JP2012001380A - Hydrogen purification system, low-temperature waste heat utilizing system, and hydrogen purification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce poisoning of a hydrogen storage alloy caused by CO and COin a system in which a hydrogen gas is separated and purified utilizing the hydrogen storage alloy, and to suppress deterioration in its performance.SOLUTION: In the hydrogen purification system, from the gas to be treated including either or both of CO and COand hydrogen, the hydrogen is separated and purified. The system includes: an introduction path 1a of introducing the gas to be treated; a chamber (hydrogen separation purification part 1) connected with the introduction path; a hydrogen storage alloy stored inside the chamber and occluding and releasing the hydrogen in the gas to be treated; a gas exhaust path (1c) connected to the chamber and discharging the gas to be treated other than the hydrogen to the outside of the chamber along with the occlusion of the hydrogen; a hydrogen transfer path (1b) of transferring the hydrogen to the outside of the chamber along with the releasing of the hydrogen; and a heating means (low-temperature waste heat source 2) of heating the hydrogen storage alloy to an operating temperature of 120 to 200°C and performing the occlusion and release of the hydrogen with the hydrogen storage alloy.

Description

  The present invention relates to a hydrogen purification system and a hydrogen purification method for separating and purifying hydrogen from a reformed gas containing carbon monoxide and carbon dioxide together with hydrogen using a hydrogen storage alloy, and a low-temperature exhaust heat utilization system in which the hydrogen purification is performed. Is.

Conventionally, a system using a hydrogen storage alloy is known as a simple hydrogen purifier. However, it is considered that a system using a hydrogen storage alloy cannot normally be used in a situation where the hydrogen storage alloy deteriorates in performance due to CO, CO ₂ or the like and contains a lot of gas such as CO, such as reformed gas. ing.

The one shown in FIG. 15 is proposed in Patent Document 1, and a reformer / transformer 100, a CO remover 101, a hydrogen separation and recovery device 102, and a heat exchanger 103 are connected in series. Next, the operation will be described. First, the hydrocarbon-containing fuel A is reformed with steam in the reformer / transformer 100 to produce a hydrogen-rich modified gas B, and this modified gas B is heat-exchanged in the heat exchanger 103, and then the CO The carbon monoxide (CO) is adsorbed and removed by contacting with a CO adsorbent loaded with copper halide and filled in the remover 101. Thereafter, hydrogen is occluded by the hydrogen occlusion material of the hydrogen separation / recovery device 102, and the occluded hydrogen is released from the occlusion material to obtain high purity hydrogen D.
The above system is a simple system among the systems using the hydrogen storage material for hydrogen separation and purification, but the hydrogen storage alloy is poisoned by CO that could not be removed by the CO remover 101, and the performance deteriorates. There's a problem. For this reason, in this method, the hydrogen storage material must be coated with fluorine or the like.

On the other hand, as a method for removing carbon monoxide (CO) from a fuel reformed gas containing hydrogen gas, generally, as shown in FIG. 16, a CO selective oxidizer 112 provided at the rear stage of the reformer 111 is used. A method of removing carbon monoxide (CO) is used (see Non-Patent Document 1). In this apparatus, methanol, ethanol or dimethyl ether raw fuel is vaporized by the vaporizer 110 using the exhaust heat of the combustor 113, mixed with water vapor (H ₂ O), and reformed by the reformer 111. To produce reformed gas containing hydrogen. In the reforming, since carbon monoxide is generated and contained in the reformed gas, it is selectively oxidized in the CO selective oxidizer 112 to be CO ₂ . The reformed gas can be used for the fuel electrode of the fuel cell main body.

Further, a method of removing CO ₂ , CH _4, and H ₂ O using hydrogen PSA after removing CO with a CO selective oxidation catalyst has been studied (see Non-Patent Document 2). Since this method removes in advance CO, which is the main cause of the increase in the size of the adsorption tower in the hydrogen PSA method, it leads to a reduction in the size of the adsorption tower.

JP 2006-342014 A

NEDO site map data (data, database-new energy data-fy16 figure "steam reforming system configuration (methanol)") NEDO 2001 Report, Development of Hydrogen Production Technology by New PSA Method, 2002

However, in the former method shown in the non-patent literature, a CO remover using a CO adsorbent is used, and carbon dioxide (CO ₂ ), methane (CH ₄ ), and moisture (H ₂ O) are removed. However, it cannot be used for a fuel cell for home use or a fuel cell for a mobile body represented by an automobile.
Further, in the latter method shown in non-patent literature, when air is introduced to oxidize CO prior to PSA, it is necessary to supply oxygen in an amount equal to or greater than the amount of CO oxidation so that CO can be reliably removed. some reason, together with oxygen which does not react with CO decreases the collection efficiency of H ₂ consumed and H ₂ react with H _2, methanation occurs as a side reaction hardly CH ₄ which is removed in the PSA to generate In addition, there is a problem that nitrogen (N ₂ ), which is also difficult to remove by PSA, is mixed in the system.

As described above, in a conventional system for separating and purifying hydrogen gas using a hydrogen storage alloy, it is inevitable that CO, CO _{2 and the} like remain, and this gas poisons the hydrogen storage alloy and has a performance. There are problems such as deterioration and the need for an excessively large CO adsorption removal apparatus.

  The object of the present invention is to solve the problems of the conventional proposals described above.

  That is, the hydrogen purification system of the present invention is a hydrogen purification system that separates and purifies hydrogen from a gas to be treated containing one or both of carbon monoxide and carbon dioxide and hydrogen, and introduces the gas to be treated. An introduction path, a chamber to which the introduction path is connected, a hydrogen storage alloy that is housed in the chamber and that stores and releases hydrogen in the gas to be processed, and is connected to the chamber, and accompanies the hydrogen storage A gas discharge path for discharging the gas other than hydrogen to the outside of the chamber, a hydrogen transfer path for transferring hydrogen to the outside of the chamber as the hydrogen is released, and an operating temperature of the hydrogen storage alloy of 120 to 200 ° C. And heating means for storing and releasing hydrogen with the hydrogen storage alloy.

  The low-temperature exhaust heat utilization system of the present invention includes the hydrogen purification system of the present invention, and a reforming unit that generates combustion reformed gas using hydrocarbon as a raw material and low-temperature exhaust heat as a heating source, Is supplied to the hydrogen generation system as a gas to be treated.

  In the hydrogen purification method of the present invention, a gas to be treated containing one or both of carbon monoxide and carbon dioxide and hydrogen is brought into contact with a hydrogen storage alloy having an operation temperature in the storage / release of hydrogen of 120 to 200 ° C. The hydrogen in the gas to be treated is separated and purified by occlusion and release.

In the present invention, by setting the operating temperature of the hydrogen storage alloy to 120 to 200 ° C., poisoning due to CO contained in the gas to be treated can be minimized and performance degradation can be suppressed. It is also effective against poisoning by CO ₂ .
For example, a reformed gas obtained by reforming hydrocarbons contains CO at a concentration of about 300 ppm and a CO ₂ concentration of 1000 ppm to several tens of percent. Even in such a reformed gas, the present invention can effectively prevent the poisoning of the hydrogen storage alloy.

In addition, when the said operating temperature is less than 120 degreeC, it will become easy to produce poisoning by CO, and it will become difficult to carry out the process of the to-be-processed gas containing CO continuously and stably. Moreover, when it exceeds 200 degreeC, the equilibrium pressure at the time of hydrogen occlusion of a hydrogen occlusion alloy will rise, and the hydrogen recovery and refinement | purification performance will fall. In addition, the heating temperature required for releasing H ₂ after recovery becomes high, and there are problems in the heat resistance and strength of the container. Therefore, the operation temperature is set to 120 ° C to 200 ° C.

In the present invention, the type of the hydrogen storage alloy is not limited. FIG. 10 shows a range of temperature and hydrogen pressure as PT characteristics of the hydrogen storage alloy usable in the present invention. In this range, various hydrogen storage alloys can be used. For example, AB type ₅ alloy (MmNi, Ni, Al, Mn, Co can be substituted for adjusting the equilibrium pressure) {Al, Mn has an equilibrium pressure. Lower, Co raises the equilibrium pressure}, AB ₂ type alloy, BCC alloy, Mg ₂ Ni alloy, etc. can be used,
In this alloy, AB ₅ series, general formula MmNi _x Al _y (where x + y = 5, 4.5 ≦ x <5.0, 0 <y ≦ 0.5, especially MmNi _4.95 Al _0.05 It is preferable to use an alloy having a PT characteristic that is expressed by an alloy and has an operating temperature of 120 ° C. or higher and 30 MPa or higher, and 200 ° C. of 0.3 MPa or higher. By having a hydrogen equilibrium pressure of 120 MPa or more and 30 MPa or more, good hydrogen storage characteristics are obtained within the operating range, and by having a hydrogen equilibrium pressure of 200 MPa or more and 0.3 MPa or more, it is good within the operation range. Hydrogen release characteristics are obtained.
Further, this Mm _x Ni _y Al _z alloy is very strong against CO ₂ poisoning and has a characteristic of not losing performance even under CO ₂ concentration.

In the present invention, poisoning of the hydrogen storage alloy can be avoided as much as possible when processing the gas to be processed containing CO and CO ₂ as described above. In order to remove CO 2, CO selective oxidation may be performed. By reducing the CO concentration before the treatment with the hydrogen storage alloy, the hydrogen storage alloy is more reliably prevented from being poisoned. However, in the present invention, the degree of demand for CO selective oxidation is not particularly high, and the CO selective oxidation treatment can be performed without using a large-scale CO selective oxidation apparatus or the like.
The CO selective oxidation apparatus can be operated at a temperature of, for example, 100 ° C. to 200 ° C., and CO is converted to CO ₂ (CO + 1 / 2O ₂ → CO ₂ ) by a CO selective oxidation catalyst filled in the apparatus, and a gas CO remaining therein can be reduced.

Moreover, in this invention, it is also possible to provide a PSA apparatus in the front | former stage side of the process by a hydrogen storage alloy. By the treatment using the PSA apparatus, CO, CO ₂ , CH ₄ , H ₂ O and the like can be removed, and purification using a hydrogen storage alloy can be performed to a higher degree. With the PSA device, CO and CO ₂ remaining in the gas to be treated are sufficiently reduced to ensure prevention of poisoning of the subsequent hydrogen storage alloy.

In the present invention, membrane separation of CO and CO ₂ may be performed on the upstream side of the treatment with the hydrogen storage alloy. By the treatment using the membrane separation apparatus, CO and CO ₂ can be removed at a lower cost than the PSA apparatus. By means of the membrane separator, CO and CO ₂ remaining in the gas to be treated are sufficiently reduced to ensure prevention of poisoning of the subsequent hydrogen storage alloy.
Further, in the present invention, the degree of demand for the CO selective oxidation apparatus, PSA apparatus or membrane separation apparatus is not particularly high. Therefore, when a CO selective oxidation apparatus, PSA apparatus or membrane separation apparatus is provided, the conventional high purity hydrogen purification The size and scale of the apparatus can be reduced as compared with a CO selective oxidation apparatus, a PSA apparatus, or a membrane separation apparatus having the CO removal performance required for the apparatus. Further, it is not necessary to provide a CO selective oxidation device in front of the PSA device.

When the hydrogen storage alloy is heated at the operating temperature, it can be heated by an appropriate heating means, and relatively low-temperature exhaust heat (250 to 400 ° C.) discharged from a heating furnace or the like can be used. . The low-temperature exhaust heat can be adjusted to a temperature using warm / cold waste water to obtain the operation temperature of 120 to 200 ° C.
By using the exhaust gas as a heat source, significant energy saving can be achieved.

As described above, according to the present invention, a gas to be treated containing one or both of carbon monoxide and carbon dioxide and hydrogen, and a hydrogen storage alloy having an operation temperature in the storage / release of hydrogen of 120 to 200 ° C. The hydrogen in the gas to be treated is separated and purified by occlusion and release, so that it is energy-saving, compact, low-cost and improved in safety, and stably supplies high-purity hydrogen. There is an effect that makes it possible.
Further, as the hydrogen storage alloy, AB ₅ series, general formula MmNi _x Al _y (where x + y = 5, 4.5 ≦ x <5.0, 0 <y ≦ 0.5, especially MmNi _4.95 Al) _0.05 is preferable) Use of an alloy represented by an alloy and having PT characteristics of 30 MPa or more at an operating temperature of 120 ° C. or more and 0.3 MPa or more at 200 ° C., ensures further poisoning against CO and CO ₂ . Can be prevented.
In addition, by introducing a CO selective oxidation device or PSA device before the hydrogen separation and purification, the load on the hydrogen storage alloy by CO and CO ₂ is reduced, enabling further stabilization of high-purity hydrogen supply. There is an effect.

It is the schematic which shows one basic embodiment of the high purity hydrogen production system in this invention. Similarly, it is the schematic which shows one basic embodiment at the time of introduce | transducing CO selective oxidation. Similarly, it is the schematic which shows one basic embodiment at the time of introducing PSA. Similarly, it is the schematic which shows one basic embodiment at the time of introducing membrane separation. Similarly, it is the schematic which shows the structure of the steam reforming system which used methanol, ethanol, or dimethyl ether as raw fuel. Similarly, it is the schematic which shows the structure of the steam reforming system which employ | adopted CO selective oxidation by using methanol, ethanol, or dimethyl ether as a raw fuel. Similarly, it is the schematic which shows the path | route between a CO selective oxidation apparatus and a hydrogen separation refinement | purification part. Similarly, it is the schematic which shows the structure of the steam reforming system which employ | adopted PSA, using methanol, ethanol, or dimethyl ether as a raw fuel. Similarly, it is the schematic which shows the structure of the steam reforming system which uses methanol, ethanol, or dimethyl ether as raw fuel, and employ | adopted the membrane separation. It is a graph showing the PT characteristic of the hydrogen storage alloy which is an application object in the present invention. Is a graph showing the effect of CO poisoning of the hydrogen storage alloy (AB ₅ type alloy) in the embodiment of the present invention. Also, a graph showing the results of repetitive durability test with hydrogen gas containing 1000ppm of CO ₂ in MmNiAl alloy. Also, a graph showing a result of continuing the cycle test at 25% CO ₂ containing gas mixture in MmNiMnAl alloy. Similarly, a graph showing that the MmNiAl alloy recovers the hydrogen storage amount to almost the original level by carrying out 80 ° C. vacuum degassing as a recovery process. It is the schematic which shows an example of the conventional hydrogen purification system. It is the schematic which shows the other conventional hydrogen purification system.

Below, one Embodiment of this invention is described based on FIG.
(Embodiment 1)
An embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a schematic view showing an embodiment of the high purity hydrogen production system of the present invention.
The hydrogen purification system shown in FIG. 1 includes a hydrogen separation and purification unit 1 containing a hydrogen storage alloy. The hydrogen separation and purification unit 1 has a chamber (not shown) containing a hydrogen storage alloy, and an introduction path 1a for introducing reformed fuel gas and a hydrogen transfer path 1b for transferring purified hydrogen are connected to each other. Has been.
The hydrogen separation and purification unit 1 is connected to an exhaust heat gas introduction path 2a for introducing a low temperature exhaust heat gas (for example, 250 to 400 ° C.) from the low temperature exhaust heat source 2 to heat the hydrogen storage alloy. It is possible.

The operation of the above system will be described.
The reformed fuel gas corresponding to the gas to be treated of the present invention contains one or both of carbon monoxide and carbon dioxide and hydrogen.
The reformed fuel gas is introduced into the hydrogen separation and purification unit 1 through the introduction path 1a. The reformed fuel gas can be obtained by reforming hydrocarbons, etc., but the production process is not particularly limited as in the present invention, and as described above, with one or both of carbon monoxide and carbon dioxide. as long as containing hydrogen, the other, may include other gases such as CH _4.
In the hydrogen separation and purification unit 1, the low-temperature exhaust heat gas is introduced from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2 a. At this time, the temperature of the low-temperature exhaust heat gas is adjusted by warm / cold drainage or the like to heat / cool the hydrogen storage alloy.

  When hydrogen storage is performed in the hydrogen separation and purification unit 1, hydrogen in the reformed fuel gas introduced is stored at a storage temperature of 120 ° C. or higher (but 200 ° C. or lower). As a result, hydrogen and other gases in the reformed fuel gas are separated. When the hydrogen storage alloy has sufficiently stored hydrogen, the introduction of the reformed fuel gas is interrupted, and other gases stored in the hydrogen separation and purification unit 1 are discharged out of the hydrogen separation and purification unit 1. The discharge can be performed through a gas discharge path (not shown).

After sufficiently releasing the gas from the hydrogen separation and purification unit 1, the hydrogen storage alloy is heated to a release temperature (200 ° C. or less, but 120 ° C. or more) higher than the storage temperature by the low-temperature exhaust heat gas. The heating temperature can be obtained by adjusting the temperature using low-temperature exhaust heat gas and hot / cold waste water as described above. The hydrogen storage alloy is operated at an operating temperature of 120 to 200 ° C. to store and release hydrogen. To do. Therefore, the low temperature exhaust heat gas and the warm / cold drainage correspond to the heating means of the present invention.
The high purity hydrogen 9 released from the hydrogen storage alloy is transferred to an appropriate utilization system through the hydrogen transfer path 1b. In the above system, gas such as CO and CO ₂ is contained in the reformed fuel gas as described above, but hydrogen occlusion and hydrogen release are performed within the operating temperature range of 120 to 200 ° C. with respect to the hydrogen occlusion alloy. By performing, the poisoning by the said gas can be prevented and the performance stabilized over the long term can be obtained.

Next, another embodiment will be described with reference to FIG. In this embodiment, the same components as those in the above embodiment are denoted by the same reference numerals and the description thereof is simplified.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided in the same manner as the previous embodiment, and the low temperature exhaust heat gas is introduced into the hydrogen separation and purification unit 1 from the low temperature exhaust heat source 2 through the exhaust heat gas introduction path 2a and heated. And it has the same structure as the said embodiment in the point that the heating temperature by this low-temperature waste heat gas is adjusted with warm / cold waste water.
Furthermore, in this embodiment, the CO selective oxidation device 3 is provided in the preceding stage of the hydrogen separation and purification unit 1. A CO selective oxidation catalyst is accommodated in the CO selective oxidation apparatus 3 and selectively oxidizes CO in the introduced gas. The type of the CO selective oxidation catalyst is not particularly limited in the present invention, and known ones can be used.
An introduction path 3a for introducing fuel reformed gas is connected to the gas introduction side of the CO selective oxidation apparatus 3, and the introduction path 1a connected to the hydrogen separation and purification unit 1 is connected to the gas discharge side of the CO selective oxidation apparatus 3. Is connected.

The operation of the above system will be described. A reformed fuel gas corresponding to the gas to be treated according to the present invention is introduced into the CO selective oxidation apparatus 3 through the introduction path 3a. In the CO selective oxidizing unit 3, can be CO in the reformed fuel gas is CO ₂ becomes selected oxidized by the action of the catalyst to selectively oxidize CO in the reformed fuel gas at a temperature of 100 to 200 ° C. . The reformed fuel gas obtained by selectively oxidizing CO is transferred to the hydrogen separation and purification unit 1 through the introduction path 1a to separate and purify hydrogen. The operation in the hydrogen separation and purification unit 1 is the same as in the above embodiment, and high-purity hydrogen 9 is obtained. At this time, the reformed fuel gas has been reduced in concentration by the CO selective oxidizer 3 in advance, so that it is possible to more effectively prevent CO poisoning of the hydrogen storage alloy in the hydrogen separation and purification unit 1. it can.

Next, still another embodiment will be described with reference to FIG. In this embodiment, the same components as those in each of the above embodiments are denoted by the same reference numerals and the description thereof is simplified.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided in the same manner as the previous embodiment, and the low temperature exhaust heat gas is introduced into the hydrogen separation and purification unit 1 from the low temperature exhaust heat source 2 through the exhaust heat gas introduction path 2a and heated. And it has the same structure as said each embodiment at the point that the heating temperature by this low-temperature waste heat gas is adjusted with warm / cold drainage.

Furthermore, in this embodiment, the PSA device 5 is provided in the previous stage of the hydrogen separation and purification unit 1, and the compressor 4 is provided in the previous stage of the PSA device. The introduction path 4a for introducing the fuel reformed gas is connected to the gas introduction side of the compressor 4, and the introduction path 5a is connected to the PSA apparatus 5 on the discharge side of the compressed gas. . The introduction path 1 a connected to the hydrogen separation and purification unit 1 is connected to the gas discharge side of the PSA device 5.
The PSA device 5 contains an adsorbent that adsorbs a gas other than hydrogen. For example, an adsorbent that adsorbs CO, CO ₂ , CH _{4 and the} like is exemplified. The adsorbent may consist of a plurality of types, or may adsorb different gases with different adsorbents. In the present invention, the type of adsorbent is not particularly limited, and an adsorbent appropriately selected according to the gas to be adsorbed can be used.

  The operation of the above system will be described. The reformed fuel gas corresponding to the gas to be treated of the present invention is introduced into the compressor 4 through the introduction path 4a, and is introduced in a state where the pressure is increased by being compressed by the compressor 4. It is introduced into the PSA device 5 via the path 5a. In the PSA device 5, a desired gas component (other than hydrogen) in the reformed fuel gas whose pressure has been increased is adsorbed by the adsorbent. The reformed fuel gas from which unnecessary gas has been removed by adsorption has a high hydrogen component ratio, and is transferred to the hydrogen separation and purification unit 1 through the introduction path 1a to separate and purify hydrogen. The operation in the hydrogen separation and purification unit 1 is the same as that in each of the above embodiments, and high-purity hydrogen 9 is obtained. At this time, the reformed fuel gas has a concentration of gas components other than hydrogen reduced by the PSA device 5 in advance, so that the hydrogen separation alloy 1 can be more effectively prevented from being poisoned. can do.

Next, still another embodiment will be described with reference to FIG. In this embodiment, the same components as those in each of the above embodiments are denoted by the same reference numerals and the description thereof is simplified.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided as in the above embodiment, and the low temperature exhaust heat gas is introduced into the hydrogen separation and purification unit 1 from the low temperature exhaust heat source through the exhaust heat introduction path 2a and heated. It has the same configuration as the above embodiment in that the heating temperature by the low-temperature exhaust heat gas is adjusted by the hot / cold drainage.
Furthermore, in this embodiment, a membrane separation device 8 is provided in the preceding stage of the hydrogen separation and purification unit 1. The membrane separation device 8, CO · CO ₂ separation membrane has been accommodated, to separate the CO and CO ₂ in the gas introduced from the gas. The type of the CO / CO ₂ separation membrane is not particularly limited in the present invention, and known ones can be used. The introduction path 8a for introducing the fuel reformed gas is connected to the gas introduction side of the membrane separation apparatus 8, and the introduction path 1a to which the hydrogen separation purification unit 1 is connected is connected to the gas discharge side of the membrane separation apparatus 8. Has been.

Next, a low temperature exhaust heat utilization system equipped with a hydrogen purification system in the present invention will be described.
FIG. 5 is a diagram showing the low-temperature exhaust heat utilization system.
The basic configuration of the hydrogen purification system in the low-temperature exhaust heat utilization system is the same as that of the system shown in FIG. 1, and the same configurations as those described in the above embodiment will be described with the same reference numerals.
This embodiment also includes a hydrogen separation and purification unit 1. In this embodiment, MmNi _x Al _y (where, x + y = 5,4.5 ≦ x <5.0,0 <y ≦ 0.5 is hydrogen absorbing alloy of AB ₅ type hydrogen isolation purification unit 1, In particular, MmNi _4.95 Al _0.05 is preferable). A reformer 10 is provided upstream of the hydrogen separation and purification unit 1.
That is, the upstream end of the introduction path 1 a connected to the hydrogen separation and purification unit 1 is connected to the cooler 12, and the introduction path 10 b is connected to the gas introduction side of the cooler 12. The introduction path 10 b is connected to the gas discharge side of the reformer 10. The reformer 10 can introduce fuel from a fuel tank 11 that uses methanol, ethanol, or dimethyl ether as a steam reformed fuel via a fuel supply path 10a. Further, in the reformer 10, heat exchange is possible by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas transfer path 2b.

The hydrogen separation and purification unit 1 can exchange heat with the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2a. Heat exchange with cold drainage is possible. Adjustment of the heating temperature of the hydrogen storage alloy in the hydrogen separation and purification unit 1 becomes possible by adjusting the low-temperature exhaust heat gas and the hot / cold drainage.
In the hydrogen separation and purification unit 1, a hydrogen transfer path 1b for transferring purified hydrogen to the outside of the chamber is connected, and a gas exhaust path 1c for discharging residual CO ₂ gas and the like from which hydrogen has been separated to the outside of the chamber is connected. Has been. The hydrogen separation and purification unit 1 is connected to an activation device 7 that performs a recovery process of the hydrogen storage alloy in the hydrogen separation and purification unit 1.

Next, the operation of the system will be described.
In this system, steam reformed fuel (methanol, ethanol, or DME) is accommodated in the fuel tank 11, and the steam reformed fuel is introduced into the reformer 10 through the fuel supply path 10a. Low temperature exhaust heat discharged from the low temperature exhaust heat source 2 is introduced into the reformer 10 as a heat source through the exhaust heat gas transfer pipe 2b, and the steam reformed fuel is steam reformed at a low temperature (250 ° C. to 400 ° C.). As a result, significant energy savings can be achieved in the reforming process, and the CO concentration contained in the reformed gas is suppressed to about 1%. The reformed gas contains hydrogen monoxide (CO), carbon dioxide (CO ₂ ), etc. that degrade the performance of the hydrogen storage alloy by poisoning in addition to hydrogen (H ₂ ) in the process of steam reforming. However, with respect to the CO concentration, the generated amount is suppressed to about 1% as described above.

Subsequently, the reformed gas is introduced into the cooler 12 through the introduction path 10b and cooled, and moisture in the gas is removed. The configuration of the cooler 12 is not particularly limited as long as the reformed gas can be cooled. The hydrogen-rich reformed gas thus obtained is introduced into the hydrogen separation and purification unit 1 through the introduction path 1a.
In the hydrogen separation and purification unit 1, low-temperature exhaust heat gas is introduced from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2 a, and hot / cold waste water is introduced through the drain pipe 6. The hydrogen storage alloy in the hydrogen separation and purification unit 1 is heated to an operating temperature of 120 to 200 ° C.

When hydrogen storage is performed in the hydrogen separation and purification unit 1, a hydrogen storage alloy made of Mm _x Ni _y Al _z alloy is stored at a storage temperature of 120 ° C. or higher to store hydrogen in the reformed fuel gas and store the hydrogen. And other gases. When the hydrogen storage alloy has sufficiently stored hydrogen, the introduction of the reformed fuel gas is interrupted, and other gases stored in the hydrogen separation and purification unit 1 are discharged out of the hydrogen separation and purification unit 1 through the gas exhaust passage 1c. .
After sufficiently releasing the gas from the hydrogen separation and purification unit 1, the hydrogen storage alloy was heated to a release temperature of 200 ° C. or less higher than the storage temperature by the low-temperature exhaust heat gas, and was stored in the hydrogen storage alloy. Hydrogen is released. Hydrogen released from the hydrogen storage alloy is recovered as high-purity hydrogen 9 through the hydrogen transfer path 1b and transferred to an appropriate utilization system or the like.
In addition, after recovering high-purity hydrogen 9, the hydrogen storage performance is recovered by vacuum degassing at 80 ° C. in the activation device 7 for the Mm _x Ni _y Al _z alloy filled in the hydrogen separation and purification unit 1. By carrying out the above, it becomes possible to continue high-purity hydrogen separation and purification. In addition, the influence of poisoning of the hydrogen storage alloy by CO ₂ is eliminated by adopting the AB ₅ series Mm _x Ni _y Al _z alloy.
Therefore, it is possible to construct a system that is more energy saving, lower cost, and safer than before.

Next, another form of the low-temperature exhaust heat utilization system will be described.
FIG. 6 is a diagram showing the low-temperature exhaust heat utilization system.
The basic configuration of the hydrogen purification system in the low-temperature exhaust heat utilization system is the same as that of the system of FIG. 2, and the same configuration as that described in the above embodiment will be described with the same reference numerals.
Also in this embodiment, a hydrogen separation and purification unit 1 is provided, and an Mm _x Ni _y Al _z alloy, which is the same hydrogen storage alloy as described above, is accommodated in the hydrogen separation and purification unit 1. A CO selective oxidation device 3 is provided upstream of the hydrogen separation and purification unit 1.
That is, the CO selective oxidizer 3 is connected to the upstream end of the introduction path 1 a connected to the hydrogen separation and purification unit 1. A CO selective oxidation catalyst is accommodated in the CO selective oxidation apparatus 3 and is used for CO selective oxidation. Further, the CO selective oxidizer 3 is connected to a drain pipe 6 so that warm / cold effluent is sent and heat exchange is possible. The hot / cold effluent exchanged by the CO selective oxidizer 3 is drained. The pipe 6 is configured to be sent to the hydrogen separation and purification unit 1 for heat exchange.

  An introduction path 3 a is connected to the gas introduction side of the CO selective oxidation apparatus 3. The introduction path 3 a is connected to the cooler 12, and an introduction path 10 b is connected to the gas introduction side of the cooler 12. The introduction path 10 b is connected to the reformer 10. In the reformer 10, fuel is introduced from a fuel tank 11 using methanol, ethanol, or dimethyl ether as a steam reformed fuel through a fuel supply path 10a, as in the above embodiment. Further, in the reformer 10, heat exchange is performed by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas transfer path 2b.

Next, the operation of the system will be described.
The steam reformed fuel (methanol, ethanol or DME) accommodated in the fuel tank 11 is introduced into the reformer 10 through the fuel supply path 10a as in the above embodiment, and is exhausted from the low-temperature exhaust heat source 2. Steam reforming is performed in the reformer 10 by the low-temperature exhaust heat transferred through the transfer pipe 2b. The reformed gas is introduced into the cooler 12 through the introduction path 10 b to remove moisture, and is introduced into the CO selective oxidation apparatus 3.
In the CO selective oxidation apparatus 3, a CO selective oxidation catalyst is filled inside, and the introduced CO is selectively oxidized. In this case, heat is exchanged with warm / cold drainage by the drain pipe 6 so that the oxidation reaction is performed at a temperature of 100 ° C. to 200 ° C. As a result, the CO remaining in the gas is reduced to several tens to several hundred ppm.
The reformed gas exiting the CO selective oxidizer 3 is introduced into the hydrogen separation and purification unit 1 and enters the hydrogen separation and purification step. The hydrogen separation and purification step is the same as that described in the above embodiment.
That is, in the hydrogen separation and purification unit 1, the internal temperature of the hydrogen separation and purification unit 1 is reduced by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2 a and the hot / cold drainage sent by the drain pipe 6. The hydrogen storage alloy is heated to a storage temperature of 120 ° C. or higher to store hydrogen in the reformed gas. Thereafter, as in the above-described embodiment, hydrogen and other gases are separated and high-purity hydrogen 9 is obtained through the hydrogen transfer path 1b.
The hot / cold waste water is used in the CO oxidation selection device 3 and then sent to the hydrogen separation and purification unit 1 to be used for temperature adjustment.
As described above, high-purity hydrogen 9 can be obtained stably.

Next, another embodiment of the low-temperature exhaust heat system will be described.
FIG. 7 is a diagram showing the low-temperature exhaust heat utilization system.
The basic configuration of the hydrogen purification system in the low-temperature exhaust heat utilization system is the same as the system shown in FIG. 3, and the same configurations as those described in the above embodiment are denoted by the same reference numerals.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided, and the hydrogen separation and purification unit 1 contains a Mm _x Ni _y Al _z alloy, which is the same hydrogen storage alloy as described above. A CO selective oxidation device 3 or a PSA device 5 is provided upstream of the hydrogen separation and purification unit 1.
That is, the CO selective oxidation device 3 or the PSA device 5 is connected to the upstream end of the introduction path 1 a connected to the hydrogen separation and purification unit 1.
A CO concentration meter 20 capable of outputting a control signal is connected to the introduction path 1 a connected to the hydrogen separation and purification unit 1. Further, an exhaust heat gas introduction path 2 a connected to the hydrogen separation and purification unit 1 and a drain pipe 6 are connected.

Next, the operation of the system will be described.
A gas that has been reformed by the reformer 10 and reduced in CO and CO ₂ by the CO selective oxidation device 3 or the PSA device 5 is supplied to the hydrogen separation and purification unit 1. At this time, the CO concentration meter 20 is set to output a signal when the CO concentration reaches a predetermined value (for example, 1 ppm or less). When the CO concentration reaches a predetermined value (for example, 1 ppm or less), the valve installed in the exhaust heat gas introduction path 2a connected to the hydrogen separation and purification unit 1 is closed and the valve installed in the drain pipe 6 Is opened, and low-temperature exhaust heat (˜80 ° C.) is supplied to the hydrogen separation and purification unit 1. The valve can be opened and closed manually, and the valve may be automatically opened and closed by a signal from the CO concentration meter 20. By this operation, when the CO concentration is small, low-temperature exhaust heat is supplied. It is known that the performance of an alloy such as an AB ₅ type hydrogen storage alloy may deteriorate due to repeated high-temperature operation in addition to poisoning. Therefore, this system enables low-temperature operation when there is no influence of poisoning, so that deterioration of alloy performance can be reduced and long-term stable performance can be obtained.

Next, another embodiment of the low-temperature exhaust heat utilization system will be described.
FIG. 8 is a diagram showing the low-temperature exhaust heat utilization system.
The basic configuration of the hydrogen purification system in the low-temperature exhaust heat utilization system is the same as the system shown in FIG. 3, and the same configurations as those described in the above embodiment are denoted by the same reference numerals.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided. In the hydrogen separation and purification unit 1, an Mm _x Ni _y Al _z alloy (however, x + y = 5, 4.5 ≦ x < 5.0, 0 <y ≦ 0.5) is accommodated. A PSA device 5 is provided upstream of the hydrogen separation and purification unit 1.
That is, the PSA device 5 is connected to the upstream end of the introduction path 1 a connected to the hydrogen separation and purification unit 1. The PSA device 5 has an adsorption tower filled with an adsorbent, and an adsorbent that adsorbs and removes CO, CO ₂ , CH ₄ , and H ₂ O is used. Of these, the CO adsorption / removal equipment is limited in size and scale to such an extent that rough removal up to several hundred ppm is possible. The size and scale of the apparatus can be reduced as compared with the conventional PSA apparatus having the CO removal performance required for high-purity hydrogen purification.
An introduction path 5a is connected to the gas introduction side of the PSA apparatus 5, and an upstream side of the introduction path 5a is connected to a compressor 4 that compresses the reformed gas. The gas introduction side of the compressor 4 is connected to the cooler 12 by an introduction path 4 a, and the introduction path 10 b is connected to the gas introduction side of the cooler 12. The introduction path 10 b is connected to the reformer 10. In the reformer 10, the fuel is introduced from the fuel tank 11 using methanol, ethanol, or dimethyl ether as a steam reformed fuel through the fuel supply path 10a, as in the above embodiment. Further, in the reformer 10, heat exchange is performed by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas transfer path 2b.

Next, the operation of the system will be described.
Similarly to the above embodiment, steam reformed fuel (methanol, ethanol or DME) is introduced from the fuel tank 11 through the fuel supply path 10a to the reformer 10, and the exhaust heat gas transfer pipe 2b is connected from the low temperature exhaust heat source 2. Steam reforming is performed by the low-temperature exhaust heat transferred through the heat exchanger. The reformed gas is introduced into the cooler 12 through the introduction path 10b and moisture is removed, and then introduced into the compressor 4 through the introduction path 4a and compressed. The compressed reformed gas is introduced into the PSA device 5 through the introduction path 5a and adsorbs and removes CO, CO ₂ , CH ₄ , and H ₂ O. Thereby, CO and CO ₂ remaining in the gas are reduced to about several tens to several hundred ppm.

The reformed gas separated by the PSA device 5 is introduced into the hydrogen separation and purification unit 1a via the introduction path 1a and enters the hydrogen separation and purification step. The hydrogen separation and purification step is the same as that described in the above embodiment.
That is, in the hydrogen separation and purification unit 1, the internal temperature of the hydrogen separation and purification unit 1 is reduced by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2 a and the hot / cold drainage sent by the drain pipe 6. The hydrogen storage alloy is heated to a storage temperature of 120 ° C. or higher to store hydrogen in the reformed gas. Thereafter, the hydrogen storage alloy is heated at a temperature higher than the storage temperature (200 ° C. or lower) to release hydrogen, and high-purity hydrogen 9 is obtained through the hydrogen transfer path 1b.
The hydrogen storage alloy in the hydrogen separation and purification unit 1 is subjected to a hydrogen storage performance recovery process by vacuum degassing at 80 ° C. in the activation device 7. In addition, the influence of poisoning of the hydrogen storage alloy by CO ₂ is eliminated by adopting the AB ₅ series Mm _x Ni _y Al _z alloy.

Next, another embodiment of the low-temperature exhaust heat utilization system will be described.
FIG. 9 is a diagram showing the low-temperature exhaust heat utilization system.
The basic configuration of the hydrogen purification system in the low-temperature exhaust heat utilization system is the same as that of the system shown in FIG. 4, and the same configurations as those described in the above embodiment are denoted by the same reference numerals.
Also in this embodiment, the hydrogen separation and purification unit 1 is provided, and the hydrogen separation and purification unit 1 contains a Mm _x Ni _y Al _z alloy that is the same hydrogen storage alloy as described above. A membrane separation device 8 is provided on the upstream side of the hydrogen separation and purification unit 1.
That is, the membrane separation device 8 is connected to the upstream end of the introduction path 1 a connected to the hydrogen separation and purification unit 1. A CO / CO ₂ separation membrane is accommodated in the membrane separation device 8 and is used for separation of CO and CO ₂ from gas.
An introduction path 8 a is connected to the gas introduction side of the membrane separation device 8. The introduction path 8 a is connected to the cooling unit 12, and an introduction path 10 b is connected to the gas introduction side of the cooling unit 12. The introduction path 10 b is connected to the reformer 10. In the reformer 10, fuel is introduced from a fuel tank 11 using methanol, ethanol, or dimethyl ether as a steam reformed fuel through a fuel supply path 10a, as in the above embodiment. Further, in the reformer 10, heat exchange is performed by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas transfer path 2b.

Next, the operation of the system will be described.
The steam reformed fuel (methanol, ethanol or DME) accommodated in the fuel tank 11 is introduced into the reformer 10 through the fuel supply path 10a as in the above embodiment, and is exhausted from the low-temperature exhaust heat source 2. Steam reforming is performed in the reformer 10 by the low-temperature exhaust heat transferred through the transfer pipe 2b. The reformed gas is introduced into the cooler 12 through the introduction path 10 b to remove moisture, and is introduced into the membrane separation device 8.
In the membrane separation device 8, a CO / CO ₂ separation membrane is accommodated therein, and the introduced CO and CO ₂ are separated from the reformed gas. As a result, CO and CO ₂ remaining in the gas are reduced to about 1%.
The reformed gas exiting the membrane separation device 8 is introduced into the hydrogen separation and purification unit 1 and enters the hydrogen separation and purification step. The hydrogen separation and purification step is the same as that described in the above embodiment.
That is, in the hydrogen separation and purification unit 1, the internal temperature of the hydrogen separation and purification unit 1 is reduced by the low-temperature exhaust heat gas sent from the low-temperature exhaust heat source 2 through the exhaust heat gas introduction path 2 a and the hot / cold drainage sent by the drain pipe 6. The hydrogen storage alloy is heated to a storage temperature of 120 ° C. or higher to store hydrogen in the reformed gas. Thereafter, high purity hydrogen 9 is obtained through hydrogen transfer pipe 1b after being separated into hydrogen and other gases as in the above embodiment.
The hot / cold waste water is sent to the hydrogen separation and purification unit 1 and used for temperature adjustment.
As described above, high-purity hydrogen 9 can be obtained stably.

An embodiment of the present invention will be described below.
Figure 11 is a AB ₅ type hydrogen absorbing alloy of the MmNi _x Al _y (where, x + y = 5,4.5 ≦ x <5.0,0 <y ≦ 0.5, in particular _MmNi 4.95 _{Al 0. 05} is preferable), and hydrogen is occluded / desorbed when hydrogen is selectively occluded / released using a gas containing 300 ppm or 2 ppm of CO and hydrogen at different operating temperatures. At the operating temperature of 120 ° C. as the lower limit, the performance degradation of the hydrogen storage alloy is small even by repeated hydrogen absorption / release, indicating that the influence of poisoning on CO is small. On the other hand, when the operating temperature is set to 35 ° C., the hydrogen absorption / desorption characteristics are inferior to those at 120 ° C. even at a CO concentration of 2 ppm. Furthermore, in the same example where the operating temperature was lowered to 35 ° C., the hydrogen storage alloy was poisoned at an early stage and the CO concentration was 300 ppm, making it difficult to use. In addition, even when the CO concentration was 300 ppm and the operation temperature was 80 ° C., the hydrogen storage alloy was poisoned early, making it difficult to use. Therefore, the operating temperature of the hydrogen storage alloy needs to be 120 ° C. or higher regardless of the CO concentration.

Here, FIGS. 12 to 14 are shown as reference data for the Mm _x Ni _y Al _z alloy. FIG. 12 shows the result of a repeated durability test using a hydrogen gas containing 1000 ppm of CO ₂ with an MmNiAl alloy, and shows that the same AB ₅ series alloy is less susceptible to surface poisoning by CO ₂ . FIG. 13 shows the result of continuing the repeated test of the same alloy in a mixed gas containing 25% CO ₂ , and it can be seen that the self-healing behavior of the amount of hydrogen transfer is seen as the number of repetitions increases. Here, in order to adjust the equilibrium pressure, Al is partially substituted with Mn to obtain an MmNiMnAl alloy.

As described above, the Mm _x Ni _y Al _z alloy has a property that it is difficult to be poisoned with respect to CO _{2. By} storing and releasing hydrogen at an operating temperature within a range of 120 to 200 ° C., CO, CO ₂ can be stably obtained with good hydrogen absorption / release characteristics.
FIG. 14 shows that the same alloy recovers the hydrogen storage amount to almost the original level by carrying out 80 ° C. vacuum degassing as a recovery treatment.
In the absorption / release characteristics shown in FIG. 14, after the activation (hydrogenation) of performing vacuum degassing at 80 ° C. and pure hydrogen storage at the pressure shown in the drawing at 35 ° C. three times in one step, It was brought into contact with the indicated standard gas, and the recovery process of vacuum degassing was carried out at 80 ° C. in two steps to make contact with pure hydrogen. Next, the gas was contacted with the standard gas as it was, and the absorption and release were repeated, and thereafter the absorption and emission were repeated with pure hydrogen. As a result, it can be seen that stable hydrogen absorption / release characteristics are maintained over a long period of time.

  The present invention has been described based on the above-described embodiments and examples. However, the present invention is not limited to the contents of the description, and appropriate modifications can be made without departing from the scope of the present invention. is there.

DESCRIPTION OF SYMBOLS 1 Hydrogen separation refinement | purification part 2 Low temperature waste heat source 3 CO selective oxidation apparatus 4 Compressor 5 PSA apparatus 6 Drain pipe 7 Activation apparatus 8 Membrane separation apparatus 9 High-purity hydrogen 10 Reformer 11 Fuel tank 12 Cooler

Claims (9)

A hydrogen purification system for separating and purifying hydrogen from a gas to be treated containing one or both of carbon monoxide and carbon dioxide and hydrogen,
An introduction path for introducing the gas to be processed, a chamber to which the introduction path is connected, a hydrogen storage alloy that is accommodated in the chamber and stores and releases hydrogen in the gas to be processed, and is connected to the chamber. A gas discharge path for discharging the gas other than hydrogen to the outside of the chamber as the hydrogen is stored, a hydrogen transfer path for transferring hydrogen to the outside of the chamber as the hydrogen is released, and the hydrogen storage alloy. A hydrogen refining system comprising heating means for heating to an operating temperature of 120 to 200 ° C. to cause hydrogen storage alloy to store and release hydrogen.   2. The hydrogen purification system according to claim 1, further comprising a CO selective oxidation apparatus that treats the gas to be treated on the upstream side of the gas to be treated of the hydrogen storage alloy chamber.   A PSA device for processing the gas to be processed and a compressor for compressing the gas to be processed and supplying the gas to the PSA device are provided on the upstream side of the gas to be processed of the hydrogen storage alloy chamber. The hydrogen purification system according to any one of claims 1 and 2.   The hydrogen purification system according to any one of claims 1 to 3, further comprising a membrane separation device for processing the gas to be processed on the upstream side of the gas to be processed in the hydrogen storage alloy chamber.   The hydrogen purification system according to claim 1, wherein the heating unit uses low-temperature exhaust heat as a heating source.   The hydrogen purification system according to any one of claims 1 to 5 and a reforming unit that generates hydrocarbon reformed gas using hydrocarbon as a raw material and low-temperature exhaust heat as a heating source, wherein the combustion reformed gas is a gas to be treated. A low-temperature exhaust heat utilization system characterized by being provided for the hydrogen generation system.   A treatment gas containing one or both of carbon monoxide and carbon dioxide and hydrogen is brought into contact with a hydrogen storage alloy having an operation temperature in the storage / release of hydrogen of 120 to 200 ° C. A hydrogen purification method characterized by separating and purifying hydrogen by occlusion and release.   The hydrogen purification method according to claim 7, wherein the gas to be treated is subjected to one or both of carbon monoxide weight loss treatment and carbon dioxide weight loss treatment prior to contact with the hydrogen storage alloy.   The hydrogen purification method according to claim 7 or 8, wherein low-temperature exhaust heat is used as a heat source for heating the hydrogen storage alloy to an operating temperature.

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