Application and Advantages Analysis of Dongshi Pressurized Wet Flue Gas Desulfurization Technology

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1. Technical introduction: Using low-quality coal for gasification to produce hydrogen is a technical approach that will remain unchanged in China in the long term. During the transformation of gas generation technology, as the gasification pressure and the CO2 content in the gas increase, it has a significant impact on the removal of H2S. Both CO2 and H2S are acidic substances; the conventional wet oxidation desulfurization process removes H2S while also eliminating some of the CO2. This not only results in a loss of CO2 but can sometimes also affect the proper operation of the desulfurization process. The main effect of CO2 in the gas source on the desulfurization process using conventional wet oxidation is to increase the equivalent ratio of NaHCO3 to Na2CO3 in the absorption solution, to lower the pH value of the solution, to reduce the mass transfer coefficient for absorbing H2S, and to decrease the degree of purification ； An increase in the equivalent ratio of the absorbent solutions NaHCO3 to Na2CO3 enhances the foaming tendency of the desulfurization solution, affecting the absorption and regeneration processes. 2. Technical characteristics: From the perspective of reaction mechanism analysis, the reaction between H2S and an alkaline solution is an instantaneous ionic reaction, controlled by gas-phase mass transfer ； The reaction between CO2 and an alkaline solution is not an ionic reaction; it is controlled by mass transfer in the liquid phase. In feed gas with a high CO2 content, the selectivity of the desulfurization liquid for H2S absorption is achieved through the difference in absorption rates of the two components; therefore, the selectivity of the absorption process depends not only on the properties of the absorbent but also on the gas-liquid contact conditions as well as the contact time between the gas and the liquid. The pressurized desulfurization technology developed by Changchun Dongshi Company is a complete wet desulfurization process that has been subject to long-term industrial application. It relies on patented or proprietary technologies such as filler-free mass transfer absorption, CO2 atomization flashing, and DSH desulfurization catalysts, and effectively addresses the adverse effects of high CO2 levels on the desulfurization process using the wet oxidation method. The pressurized desulfurization technology developed by Changchun Dongshi Company exhibits excellent adaptability to process conditions with high H2S levels and high CO2 partial pressures. It has been applied in multiple units for the desulfurization of pressurized gasified coal gas or similar gases, achieving very good results. The process conditions suitable for this technology are: (1) operating pressure of 0.1–6.0 MPa; (2) operating temperature of 25–45°C; (3) H2S content in the gas supply of 0.05–60 g/Nm3; (4) CO2 content in the gas supply ≤95%; (5) H2S content in the purified gas ≤5 mg/Nm3. The application scenarios for this technology include: 1) pressurized desulfurization processes for new plants involved in the gasification of water-coal slurry or pulverized coal on a medium to small scale ； 2: Fixed-bed gas production modified to a pressurized desulfurization mode suitable for clean coal gasification ； 3: Cancel normal-pressure desulfurization and instead carry out pressure-driven desulfurization after conversion to remove hydrogen sulfide.