JPH0569567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an adsorption device (hereinafter abbreviated as PSA device) that is operated from a mixed gas containing hydrogen sulfide (H ₂ S) by a pressure swing regeneration method. )Using,
Certain gases included, such as hydrogen (H ₂ )
The present invention relates to a method for efficiently removing hydrogen sulfide when recovering hydrogen sulfide.

[Prior art and its problems]

Oil refinery off-gas and liquid-phase hydrogenation circulating gas contain large amounts of hydrogen.

An example of the composition of oil refinery off-gas is: H ₂ 60.0vol% CH ₄ 20.0〃 C ₂ H ₆ 15.0〃 C ₃ H ₈ 4.0〃 C ₄ H ₁₀ 0.7〃 C ₅ H ₁₂ 0.3〃 H ₂ S 200ppm CO ₂ 50〃 H ₂ O saturated Also, examples of liquid phase hydrogenation circulating gas include H ₂ 79.2mol% N ₂ 2.8〃 CO ₂ 0.0〃 CO 8.0〃 Hydrocarbons C-1 7.8mol% C-2 1.2mol% C -3 0.8〃 C-4 0.1〃 C-5 0.03〃 H ₂ S 0.05〃 NH ₃ 0.01〃 Therefore, this hydrogen is recovered as fuel, raw material for chemical synthesis, etc. Generally, a PSA device is often used. However, as is clear from the above composition, hydrogen sulfide coexists in such a mixed gas, and there is a problem that this hydrogen sulfide deteriorates the adsorbent of the PSA device.
That is, hydrogen sulfide adsorbed on an adsorbent such as activated carbon in a PSA device changes to sulfur during desorption and gradually accumulates in the adsorbent, reducing the hydrogen separation performance of the desorbent. Therefore, it is necessary to remove hydrogen sulfide before introducing the mixed gas into the PSA device.

Hydrogen sulfide removal methods include wet desulfurization, activated carbon adsorption, and iron oxide methods.

However, the wet desulfurization method requires complicated equipment and operation. Furthermore, the activated carbon adsorption method has a small removal capacity and is difficult to regenerate. Furthermore, the iron oxide method has the disadvantage that the equipment becomes bulky if it is attempted to remove at a high removal rate. As described above, the removal of hydrogen sulfide is accompanied by various problems, and a simple and highly efficient removal method is required.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The purpose is to provide a purification method that can efficiently remove hydrogen sulfide in a mixed gas with simple equipment and prevent deterioration of the adsorbent in a PSA device. It is characterized by reacting with hydrogen sulfide to form carbonyl sulfide, which facilitates adsorption and desorption.

[Structure of the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings.

The drawing shows an example of an apparatus used in the refining method of the present invention, and is an apparatus for recovering hydrogen from raw material gas such as petroleum refinery offgas or liquid phase hydrogenation circulating gas. First, the raw material gas containing hydrogen sulfide is introduced from the pipe 1 into the compressor 2, where it is pressurized to about 5 to 10 kg/cm ² G. The pressurized raw material gas is added with carbon dioxide from the carbon dioxide source 3 via the valve 4, and then passes through the valve 5a to the one of the two adsorption columns 6a and 6b that is in the adsorption process. Sent to 6a. The amount of carbon dioxide added is in excess of 2 to 3 times the reaction equivalent of hydrogen sulfide so that hydrogen sulfide in the raw material gas is completely converted to carbonyl sulfide. The adsorption cylinders 6a and 6b are operated by switching between the adsorption process and the regeneration process, so that when one is in the adsorption process, the other is in the regeneration process. Further, the adsorption cylinders 6a and 6b are both filled with at least zeolite as an adsorbent, and in addition to this, silica gel or activated carbon, for example, is filled depending on impurities in the raw gas. Hydrogen sulfide in the raw material gas introduced into the adsorption cylinder 6a reacts with excess carbon dioxide in the internal zeolite layer by the catalytic action of the zeolite, and is converted into carbonyl sulfide.

H ₂ S + CO ₂ → COS + H ₂ O This carbonyl sulfide is more stable than hydrogen sulfide, does not precipitate sulfur when desorbed from the adsorbent, is easy to desorb, and completely regenerates the adsorbent. I can do it. Further, impurities other than hydrogen sulfide in the raw material gas, such as heavy hydrocarbons and ammonia, are adsorbed and removed by an adsorbent other than zeolite, such as silica gel.

In this way, impurities are removed in the adsorption column 6a, and the raw material gas containing carbonyl sulfide generated from hydrogen sulfide and remaining carbon dioxide passes through the valve 7b.
It is sent to the PSA device 8. The PSA device 8 consists of a plurality of adsorption columns filled with adsorbents such as activated carbon and molecular sieves, and removes residual impurities in the raw material gas, such as light hydrocarbons, nitrogen, carbon monoxide, carbonyl sulfide, and Carbon dioxide is adsorbed and removed, and product hydrogen is led out from pipe 9.

When one adsorption column 6a breaks through, the raw material gas is introduced into the other adsorption column 6b through the valve 5c, and the adsorption column 6a undergoes a regeneration process. Regeneration of the adsorption cylinder 6a
This is carried out by introducing the low-pressure (approximately 0.5 kg/cm ² G) exhaust gas at room temperature discharged from the PSA device 7 from the pipe 10 through the valve 7a and into the adsorption column 6a. Although the exhaust gas contains carbonyl sulfide, it desorbs impurities from the adsorbent without degrading the adsorbent, and is discharged to the outside from the valve 5b. If necessary, the exhaust gas may be heated before being introduced into the adsorption column 6a, which is preferable because desorption is performed completely.

In a method for purifying such a mixed gas, carbon dioxide is added to the raw material gas, and the hydrogen sulfide contained therein is catalyzed by zeolite to convert it into carbonyl sulfide, which is then sent to the PSA device 8. This eliminates inconveniences such as difficulty in regeneration and accumulation of sulfur when adsorbing and removing hydrogen sulfide, making it possible to efficiently remove hydrogen sulfide. In addition, the equipment is simple and the regeneration of the adsorption cylinders 6a and 6b can be done using the PSA device 8.
This can be easily done using exhaust gas from. moreover,
Even if the hydrogen sulfide concentration in the raw material gas fluctuates, it can be handled without any problems by adding an excess amount of carbon dioxide.

Note that similar effects can be obtained even if the PSA device 8 and the adsorption column are filled with zeolite.

Hereinafter, a specific explanation will be given by showing examples.

〔Example〕

Petroleum refinery offgas having the following composition is used as the raw material gas.

H ₂ 66vol% CH ₄ 16〃 C ₂ H ₆ 14〃 Other hydrocarbons 4〃 H ₂ S 200ppm CO ₂ 50〃 30Nm ³ /hr of this raw material gas is compressed to 9Kg/cm ² G
12N/hr of carbon dioxide was injected into this. The carbon dioxide concentration after injection was 450ppm. This raw material gas was introduced into an adsorption cylinder (two-cylinder type) filled with 20 kg of synthetic zeolite, and then sent to the PSA device. With the PSA device, hydrogen with a purity of 99.999% was obtained with a recovery rate of 72%. When the adsorption column was regenerated with the exhaust gas of the PSA device and operated alternately, 1
Hydrogen sulfide was successfully removed over a long period of over 20 years, and no deterioration in the performance of the PSA device was observed.

It goes without saying that carbon dioxide may be added before pressurizing the raw material gas.

〔Effect of the invention〕

As explained above, in the mixed gas purification method of the present invention, when a mixed gas containing hydrogen sulfide is separated using a PSA device, carbon dioxide is added to this mixed gas, and in the presence of zeolite, hydrogen sulfide and carbon dioxide are separated. This reacts with carbonyl sulfide to form carbonyl sulfide, which is then removed using a PSA device. Therefore, this carbonyl sulfide is stable, easily adsorbed and desorbed, and the adsorbent can be completely regenerated.As a result, hydrogen sulfide contained in the mixed gas can be efficiently removed without deterioration of the adsorbent. Can be removed. It also prevents the deterioration of the adsorbent in the PSA device.
and the equipment and operation for removal are simple;
Fluctuations in the concentration of hydrogen sulfide can be easily coped with, and the removal rate does not decrease. Furthermore, if adsorbents other than zeolite are also filled at the same time, other impurities in the mixed gas can be removed in the same adsorption cylinder.
It protects the PSA device and can flexibly respond to changes in the composition of the mixed gas.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing an example of an apparatus used in the purification method of the present invention. 2... Compressor, 3... Carbon dioxide source, 4...
Valve, 6a, 6b...adsorption cylinder, 8...PSA device,
10...Tube.

Claims (1)

[Claims] 1 When a mixed gas containing hydrogen sulfide is purified and separated using an adsorption device operated by a pressure swing regeneration method, carbon dioxide is added to this mixed gas, and hydrogen sulfide and carbon dioxide are reacted in the presence of zeolite to produce carbonyl sulfide. A method for purifying a mixed gas containing hydrogen sulfide, characterized in that the carbonyl sulfide is removed by the adsorption purification device described above.