Under what circumstances must gas desulfurization be changed?

Wet desulfurization is used for primary desulfurization. If the organic sulfur in the system is relatively high, shift gas desulfurization must be used. After organic sulfur is catalyzed by a low-change cobalt-molybdenum catalyst, the following reaction occurs to generate hydrogen sulfide: (thiol) RSH + H2 = RH + H2S + Q (thiophene) C4H4 S + 4H2 = C4H10 + H2S + Q (carbon disulfide) CS2 + 2H2 = C + 2H2S + Q (carbon sulfide) COS + H2 = CO + 2H2S + Q (ethylene) C2H4 + H2 = C2H6 After organic sulfur is converted into hydrogen sulfide, wet desulfurization can be used for shift gas desulfurization.

Generally speaking, except for those manufacturers whose natural gas conversion process has completed fine desulfurization in advance, all manufacturers must convert gas desulfurization. Some small plants do not have a shift gas desulfurization process, which is at the expense of the environment and is not allowed. Shift gas desulfurization includes wet oxidation method (such as tannin method, 888 method, etc.), physical absorption regeneration (low-temperature methanol washing, NHD, etc.) and dry method (activated carbon absorption, pressure swing adsorption method, etc.). Small and medium-sized plants mainly use wet oxidation method, and large plants mainly use low-temperature methanol washing with Claus method. Pressure swing adsorption desulfurization in small plants cannot be recycled and is not worth discussing. Large-scale pressure swing adsorption desulfurization is also equipped with Claus recovery process, which is still in the experimental stage.

Shift gas desulfurization must be carried out under the following circumstances: ① Plants that adopt a full low-shift production process: The full low-variation process has relatively high requirements for the H2S concentration in the semi-water gas, which is generally required to be controlled above 150㎎/m³ (standard). Under this situation, if shift gas desulfurization is not carried out, it will be difficult to maintain normal production in the back section. ②Plants using high-sulfur coal as raw material: Although production plants using high-sulfur coal as raw materials can reduce the H2S concentration in semi-water gas to below 70㎎/m³ (standard), part of the organic sulfur is converted into H2S after conversion, which may still cause excessive H2S in the converted gas. ③Plants equipped with decarbonization equipment: Urea production plants and plants that have decarbonization devices set up to increase ammonia surplus, especially plants that use propylene carbonate decarburization process. The shift gas has been desulfurized, which can reduce the consumption of decarburization liquid, alleviate the clogging of the decarburization system, and stabilize the normal production of the decarburization post and the subsequent section. Desulfurization method to be used: Shift gas desulfurization can be achieved by wet oxidation desulfurization or dry desulfurization.