JPH0569566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a method for removing hydrogen sulfide from a mixed gas containing at least hydrogen sulfide and carbon dioxide, such as coke oven gas (COG).

[Prior art and problems to be solved]

Hydrogen is recovered from COG using a main purification unit operated in a pressure swing regeneration mode. Since hydrogen sulfide poses a problem to the main purification equipment, it must be removed in advance until it is reduced to almost zero. Conventionally, in order to remove hydrogen sulfide contained in COG in such a process, there is a method in which an activated carbon adsorption device for preliminary purification is provided upstream of the main purification device, and hydrogen sulfide is adsorbed and removed there. However, with the method of adsorbing hydrogen sulfide onto an activated carbon adsorbent, when hydrogen sulfide is desorbed, hydrogen sulfide precipitates as sulfur S, making it difficult to desorb from the adsorbent, making it necessary to replace the adsorbent. Nakatsuta. There is also a method of regenerating the adsorbent, but it has a limited number of uses and a short lifespan.

Furthermore, in the reaction-adsorption process of hydrogen sulfide onto activated carbon, the reaction mass transfer zone becomes considerably long, and hydrogen sulfide can only be adsorbed in small amounts compared to the capacity of the packed activated carbon, making it necessary to increase the size of the adsorber. I have no choice but to. Although the H ₂ S adsorption rate of activated carbon is usually 10 to 20 wt%, the mass transfer zone is long, so in order to remove hydrogen sulfide to virtually zero, it is necessary to Only an adsorption rate of 1 wt% can be used. For this reason, methods have been adopted, such as installing a preliminary adsorbent with a very large capacity, or allowing a certain amount of hydrogen sulfide to flow into the main purification unit, thereby allowing the adsorbent in the main purification unit to deteriorate prematurely.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of the present invention is to provide a method for removing hydrogen sulfide that can downsize a pre-purification adsorption device, facilitate regeneration of this device, extend the life of the main purification device, and reduce purification costs. That is.

[Structure of the invention]

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

The present invention is characterized by reacting hydrogen sulfide with carbon dioxide in the presence of zeolite in a preliminary purification stage to convert it into carbonyl sulfide, and removing this carbonyl sulfide by adsorption in the main purification device. Taking COG as an example of a gas containing hydrogen sulfide, we will explain the case of removing hydrogen sulfide from COG. The drawings illustrate the method of this invention.
This shows the equipment applied to remove hydrogen sulfide from COG.

After the tar content is removed from the raw material COG in the tar remover 1, it is sent to the compressor 2, where it is
After being pressurized to Kg/cm ² G, it is sent via a valve 3 to one adsorption cylinder 5a of a pre-purification device 5 consisting of two adsorption cylinders 5a and 5b which are operated in a switching manner. These adsorption cylinders 5a and 5b are filled with three types of adsorbents in the order of zeolite, silica gel, and activated carbon from the gas inlet side (upstream side). The hydrogen sulfide in the COG that has flowed into the adsorption column 5a undergoes the reaction _H2S + _CO2 →COS+ _H2O at room temperature in the presence of coexisting carbon dioxide, oxygen, and water using synthetic zeolite molecular sieves as a catalyst. , changes to carbonyl sulfide. The rate of change of hydrogen sulfide into carbonyl sulfide by this reaction depends on the concentration of hydrogen sulfide and carbon dioxide, pressure, etc., but the reaction is fully possible at room temperature. In addition, since hydrogen sulfide in COG is usually in trace amounts,
The heat of reaction is relatively small and does not affect the overall system.

COG in which hydrogen sulfide is converted to carbonyl sulfide
Next, ammonia is adsorbed and removed in the silica gel layer, and then benzene, toluene, xylene, and other hydrocarbons are adsorbed and removed in the activated carbon layer, the preliminary purification is completed, and the product flows out from the adsorption column 5a. The COG flowing out from the adsorption column 5a contains carbonyl sulfide and trace amounts of hydrocarbons as impurities, and is sent to the main purification device 8, which is operated by the next pressure swing regeneration method, through the valve 6. The main purification device 8 is filled with activated carbon and zeolite, and carbonyl sulfide is adsorbed and removed by an adsorbent at the same time as methane, carbon monoxide, etc., and high purity (99.9% or more) hydrogen ( H ₂ ) is derived.

From the adsorption cylinder 5a of the preliminary purification device 5 to the adsorption cylinder 5
Switching to b is due to the outflow COG at the outlet of the adsorption cylinder 5a.
When the benzene concentration in the adsorption cylinder 5a reaches a predetermined concentration, high-pressure steam or heated inert gas for regeneration is passed from the pipe 9 through the three-way valve 10 to the adsorption cylinder 5a.
to desorb benzene, toluene, xylene, water, ammonia, etc., and then the exhaust gas or hydrogen from the main purifier 8 is passed through the three-way valve 11 and pipe 12 for drying and final regeneration, in preparation for the next changeover. . The regenerated exhaust gas is then discharged from the adsorption cylinder 5a to the outside of the system via the three-way valve 13.

In this method of removing hydrogen sulfide from COG, this hydrogen sulfide is converted into carbonyl sulfide using zeolite as a catalyst in the preliminary purification device 5, and this carbonyl sulfide is adsorbed and removed in the main purification device 8. Therefore, the amount of adsorbent in the pre-purification device 5 is mainly for benzene, toluene, and
It is determined by the amount of xylene, etc., and it is sufficient to use about 1/10 of the conventional pre-purification device, which was determined from the limitation of hydrogen sulfide removal performance, and the pre-purification device 5
The regeneration of the adsorbent can also be performed reliably and easily. Also,
Since carbonyl sulfide can be desorbed very easily by the pressure swing regeneration method, the operation of the main purifier 8 does not become particularly complicated or difficult.

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

〔Example〕

30 Nm ³ /hour of raw material COG is passed through the tar remover 1 and compressed to 10 Kg/cm ² G by the compressor 2, and then sent to the preliminary purification device 5. Inside the adsorption cylinders 5a and 5b,
Each container is filled with 2 kg of zeolite, 1 kg of silica gel, and 18 kg of activated carbon, stacked in order from the upstream side. Hydrogen sulfide in COG is here converted to carbonyl sulfide, which is converted into benzene, toluene, xylene,
Ammonia and the like are adsorbed and removed, and then sent to the next main purifier 8. Activated carbon 7 is used in the main purification device 8.
Kg, 8Kg of synthetic zeolite is packed, and carbonyl sulfide etc. are adsorbed and removed, resulting in a purity of 99.99 to 999.9.
% hydrogen was stably obtained over a long period of time from 10 to 13 Nm ³ /hour.

After 25 hours of operation, when approximately 100 to 200 ppm of benzene was detected at the outlet of the pre-purification unit 5, the adsorption cylinder 5
Switch a to the adsorption cylinder 5b, and replace the used adsorption cylinder 5a.
Water vapor at 80 to 150° C. was passed through the reactor for desorption and regeneration, and then regenerated exhaust gas from the main purifier 8 was passed through for final regeneration, drying, and cooling, in preparation for next use.

The pot life until the adsorption cylinders 5a and 5b of the preliminary purification device 5 were switched was gradually shortened until the adsorption cylinders 5a and 5b were switched several times, but after that it became stable and could be used stably for an extremely long period of time.

In conventional pre-purification equipment filled with a large amount of activated carbon, the filler must be replaced in a short period of time, but compared to this, the method of the present invention can be used for a much longer period of time.
A reduction in refining costs was achieved.

In addition, above, we have explained the method for removing hydrogen sulfide when recovering hydrogen from COG, which is an example of a mixed gas containing hydrogen sulfide and carbon dioxide. It can be widely applied to systems in which a minimum amount of mixed gas is pre-purified and then gas separation is performed in the main purification unit operated by the pressure swing regeneration method. In this case, the type of adsorbent filled in the adsorption cylinders 5a, 5b of the preliminary purification device 5 and the stacking order are not limited to the above example, and may be changed depending on the composition of the mixed gas, for example, on the inlet side (upstream side). Activated carbon, zeolite, and silica gel may be used in that order from side) to the adsorption cylinders 5a and 5b, as long as at least zeolite is present in the adsorption cylinders 5a and 5b, whereby hydrogen sulfide in the mixed gas is sufficiently converted to carbonyl sulfide,
The same effects as in the above example can be obtained.

〔Effect of the invention〕

As explained above, in the method of removing hydrogen sulfide from a mixed gas according to the present invention, a mixed gas containing at least hydrogen sulfide and carbon dioxide is pre-purified, and then the gas is purified in a main purification device operated by a pressure swing regeneration method. When performing separation, hydrogen sulfide is reacted with carbon dioxide in the presence of zeolite in the preliminary purification stage to convert it into carbonyl sulfide, and then this carbonyl sulfide is removed by adsorption in the main purification device. Therefore, the adsorption efficiency is poor,
Furthermore, hydrogen sulfide, which generates sulfur during desorption and regeneration, which causes problems, is first converted into carbonyl sulfide, which has good adsorption efficiency and does not cause problems in desorption and regeneration, and this carbonyl sulfide is removed by adsorption in the main purification equipment. The amount of adsorbent in the preliminary purification stage can be significantly reduced, and its desorption and regeneration can be easily performed. In addition, carbonyl sulfide can be efficiently adsorbed and removed in the main purification device, and desorption and regeneration of the main purification device can be carried out easily as usual. Therefore, according to the method of the present invention, various problems associated with the adsorption and removal of hydrogen sulfide can be solved at once, and the cost associated with the removal can be significantly reduced.

[Brief explanation of the drawing]

The drawing is a flowchart of an apparatus used for removing hydrogen sulfide when recovering hydrogen from COG, as an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. When a mixed gas containing at least hydrogen sulfide and carbon dioxide is pre-purified and then gas separated in a main purification unit operated by a pressure swing regeneration method, in the presence of zeolite in the pre-purification stage. ,
A method for removing hydrogen sulfide from a mixed gas, characterized in that hydrogen sulfide is reacted with carbon dioxide to convert it into carbonyl sulfide, and then this carbonyl sulfide is adsorbed and removed in the main purification device.