JPS6146169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for desulfurizing hydrogen sulfide-containing gas. Specifically, the present invention relates to a method for removing hydrogen sulfide from a hydrogen sulfide-containing gas using a redox catalyst. Conventionally, so-called "redox catalysts" are used to wet-process hydrogen sulfide-containing gases such as coke oven gas, petroleum cracking gas, natural gas, and factory waste gas to remove hydrogen sulfide and recover sulfur. Methods are known, and representative ones include the fumux method using picric acid, the strep hood method using anthraquinone sulfonate,
There is the Takahatsu method using naphthoquinone sulfonate. In both of these methods, hydrogen sulfide is absorbed and removed by bringing the redox catalyst solution into contact with a hydrogen sulfide-containing gas, and the catalyst solution that has absorbed hydrogen sulfide is regenerated with a molecular oxygen-containing gas such as air. The regenerated liquid is recycled and used again as a catalyst liquid. The reaction mechanism, for example when coke oven gas is treated by the Fumax method, is as follows. First, in the absorption tower, coke oven gas is
NH ₃ , H ₂ S and HCN are reacted and absorbed as NH ₄ HS and NH ₄ CN, and S is separated from NH ₄ HS by the catalytic action of picric acid added to the system. This S is consumed as separated S from (NH ₄ ) ₂ Sx ₊₁ produced in the absorption tower, and reacts with NH ₄ CN to produce NH ₄ SCN. NH ₃ +H ₂ SNH ₄ HS NH ₃ +HCN→NH ₄ CN NH ₄ HS+R・NO+H ₂ O→ NH ₄ OH+S+R・NHOH NH ₄ HS+NH ₃ +Sx→(NH ₄ ) ₂ Sx ₊₁ NH ₄ CN+(NH ₄ ) ₂ Sx ₊₁ → NH ₄ SCN + (NH ₄ ) ₂ Sx Picric acid, which released oxygen through catalytic action,
It is regenerated by being supplied with oxygen from the air in a regeneration tower. 2NH ₄ HS+20 ₂ →(NH ₄ ) ₂ S ₂ O ₃ R・NHOH+1/20 ₂ →R・NO+H ₂ O (NH ₄ ) ₂ Sx+S→(NH ₄ ) ₂ Sx ₊ 1However, the coke oven is As the size increases, the scale becomes larger, and as a result, the desulfurization equipment for coke oven gas also becomes larger. Such a large-scale coke oven is operated according to the operating rate of the blast furnace that uses the coke produced in the coke oven, so the load on the desulfurization equipment is as follows:
It varies depending on the operating rate of the blast furnace or coke oven. In this case, if the scale of the desulfurization equipment is constructed according to the maximum operation rate of the coke oven, a sufficient desulfurization effect can be obtained, but since it is usually operated at a smaller scale, the desulfurization equipment should be constructed according to the maximum operation rate. Not only does construction cost increase, but power costs also increase, which has the disadvantage of increasing costs. On the other hand, if the desulfurization equipment is constructed in accordance with the normal operation rate, if the coke oven operation rate increases and the load on the desulfurization equipment increases,
The drawback was that the desired desulfurization effect could not be obtained. The present invention was made in order to eliminate the various drawbacks of the conventional method, and involves bringing hydrogen sulfide-containing gas into contact with an alkaline absorption liquid containing a redox catalyst in an absorption tower, thereby transferring hydrogen sulfide to the absorption liquid. The absorbent liquid that has absorbed hydrogen sulfide is catalytically oxidized with a molecular oxygen-containing gas in a regeneration tower to liberate sulfur, and the regenerated absorbent thus obtained is then recycled to the absorption tower. A method for desulfurizing a gas containing hydrogen sulfide, characterized in that a part of the regenerated absorption liquid obtained in the regeneration tower is circulated to the regeneration tower. Examples of the redox catalyst used in the present invention include picric acid, anthraquinone sulfonate, naphthoquinone sulfonate, and naphthohydroquinone sulfonate, with picric acid being preferred. Next, the present invention will be described with reference to the drawings, taking as an example a case where coke oven gas is desulfurized using picric acid as a redox catalyst. That is, as shown in the drawing, the coke oven gas introduced into the lower part of the absorption tower 2 through the conduit 1 is brought into countercurrent contact with an absorption liquid consisting of an ammonia aqueous solution of picric acid, which is supplied to the top of the tower through the conduit 3. After hydrogen sulfide, ammonia, hydrocyanic acid, etc. are absorbed and removed, they are discharged from the system through a conduit 4 at the top of the absorption tower 2. The absorption liquid that has absorbed hydrogen sulfide, ammonia, hydrocyanic acid, etc. is discharged from the bottom of the tower through a conduit 5, and the consumed amount of picric acid is transferred to the conduit along with water corresponding to the amount of regenerated absorption liquid to be extracted as described later. After being replenished from 6, it is supplied to the upper part of the regeneration tower 9 via a pump 7 and a conduit 8. In the regeneration tower 9, the absorption liquid is regenerated by bringing it into countercurrent contact with a molecular oxygen-containing gas, such as air, supplied through a conduit 10 to liberate sulfur.
The remaining molecular oxygen-containing gas is transferred from the top of the column to conduit 11.
After that, it is discharged from the system. The regenerated absorption liquid is discharged from the bottom of the tower through a conduit 12, and is supplied to the top of the absorption tower 2 through a pump 13 and conduits 14 and 3.
However, the entire amount of the absorption liquid was not circulated to the absorption tower 2, and a part of it was taken out from the conduit 15 and absorbed hydrogen sulfide, etc. in the conduit 8, which was sent from the absorption tower 2 to the regeneration tower 9. It is mixed with the absorption liquid and circulated to the regeneration tower 9. However, by repeating such circulation, free sulfur accumulates in the regenerated absorption liquid, and a part of it is discharged from the conduit 16 and sent to the secondary desulfurization treatment process. In the above method, the alkali supplied to the absorption tower 2 includes ammonia, sodium hydroxide, etc., but preferably ammonia. Especially when desulfurizing coke oven gas, because of the ammonia derived from the gas, There is no particular need to add it. The amount of oxygen required in the regeneration tower 9 is 2 Nm ³ or more of air per 1 kg of hydrogen sulfide in the absorption tower, preferably 10 to 30 Nm ³ . The regenerated absorption liquid containing free sulfur discharged from the conduit 16 is 0.05 to 0.5% by volume of the amount circulated in the system, and is used to recover elemental sulfur or to treat the desulfurization liquid, such as combustion or production of sulfuric acid. be done. 10 to 50% by volume, preferably 20
~40% by volume is separated via conduit 15 and recycled to the regeneration tower. In this way, part of the regenerated absorption liquid is circulated to the regeneration tower because it has been experimentally confirmed that even if the circulation amount of the absorption tower is reduced, there is no problem with the desulfurization rate as long as the regeneration efficiency is good. When the circulation rate to the absorption tower was reduced and a part of it was circulated to the regeneration tower, the contact time with air in the regeneration tower became longer compared to the normal circulation rate, and the height of the tower was increased by that amount. This is because it was discovered that the same effect can be obtained, and in addition, once the regenerated liquid is circulated again, it helps regenerate the unregenerated portion, and together with the dilution effect, the regeneration speed is increased. Furthermore, regarding the regeneration atmosphere, the amount of ammonia circulated to the absorption tower is reduced by the amount that is circulated to the absorption tower, and the ammonia concentration in the regeneration tower is reduced due to the dilution effect, so interference with regeneration can be prevented. I can do it. Therefore, it can be said that the above-mentioned improvement in regeneration efficiency by circulating a portion of the regenerated absorption liquid to the regeneration tower, and in turn, the improvement in desulfurization efficiency, is due to these synergistic effects. Next, the method of the present invention will be explained in more detail with reference to Examples. Example In the apparatus shown in the drawing, coke oven gas (COG; hydrogen sulfide 4g/Nm ³ , ammonia
10g/Nm ³ containing) is supplied to the absorption tower 2, and the regenerated absorption liquid (containing ammonia 7g/) is supplied from the conduit 3.
It was brought into countercurrent contact with 1.5×10 ⁻² m ³ /Nm ³ -COG to absorb and remove hydrogen sulfide, and deflow coke oven gas was discharged from conduit 4. The absorption liquid (containing 12.0 g/ammonia) discharged from the conduit 5 was supplied to the upper part of the regeneration tower 9. 0.1 Nm ³ /Nm ³ -COG of air was supplied to the regeneration tower 9 to regenerate the absorption liquid, and the air was discharged from the top of the tower through the conduit 11. Conduit 1 from the bottom of regeneration tower 9
2, 14, regenerated absorption liquid (ammonia 7g/
Containing) 2.2×10 ^-2 m ³ /Nm ³ -COG is discharged and 2/3
is supplied to the absorption tower 2 through conduit 3, and the remaining 1/3 is mixed with the absorption liquid in conduit 8 through conduit 15, resulting in a mixed absorption liquid (containing 7.0 g of ammonia) 2.2×10 ^-2 m ³ /Nm ³ -COG was circulated to regeneration tower 9. Incidentally, the regenerated absorption liquid was discharged little by little from the conduit 16 to attack the desulfurization liquid treatment process. The hydrogen sulfide removal rate in this case was 95%. Note that when a part of the regenerated absorption liquid was not circulated to the regeneration tower 9 and the entire amount was supplied to the absorption tower 2 through the conduit 3, the hydrogen sulfide removal rate was 92%. Furthermore, the ammonia concentration and oxidation-reduction potential (O, R, P,) of the regenerated absorbent were measured by changing the rate at which the regenerated absorbent was circulated to the regeneration tower, and the following results were obtained. 【table】

[Brief explanation of the drawing]

The drawing is a flow sheet showing one embodiment of the method of the present invention. 2...Absorption tower, 9...Regeneration tower, 12...Regenerated absorption liquid discharge conduit, 15...Regenerated absorption liquid circulation conduit.

Claims (1)

[Claims] 1. Hydrogen sulfide-containing gas is brought into contact with an alkaline absorption liquid containing a redox catalyst in an absorption tower to absorb hydrogen sulfide into the absorption liquid, and the absorption liquid that has absorbed hydrogen sulfide is brought into contact with an alkaline absorption liquid containing a redox catalyst in an absorption tower. In a method for desulfurizing a hydrogen sulfide-containing gas, the hydrogen sulfide-containing gas is catalytically oxidized with a molecular oxygen-containing gas to liberate sulfur, and then the regenerated absorption liquid thus obtained is recycled to the absorption tower. A method for desulfurizing a hydrogen sulfide-containing gas, comprising circulating a portion of the regenerated absorption liquid to the regeneration tower. 2. The method according to claim 1, wherein the regenerated absorption liquid recycled to the regeneration tower is 10 to 50% by volume of the amount to be supplied to the absorption tower. 3. The method according to claim 1 or 2, wherein the redox catalyst is picric acid. 4. The method according to any one of claims 1 to 3, wherein the alkali is ammonia. 5. The method according to any one of claims 1 to 4, wherein the hydrogen sulfide-containing gas is coke oven gas.