JPS61114712A - Purification of gaseous mixture - Google Patents

Abstract

PURPOSE:To raise the removal efficiency of H2S, by adding CO2 to a gaseous mixture containing H2S to react H2S and CO2 in the presence of zeolite to form COS which is, in turn, removed by a pressure swing method. CONSTITUTION:H2S-containing gas is introduced into a compressor 2 from a pipe 1 to be compressed and introduced into an adsorbing tower 6a during an adsorbing process while CO2 is added to said gas from a CO2 source 3 to react H2S and CO2 in the zeolite bed within said adsorbing tower 6a to form COS and the gas containing CO2 and COS receives adsorbing treatment in a PSA apparatus to purify H2-gas which is, in turn, discharged from a pipe 9. When the adsorbing tower 6a is saturated, it enters a regeneration process and the ambient temp. exhaust gas issued from the PSA apparatus is sent to an adsorbing tower 6a. During this time, an adsorbing tower 6b is in an adsorbing process.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses an adsorption device (hereinafter abbreviated as PSA device) operated by a pressure swing regeneration method from a mixed gas containing hydrogen sulfide (LzS). The present invention relates to a method for efficiently removing hydrogen sulfide when recovering a specific gas contained therein, such as hydrogen (H2).

[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 petroleum silk off-gas is H260,O
vot% C) I 4 ko0.0ttCzHs
No jko O〃C3H8'4
0 1 C4H1047 C5Hxz a3 ttH2S
, 2oo lPCO2to , 1 H20 saturated, as an example of liquid phase hydrogenation circulating gas, Hz
7 t 2 mot%N2
yor 〃 CO2 (10s CO yo O〃 Hydrocarbons C-17rtr C2iimoti C-3Qrtt C-4+2ノ〃 C-50,0JI H23aortr NH3a, oノ〃 Therefore, this hydrogen is recovered as fuel, raw material for chemical synthesis, etc. The general KPS is used to recover this hydrogen.
There are many methods that use the A device. 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. Hydrogen sulfide adsorbed by the adsorbent changes to sulfur during desorption, and gradually accumulates in the adsorbent, reducing the hydrogen content of the desorbent. 1. Decreases performance. 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 is complex in terms of equipment and operation. However, 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 a high removal rate is to be achieved. 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, and it is possible to efficiently remove hydrogen sulfide from mixed gas with simple equipment.
The aim is to provide a purification method that can prevent the deterioration of the adsorbent in the equipment. Carbon dioxide is added to the mixed gas and reacts with hydrogen sulfide in the presence of zeolite to form carbonyl sulfide, which facilitates adsorption and desorption. It is characterized by nine things.

[Structure of the invention]

Hereinafter, the present invention will be described 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 off-gas or liquid-phase hydrogenated microvolume gas. First, the raw material gas containing hydrogen sulfide is transferred from the pipe 1 to the compressor 2.
Introduced here! It is pressurized to about 10 kg/crdG. Carbon dioxide from a carbon dioxide source 3 is added to the pressurized raw material gas via a valve 4, and then the gas is passed through a valve 5a to an adsorption column 6a1. -6b is sent to one of the adsorption cylinders 6a which is in the adsorption process. The amount of carbon dioxide is added in excess of 2 to 3 times the reaction equivalent of hydrogen sulfide so that the hydrogen sulfide in the raw material gas is completely converted to carbonyl sulfide. The adsorption cylinders 6g 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. In addition, the adsorption cylinders 6a and 6b are both filled with at least zeolite as an adsorbent, and in addition to this, depending on the impurities in the raw material gas, for example, silica gel or activated carbon is filled. Hydrogen sulfide in the raw material gas introduced into the adsorption column 6& reacts with excess carbon dioxide in the internal zeolite layer due to the catalytic action of the zeolite, and is converted to carbonyl sulfide.

H2S+CO2→CO3+H20 This carbonyl sulfide is more stable than hydrogen sulfide, and when it is desorbed from the adsorbent, it does not precipitate sulfur and is easily desorbed, making it possible to completely regenerate the adsorbent. (9) Impurities other than hydrogen sulfide in the raw material gas, such as airy 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 generated from hydrogen sulfide and containing fc carbonyl sulfide and residual carbon dioxide is sent to the PSA device r8 via the valve 7b. The PSA device 8 is composed of a plurality of adsorption cylinders filled with adsorbents such as activated carbon and Tular sieves, and is used to absorb residual impurities in the raw gas, such as light hydrocarbons, nitrogen, carbon oxides and carbonyl sulfides. Carbon dioxide and carbon dioxide are adsorbed and removed, and product hydrogen is led out from pipe 9.

If one adsorption cylinder 6a breaks through, the raw material gas is removed from the valve 5C.
After that, four people move the other suction tube 6b and perform the regeneration process on the suction tube 6a. The regeneration of the adsorption column 6a is carried out by four people supplying the low pressure (approximately QJkg/crttG) exhaust gas at room temperature discharged from the PSAifNt7 from the pipe 10 to the adsorption column 6& through the valve 7&.

The above exhaust gas contains carbonyl sulfide, which desorbs impurities from the adsorbent without degrading the adsorbent.
It is discharged to the outside from the valve 5b. If necessary, the exhaust gas may be heated before being introduced into the adsorption column 6aK, which is preferable because the adsorption can be completed completely.

In such a mixed gas purification method, carbon dioxide is added to the raw material gas, and the hydrogen sulfide contained therein is converted into carbonyl sulfide by the catalytic action of zeolite, and then the mixture is fed into the PSA device 8. Therefore, problems such as difficulty in regeneration and accumulation of sulfur when removing hydrogen sulfide by adsorption are eliminated, and hydrogen sulfide can be removed efficiently. In addition, the equipment is simple and the regeneration of the adsorption tubes 6&, 6b is possible using the PSA system.
This can be easily done using the exhaust gas from t8. Furthermore, even if there is a fluctuation in the concentration of sulfide water in the raw material gas, if the amount of carbon dioxide is determined to be excessive, it can be dealt with without any problem.

Note that similar effects can be obtained by filling the adsorption cylinder of the PSA device 8 with zeolite.

Examples will be shown below and will be explained in detail. .

〔Example〕

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

) i2 66101. CH4
ノ 6 〃 CzHs 74C
l Other hydrocarbons ≠ 1 (28 QQ l'jfI COZ to #This raw material gas aoNm'/hr is compressed to F kg/dG with a compressor,
Carbon dioxide was injected into this at a rate of N4/hr. The carbon dioxide concentration after injection became HirojQP. This raw material gas was introduced into a nine adsorption column (two-part type) filled with synthetic zeolite co-0-, and then PSA! ! I sent it to e. In the PSA device, 29% of pure hydrogen was obtained with a recovery rate of 7%. When the adsorption column was regenerated with the exhaust gas from the PSA device and the adsorption column was operated in a mutually switching manner, 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.

Incidentally, it goes without saying that carbon dioxide may be added before pressurizing the raw material gas. 4゜[Effects of the Invention] As explained above, in the method for purifying a mixed gas of the present invention, when a mixed gas containing hydrogen sulfide is separated using a PSA device, carbon dioxide is added to the mixed gas to eliminate the presence of zeolite. Below, hydrogen sulfide is reacted with carbon dioxide to form carbonyl sulfide, and this carbonyl sulfide is removed using a PSA device. Therefore, this carbonyl sulfide is stable, easily adsorbed and desorbed, and the adsorbent can be completely regenerated, resulting in the efficient removal of hydrogen sulfide contained in the mixed gas without deterioration of the adsorbent. can. Also, P
Deterioration of the adsorbent in the SA device can be prevented, the removal equipment and operation are simple, and fluctuations in the concentration of hydrogen sulfide can be easily dealt with, without causing a decrease in removal rate. Furthermore, if adsorbents other than 1 zeolite are filled at the same time, other impurities in the mixed gas can be removed in the same adsorption column, making it possible to secure the PSA device and making it more flexible to fluctuations in the composition of the mixed gas. Is it possible to respond to this?

[Brief explanation of drawings]

The drawing is a schematic configuration 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 tube, 8
・River...PSA device, 10...tube.

Claims (1)

[Claims] 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 the mixed gas, and the hydrogen sulfide and carbon dioxide are reacted in the presence of zeolite to form carbonyl sulfide. A method for purifying a mixed gas containing hydrogen sulfide, characterized in that carbonyl sulfide is removed by the adsorption purification device described above.