JP5568059B2 - High purity hydrogen purification method - Google Patents

Description

  The present invention relates to a method for purifying hydrogen from a hydrogen-containing gas with high purity and high recovery rate using a hydrogen recovery tower packed with a hydrogen storage alloy.

  In recent years, there is an increasing expectation for hydrogen as a fuel for fuel cells that leads to improvement of the global environment. In general, this hydrogen is obtained by reforming and reforming a hydrocarbon-containing fuel such as natural gas, naphtha, kerosene, and methanol and steam in the presence of a metal catalyst. In addition to hydrogen, the gas after the transformation contains components that are impurities for fuel for fuel cells, such as carbon monoxide, carbon dioxide, methane, and water. However, as fuel for the fuel cell, high-purity hydrogen improves power generation efficiency. As a typical method for obtaining such high-purity hydrogen, a hydrogen PSA method using a plurality of adsorption towers is known (see, for example, Patent Document 1).

  In addition to the hydrogen PSA method using an adsorption tower, a method for obtaining high-purity hydrogen has been developed (see, for example, Patent Document 2). The technique disclosed in Patent Document 2 is such that a hydrogen-containing gas is passed through a hydrogen recovery tower packed with a hydrogen storage alloy, and only hydrogen in the hydrogen-containing gas is selectively stored in the hydrogen storage alloy to be separated from the impurity gas. Then, only hydrogen stored in the hydrogen storage alloy is released from the hydrogen recovery tower to produce hydrogen (hereinafter referred to as “hydrogen storage alloy method”).

  Further, a technique that further develops the technique disclosed in Patent Document 2 has been developed (see, for example, Patent Document 3). The technique disclosed in Patent Document 3 includes a cleaning step of cleaning using a part of high-purity hydrogen obtained by purifying impurities remaining in the hydrogen recovery tower after hydrogen is stored in the hydrogen storage alloy. is there.

JP 2002-177726 A Japanese Patent Laid-Open No. 5-319822 JP 2002-338204 A

  In the hydrogen PSA method using a plurality of adsorption towers disclosed in Patent Document 1, high purity hydrogen of 99.999 volume% (hereinafter, “volume%” is simply expressed as “%”) or more is produced. However, it is necessary to have an adsorbent according to the removal components other than hydrogen, which not only increases the size of the adsorption tower, but also generates a loss of 20% or more at 80% even when the hydrogen recovery rate is high. There was a problem of doing.

  Further, in the hydrogen storage alloy method disclosed in Patent Document 2, since the hydrogen storage alloy uses the advantage that a large amount of hydrogen can be stored, the process switching cycle at the time of production is disclosed in Patent Document 1 above. The length can be increased compared to the PSA method. Therefore, the hydrogen storage alloy method has less depressurization loss at the time of switching, and the hydrogen recovery rate can be improved compared to the hydrogen PSA method. However, in this hydrogen storage alloy method, impurities remaining in the hydrogen recovery tower after hydrogen is stored in the hydrogen storage alloy are recovered together with the high purity hydrogen released from the hydrogen recovery tower in the hydrogen release step. Therefore, although the hydrogen recovery rate is improved as compared with the hydrogen PSA method, there is a problem that the purity of the recovered hydrogen is conversely lower than 99.999% or more obtained by the hydrogen PSA method.

  In addition, the hydrogen storage alloy method disclosed in Patent Document 3 has improved the problems of the hydrogen storage alloy method disclosed in Patent Document 2 (reduction in the purity of recovered hydrogen). Since a part of the purified high-purity hydrogen used is discharged out of the hydrogen recovery tower as an off-gas, the hydrogen recovery rate is conversely lower than that of the hydrogen storage alloy method disclosed in Patent Document 2 above. there were.

  An object of the present invention is to provide a high purity hydrogen purification method capable of recovering high purity hydrogen from a hydrogen-containing gas at a high recovery rate.

In order to achieve this object, the invention according to claim 1 of the present invention provides:
A hydrogen-containing gas was passed through a hydrogen recovery tower filled with a hydrogen-occlusion alloy, a first hydrogen-occlusion step of occluding the hydrogen-containing gas in the hydrogen-occlusion alloy, and the hydrogen-occlusion alloy occluded hydrogen. A first purge step for purging impurity gas remaining in the subsequent hydrogen recovery tower, a cleaning step for discharging impurities remaining in the hydrogen recovery tower after the first purge step, and after this cleaning step A high-purity hydrogen refining method comprising: a first hydrogen releasing step of releasing hydrogen stored in the first hydrogen storage step from the hydrogen recovery tower to obtain high-purity hydrogen;
A cleaning hydrogen purification tower filled with a cleaning hydrogen storage alloy having a volume smaller than the volume of the hydrogen storage alloy;
A part of the high-purity hydrogen released from the hydrogen recovery tower in the first hydrogen releasing step is passed through the cleaning hydrogen purification tower, and the hydrogen in the part of the high-purity hydrogen is further stored in the cleaning hydrogen storage. A second hydrogen storage step for storing in the alloy; a second purge step for purging the impurity gas slightly remaining in the cleaning hydrogen purification tower after storing the hydrogen in the cleaning hydrogen storage alloy; A second hydrogen releasing step of releasing hydrogen stored in the second hydrogen storage step after the second purge step to obtain cleaning hydrogen by releasing the hydrogen stored in the cleaning hydrogen purification tower;
The high purity hydrogen purification method is characterized in that the cleaning hydrogen obtained in the second hydrogen releasing step is used for discharging impurities in the cleaning step.

The invention according to claim 2 is the invention according to claim 1,
The volume of the hydrogen storage alloy for cleaning is 20% to 80% of the volume of the hydrogen storage alloy.

The invention according to claim 3 is the invention according to claim 1 or 2,
The hydrogen recovery tower has a first heating step for preheating the hydrogen storage alloy in the hydrogen recovery tower between the washing step and the first hydrogen releasing step, and the first hydrogen releasing step and the first hydrogen It has the 1st cooling process which cools in advance the hydrogen storage alloy in a hydrogen recovery tower between storage processes.

The invention according to claim 4 is the invention according to claim 1,
The hydrogen storage alloy is an AB5 hydrogen storage alloy.

The invention according to claim 5 is the invention according to claim 3,
The hydrogen storage alloy is an AB5 hydrogen storage alloy, and the hydrogen equilibrium pressure of the AB5 hydrogen storage alloy is 0.05 MPa or more and 0.3 MPa or less,
A medium flow passage for temperature control of the AB5 hydrogen storage alloy is provided inside or outside the hydrogen recovery tower,
In the first hydrogen storage step, the first purge step, the cleaning step and the first cooling step, a medium having a temperature of 0 ° C. or more and less than 40 ° C. is circulated through the medium flow path,
In the first hydrogen releasing step and the first heating step, a medium having a temperature of 40 ° C. or higher and lower than 150 ° C. is circulated through the medium flow path.

The invention according to claim 6 is the invention according to claim 1 or 2,
The cleaning hydrogen purification tower has a second heating step of preheating the cleaning hydrogen storage alloy in the cleaning hydrogen purification tower between the second purge step and the second hydrogen release step, And a second cooling step for cooling the cleaning hydrogen storage alloy in the cleaning hydrogen purification tower in advance between the hydrogen release step and the second hydrogen storage step.

The invention according to claim 7 is the invention according to claim 1,
The cleaning hydrogen storage alloy is an AB5 hydrogen storage alloy.

The invention according to claim 8 is the invention according to claim 6,
The cleaning hydrogen storage alloy is an AB5-based hydrogen storage alloy, and the hydrogen equilibrium pressure of the AB5-based hydrogen storage alloy is 0.05 MPa or more and 0.3 MPa or less,
A medium flow passage for temperature control of the AB5 hydrogen storage alloy is provided inside or outside the cleaning hydrogen purification tower,
In the second hydrogen storage step, the second purge step and the second cooling step, a medium having a temperature of 0 ° C. or more and less than 40 ° C. is circulated through the medium flow path,
In the second hydrogen releasing step and the second heating step, a medium having a temperature of 40 ° C. or higher and lower than 150 ° C. is circulated through the medium flow path.

As described above, according to the high purity hydrogen purification method of the present invention,
A hydrogen-containing gas was passed through a hydrogen recovery tower filled with a hydrogen-occlusion alloy, a first hydrogen-occlusion step of occluding the hydrogen-containing gas in the hydrogen-occlusion alloy, and the hydrogen-occlusion alloy occluded hydrogen. A first purge step for purging impurity gas remaining in the subsequent hydrogen recovery tower, a cleaning step for discharging impurities remaining in the hydrogen recovery tower after the first purge step, and after this cleaning step A high-purity hydrogen refining method comprising: a first hydrogen releasing step of releasing hydrogen stored in the first hydrogen storage step from the hydrogen recovery tower to obtain high-purity hydrogen;
A cleaning hydrogen purification tower filled with a cleaning hydrogen storage alloy having a volume smaller than the volume of the hydrogen storage alloy;
A part of the high-purity hydrogen released from the hydrogen recovery tower in the first hydrogen releasing step is passed through the cleaning hydrogen purification tower, and the hydrogen in the part of the high-purity hydrogen is further stored in the cleaning hydrogen storage. A second hydrogen storage step for storing in the alloy; a second purge step for purging the impurity gas slightly remaining in the cleaning hydrogen purification tower after storing the hydrogen in the cleaning hydrogen storage alloy; A second hydrogen releasing step of releasing hydrogen stored in the second hydrogen storage step after the second purge step to obtain cleaning hydrogen by releasing the hydrogen stored in the cleaning hydrogen purification tower;
Since the cleaning hydrogen obtained in the second hydrogen releasing step is used for discharging impurities in the cleaning step,
A high-purity hydrogen purification method that can recover high-purity hydrogen from a hydrogen-containing gas at a high recovery rate can be provided.

It is explanatory drawing which illustrates typically the outline | summary of a structure of the high purity hydrogen purification system which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an explanatory diagram schematically illustrating an outline of a configuration of a high purity hydrogen purification system according to an embodiment of the present invention.

  In FIG. 1, 1a, 1b and 1c are hydrogen recovery towers filled with a hydrogen storage alloy, 2a, 2b and 2c are media provided outside the hydrogen recovery towers 1a, 1b and 1c for temperature control of the hydrogen storage alloy. Flow path, 3 is a pressure control valve, 4, 5, 14, 15 are valves, 6 is a vacuum pump, 7, 8, 9 are mass flow controllers, 13 is a hydrogen occlusion filled in the hydrogen recovery towers 1 a, 1 b, 1 c The cleaning hydrogen purification section (11a, 11b, 11c) is composed of a cleaning hydrogen purification tower (11a, 11b, 11c) filled with a cleaning hydrogen storage alloy each having a predetermined ratio {eg, 50%} to the volume of the alloy. It is.

  Further, medium flow passages 12a, 12b, and 12c are provided outside the cleaning hydrogen purification towers 11a, 11b, and 11c, respectively, similarly to the hydrogen recovery towers 1a, 1b, and 1c.

  Line 101 is an introduction line for hydrogen-containing gas A. The line 101 and the hydrogen recovery towers 1a, 1b, and 1c are connected to each other through a valve A1, a valve B1, and a valve C1, respectively.

  The line 102 is a recovery line that obtains high-purity hydrogen from the hydrogen-containing gas A in each of the hydrogen recovery towers 1a to 1c and recovers this high-purity hydrogen (product hydrogen) C. The hydrogen recovery towers 1a to 1c and Are connected via valves A2, B2 and C2, respectively, and the recovered high-purity hydrogen (product hydrogen) C is further temporarily stored in a buffer tank (not shown) via the mass flow controller 7. .

  The line 103 is purged as off-gas B by reducing the impurity gas remaining in the hydrogen recovery towers 1a to 1c after the hydrogen storage alloy is occluded with hydrogen in each hydrogen recovery tower 1a to 1c to normal pressure or reduced pressure. It is an off-gas line. The line 103 and each of the hydrogen recovery towers 1a to 1c are connected to each other via a valve A4, a valve B4, and a valve C4, and the line 103 is connected to a valve 4 that reduces the pressure to normal pressure via a pressure control valve 3. ing. Further, the line 103 is connected to the vacuum pump 6 via the pressure control valve 3 and the valve 5 in order to further reduce the pressure as required. Further, this line 103 is provided with each of the cleaning hydrogen purification towers 11a to 11c after the cleaning hydrogen storage towers 11a, 11b, and 11c further store hydrogen in the part of the high-purity hydrogen. It is also an off-gas line for purging impurity gas slightly remaining in 11c, and is connected to each of the cleaning hydrogen purification towers 11a, 11b, 11c via a valve.

  The line 104 passes a part of the high purity hydrogen discharged from the hydrogen recovery towers 1a, 1b, and 1c via the line 102 to the mass flow controller 8, the valve PW-1A, the valve PW-1B, and the valve PW-1C. Through the cleaning hydrogen purification towers 11a, 11b, and 11c.

  The line 105 contains impurity gas slightly remaining in the cleaning hydrogen purification towers 11a, 11b, and 11c after the hydrogen in the part of the high-purity hydrogen is occluded in the cleaning hydrogen purification towers 11a, 11b, and 11c. After purging, it is discharged as cleaning hydrogen from the cleaning hydrogen purification towers 11a, 11b, and 11c through the valves PW-2A, PW-2B, PW-2C, and valve 15, respectively, and connected to the mass flow controller 9. It is a line for.

  The line 106 is a line for supplying the cleaning hydrogen supplied from the mass flow controller 9 in order to discharge impurities remaining in the hydrogen recovery towers 1a, 1b, and 1c. The line 106 and the hydrogen recovery towers 1a, 1b, and 1c are connected to each other through a valve A3, a valve B3, and a valve C3.

  Next, the operation procedure of the method for purifying high-purity hydrogen (product hydrogen) C from the hydrogen-containing gas A is concretely described together with the process of purifying cleaning hydrogen (for example, when the cleaning hydrogen purifying tower 11a is used). Explained. In the following, although only the operation procedure of the hydrogen recovery tower 1a will be described in principle, the operation is cyclic using three hydrogen recovery towers 1a to 1c as shown in the time step table of Table 1 below. Do.

  1) [Hydrogen storage step of hydrogen recovery tower 1a (hereinafter referred to as “first hydrogen storage step”, time step numbers 1 to 6)]: medium having a temperature of 0 ° C. or higher and lower than 40 ° C. in medium flow passage 2a (for example, While flowing cold water), the hydrogen-containing gas A is introduced into the hydrogen recovery tower 1a and the hydrogen in the hydrogen-containing gas A is stored in the hydrogen storage alloy (valves A2, A3: closed, valves A1, A4: open). Since the hydrogen occlusion reaction is an exothermic reaction, hydrogen occlusion is performed while flowing cold water as described above for heat removal. Thereby, since the hydrogen occlusion speed is not lowered, the hydrogen recovery rate is also improved. Moreover, when using a kind like an AB5 type | system | group hydrogen storage alloy as a hydrogen storage alloy, the hydrogen-containing gas A made into high pressure (for example, 0.9 MPa) is introduce | transduced into the hydrogen recovery tower 1a.

  2) [Purge step of the hydrogen recovery tower 1a (hereinafter referred to as “first purge step”, time step number 7)]: After the completion of the first hydrogen storage step shown in 1) above, The remaining impurity gas is purged as off-gas B via the line 103 by reducing the pressure to normal pressure or down. In addition, when making it normal pressure, valve A1, A2, A3 is closed and valve A4, the pressure control valve 3, and the valve 4 are opened. When the pressure is reduced, the valves A1, A2, A3 and the valve 4 are closed, the valve 5 is opened, the vacuum pump 6 is activated, and the pressure control valve 3 is adjusted to reduce the pressure to a predetermined pressure. During the first purge process, a second heating process in the process of purifying cleaning hydrogen, which will be described later, is performed.

  3) [Hydrogen recovery tower 1a cleaning step (time step number 8)]: After the completion of the first purging step shown in 2) above, the hydrogen recovery tower 1a using the cleaning hydrogen supplied via the line 106 is used. The impurities remaining inside are discharged (valves A1, A2, valve 4: closed, valves A3, A4, pressure control valve 3, valve 5, vacuum pump 6: opened). During this cleaning step, cleaning hydrogen is obtained in the second hydrogen releasing step in the process of purifying cleaning hydrogen, which will be described later, and the cleaning hydrogen obtained in this second hydrogen releasing step is obtained. The gas is supplied to the line 106 while controlling the mass flow controller 9 from the cleaning hydrogen purification tower 11a. That is, the cleaning process of the hydrogen recovery tower 1 a is performed using the cleaning hydrogen supplied to the line 106.

  4) [Heating step of the hydrogen recovery tower 1a (hereinafter referred to as “first heating step”, time step numbers 9, 10)]: After completion of the cleaning step shown in 3) above, the medium flow passage 2a is heated to 40 ° C. or higher. While flowing a medium lower than 150 ° C. (for example, warm water), the hydrogen storage alloy filled in the hydrogen recovery tower 1a is heated (valves A1, A2, A3: closed). As a result, the amount of heat necessary for the first hydrogen releasing step to be described later is supplied in advance, so that a sufficient hydrogen releasing speed can be quickly obtained in the hydrogen releasing step.

  5) [Hydrogen releasing step of the hydrogen recovery tower 1a (hereinafter referred to as “first hydrogen releasing step”, time step numbers 11 to 16)]: After the completion of the first heating step shown in 4) above, the medium flow path While flowing a medium (for example, warm water) of 40 ° C. or higher and lower than 150 ° C. to 2a, the hydrogen stored in the first hydrogen storage step is released from the hydrogen recovery tower 1a to obtain high purity hydrogen (valves A1, A3). , A4: closed, valve A2: open). Since the hydrogen releasing reaction is an endothermic reaction, hydrogen is released while flowing warm water as described above in order to replenish heat. Thereby, since the hydrogen release rate does not decrease, high-purity hydrogen can be obtained. As described above, since the impurities remaining in the hydrogen recovery tower 1a are previously discharged with cleaning hydrogen (corresponding to the cleaning step shown in 3) above, the high purity obtained in the first hydrogen releasing step is obtained. Hydrogen has a higher purity.

  6) [Cooling step of hydrogen recovery tower 1a (hereinafter referred to as “first cooling step”, time step numbers 17, 18)]: After the completion of the first hydrogen releasing step shown in 5) above, the medium flow passage is again formed. While flowing a medium (for example, cold water) of 0 ° C. or higher and lower than 40 ° C. through 2a, the hydrogen storage alloy filled in the hydrogen recovery tower 1a is cooled (valves A1, A2, A3, A4: closed). Thereby, in preparation for the next step (the first hydrogen storage step), necessary heat removal is performed in advance, so that a sufficient hydrogen storage rate can be quickly obtained in the first hydrogen storage step.

  By repeating the operation procedures 1) to 6), high purity hydrogen can be recovered from the hydrogen-containing gas A at a high recovery rate.

  Next, the process of purifying cleaning hydrogen will be described in detail. In the following, a method for purifying cleaning hydrogen using the cleaning hydrogen purification tower 11a will be described in principle. However, as shown in the time step table of Table 1, the operation is as follows. Perform cyclically using 3 towers of 11c.

  11) [Hydrogen storage step of cleaning hydrogen purification tower 11a (hereinafter referred to as “second hydrogen storage step”, time step numbers 11 and 12)]: Medium (0 ° C. or more and less than 40 ° C. in medium flow passage 12a) For example, a portion of the high purity hydrogen (product hydrogen) C obtained in the first hydrogen releasing step shown in 5) above is fed through the line 104 while controlling the mass flow controllers 7 and 8 while flowing cold water). The hydrogen is introduced into the hydrogen purification tower 11a, and the hydrogen in this part of high-purity hydrogen is further stored in the hydrogen storage alloy for cleaning (valve PW-2A: closed, valve PW-1A: open). Since this hydrogen occlusion reaction is also an exothermic reaction, hydrogen occlusion is performed while flowing cold water as described above for heat removal. Thereby, since the hydrogen occlusion speed is not lowered, the hydrogen recovery rate is also improved. In addition, when a cleaning hydrogen storage alloy such as an AB5 hydrogen storage alloy is used, a part of high-purity hydrogen (product hydrogen) C having a high pressure (for example, 0.9 MPa) is used for cleaning. It introduce | transduces into the hydrogen purification column 11a.

  12) [Purging step of cleaning hydrogen purification column 11a (hereinafter referred to as “second purging step”, time step number 17)]: After completion of the second hydrogen storage step shown in 11) above, cleaning hydrogen purification The impurity gas slightly remaining in the column 11a is purged as off-gas B through the valve 14 by reducing the pressure to atmospheric pressure. Thus, preparation for purifying cleaning hydrogen having higher hydrogen purity from high-purity hydrogen (product hydrogen) C is completed. When normal pressure is used, the valves PW-1A and 15 are closed and the valves PW-2A and 14 are opened. Further, during the second purge process, the first cooling process shown in 6) above is performed.

13) [Heating step of cleaning hydrogen purification tower 11a (hereinafter referred to as "second heating step", time step number 7)]: After the completion of the second purging step shown in 12) above, While flowing a medium (for example, warm water) of 40 ° C. or higher and lower than 150 ° C., the cleaning hydrogen purification tower 11a
The cleaning hydrogen storage alloy filled therein is heated (valves PW-1A, PW-2A: closed). As a result, the amount of heat necessary for the second hydrogen releasing step to be described later is supplied in advance, so that a sufficient hydrogen releasing speed can be quickly obtained in the hydrogen releasing step.

  14) [Hydrogen releasing step of cleaning hydrogen purification column 11a (hereinafter referred to as “second hydrogen releasing step”, time step number 8)]: After the completion of the second heating step shown in 13) above, the medium flow path While flowing a medium of 40 ° C. or higher and lower than 150 ° C. (for example, warm water) through 12a, the hydrogen stored in the second hydrogen storage step is released from the cleaning hydrogen purification column 11a to obtain cleaning hydrogen (valve PW). -1A, valve 14: closed, valve PW-2A, valve 15: open). Since this hydrogen releasing reaction is also an endothermic reaction, hydrogen is released while flowing warm water as described above in order to replenish heat. As a result, the hydrogen release rate does not decrease, so that an appropriate cleaning hydrogen can be obtained.

  15) [Cooling step of cleaning hydrogen purification tower 11a (hereinafter referred to as “second cooling step”, time step numbers 9, 10)]: After completion of the second hydrogen releasing step shown in 14) above, the medium again While flowing a medium (for example, cold water) of 0 ° C. or higher and lower than 40 ° C. through the flow passage 12a, the cleaning hydrogen storage alloy filled in the cleaning hydrogen purification tower 11a is cooled (valves PW-1A, PW-2A: Closed). Thereby, in preparation for the next step (the second hydrogen storage step), necessary heat removal is performed in advance, so that a sufficient hydrogen storage rate can be quickly obtained in the second hydrogen storage step.

  By repeating the operation procedures 11) to 15) above, it is possible to purify hydrogen for cleaning with higher hydrogen purity from high-purity hydrogen (product hydrogen) C.

  In the high-purity hydrogen purification method in the high-purity hydrogen purification system according to the present embodiment, the hydrogen storage process, purge process, cleaning process, heating process, hydrogen release process and cooling are performed in one cycle for one hydrogen recovery tower. Although an example in which a hydrogen storage step, a purge step, a heating step, a hydrogen release step and a cooling step are provided in one cycle for one cleaning hydrogen purification tower has been described, it is not necessarily limited to this. It is not something. That is, the heating process and the cooling process are respectively included in one cycle for the one hydrogen recovery tower and in one cycle for one cleaning hydrogen purification tower. In the technical idea of the present invention, It is not necessarily an essential configuration requirement. However, it is more preferable to provide these steps because the heating and cooling steps provide the above-described further effects.

  In the high-purity hydrogen purification method in the high-purity hydrogen purification system according to the present embodiment, the example in which the three hydrogen recovery towers 1a to 1c and the three cleaning hydrogen purification towers 11a to 11c are described has been described. It is not limited to. For example, even a configuration provided with one hydrogen recovery tower and one cleaning hydrogen purification tower satisfies the technical idea of the present invention. However, by adopting the configuration of the present embodiment (the configuration including the three hydrogen recovery towers 1a to 1c and the three cleaning hydrogen purification towers 11a to 11c), continuous and improved production efficiency of high-purity hydrogen purification To preferred.

Further, when impurities such as CO ₂ and N ₂ are contained in the hydrogen-containing gas A, if an AB5 type hydrogen storage alloy is adopted as the hydrogen storage alloy and the cleaning hydrogen storage alloy, the AB2 type hydrogen storage alloy and the like can be used. Compared to other hydrogen storage alloys, it is more resistant to impurities such as CO ₂ and N _2, and it is possible to provide durability as a system, which is preferable. In particular, it is important for a hydrogen storage alloy filled in a hydrogen recovery tower. The hydrogen equilibrium pressure of the AB5-based hydrogen storage alloy is 0.05 MPa or more and 0.3 MPa or less, and a medium flow passage for controlling the temperature of the AB5-based hydrogen storage alloy is provided inside or outside the hydrogen recovery tower. In the process, the purge process, the cleaning process, and the cooling process, a medium (hereinafter referred to as “refrigerant”) of 0 ° C. or more and less than 40 ° C. is circulated through the medium flow path, and in the hydrogen release process and the heating process, the medium It is preferable to circulate a medium (hereinafter referred to as “heat medium”) having a temperature of 40 ° C. or higher and lower than 150 ° C. in the flow path. This is because if the temperature of the refrigerant is too lower than this range, energy for producing the refrigerant is required and energy efficiency is lowered. On the other hand, if it is higher than this range, a sufficient hydrogen storage rate cannot be obtained. On the other hand, if the temperature of the heat medium is lower than this range, a sufficient hydrogen release rate cannot be obtained. On the other hand, if it is higher than this range, energy for producing the heat medium is required, and the energy efficiency is lowered. Considering energy efficiency and cost, a more preferable refrigerant temperature is 20 ° C. to 40 ° C., and a more preferable heat medium temperature is 60 ° C. to 80 ° C. that can be recovered by low-grade exhaust heat that is not normally used. The above is also true for the cleaning hydrogen storage alloy filled in the cleaning hydrogen purification tower.

  In this embodiment, the volume of the cleaning hydrogen storage alloy filled in the cleaning hydrogen purification towers 11a, 11b, and 11c is equal to the volume of the hydrogen storage alloy filled in the hydrogen recovery towers 1a, 1b, and 1c. On the other hand, the case of 50% has been described as an example, but it is not necessarily limited thereto. For example, the volume of the hydrogen storage alloy for cleaning is preferably 20% to 80% of the volume of the hydrogen storage alloy. By setting such a ratio, it is possible to control a small amount of flow rate using a mass flow controller or the like while securing an appropriate amount as hydrogen for cleaning in the above-described cleaning step of the hydrogen recovery tower, and the first It is also possible to reduce the loss of high purity hydrogen obtained in the hydrogen releasing step (hydrogen releasing step of the hydrogen recovery tower). Also, as long as the ratio is ensured, the system is stopped in the evening of the previous day and restarted the next morning. {At this point, the first hydrogen release step (hydrogen recovery step of the hydrogen recovery tower) described above is still in operation. Even if not, the cleaning step of the hydrogen recovery tower can be performed using the cleaning hydrogen remaining in the cleaning hydrogen purification tower.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not restrict | limited by the following Example from the first.

  In order to confirm the effect of the present invention, the configuration of the high-purity hydrogen purification system of FIG. 1 exemplified in the present embodiment is employed, and the operation shown in the time step table of Table 1 is adopted to achieve high purity. A hydrogen purification test was conducted.

The experimental conditions are as follows.
<Purified gas (hydrogen-containing gas A) conditions>
Pressure: 0.9 MPa
Temperature: 20 ° C
Flow rate: 2.0NL / min
Composition: H ₂ : 80%, CO ₂ : 20% (hydrogen partial pressure 0.72 MPa)
<Hydrogen storage alloy and cleaning hydrogen storage alloy>
AB5 hydrogen storage alloy adjusted so that the equilibrium pressure at 20 ° C. is 0.2 MPa <Heat medium and refrigerant conditions>
Heating medium conditions: 80 ° C hot water, flow rate 3L / min
Refrigerant conditions: 20 ° C cold water, flow rate 3L / min
<Cycle pattern of hydrogen recovery tower (each tower)>
First hydrogen storage step: 30 minutes First purge step: 5 minutes Cleaning step: 5 minutes First heating step: 10 minutes First hydrogen releasing step: 30 minutes First cooling step: 10 minutes <for washing Cycle pattern of hydrogen purification tower (each tower)>
Second hydrogen storage step: 10 minutes (a portion of high-purity hydrogen (product hydrogen) C is stored at 0.125 NL / min)
Second purge step: 5 minutes Second heating step: 5 minutes Second hydrogen release step: 5 minutes (release of 0.25 NL / min as cleaning hydrogen)
Second cooling step: 10 minutes

When the above steps were performed 30 cycles, a hydrogen recovery rate of 87% and an average concentration of high purity hydrogen of 99.9999% were obtained.

[Comparative example]
The experimental condition is that, in the above-described example (the present invention), a cleaning hydrogen purification tower is not installed, and a part of high-purity hydrogen (product hydrogen) C is used as cleaning hydrogen in the cleaning process of the hydrogen recovery tower. Is the same as in the above embodiment. As a result, the hydrogen recovery rate was 85%, and the average concentration of the obtained high purity hydrogen was 99.9%.

  As described above, only the above-described example (the present invention) satisfies the average concentration of high-purity hydrogen of 99.9999% and the hydrogen recovery rate of 87% or more.

  The hydrogen concentration of the hydrogen-containing gas A used in this example and the comparative example was 80% and the pressure was 0.9 MPa. However, the hydrogen concentration is not necessarily limited to this concentration. High-purity hydrogen purification is possible at any pressure and temperature as long as it is equal to or higher than the equilibrium pressure of the storage alloy and the hydrogen storage alloy for cleaning. Further, when CO other than hydrogen, which is a poisoning factor of the hydrogen storage alloy and the cleaning hydrogen storage alloy, is contained in the gas other than hydrogen, it may be removed using a CO selective adsorbent in the previous stage.

1a, 1b, 1c: Hydrogen recovery towers 2a, 2b, 2c, 12a, 12b, 12c: Medium flow passage 3: Pressure control valves 4, 5, 14, 15: Valve 6: Vacuum pumps 7, 8, 9: Mass flow controller 11a, 11b, 11c: Hydrogen purification tower for cleaning A: Hydrogen-containing gas B: Off-gas C: High-purity hydrogen (product hydrogen)

Claims (8)

A hydrogen-containing gas was passed through a hydrogen recovery tower filled with a hydrogen-occlusion alloy, a first hydrogen-occlusion step of occluding the hydrogen-containing gas in the hydrogen-occlusion alloy, and the hydrogen-occlusion alloy occluded hydrogen. A first purge step for purging impurity gas remaining in the subsequent hydrogen recovery tower, a cleaning step for discharging impurities remaining in the hydrogen recovery tower after the first purge step, and after this cleaning step A high-purity hydrogen refining method comprising: a first hydrogen releasing step of releasing hydrogen stored in the first hydrogen storage step from the hydrogen recovery tower to obtain high-purity hydrogen;
A cleaning hydrogen purification tower filled with a cleaning hydrogen storage alloy having a volume smaller than the volume of the hydrogen storage alloy;
A part of the high-purity hydrogen released from the hydrogen recovery tower in the first hydrogen releasing step is passed through the cleaning hydrogen purification tower, and the hydrogen in the part of the high-purity hydrogen is further stored in the cleaning hydrogen storage. A second hydrogen storage step for storing in the alloy; a second purge step for purging the impurity gas slightly remaining in the cleaning hydrogen purification tower after storing the hydrogen in the cleaning hydrogen storage alloy; A second hydrogen releasing step of releasing hydrogen stored in the second hydrogen storage step after the second purge step to obtain cleaning hydrogen by releasing the hydrogen stored in the cleaning hydrogen purification tower;
A high-purity hydrogen refining method, wherein the cleaning hydrogen obtained in the second hydrogen releasing step is used for discharging impurities in the cleaning step.   2. The high-purity hydrogen purification method according to claim 1, wherein the volume of the hydrogen storage alloy for cleaning is 20% to 80% of the volume of the hydrogen storage alloy.   The hydrogen recovery tower has a first heating step for preheating the hydrogen storage alloy in the hydrogen recovery tower between the washing step and the first hydrogen releasing step, and the first hydrogen releasing step and the first hydrogen The high-purity hydrogen purification method according to claim 1 or 2, further comprising a first cooling step of cooling the hydrogen storage alloy in the hydrogen recovery tower in advance during the storage step.   The high-purity hydrogen purification method according to claim 1, wherein the hydrogen storage alloy is an AB5 hydrogen storage alloy. The hydrogen storage alloy is an AB5 hydrogen storage alloy, and the hydrogen equilibrium pressure of the AB5 hydrogen storage alloy is 0.05 MPa or more and 0.3 MPa or less,
A medium flow passage for temperature control of the AB5 hydrogen storage alloy is provided inside or outside the hydrogen recovery tower,
In the first hydrogen storage step, the first purge step, the cleaning step and the first cooling step, a medium having a temperature of 0 ° C. or more and less than 40 ° C. is circulated through the medium flow path,
4. The high purity hydrogen purification method according to claim 3, wherein in the first hydrogen releasing step and the first heating step, a medium of 40 ° C. or higher and lower than 150 ° C. is circulated through the medium flow passage.   The cleaning hydrogen purification tower has a second heating step of preheating the cleaning hydrogen storage alloy in the cleaning hydrogen purification tower between the second purge step and the second hydrogen release step, 3. The method according to claim 1, further comprising a second cooling step of cooling the cleaning hydrogen storage alloy in the cleaning hydrogen purification tower in advance between the hydrogen release step and the second hydrogen storage step. High-purity hydrogen purification method.   2. The high-purity hydrogen purification method according to claim 1, wherein the cleaning hydrogen storage alloy is an AB5 hydrogen storage alloy. The cleaning hydrogen storage alloy is an AB5-based hydrogen storage alloy, and the hydrogen equilibrium pressure of the AB5-based hydrogen storage alloy is 0.05 MPa or more and 0.3 MPa or less,
A medium flow passage for temperature control of the AB5 hydrogen storage alloy is provided inside or outside the cleaning hydrogen purification tower,
In the second hydrogen storage step, the second purge step and the second cooling step, a medium having a temperature of 0 ° C. or more and less than 40 ° C. is circulated through the medium flow path,
The high-purity hydrogen purification method according to claim 6, wherein in the second hydrogen releasing step and the second heating step, a medium of 40 ° C. or higher and lower than 150 ° C. is circulated through the medium flow path.

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