JPS59227701A - Method for selective concentration and separative purification of hydrogen gas - Google Patents

Abstract

PURPOSE:To obtain concentrated hydrogen gas or high-purity hydrogen gas economically, in high efficiency, by treating a hydrogen-containing mixed gas by a pressure-cycle process using a composite of zeolite and activated carbon. CONSTITUTION:A calcined composite of zeolite and activated carbon is used for refining crude hydrogen gas containing various kinds of hydrocarbon vapors and inorganic gases to high-purity hydrogen gas. Fine powder of A type synthetic zeolite is mixed with equal amount of the powder of activated carbon, added with bentonite as an inorganic binder, kneaded under wet condition with water and methyl cellulose, dried, and calcined to obtain an activated composite wherein the ratio of bentonite to activated carbon is 0.25-8.0. A gaseous mixture 53 containing about 50% of H2 is supplied to a plurality of adsorption columns 46- 50 packed with the composite as adsorbent, and the adsorption and desorption of the impurities are repeated by repeating the increase, retention and decrease of the pressure of the supplied gas in the course of passing through the columns. A concentrated high-purity H2 gas 55 is obtained as the product.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method for selectively concentrating and separating and purifying hydrogen gas using an adsorption method. More specifically, the present invention provides an economical method for obtaining high purity hydrogen by treating a gas mixture containing hydrogen gas using a so-called pressure cycle method (hereinafter referred to as PSA).

(b) Prior art Gas sources containing hydrogen are widely available in many industrial fields, and from the industrial standpoint of energy recovery, it is difficult to use them as a raw material gas to concentrate hydrogen, or to separate and purify it. It is also very meaningful.

There are many raw material gases that can be used as hydrogen sources, including waste gas, but their compositions are complex. The hydrogen raw material gas contains various hydrocarbons such as CI4. C2Ht, , C
Gases such as 3He, C2H4, C2+12, Co, Co2, SO2, N2, NH3,
In many cases, inorganic gases such as t20 are included. The composition of a raw material gas source useful as a hydrogen source is extremely complex, and in order to economically purify and concentrate hydrogen gas by adsorption, it is necessary to select an effective adsorbent and use it. It is also technologically important to establish highly efficient hydrogen purification and concentration processes.

(c) Objective The main object of the present invention is to provide a method for selectively concentrating and separating and purifying hydrogen gas, which can efficiently obtain high-purity hydrogen gas.

(D) Structure The method for selectively concentrating or separating or purifying hydrogen gas according to the present invention includes at least one step in selectively concentrating, separating, or purifying hydrogen in a mixed gas containing hydrogen by an adsorption method. It mainly consists of a fired product of a composite of zeolite (Z)--active U (A), which has selective adsorption properties for one component, and the weight ratio of Z/A is in the range of 0.25 to 8.0. By passing the mixed gas under pressure through an adsorption bed filled with an activated adsorption material in the interior, impurity components are selectively adsorbed and removed, and hydrogen gas is concentrated and purified to produce product gas. In the first adsorption step, the adsorption bed under pressure after the end of the first step is connected to the adsorption bed that has completed the pressurization step with the product hydrogen gas that constitutes the hydrogen concentration system, and the inter-bed pressure is The second step is the so-called pressure equalization step, in which the hydrogen-enriched part released in the cocurrent direction from the former is collected in the cocurrent direction to the latter and used for pressurization in the same method. , a third depressurization step in which the adsorption bed after the second step is depressurized in the countercurrent direction and maintained near atmospheric pressure to release residual gas in the bed, and the bed is further evacuated in the countercurrent direction to a low vacuum. and at least 2
4th evacuation step to maintain the temperature at 0.00 Torr or less; a combined step of exhausting the adsorption bed that has completed the same step at a pressure of at least 2.0 Torr or less and cleaning (purging) with hydrogen gas; A fifth step of pressurizing the product hydrogen gas in a countercurrent direction with the product hydrogen gas on the bed after completing the step; a sixth step of pressurizing the bed after the step in the countercurrent direction; The pressure between the beds is averaged by connecting the adsorption bed under pressure after the completion of the adsorption process described above, and the hydrogen gas enriched part released from the latter bed in the substream direction is used to pressurize the former bed. The so-called seventh inter-bed pressure averaging step is used as a gas in the co-current direction, and after the completion of the seventh step, a raw material gas containing hydrogen is introduced in the co-current direction to the adsorption bed to maintain a predetermined adsorption pressure. The present invention is characterized in that a cycle consisting of eight steps is carried out, including an eighth step of pressurizing the raw material gas.

Specifically, when carrying out this method, the zeolite (Z)-activated carbon (A) complex (Z
/A=0.25 to 8.0)), each step constituting the cycle of the present invention may be sequentially carried out under preferable conditions.

The cycle configuration of the present invention is summarized as follows.

"Adsorption process - Pressure equalization release process (co-current direction) - Depressurization process (counter-current direction) - Exhaust process (counter-current direction) - Exhaust/purge process (
Countercurrent direction) - Product hydrogen gas pressurization process (countercurrent direction) - Equal pressure pressurization process (cocurrent direction) - Raw material hydrogen gas pressurization process (cocurrent direction)" However, if the above cycle configuration is used. The direction of gas flow within the bed shown in parentheses for each step is based on the direction of flow within the bed during the adsorption step of raw material hydrogen gas. Furthermore, as mentioned above, pressure equalization is an operation to average the inter-bed pressure, and pressure equalization release is the release of gas during pressure equalization operation, and pressure equalization is the operation of the gas released during pressure equalization operation. It represents pressurization.

(E) Examples Continuously and efficiently according to the method of the present invention, at least 99%
．． For the purpose of obtaining 4% or more hydrogen, the cycle consisting of the eight steps described above may be carried out under conditions suitable for each adsorption bed constituting the hydrogen concentration system. In the first adsorption step, the regenerated adsorption bed is maintained at a predetermined adsorption pressure, and impurity components in the raw hydrogen gas are selectively adsorbed and removed to at least 99.9%.
This is a process of concentrating and refining product hydrogen gas of 4% or more, usually 99.9% or more, and taking it out of the hydrogen concentration system as product gas. The adsorption pressure in the main adsorption step is at least 3 kg.
It is preferable to maintain it at or above /cJ・G. Increasing the adsorption pressure has the advantage of increasing the processing capacity of crude hydrogen gas and increasing the amount of hydrogen product per unit time, but on the other hand, the high pressure operation of PSA requires less power consumption than its low pressure operation. It tends to increase.

If pressurized gas can be used as the crude hydrogen gas source, this will not be a problem.

Now, in the adsorption process mentioned above, after the hydrogen mixed gas is processed under pressure and hydrogen gas of a certain purity is extracted as product hydrogen gas, a portion with higher hydrogen purity than the raw material gas remains in the adsorption bed. Since there is a significant amount of gas present, it is necessary to recover this hydrogen-enriched portion to the pond bed to increase the yield. For this purpose, the bed that has completed the above adsorption process and the bed that constitutes the hydrogen concentrating system and that has already completed the pressurization process with product hydrogen gas are connected to each other, and a co-current flow is started from the former bed. An operation is carried out in which the gaseous components released in the direction are recovered in the co-current direction as gas for pressurizing the latter bed. For example, with the cycle configuration of the present invention using crude hydrogen gas containing about 50% hydrogen as a raw material, the adsorption pressure is set to 4. kg/ca・G and operates under normal conditions to extract more than 99.9% of hydrogen as product hydrogen gas with a yield of 80%.
In the SA system, the equilibrium pressure at the end of the above-mentioned pressure equalization step (second step) is usually around 1.6 to 2.0 kg/c/g.

The bed, which has undergone the above-mentioned pressure equalization discharge treatment, then enters a third countercurrent depressurization step for its regeneration. This process is a preliminary step before entering the exhaust process, and in this process, the pressure in the bed is mechanically reduced by simply opening the valve to maintain the pressure in the bed near atmospheric pressure. It is being implemented. The gaseous components released in this step are released outside the hydrogen concentrating system without being recovered. Subsequently, a fourth evacuation step is performed in which the inside of the bed is evacuated in a countercurrent direction using a vacuum pump. In this case, preliminary regeneration of the bed is carried out, so the degree of vacuum in the bed does not necessarily need to be high, and in consideration of the economy of power, this method uses at least 200 torr.
The most preferable range is 150 torr.
r or less. After completing the above steps, the inside of the bed is regenerated using a combination of countercurrent exhaust and purge, the so-called fifth phase of exhaust and purge.
The process is carried out.

In this case, the amount of hydrogen gas used for purging will naturally vary depending on the degree of bed evacuation. For example, in order to achieve a purity of product hydrogen gas of 99.9% using the method of the present invention and to maintain a hydrogen yield of at least 75%, the exhaust gas in the above process must be reduced to 10%.
When carried out at around 0 torr, the amount of hydrogen in the purge used in conjunction with this is preferably 30% or less of the amount of product hydrogen gas, and the most desirable purge amount is in the range of 7 to 25%. By carrying out the fifth exhaust/purge step as described above, the bed regeneration is completed.

Next, in the sixth product hydrogen gas pressurization step, a part of the product hydrogen gas is introduced into the bed in a countercurrent direction to perform pressurization. By performing this operation, some impurity components remaining in the bed move closer to the entrance of the bed and form an adsorption zone, which is effective in preventing irregular diffusion of impurity components. be. Subsequently, a seventh equalization pressurization step is carried out in which the bed is pressurized in the cocurrent direction using the gas in the hydrogen enrichment section released in the cocurrent direction from within the bed in the second step of pressure equalization release described above. The floor becomes even more pressurized.

The eighth raw material hydrogen gas pressurization step is performed on the bed that has completed the seventh step. That is, the raw material hydrogen gas is introduced in a parallel flow direction so that the inside of the bed is ultimately maintained at a predetermined adsorption pressure.

In the seventh and eighth steps described above, the bed, which is kept under pressure with the product hydrogen gas, is pressurized in the cocurrent direction with gases in the order of hydrogen purity, so that the adsorption zone of impurity components is Disturbances are prevented as much as possible.

Figure 1 shows the zeolite-activated carbon complex used for hydrogen purification.
As an example of using this as a concentrator and specifically carrying out purification and concentration of hydrogen in a fully automatic manner using the PSA method of the present invention which consists of 8 steps, the arrangement of a hydrogen concentration system with a 5-column configuration with 4-minute switching is shown. The figure shows. Further, related steps are shown in Table 1.

The process for the adsorption tower 46 will be explained below.
Valve 1 and valve 2 are opened for ~240 seconds, crude hydrogen gas is introduced into the adsorption tower 46 under pressure through raw material gas piping 53, and product gas is taken out through product hydrogen gas piping 55.

During the time period 240 to 270 seconds, the valve 3 opens and the adsorption tower 46
After hydrogen pressurization, the adsorption tower 48 is pressure-equalized, and the hydrogen-enriched gas is recovered into the adsorption tower 48.

Between 270 and 330 seconds, valve 4 opens and adsorption tower 46
is depressurized countercurrently to atmospheric pressure.

The valve 5 is opened for a time period of 330 to 570 seconds, and the adsorption tower 46 is evacuated in the countercurrent direction to a predetermined pressure using the vacuum pump 51.

During a period of time 570 to 810 seconds, valves 6 and 7 are opened, and the adsorption column 46 is flushed countercurrently with a portion of the hydrogen product gas while maintaining a predetermined pressure using the vacuum pump 52.

During the time period 810 to 960 seconds, the valve 8 is opened and the adsorption tower 46
is pressurized to a predetermined pressure using a portion of the product hydrogen gas.

During a time period of 960 to 990 seconds, the valve 30 is opened, the pressure of the adsorption tower 46 is equalized with the tower 49 where adsorption has been completed, and hydrogen-enriched gas is recovered.

During the time period of 990 to 1200 seconds, the valve 9 is opened and the adsorption tower 46 is pressurized with the raw material gas to the adsorption pressure.

The above eight steps are shown in Table 1. The five tower processes are carried out in parallel while being staggered in a time sequence.

Next, specific examples of the present invention will be described, but the present invention is not limited to these examples unless the gist thereof is exceeded.

First, a method for producing an adsorbent used for purifying and concentrating hydrogen gas according to the present invention will be explained.

A-type synthetic zeolide fine powder (1,08Na20
・81203 ・2.02Si02 ・xH2O) 5 kg of the dried product was collected as its anhydride, and activated carbon powder (Fujisawa Pharmaceutical: B-CW; average particle size 100 pm) was collected.
) 5 kg was added and mixed using a V-mixer. Next, to the obtained mixture, 20% (2 kg) of bentonite fine powder was added as an inorganic binder and 2% methyl cellulose was added as an organic binder [7,000 to 10,000 cp].
s (2% aqueous solution: 20° C.)] and wet mixing was performed for 3 hours and 30 minutes in the presence of water.

The moisture content during wet mixing was 44.3%. The mixture obtained by the darning method was molded into 1/8 pellets using a molding machine, and then dried at 100-1]0"C. Subsequently, a flasher was used to reduce the length of the dried pellets. After adjustment to obtain a certain length distribution, the sample was finally calcined at 470 to 475°C for 3 hours and 30 minutes in a tin atmosphere to be used in the hydrogen enrichment example of the present invention.
A fired body of /8" pellets was obtained.

The weight ratio of zeolite (Z) and activated carbon (8) of the 1/8" pellets (calcined) for hydrogen purification and concentration obtained in this way was Z/A-0.96, and its average hardness was It was 7.l3kg/bellet.

Therefore, in this example, a hydrogen purification/concentration agent mainly composed of a composite of zeolite (Z) and activated carbon (8) (1/8" pellet adsorbent Z/A- 8 of the present invention already described using
Hydrogen purification and concentration was carried out using the PSA method, which consists of several steps.

FIG. 2 is a layout diagram of a manual hydrogen concentration test device with a two-column configuration used in this test.

For the adsorption tower No. 1 (inner diameter: 42.6 mm; length: 2,000 mm), the hydrogen purifying agent l/8" obtained from the above production example was used.
Each group was loaded with 1.47 kg of pellets.

Superheated nitrogen gas (150°C) was introduced from the bottom of the adsorption tower to activate the inside of the tower until the dew point of the gas released from the top of the tower reached 165°C.

Raw material hydrogen gas used in this example (Hz = 54.5%
;CH4=19.3%i C2H6=19.2%1c
3H1]-5,8%; C4If to =1.2%
) is introduced into an adsorption tower 61 having a two-column configuration through a pipe 71. 62 is a flow meter for product hydrogen gas, 63 is a flow meter for pressure reduction, 64 is a wet flow meter, 65 is a hydrogen analyzer, 66 is a vacuum pump, 67 is a compound meter, and 68 is a precision pressure gauge. .

The hydrogen for pressurization required in the hydrogen gas concentration process of the present invention is stored in 69 hydrogen cylinders, which is equivalent to 70
It is designed to be introduced into a two-column adsorption tower through a charge tank. Reference numeral 72 is a pipe for discharging exhaust gas from the vacuum pump. In this example, the above-mentioned "adsorption process - pressure equalization release process (cocurrent direction) - depressurization process (countercurrent direction) - exhaust process (countercurrent direction) - exhaust/purge process (countercurrent direction) - product hydrogen gas addition" A cycle consisting of 8 steps of "pressure step (countercurrent direction) - equal pressure pressurization step (cocurrent direction) - raw material hydrogen gas pressurization step (cocurrent direction)" was sequentially carried out.

Details of the examples are shown in Table 2.

Examples 1 to 3 are cases where the pressure of the adsorption tower was maintained at 4 kg/cA·G, and the degree of vacuum inside the tower was maintained at 100 torr in both the exhaust process and the exhaust/purge process. In this case, the pressure inside the column at the end of the pressure equalization step is about 1.
It was 8 kg/cf・G. In addition, the amount of hydrogen used in the hydrogen gas pressurization process is 2. IN<! Met.

The yield of hydrogen gas product at the end of one cycle of the above eight steps was 78.1% in Example 1, 82.2% in Example 2,
Further, in Example 3, it reached 85.0%. As stated in all Examples, the hydrogen gas purity reached 99.8%. In addition, the amount of product hydrogen gas per 1 kg of the hydrogen purifying agent used in the present invention was large, showing 23 to 25 units.

These results clearly demonstrate that the hydrogen purification and concentration method of the present invention, which combines the above-mentioned purification agent and PSA, exhibits high efficiency.

Next, Examples 4 and 5 are cases in which the adsorption pressure is maintained at 4 kg/cJ-G, and the degree of vacuum in the column is set at 200 torr in both the exhaust process and the exhaust/purge process.

The relevant detailed data are listed in Table 2. 2 above
In the Examples, the yield of the product hydrogen gas was 74 to 79%, and the purity of the obtained hydrogen gas reached 99.5% in all cases.

In the above-mentioned embodiment, the selective concentration or separation/purification of hydrogen gas mainly consists of a fired product of a zeolite (Z)-activated carbon (A) composite, whose Z/A weight ratio is 0.25. Although it has been explained that an adsorption bed filled with an activated adsorption material within the range of ~8.0 is used, the following may be used instead of this bed depending on the type and composition of the hydrogen raw material gas to be treated. May be matched with floor configuration.

That is, the method of the present invention is carried out using a bed made of the above-mentioned zeolite-activated carbon composite as the main bed, and a bed filled with silica gel, alumina gel, or silica gel and alumina gel as a side bed. It is also possible to obtain 99.9% or more hydrogen gas. In this case, in order to increase the efficiency of the adsorption bed, the amount of the adsorbent such as silica gel or alumina gel used in the side bed structure should be 30% or less of the zeolite-activated carbon composite adsorbent used in the main bed structure. is also appropriate.

(f) Effects According to the method for selectively concentrating and separating hydrogen gas according to the present invention, the following effects can be obtained.

ta> It is extremely easy to obtain at least 99.5% or more hydrogen by processing a crude hydrogen mixed gas (Hz #50%), and the hydrogen yield can be increased.

(b) The yield of purified hydrogen gas per unit weight of the adsorbent made of the zeolite-activated carbon composite used can be extremely high (for example, the hydrogen yield is 19 to 24 Nil).
l/kg adsorbent).

(C1 Since the present invention uses an adsorption bed filled with a zeolite-activated carbon composite, compared to an adsorption tower composed only of zeolite or an adsorption tower composed of two layers of activated carbon and zeolite, Thermal conductivity within the column is significantly improved, and the temperature distribution within the column is also more uniform.Therefore, the hydrogen:a pongee yarn based on PSA proposed in the present invention has the advantage that extremely stable operation can be performed completely automatically. There is.

(d) The true density of activated carbon (A), which is the material constituting the hydrogen purification adsorbent used in the present invention, is usually 1.9 to 2.2 g /
c+J (apparent density: 0.8 to 1.0 g/cJ), while the true density of natural or synthetic zeolite l-(Z) is usually 2.0 to 2.3 g/cJ (apparent density: 0
．． 8 to 1.3 g/cJ), so after carrying out wet mixing using a mixture of both in the presence of a binder, molding,
By drying and firing, a preferred composite composition in which activated carbon and zeolite are uniformly dispersed can be obtained.

Therefore, the zeolite-activated carbon composite adsorbent used in the hydrogen concentrating system of the present invention has a high apparent density and mechanical strength.

In addition, the ignition point increases with the content of zeolite, so it is safer to use than when the adsorbent is made of activated carbon alone.

fe) Since the activated carbon-zeolide constituting the composite adsorbent is uniformly dispersed, the adsorption bed made of this adsorbent has good thermal conductivity. Therefore, according to the present invention, highly efficient PSA operation is possible.

(f1) The adsorption and desorption of gas in the adsorption bed composed of the active substance-zeolide complex used in the present invention is carried out rapidly. In addition, it is easy to regenerate it. There is an advantage that the time required for a cycle consisting of steps can also be shortened.In other words, according to the method according to the present invention, hydrogen purification and concentration efficiency can naturally be increased.

(g1) Since the present invention uses an adsorption bed made of an activated carbon-zeolide composite, gas adsorption to desorption is more rapid and uniform throughout the bed compared to a zeolite-only bed or a two-layer bed of zeolite and activated carbon. This has the advantage of increasing the efficiency of the floor.

Therefore, compared to the zeolite-only bed or the 2M bed of zeolite and activated carbon, the adsorbent used in the present invention has
This has the effect of further shortening the length of MTZ (mass transfer thinner) required when separating, purifying, or concentrating hydrogen from a hydrogen-containing mixed gas.

Therefore, when actually refining and concentrating hydrogen mixed gas, it is recommended to use the aforementioned zeolite-only bed or the 2N bed of zeolite and activated carbon.
The adsorption bed having the above-mentioned structure used in the present invention has the advantage of being able to further reduce the required height of the bed. This has the advantage of reducing the floor resistance, which is seen in the exhaust process during gas processing and purification, in the PSA system, for example, and reduces power consumption. Therefore, according to the present invention, where a hydrogen concentration system is constructed from this adsorption bed and the PSA No. 1 is repeatedly cycled through eight steps, economical hydrogen concentration with low power consumption is possible.

[Brief explanation of drawings]

Figure 1 shows the 8-step PSA of the present invention for hydrogen purification and
As an example of concretely carrying out concentration in a fully automated manner, the layout of a hydrogen concentration system with five columns is shown. A layout diagram of a two-column configuration device during implementation is shown. 1 to 45... valves, 46 to 50 adsorption towers, 51... vacuum pumps, 52... vacuum pumps for exhaust/purge,
53-57... Piping, 61... Adsorption tower, 62...
Flowmeter for product gas, 63...Flowmeter for pressure reduction, 64
...Wet flow meter, 65...Hydrogen analyzer, 66...
Vacuum pump, 67...Compound gauge, 68...Precision pressure gauge, 69...Hydrogen cylinder for pressurizing hydrogen, 70...Hydrogen charge tank, 71.72...Piping. Patent applicant: Japan Electronic Materials Co., Ltd. Agent: Zenji Hagiwara Patent attorney: Takaharu Ohnishi

Claims (2)

[Claims] (1) When selectively concentrating or separating and purifying hydrogen in a mixed gas containing hydrogen by an adsorption method, mainly zeolite (Z)-activated carbon (A) that has selective adsorption properties for at least one component of the mixed gas The adsorption bed filled with an activated adsorption material consisting of a calcined composite of which Z/A weight ratio is within the range of 0.25 to 8.0 is mixed while maintaining the adsorption bed under pressure. The first adsorption step in which impurity components are selectively adsorbed and removed by passing the gas through, and the hydrogen gas is concentrated and purified to be taken out as a product gas, the adsorption bed under pressure after the first step and the hydrogen concentration system. The adsorption bed that has completed the pressurization process using the product hydrogen gas constituting the adsorption bed is connected to average the inter-bed pressure, and the hydrogen-enriched part released from the former in the cocurrent direction is parallel to the latter. In the second step of the so-called pressure equalization step, which is the averaging step used for pressurization in the same method, the adsorption bed after the second step is depressurized in the countercurrent direction and maintained near atmospheric pressure. a third depressurization step in which residual gas in the bed is released by
a fourth evacuation step to maintain the pressure below 0.00 torr; at least 2
A fifth step in which a combined step of exhausting at 00 Torr or less and cleaning (purging) with product hydrogen gas is carried out in the countercurrent direction.
a sixth product hydrogen gas pressurization step in which the bed that has completed the fifth step is pressurized in a countercurrent direction with product hydrogen gas; a bed that has completed the sixth step and the aforementioned adsorption step; After completion of the adsorption process, the adsorption bed under pressure is connected to average the inter-bed pressure, and the hydrogen gas enriched part released from the latter bed in the cocurrent direction is used as the pressurizing gas for the former bed. The so-called seventh inter-bed pressure averaging step used in the 7th step, and the 7th step in which a raw material gas containing hydrogen is introduced into the adsorption bed in parallel flow direction and pressurized to a predetermined adsorption pressure. 1. A method for selectively concentrating and separating and purifying hydrogen gas, characterized by carrying out a cycle consisting of 8 steps of pressurizing raw material gas. (2) The adsorption pressure in the first adsorption step is at least 3 kg.
/cIII-G or higher, and the fourth evacuation step was
Both are carried out until the inside of the bed is maintained at a vacuum level of 150 torr or less, and further, the combined process of exhausting and cleaning (purging) in the fifth step is carried out so that the inside of the bed is maintained at a vacuum level of at least 150 torr (torr) or less. A method for selectively concentrating and separating and purifying hydrogen gas according to claim 1.