Process for producing hydrogen by cracking methane through plasma reaction

Abstract

The invention provides a process for producing hydrogen by cracking methane through plasma reaction, which comprises a mixing system, a plasma ionization system, a hydrogen separation system and an acetylene recovery system, and is characterized in that the mixing system is used for mixing raw material gases containing methane, and the raw material gases are ionized by the plasma ionization system to form a mixed gas containing hydrogen and acetylene; after acetylene is separated by the acetylene recovery system, hydrogen is separated by the hydrogen separation system and is recycled to the mixing system; according to the overall scheme, the reaction efficiency of hydrogen production through methane conversion by plasmas is high, the needed temperature is low, the device size is small, and starting is fast; the methane is cracked by pulse spark discharge, and the methane has higher chemical activity and higher selectivity to hydrogen; the produced product is carbon black, so that the technological process is relatively simple, meanwhile, the carbon black can be recycled, and harmful emission is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of methane hydrogen production, and in particular to a plasma reaction methane cracking hydrogen production process. Background Art

[0002] As a highly efficient, clean and renewable energy source with great potential, hydrogen is gradually showing its irreplaceable advantages in many fields; its unique characteristics of high energy density, high combustion calorific value and near-perfect combustion efficiency make hydrogen occupy an important position in energy transformation and sustainable development strategies; the unique advantages of hydrogen are not only reflected in its high calorific value, but also in the fact that it produces almost no harmful substances during its use, and only releases water molecules as a by-product; the large-scale production characteristics of hydrogen energy provide a solid foundation for its widespread application.

[0003] Existing methane hydrogen production processes include: methane steam reforming hydrogen production, partial oxidation hydrogen production and autothermal reforming hydrogen production technologies. These technologies are energy-intensive and produce a large amount of CO gas during the hydrogen production process. Subsequent steps such as conversion reaction and removal of carbon dioxide are required to obtain high-purity hydrogen, which does not meet the needs of energy conservation and emission reduction.

[0004] At the same time, the actual conversion efficiency and selectivity of methane may be affected by many factors. At high temperatures, carbon deposits and other byproducts are easily formed on the catalyst surface, which may cause catalyst fouling and deactivation, not only reducing the service life of the catalyst, but also increasing the frequency and cost of catalyst replacement. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a plasma reaction methane cracking hydrogen production process to solve the problems of low hydrogen production efficiency and complicated process.

[0006] Based on the technical problems existing in the background technology, the present invention proposes a plasma reaction methane cracking hydrogen production process, including a mixing system, a plasma ionization system, a hydrogen separation system and an acetylene recovery system. The mixing system is used to mix the raw gas containing methane, which is ionized by the plasma ionization system to form a mixed gas containing hydrogen and acetylene. After the acetylene is separated by the acetylene recovery system, the hydrogen is separated by the hydrogen separation system and recycled to the mixing system.

[0007] Preferably, the mixing system includes a raw gas system for generating methane gas and a carrier gas system for generating nitrogen gas, and the raw gas system and the nitrogen system are connected to the same compressor for gas mixing.

[0008] Preferably, the plasma ionization system includes a heater, a plasma reactor, a cooling chamber, a cyclone separator and a bag dust collector. The first mixed gas generated by the compressor is heated by the heater in turn, and then ionized by the plasma reactor to generate a second mixed gas containing hydrogen and acetylene. The second mixed gas is cooled by the cooling chamber and then filtered by the cyclone separator and the bag dust collector to form a third mixed gas.

[0009] Preferably, the particles are carbon black, and carbon black is also produced during the plasma reaction.

[0010] Preferably, the plasma ionization system further comprises a carbon black collecting device, which can recover carbon black from the plasma reactor, the cooling chamber, the cyclone separator and the bag filter.

[0011] Preferably, the acetylene recovery system includes an acetylene absorption tower, a filter and an acetylene regeneration tower. The third mixed gas passes through the acetylene absorption tower to absorb acetylene to produce a fourth mixed gas and a rich liquid. The rich liquid passes through the filter to remove carbon black, and then passes through the acetylene regeneration tower to distill out acetylene and lean liquid. The lean liquid is circulated to the acetylene absorption tower to absorb new third mixed gas, and the fourth mixed gas enters the hydrogen separation system.

[0012] Preferably, heat exchange is achieved between the cooling chamber and the acetylene regeneration tower via a heat recovery device.

[0013] Preferably, the filter is connected to the carbon black collecting device via a dryer.

[0014] Preferably, the hydrogen separation system includes a third cooler, a second separator, a PSA adsorption tower, and a deliquidator. The fourth mixed gas is cooled by the third cooler and separated by the second separator, and then purified into hydrogen by the PSA adsorption tower, and then returned to the compressor for circulating mixing after dehydration.

[0015] Compared with the prior art, the plasma reaction methane cracking hydrogen production process proposed in the present invention adopts the above technical solution and achieves the following technical effects:

[0016] In the above overall scheme of the present invention, the plasma conversion of methane to hydrogen has high reaction efficiency, low required temperature, small device size and fast startup; pulsed spark discharge is used to crack methane, and methane has high chemical activity and higher selectivity for hydrogen; the product is carbon black, which makes the process relatively simple, and the carbon black can also be recycled to reduce harmful emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process principle relationship diagram of the present invention.

[0018] In the figure: 100, mixing system; 200, plasma ionization system; 300, hydrogen separation system; 400, acetylene recovery system; 1, raw gas system; 2, carrier gas system; 3, compressor; 4, heater; 5, plasma reactor; 6, cooling chamber; 7, cyclone separator; 8, bag filter; 9, carbon black collection device; 10, acetylene absorption tower; 11, filter; 12, acetylene regeneration tower; 13, second cooler; 19, heat recovery device; 18, dryer; 14, third cooler; 15, second separator; 16, PSA adsorption tower; 17, deliquidator. DETAILED DESCRIPTION

[0019] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0021] Example

[0022] Please refer to Figure 1The present invention proposes a plasma reaction methane cracking hydrogen production process, including a mixing system 100, a plasma ionization system 200, a hydrogen separation system 300 and an acetylene recovery system 400, wherein the mixing system 100 can mix high-purity methane gas and high-purity methane, and during this period, the gas discharged by the hydrogen separation system 300 is also added to mix to form a first mixed gas, the main components of which are methane and nitrogen. The first mixed gas can be cracked after ionization by the plasma ionization system 200 to form a second mixed gas, and the second mixed gas mainly contains hydrogen, acetylene, methane, pure carbon and nitrogen. The second mixed gas is filtered by the plasma ionization system 200 to form a third mixed gas, and the third mixed gas is then passed through the acetylene recovery system 400 to remove acetylene to form a fourth mixed gas, and the fourth mixed gas is then purified by the hydrogen separation system 300 to obtain hydrogen, and the remaining methane and nitrogen are returned to the mixing system 100 for circulation.

[0023] In a specific implementation manner, refer to Figure 1 The mixing system 100 includes a raw gas system 1 for producing methane gas and a carrier gas system 2 for producing nitrogen gas. The raw gas system 1 can provide methane gas with a high purity of 99.9%. The carrier gas system 2 can provide nitrogen gas with a high purity of 99.9%. The raw gas system 1 and the nitrogen system are connected to the same compressor 3 for gas mixing. The outlet pressure of the compressor 3 is 3 bar, which can ensure that the flow rate of the mixed gas received by the plasma ionization system 200 can reach a flow rate of 20L / s, ensuring that the plasma ionization system 200 operates normally. Furthermore, if the flow rate required by the plasma ionization system 200 is different, the flow rate provided by the compressor 3 can be different.

[0024] In a specific implementation manner, refer to Figure 1 The plasma ionization system 200 includes a heater 4, a plasma reactor 5, a cooling chamber 6, a cyclone separator 7 and a bag filter 8. The first mixed gas generated by the compressor 3 is heated by the heater 4 in turn. The first mixed gas needs to be preheated to 500 degrees, and then ionized by the plasma reactor 5 to generate a second mixed gas containing hydrogen and acetylene. The temperature in the plasma reactor 5 is 800 degrees. Therefore, the first mixed gas can increase the activity of the gas after preheating, and reduce the reaction time in the plasma reactor 5. The generated second mixed gas contains carbon black, carbon black and separated pure carbon. The carbon black is a particulate matter. After cooling in the cooling chamber 6, the temperature of the second mixed gas is reduced to 100 degrees to prevent a reverse reaction from occurring when filtering the carbon black. The carbon black is filtered by the cyclone separator 7 and the bag filter 8 to form a third mixed gas. The third mixed gas has the same composition as the second mixed gas, and the third mixed gas will contain a small amount of carbon black.

[0025] In a specific implementation manner, refer to Figure 1 The particles are carbon black, and carbon black will also be produced during the plasma reaction.

[0026] In a specific implementation manner, refer to Figure 1 The plasma ionization system 200 also includes a carbon black collecting device 9, which can recover carbon black from the plasma reactor 5, the cooling chamber 6, the cyclone separator 7 and the bag filter 8. Since carbon black is a particulate matter, it has a certain weight. After being separated by the cyclone separator 7, a large amount of carbon black can be cleaned out, and then finely removed by the bag filter, thereby achieving a large amount of carbon black removal.

[0027] In a specific implementation manner, refer to Figure 1 The acetylene recovery system 400 includes an acetylene absorption tower 10, a filter 11 and an acetylene regeneration tower 12. The third mixed gas passes through the acetylene absorption tower 10 to absorb acetylene to produce a fourth mixed gas and a rich liquid. The acetylene absorption tower 10 contains a methanol solution that can absorb acetylene. The methanol becomes a rich liquid after absorbing acetylene to saturation. The rich liquid passes through the filter 11 to remove carbon black. The carbon black at this time is precipitated, and then passes through the acetylene regeneration tower 12 to distill out acetylene and a lean liquid. The lean liquid is circulated to the acetylene absorption tower 10 to absorb acetylene in the new third mixed gas, and the fourth mixed gas enters the hydrogen separation system 300.

[0028] In a specific implementation manner, refer to Figure 1 The first cooler (cooling chamber 6) and the acetylene regeneration tower 12 realize heat exchange through the heat recovery device 19. A large amount of heat will be generated in the plasma reactor 5. The cooling chamber 6 needs to cool down the second mixed gas. The reaction in the acetylene regeneration tower 12 requires heat, which can be achieved through heat exchange. Heat balance can reduce energy consumption and improve reaction efficiency.

[0029] In a specific implementation manner, refer to Figure 1 The filter 11 is connected to the carbon black collecting device 9 through a dryer 18. The carbon black filtered by the filter 11 is separated from the rich liquid, so there will be liquid residue, which needs to be dried before use.

[0030] In a specific implementation manner, refer to Figure 1 The hydrogen separation system 300 includes a third cooler 14, a second separator 15, a PSA adsorption tower 16, and a deliquidator 17. The fourth mixed gas is cooled by the third cooler 14 and separated by the second separator 15, and then purified into hydrogen by the PSA adsorption tower 16. After dehydration, the fourth mixed gas is refluxed into the compressor 3 for circulating mixing.

[0031] In the above overall scheme, hydrogen is produced by methane cracking through plasma, so that the hydrogen atoms in methane can directly jump to the excited state at a lower temperature and undergo a dissociation reaction. During this period, a series of active substances and free radical fragments are produced, and after these substances collide effectively, stable compounds are produced. The product is related to the voltage and discharge type. When the voltage is higher and the temperature is lower, the methane molecules are decomposed more thoroughly, and the selectivity for the production of hydrogen and carbon black is greater, which makes the methane in this method have a higher atomic utilization rate.

[0032] In the above overall scheme, plasma conversion of methane to hydrogen has the advantages of high reaction efficiency, low required temperature, small device size, and fast startup. Pulsed spark discharge is used to crack methane, which has high chemical activity and higher selectivity for hydrogen. The product is carbon black instead of carbon monoxide, which makes the process relatively simple. At the same time, carbon black can also be recycled to reduce harmful emissions.

[0033] 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 process for producing hydrogen by cracking methane through plasma reaction, characterized in that: The invention comprises a mixing system (100), a plasma ionization system (200), a hydrogen separation system (300) and an acetylene recovery system (400). The mixing system (100) is used for mixing raw gas containing methane, ionizing it through the plasma ionization system (200) to form a mixed gas containing hydrogen and acetylene, separating acetylene through the acetylene recovery system (400), and then separating hydrogen through the hydrogen separation system (300), which is then recycled to the mixing system (100).

2. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 1, characterized in that: The mixing system (100) comprises a raw gas system (1) for producing methane gas and a carrier gas system (2) for producing nitrogen gas. The raw gas system (1) and the nitrogen system are connected to the same compressor (3) for gas mixing.

3. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 1, characterized in that: The plasma ionization system (200) comprises a heater (4), a plasma reactor (5), a cooling chamber (6), a cyclone separator (7) and a bag filter (8); the first mixed gas generated by the compressor (3) is sequentially heated by the heater (4), and then ionized by the plasma reactor (5) to generate a second mixed gas containing hydrogen and acetylene; the second mixed gas is cooled by the cooling chamber (6) and then filtered by the cyclone separator (7) and the bag filter (8) to form a third mixed gas.

4. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 3, characterized in that: The particles are carbon black, and carbon black is also produced during the plasma reaction.

5. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 3, characterized in that: The plasma ionization system (200) further comprises a carbon black collecting device (9), and the carbon black collecting device (9) can recover carbon black from the plasma reactor (5), the cooling chamber (6), the cyclone separator (7) and the bag filter (8).

6. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 5, characterized in that: The acetylene recovery system (400) comprises an acetylene absorption tower (10), a filter (11) and an acetylene regeneration tower (12); the third mixed gas passes through the acetylene absorption tower (10) to absorb acetylene to generate a fourth mixed gas and a rich liquid; the rich liquid passes through the filter (11) to remove carbon black; and then passes through the acetylene regeneration tower (12) to distill out acetylene and a lean liquid; the lean liquid passes through a second cooler (13) and is cooled and circulated to the acetylene absorption tower (10) to absorb new third mixed gas; and the fourth mixed gas enters the hydrogen separation system (300).

7. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 5, characterized in that: Heat exchange is achieved between the cooling chamber (6) and the acetylene regeneration tower (12) via a heat recovery device (19).

8. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 6, characterized in that: The filter (11) is connected to the carbon black collecting device (9) via a dryer (18).

9. The process for producing hydrogen from methane by cracking it through plasma reaction according to claim 6, characterized in that: The hydrogen separation system (300) comprises a third cooler (14), a second separator (15), a PSA adsorption tower (16), and a deliquidator (17). The fourth mixed gas is cooled by the third cooler (14), separated by the second separator (15), purified by the PSA adsorption tower (16), and then dehydrated and returned to the compressor (3) for circulation and mixing.

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