JPS5849591B2 - Wet desulfurization method for coke oven gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing hydrogen sulfide from coke oven gas by bringing coke oven gas into contact with an alkali-containing absorption liquid.

Coke oven gas usually contains 2 to 6 g/Nm” of hydrogen sulfide.
．． Contains 5-3 g/Nm" of hydrogen cyanide.

Hydrogen sulfide burns and becomes sulfur dioxide gas, which pollutes the atmosphere, so it must be removed during the purification process.

Methods for removing hydrogen sulfide from coke oven gas include a method of absorbing ammonia in the gas as an alkali source, and a method of absorbing the gas from which ammonia has been removed using caustic soda as an alkali source, but both methods absorb hydrogen sulfide. When the oxidized liquid is oxidized with a gas containing oxygen, a redox catalyst such as a quinoline derivative, a naphthoquinone derivative, an anthraquinone derivative, or picric acid is used to produce mainly elemental sulfur and thiocyanide, and as a side reaction, thiosulfate and sulfate are produced. elemental sulfur is separated, the absorption liquid is recirculated, and make-up water, catalyst, and
Adds alkali.

This method is a so-called redox reaction type coke oven gas wet desulfurization method, which uses a catalyst to efficiently oxidize H2S or HS- ions absorbed in the absorption liquid to elemental sulfur. The elemental sulfur suspended in water was mainly removed by physical means such as centrifugation.

However, a new method for absorbing liquid treatment was developed in which wet oxidation is carried out at high temperature and pressure to convert all elemental sulfur and sulfur compounds into sulfates at once, and the method of generating elemental sulfur is meaningless, and rather the absorption liquid circulation system. This caused the desulfurization tower to become clogged.

In particular, in the desulfurization method in which the coke gas desulfurization process is installed before the removal of light oil and naphthalene, heavy unsaturated hydrocarbons contained in coke oven gas combine with the generated elemental sulfur to form a highly viscous oily sulfur compound. This was a major cause of clogging, such as adhesion to the packed bed of the desulfurization tower.

In addition, the generated elemental sulfur is not preferable because it causes clogging of the heat exchanger and local abnormal oxidation reactions even in the wet oxidation process which is the treatment equipment for the absorption liquid.

Furthermore, in the absorption liquid treatment process and wet oxidation, all of this elemental sulfur becomes sulfuric acid, which has the effect of making the reaction product strongly acidic, so it is necessary to add an alkali such as ammonia necessary for neutralization. Furthermore, since this elemental sulfur starts to oxidize at low temperatures and has a high calorific value, there are strong restrictions on the concentration that can be charged to wet oxidation equipment.

On the other hand, one method of desulfurization operation that does not generate elemental sulfur is to limit the amount of oxygen supplied in the catalyst oxidation regeneration process or to lower the concentration of the added catalyst to replace HS- ions with H or S2.
There is also an operating method in which oxidation is limited to 0.0 and 0.1 to 0.1, and elemental sulfur is not generated as much as possible.

However, even with this method, it is impossible to operate without generating elemental sulfur at all due to fluctuations in the hydrogen sulfide concentration of coke oven gas and gas flow rate, and furthermore, the oxidation regeneration of the catalyst in the oxidation process becomes poor, which has the effect of lowering the desulfurization rate. However, there were drawbacks that prevented it from being an efficient desulfurization method.

The present invention solves all of the above problems by adding ammonium water, which has been removed and condensed from coke oven gas, and phenol or tar acid to this absorption liquid.

In other words, it was discovered that there is a catalytic substance for redox reaction, albeit in a small amount, in the ammonium solution cooled and condensed from coke oven gas, and when redox reaction-type wet desulfurization is performed using this substance, a specific substance is produced in the absorption liquid. It has been confirmed that desulfurization is possible by simply adding ammonium water without adding a catalyst, but in addition, the catalytic substances contained in this ammonium water contain elemental sulfur, which causes blockage when oxidizing HS. SCN-, S20. Il! -, soX-
The organic water-soluble substances such as phenol and pyridine that are contained in small amounts in ammonium water have the ability to dissolve blockages, so adding ammonium water to the absorption liquid has double and triple effects on preventing blockages. It is effective.

In addition, by adding ammonium water to the absorption liquid in the packed bed of a desulfurization tower that has already become clogged, it is possible to continue the desulfurization operation and clean out the blockage, thereby increasing the cleaning capacity. If this is insufficient, the objective can be achieved by adding 0.3 to 2% of phenol or cool acid to the absorption liquid.

The drawing is a process diagram of a redox reaction type coke oven gas wet desulfurization equipment.

In the figure, 1 is undesulfurized coke oven gas, and this gas 1 is the desulfurization tower 2.
The hydrogen sulfide in the gas 1 is absorbed by contact with the absorption liquid 3 and becomes desulfurized coke oven gas 4.

The absorption liquid 3 contains hydrogen sulfide which is oxidized by an oxygen-containing gas 6 and a catalyst in the oxidation tower 5, and which reacts with the hydrogen cyanide absorbed simultaneously in the absorption tower 2, thiocyanide, elemental sulfur which is an oxide of hydrogen sulfide, thiosulfide, Forms water-soluble salts of sulfates.

In order to maintain the desulfurization rate of the absorption liquid 3, a part of the absorption liquid 3 is extracted as a blow 10 to prevent the salt concentration from increasing, and a catalyst 7,
Add makeup water 8 and alkaline source 9.

Since the blow 10 has a high COD, it is treated by wet oxidation-reduction combustion or the like.

13 is a tower bottom blow line, and 14 is an electrostatic precipitator.

Example In the equipment shown in the drawings, ammonium water and phenol were added to the absorption liquid 3 instead of the catalyst 7 to prevent blockage, and ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate were added at 60 g/l and 5 g, respectively. /l,409/
Furthermore, using an absorption liquid containing 8 g/l of ammonia, the desulfurization rate, the cyanogen removal rate, and the progress of clogging of the column were investigated.

Air is used as the gas supplied to the oxidation tower, and the air ratio is 0.05 (
The temperature of the absorption liquid (air/COG) and gas was 35° C., and ammonia in coke oven gas was used as the alkali source.

Ammonia in undesulfurized coke oven gas is 8 to 10 g/
Hydrogen sulfide with Nm is 2 to 3 g/Nm3, hydrogen cyanide is 0
．． It was 6-1.197Nm3.

The investigation results are summarized in Table 1 along with the operating conditions of the equipment.

As shown in Table 1, when the method of the present invention is carried out in a state where the desulfurization tower is blocked by the conventional method, the blockage is eliminated in a short period of time and operation can be continued.

In the present invention, it has been found that the same effect can be obtained by using tar acid (mixture of phenol, cresol, xylenolic acid, etc.) recovered by tar distillation instead of phenol.

In the present invention, the amount of ammonium water added is 10% of the absorption liquid.
The effect of preventing clogging is obtained with the above, and the effect of dissolving clogging deposits is recognized when phenol or tar acid is 0.1% or more in the absorption liquid, and it becomes noticeable when it is 0.3% or more, but when it exceeds 2%, the effect of clogging prevention is observed. Since the effect slows down and reaches a ceiling at 5%, it is economically unsuitable to add more than 5% and cannot be adopted.

As described above, according to the present invention, in the conventional redox reaction type coke oven gas wet desulfurization method, it becomes unnecessary to add a specific catalyst and at the same time eliminates the generation of elemental sulfur. Blockages in other equipment can be cleaned while operation continues, and this has extremely large economic effects, such as improving the processing efficiency of the wet oxidation method in the absorption liquid treatment process and ensuring stable operation. be.

[Brief explanation of drawings]

The drawing is a process diagram of a redox reaction type coke oven gas wet desulfurization equipment. 1: undesulfurized coke oven gas, 2: desulfurization tower, 3: absorption liquid,
4: Desulfurization coke oven gas, 5: Oxidation tower, 6: Oxygen-containing gas, 7: Catalyst, 8: Make-up water, 9: Alkali source, 10:
Blow, 11: Exhaust, 13: Bottom blow line, 14:
Electric dust collector.

Claims (1)

[Claims] 1 Coke oven gas is brought into contact with an absorption liquid containing an alkali to absorb and remove hydrogen sulfide from the coke oven gas, and the hydrogen sulfide contained in the absorption liquid is further oxidized using a redox catalyst, and the alkali is regenerated and circulated. A wet desulfurization method for coke oven gas, characterized in that ammonium water cooled and condensed from coke oven gas and phenol or tar acid are added to the absorption liquid.