What is dry gas desulfurization

The dry gas mainly contains C1 and C2 alkane hydrocarbons and a small amount of hydrogen. Non-hydrocarbon gases, such as hydrogen sulfide and mercaptans, are present in dry gas to varying degrees. The presence of harmful gases such as hydrogen sulfide limits the use and further processing of dry gas. For example, when dry gas is used as a raw material or fuel for the conversion of light hydrocarbon vapor to hydrogen, it can cause equipment corrosion, catalyst poisoning and environmental pollution. In addition, the hydrogen sulfide separated from the dry gas is a raw material for the manufacture of sulfur yellow and sulfuric acid, so desulfurization of the dry gas is required.

Dry gas desulfurization methods

Dry gas desulfurization methods are basically divided into two main categories. One type is dry desulfurization, which is to remove hydrogen sulfide by passing the dry gas through a bed of solid adsorbents, and the main solid adsorbents often used are iron oxide, zinc oxide, activated carbon, zeolite and molecular sieve, etc. The content of hydrogen sulfide after desulfurization can be reduced to less than 1ug/g. This type of method is suitable for the treatment of gases containing trace amounts of hydrogen sulfide, as well as the need for high desulfurization rate. Another type is wet desulfurization, which uses a liquid adsorbent to wash the dry gas to remove the hydrogen sulfide in the dry gas. Then the adsorbent that absorbs hydrogen sulfide is heated so that hydrogen sulfide is desorbed from it and further processed into sulfur yellow, while the recovered adsorbent is returned to the system for recycling. The refining effect of wet desulfurization is not as good as that of dry desulfurization, but it has the characteristics of continuous operation, compact equipment, large processing capacity, low investment and operating costs, and thus has been widely used.

Wet desulfurization is further divided into chemical absorption, physical absorption, direct conversion and other methods according to the characteristics of absorbent absorption of hydrogen sulfide, while the chemical absorption method is currently more widely used.

Chemical absorption method is characterized by the use of alkaline solutions that can react with hydrogen sulfide for chemical absorption, the solution of alkaline compounds and hydrogen sulfide at room temperature combined into complex salts, and then decomposition of the complex salts by heating or pressure reduction to release hydrogen sulfide gas. One of the common features of the chemical absorption method is that most of the absorption solution is alkaline, and absorption is carried out in the form of absorption solution reaction with dissociation of hydrogen sulfide.