Pressure fluctuation absorption device for high-purity hydrogen purification from ammonia decomposition and hydrogen purification method using same

Abstract

The present disclosure relates to a pressure fluctuation absorption apparatus for performing high-purity hydrogen purification from ammonia decomposition and a hydrogen purification method using the same, and more particularly, the pressure fluctuation absorption apparatus includes a plurality of absorption towers including a guard bed unit and a hydrogen purification unit, each absorption tower is filled with a different absorbent to purify high-purity hydrogen from mixed hydrogen gas generated after ammonia decomposition, so that the absorbent for removing ammonia is easy to replace, the possibility that the service life of the absorbent in the hydrogen purification unit is sharply shortened due to an extremely small amount of ammonia is minimized, the hydrogen of the protective bed unit is effectively recovered, and the service life of the protective bed unit is prolonged. Thus, compared with conventional pressure fluctuation absorption processes including a pretreatment unit and a hydrogen purification unit, the hydrogen recovery rate is maximized, and a significant change in ammonia concentration in the raw material is coped with.

Description

Technical Field

[0001] The present disclosure relates to a pressure swing adsorption apparatus for high-purity hydrogen purification from ammonia decomposition and a hydrogen purification method using the pressure swing adsorption apparatus. More specifically, the present disclosure relates to a pressure swing adsorption apparatus for high-purity hydrogen purification from ammonia decomposition, the pressure swing adsorption apparatus including a plurality of absorption towers, the plurality of absorption towers including a guard bed unit and a hydrogen purification unit, to reduce the amount of impurities (e.g., nitrogen (N 2 ), ammonia (NH 3 ), and moisture (H 2 O)) in a mixed gas containing hydrogen to a trace level by increasing the physical absorption selectivity for the impurities to produce a high-purity hydrogen product, and to a hydrogen purification method using the pressure swing adsorption apparatus. Background Art

[0002] Recently, in order to achieve the goal of carbon neutrality, the development of ammonia-based hydrogen storage, transportation, extraction, and utilization technologies has received increasing attention. When importing clean ammonia from abroad, for domestic hydrogen supply, an ammonia decomposition technology is required. The products generated after ammonia decomposition include hydrogen, as well as nitrogen (N 2 ), ammonia (NH 3 ), and moisture (H 2 O). Therefore, in order to produce high-purity hydrogen, it is necessary to remove nitrogen, moisture, and ammonia. For hydrogen purification from ammonia decomposition, generally, it is necessary to remove moisture, ammonia, and nitrogen in sequence, and different absorbents can be used.

[0003] Absorption based on chemical bonding with the acid group of the absorbent is mainly used to remove ammonia, and a temperature swing absorption purification method is used to regenerate the absorbent used at high temperatures. The pressure swing adsorption purification method is only used in physical absorption between impurities and the absorbent.

[0004] Currently, a method for producing high-purity hydrogen using ammonia has not been commercialized, and in order to isolate only high-purity hydrogen from the decomposed ammonia gas, a hybrid process of a temperature swing absorption (TSA) process for removing undecomposed ammonia and a pressure swing adsorption (PSA) process for removing nitrogen is being developed.

[0005] However, since existing commercial ammonia absorbents absorb ammonia through an acid-base reaction by a chemical method, they can only absorb and desorb ammonia through a temperature swing absorption process, and an absorbent capable of physical absorption is required for use in a pressure swing adsorption process. In addition, existing pressure swing adsorption hydrogen purification processes for high-purity hydrogen production involve from a mixture containing H 2 , CO 2, CH 4 and selectively remove CO, CH 4 and CO 2 from a mixed gas of, and is only intended to minimize the size of the apparatus and improve the hydrogen recovery rate.

[0006] U.S. Patent No. 3,986,849 discloses a process for removing CO 2 and N 2 contained in hydrogen, in which at least eight absorption towers (at least two of the eight absorption towers process the feed gas simultaneously) are utilized and there is at least a three-stage pressure equalization.

[0007] In addition, U.S. Patent No. 5,250,088 discloses a pressure swing absorption process that uses more than three absorption towers to remove moisture and hydrocarbons contained in hydrogen, and proposes a method for improving the efficiency of the separation process by further including a tank for storing purge gas.

[0008] However, although these prior art documents can improve the efficiency of the separation process by using multiple absorption towers, they have the following problems: When the hydrogen purifier for purifying hydrogen from ammonia decomposition does not operate, the desorption of pre-absorbed ammonia causes contamination of the absorbent for nitrogen separation and shortens its service life. In addition, since the service life of the absorbent for separating ammonia is shorter than that of the absorbent for separating nitrogen, all the absorbents need to be replaced when the absorbents are stacked and used.

[0009] Therefore, it is necessary to study a new separation process that not only selectively absorbs moisture, ammonia, and nitrogen from the mixed hydrogen gas during the ammonia decomposition process and purifies high-purity hydrogen, but also minimizes the shortening of the service life of the absorbent caused by impurities (e.g., trace amounts of ammonia).

[0010] [Related Literature]

[0011] [Patent Literature]

[0012] (Patent Document 1) U.S. Patent No. 3,986,849

[0013] (Patent Document 2) U.S. Patent No. 5,250,088 Summary of the Invention

[0014] Technical Problem

[0015] To solve the above problems, the present disclosure aims to provide a pressure swing absorption apparatus for hydrogen purification from ammonia decomposition, which includes a plurality of absorption towers, and the plurality of absorption towers include a guard bed unit and a hydrogen purification unit, wherein each absorption tower is filled with a different absorbent.

[0016] The present disclosure also aims to provide a hydrogen purification method for high-purity hydrogen purification using a pressure swing absorption device, which improves the selective absorption of moisture, ammonia, and nitrogen in mixed hydrogen and maximizes the hydrogen recovery rate and productivity.

[0017] Technical solution

[0018] The present disclosure provides a pressure swing absorption device for hydrogen purification from ammonia decomposition, which includes: a plurality of absorption towers, the plurality of absorption towers including a guard bed unit and a hydrogen purification unit, the plurality of absorption towers being connected to a raw material supply pipe; a vacuum pump, the vacuum pump being connected to the absorption towers to keep the absorption towers in a vacuum state; and a plurality of valves for opening / closing a plurality of pipes connected to the absorption towers and the vacuum pump, wherein the guard bed unit is provided at the bottom of the hydrogen purification unit, and the absorption towers in the guard bed unit are filled with a first absorbent and a second absorbent in a multi-layer structure to selectively absorb and remove moisture and ammonia contained in the mixed hydrogen generated after ammonia decomposition supplied through the raw material supply pipe, wherein the hydrogen purification unit is provided on top of the guard bed unit, and the absorption towers in the hydrogen purification unit are filled with a third absorbent to selectively absorb and remove nitrogen contained in the mixed hydrogen free of moisture and ammonia from the guard bed unit.

[0019] In addition, the present disclosure provides a hydrogen purification method using the pressure swing absorption device according to the present disclosure, the pressure swing absorption device including: a plurality of absorption towers, the plurality of absorption towers including a guard bed unit and a hydrogen purification unit, the plurality of absorption towers being connected to a raw material supply pipe; a vacuum pump, the vacuum pump being connected to the absorption towers to keep the absorption towers in a vacuum state; and a plurality of valves for opening / closing a plurality of pipes connected to the absorption towers and the vacuum pump, the hydrogen purification method including: supplying the mixed hydrogen generated after ammonia decomposition to the absorption towers of the guard bed unit through the raw material supply pipe; selectively absorbing and removing moisture by passing the supplied mixed hydrogen through the first absorbent at the lower layer region of the absorption towers filled in the guard bed unit; selectively absorbing and removing ammonia by allowing the mixed hydrogen free of moisture to pass through the second absorbent at the upper layer region of the absorption towers filled in the guard bed unit; supplying the mixed hydrogen free of moisture and ammonia to the absorption towers of the hydrogen purification unit; and selectively absorbing and removing nitrogen by allowing the supplied mixed hydrogen free of moisture and ammonia to pass through the third absorbent in the absorption towers filled in the hydrogen purification unit to obtain purified hydrogen.

[0020] Advantageous effects

[0021] Since the pressure swing absorption apparatus according to the present disclosure includes a plurality of absorption towers, the plurality of absorption towers including a guard bed unit and a hydrogen purification unit, wherein each absorption tower is filled with a different absorbent, high-purity hydrogen can be purified from the mixed hydrogen gas generated after ammonia decomposition, making it easy to replace the absorbent for removing ammonia and minimizing the possibility that the service life of the absorbent in the hydrogen purification unit is drastically shortened due to extremely small amounts of ammonia.

[0022] In addition, the pressure swing absorption apparatus of the present disclosure can effectively recover the hydrogen in the guard bed unit, thereby maximizing the hydrogen recovery rate compared to conventional pressure swing absorption processes including a pretreatment unit and a hydrogen purification unit and coping with large changes in the ammonia concentration in the raw material. Further, when the apparatus stops operating for a short time or is idle for a long time, the residual gas in the guard bed unit can be prevented from entering the hydrogen purification unit, thereby preventing contamination of the absorbent filled in the hydrogen purification unit and maintaining the separation performance.

[0023] In addition, the hydrogen purification method using the pressure swing absorption apparatus of the present disclosure can physically absorb impurities (such as moisture (H 2 O), ammonia (NH 3 ), and nitrogen (N 2 )) contained in the mixed hydrogen gas generated after ammonia decomposition to extremely small amounts or less than extremely small amounts, thereby achieving high-purity hydrogen purification and improving the selective absorption of moisture, ammonia, and nitrogen, and thus maximizing the hydrogen recovery rate and productivity. Further, the initial investment cost is low, and when only the pressure swing absorption process is applied, the temperature swing absorption process is not introduced, so the need for a heat source for regeneration can be eliminated, thereby reducing the driving cost.

[0024] The effects of the present disclosure are not limited to the above effects. It should be understood that the effects of the present disclosure include all inferable effects from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a diagram of a pressure swing absorption apparatus according to the present disclosure including a five-bed guard bed unit and a hydrogen purification unit.

[0026] Figure 2 is a diagram of a pressure swing absorption apparatus according to the present disclosure including a six-bed guard bed unit and a hydrogen purification unit. DETAILED DESCRIPTION

[0027] Hereinafter, the present disclosure will be described in more detail by way of examples.

[0028] The present disclosure relates to a pressure swing absorption (PSA) apparatus for purifying high-purity hydrogen by removing moisture, ammonia, and nitrogen from mixed hydrogen gas generated from ammonia decomposition and a hydrogen purification method using the pressure swing absorption apparatus.

[0029] As described above, when the existing pressure swing absorption process for purifying hydrogen from ammonia decomposition sequentially removes moisture, ammonia, and nitrogen, in the case where ammonia is absorbed onto the absorbent for separating nitrogen, the absorbent for separating nitrogen loses its absorption capacity. Therefore, it is necessary to prevent ammonia from entering the absorbent for nitrogen. Additionally, when the hydrogen purifier for purifying hydrogen from ammonia decomposition is not operating, the pre-absorbed ammonia may be desorbed, resulting in contamination of the absorbent for separating nitrogen and shortening the service life of the absorbent. Further, since the service life of the absorbent for separating ammonia is shorter than that of the absorbent for separating nitrogen, when the absorbents are stacked and used, it is necessary to replace all the absorbents.

[0030] Accordingly, the present disclosure provides a pressure swing absorption apparatus including a plurality of absorption towers, the plurality of absorption towers including a guard bed unit for separating moisture and ammonia and a hydrogen purification unit for separating nitrogen, wherein each absorption tower is filled with a different absorbent, thereby achieving high-purity hydrogen purification from the mixed hydrogen gas generated after ammonia decomposition, making it easy to replace the absorbent for removing ammonia, and minimizing the possibility that the service life of the absorbent in the hydrogen purification unit is drastically shortened due to extremely small amounts of ammonia.

[0031] In addition, hydrogen in the guard bed unit can be effectively recovered, thereby maximizing the hydrogen recovery rate compared to the existing pressure swing absorption process and coping with a large change in the ammonia concentration in the raw material. Further, when the apparatus stops operating for a short time or is idle for a long time, it is possible to prevent the residual gas in the guard bed unit from entering the hydrogen purification unit, thereby preventing contamination of the absorbent filled in the hydrogen purification unit and maintaining the separation performance.

[0032] (a) Configuration of the pressure swing absorption apparatus 100

[0033] Specifically, the present disclosure provides a pressure swing absorption apparatus 100 for purifying hydrogen from ammonia decomposition, which includes: a plurality of absorption towers including a guard bed unit and a hydrogen purification unit, the plurality of absorption towers being connected to a raw material supply pipe 101; a vacuum pump 131 connected to the absorption towers to keep the absorption towers in a vacuum state; and a plurality of valves for opening / closing a plurality of pipes connected to the absorption towers and the vacuum pump 131, wherein the guard bed unit is provided at the bottom of the hydrogen purification unit, and the absorption towers in the guard bed unit are filled with a first absorbent and a second absorbent in a multi-layer structure to selectively absorb and remove moisture and ammonia contained in the mixed hydrogen gas generated after ammonia decomposition supplied through the raw material supply pipe 101, and hydrogen purification units 111 to 116 are provided at the top of the guard bed unit, and the absorption towers in the hydrogen purification unit are filled with a third absorbent to selectively absorb and remove nitrogen contained in the mixed hydrogen gas free of moisture and ammonia from the guard bed unit.

[0034] The pressure swing absorption equipment can reduce the amount of impurities to an extremely low level by increasing the physical absorption selectivity for impurities (e.g., moisture (H 2 O), unreacted ammonia (NH 3 ), and nitrogen (N 2 )) generated in the ammonia decomposition process, to produce high-purity hydrogen, rather than removing impurities (e.g., carbon monoxide (CO), methane (CH 4 ), and carbon dioxide (CO 2 )) in the hydrogen purification process. Preferably, the pressure swing absorption equipment 100 can be a vacuum pressure swing absorption (VPSA) equipment.

[0035] Existing four-bed pressure swing absorption equipment uses at least two types of absorbents stacked in an absorption tower to simultaneously absorb moisture, ammonia, and nitrogen from mixed hydrogen to purify hydrogen. However, when unreacted ammonia contacts the absorbent used to absorb nitrogen, the performance and service life of the absorbent may be reduced. Additionally, the pressure swing absorption equipment can include a pretreatment unit with two or more absorption towers arranged in parallel and a hydrogen purification unit with four or more absorption towers arranged in parallel. However, there are limitations in increasing the hydrogen recovery rate because it is difficult to recover hydrogen in the absorption towers of the pretreatment unit, and each of the pretreatment unit and the hydrogen purification unit requires its own vacuum pump, resulting in higher power consumption. The above-described absorption process configuration is not easily adaptable to changes in the ammonia concentration in the raw material, and when replacing the absorbent, all the stacked absorbents must be replaced, resulting in increased investment costs and driving costs.

[0036] The present disclosure includes a plurality of absorption towers, which include a guard bed unit for absorbing and removing moisture and ammonia and a hydrogen purification unit for absorbing and purifying nitrogen after absorbing and removing moisture and ammonia, thereby solving the problem of reduced performance and service life of the absorbent for absorbing nitrogen and achieving savings in investment costs and operating costs.

[0037] The guard bed unit and the hydrogen purification unit can have a closed system design and can be configured to cooperate with each other to perform process steps.

[0038] The guard bed unit and the hydrogen purification unit can be connected in series, and two or more absorption tower groups each including a guard bed unit and a hydrogen purification unit connected in series can be arranged in parallel. Preferably, four or more absorption tower groups are arranged in parallel. More preferably, five to six absorption tower groups are arranged in parallel. Each absorption tower group can allow the mixed hydrogen supplied through the raw material supply pipe 101 to sequentially pass through the guard bed unit and then through the hydrogen purification unit to perform an absorption process, a discharge process, a cleaning process, a raw material pressurization process, and a product pressurization process to absorb moisture and ammonia, thereby purifying high-purity hydrogen.

[0039] When the mixed hydrogen flows in the raw material flow direction (downstream direction), the minimum pressure of the absorption tower in the guard bed unit can be maintained at not less than 1 / 4 of the raw material supply pressure, preferably not less than 1 / 3 to 2 / 5 of the raw material supply pressure. In the case where the minimum pressure is lower than 1 / 4 of the raw material supply pressure, ammonia in the guard bed unit may enter the hydrogen purification unit.

[0040] The lower region in the absorption tower of the guard bed unit may be filled with a first absorbent, and the upper region may be filled with a second absorbent. When the mixed hydrogen is supplied from the raw material supply pipe 101, the mixed hydrogen can selectively absorb moisture and ammonia while passing through the lower region and the upper region in the absorption tower in sequence.

[0041] The first absorbent may be filled in the lower region in the absorption tower of the guard bed unit, and may be at least one selected from the group consisting of first activated alumina capable of removing moisture, silica gel, alumina silica gel, and zeolite. Preferably, it may be first activated alumina or silica gel.

[0042] The content of the first absorbent may be 1 wt% to 70 wt% relative to the second absorbent, preferably 1 wt% to 60 wt%, and most preferably 1 wt% to 50 wt%. When the amount of the first absorbent is less than 1 wt%, moisture removal may be insufficient. On the contrary, when the amount of the first absorbent is greater than 70 wt%, it may not be easy to cope with changes in ammonia concentration.

[0043] The second absorbent may be filled in the upper region in the absorption tower of the guard bed unit, and may be at least one selected from the group consisting of metal-impregnated activated carbon, silica gel, alumina silica gel, zeolite, and second activated alumina. Preferably, it may be metal-impregnated activated carbon, silica gel, or zeolite.

[0044] The metal-impregnated activated carbon has high ammonia selectivity and high ammonia absorption capacity. The metal-impregnated activated carbon may be activated carbon impregnated with at least one selected from the group consisting of Mg, Ca, Mn, and Cu. Preferably, it may be Mg-impregnated activated carbon or Ca-impregnated activated carbon. Most preferably, it may be Mg-impregnated activated carbon. The Mg-impregnated activated carbon has higher ammonia absorption performance compared to other metal-impregnated activated carbons, and has a high ammonia absorption capacity even in a small amount.

[0045] The metal impregnation amount in the metal-impregnated activated carbon can be 1 wt% to 10 wt%, preferably, it can be 1 wt% to 8 wt%, and most preferably, it can be 1 wt% to 6 wt%. In this case, when the metal impregnation amount is less than 1 wt%, the ammonia absorption performance may not reach the expected performance level. On the contrary, when the metal impregnation amount is greater than 10 wt%, the increase in the absorbent regeneration time is not conducive to the pressure swing absorption process, making it difficult to absorb ammonia to an extremely low level below 0.1 ppm.

[0046] Silica gel, zeolite, and the second activated alumina can also have high ammonia selectivity and rapid ammonia absorption, so they can remove ammonia in very small amounts in the pressure swing absorption process.

[0047] The content of the second absorbent can be 30 wt% to 99 wt% relative to the first absorbent, preferably, it is 3 wt% to 60 wt%, and most preferably, it is 12 wt% to 50 wt%. When the amount of the second absorbent is less than 30 wt%, the ammonia absorption amount may decrease. On the contrary, when the amount of the second absorbent is greater than 99 wt%, it may not be easy to cope with the change in the moisture concentration.

[0048] The hydrogen purification unit can include two or more absorption towers arranged in parallel, preferably, four or more absorption towers arranged in parallel, and most preferably, five to six absorption towers arranged in parallel. And the hydrogen purification unit can pass the mixed hydrogen that has been purified of moisture and ammonia through the guard bed unit to jointly perform an absorption process, a primary pressure equalization process, a clean supply process, a secondary pressure equalization process, an emission process, a clean and pressurization process with the guard bed unit to absorb and remove nitrogen, so as to obtain hydrogen with a high hydrogen recovery rate and high purity.

[0049] The absorption towers in the hydrogen purification unit are filled with a third absorbent to selectively absorb the nitrogen contained in the mixed hydrogen that has been purified of moisture and ammonia to purify high-purity hydrogen.

[0050] The third absorbent can be at least one selected from the group consisting of zeolite NaA, zeolite CaA, zeolite CaNaA, zeolite LiX, zeolite LiNaX, zeolite LiCaX, zeolite LiNaCaX, zeolite NaX, zeolite CaX, zeolite CaNaX, and zeolite KX. Preferably, it can be zeolite LiX, zeolite CaX, or a mixture thereof, and most preferably, it is zeolite CaX.

[0051] The pressure swing absorption device 100 can further include a hydrogen storage tank to capture the purified hydrogen from the absorption tower.

[0052] Specifically, although not explicitly described in the following examples or comparative examples, in the pressure swing absorption apparatus 100 according to the present disclosure, the hydrogen purification process is continuously performed 100 times using the mixed hydrogen gas generated after ammonia decomposition under the following eight different conditions.

[0053] Therefore, different from other conditions and numerical ranges, when all of the following conditions are satisfied, the purity of the purified hydrogen is 99.99% or more, and the hydrogen recovery rate shows an improved value of 92.5% or more.

[0054] ① The minimum pressure of the absorption tower in the guard bed unit is maintained at not less than 1 / 3 to 2 / 5 of the raw material supply pressure; ② The first absorbent is filled in the lower layer region of the absorption tower in the guard bed unit and is the first activated alumina or silica gel capable of removing moisture; ③ The first absorbent is filled in the absorption tower of the guard bed unit in an amount of 10 wt% to 35 wt% relative to the second absorbent; ④ The second absorbent is filled in the upper layer region of the absorption tower in the guard bed unit and is metal-impregnated activated carbon capable of removing ammonia; ⑤ The second absorbent is filled in the absorption tower of the guard bed unit in an amount of 65 wt% to 90 wt% relative to the first absorbent; ⑥ The metal-impregnated activated carbon is magnesium (Mg)-impregnated activated carbon or calcium (Ca)-impregnated activated carbon; ⑦ The impregnation amount of the metal in the metal-impregnated activated carbon is 1 wt% to 8 wt%; ⑧ The third absorbent is zeolite LiX, zeolite CaX, or a mixture of zeolite LiX and zeolite CaX.

[0055] However, when any one of the above eight conditions is not satisfied, the recovery rate of the purified hydrogen is as low as 75% or less, unabsorbed moisture, ammonia, or nitrogen is detected above the reference range, and the purity of the purified hydrogen shows a low value of 86% or less.

[0056] Figure 1 It is a diagram of a pressure swing absorption apparatus 100 according to the present disclosure, including a five-bed guard bed unit and a hydrogen purification unit. Refer to Figure 1 , the pressure swing absorption apparatus 100 includes: a plurality of absorption towers 111 to 115, the plurality of absorption towers 111 to 115 including a guard bed unit 121 to 125 and a hydrogen purification unit connected to a raw material supply pipe 101; a vacuum pump 131, the vacuum pump 131 being connected to keep each of the guard bed units 121 to 125 and the plurality of absorption towers 111 to 115 connected in series with each other in a vacuum state; and a plurality of valves for opening / closing a plurality of pipes 102 to 108 connecting the guard bed units 121 to 125, the plurality of absorption towers 111 to 115, and the vacuum pump 131.

[0057] In addition, it shows a guard bed unit 121 to 125 in which five absorption towers GB1, GB2, GB3, GB4, and GB5 are arranged in parallel, and a hydrogen purification unit in which five absorption towers 111 to 115 are arranged in parallel. Each absorption tower of the guard bed unit can be connected in series with each absorption tower of the hydrogen purification unit, so as to perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge providing step, a third pressure equalization step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a final pressurization step by product in an organic manner in one cycle.

[0058] The bottoms of the absorption towers in the guard bed units 121 to 126 are connected to a raw material supply pipe 101 for supplying mixed hydrogen through a first raw material supply valve 11. Each absorption tower of the guard bed unit and the hydrogen purification unit can perform a process including an absorption step, a first pressure equalization step, a second pressure equalization step, a purge providing step, a third pressure equalization step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a final pressurization step by product on the moisture, ammonia, and nitrogen contained in the mixed hydrogen supplied through the raw material supply pipe 101 in one cycle, so as to purify high-purity hydrogen from the products generated after ammonia decomposition.

[0059] The first to fifth countercurrent discharge valves 12, 22, 32, 42, 52 are arranged below the absorption tower of the protective bed unit. The first to fifth countercurrent discharge valves 12, 22, 32, 42, 52 are used to adjust the pressure through the first to fifth raw material supply valves 11, 21, 31, 41, 51 for supplying mixed hydrogen from the raw material supply pipe 101 to them and the vacuum pump 131. In addition, the first to fifth outlet valves 11-1, 21-1, 31-1, 41-1, 51-1 are arranged above the absorption tower of the protective bed unit, and the mixed hydrogen without moisture and ammonia is discharged from the first to fifth outlet valves 11-1, 21-1, 31-1, 41-1, 51-1.

[0060] The first to fifth vacuum purge valves 16, 26, 36, 46, 56 are arranged above the absorption tower of the hydrogen purification unit. The first to sixth pressure equalization valves 15, 25, 35, 45, 55 for pressure equalization are arranged at a higher position connected to the vacuum purge valves, and the first to fifth pressurization valves 14, 24, 34, 44, 54 for product pressurization are arranged at an even higher position connected to the pressure equalization valves. In addition, the first to fifth product generation valves 13, 23, 33, 43, 53 are arranged at the highest position above the absorption tower of the hydrogen purification unit to transport the purified hydrogen, and the first to sixth countercurrent discharge valves 12-1, 22-1, 32-1, 42-1, 52-1 are arranged below the absorption tower to adjust the pressure of the absorption tower.

[0061] The protective bed unit and the hydrogen purification unit can perform the desorption process by providing clean gas through the first to fifth countercurrent discharge valves 12~52, 12-1~52-1 in the vacuum purge step. Each of the countercurrent discharge valves of the protective bed unit and the hydrogen purification unit is arranged separately to prevent ammonia from flowing back from the protective bed unit to the hydrogen purification unit due to the pressure difference.

[0062] The absorption towers 121~126 of the protective bed unit and the absorption towers 111~116 of the hydrogen purification unit are connected in series through a plurality of pipes 102~108 connecting each absorption tower. Among them, the protective bed unit is configured to remove moisture and ammonia, and the hydrogen purification unit is configured to remove nitrogen, so as to achieve high-purity hydrogen production, high hydrogen recovery rate and low-power operation.

[0063] Figure 2 is a diagram of the pressure swing absorption device 100-1 including a six-bed protective bed unit and a hydrogen purification unit according to the present disclosure. Refer to Figure 2, the six-bed pressure swing absorption apparatus 100-1 can improve the recovery rate more than the five-bed pressure swing absorption apparatus 100, and the basic purification method is similar to the following hydrogen purification method using the five-bed pressure swing absorption apparatus, in the order of absorption, pressure equalization, purge supply, pressure equalization, countercurrent discharge, vacuum purge, pressurization, and product pressurization.

[0064] (b) Hydrogen purification method using a pressure swing absorption apparatus including a guard bed unit and a hydrogen purification unit

[0065] In addition, the present disclosure provides a hydrogen purification method using the pressure swing absorption apparatus 100 according to the present disclosure. The pressure swing absorption apparatus 100 includes: a plurality of absorption towers including a guard bed unit and hydrogen purification units 111 to 116, the plurality of absorption towers being connected to a raw material supply pipe 101; a vacuum pump 131 connected to the absorption towers to keep the absorption towers in a vacuum state; and a plurality of valves for opening / closing a plurality of pipes connected to the absorption towers and the vacuum pump. The hydrogen purification method includes the following steps: supplying the mixed hydrogen gas generated after ammonia decomposition to the absorption tower of the guard bed unit through the raw material supply pipe 101; selectively absorbing and removing moisture by passing the supplied mixed hydrogen gas through a first absorbent filled in the lower layer region of the absorption tower in the guard bed unit; selectively absorbing and removing ammonia by passing the moisture-free mixed hydrogen gas through a second absorbent filled in the upper layer region of the absorption tower in the guard bed unit; supplying the moisture-free and ammonia-free mixed hydrogen gas to the absorption towers 111 to 116 of the hydrogen purification unit; and selectively absorbing and removing nitrogen by passing the supplied moisture-free and ammonia-free mixed hydrogen gas through a third absorbent filled in the absorption towers 111 to 116 of the hydrogen purification unit to obtain purified hydrogen.

[0066] The step of supplying the mixed hydrogen gas may include supplying the mixed hydrogen gas discharged after removing moisture and ammonia at one absorption tower in the guard bed unit. In this case, the other absorption tower in the guard bed unit may perform a process including the following steps: a step of supplying a clean gas at a pressure higher than atmospheric pressure from the hydrogen purification units 111 to 116 after countercurrent discharge at a pressure lower than the absorption driving pressure; a raw material pressurization step; and a product pressurization step to physically absorb and remove moisture and ammonia from the mixed hydrogen gas generated after ammonia decomposition.

[0067] The supplied mixed hydrogen gas may be passed through the lower layer region of the absorption tower in the guard bed unit to selectively absorb and purify moisture, and then the mixed hydrogen gas may be passed through the upper layer region in sequence to selectively absorb and purify ammonia. In particular, the step of selectively absorbing and purifying ammonia may include absorbing and purifying ammonia such that the amount of ammonia in the mixed hydrogen gas in which moisture has been purified is less than 0.1 ppm.

[0068] According to an embodiment, the protection bed unit may include a first absorption tower to a fifth absorption tower, and each of the first absorption tower to the fifth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, and a product final pressurization step to remove moisture and ammonia from the mixed hydrogen gas supplied from the raw material supply pipe 101. And the hydrogen purification unit may include a first absorption tower to a fifth absorption tower 111 to 115, and each of the first absorption tower to the fifth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, and a product final pressurization step to remove nitrogen from the mixed hydrogen gas without moisture and ammonia supplied from the protection bed unit and improve the purity and recovery rate of the hydrogen product.

[0069] Preferably, the protection bed unit may include a first absorption tower to a fifth absorption tower, and each of the first absorption tower to the fifth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step. The hydrogen purification unit may include a first absorption tower to a fifth absorption tower 111 to 115, and each of the first absorption tower to the fifth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a third pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step.

[0070] More specifically, in the protection bed unit and the hydrogen purification units 111 to 116, except for the absorption tower supplied with the mixed hydrogen gas without ammonia, the other four absorption towers may perform the steps in a cycle in a cyclic order, that is, an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a third pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step. And in a cyclic step, the second absorption tower may perform the third pressurization step, the third absorption tower may perform the vacuum purge step, the fourth absorption tower may perform the purge supply step, and the fifth absorption tower may perform the first pressure equalization step.

[0071] According to another embodiment, the protective bed unit may include a first absorption tower to a sixth absorption tower, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step to remove moisture and ammonia from the mixed hydrogen gas supplied from the raw material supply pipe 101. The hydrogen purification unit may include a first absorption tower to a sixth absorption tower 111-116, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step to remove nitrogen from the moisture- and ammonia-free mixed hydrogen gas supplied from the protective bed unit and improve the purity and recovery rate of the hydrogen product.

[0072] Preferably, the protective bed unit may include a first absorption tower to a sixth absorption tower, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step to remove moisture and ammonia from the mixed hydrogen gas supplied from the raw material supply pipe 101. The hydrogen purification unit may include a first absorption tower to a sixth absorption tower 111-116, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a fourth pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step to remove nitrogen from the moisture- and ammonia-free mixed hydrogen gas supplied from the protective bed unit and improve the purity and recovery rate of the hydrogen product.

[0073] More preferably, the protective bed unit may include a first absorption tower to a sixth absorption tower, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge gas supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step to remove moisture and ammonia from the mixed hydrogen gas supplied from the raw material supply pipe 101. The hydrogen purification unit may include a first absorption tower to a sixth absorption tower 111 to 116, and each of the first absorption tower to the sixth absorption tower may sequentially perform an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge gas supply step, a fourth pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step to remove nitrogen from the moisture- and ammonia-free mixed hydrogen gas supplied from the protective bed unit and improve the purity and recovery rate of the hydrogen product.

[0074] The step of supplying to the absorption towers 111 to 116 of the hydrogen purification unit may include supplying the ammonia-purified mixed hydrogen gas to one of the absorption towers in the hydrogen purification unit.

[0075] The step of obtaining purified hydrogen after selectively absorbing nitrogen may include absorption and purification such that the amount of nitrogen in the ammonia-purified mixed hydrogen gas is less than 10 ppm.

[0076] The hydrogen purification method using the pressure swing absorption apparatus 100 may further include the following steps: capturing the obtained hydrogen in a hydrogen storage tank after the step of obtaining purified hydrogen; and circulating and supplying the hydrogen in the hydrogen storage tank for the cleaning step of another absorption tower and the product pressurization steps of the protective bed unit and the hydrogen purification unit 111 to 116.

[0077] Each of the plurality of absorption towers including the protective bed unit and the hydrogen purification unit 111 to 116 may repeatedly perform the hydrogen purification process on the supplied mixed hydrogen gas in a periodic manner after a cycle of the process of absorbing and purifying moisture, ammonia, and nitrogen.

[0078] The method may further include the following steps: regenerating the first absorbent and the second absorbent of the protective bed unit by supplying the exhaust gas discharged from the absorption towers 111 to 116 of the hydrogen purification unit as a purge gas to the absorption tower of the protective bed unit that has performed the countercurrent discharge step. In this case, the exhaust gas stream separately discharged from the hydrogen product stream may be continuously discharged to continuously supply a heat source for heating the ammonia decomposition apparatus.

[0079] The process of removing moisture, ammonia, and nitrogen using the pressure change absorption apparatus 100 according to the present disclosure can be performed as follows by a plurality of absorption towers including a guard bed unit and a hydrogen purification unit.

[0080] According to an embodiment, each of the absorption towers 121 to 125 of the guard bed unit and each of the absorption towers 111 to 115 of the hydrogen purification unit can perform an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a third pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step.

[0081] Figure 1 The driving method of includes: with the first supply valve 11 connected to the first absorption tower 121 of the guard bed unit open, the mixed hydrogen gas generated after the decomposition of the raw material gas (i.e., ammonia) is supplied into the first absorption tower 121 of the guard bed unit through the raw material supply pipe 101. When the impurities (such as moisture and undecomposed ammonia) contained in the mixed hydrogen gas supplied into the first absorption tower 121 pass through the first absorbent and the second absorbent filled in the first absorption tower 111 of the guard bed unit in a multi-layer structure, the moisture and ammonia are sequentially absorbed and purified, and the remaining mixed gas including nitrogen and hydrogen is obtained. Subsequently, the mixed gas containing nitrogen and hydrogen is passed through the first absorption tower 121 of the guard bed unit, and moves through the pipe 103 in a state where the valve 11-1 is open, and then is supplied into the first absorption tower 111 in the hydrogen purification unit.

[0082] The ammonia concentration in the mixed hydrogen gas supplied into the hydrogen purification units 111 to 116 is monitored in real time to keep the ammonia concentration below 0.1 ppm. In this case, when the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit perform the absorption step, the second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit sequentially perform the first pressurization step to the product pressurization step among the plurality of steps in one cycle.

[0083] First, the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform the first pressure equalization step for countercurrent discharge through the second pressure equalization valves 24 and 54, and perform the third pressurization step using the gas supplied from the pipe 108 of the hydrogen purification unit for countercurrent pressurization. After the countercurrent pressurization, the second absorption tower 112 performs the final pressurization of the product using the high-purity hydrogen generated from the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit. For the product pressurization, the second pressure equalization valves 24 and 54 are closed and the second pressurization valve 24 is opened, and the product pressurization is performed until the absorption pressure is reached.

[0084] In this case, the third absorption tower 123 of the protection bed unit and the third absorption tower 113 of the hydrogen purification unit sequentially perform the vacuum purge step and the first pressurization step among the multiple steps in a cycle. The fourth absorption tower 124 of the protection bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform the purge supply step of supplying the required vacuum purge gas to the third absorption tower 123 and the third absorption tower 113 of the hydrogen purification unit through the pipe 106 in a state where the third vacuum purge valve 36 is open, and perform vacuum desorption through the vacuum pump pipe 102 in a state where the third countercurrent discharge valve 32 is open.

[0085] After the vacuum purge step, the third absorption tower 123 and the third absorption tower 113 of the hydrogen purification unit perform the first pressurization step through discharge via the third pressure equalization step of the fourth absorption tower 114 of the hydrogen purification unit through the valve and the pipe for hydrogen. To prevent contamination of ammonia in the hydrogen purification unit, the fourth absorption tower 124 of the protection bed unit performs the countercurrent discharge step without the third pressure equalization step to exhaust gas in a state where the fourth countercurrent discharge valve 42 is open. After the third pressure equalization step, the fourth absorption tower 114 of the hydrogen purification unit performs the countercurrent discharge step in a state where the countercurrent discharge valve 42-1 is open. After the first pressurization step, the third absorption tower 123 of the protection bed unit and the third absorption tower 113 of the hydrogen purification unit perform the second pressurization step through co-current discharge via the second pressure equalization step of the fifth absorption tower 125 of the protection bed unit and the fifth absorption tower 115 of the hydrogen purification unit, and perform it through the pipe 107 in a state where the third vacuum purge valve 36 is closed and the fourth pressure equalization valve 45 and the fifth pressure equalization valve 55 are open.

[0086] The first absorption tower 121 of the protective bed unit and the first absorption tower 111 of the hydrogen purification unit perform an absorption step. Subsequently, in a state where the first raw material supply valve 11 is closed, a co-current discharge is performed through a first pressure equalization step and a second pressure equalization step. In this case, the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit perform an absorption step in a state where the second raw material supply valve 21 is open. In a state where the first pressure equalization valve 15 and the third pressure equalization valve 35 are open, the first absorption tower 121 of the protective bed unit and the first absorption tower 111 of the hydrogen purification unit perform a first pressure equalization step to perform a counter-current discharge through the pipe 107, and the third absorption tower 123 of the protective bed unit and the third absorption tower 113 of the hydrogen purification unit perform a third pressurization step to perform a counter-current pressurization. After the first pressure equalization step, through the opening of the first pressure equalization valve 15 and the fourth pressure equalization valve 45 and the pipe 107, the first absorption tower 121 of the protective bed unit and the first absorption tower 111 of the hydrogen purification unit perform a co-current discharge through a second pressure equalization step, and the fourth absorption tower 124 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform a counter-current pressurization through a second pressurization step.

[0087] After the counter-current pressurization, the third absorption tower performs a product final pressurization step using the high-purity hydrogen generated by the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit. For product pressurization, the first pressure equalization valve 15 and the third pressure equalization valve 35 are closed and the third pressurization valve 34 is opened, and the product final pressurization step is performed until the absorption pressure is reached. In this case, the fourth absorption tower 124 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit sequentially perform a vacuum purge step and a first pressurization step among the multiple steps in a cycle. The fifth absorption tower 125 of the protective bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform a purge supply step of supplying the required vacuum purge gas to the fourth absorption tower GB-4 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit through the pipe 106 in a state where the fourth vacuum purge valve 46 and the fifth vacuum purge valve 56 are open, and perform a vacuum desorption through the vacuum pump pipe 102 in a state where the fourth counter-current discharge valve 42 is open.

[0088] After the vacuum purge step, the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform the first pressurization step by co-current discharge through the third pressure equalization step of the fifth absorption tower 115 of the hydrogen purification unit via valves and pipes. To prevent contamination of ammonia in the hydrogen purification unit, the fifth absorption tower 125 of the guard bed unit performs a counter-current discharge step without the third pressure equalization step to exhaust gas with the fifth counter-current discharge valve 52 open. After the third pressure equalization step, the fifth absorption tower 115 of the hydrogen purification unit performs a counter-current discharge step with the fifth counter-current discharge valve 52-1 open.

[0089] After the first pressurization step, the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform the second pressurization step by co-current discharge through the second pressure equalization step of the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit, and it is performed through the pipe 107 with the fourth vacuum purge valve 46 closed and the first pressure equalization valve 15 and the fourth pressure equalization valve 45 open.

[0090] The second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit perform an absorption step, and then perform a co-current discharge through the first pressure equalization step and the second pressure equalization step with the second raw material supply valve 21 closed. In this case, the third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit perform an absorption step with the third raw material supply valve 31 open. With the second pressure equalization valve 25 and the fourth pressure equalization valve 45 open, the second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit perform the first pressure equalization step to perform a counter-current discharge through the pipe 107, and the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform the third pressurization step to perform a counter-current pressurization.

[0091] After the first pressure equalization step, the second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit perform a co-current discharge through the opening of the second pressure equalization valve 25 and the fifth pressure equalization valve 55 and the pipe 107 through the second pressure equalization step, and the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform a counter-current discharge through the second pressurization step. After the counter-current pressurization, the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform a product final pressurization step using the high-purity hydrogen generated from the third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit.

[0092] For product pressurization, the second pressure equalization valve 25 and the fifth pressure equalization valve 55 are closed and the fourth pressurization valve 44 is opened, and the product final pressurization step is performed until the absorption pressure is reached. In this case, the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit sequentially perform the vacuum purge step and the first pressurization step among the multiple steps in one cycle. The first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit perform the purge supply step of supplying the required vacuum purge gas to the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit through the pipe 106 with the first vacuum purge valve 16 and the fifth vacuum purge valve 56 opened, and perform vacuum desorption through the vacuum pump pipe 102 with the fifth countercurrent discharge valve 52 opened.

[0093] After the vacuum purge step, the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform the first pressurization step through co-current discharge by the third pressure equalization step of the first absorption tower 111 of the hydrogen purification unit via the valve and the pipe. To prevent contamination of ammonia in the hydrogen purification unit, the first absorption tower 121 of the guard bed unit performs the countercurrent discharge step without the third pressure equalization step for discharging in the state where the first countercurrent discharge valve 12 is opened. After the third pressure equalization step, the first absorption tower 111 of the hydrogen purification unit performs the countercurrent discharge step in the state where the first countercurrent discharge valve 12-1 is opened. After the first pressurization step, the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform the second pressurization step through co-current discharge by the second pressure equalization step of the second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit, and perform it through the pipe 107 in the state where the fifth vacuum purge valve 56 is closed and the second pressure equalization valve 25 and the fifth pressure equalization valve 55 are opened.

[0094] The third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit perform the absorption step, and then perform co-current discharge through the first pressure equalization step and the second pressure equalization step in the state where the third raw material supply valve 31 is closed. In this case, the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform the absorption step in the state where the fourth raw material supply valve 41 is opened. In the state where the third pressure equalization valve 35 and the fifth pressure equalization valve 55 are opened, the third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit perform the first pressure equalization step for co-current discharge through the pipe 107, and the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform the third pressurization step for countercurrent pressurization.

[0095] After the first pressure equalization step, the third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit perform a co-current discharge through the opening of the first pressure equalization valve 15 and the third pressure equalization valve 35 and through the pipe 107 by the second pressure equalization step, and the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit perform a counter-current discharge by the second pressurization step.

[0096] After counter-current pressurization by the third pressurization step, the fifth absorption tower 125 of the guard bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform a product final pressurization step using high-purity hydrogen generated from the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit. For product pressurization, the first pressure equalization valve 15 and the third pressure equalization valve 35 are closed and the fifth pressurization valve 54 is opened, and the product final pressurization step is performed until the absorption pressure is reached. In this case, the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit sequentially perform a vacuum purge step and a first pressurization step among multiple steps in a cycle. The second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit perform a purge supply step of supplying the required vacuum purge gas to the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit through the pipe 106 with the first vacuum purge valve 16 and the second vacuum purge valve 26 opened, and perform vacuum desorption through the vacuum pump pipe 102 with the first counter-current discharge valve 12 opened.

[0097] After the vacuum purge step, the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit perform the first pressurization step through co-current discharge through the third pressure equalization step of absorbing and purifying the second adsorption tower 112 of the hydrogen purification unit via valves and pipes. To prevent contamination of ammonia in the hydrogen purification unit, the second absorption tower 122 of the guard bed unit performs a counter-current discharge step without the third pressure equalization step to perform discharge with the second counter-current discharge valve 22 opened.

[0098] After the third pressure equalization step, the second absorption tower 112 of the hydrogen purification unit performs a counter-current discharge step with the second counter-current discharge valve 22-1 opened. After the first pressurization step, the first absorption tower 121 of the guard bed unit and the first absorption tower 111 of the hydrogen purification unit perform the second pressurization step through co-current discharge through the second pressure equalization step of the third absorption tower 123 of the guard bed unit and the third absorption tower 113 of the hydrogen purification unit, and perform it through the pipe 107 with the first vacuum purge valve 16 closed and the first pressure equalization valve 15 and the third pressure equalization valve 35 opened.

[0099] The fourth absorption tower 124 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform an absorption step, and then perform a co-current discharge through a first pressure equalization step and a second pressure equalization step with the fourth raw material supply valve 41 closed. In this case, the fifth absorption tower 125 of the protective bed unit and the fifth absorption tower 115 of the hydrogen purification unit perform an absorption step with the fifth raw material supply valve 51 open. With the first pressure equalization valve 15 and the fourth pressure equalization valve 45 open, the fourth absorption tower 124 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform a first pressure equalization step to perform a co-current discharge through the pipe 107, and the first absorption tower 121 of the protective bed unit and the first absorption tower 111 of the hydrogen purification unit perform a third pressurization step to perform a counter-current pressurization.

[0100] After the first pressure equalization step, the fourth absorption tower 124 of the protective bed unit and the fourth absorption tower 114 of the hydrogen purification unit perform a co-current discharge through the opening of the second pressure equalization valve 25 and the fourth pressure equalization valve 45 and the pipe 107 through the second pressure equalization step, and the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit perform a second pressurization step in a counter-current flow. After the counter-current pressurization, the first absorption tower 121 of the protective bed unit and the first absorption tower 111 of the hydrogen purification unit perform a product final pressurization step using the high-purity hydrogen generated from the fifth absorption tower 125 of the protective bed unit and the fifth absorption tower 115 of the hydrogen purification unit. For the product pressurization, the pressurization valves 45 and 25 are closed and the first pressurization valve 14 is opened, and the product final pressurization step is performed until the absorption pressure is reached. In this case, the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit sequentially perform a vacuum purge step and a first pressurization step among the multiple steps in a cycle.

[0101] The third absorption tower 123 of the protective bed unit and the third absorption tower 113 of the hydrogen purification unit perform a purge supply step of supplying the required vacuum purge gas to the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit through the pipe 106 with the second vacuum purge valve 26 and the third vacuum purge valve 36 open, and perform a vacuum desorption through the vacuum pump pipe 102 with the second counter-current discharge valve 22 open. After the vacuum purge step, the second absorption tower 122 of the protective bed unit and the second absorption tower 112 of the hydrogen purification unit perform a first pressurization step through a co-current discharge through a third pressure equalization step of the third absorption tower 113 of the hydrogen purification unit via valves and pipes.

[0102] To prevent contamination of ammonia in the hydrogen purification unit, the third absorption tower 123 of the guard bed unit performs a countercurrent discharge step without a third pressure equalization step to perform discharge in a state where the third countercurrent discharge valve 32 is open. After the third pressure equalization step, the third absorption tower 113 of the hydrogen purification unit performs a countercurrent discharge step in a state where the third countercurrent discharge valve 32-1 is open. After the first pressurization step, the second absorption tower 122 of the guard bed unit and the second absorption tower 112 of the hydrogen purification unit perform a second pressurization step by co-current discharge through the second pressure equalization step of the fourth absorption tower 124 of the guard bed unit and the fourth absorption tower 114 of the hydrogen purification unit, and are performed through the pipe 107 in a state where the second vacuum purge valve 26 is closed and the second pressure equalization valve 25 and the fourth pressure equalization valve 45 are open.

[0103] After one cycle is completed, each absorption tower 121-125 of the guard bed unit and each absorption tower 111-115 of the hydrogen purification unit are continuously driven by performing the same processes as one cycle, and the process includes an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a third pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step.

[0104] As described above, the hydrogen purification method using the pressure swing absorption apparatus 100 of the present disclosure can physically absorb impurities (such as moisture (H 2 O), ammonia (NH 3 ), and nitrogen (N 2 )) contained in the mixed hydrogen gas generated after ammonia decomposition to an extremely small amount or less than an extremely small amount, to achieve high-purity hydrogen purification, and improve the selective absorption of moisture, ammonia, and nitrogen, thereby maximizing the hydrogen recovery rate and productivity. In addition, the initial investment cost is low, and when only the pressure swing absorption process is applied, the temperature swing absorption process is not introduced, so the need for a heat source for regeneration can be eliminated, thereby reducing the operating cost.

[0105] Hereinafter, the present disclosure will be described in more detail based on embodiments, but the present disclosure is not limited to the following embodiments.

[0106] Example 1: Hydrogen purification using the pressure swing absorption apparatus 100 including a five-bed guard bed unit and absorption towers of a hydrogen purification unit

[0107] A process for purifying hydrogen from a mixed gas containing 74.775 vol% of hydrogen, 24.925 vol% of nitrogen, and 3000 ppm of ammonia is performed using the pressure swing absorption apparatus 100, which includes a guard bed unit in which five absorption towers are arranged in parallel and a hydrogen purification unit in which five absorption towers are arranged in parallel.

[0108] 8 wt% of silica gel as the first absorbent capable of absorbing moisture is filled in the lower regions of the first to fifth absorption towers in the guard bed unit, and 15 wt% of activated carbon impregnated with 5 wt% of magnesium as the second absorbent capable of absorbing ammonia is filled in the upper regions of the first to fifth absorption towers to form a multi-layer structure. Additionally, each of the first to fifth absorption towers in the hydrogen purification unit is filled with zeolite CaX capable of absorbing nitrogen. Further, the raw material gas supply pressure is 5.5 atmospheres. The process cycles of the guard bed unit and the hydrogen purification unit are maintained in the same manner, and the start pressures of the countercurrent discharge steps for the guard bed unit and the hydrogen purification unit are 0.8 barg (bar) and 0.5 barg, respectively.

[0109] Each absorption tower of the five-bed guard bed unit is continuously driven by performing an absorption step, a first pressure equalization step, a second pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step, and each absorption tower of the hydrogen purification unit is continuously driven by performing an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step. In this case, the raw material gas throughput is 22.00 NL / min.

[0110] The results of purifying hydrogen using the pressure swing absorption apparatus 100 are measured. The purity of the purified hydrogen is 99.999%, and the hydrogen recovery rate is 86.7%.

[0111] Example 2: Hydrogen purification using the pressure swing absorption apparatus 100-1 including a six-bed guard bed unit and absorption towers of a hydrogen purification unit

[0112] A process for purifying hydrogen from a mixed gas containing 74.775 vol% of hydrogen, 24.925 vol% of nitrogen, and 3000 ppm of ammonia is performed using the pressure swing absorption apparatus 100-1, which includes a guard bed unit in which six absorption towers are arranged in parallel and a hydrogen purification unit in which six absorption towers are arranged in parallel.

[0113] The lower regions of the first to sixth absorption towers in the protective bed unit are filled with 8 wt% silica gel as the first absorbent capable of absorbing moisture, and the upper regions of the first to sixth absorption towers are filled with 15 wt% activated carbon impregnated with 5 wt% magnesium as the second absorbent capable of absorbing ammonia to form a multi-layer structure. Additionally, each of the first to sixth absorption towers in the hydrogen purification unit is filled with zeolite CaX capable of absorbing nitrogen. Further, the raw material gas supply pressure is 5.5 atmospheres. The process cycles of the protective bed unit and the hydrogen purification unit are maintained in the same manner, and the starting pressures of the countercurrent discharge steps for the protective bed unit and the hydrogen purification unit are 0.8 barg and 0.5 barg, respectively.

[0114] Each absorption tower GB1 - GB6 of the six-bed protective bed unit is continuously driven by performing an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step, and each absorption tower 111 - 116 of the hydrogen purification unit is continuously driven by performing an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge supply step, a fourth pressure equalization step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, a fourth pressurization step, and a product final pressurization step. In this case, the raw material gas throughput is 22.00 NL / min.

[0115] The results of purifying hydrogen using the pressure swing absorption apparatus 100 - 1 were measured. The purity of the purified hydrogen was 99.999%, and the hydrogen recovery rate was 87.414%.

[0116] [Detailed Description of Main Components]

[0117] 100, 100 - 1: Pressure swing absorption apparatus

[0118] 101: Raw material supply pipe

[0119] 102 - 108: Multiple pipes

[0120] 111 - 116: The first to sixth absorption towers of the hydrogen purification unit

[0121] 121 - 126: The first to sixth absorption towers of the protective bed unit

[0122] 131: Vacuum pump

[0123] 11, 21, 31, 41, 51, 61: The first to sixth raw material supply valves

[0124] 11-1, 21-1, 31-1, 41-1, 51-1, 61-1: Outlet valves of the first to sixth protection bed units

[0125] 12, 22, 32, 42, 52, 62: Countercurrent discharge valves of the first to sixth protection bed units

[0126] 12-1, 22-1, 32-1, 42-1, 52-1, 62-1: Countercurrent discharge valves of the first to sixth hydrogen purification units

[0127] 13, 23, 33, 43, 53, 63: First to sixth product generation valves

[0128] 14, 24, 34, 44, 54, 64: First to sixth pressurizing valves

[0129] 15, 25, 35, 45, 55, 65: First to sixth pressure equalizing valves

[0130] 16, 26, 36, 46, 56, 66: First to sixth vacuum purging valves

Claims

1. A pressure swing absorption device for hydrogen purification from ammonia decomposition, comprising: a plurality of absorption towers, the plurality of absorption towers including a guard bed unit and a hydrogen purification unit, the plurality of absorption towers being connected to a raw material supply pipe; a vacuum pump, the vacuum pump being connected to the absorption tower to keep the absorption tower in a vacuum state; and a plurality of valves, the plurality of valves opening / closing a plurality of pipes connected to the absorption tower and the vacuum pump, wherein, the guard bed unit is provided at the bottom of the hydrogen purification unit, and the absorption tower in the guard bed unit is filled with a first absorbent and a second absorbent in a multi-layer structure to selectively absorb and remove moisture and ammonia contained in the mixed hydrogen gas generated after ammonia decomposition supplied through the raw material supply pipe, and wherein, the hydrogen purification unit is provided at the top of the guard bed unit, and the absorption tower in the hydrogen purification unit is filled with a third absorbent to selectively absorb and remove nitrogen contained in the mixed hydrogen gas free of moisture and ammonia from the guard bed unit.

2. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the guard bed unit and the hydrogen purification unit are connected in series, and two or more absorption tower groups each including the guard bed unit and the hydrogen purification unit connected in series are arranged in parallel.

3. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the lowest pressure of the absorption tower in the guard bed unit is maintained at not less than 1 / 4 of the raw material supply pressure.

4. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the first absorbent is filled in the lower layer region of the absorption tower in the guard bed unit, and is at least one selected from the group consisting of first activated alumina capable of removing moisture, silica gel, alumina silica gel, and zeolite.

5. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the content of the first absorbent relative to the second absorbent is 1 wt% to 70 wt%.

6. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the second absorbent is filled in the upper layer region of the absorption tower in the guard bed unit, and is at least one selected from the group consisting of metal-impregnated activated carbon capable of removing ammonia, silica gel, alumina silica gel, zeolite, and second activated alumina.

7. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 6, wherein, the metal-impregnated activated carbon is activated carbon impregnated with at least one metal selected from the group consisting of Mg, Ca, Mn, and Cu.

8. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, the content of the second absorbent relative to the first absorbent is 30 wt% to 99 wt%.

9. The pressure swing absorption device for hydrogen purification from ammonia decomposition according to claim 1, wherein, The third absorbent is at least one selected from the group consisting of zeolite NaA, zeolite CaA, zeolite CaNaA, zeolite LiX, zeolite LiNaX, zeolite LiCaX, zeolite LiNaCaX, zeolite NaX, zeolite CaX, zeolite CaNaX, and zeolite KX.

10. The pressure swing absorption apparatus for hydrogen purification from ammonia decomposition according to claim 1, wherein, the lowest pressure of the absorption tower in the guard bed unit is maintained at not less than 1 / 3 to 2 / 5 of the raw material supply pressure, wherein the first absorbent is filled in the lower layer region of the absorption tower in the guard bed unit and is the first activated alumina or silica gel capable of removing moisture, wherein the first absorbent is filled in the absorption tower of the guard bed unit in an amount of 10 wt% to 35 wt% relative to the second absorbent, wherein the second absorbent is filled in the upper layer region of the absorption tower in the guard bed unit and is metal-impregnated activated carbon capable of removing ammonia, wherein the second absorbent is filled in the absorption tower of the guard bed unit in an amount of 65 wt% to 90 wt% relative to the first absorbent, wherein the metal-impregnated activated carbon is magnesium (Mg)-impregnated activated carbon or calcium (Ca)-impregnated activated carbon, wherein the metal impregnation amount in the metal-impregnated activated carbon is 1 wt% to 8 wt%, and wherein the third absorbent is zeolite LiX, zeolite CaX, or a mixture of zeolite LiX and zeolite CaX.

11. A hydrogen purification method using the pressure swing absorption apparatus according to claim 1, the pressure swing absorption apparatus comprising: the plurality of absorption towers, the plurality of absorption towers including the guard bed unit and the hydrogen purification unit, the plurality of absorption towers being connected to the raw material supply pipe; the vacuum pump, the vacuum pump being connected to the absorption tower to keep the absorption tower in a vacuum state; and the plurality of valves, the plurality of valves opening / closing the plurality of pipes connected to the absorption tower and the vacuum pump, the hydrogen purification method comprising: supplying the mixed hydrogen gas generated after ammonia decomposition to the absorption tower of the guard bed unit through the raw material supply pipe; selectively absorbing and removing moisture by passing the supplied mixed hydrogen gas through the first absorbent filled in the lower layer region of the absorption tower in the guard bed unit; selectively absorbing and removing ammonia by passing the moisture-free mixed hydrogen gas through the second absorbent filled in the upper layer region of the absorption tower in the guard bed unit; supplying the moisture-free and ammonia-free mixed hydrogen gas to the absorption tower of the hydrogen purification unit; and selectively absorbing and removing nitrogen by passing the supplied moisture-free and ammonia-free mixed hydrogen gas through the third absorbent filled in the absorption tower in the hydrogen purification unit to obtain purified hydrogen.

12. The hydrogen purification method using the pressure swing absorption apparatus according to claim 11, wherein, The selectively absorbing and removing ammonia includes: absorbing and removing ammonia such that the amount of ammonia in the hydrogen mixture without moisture is less than 0.1 ppm, and wherein, the selectively absorbing and removing nitrogen to obtain purified hydrogen includes: absorbing and removing nitrogen such that the amount of nitrogen in the hydrogen mixture without ammonia is less than 10 ppm.

13. The hydrogen purification method using a pressure swing absorption apparatus according to claim 11, wherein, the guard bed unit includes a first absorption tower to a fifth absorption tower, and each of the first absorption tower to the fifth absorption tower of the guard bed unit sequentially performs an absorption step, a first pressure equalization step, a second pressure equalization step, a purge gas supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, and a product final pressurization step to remove moisture and ammonia from the hydrogen mixture supplied from the raw material supply pipe, and wherein, the hydrogen purification unit includes a first absorption tower to a fifth absorption tower, and each of the first absorption tower to the fifth absorption tower of the hydrogen purification unit sequentially performs an absorption step, a first pressure equalization step, a second pressure equalization step, a purge gas supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, and a product final pressurization step to remove nitrogen from the hydrogen mixture without moisture and ammonia supplied from the guard bed unit and improve the purity and recovery rate of the hydrogen product.

14. The hydrogen purification method using a pressure swing absorption apparatus according to claim 11, wherein, the guard bed unit includes a first absorption tower to a sixth absorption tower, and each of the first absorption tower to the sixth absorption tower of the guard bed unit sequentially performs an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge gas supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step to remove moisture and ammonia from the hydrogen mixture supplied from the raw material supply pipe, and wherein, the hydrogen purification unit includes a first absorption tower to a sixth absorption tower, and each of the first absorption tower to the sixth absorption tower of the hydrogen purification unit sequentially performs an absorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge gas supply step, a countercurrent discharge step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a product final pressurization step to remove nitrogen from the hydrogen mixture without moisture and ammonia supplied from the guard bed unit and improve the purity and recovery rate of the hydrogen product.

15. The hydrogen purification method using a pressure swing absorption apparatus according to claim 13 or 14, further includes: regenerating the first absorbent and the second absorbent of the guard bed unit by supplying the exhaust gas discharged from the absorption tower of the hydrogen purification unit as a purge gas to the absorption tower of the guard bed unit that has performed the countercurrent discharge step.

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