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During the coal chemical production process, materials such as gas, liquefied petroleum gas, and chemical exhaust gases contain hydrogen sulfide (H₂S), which must be removed. The mainstream methods for hydrogen sulfide removal in the coal chemical industry can be divided into two categories: dry desulfurization and wet desulfurization. The details are as follows: 01///Wet Desulfurization/// Wet desulfurization involves using a solution (water-based or organic solvent) to undergo a chemical reaction or physical dissolution with hydrogen sulfide, thereby achieving gas-liquid separation. It offers advantages such as high treatment capacity, high desulfurization efficiency, and the possibility of recovering sulfur. It is suitable for coal chemical process exhaust gases with high hydrogen sulfide concentrations, such as coke oven gas and raw gas for ammonia synthesis. A. Chemical absorption method – Alkylamine method. Principle: The alkylamine solution is alkaline and undergoes a reversible reaction with the acidic H₂S to form hydrosulfides or sulfides ； The rich liquid is regenerated by heating, releasing high-concentration H₂S, while the lean liquid is recycled. Features: It can reduce H₂S to below 10 mg/m³, making it suitable for gas desulfurization in environments with high CO₂ and high H₂S levels. Ammonia method: Principle: Ammonia is used as an absorbent that reacts with H₂S to form ammonium hydrosulfide and ammonium sulfide. The absorbent solution can be oxidized to regenerate sulfur, or it can be used directly as a raw material for nitrogen fertilizers. Features: Suitable for desulfurizing coke oven gas in coking plants, enabling the recovery of sulfur resources; however, ammonia escape must be controlled. B. Physical absorption method: Low-temperature methanol washing (Rectisol). Principle: Under low temperature and high pressure (–20 to –40°C), methanol has a strong physical capacity to dissolve acidic gases such as H₂S and CO₂; the methanol that has absorbed these acidic gases is regenerated through depressurization and heating. Features: Integrated desulfurization and decarbonization, with extremely high desulfurization accuracy (H₂S＜0.1mg/m³). Suitable for the purification of feed gas in large-scale coal chemical projects, but it requires substantial capital investment and a low-temperature refrigeration system. Principle of the polyethylene glycol dimethyl ether method (NHD method): The NHD solvent exhibits good selective solvation capacity for H₂S and CO₂, allowing for absorption and desorption at normal temperature and pressure. Features: Lower energy consumption compared to low-temperature methanol washing, good chemical stability of the solvent, and low corrosivity. Suitable for desulfurization in small-scale coal chemical plants used in gasification of syngas and desulfurization of refinery gas. C. Wet oxidation-reduction method, tannin method: Principle: Using tannin as a catalyst, an alkaline solution absorbs H₂S to form sodium hydrosulfide, which is then oxidized by air to produce elemental sulfur. Features: Non-directional oxidation process, high rate of by-product salt formation, the solution tends to foam, and defoamers need to be added regularly. Suitable for operating conditions with relaxed environmental requirements. PDS method (dinicobalt phthalocyanine sulfonate method) Principle: PDS acts as a catalyst; under alkaline conditions, H₂S is oxidized to elemental sulfur, and the catalyst regains its activity through oxidation by air. Features: Fast reaction speed, capable of handling gases with high sulfur content; however, the sulfur recovery rate is 50%~60%, there is a high amount of by-products, and a waste liquid treatment system is required. GLT “Zero Waste Liquid” technology set: Principle – Based on the GLT high-performance catalyst, an alkaline solution is used to absorb H₂S, thereby producing elemental sulfur directly; the catalyst is then regenerated through an oxidation cycle using air. Features: 99% sulfur recovery rate, zero waste liquid; eliminates desulfurization waste at the source, enables targeted recovery of sulfur products, and has low energy consumption. Suitable for desulfurization of coke oven gas/syngas/acidic off-gases with a sulfur content of 100 kg to 30 t/d. The investment is low, operating costs are minimal, and the utilization of sulfur resources can generate economic benefits. 02 ///Dry Desulfurization/// Dry desulfurization makes use of solid adsorbents or catalysts to undergo a chemical reaction with hydrogen sulfide, converting it into solid sulfides or elemental sulfur. It offers advantages such as high desulfurization accuracy, simple equipment, and no need for solvent regeneration; it is suitable for the precise desulfurization of gases with low hydrogen sulfide concentrations (such as the advanced treatment of purified gases). Activated carbon adsorption method: Principle – Activated carbon physically adsorbs H₂S; in the presence of oxygen, it can act as a catalyst to oxidize H₂S into elemental sulfur, which is then adsorbed on its surface ； Saturated activated carbon can be regenerated by heating or replaced directly. Features: High desulfurization accuracy (H₂S＜0.5mg/m³), simple operation; suitable for the precise desulfurization of low-sulfur gases. However, its processing capacity is limited, and the adsorbent needs to be replaced or regenerated regularly. Principle of the iron oxide desulfurization method: Using iron oxide (Fe₂O₃) as the main active component, it reacts with H₂S to produce ferrous sulfide (FeS) ； When the desulfurization agent becomes ineffective, air can be introduced to oxidize FeS to Fe₂O₃, enabling regeneration while elemental sulfur is precipitated. Features: It can react at room temperature, making it suitable for the precise desulfurization of coal gas and natural gas; however, its desulfurization capacity is low, so it is appropriate for small-scale coal gasification units. Zinc oxide desulfurization method: Principle: Zinc oxide (ZnO) undergoes an irreversible reaction with H₂S to form stable zinc sulfide (ZnS), achieving extremely high desulfurization accuracy (H₂S＜0.01mg/m³). Features: Suitable for the deep desulfurization of raw gas used in coal chemical and fine chemical industries, and can effectively protect downstream catalysts ； However, desulfurizers are non-renewable and need to be replaced once they become ineffective, resulting in high operating costs. Principle of molecular sieve desulfurization: selective adsorption in pores, and regeneration through high-temperature desorption. Features: Fine chemical raw material gases, low-temperature gas desulfurization. Principles for selecting desulfurization technologies in coal chemical industry NO.1: For feed gases with high sulfur content and large processing volumes (such as coke oven gas and coal-derived gas), wet desulfurization methods (such as the MDEA method and low-temperature methanol washing) should be preferred, as they facilitate the recovery of sulfur resources. NO.2 For high sulfur content applications ranging from 100 kg to 30 t/day, it is recommended to use the GLT “zero wastewater” integrated technology. This technology features a catalyst with a selectivity of over 99%, effectively suppressing the formation of by-product salts. There are no emissions of any kind of waste; the sulfur paste can be recycled into high-value sulfur products. Additionally, this technology requires low investment and incurs minimal operating costs. NO.3 For the deep purification of gases with low sulfur content (such as precise desulfurization), dry desulfurization methods (such as the zinc oxide method and activated carbon method) are preferred to ensure compliance with the requirements of downstream processes.