JP2001347125A - Method or manufacturing high-purity gas by pressure fluctuation adsorption apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing high-purity gas which reduces an installation cost and equipment installationa area and is capable of solving the degradation in the recovery rate of the high-purity gas, such as high-purity hydrogen, which is a problem on the adsorption by fewer adsorption columns by using a two-column type PSA apparatus which is made compact. SOLUTION: This method for manufacturing the high-purity gas by the pressure fluctuation adsorption apparatus is characterized in that, when one column of the two-column type pressure fluctuation adsorption apparatus is in an adsorption process step, the respective process steps of a pressure reducing process step, a blowdown process step, a purging process step and a boosting process step are successively carried out in the other column and the gas substantially not containing the impurities discharged in the post steps of the pressure reducing process step and the purging process step or containing the impurities to a lesser extent is circulated to gaseous raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity gas using a pressure fluctuation adsorption apparatus (hereinafter, referred to as a PSA apparatus). More specifically, two adsorption towers filled with an adsorbent are provided to remove impurities from a raw material gas. The present invention relates to a method for producing high-purity gas using a two-column PSA apparatus for producing high-purity gas by adsorbing and removing hydrogen, and in particular, producing high-purity hydrogen (hereinafter referred to as high-purity hydrogen) from hydrogen-containing gas. The present invention relates to a manufacturing method which is most suitable for a relatively small device.

[0002]

2. Description of the Related Art Hydrogen is a basic raw material often used as a reducing gas or hydrogenated gas in the metal industry, oil and fat industry, petroleum industry, semiconductor industry, and the like. In recent years, hydrogen has also been used as a fuel for fuel cells. I have. In particular, high purity hydrogen of 99.99 mol% or more, which contains almost no impurities, is used for hydrogen used in the semiconductor industry, fuel cells, and the like.

[0003] High-purity hydrogen is produced by removing impurities from a hydrogen-containing gas. As the hydrogen-containing gas, various kinds of hydrocarbons such as natural gas, city gas, naphtha, kerosene or methanol are used as raw materials. After desulfurizing these hydrocarbons as necessary, reforming equipment using a Ni-based or Ru-based catalyst, reformed gas produced by cracking or reacting with steam, or coal is distilled in a coke oven. The coke oven gas manufactured by the method is used.

[0004] The hydrogen-containing gas such as the reformed gas and coke oven gas contains methane, carbon monoxide, carbon dioxide, and the like as impurities, so that highly purified hydrogen can be produced. To do so, it is necessary to remove those impurities to an extremely low content. As a conventional apparatus for producing high-purity hydrogen, a hydrogen separation membrane apparatus in which only hydrogen is permeated by a hydrogen separation membrane to separate it from impurities is also used. A PSA device (hereinafter referred to as a hydrogen PSA device) for producing high-purity hydrogen by absorbing and removing impurities in a hydrogen-containing gas is often used.

In the hydrogen PSA apparatus, a hydrogen-containing gas is supplied at a high pressure to an adsorption tower filled with an adsorbent, impurities are adsorbed and removed by the adsorbent at a high pressure, and hydrogen that is difficult to adsorb is extracted from the adsorption tower. To remove the impurities adsorbed on the adsorbent by a depressurizing step, a blow-down step and a purging step, and regenerate the adsorbent by discharging the off-gas out of the system. This is an apparatus capable of continuously producing high-purity hydrogen as a whole apparatus by sequentially repeating the process between a plurality of adsorption towers. To produce large-capacity high-purity hydrogen, a four-column hydrogen PSA device consisting of four or more adsorption towers is mainly used. A three-column hydrogen PSA device comprising a column adsorption tower is also used.

FIG. 3 is a schematic diagram of an operation sequence in a three-tower hydrogen PSA apparatus comprising three adsorption towers, tower A, tower B, and tower C. In tower A, impurities in a hydrogen-containing gas are shown. In the adsorption step of adsorbing water, carbon dioxide, carbon monoxide, methane, etc. and recovering the non-adsorbed hydrogen as high-purity hydrogen, in the B tower, each of the pressure reduction step, pressure equalization step, and blowdown step is performed. The steps are sequentially performed. In the tower C, the steps of the purging step, the equalizing step, and the pressure increasing step are sequentially performed.

Before the adsorption of impurities becomes saturated and breaks down in the adsorption step of the tower A, the steps between the respective towers are switched by automatic control of the control valve, and the operation is sequentially repeated, so that the apparatus as a whole is obtained. High-purity hydrogen is produced continuously.

[0008]

In the PSA apparatus, the smaller the number of adsorption towers, the more compact the apparatus, the lower the equipment cost, and the simpler the operation control method, which is preferable. If the number of columns is reduced, it becomes difficult to recover high-purity gas in the gas discharged in the pressure reduction step, blow-down step, and purge step, so that there is a problem that the recovery rate of high-purity gas decreases. By the way, hydrogen PSA
In order to produce high-purity hydrogen from a hydrogen-containing gas produced by decomposing natural gas, the operating pressure is 0.7Mp.
When operated at aG, a high-purity hydrogen recovery rate of 65 to 70% in the three-tower system and 70 to 75% in the four-tower system is achieved.

The present invention has been made in view of the above-mentioned problem, and the PSA apparatus is further reduced in size by making the number of adsorption towers of two columns smaller than that of a three-column PSA apparatus. In order to provide a method for producing a high-purity gas using a two-tower PSA apparatus, which can reduce the area and solve the problem of a reduced recovery rate of a high-purity gas such as high-purity hydrogen, which is a problem caused by a small number of adsorption towers. It was made.

[0010]

The gist of the present invention for achieving the above object is as follows.
In a two-column pressure fluctuation adsorption device that provides two adsorption columns filled with an adsorbent and removes impurities from a raw material gas to produce a high-purity gas, when one of the two columns is in the adsorption step, In other towers, the pressure reduction step, blowdown step,
And a pressure-reducing step. In the pressure-reducing step, a gas containing almost no impurities is recovered from the high-purity gas recovery side by reducing the pressure to a pressure with almost no outflow of impurities, and circulated to the raw material gas. And / or stored in a gas holder. In the blow-down step, the pressure is further reduced and a gas containing a large amount of impurities is extracted as an off-gas from the source gas supply side. In the purging step, the high-purity gas and And / or supplying a gas containing almost no impurities, extracting a gas containing a large amount of impurities discharged in the preceding stage as an off-gas from the raw material gas supply side, and circulating a gas containing a small amount of impurities discharged in the subsequent stage to the raw material gas. The pressure fluctuation is characterized by supplying a high-purity gas and / or a gas containing almost no impurities from the high-purity gas recovery side and increasing the pressure. A process for producing a high-purity gas by wearing device. Note that a gas containing almost no impurities means that the impurity concentration is 1 mol% or less, preferably 0.1 mol%.
The following gases, and a gas having a small amount of impurities, mean a gas having an impurity concentration of 10 mol% or less, preferably 1 mol% or less. Further, the gas containing a large amount of impurities means a gas containing more impurities than the above-described impurity concentration in each step. By the manufacturing method having the above configuration, the PSA device can be made compact, the equipment cost and the equipment area can be reduced, and the reduction in the recovery rate of high-purity gas such as high-purity hydrogen, which is a problem with a small number of adsorption towers, can be solved. The high-purity gas recovery rate can be improved. In particular, it is suitable for producing high-purity hydrogen by absorbing and removing impurities from a hydrogen-containing gas.
This is an optimal production method for a small-sized hydrogen PSA device having a high-purity hydrogen production capacity of 10 to 40 Nm3 / H.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a driving seat according to an embodiment of the present invention.
FIG. 2 is a schematic view of a cans, FIG. 2 is a system diagram of a two-column hydrogen production pressure fluctuation adsorption apparatus according to an embodiment of the present invention, and FIG. FIG.

In FIG. 2, reference numeral 1 denotes a high-purity hydrogen recovery pipe 7a connected to a high-purity hydrogen recovery base pipe 7 at an upper part and a lower source gas supply pipe 6a branched from the source gas supply base pipe 6.
Is connected to the tower A. Reference numeral 2 denotes a high-purity hydrogen recovery pipe 7b connected to a high-purity hydrogen recovery base pipe 7 at the lower part and a high-purity hydrogen recovery pipe 7 at the upper part. Is the connected tower B. Inside of tower A 1 and tower B 2
Adsorbent beds 3a and 3b for adsorbing and removing impurities in the hydrogen-containing gas as the raw material gas are provided, respectively. In the production of high-purity hydrogen, the activated carbon layer is mainly moved from the upstream side to the downstream side in the flow direction of the raw material gas. And an adsorbent bed 3a, 3b laminated in the order of a zeolite layer, but depending on the composition of a raw material gas such as a hydrogen-containing gas containing a large amount of water, in order to protect activated carbon and zeolite from the influence of moisture. In some cases, an activated alumina layer may be provided before the adsorbent bed 3 in the same adsorption tower or as a separate adsorption tower.

Reference numeral 4 indicates that the raw material gas is pressurized and A tower 1 and B
Compressors 5 are supplied to the tower 2, respectively. Reference numeral 5 is an off-gas storage tank for storing an off-gas containing a large amount of impurities recovered in a blow-down process or a purge process as an adsorbent regeneration process. The off-gas can be used as a fuel gas for a reformer for producing a hydrogen-containing gas. Numeral 12 is a gas holder for storing a gas containing almost no impurities collected in the pressure reduction step,
It can be used as a purge gas in the purge step or a pressurized gas in the pressure step.

Reference numeral 6 designates a compressor-4, and feeds the raw material gas through the raw gas supply pipes 6a and 6b to the towers A and B.
Source gas supply base pipes to be supplied to the tower 2 respectively, and reference numeral 7 denotes the tower A 1
And a high-purity hydrogen recovery pipe for recovering high-purity hydrogen extracted from the high-purity hydrogen recovery pipes 7a and 7b of the B tower 2 respectively. Reference numeral 8 denotes a high-purity hydrogen recovery pipe of the A tower 1 and the B tower 2. 7
In order to circulate a gas containing almost no impurities discharged in the depressurizing step from the hydrogen discharge pipes 8a and 8b branched from the a and 7b to the raw material gas, the gas is connected to the raw gas supply base pipe 6 in front of the compressor-4. The hydrogen circulation base pipe 8 is connected to the reduced pressure gas recovery base pipe 11 in order to store in the gas holder a gas substantially containing no impurities collected in the pressure reduction step. In order to supply high-purity hydrogen and / or gas containing almost no impurities used in the pressurization step from the hydrogen discharge pipes 8a and 8b to the A tower 1 and the B tower 2, respectively, it is also connected to the high-purity hydrogen recovery base pipe 7. ing.

Reference numeral 9 denotes off-gas discharge pipes 9a, 9b branched from the raw gas supply pipes 6a, 6b of the tower A 1 and the tower B 2.
Of the off-gases discharged respectively in the purging process, a gas containing a small amount of impurities discharged in the latter stage is circulated to the source gas, so that an off-gas circulation base tube connected to the front stage of the compressor-4 of the source gas supply base tube 6 However, in order to supply the gas containing a large amount of impurities discharged in the previous stage of the blow-down step and the purge step to the off-gas storage tank 5 as an off-gas,
It is also connected to the off-gas discharge base pipe 10.

In the hydrogen PSA apparatus having the above structure, as shown in FIG. 1, in two adsorption towers, the adsorption of impurities in the adsorption step in one tower (A tower) is saturated and breaks through. Before the automatic control of the control valve, the pressure-reducing step, the blow-down step, the purging step, and the pressure-increasing step are sequentially advanced, and the step is switched to another tower (B tower) in which the regeneration operation has been completed. The regeneration operation of the adsorbent is performed, and the adsorption step in the tower B is performed. By repeating the operation between the two columns, high-purity hydrogen can be produced continuously.

A method for producing high-purity hydrogen by adsorbing and removing impurities from a hydrogen-containing gas using the two-column hydrogen PSA apparatus will be described in detail below with reference to FIG. Since they are the same, the adsorption step in the tower A
In the column, the steps of pressure reduction, blowdown, purge, and pressure increase for regeneration are described. As a hydrogen-containing gas as a raw material gas, various hydrocarbons such as natural gas, city gas, naphtha, kerosene, and methanol are used as raw materials, and after desulfurizing the hydrocarbons as necessary, Ni-based or Ru-based gas is used.
Using a reformed gas mainly composed of hydrogen produced by cracking or reacting with steam in a reformer using a system catalyst, or a coke oven gas produced by dry-distilling coal But not limited to those hydrogen-containing gases.

(Adsorption Step) The above-mentioned hydrogen-containing gas is pressurized by the compressor-4 of the source gas supply base pipe 6, and the valve V1 of the source gas supply base pipe 6, the valve V2 of the high-purity hydrogen recovery pipe 7a and the high-purity hydrogen The valve V12 of the recovery base pipe 7 is opened to supply the raw gas from the raw gas supply pipe 6a to the lower part of the tower A, and the adsorbent bed 3a is circulated in an upward flow, so that the activated carbon layer mainly contains water and carbon dioxide. And methane are adsorbed and removed, carbon monoxide and the like are adsorbed and removed in the zeolite layer, and all impurities in the hydrogen-containing gas are adsorbed and removed in the entire adsorbent bed 3a. Hydrogen that is not adsorbed by the adsorbent is supplied from a high-purity hydrogen recovery base pipe 7 to a high-purity hydrogen storage tank (not shown) through an upper high-purity hydrogen recovery pipe 7a, and is stored as product high-purity hydrogen.

When the step of adsorbing impurities is performed in the tower A and high-purity hydrogen is being produced, a regeneration operation for recovering the adsorbent adsorption capacity is performed in the tower B 2. (Decompression step)
The valve V8 of the hydrogen discharge pipe 8b and the valve V9 of the hydrogen circulation base pipe 8 are opened, or the valve V8 of the hydrogen discharge pipe 8b and the valve V15 of the reduced-pressure gas recovery base pipe 11 are opened, so that the impurity in the B tower 2 flows out. By reducing the pressure to a pressure at which almost no impurities remain, a gas containing almost no impurities remaining in the B tower 2 is discharged and circulated to the raw material gas or stored in the gas holder 12.

(Blow-down step) The valves V8 and V
9 or V8 and V15 are closed, and the valve V7 of the off-gas discharge pipe 9b and the valve V of the off-gas discharge base pipe 10 are closed.
The valve 13 is opened to further reduce the pressure in the B tower 2, discharge a gas rich in impurities, supply the gas from the hydrogen offgas discharge base pipe 10 to the offgas storage tank 5, and store the offgas.

(Purge step) Next, the valves V7, V
13, while the valve V8 of the hydrogen discharge pipe 8b and the valve V11 of the hydrogen circulation base pipe 8 are opened and the valve 12 is closed, the high-purity hydrogen produced in the tower A
Supply the gas to the tower 2 or open the valve V8 of the hydrogen discharge pipe 8b and the valve V15 of the reduced pressure gas recovery pipe 11 to supply the gas containing almost no impurities recovered in the pressure reducing step to the B tower 2 for adsorption. Purging impurities adsorbed on the agent bed 3b,
The gas containing a large amount of impurities discharged in the previous stage is supplied from the off-gas discharge base pipe 10 to the off-gas storage tank 5 and stored as off-gas. The valve V13 of the off-gas circulation base pipe 9 is opened while the valve V13 is closed to circulate a gas containing less impurities discharged in the subsequent stage to the source gas.

(Pressurizing Step) After closing the valves V7 and V10 and supplying a gas containing almost no high-purity hydrogen or impurities to the B column 2, the B column 2 is pressurized to a predetermined pressure. , The valve V8, V11 or V
8. By closing the valve V15 and stopping the supply of high-purity hydrogen or gas containing almost no impurities, the regeneration operation of the B tower 2 is completed.

In the description of the method for producing high-purity hydrogen, the reference numerals corresponding to the valves in the tower A 1 and the tower B 2 accompanying the switching of the process are as follows. V1: V
5, V2: V6, V3: V7, V4: V8. In addition, the former is the valve number of the tower A1, and the latter is the valve number of the tower B2. Further, the present invention is not limited to the operation in each of the above steps. For example, in the supply of high-purity hydrogen in the purging step or the pressurizing step, the gas produced in another tower is not used as it is, but is supplied from a high-purity hydrogen storage tank by providing a separate piping and a compressor. The gas used in the purging step and the pressure increasing step may be a combination of high-purity hydrogen and a gas containing almost no impurities. Further, a gas containing almost no impurities may be recovered as a high-purity hydrogen product.

As an example of the operating conditions in each of the above steps, when the hydrogen production capacity is 10 to 40 Nm 3 / H, the adsorption time in the adsorption step is 200 to 500 seconds, and the pressure is 0.3 to 0. 98 MPaG, the time of the pressure reduction step is 50 to 1
20 seconds, pressure is 0.2-0.6 MPa, time of blow-down step is 20-100 seconds, pressure is 0-0.2 MPa,
The time for the purging step is 50 to 120 seconds, the time for the pressure raising step is 10 to 60 seconds, and the pressure is 0.3 to 0.98 MPaG. A gas containing almost no impurities is a gas having an impurity concentration of 1 mol% or less, preferably 0.1 mol% or less, and a gas having a small impurity has an impurity concentration of 10 mol% or less.
mol% or less, preferably 1 mol% or less. In addition, the gas containing many impurities is used in each process.
It contains more impurities than the above impurity concentration. Furthermore, the high-purity hydrogen produced is 99.99 mol% or more,
Preferably it is 99.9999 mol% or more, and the high purity hydrogen recovery rate is 65 to 80%.

[0025]

According to the present invention, the PSA apparatus can be made compact, the equipment cost and the installation area can be reduced, and the problem of a low adsorption tower, that is, the reduction in the recovery rate of high-purity gas such as high-purity hydrogen, can be solved. Thus, the high-purity gas recovery rate can be improved. In particular, it is suitable for producing high-purity hydrogen by absorbing and removing impurities from a hydrogen-containing gas, and is a production method most suitable for a small-sized hydrogen PSA device having a high-purity hydrogen production capacity of 10 to 40 Nm3 / H.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an operation sequence according to an embodiment of the present invention.

FIG. 2 is a system diagram of a pressure fluctuation adsorption apparatus for two-column hydrogen production according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an operation sequence in a conventional pressure fluctuation adsorption apparatus for three-column hydrogen production.

[Explanation of symbols]

 1: A tower (adsorption tower) 2: B tower (adsorption tower) 3a, 3b: adsorbent bed 4: compressor 5: off-gas storage tank 6: source gas supply base pipe 7: high-purity hydrogen recovery base pipe 8: hydrogen Circulation base pipe 9: Off gas circulation base pipe 10: Off gas discharge base pipe 11: Reduced pressure gas recovery base pipe 12: Gas holder

Continued on the front page (72) Inventor Kumiko Kato 3-3-1 Minatomirai, Nishi-ku, Yokohama-shi, Kanagawa F-term in Mitsubishi Kakoki Co., Ltd. 4D012 CA07 CB16 CD07 CG01 CJ01 CJ02 CJ06

Claims (1)

[Claims] 1. A two-column pressure fluctuation adsorption apparatus for providing high-purity gas by adsorbing and removing impurities from a raw material gas by providing two adsorption columns filled with an adsorbent, wherein one of the two columns is At the time of the adsorption step, in the other column, each step of the pressure reduction step, the blowdown step, the purge step and the pressure increase step is sequentially performed. In the pressure reduction step, the pressure is reduced to a pressure at which almost no impurities flow out. A gas containing almost no impurities is recovered from the high-purity gas recovery side and circulated to the raw material gas and / or stored in a gas holder. In the purging step, a high-purity gas and / or a gas containing almost no impurities are supplied from the high-purity gas recovery side, and a large amount of impurities are discharged in the preceding stage from the source gas supply side. Extracting the scan as off-gas,
A gas with a small amount of impurities discharged in the subsequent stage is circulated to the source gas, and in the pressurizing step, a high-purity gas and / or a gas containing almost no impurities are supplied from the high-purity gas recovery side to increase the pressure. A method for producing high-purity gas using a pressure fluctuation adsorption device.