and a pressure reduction and analysis stage. The desorbed gas is obtained after the pressure reduction and analysis stage, and the purified hydrogen is obtained after the adsorption stage. Based on the characteristics that the adsorbent has a greater adsorption capacity for gas under high pressure and a smaller adsorption capacity under low pressure, and the adsorbent has a smaller adsorption capacity for the ideal component H2 regardless of high pressure or low pressure, this embodiment uses pressure swing adsorption technology to purify the methanol decomposition gas generated by methanol steam reforming hydrogen production treatment to obtain higher purity hydrogen. The purity of the hydrogen obtained after pressure swing adsorption can reach 99.9995%, and the impurities adsorbed in the adsorbent are automatically desorbed under low pressure conditions. At this time, the originally adsorbed impurities exist in the form of desorbed gas, and the adsorbent is regenerated to facilitate the next adsorption treatment.

[0056] The hydrogen purified by S4 flows through the product gas buffer tank with a filter element, and then is sent to the gas using section. In this embodiment, when the hydrogen flows through the product gas buffer tank with a filter element, particles with a particle size greater than 0.3 μm are filtered out.

[0057] The S5 desorbed gas is sent to a catalytic oxidation reactor for recovery and treatment, and the released heat energy is supplied to the methanol cracking hydrogen production system.

[0058] The catalytic oxidation reactor is equipped with a heat exchanger and a circulating fan, and a catalytic oxidation catalyst is arranged in the catalytic oxidation reactor. This embodiment is explained by taking the SCST-901 catalytic oxidation catalyst as an example. CO and CH4 in the desorbed gas are catalytically oxidized on the surface of the SCST-901 catalytic oxidation catalyst and converted into CO2 and H2O. It has the characteristics of full reaction, no secondary pollution, and safe operation. In other embodiments, the SCST-902 catalytic oxidation catalyst can also be used, which will not be described here. In the present invention, a circulating fan is arranged so that the oxygen content in the catalytic oxidation reactor is always controlled below 8%.

[0059] The catalytic oxidation catalyst is activated at low temperature, and the desorbed gas enters the catalytic oxidation reactor to undergo a redox reaction, releasing a large amount of low-level heat, and the desorbed waste gas is converted into thermal energy. The low-level thermal energy remaining in the flue gas is transferred to the heat transfer oil through the heat exchanger. The heated heat transfer oil is sent to the reformer and vaporization superheater through a circulation pump, releasing heat for methanol cracking, and the cooled heat transfer oil returns to the catalytic oxidation reactor for recycling. In this embodiment, the catalytic oxidation reactor can realize the oxidation treatment of organic matter without the need for an external heat source, the operating temperature is low, it is a flameless reaction, and there is no open flame in the reactor. Therefore, there is no need to set up a safety distance with the methanol cracking hydrogen production system. The equipment is safe and reliable, and the safety risks caused by electric heating at startup can be completely eliminated.

[0060] In this embodiment, the desorbed gas is sent to a catalytic oxidation reactor for recovery and treatment, and the desorbed waste gas is converted into thermal energy, thereby achieving pollution-free emissions in the hydrogen production process and providing heat for the methanol cracking hydrogen production reaction without adding additional external heating measures, thereby saving the operating cost of the boiler.

[0061] In summary, the methanol hydrogen production process of this embodiment has the following advantages: by recovering and treating the desorbed gas released during pressure swing adsorption, pollution-free emission of the hydrogen production process is achieved, overcoming the problem that the existing methanol hydrogen production process needs to emit flammable tail gas, which is unsafe and environmentally friendly, and by recovering and treating the desorbed waste gas released during pressure swing adsorption through room temperature catalytic oxidation, the waste gas is converted into thermal energy to provide heat for the methanol cracking hydrogen production reaction, saving energy consumption, and realizing the organic combination of catalytic oxidation and methanol cracking hydrogen production.

[0062] The whole process of hydrogen production does not require additional fuel, only methanol is needed. Compared with traditional thermal oil furnaces, it has the significant advantage of zero consumption of fuels such as natural gas, diesel and coal. The production of hydrogen by combining methanol cracking and pressure swing adsorption has mature process production technology, safe and reliable operation, high degree of automation, and is easy for industrial operation.

[0063] The above embodiments are merely preferred implementations of the present invention. Any simple modification, amendment and substitution of the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A process for producing hydrogen from methanol by catalytic heating coupling, characterized in that: The following steps are involved: S1 provides a methanol cracking hydrogen production system consisting of a methanol buffer tank, a desalted water buffer tank, a heat exchanger, a reformer, a vaporization superheater, a water cooler and a scrubber; S2 is based on the methanol cracking hydrogen production system to carry out methanol steam reforming hydrogen production process; S3 performs pressure swing adsorption treatment on the methanol decomposition gas obtained in S2 to obtain desorbed gas and purified hydrogen; The hydrogen purified by S4 flows through the product gas buffer tank with a filter element and then is sent to the gas-using section; The S5 desorbed gas is sent to a catalytic oxidation reactor for recovery and treatment, and the released heat energy is supplied to the methanol cracking hydrogen production system.

2. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 1, characterized in that: A metering pump I is installed between the methanol buffer tank and the heat exchanger, and a metering pump II is installed between the desalted water buffer tank and the heat exchanger.

3. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 2, characterized in that: The method for producing hydrogen through methanol steam reforming is specifically performed as follows: The methanol in the S21 methanol buffer tank, and the unreacted methanol and water recovered in the desalted water buffer tank, are sent to a heat exchanger to be mixed and heat exchanged with the reformed gas from the reformer; S22 enters the vaporization superheater through the mixer after heat exchange and is heated by the heat transfer oil to obtain methanol water vapor; S23 methanol water vapor enters the reformer and undergoes a reforming reaction through a methanol hydrogen production catalyst to obtain methanol decomposition gas; S24 methanol decomposition gas returns to the heat exchanger for cooling; The methanol decomposition gas after cooling in S25 is cooled by a water cooler and then enters a washing tower and is washed with desalted water to remove unreacted methanol.

4. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 3 is characterized in that: The inlet temperature of the reformer is 230-280° C., the inlet gauge pressure is 2.1 MPa, the outlet temperature is 235-285° C., and the outlet gauge pressure is 2.05 MPa.

5. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 4, characterized in that: The methanol decomposition gas after cooling and washing is sent from the top of the washing tower to the pressure swing adsorption process, and the methanol and water removed by washing with desalted water enter the desalted water buffer tank for recycling.

6. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 1, characterized in that: The pressure swing adsorption treatment is carried out in a pressure swing adsorption system, and the pressure swing adsorption system is composed of a plurality of adsorbers arranged in parallel, each of which is filled with an adsorbent.

7. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 6, characterized in that: The adsorbent is a solid material with a developed microporous structure, and the adsorbent is at least two of activated alumina, activated carbon, silica gel or molecular sieve; During the pressure swing adsorption process, one of several adsorbers is selected for operation; The pressure swing adsorption process includes an adsorption stage and a pressure reduction and decomposition stage; the desorbed gas is obtained after the pressure reduction and decomposition stage, and the purified hydrogen is obtained after the adsorption stage.

8. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 1, characterized in that: When hydrogen flows through the product gas buffer tank with a filter element, particles with a particle size greater than 0.3μm are filtered out.

9. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 1, characterized in that: The catalytic oxidation reactor is equipped with a heat exchanger and a circulating fan, and a catalytic oxidation catalyst is arranged in the catalytic oxidation reactor.

10. The process for producing hydrogen from methanol by catalytic heating coupling according to claim 9, characterized in that The catalytic oxidation catalyst is activated at low temperature, and the desorbed gas enters the catalytic oxidation reactor to undergo redox reaction, releasing a large amount of low-level heat, and the exhaust gas is converted into thermal energy. The residual low-level thermal energy in the flue gas is transferred to the heat transfer oil through the heat exchanger. The heated heat transfer oil is sent to the reformer and vaporization superheater through a circulation pump, releasing heat for methanol cracking, and the cooled heat transfer oil returns to the catalytic oxidation reactor for recycling.

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