Efficient large-scale coupling hydrogen production process and system

Abstract

The invention relates to a high-efficiency large-scale coupling hydrogen production process and system, an alkaline water electrolysis hydrogen production system, an ammonia water distillation system, an ammonia decomposition system and a hydrogen separation and collection system are coupled, alkaline liquor in the alkaline water electrolysis hydrogen production system is not recycled in an electrolysis system but is directly sent to the ammonia water distillation system, a reactive distillation mode is adopted, and the hydrogen separation and collection system is directly sent to the ammonia decomposition system. The method comprises the following steps of: reacting alkali liquor with fixed ammonium in ammonia water to generate volatile ammonia, carrying out step-by-step steam stripping condensation, sending enriched ammonia-containing non-condensable gas to an ammonia decomposition system for catalytic decomposition to obtain hydrogen-containing process gas, separating and purifying to obtain hydrogen, and finally collecting the hydrogen and hydrogen prepared by water electrolysis to serve as a product hydrogen to be sent to downstream users. Compared with the traditional water electrolysis process for recycling the alkali liquor, the method has the advantages that the influence of impurity ion accumulation and insoluble small particles on the quality of the electrolyte after the alkali liquor is recycled is avoided, the conductivity of the electrolyte is improved, the electrolysis power consumption is reduced, the electrolysis hydrogen production efficiency is improved, and the electrolysis hydrogen production yield is increased.

Description

Technical Field

[0001] The present invention relates to the field of coking technology, and in particular to an efficient and large-scale coupled hydrogen production process and system. Background Art

[0002] "Hydrogen metallurgy" and "steel and chemical co-production" are effective ways to "reduce carbon" in the steel and coking industries, and their core resources are the large-scale supply of low-cost hydrogen. At present, industrial-scale hydrogen can be derived from natural gas, coal, water and industrial by-product gas through technical means such as production or separation. Among them, hydrogen production by water electrolysis has the advantages of high hydrogen purity and few impurities. If hydrogen production by water electrolysis is coupled with renewable energy, "zero carbon" emissions in the hydrogen production process can be achieved, which has unique technical advantages. In the future, combining renewable energy with water electrolysis technology to produce "green hydrogen" will be an important way to obtain hydrogen, and it is also an ideal model for achieving large-scale consumption of renewable energy such as wind and light and rapid transformation of traditional energy.

[0003] There are three main technical routes for hydrogen production by water electrolysis: alkaline water electrolysis, proton exchange membrane water electrolysis and solid oxide water electrolysis. At present, only alkaline water electrolysis technology has been widely used in commercial applications, which is mainly related to its mature development, low investment cost and good durability. However, this technology still has disadvantages such as low hydrogen production efficiency, large equipment size and high maintenance cost.

[0004] Because the conductivity of pure water is very small (1-10 μS cm), only after adding a certain amount of electrolyte, it is conducive to the occurrence of water electrolysis reaction. Therefore, for alkaline water electrolysis technology, a certain concentration of sodium hydroxide or potassium hydroxide solution is a more ideal electrolyte. In theory, the alkaline water electrolysis process only consumes water, and the alkali only plays a conductive role. However, due to gas entrainment, filter cleaning, and leakage of the pipeline system, the lost alkali must still be frequently replenished to the system during actual operation. However, the impurity ions and insoluble small particles accumulated in the repeated circulation of alkaline electrolytes, especially the carbonates formed by absorbing carbon dioxide in the air, will gradually reduce their conductivity. When the impurity concentration accumulates to a certain extent (such as the carbonate concentration rises to 1 mg / L), it will cause the electrolysis current to decrease, the unit power consumption to increase, and the electrolysis performance and efficiency to seriously deteriorate, so that the system has to be shut down to replace the electrolyte, which not only affects the normal operation of the system, but also brings a certain risk of leakage. Therefore, controlling the quality of the electrolyte is extremely important for alkaline water electrolysis technology.

[0005] The Chinese patent application with publication number CN116905007A discloses "an alkaline water electrolysis hydrogen production system and a water electrolysis hydrogen production method". The system includes an electrolytic cell, a gas-liquid separation device, and an additional ion purification device and a solid impurity filter. The electrolyte can be purified during electrolysis, avoiding periodic replacement of the electrolyte and reducing the number of electrolytic cell shutdowns. However, it also increases the investment cost of the electrolysis system and increases the complexity of operation.

[0006] The Chinese invention patent with authorization announcement number CN116768430B discloses "a method and system for treating alkaline electrolyte", the Chinese utility model patent with authorization announcement number CN220633198U discloses "a recovery device for auxiliary impurity removal", and the Chinese utility model patent with authorization announcement number CN210215013U discloses "an alkaline electrolyte purification and recovery device". All of them use alkaline electrolyte purification equipment independent of the electrolysis system. This offline purification equipment has no connection with the electrolysis system. Only after all the electrolyte is replaced can "out-of-system" purification be carried out, which not only increases equipment investment, but also increases the difficulty of operation and brings certain environmental risks. Summary of the invention

[0007] The present invention provides an efficient and large-scale coupled hydrogen production process and system. Different from the traditional water electrolysis process in which alkali solution is recycled, the alkali solution in the present invention is not recycled in the electrolysis system after participating in water electrolysis, but is directly sent to an ammonia distillation system, and a reactive distillation method is adopted to make the alkali solution react with the fixed ammonium in the ammonia solution to generate volatile ammonia, which is enriched by step-by-step stripping, and after ammonia-containing non-condensable gas is obtained at the top of a distillation tower, it is sent to an ammonia decomposition system for further catalytic decomposition into hydrogen-containing process gas, and further separated and purified to obtain hydrogen, which is then collected with the hydrogen obtained by water electrolysis and sent to downstream users as product hydrogen.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An efficient and large-scale coupled hydrogen production process couples an alkaline water electrolysis hydrogen production system, an ammonia distillation system, an ammonia decomposition system and a hydrogen separation and collection system. The alkali liquid in the alkaline water electrolysis hydrogen production system is not recycled in the electrolysis system, but is directly sent to the ammonia distillation system. Reactive distillation is used to react the alkali liquid with the fixed ammonium in the ammonia water to generate volatile ammonia. After step-by-step stripping and condensation, the enriched ammonia-containing non-condensable gas is sent to the ammonia decomposition system for catalytic decomposition into hydrogen-containing process gas. Hydrogen is obtained through separation and purification, and finally collected with the hydrogen produced by water electrolysis and sent to downstream users as product hydrogen.

[0010] Furthermore, an efficient and large-scale coupled hydrogen production process specifically includes the following steps:

[0011] 1) In the alkaline water electrolysis hydrogen production system, the alkaline electrolyte after participating in the water electrolysis reaction in the alkaline electrolytic cell is directly sent to the ammonia distillation system after gas-liquid separation; the high-purity hydrogen obtained after gas-liquid separation, mist capture and purification of the hydrogen-containing electrolyte is sent to the hydrogen separation and collection system, and the oxygen obtained after gas-liquid separation, mist capture and purification of the oxygen-containing electrolyte is sent to downstream oxygen users;

[0012] 2) In the ammonia distillation system, the alkali solution from the alkaline water electrolysis hydrogen production system reacts with the heat exchange ammonia water in the distillation tower, and the generated ammonia vapor is condensed by step-by-step stripping, and the obtained ammonia-containing non-condensable gas is sent to the ammonia decomposition system;

[0013] 3) In the ammonia decomposition system, the ammonia-containing non-condensable gas is catalytically decomposed into hydrogen-containing process gas;

[0014] 4) In the hydrogen separation and collection system, the hydrogen in the hydrogen-containing process gas is separated and purified, and the obtained hydrogen is collected with the hydrogen sent out by the alkaline water electrolysis hydrogen production system and sent to downstream hydrogen users as product hydrogen.

[0015] Furthermore, in the step 1), the alkali solution is a strong alkali solution including potassium hydroxide and sodium hydroxide, and the concentration of the alkali solution is 2%wt to 40%wt.

[0016] Furthermore, in the step 3), a ruthenium-based or nickel-based catalyst is used to catalytically decompose the ammonia-containing non-condensable gas, and the reaction is carried out at 600-850° C. The required heat is provided by gas combustion or high-temperature steam; the waste heat of the hydrogen-containing process gas after the reaction is recovered through a waste heat recovery device.

[0017] Furthermore, in step 4), the method of separating and purifying the hydrogen-containing process gas includes temperature swing adsorption or pressure swing adsorption; the adsorbent includes molecular sieve or activated carbon.

[0018] The invention discloses an efficient and large-scale coupled hydrogen production system, comprising an alkaline water electrolysis hydrogen production system, an ammonia distillation system, an ammonia decomposition system and a hydrogen separation and collection system; the alkaline electrolyzer in the alkaline water electrolysis hydrogen production system is connected to an ammonia distillation tower in the ammonia distillation system through an alkaline liquid delivery pipeline, and a gas-liquid separator is arranged on the alkaline liquid delivery pipeline to separate hydrogen and oxygen; the hydrogen outlet of the gas-liquid separator is connected to a mixer upstream of a product hydrogen pipeline through a hydrogen pipeline; the ammonia distillation system is connected to an ammonia decomposition reactor in the ammonia decomposition system through an ammonia-containing non-condensable steam pipeline; the ammonia decomposition system is connected to the hydrogen separation and collection system through a hydrogen-containing process gas pipeline; the hydrogen separation and collection system comprises a compressor, a final cooler, an adsorption tower and a mixer connected in sequence, and the hydrogen outlet pipeline at the top of the adsorption tower is connected to the product hydrogen pipeline through a mixer.

[0019] Furthermore, the alkali liquid delivery pipeline includes a hydrogen-containing electrolyte pipeline, an oxygen-containing electrolyte pipeline, an alkali liquid pipeline 1 and an alkali liquid pipeline 2; the gas-liquid separator includes a hydrogen-alkali separator and an oxygen-alkali separator; the alkaline electrolyzer is connected to the hydrogen-alkali separator through the hydrogen-containing electrolyte pipeline, and the alkali liquid outlet of the hydrogen-alkali separator is connected to the alkali liquid pipeline 1; the hydrogen outlet of the hydrogen-alkali separator is connected to the hydrogen pipeline, and a hydrogen condenser, a hydrogen mist collector and a hydrogen purifier are sequentially arranged on the hydrogen pipeline along the flow direction of hydrogen; the alkaline electrolyzer is connected to the oxygen-alkali separator through the oxygen-containing electrolyte pipeline, and the alkali liquid outlet of the oxygen-alkali separator is connected to the alkali liquid pipeline 2; the oxygen outlet of the oxygen-alkali separator is connected to the oxygen pipeline, and an oxygen condenser, an oxygen mist collector and an oxygen purifier are sequentially arranged on the oxygen pipeline along the flow direction of oxygen; the alkali liquid pipeline 1 is connected to the alkali liquid inlet of the ammonia distillation tower after merging with the alkali liquid pipeline 2.

[0020] Furthermore, the ammonia vapor outlet at the top of the ammonia distillation tower is connected to the tower top condenser through an ammonia vapor pipeline, and the ammonia-containing non-condensable gas outlet of the top condenser is connected to the ammonia decomposition reactor through an ammonia-containing non-condensable gas pipeline; the condensate of the top condenser is connected to the reflux liquid inlet at the top of the ammonia distillation tower through a reflux condensate pipeline; an ammonia inlet is arranged at the top of the ammonia distillation tower, a heat source inlet is arranged at the bottom to be connected to the tower bottom reboiler, and an ammonia wastewater outlet is arranged at the bottom.

[0021] Furthermore, the ammonia decomposition system is composed of an ammonia decomposition reactor, a heater, a waste heat boiler and a process gas cooler; a heater is provided at one end of the ammonia decomposition reactor close to the inlet of the ammonia-containing non-condensable gas, and the hydrogen-containing process gas outlet of the ammonia decomposition reactor is connected to the hydrogen separation and collection system through a hydrogen-containing process gas pipeline; a waste heat boiler is provided on the hydrogen-containing process gas pipeline close to the ammonia decomposition reactor, and a process gas cooler is provided on the hydrogen-containing process gas pipeline downstream of the waste heat boiler.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) Compared with the traditional alkaline water electrolysis process in which alkali solution is recycled, the process of the present invention avoids the accumulation of impurity ions and the influence of insoluble small particles on the quality of the electrolyte after repeated recycling of the alkali solution, improves the conductivity of the electrolyte, reduces the power consumption of electrolysis, improves the efficiency of electrolytic hydrogen production, and increases the output of electrolytic hydrogen production;

[0024] 2) The process of the present invention is combined with the existing coke oven gas purification or wastewater treatment process, and the alkali solution after electrolysis is used as one of the raw materials for ammonia distillation. The fixed ammonium in the ammonia water is deeply decomposed by the reactive distillation method, and the obtained ammonia vapor is further decomposed, separated and purified to obtain hydrogen, thereby achieving increased hydrogen production;

[0025] 3) The process of the present invention is a hydrogen production process with dual hydrogen production capabilities, that is, it includes an electrolytic hydrogen production process and an ammonia decomposition hydrogen production process, which not only greatly increases the total hydrogen production, but also is an efficient coupled hydrogen production process route that can be implemented on a large scale;

[0026] 4) After adopting the process of the present invention, the alkali liquid circulation pump, alkali liquid filter, alkali liquid cooler required for the existing alkaline water electrolysis process, and the alkali liquid pump, alkali liquid preheater and alkali liquid tank and other equipment of the existing ammonia distillation process are omitted; after practical application, the total investment cost, operation complexity and energy consumption of the coupling of the two processes are greatly reduced;

[0027] 5) In the process of the present invention, no circulating alkaline solution is used during electrolysis, so there is no environmental risk of leakage and discharge of alkaline electrolyte;

[0028] 6) When the process described in the present invention adopts "green electricity", it can be used to produce "green hydrogen".

[0029] 7) The process described in the present invention not only involves the production of coking chemicals in the steel coking industry, but also involves the technical fields of coal chemical industry, petrochemical industry, environmental protection and low-carbon production, and is an efficient and large-scale coupling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart (system composition diagram) of an efficient and large-scale coupled hydrogen production process described in the present invention.

[0031] In the figure: 1. Alkaline water electrolysis hydrogen production system 2. Ammonia distillation system 3. Ammonia decomposition system 4. Hydrogen separation and collection system 10. Alkaline electrolyzer 11. Water tank 12. Alkali preparation tank 13. Power supply 14-1. Hydrogen alkali separator 14-2. Oxygen alkali separator 15-1. Hydrogen condenser 15-2. Oxygen condenser 16-1. Hydrogen mist collector 16-2. Oxygen mist collector 17-1. Hydrogen purifier 17-2. Oxygen purifier 20. Ammonia distillation tower 21. Top condenser 22. Bottom reboiler 30. Ammonia decomposition reactor 3 1. Heater 32. Waste heat boiler 33. Process gas cooler 40. Adsorption tower 41. Compressor 42. Final cooler 43. Mixer 50. Hydrogen 50-1. Hydrogen-containing electrolyte 50-2. Alkaline hydrogen 51. Oxygen 51-1. Oxygen-containing electrolyte 51-2. Alkaline oxygen 52. Nitrogen 53. Ammonia-containing non-condensable gas 53-1. Ammonia vapor 54. Hydrogen-containing process gas 60. Deionized water 61. Alkali source 62. Alkali liquid 63. Ammonia water after heat exchange 64. Reflux condensate 65. Ammonia evaporation wastewater 66. Soft water 67. Steam DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0033] like Figure 1 As shown, the present invention is a highly efficient coupled hydrogen production process that can be implemented on a large scale. Different from the traditional water electrolysis process using alkali solution recycling, the alkali solution in the present invention does not continue to be recycled in the alkaline water electrolysis hydrogen production system 1 after participating in the water electrolysis reaction, but is directly sent to the ammonia distillation system 2. In the ammonia distillation system 2, the alkali solution is reacted with the fixed ammonium in the ammonia water to generate volatile ammonia by reactive distillation, and the volatile ammonia is stripped and enriched step by step to obtain ammonia-containing non-condensable gas; the ammonia-containing non-condensable gas is then sent to the ammonia decomposition system 3, and catalytically decomposed to obtain hydrogen-containing process gas; the hydrogen-containing process gas is further separated and purified by the hydrogen separation and collection system 4 to obtain hydrogen, and after being collected with the hydrogen produced by water electrolysis, it is sent to downstream hydrogen users as product hydrogen.

[0034] The main chemical reactions involved in the present invention are as follows:

[0035] Cathode reaction of alkaline water electrolysis:

[0036] 2H2O+2e - ——→H2+2OH -

[0037] Anode reaction of alkaline water electrolysis:

[0038]

[0039] Fixed ammonium decomposition reaction:

[0040]

[0041] Decomposition reaction of volatile ammonia:

[0042]

[0043] Ammonia decomposition reaction:

[0044]

[0045] The efficient and large-scale coupled hydrogen production process described in the present invention is combined with the existing coke oven gas purification or wastewater treatment process. Without adding additional alkaline electrolyte purification devices and equipment, it not only meets the strict requirements of the alkaline water electrolysis process for high-quality alkaline solution, but also realizes the continuous supply of alkaline solution required by the subsequent alkali system.

[0046] From the perspective of equipment configuration, the use of the efficient and large-scale coupled hydrogen production process described in the present invention can save the alkali circulation pump, alkali filter, alkali cooler required in the existing alkaline water electrolysis process system, and the alkali pump, alkali preheater and alkali tank in the existing ammonia distillation process system. That is, after integration, the investment and energy consumption of the two existing processes can be reduced.

[0047] From a product perspective, the use of an efficient and large-scale coupled hydrogen production process described in the present invention not only improves the conductivity of the alkaline electrolyte and the efficiency of hydrogen production by electrolysis, thereby increasing the output of hydrogen production by electrolysis, but also couples the ammonia distillation and ammonia decomposition systems to further convert the fixed ammonium and volatile ammonia in the ammonia into hydrogen, thereby greatly increasing the hydrogen output of the overall process.

[0048] like Figure 1 As shown, the high-efficiency and large-scale coupled hydrogen production process system described in the present invention is composed of an alkaline water electrolysis hydrogen production system 1, an ammonia distillation system 2, an ammonia decomposition system 3 and a hydrogen separation and collection system 4. Among them:

[0049] The alkaline water electrolysis hydrogen production system 1 mainly includes: an alkaline electrolytic cell 10, a water tank 11, an alkali preparation tank 12, a power supply 13, a hydrogen-alkali separator 14-1, an oxygen-alkali separator 14-2, a hydrogen condenser 15-1, an oxygen condenser 15-2, a hydrogen mist collector 16-1, an oxygen mist collector 16-2, a hydrogen purifier 17-1 and an oxygen purifier 17-2.

[0050] The ammonia distillation system 2 mainly includes: an ammonia distillation tower 20 , a tower top condenser 21 and a tower bottom reboiler 22 .

[0051] The ammonia decomposition system 3 mainly includes: an ammonia decomposition reactor 30 , a heater 31 , a waste heat boiler 32 and a process gas cooler 33 .

[0052] The hydrogen separation and collection system 4 mainly includes: a compressor 41 , a final cooler 42 , an adsorption tower 40 and a mixer 43 .

[0053] The principle and process of an efficient and large-scale coupled hydrogen production process described in the present invention are as follows:

[0054] Deionized water 60 from outside the boundary area is mixed with an alkali source 61 in an alkali preparation tank 12 through a water tank 11 to prepare an alkali solution 62 of a certain concentration, and then sent to the alkaline electrolytic cell 10. Using the direct current provided by the power supply 13, the alkaline electrolyte is electrolyzed in the alkaline electrolytic cell 10, and hydrogen 50 is generated at the cathode and oxygen 51 is generated at the anode. Although a part of the hydroxyl ions migrate from the cathode to the anode, they are not consumed, so the total amount remains unchanged. The hydrogen-containing electrolyte 50-1 engulfed with a large number of hydrogen bubbles and the oxygen-containing electrolyte 51-1 engulfed with a large number of oxygen bubbles enter the corresponding hydrogen-alkali separator 14-1 and oxygen-alkali separator 14-2 respectively, and the gas and most of the alkali solution are separated here. Then, the gas phase is discharged from the upper port of the corresponding separator, and the alkali solution 62 is discharged from the lower port of the corresponding separator. At this time, the alkaline hydrogen 50-2 and alkaline oxygen 51-2, which still have a certain temperature, are cooled and condensed by the corresponding hydrogen condenser 15-1 and oxygen condenser 15-2, and then enter the corresponding hydrogen purifier 17-1 and oxygen purifier 17-2 after the fine alkaline liquid droplets are captured by the hydrogen mist collector 16-1 and oxygen mist collector 16-2 for a second time. Drying and other operations are continued in the purifier to obtain high-purity hydrogen and oxygen. The alkaline liquid 62 separated in the above steps is collected and directly sent to the ammonia distillation system 2.

[0055] Since the temperature of the alkali solution 62 from the alkaline water electrolysis hydrogen production system 1 can meet the distillation requirements, it can directly enter the ammonia distillation tower 20, thereby eliminating the alkali solution preheater in the traditional ammonia distillation process. The ammonia water from the upstream unit needs to be heated by heat exchange before entering the ammonia distillation tower 20. The alkali solution 62 first reacts with the fixed ammonium in the ammonia water in the ammonia distillation tower 20 to generate volatile ammonia, and then further uses the heat of the rising steam at the bottom of the tower to convert the volatile ammonia into ammonia vapor. After step-by-step stripping, the ammonia vapor is gradually enriched at the top of the tower, and then enters the top condenser 21 for condensation. The reflux condensate 64 returns to the ammonia distillation tower 20 for reflux, and the ammonia-containing non-condensable gas 53 is sent to the subsequent ammonia decomposition system 3. The heat required by the ammonia distillation tower 20 is provided by the direct steam or indirect reboiler at the bottom of the tower, and the ammonia vapor wastewater 65 at the bottom of the tower is sent to the subsequent water treatment unit.

[0056] The ammonia-containing non-condensable gas 53 from the ammonia distillation system 3 enters the ammonia decomposition reactor 30 to undergo an ammonia decomposition reaction, generating a hydrogen-containing process gas 54 mainly composed of hydrogen and nitrogen. Since the ammonia decomposition reaction is an endothermic process, a heater 31 is required to continuously supply heat to the ammonia decomposition reactor 30. The required heat can be provided by gas combustion or high-temperature steam. After the reaction, the temperature of the hydrogen-containing process gas 54 is relatively high, and the waste heat can be recovered by the waste heat boiler 32, and then sent to the hydrogen separation and collection system 4 after being cooled by the process gas cooler 33.

[0057] In order to remove non-hydrogen components in the hydrogen-containing process gas 54 and purify the hydrogen, the hydrogen-containing process gas 54 is first pressurized by the compressor 41, and then cooled to the adsorption temperature by the final cooler 42. After entering the adsorption tower 40, the hydrogen with weak adsorption capacity first overflows from the top outlet of the tower, so that it can be separated and purified, and the gas with strong adsorption capacity is gradually adsorbed and accumulated in the bed layer in the tower. When the adsorption equilibrium is reached, the pressure of the adsorption tower 40 is lowered to gradually desorb this part of the gas and discharge it from the bottom outlet of the tower. By repeating the above operation, the hydrogen mixed in the process gas is separated from other gases. Finally, the separated and purified hydrogen is collected together with the hydrogen produced by water electrolysis and sent to downstream users as a hydrogen product.

[0058] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0059] [Example 1]

[0060] In this embodiment, deionized water 60 from outside the boundary area is mixed with sodium hydroxide 61 in the alkali preparation tank 12 through the water tank 11 to prepare a sodium hydroxide solution 62 with a concentration of 30%wt, and then sent to the alkaline electrolytic cell 10.

[0061] After the electrolysis reaction is carried out in the alkaline electrolytic cell 10, the hydrogen-containing electrolyte 50-1 entrained with a large number of hydrogen bubbles and the oxygen-containing electrolyte 51-1 entrained with a large number of oxygen bubbles enter the corresponding hydrogen-alkali separator 14-1 and oxygen-alkali separator 14-2 respectively. After separation, the alkaline hydrogen 50-2 and the alkaline oxygen 51-2 are discharged from the upper opening of the corresponding separator, and the separated alkaline liquid 62 is discharged from the lower opening. The alkaline hydrogen 50-2 and the alkaline oxygen 51-2 are cooled and condensed by the corresponding hydrogen condenser 15-1 and the oxygen condenser 15-2, and after the fine alkaline liquid droplets are captured for the second time by the corresponding hydrogen mist collector 16-1 and the oxygen mist collector 16-2, they enter the corresponding hydrogen purifier 17-1 and the oxygen purifier 17-2. Finally, after drying in the corresponding purifier, high-purity hydrogen 50 and oxygen 51 are obtained. The alkali solution 62 separated in the above process is collected at a temperature of 90° C. and directly sent to the ammonia distillation system 2.

[0062] The alkali solution 62 from the alkaline water electrolysis hydrogen production system 1 directly enters the ammonia distillation tower 20. The ammonia water 63 after heat exchange and temperature rise to 95°C also enters the ammonia distillation tower 20. In the ammonia distillation tower 20, the alkali solution 62 reacts with the fixed ammonium to generate volatile ammonia. After step-by-step stripping, the ammonia vapor 53-1 is gradually enriched at the top of the tower, and then enters the top condenser 21 for condensation. The condensate 64 returns to the ammonia distillation tower 20 for reflux, and the ammonia-containing non-condensable gas 53 is sent to the subsequent ammonia decomposition system 3. The heat required by the ammonia distillation tower 20 is provided by the direct steam at the bottom of the tower, and the ammonia vapor wastewater 65 at the bottom of the tower is sent to the subsequent water treatment unit.

[0063] The ammonia-containing non-condensable gas 53 from the ammonia distillation system 2 enters the ammonia decomposition reactor 30, and the heat 31 required for the reaction can be provided by the combustion of fuel gas. The ammonia decomposition reaction occurs at a temperature of 65-800°C and under the catalysis of a Ni-based catalyst to generate a hydrogen-containing process gas mainly composed of hydrogen and nitrogen; the hydrogen-containing process gas 54 uses the waste heat boiler 32 to recover waste heat and generate steam 67, which is then cooled by the process gas cooler 33 and sent to the hydrogen separation and collection system 4.

[0064] In the hydrogen separation and collection system 4, the hydrogen-containing process gas 54 is first pressurized by the compressor 41, then cooled to the adsorption temperature by the final cooler 42, and finally enters the adsorption tower 40; in the adsorption tower, the hydrogen 50 with weak adsorption capacity first overflows from the tower top outlet, and the gas with strong adsorption capacity (such as nitrogen 52) is discharged from the tower bottom outlet. After repeating the above operation, the hydrogen 50 mixed in the hydrogen-containing process gas 54 can be separated from other gases (such as nitrogen 52). Finally, the separated and purified hydrogen 50 is collected with the hydrogen 50 produced by water electrolysis and sent to downstream hydrogen users as product hydrogen.

[0065] [Example 2]

[0066] In this embodiment, deionized water 60 from outside the boundary area is mixed with potassium hydroxide 61 in the alkali preparation tank 12 through the water tank 11 to prepare a potassium hydroxide solution 62 with a concentration of 30% wt, which is then sent to the alkaline electrolytic cell 10.

[0067] After the electrolysis reaction in the alkaline electrolytic cell 10, the hydrogen-containing electrolyte 50-1 entrained with a large number of hydrogen bubbles and the oxygen-containing electrolyte 51-1 entrained with a large number of oxygen bubbles enter the corresponding hydrogen-alkali separator 14-1 and oxygen-alkali separator 14-2 respectively. After separation, the alkaline hydrogen 50-2 and the alkaline oxygen 51-2 are discharged from the upper port of the corresponding separator, and the alkaline liquid 62 is discharged from the lower port. The alkaline hydrogen 50-2 and the alkaline oxygen 51-2 are cooled and condensed by the corresponding hydrogen condenser 15-1 and oxygen condenser 15-2, and after the corresponding hydrogen mist collector 16-1 and oxygen mist collector 16-2 capture fine alkaline liquid droplets for the second time, they enter the corresponding hydrogen purifier 17-1 and oxygen purifier 17-2. Finally, after drying in the corresponding purifier, high-purity hydrogen 50 and oxygen 51 are obtained. After the alkaline liquid 62 separated in the above process is collected, the temperature is 90°C and it is directly sent to the ammonia distillation system 2.

[0068] The alkali solution 62 from the alkaline water electrolysis hydrogen production system 1 directly enters the ammonia distillation tower 20. The ammonia water 63 after heat exchange and temperature rise to 95°C also enters the ammonia distillation tower 20. In the ammonia distillation tower 20, the alkali solution 62 reacts with the fixed ammonium to generate volatile ammonia. After step-by-step stripping, the ammonia vapor 53-1 is gradually enriched at the top of the tower, and then enters the top condenser 21 for condensation. The condensate 64 returns to the ammonia distillation tower 20 for reflux, and the ammonia-containing non-condensable gas 53 is sent to the subsequent ammonia decomposition system 3. The heat required by the ammonia distillation tower 20 is provided by the bottom reboiler 22, and the ammonia wastewater 65 at the bottom of the tower is sent to the subsequent water treatment unit.

[0069] The ammonia-containing non-condensable gas 53 from the ammonia distillation system 2 enters the ammonia decomposition reactor 30, and the heat 31 required for the reaction is provided by high-temperature steam. Ammonia decomposition reaction occurs at a temperature of 350-650°C and under the catalysis of a Ru-based catalyst, generating a hydrogen-containing process gas 54 mainly composed of hydrogen and nitrogen. Since the temperature of the hydrogen-containing process gas 54 is relatively high, the waste heat is recovered by the waste heat boiler 32 to generate steam 67, which is then cooled by the process gas cooler 33 and sent to the hydrogen separation and collection system 4.

[0070] In the hydrogen separation and collection system 4, the hydrogen-containing process gas 54 is first pressurized by the compressor 41, then cooled to the adsorption temperature by the final cooler 42, and finally enters the adsorption tower 40. In the adsorption tower 40, the hydrogen 50 with weak adsorption capacity first overflows from the top outlet of the tower, and the gas with strong adsorption capacity (such as nitrogen 52) is discharged from the bottom outlet of the tower. After repeating the above operation, the hydrogen 50 mixed in the hydrogen-containing process gas 54 can be separated from other gases (such as nitrogen 52). Finally, the separated and purified hydrogen 50 is collected with the hydrogen 50 produced by water electrolysis and sent to downstream hydrogen users as product hydrogen.

[0071] 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. An efficient and large-scale coupled hydrogen production process, characterized in that: The alkaline water electrolysis hydrogen production system, ammonia distillation system, ammonia decomposition system and hydrogen separation and collection system are coupled. The alkali liquid in the alkaline water electrolysis hydrogen production system is not recycled in the electrolysis system, but is directly sent to the ammonia distillation system. Reactive distillation is used to make the alkali liquid react with the fixed ammonium in the ammonia water to generate volatile ammonia. After step-by-step stripping and condensation, the enriched ammonia-containing non-condensable gas is sent to the ammonia decomposition system for catalytic decomposition into hydrogen-containing process gas. Hydrogen is obtained through separation and purification, and finally collected with the hydrogen produced by water electrolysis and sent to downstream users as product hydrogen.

2. The highly efficient and large-scale coupled hydrogen production process according to claim 1, characterized in that: The specific steps include: 1) In the alkaline water electrolysis hydrogen production system, the alkaline electrolyte after participating in the water electrolysis reaction in the alkaline electrolytic cell is directly sent to the ammonia distillation system after gas-liquid separation; the high-purity hydrogen obtained after gas-liquid separation, mist capture and purification of the hydrogen-containing electrolyte is sent to the hydrogen separation and collection system, and the oxygen obtained after gas-liquid separation, mist capture and purification of the oxygen-containing electrolyte is sent to downstream oxygen users; 2) In the ammonia distillation system, the alkali solution from the alkaline water electrolysis hydrogen production system reacts with the heat exchange ammonia water in the distillation tower, and the generated ammonia vapor is condensed by step-by-step stripping, and the obtained ammonia-containing non-condensable gas is sent to the ammonia decomposition system; 3) In the ammonia decomposition system, the ammonia-containing non-condensable gas is catalytically decomposed into hydrogen-containing process gas; 4) In the hydrogen separation and collection system, the hydrogen in the hydrogen-containing process gas is separated and purified, and the obtained hydrogen is collected with the hydrogen sent out by the alkaline water electrolysis hydrogen production system and sent to downstream hydrogen users as product hydrogen.

3. An efficient and large-scale coupled hydrogen production process according to claim 2, characterized in that: In the step 1), the alkali solution is a strong alkali solution including potassium hydroxide and sodium hydroxide, and the concentration of the alkali solution is 2%wt to 40%wt.

4. The highly efficient and large-scale coupled hydrogen production process according to claim 2, characterized in that: In the step 3), a ruthenium-based or nickel-based catalyst is used to catalytically decompose the ammonia-containing non-condensable gas. The reaction is carried out at 600-850° C. The required heat is provided by gas combustion or high-temperature steam. The waste heat of the hydrogen-containing process gas after the reaction is recovered through a waste heat recovery device.

5. The highly efficient and large-scale coupled hydrogen production process according to claim 2, characterized in that: In the step 4), the method of separating and purifying the hydrogen-containing process gas includes temperature swing adsorption or pressure swing adsorption; the adsorbent includes molecular sieve or activated carbon.

6. An efficient and large-scale coupled hydrogen production system for realizing the process as claimed in claim 1 or 2, characterized in that: It includes an alkaline water electrolysis hydrogen production system, an ammonia distillation system, an ammonia decomposition system and a hydrogen separation and collection system; the alkaline electrolytic cell in the alkaline water electrolysis hydrogen production system is connected to the ammonia distillation tower in the ammonia distillation system through an alkaline liquid delivery pipeline, and a gas-liquid separator is arranged on the alkaline liquid delivery pipeline to separate hydrogen and oxygen; the hydrogen outlet of the gas-liquid separator is connected to the mixer upstream of the product hydrogen pipeline through a hydrogen pipeline; the ammonia distillation system is connected to the ammonia decomposition reactor in the ammonia decomposition system through an ammonia-containing non-condensable steam pipeline; the ammonia decomposition system is connected to the hydrogen separation and collection system through a hydrogen-containing process gas pipeline; the hydrogen separation and collection system includes a compressor, a final cooler, an adsorption tower and a mixer connected in sequence, and the hydrogen outlet pipeline at the top of the adsorption tower is connected to the product hydrogen pipeline through a mixer.

7. The efficient and large-scale coupled hydrogen production system according to claim 6, characterized in that: The alkali solution delivery pipeline includes a hydrogen-containing electrolyte pipeline, an oxygen-containing electrolyte pipeline, an alkali solution pipeline 1 and an alkali solution pipeline 2; the gas-liquid separator includes a hydrogen-alkali separator and an oxygen-alkali separator; the alkaline electrolyzer is connected to the hydrogen-alkali separator through the hydrogen-containing electrolyte pipeline, and the alkali solution outlet of the hydrogen-alkali separator is connected to the alkali solution pipeline 1; the hydrogen outlet of the hydrogen-alkali separator is connected to the hydrogen pipeline, and a hydrogen condenser, a hydrogen mist collector and a hydrogen purifier are sequentially arranged on the hydrogen pipeline along the flow direction of hydrogen; the alkaline electrolyzer is connected to the oxygen-alkali separator through the oxygen-containing electrolyte pipeline, and the alkali solution outlet of the oxygen-alkali separator is connected to the alkali solution pipeline 2; the oxygen outlet of the oxygen-alkali separator is connected to the oxygen pipeline, and an oxygen condenser, an oxygen mist collector and an oxygen purifier are sequentially arranged on the oxygen pipeline along the flow direction of oxygen; the alkali solution pipeline 1 is connected to the alkali solution inlet of the ammonia distillation tower after merging with the alkali solution pipeline 2.

8. An efficient and large-scale coupled hydrogen production system according to claim 6 or 7, characterized in that: The ammonia vapor outlet at the top of the ammonia distillation tower is connected to the tower top condenser through an ammonia vapor pipeline, and the ammonia-containing non-condensable gas outlet of the tower top condenser is connected to the ammonia decomposition reactor through an ammonia-containing non-condensable gas pipeline; the condensate of the tower top condenser is connected to the reflux liquid inlet at the top of the ammonia distillation tower through a reflux condensate pipeline; an ammonia water inlet is arranged at the top of the ammonia distillation tower, a heat source inlet is arranged at the bottom of the tower to be connected to the tower bottom reboiler, and an ammonia wastewater outlet is arranged at the bottom.

9. The efficient and large-scale coupled hydrogen production system according to claim 6, characterized in that: The ammonia decomposition system consists of an ammonia decomposition reactor, a heater, a waste heat boiler and a process gas cooler; a heater is arranged at one end of the ammonia decomposition reactor close to the inlet of the ammonia-containing non-condensable gas, and the hydrogen-containing process gas outlet of the ammonia decomposition reactor is connected to the hydrogen separation and collection system through a hydrogen-containing process gas pipeline; a waste heat boiler is arranged on the hydrogen-containing process gas pipeline close to the ammonia decomposition reactor, and a process gas cooler is arranged on the hydrogen-containing process gas pipeline downstream of the waste heat boiler.

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