Removal of hydrogen sulfide waste gas

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Hydrogen Sulfide Removal in Industrial Processes

As humans’ awareness of environmental protection has gradually increased, they have become more concerned about the quality of the surrounding living environment. In recent years, the H2S removal in industrial exhaust gas has attracted the attention of many petrochemical enterprises, and the H2S removal system has gradually been widely used.

Why is H2S Removal Necessary?

Hydrogen sulfide (H2S) is the simplest type of sulfur hydride. At room temperature, hydrogen sulfide is a colorless and highly toxic gas with the smell of rotten eggs. It is volatile and presents a blue flame when it burns.

Hydrogen sulfide is produced in industrial production processes such as natural gas purification, petroleum refining, gas making, leather making, pharmaceuticals, paper making, and synthetic chemical fibers. It is one of the main pollutants in the atmosphere. It can not only cause catalyst poisoning, worsen process conditions and corrosion of equipment, but also cause serious environmental pollution and even endanger the survival of human beings.

H2S harms environment
H2S harms environment
H2S endangers human health
H2S endangers human health

In summary, H2S removal is necessary for chemical waste gas emission enterprises. Because hydrogen sulfide has a wide range of pollution and great influence, once hydrogen sulfide gas is discharged into the atmosphere, it will cause serious environmental pollution. Because sulfur is a valuable raw material in energy, chemical, pharmaceutical, and agricultural fields, rational use of hydrogen sulfide, purification of industrial tail gas, and H2S removal, together with the use of a sulfur recovery system, can effectively realize resource reuse. These have very important practical significance in industrial production.

How to Remove H2S in the Industrial Process?

H2S removal system
H2S removal system

For the H2S-containing waste gas generated in the industrial process, methods such as absorption, adsorption and catalytic oxidation are mainly used for removal, recycling and harmless treatment. Among them, the desulfurization method can be divided into two types: dry method and wet method.

  • For natural gas and refinery gas with a high concentration of H2S and a large total amount discharged from the petroleum, chemical, and other industries, sulfur recovery should be the mainstay. Mainly adopt Claus method and absorption oxidation method.
  • For low-concentration H2S gas, chemical absorption or absorption oxidation can be used to purify.

Dry method H2S removal system

The main methods of H2S removal by the dry method are the ferric hydroxide method, activated carbon method, Claus method, and zinc oxide method.

1. Ferric hydroxide method

The iron scraps and wet sawdust are fully mixed, and 0.5% calcium oxide is added to make desulfurized. The humidity is 30%~40%. The hydrogen sulfide is removed by reaction with the desulfurized and the regenerated ferric hydroxide can be used continuously.

2. Claus method

H2S first reacts with oxygen to form SO2. In the combustion furnace, the generated SO2 continues to react with H2S, and high-quality molten sulfur can be produced directly from the gas phase.

Combustion furnace reaction:

3 H2S  +  1.5 O2 → 2 H2S + SO2 + H2O

       2 H2S  +  SO2 → 1.5 S2 + 2 H2O

Claus reaction:       

2 H2S   + SO2 → 3/n Sn + 2 H2O

Claus method technological process
Claus method technological process

3. Activated carbon method

Activated carbon is used to adsorb hydrogen sulfide, and the hydrogen sulfide is converted into monomer sulfur and water through oxygen. Use amine sulfide to wash away the sulfur, and the activated carbon can be used continuously. This method is not suitable for gas-containing tar.

4. Zinc oxide method

The granular zinc oxide reacts with hydrogen sulfide to produce zinc sulfate and water. This method is mainly used to purify waste gas with low hydrogen sulfide content. This method has high efficiency in the H2S removal system, but the cost is relatively high.

Wet method H2S removal system

Wet method H2S removal mainly adopts solvent method, neutralization method, and oxidation method.

1. Solvent method

This method usually uses 15%-20% diethanolamine aqueous solution to absorb hydrogen sulfide to form a “complex”. When heated to 100~130°C, hydrogen sulfide is precipitated, and high concentration hydrogen sulfide can be obtained by condensation, which is then made into sulfur.

2. Neutralization method

Hydrogen sulfide is an acidic substance and can be removed with an alkaline absorbent. Commonly used absorption liquids include sodium carbonate solution and ammonia water.

3. Oxidation method

After being absorbed by lye, hydrogen sulfide is oxidized to sulfur under the action of a catalyst. The catalyst can be regenerated with air and continue to be used. Commonly used catalysts are nickel salt, ferricyanide, iron oxide, iron hydroxide, alkali metal salts of sulfide arsenic acid, etc.

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