Refining apparatus and method

Abstract

To provide a lower-cost method for producing hydrogen from ammonia by simplifying the whole apparatus in removing ammonia and nitrogen from hydrogen.SOLUTION: A purification apparatus comprises a PSA device 5 which has multiple adsorption cylinders filled with an adsorbent for adsorbing and removing impurities of ammonia and nitrogen gas from a raw hydrogen gas and which continuously purifies hydrogen gas. The PSA device 5 performs adsorption separation in each adsorption cylinder by repeating a pressurization process, an adsorption process, an equalization process, a decompression process, a regeneration process, and an equalization process in this order. The adsorbent for adsorbing and removing the impurities is filled with a first adsorbent 101 for adsorbing and removing ammonia and a second adsorbent 103 for adsorbing and removing nitrogen gas, respectively, in this order from an inlet side of the raw hydrogen gas. A heat exchange part 102 is provided between the first adsorbent 101 and the second adsorbent 103.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a purification apparatus and a purification method, and more particularly to a purification apparatus and a purification method for continuously purifying hydrogen gas using a PSA device. [Background technology]

[0002] The use of hydrogen gas as a future automobile fuel is currently being promoted. However, hydrogen gas requires ultra-low temperatures to be liquefied, and it can only be transported at high pressure at room temperature, making it difficult to transport in large quantities. Therefore, a method has been considered in the past in which hydrogen is reacted with nitrogen to produce ammonia for transport, and the ammonia is then decomposed at the point of use to generate hydrogen gas for use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-177615 A [Patent Document 2] JP 2017-104778 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that ammonia decomposes when heated under a catalyst, generating hydrogen and nitrogen. However, the decomposition gas contains not only hydrogen gas and nitrogen gas as decomposition products, but also undecomposed ammonia and methane that was originally contained in the ammonia. Since high purity is required for the hydrogen gas used as fuel for FCVs, it is necessary to remove nitrogen gas and ammonia contained in the decomposed hydrogen gas to low concentrations.

[0005] To be used as fuel for FCVs, ammonia must be removed to 0.2 ppm or less, and nitrogen gas must be removed to 100 ppm or less. Conventionally, this removal has been carried out separately, with ammonia being removed using a zeolite heat regeneration type TSA (temperature swing adsorption) device, and nitrogen gas being removed using a PSA (pressure swing adsorption) device (see Patent Documents 1 and 2), which creates the problem that the entire device becomes complicated and expensive (see Figure 4).

[0006] In addition, ammonia has a strong adsorption power to adsorbents, and it cannot be sufficiently desorbed from the adsorbent by simply depressurizing or evacuating the PSA unit. Therefore, when the PSA unit is operated for a long period of time, ammonia accumulates in the adsorbent, and the accumulated ammonia then gradually leaks into the refined hydrogen gas, which is an issue.

[0007] In addition, when ammonia or nitrogen is adsorbed and removed, the heat of adsorption is large, so the gas temperature rises, which reduces the adsorption capacity.In addition, when ammonia or nitrogen is desorbed during regeneration of the adsorbent, heat of desorption (cold heat of desorption) is generated, which reduces the gas temperature and leads to insufficient regeneration of the adsorbent.

[0008] In view of the above, an object of the present invention is to simplify the entire apparatus for removing ammonia and nitrogen from raw material hydrogen gas decomposed from ammonia, thereby reducing the cost of producing hydrogen. [Means for solving the problem]

[0009] The first aspect of the present invention is a purification apparatus having a plurality of adsorption columns filled with an adsorbent for adsorbing and removing ammonia and nitrogen gas impurities from raw hydrogen gas, and equipped with a PSA apparatus for continuously purifying hydrogen gas, the PSA apparatus comprising, in each adsorption column, a pressurizing step of introducing raw hydrogen gas into the adsorption column, b an adsorption step of adsorbing and removing the impurities from the raw hydrogen gas, c a pressure equalization step of reducing the pressure inside the adsorption column to the same pressure as the other adsorption columns after the adsorption step is completed, d a degassing step of discharging gas inside the adsorption column at a constant flow rate, a pressure equalization step of evacuating the adsorption cylinder and introducing hydrogen gas for regeneration into the adsorption cylinder to regenerate the adsorbent; and f after completion of the regeneration step, the pressure equalization step of pressurizing the adsorption cylinder to the same pressure as the other adsorption cylinders is repeated in order from a pressure equalization step to f for adsorption and separation. The adsorbents for adsorbing and removing impurities are filled in the order of a first adsorbent for adsorbing and removing ammonia and a second adsorbent for adsorbing and removing nitrogen gas from the raw hydrogen gas inlet side, and a gas separator is provided between the first adsorbent and the second adsorbent. , so as to be in contact with the inner peripheral surface of the outer wall of the adsorption cylinder. The present invention is characterized by the provision of a heat exchange section.

[0010] A second aspect of the present invention is the method according to the first aspect of the present invention, characterized in that the raw material hydrogen gas is generated by decomposing ammonia using a catalyst.

[0011] A third aspect of the present invention is the above-mentioned first or second aspect, wherein the first adsorbent is activated alumina.

[0012] A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the second adsorbent is zeolite.

[0013] The fifth aspect of the present invention is any one of the first to fourth aspects of the present invention, The hydrogen gas for regeneration is hydrogen gas from which the impurities have been adsorbed and removed in the adsorption step, A part of the regenerating hydrogen gas is introduced into the heat exchange section.

[0014] The sixth aspect of the present invention is any one of the first to fifth aspects of the present invention, characterized in that the PSA apparatus has three or more adsorption columns, and when the adsorption process is performed in the first column, the depressurization process is performed in the second column, and the regeneration process is performed in any one of the third column and subsequent columns.

[0015] A seventh aspect of the present invention is a method for continuously purifying hydrogen gas by a PSA apparatus having a plurality of adsorption columns filled with an adsorbent that adsorbs and removes ammonia and nitrogen gas impurities from a raw hydrogen gas, wherein the PSA apparatus performs adsorption and separation in each adsorption column by sequentially repeating steps a to f, the steps being: a) a pressurizing step of introducing raw hydrogen gas into the adsorption column; b) an adsorption step of adsorbing and removing the impurities from the raw hydrogen gas; c) a pressure equalizing step of reducing the pressure inside the adsorption column to the same pressure as the other adsorption columns after the adsorption step is completed; d) a depressurizing step of discharging gas inside the adsorption column at a constant flow rate; e) a regeneration step of evacuating the adsorption column and introducing hydrogen gas for regeneration into the adsorption column to regenerate the adsorbent; and f) a pressure equalizing step of pressurizing the inside of the adsorption column to the same pressure as the other adsorption columns after the regeneration step is completed. In the adsorption step, the raw hydrogen gas is brought into contact with a first adsorbent to remove ammonia, and then , provided so as to be in contact with the inner peripheral surface of the outer wall of the adsorption cylinder The adsorption heat is removed by passing the adsorbent through a heat exchange section, and then the adsorbent is brought into contact with a second adsorbent to remove the nitrogen gas.

[0016] An eighth aspect of the present invention is the method according to the seventh aspect, characterized in that the raw material hydrogen gas is generated by decomposing ammonia using a catalyst.

[0017] A ninth aspect of the present invention is the above seventh or eighth aspect, characterized in that the first adsorbent is activated alumina.

[0018] A tenth aspect of the present invention is characterized in that, in any one of the seventh to ninth aspects, the second adsorbent is zeolite.

[0019] The eleventh aspect of the present invention is any one of the seventh to tenth aspects of the present invention, The hydrogen gas for regeneration is hydrogen gas from which the impurities have been adsorbed and removed in the adsorption step,In the regeneration step, a part of the regeneration hydrogen gas is introduced into the heat exchange section.

[0020] The twelfth aspect of the present invention is any one of the seventh to eleventh aspects of the present invention, characterized in that the PSA apparatus has three or more adsorption columns, and when an adsorption process is performed in a first column, a depressurization process is performed in a second column, and a regeneration process is performed in any one of the third and subsequent columns. Effect of the Invention

[0021] According to the purification device and purification method of the present invention, it is possible to simplify the entire device and reduce the cost of producing hydrogen by removing ammonia and nitrogen from hydrogen. In addition, the obtained hydrogen gas is of high purity and can be used as fuel for FCVs. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing the configuration of a hydrogen gas production apparatus used in the purification method of the present invention. [Diagram 2] FIG. 1 is a system diagram showing one embodiment of a PSA apparatus in the purification method of the present invention. [Diagram 3] FIG. 2 is a diagram showing the structure of an adsorption column in the PSA apparatus. [Figure 4] FIG. 1 is a diagram showing the configuration of a conventional hydrogen gas production device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Fig. 1 is a schematic diagram showing an example of the configuration of a hydrogen gas production apparatus 1 (purification apparatus) used in the purification method of the present invention. As shown in Fig. 1, the hydrogen gas production apparatus 1 includes an ammonia supply source 2, an ammonia decomposition apparatus 3, a boost pump 4, a PSA apparatus 5, an air supply source 6, a boost pump 8, and lines L1 to L7. It differs from the prior art shown in Fig. 4 in that it includes only the PSA apparatus 5 without including a TSA apparatus. Each component of the hydrogen gas production apparatus 1 will be described below.

[0024] The ammonia supply source 2 supplies ammonia to the ammonia decomposer 3 via a line L1. One end of the line L1 is connected to the ammonia supply source 2, and the other end is connected to the ammonia decomposer 3. Ammonia is supplied to the ammonia supply source 2 by a known method such as a cylinder, a tank, a truck, or a pipeline.

[0025] The ammonia decomposition device 3 decomposes ammonia supplied from the ammonia supply source 2 into nitrogen gas and hydrogen gas by an ammonia decomposition reaction shown in the following formula (1). This decomposition reaction takes place in a reaction chamber 7 of the ammonia decomposition device 3. This hydrogen gas is supplied as raw hydrogen gas to the PSA device 5 described later, but it contains impurities such as nitrogen gas, ammonia residue, and methane gas. 2NH3 → N2+3H2 (1)

[0026] The ammonia decomposition device 3 is not particularly limited and may be a known reactor. For example, the ammonia decomposition device performs the ammonia decomposition reaction shown in the above formula (1) by providing heat such as heat of combustion. Therefore, the ammonia decomposition device 3 stably supplies heat to the reaction chamber 7. The reaction chamber 7 is filled with an ammonia decomposition catalyst. The ammonia decomposition catalyst promotes the ammonia decomposition reaction shown in the above formula (1). Examples of the ammonia decomposition catalyst include known catalysts such as nickel and ruthenium.

[0027] One end of the line L2 is connected to the ammonia decomposer 3, and the other end is connected to a boost pump 4. The boost pump 4 is a pump that increases the pressure of the raw hydrogen gas (ammonia decomposition gas) supplied from the ammonia decomposer 3 via the line L2.

[0028] One end of the line L3 is connected to the boost pump 4, and the other end is connected to the PSA unit 5. The PSA unit 5 is a unit that purifies the raw hydrogen gas supplied through the line L3, and removes impurities from the raw hydrogen gas to purify the hydrogen gas.

[0029] The line L4 is a line for taking out purified hydrogen gas from the adsorption tower in the adsorption step of the PSA apparatus 5.

[0030] The line L5 is a line for extracting off-gas discharged from the adsorption column in the regeneration step or depressurization step of the PSA unit 5. One end of the line L5 is connected to the PSA unit 5, and the other end is connected to the boost pump 8.

[0031] One end of the line L6 is connected to the boost pump 8, and the other end is connected to the ammonia decomposer 3. The off-gas whose pressure has been increased by the boost pump 8 is introduced into the ammonia decomposer 3 via the line L6 and is reused as fuel for the ammonia decomposer 3.

[0032] One end of the line L7 is connected to the air supply source 6, and the other end is connected to the line L6. The air supply source 6 delivers air to the line L6 via the line L7, and mixes the oxygen component in the air into the off-gas, thereby making the off-gas a practical fuel for the ammonia decomposition unit 3.

[0033] Fig. 2 is a system diagram showing one embodiment of the PSA apparatus 5. As shown in Fig. 2, the PSA apparatus 5 is roughly configured to include a raw material hydrogen gas (ammonia decomposition gas) supply line 10, an off-gas discharge line 20, a depressurization line 30, a hydrogen gas recovery line 40, a regeneration gas introduction line 50, a pressure equalization line 60, first to third adsorption columns 70A to 70C, a vacuum pump 22, a first tank 23, a boost pump 24, a second tank 25, valves Va1 to Va6, Vb1 to Vb6, Vc1 to Vc6, a valve V, and a return line 80.

[0034] One end of the raw hydrogen gas supply line 10 is connected to a raw hydrogen gas supply source 12, and the other end is branched into first to third supply branch lines 11A, 11B, and 11C. The raw hydrogen gas supply source 12 is continued from the line L3 in Fig. 1, and raw hydrogen gas pressurized by a boost pump 4 is supplied to it.

[0035] The first supply branch line 11A is connected to a connecting pipe 71A that is connected to the lower end of the first adsorption column 70A. The first supply branch line 11A supplies the source gas to the lower end of the first adsorption column 70A via the connecting pipe 71A. The second supply branch line 11B is connected to a connecting pipe 71B that is connected to the lower end of the second adsorption column 70B. The second supply branch line 11B supplies the source gas to the lower end of the second adsorption column 70B via the connecting pipe 71B. The third supply branch line 11C is connected to a connecting pipe 71C that is connected to the lower end of the third adsorption column 70C. The third supply branch line 11C supplies the source gas to the lower end of the third adsorption column 70C via the connecting pipe 71C.

[0036] Offgas discharged from each adsorption cylinder during regeneration passes through the offgas discharge line 20. One end of the offgas discharge line 20 is branched into first to third discharge branch lines 21A, 21B, and 21C, and the other end is connected to the line L5 in Fig. 1 to reuse the offgas as fuel.

[0037] The first discharge branch line 21A is connected to a connecting pipe 71 A. The first discharge branch line 21A passes through the connecting pipe 71A the off-gas discharged from the lower end of the first adsorption column 70A. The second discharge branch line 21B is connected to the connecting pipe 71B. The second discharge branch line 21B passes through the connecting pipe 71B the off-gas discharged from the lower end of the second adsorption column 70B. The third discharge branch line 21C is connected to a connecting pipe 71C. The off-gas discharged from the lower end of the third adsorption column 70C passes through the third discharge branch line 21C via the connecting pipe 71C.

[0038] In this manner, in the PSA apparatus 5 according to this embodiment, the first to third discharge branch lines 21A-21C are connected to the lower ends of the respective adsorption columns. When each adsorption column is in the regeneration process, the upper end of each adsorption column is the primary side, and the lower end of each adsorption column is the secondary side (the off-gas discharge port side).

[0039] In the off-gas discharge line 20, a vacuum pump 22, a first tank 23, a booster pump 24, and a second tank 25 are provided in series in this order toward the secondary side.

[0040] The vacuum pump 22 is provided in a portion of the off-gas discharge line 20 located between the branching positions of the first to third discharge branch lines 21A to 21C and the first tank 23. The vacuum pump 22 draws air into the first to third adsorption columns 70A to 70C via the off-gas discharge line 20, thereby directing the off-gas to the first tank 23. The vacuum pump 22 can also evacuate the insides of the adsorption columns 70A to 70C.

[0041] The first tank 23 is provided in the off-gas discharge line 20. Specifically, the first tank 23 is provided in a portion of the off-gas discharge line 20 that is located between the vacuum pump 22 and the boost pump 24. The first tank 23 is a tank that temporarily stores the off-gas discharged from the first to third adsorption columns 70A-70C via the off-gas discharge line 20. The first tank 23 temporarily stores the off-gas and then supplies it to the second tank 25.

[0042] The boost pump 24 is provided in a portion of the off-gas discharge line 20 that is located between the first tank 23 and the second tank 25. The boost pump 24 is an example of a boosting means that boosts the pressure of the off-gas temporarily stored in the first tank 23 via the off-gas discharge line 20. The off-gas pressurized by the boost pump 24 is pumped from the first tank 23 to the second tank 25.

[0043] The second tank 25 is provided in a portion of the off-gas discharge line 20 on the secondary side of the first tank 23. The second tank 25 stores the off-gas supplied via the first tank 23 while maintaining the pressure at a constant level. The second tank 25 also supplies the off-gas to the line L5 to use it as fuel gas for the ammonia decomposition unit 3.

[0044] During operation of the PSA device 5, the pressure in the first tank 23 is preferably maintained at approximately atmospheric pressure. In particular, while at least one of the adsorption towers is performing at least one of a depressurization step and a regeneration step, the pressure in the first tank 23 is preferably maintained at approximately atmospheric pressure. In this case, the back pressure, which is the pressure on the secondary side of the vacuum pump 22, is maintained at approximately atmospheric pressure, and the vacuum pump 22 operates normally to suck the inside of each adsorption tower, which makes it easier for impurities in the adsorption towers to be desorbed, which is preferable.

[0045] From the viewpoint of making it easier to maintain the pressure inside the first tank 23 at approximately atmospheric pressure, it is preferable that the volume of the first tank 23 be larger than the volume of the second tank 25. Moreover, the first tank 23 and the second tank 25 are preferably airtight to prevent hydrogen gas from leaking outside the respective tanks. The pressure in the second tank is preferably maintained higher than the pressure in the first tank 23, since this makes it easier to store the off-gas while maintaining it at a constant pressure.

[0046] The depressurization line 30 has one end branched into first to third depressurization branch lines 31A, 31B, and 31C, and the other end connected to the first tank 23.

[0047] The first depressurization branch line 31A is connected to a connecting pipe 71A. The first depressurization branch line 31A passes through the connecting pipe 71A the off-gas discharged from the lower end of the first adsorption column 70A. The second depressurization branch line 31B is connected to the connecting pipe 71B. The second depressurization branch line 31B passes through the connecting pipe 71B the off-gas discharged from the lower end of the second adsorption column 70B. The third depressurization branch line 31C is connected to a connecting pipe 71C. The off-gas discharged from the lower end of the third adsorption column 70C passes through the third depressurization branch line 31C via the connecting pipe 71C.

[0048] One end of the hydrogen gas recovery line 40 is branched into first to third recovery branch lines 41A, 41B, and 41C, and the other end is connected to the line L4 in FIG.

[0049] The first recovery branch line 41A is connected to a connecting pipe 72A. The first recovery branch line 41A recovers the purified hydrogen gas from the upper end of the first adsorption column 70A via the connecting pipe 72A. The second recovery branch line 41B is connected to the connecting pipe 72B. The second recovery branch line 41B recovers the purified hydrogen gas from the upper end of the second adsorption column 70B via the connecting pipe 72B. The third recovery branch line 41C is connected to a connecting pipe 72C. The third recovery branch line 41C recovers the purified hydrogen gas from the upper end of the third adsorption column 70C via the connecting pipe 72C.

[0050] One end of the regeneration gas introduction line 50 is branched into first to third introduction branch lines 51A, 51B, and 51C, and the other end is connected to the hydrogen gas recovery line 40 via a connection point 43.

[0051] The first inlet branch line 51A is connected to a connecting pipe 72A. The first inlet branch line 51A introduces the regeneration gas into the upper end of the first adsorption column 70A via the connecting pipe 72A. The second inlet branch line 51B is connected to a connecting pipe 72B. The second inlet branch line 51B introduces the regeneration gas into the upper end of the second adsorption column 70B via the connecting pipe 72B. The third inlet branch line 51C is connected to a connecting pipe 72C. The third inlet branch line 51C introduces the regeneration gas into the upper end of the third adsorption column 70C via the connecting pipe 72C.

[0052] The regeneration gas introduction line 50 is provided with a flow rate control valve 52 . The flow rate control valve 52 is provided in a portion of the regeneration gas introduction line 50 located between the branch positions of the first to third introduction branch lines 51A to 51C and the connection point 43. The flow rate control valve 52 controls the flow rate of the regeneration gas introduced from the hydrogen gas storage tank 42 through the connection point 43 and the regeneration gas introduction line 50 into the first to third adsorption columns 70A to 70C.

[0053] The pressure equalization line 60 has first to third pressure equalization branch lines 61A, 61B, 61C branched off so as to connect the upper ends of the first to third adsorption columns 70A to 70C. The first pressure equalizing branch line 61A is connected to a connecting pipe 72A. The second pressure equalizing branch line 61B is connected to a connecting pipe 72B. The third pressure equalizing branch line 61C is connected to a connecting pipe 72C.

[0054] The first adsorption column 70A has its lower end connected to a connecting pipe 71A and its upper end connected to a connecting pipe 72A. The second adsorption column 70B has its lower end connected to a connecting pipe 71B and its upper end connected to a connecting pipe 72B. The third adsorption column 70C has its lower end connected to a connecting pipe 71C and its upper end connected to a connecting pipe 72C.

[0055] 3 shows the structure of the first to third adsorption columns 70A to 70C. Inside each adsorption column, a first adsorbent 101, a heat exchanger 102, and a second adsorbent 103 are layered in order from the side (the lower side of the adsorption column) where raw hydrogen gas (ammonia decomposition gas) is introduced in the adsorption process.

[0056] The first adsorbent 101 is made of activated alumina and adsorbs and removes ammonia residues and the like in the raw hydrogen gas.

[0057] The heat exchanger 102 is for removing heat of adsorption generated when the first adsorbent 101 adsorbs and removes ammonia residues and the like in the adsorption process. The heat exchanger 102 is also for removing desorption cold heat generated in the second adsorbent 103 in the depressurization process and the regeneration process. The heat removed by the heat exchanger 102 is quickly released to the outer wall of the adsorption cylinder.

[0058] The second adsorbent 103 is made of zeolite and adsorbs and removes nitrogen gas and the like from the raw hydrogen gas. The first adsorbent 101 and the second adsorbent 103 remove ammonia residue, nitrogen gas, and the like from the raw hydrogen gas, thereby producing high-purity hydrogen gas.

[0059] As shown in FIG. 3, when regenerating the adsorbent, if hydrogen gas as the regeneration gas is introduced directly into the heat exchange section 102 in addition to being introduced into the second adsorbent 103, the regeneration gas is introduced directly into the first adsorbent 101, which promotes desorption of ammonia from the first adsorbent 101, which is preferable.

[0060] The valve Va1 is provided in the first supply branch line 11A. The valve Va2 is provided in the first discharge branch line 21A. The valve Va3 is provided in the first depressurization branch line 31A. The valve Va4 is provided in the first recovery branch line 41A. The valve Va5 is provided in the first introduction branch line 51A. The valve Va6 is provided in the first equalization branch line 61A.

[0061] The valve Vb1 is provided in the second supply branch line 11B. The valve Vb2 is provided in the second discharge branch line 21B. The valve Vb3 is provided in the second depressurization branch line 31B. The valve Vb4 is provided in the second recovery branch line 41B. The valve Vb5 is provided in the second introduction branch line 51B. The valve Vb6 is provided in the second equalization branch line 61B.

[0062] The valve Vc1 is provided in the third supply branch line 11C. The valve Vc2 is provided in the third discharge branch line 21C. The valve Vc3 is provided in the third depressurization branch line 31C. The valve Vc4 is provided in the third recovery branch line 41C. The valve Vc5 is provided in the third introduction branch line 51C. The valve Vc6 is provided in the third equalization branch line 61C.

[0063] The valve V is provided in the return line 80. The valve V is used when leading off-gas from the second tank 25 to the first tank 23. As the valve V, for example, a needle valve for flow rate control, a pressure regulator, or the like can be used.

[0064] The return line 80 connects the first tank 23 and the second tank 25. The return line 80 delivers the off-gas from the second tank 25 to the first tank 23.

[0065] Using the hydrogen gas purification apparatus 1 configured as above, the method for producing hydrogen from ammonia according to the present invention is carried out as follows.

[0066] The purification method of this embodiment will be specifically described below with reference to FIG. The hydrogen gas purification method of this embodiment is a purification method using the above-mentioned hydrogen gas production apparatus 1, and includes the following steps: an adsorption process in which ammonia residue, nitrogen gas, etc. are adsorbed and removed from the raw hydrogen gas decomposed by the ammonia decomposition apparatus 3 in each of the adsorption columns 70A to 70C of the PSA apparatus 5 to purify hydrogen gas; a pressure equalization process in which the pressure between the adsorption columns is equalized after the adsorption process; a depressurization process in which the pressure inside the adsorption columns is reduced and the raw hydrogen gas remaining in the adsorption columns is discharged as off-gas; a regeneration process in which hydrogen gas is introduced into the adsorption columns and the raw hydrogen gas and hydrogen gas remaining in the adsorption columns are discharged as off-gas; a pressure equalization process in which the pressure between the adsorption columns is equalized after the regeneration process; and a pressurization process in which the inside of the adsorption columns is pressurized to prepare for the adsorption process.

[0067] First, ammonia stored in an ammonia supply source 2 is introduced into an ammonia decomposition apparatus 3 via a line L1.

[0068] The raw material hydrogen gas (ammonia decomposition gas) is produced in the ammonia decomposition device 3 by the ammonia decomposition reaction shown in the following formula (1). 2NH3 → N2+3H2 (1)

[0069] The raw hydrogen gas generated in the ammonia decomposition unit 3 contains impurities such as unreacted ammonia residues and nitrogen gas that were not decomposed in the ammonia decomposition unit 3. The raw hydrogen gas containing these impurities is pumped to the PSA unit 5 via the line L2, the boost pump 4, and the line L3.

[0070] Impurities other than hydrogen gas contained in the pressure-fed raw hydrogen gas are removed by the PSA device 5, and high-purity hydrogen gas is produced. The high-purity hydrogen gas is recovered from the PSA device 5 via line L4.

[0071] In the hydrogen gas purification method of this embodiment, off-gas is discharged from the adsorption column in the depressurization step or regeneration step of the PSA unit 5 via line L5. In the regeneration step, a part of the produced hydrogen gas is introduced into the adsorption column as regeneration gas, so that the off-gas contains hydrogen gas. Therefore, air is mixed into the off-gas, and the heat generated by burning the off-gas can be used for the ammonia decomposition reaction in the ammonia decomposition unit 3. By burning the off-gas, the regeneration gas can be effectively used, and the hydrogen recovery (utilization) rate can be made substantially 100%. When the off-gas is combusted, the off-gas is pumped from line L5 through boost pump 8 and then line L6, and air is mixed in midway through line L6 from air supply source 6 through line L7.

[0072] Hereinafter, with reference to FIG. 2, each step of purifying hydrogen gas from raw hydrogen gas in the PSA device 5 of the hydrogen gas purification device 1 will be specifically described. Table 1 is a table for explaining the process of each adsorption column when removing impurities by PSA apparatus 5 in the hydrogen gas purification method of this embodiment. Each of states 1 to 9 shown in Table 1 will be explained in order below. In Table 1, the period of the colored portion indicates the state when the corresponding valve is open, and the period of the uncolored portion indicates the state when the valve is closed.

[0073] [Table 1]

[0074] As shown in Table 1, the removal of impurities by the PSA unit 5 is carried out by repeating the steps of a pressurization step, an adsorption step, a pressure equalization step, a depressurization step, a regeneration step, and a pressure equalization step in each adsorption column. First, the following explanation will be given by taking as an example a case in which, in State 1, a pressurization process is being performed in the first adsorption column 70A, a regeneration process is being performed in the second adsorption column 70B, and a depressurization process is being performed in the third adsorption column 70C.

[0075] In state 1, valves Va1, Vb2 and Vc3 are open, and the other valves are closed.

[0076] At this time, the lower end of the first adsorption column 70A is connected to the raw material gas supply line 10. Therefore, in state 1, raw material hydrogen gas is supplied to the adsorbent from the lower end of the first adsorption column 70A via the raw material gas supply line 10, the first supply branch line 11A, the valve Va1, and the connecting pipe 71A, and the inside of the first adsorption column 70A is pressurized. That is, in state 1, a pressurization step is being performed in the first adsorption column 70A.

[0077] At this time, the lower end of the second adsorption column 70B is connected to the off-gas discharge line 20. Therefore, in state 1, impurities are desorbed from the adsorbent to which the impurities have been adsorbed by vacuum evacuation by the vacuum pump 22 via the connecting pipe 71B, the valve Vb2, the second discharge branch line 21B, and the off-gas discharge line 20, and the off-gas is discharged to the first tank 23, thereby regenerating the inside of the second adsorption column 70B. That is, in state 1, a regeneration process is being performed in the second adsorption column 70B.

[0078] At this time, the lower end of the third adsorption column 70C is connected to the depressurization line 30. Therefore, in State 1, off-gas is discharged to the first tank 23 via the connecting pipe 71C, the valve Vc3, the third depressurization branch line 31C, and the depressurization line 30, and the inside of the third adsorption column 70C is depressurized. That is, in State 1, a depressurization step is being performed in the third adsorption column 70C.

[0079] Next, in order to bring the PSA apparatus 5 into state 2 in Table 1 above, valves Va4 and Vb5 are opened while valves Va1, Vb2, and Vc3 are kept open.

[0080] By opening valve Va4 while keeping valve Va1 open, first adsorption column 70A begins adsorption separation with the adsorbent from a pressurized state, and the purified hydrogen gas is connected to line L4 in Fig. 1 via connecting pipe 72A, valve Va4, first recovery branch line 41A, and hydrogen gas recovery line 40. That is, in state 2, the adsorption process is performed in first adsorption column 70A.

[0081] Furthermore, by opening valve Vb5 while keeping valve Vb2 open, the second adsorption column 70B performs the regeneration process following state 1 in a state in which hydrogen gas as a regeneration gas is introduced into the second adsorption column 70B via the regeneration gas introduction line 50, the second introduction branch line 51B, valve Vb5, and the connecting pipe 72B. That is, in state 2, the regeneration process continues to be performed in the second adsorption column 70B.

[0082] Furthermore, by keeping valve Vc3 open, the depressurization step is carried out in third adsorption column 70C in state 2 following state 1.

[0083] Next, in order for the PSA apparatus 5 to reach state 3 in Table 1 above, valves Va1, Va4, Vb2, Vb5 and Vc3 are closed and valves Va6 and Vb6 are opened.

[0084] By closing valves Va1 and Va4 and opening valve Va6, high-pressure hydrogen gas is discharged from the first adsorption tower 70A from the pressurized state after the end of the adsorption process via the connecting pipe 72A, the first pressure equalization branch line 61A, valve Va6, and the pressure equalization line 60.

[0085] Furthermore, by closing valves Vb2 and Vb5 and opening valve Vb6, the second adsorption column 70B is connected to the pressure equalization line 60 via the connecting pipe 72B, the second pressure equalization branch line 61B, and valve Vb6 after the regeneration step is completed, and high-pressure hydrogen gas discharged from the first adsorption column 70A is introduced into the second adsorption column 70B. When the high-pressure hydrogen gas is discharged from the first adsorption column 70A, the pressure in the first adsorption column 70A is reduced until it becomes equal to the pressure in the second adsorption column 70B. At the same time, the pressure in the second adsorption column 70B is increased until it becomes equal to the pressure in the first adsorption column 70A. That is, in state 3, the pressure equalization step is performed in the first adsorption column 70A and the second adsorption column 70B.

[0086] Furthermore, by closing valve Vc3, all valves in the third adsorption column 70C are closed, so that in State 3, the state after the depressurization step in State 2 is maintained, and no steps are progressing.

[0087] Next, in order to bring the PSA apparatus 5 into state 4 in Table 1 above, valves Va6 and Vb6 are closed and valves Va3, Vb1 and Vc2 are opened.

[0088] By closing valve Va6 and opening valve Va3, first adsorption column 70A discharges off-gas to first tank 23 via connecting pipe 71A, valve Va3, first depressurization branch line 31A, and depressurization line 30. That is, in state 4, a depressurization step is being performed in first adsorption column 70A.

[0089] Furthermore, by closing valve Vb6 and opening valve Vb1, the source gas is supplied to the adsorbent from the lower end of second adsorption column 70B via source gas supply line 10, second supply branch line 11B, valve Vb1, and connecting pipe 71B, and the inside of first adsorption column 70B is pressurized. That is, in state 4, a pressurization step is being performed in second adsorption column 70B.

[0090] Furthermore, by opening valve Vc2, impurities are desorbed from third adsorption column 70C by evacuation by vacuum pump 22 via connecting pipe 71C, valve Vc2, third exhaust branch line 21C, and off-gas exhaust line 20, and off-gas is discharged to first tank 23, thereby regenerating the inside of third adsorption column 70C. That is, in state 4, a regeneration process is being performed in third adsorption column 70C.

[0091] Next, in order to bring the PSA apparatus 5 into state 5 in Table 1 above, valves Va3, Vb1, and Vc2 are left open, while valves Vb4 and Vc5 are opened. By keeping valve Va3 open, the depressurization step is performed in first adsorption column 70A in state 5 following state 4.

[0092] Furthermore, by opening valve Vb4 while keeping valve Vb1 open, second adsorption column 70B starts adsorption separation with the adsorbent from a pressurized state, and the purified hydrogen gas is connected to line L4 in Fig. 1 via connecting pipe 72B, valve Vb4, second recovery branch line 41B, and hydrogen gas recovery line 40. That is, in state 5, the adsorption process is performed in second adsorption column 70B.

[0093] Furthermore, by opening valve Vc5 while keeping valve Vc2 open, the third adsorption column 70C continues to perform the regeneration process in a state in which hydrogen gas as the regeneration gas is introduced into the third adsorption column 70C via the regeneration gas introduction line 50, the third introduction branch line 51C, valve Vc5, and the connecting pipe 72C. That is, in state 5, the regeneration process continues to be performed in the third adsorption column 70C.

[0094] Next, in order for the PSA apparatus 5 to reach state 6 in Table 1 above, valves Va3, Vb1, Vb4, Vc2, and Vc5 are closed, and valves Vb6 and Vc6 are opened.

[0095] By closing valve Va3, all valves in the first adsorption column 70A are closed, so that in State 6, the state after the depressurization step in State 5 is maintained, and no steps are progressing.

[0096] Furthermore, by closing valves Vb1 and Vb4 and opening valve Vb6, high-pressure hydrogen gas is discharged from the second adsorption column 70B, which is in a pressurized state after the end of the adsorption process, via the connecting pipe 72B, the second pressure equalization branch line 61B, valve Vb6, and the pressure equalization line 60.

[0097] Furthermore, by closing valves Vc2 and Vc5 and opening valve Vc6, the third adsorption column 70C communicates with the pressure equalization line 60 via the connecting pipe 72C, the third pressure equalization branch line 61C, and valve Vc6 after the regeneration step is completed, and high-pressure hydrogen gas discharged from the second adsorption column 70B is introduced into the third adsorption column 70C. When the high-pressure hydrogen gas is discharged from the second adsorption column 70B, the pressure in the second adsorption column 70B is reduced until it becomes equal to the pressure in the third adsorption column 70C. At the same time, the pressure in the third adsorption column 70C is increased until it becomes equal to the pressure in the second adsorption column 70B. That is, in state 6, the pressure equalization step is performed in the second adsorption column 70B and the third adsorption column 70C.

[0098] Next, in order to bring the PSA apparatus 5 into state 7 in Table 1 above, valves Vb6 and Vc6 are closed and valves Va2, Vb3 and Vc1 are opened.

[0099] By opening the valve Va2, the first adsorption column 70A, which contains the adsorbent with the impurities adsorbed therein, is evacuated by the vacuum pump 22 via the connecting pipe 71A, the valve Va2, the first exhaust branch line 21A, and the off-gas exhaust line 20, thereby desorbing the impurities, and the off-gas is discharged into the first tank 23, thereby regenerating the inside of the first adsorption column 70A. That is, in state 7, the regeneration process is being carried out in the first adsorption column 70A.

[0100] Furthermore, by closing valve Vb6 and opening valve Vb3, the second adsorption column 70B discharges off-gas to the first tank 23 via the connecting pipe 71B, valve Vb3, second depressurization branch line 31B, and depressurization line 30. That is, in state 7, the depressurization step is being performed in the second adsorption column 70B.

[0101] Furthermore, by closing valve Vc6 and opening valve Vc1, the raw hydrogen gas is supplied to the adsorbent from the lower end of third adsorption column 70C via raw gas supply line 10, third supply branch line 11C, valve Vc1, and connecting pipe 71C, and the inside of third adsorption column 70C is pressurized. That is, in state 7, a pressurization step is being performed in third adsorption column 70C.

[0102] Next, in order to bring the PSA apparatus 5 into state 8 in Table 1 above, valves Va2, Vb3, and Vc1 are left open, while valves Va5 and Vc4 are opened.

[0103] By opening valve Va5 while keeping valve Va2 open, the first adsorption column 70A continues to perform the regeneration process in a state in which hydrogen gas as a regeneration gas is introduced into the first adsorption column 70A via the regeneration gas introduction line 50, the first introduction branch line 51A, valve Va5, and the connecting pipe 72A. That is, in state 8, the regeneration process continues to be performed in the first adsorption column 70A.

[0104] Furthermore, by keeping valve Vb3 open, the depressurization step is performed in second adsorption column 70B in state 8 following state 7.

[0105] Furthermore, by opening valve Vc4 while leaving valve Vc1 open, third adsorption column 70C begins adsorption separation using the adsorbent from a pressurized state, and the purified hydrogen gas passes through connecting pipe 72C, valve Vc4, third recovery branch line 41C, and hydrogen gas recovery line 40 and is stored in hydrogen gas storage tank 42. That is, in state 8, the adsorption process is performed in third adsorption column 70C.

[0106] Next, in order for the PSA apparatus 5 to reach state 9 in Table 1 above, valves Va2, Va5, Vb3, Vc1, and Vc4 are closed, and valves Va6 and Vc6 are opened.

[0107] By closing valve Vb3, all valves in the second adsorption column 70B are closed, so that in State 9, the state after the depressurization step in State 8 is maintained, and no steps are progressing.

[0108] In addition, by closing valve Vc1 and opening valve Vc6, high-pressure hydrogen gas is discharged from the third adsorption column 70C, which is in a pressurized state after the adsorption process is completed, via the connecting pipe 72C, the third pressure equalization branch line 61C, valve Vc6, and the pressure equalization line 60.

[0109] Furthermore, by closing valves Va2 and Va5 and opening valve Va6, the first adsorption column 70A is connected to the pressure equalization line 60 via the connecting pipe 72A, the first pressure equalization branch line 61A, and valve Va6 after the regeneration step is completed, and high-pressure hydrogen gas discharged from the third adsorption column 70C is introduced into the first adsorption column 70A. When the high-pressure hydrogen gas is discharged from the third adsorption column 70C, the pressure in the third adsorption column 70C is reduced until it becomes equal to the pressure in the first adsorption column 70A. At the same time, the pressure in the first adsorption column 70A is increased until it becomes equal to the pressure in the third adsorption column 70C. That is, in state 9, the pressure equalization step is performed in the third adsorption column 70C and the first adsorption column 70A.

[0110] By repeating the above states 1 to 9, impurities are removed in the PSA apparatus 5 of this embodiment by repeating the pressurizing step, adsorption step, pressure equalization step, depressurization step, regeneration step, and pressure equalization step in each adsorption column. Here, the depressurization step and the regeneration step are separate steps, so that the gas adsorbed to the adsorbent in the adsorption column is removed by a change in the pressure inside the column during depressurization, and is removed by vacuum suction by a vacuum pump and regeneration of the adsorbent by regeneration gas during regeneration.

[0111] Therefore, by carrying out both steps as separate steps, the gas adsorbed in the adsorbent can be efficiently desorbed from the adsorbent and sufficiently removed. In addition, by having two steps, the depressurization step and the regeneration step, the regeneration time of the adsorbent can be extended, so that the gas adsorbed in the adsorbent can be sufficiently removed.

[0112] Next, among the above steps, the flow of the raw material hydrogen gas in each adsorption column in the adsorption step will be described below. 3, the raw material gas introduced into each adsorption column from its lower end is first adsorbed and removed of ammonia residue by the first adsorbent 101. During this adsorption and removal, heat of adsorption is generated, and the temperature of the raw material hydrogen gas rises temporarily, but this heat of adsorption is removed by the heat exchanger 102, so that the temperature of the raw material hydrogen gas is lowered. Thereafter, nitrogen gas and the like are adsorbed and removed from the raw material hydrogen gas by the second adsorbent 103, and the raw material hydrogen gas becomes purified hydrogen gas, which is then recovered.

[0113] Next, among the above steps, the gas flow in each adsorption column in the depressurization step and the regeneration step will be described below. First, in the depressurization step, the gas filled in the adsorption column is released from the feed gas introduction side (the lower end of the adsorption column) in the above-mentioned adsorption step.

[0114] Next, in the regeneration step, vacuum suction is performed from the inlet side of the raw gas, and at the same time, a regeneration gas is introduced from the outlet side (the upper end of the adsorption column) of the raw gas in the adsorption step, and the nitrogen gas, ammonia, etc. adsorbed to each adsorbent are removed and discharged as off-gas. Here, during the regeneration process, it is more preferable to introduce the regeneration gas not only from the outlet side of the raw hydrogen gas but also from the heat exchange section 102, since the regeneration gas directly reaches the ammonia adsorbed in the first adsorbent 101, and desorption of ammonia in the first adsorbent 101 is promoted.

[0115] In the depressurization step and regeneration step, when the adsorbed nitrogen gas and the like are desorbed in the second adsorbent 103, heat of desorption (cold heat of desorption) is generated due to the desorption, and the temperature of the off-gas drops temporarily. However, the cold heat of desorption is removed in the heat exchange section 102. Therefore, the temperature of the off-gas returns to the original temperature in the heat exchange section 102, and the subsequent desorption of ammonia in the first adsorbent 101 is promoted. Since ammonia is generally a substance that is difficult to desorb from an adsorbent, promoting desorption in this manner is more preferable because it prevents a decrease in the purification capacity of the PSA apparatus due to the accumulation of ammonia.

[0116] [Experimental Example] Hydrogen was purified from ammonia using the purification apparatus of the present invention shown in Figure 1. The compositions of the gases flowing through the lines L1 to L5 in the purification apparatus are shown in Table 2. The gas in line L4 represents the hydrogen gas after purification in the PSA apparatus.

[0117] [Table 2]

[0118] [Comparative Example] Hydrogen was purified from ammonia using the conventional purification apparatus shown in Figure 4. The composition of the gas flowing through each line L1 to L5 in the purification apparatus is shown in Table 3. The gas in line L4 represents the hydrogen gas after purification in the PSA apparatus.

[0119] [Table 3]

[0120] From the above results, the purification apparatus and purification method of the present invention are performed using an apparatus having only a PSA apparatus without a TSA apparatus, and therefore the entire apparatus is significantly simplified compared to the conventional technology. Therefore, the cost of hydrogen production can be reduced. In addition, the obtained hydrogen gas has a high purity of 99.97% or more, contains less than 0.1 ppm of ammonia, and less than 100 ppm of nitrogen gas, and can be used as a fuel for FCVs.

[0121] In the above embodiment, the PSA device 5 is a three-tube type, but the number of adsorption tubes is not necessarily three, and can be changed appropriately depending on the situation in which the PSA treatment is performed. In the above embodiment, the first adsorbent 101 is activated alumina, and the second adsorbent 103 is zeolite, but other types of adsorbents may be used as long as they can remove ammonia residue and nitrogen gas. For example, activated carbon, silica gel, resin adsorbents, etc. can be used as the first adsorbent 101. As the second adsorbent 103, X-type zeolite is particularly used, and zeolites called Li-X and Ca-X, which are ion-exchanged with lithium or calcium, are the best, and Ca-A, which is ion-exchanged with calcium, is also suitable. However, by using activated alumina as the adsorbent for ammonia, it is possible to adsorb and remove ammonia, and to sufficiently remove the adsorbed ammonia by depressurization regeneration and vacuum regeneration.

[0122] The heat exchanger 102 for removing the heat of adsorption and desorption in the adsorption cylinder may be made of metal balls, metal honeycomb structure material, metal mesh, metal wool, etc., as long as it can quickly release the heat and cold of the gas inside the adsorption cylinder to the outer wall of the adsorption tower. Examples of metals include aluminum, gold, silver, copper, stainless steel, iron, etc., as long as they have good thermal conductivity. [Explanation of symbols]

[0123] DESCRIPTION OF SYMBOLS 1 Hydrogen gas purification apparatus, 2 Ammonia supply source, 3 Ammonia decomposition apparatus, 4 Booster pump, 5 PSA apparatus, 6 Air supply source, 7 Reaction chamber, 8 Booster pump, 10 Raw hydrogen gas supply line, 20 Off-gas discharge line, 22 Vacuum pump, 23 First tank, 24 Booster pump, 25 Second tank, 30 Depressurization line, 40 Hydrogen gas recovery line, 50 Regeneration gas introduction line, 60 Pressure equalization line, 70 Adsorption column, 80 Return line, 101 First adsorbent, 102 Heat exchange section, 103 Second adsorbent

Claims

1. A purification apparatus having a plurality of adsorption columns filled with an adsorbent that adsorbs and removes ammonia and nitrogen gas impurities from a raw hydrogen gas, and a PSA apparatus that continuously purifies hydrogen gas, The PSA apparatus includes, in each adsorption column: a. A pressurizing step of introducing raw hydrogen gas into an adsorption column; b. An adsorption step of adsorbing and removing the impurities from the raw hydrogen gas; c) A pressure equalization step of reducing the pressure inside the adsorption column to the same pressure as the other adsorption columns after the adsorption step is completed; d. A depressurization step in which the gas in the adsorption column is discharged at a constant flow rate; e. A regeneration step in which the adsorption cylinder is evacuated to a vacuum and hydrogen gas for regeneration is introduced into the adsorption cylinder to regenerate the adsorbent; f. After the regeneration process is completed, the pressure equalization process is performed to pressurize the inside of the adsorption column to the same pressure as the other adsorption columns. The steps a to f are repeated in order to perform adsorption and separation. the adsorbents for adsorbing and removing impurities are filled in the first adsorbent for adsorbing and removing ammonia and the second adsorbent for adsorbing and removing nitrogen gas in this order from the inlet side of the raw material hydrogen gas; a heat exchange section provided between the first adsorbent and the second adsorbent so as to be in contact with an inner circumferential surface of an outer wall of the adsorption column.

2. 2. The refining apparatus according to claim 1, wherein the raw hydrogen gas is generated by decomposing ammonia using a catalyst.

3. 3. The purification apparatus according to claim 1, wherein the first adsorbent is activated alumina.

4. 4. The purification apparatus according to claim 1, wherein the second adsorbent is a zeolite.

5. The hydrogen gas for regeneration is hydrogen gas from which impurities have been adsorbed and removed in the adsorption process, and a purification apparatus as described in any one of claims 1 to 4 is characterized in that a portion of the hydrogen gas for regeneration is introduced into the heat exchange section.

6. 6. The purification apparatus according to claim 1, wherein the PSA apparatus has three or more adsorption columns, and while an adsorption step is performed in a first column, a depressurization step is performed in a second column, and a regeneration step is performed in any one of the third and subsequent columns.

7. A method for continuously purifying hydrogen gas using a PSA apparatus having a plurality of adsorption columns filled with an adsorbent that adsorbs and removes ammonia and nitrogen gas impurities from a raw hydrogen gas, comprising the steps of: The PSA apparatus includes, in each adsorption column: a. A pressurizing step of introducing raw hydrogen gas into an adsorption column; b. An adsorption step of adsorbing and removing the impurities from the raw hydrogen gas; c) A pressure equalization step of reducing the pressure inside the adsorption column to the same pressure as the other adsorption columns after the adsorption step is completed; d. A depressurization step in which the gas in the adsorption column is discharged at a constant flow rate; e. A regeneration step in which the adsorption cylinder is evacuated to a vacuum and hydrogen gas for regeneration is introduced into the adsorption cylinder to regenerate the adsorbent; f. After the regeneration process is completed, the pressure equalization process is performed to pressurize the inside of the adsorption column to the same pressure as the other adsorption columns. Steps a to f are repeated in order to perform adsorption and separation. ammonia is removed by contacting the raw hydrogen gas with a first adsorbent in the adsorption step, heat of adsorption is removed by passing the raw hydrogen gas through a heat exchange section provided in contact with the inner peripheral surface of the outer wall of the adsorption column, and nitrogen gas is removed by contacting the raw hydrogen gas with a second adsorbent.

8. 8. The method according to claim 7, wherein the raw hydrogen gas is generated by decomposing ammonia using a catalyst.

9. 9. The purification method according to claim 7, wherein the first adsorbent is activated alumina.

10. 10. The method according to claim 7, wherein the second adsorbent is a zeolite.

11. A purification method described in any one of claims 7 to 10, characterized in that the hydrogen gas for regeneration is hydrogen gas from which the impurities have been adsorbed and removed in the adsorption process, and in the regeneration process, a portion of the hydrogen gas for regeneration is introduced into the heat exchange section.

12. 12. The purification method according to claim 7, wherein the PSA apparatus has three or more adsorption columns, and while an adsorption step is performed in a first column, a depressurization step is performed in a second column, and a regeneration step is performed in any one of the third and subsequent columns.

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