Main operating conditions for Klaus sulfur recovery

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The equilibrium conversion rate of the Claus reaction is highest when the ratio of H2S to SO2 in the process gas is 2. The H2S/SO2 ratio is the most important operating parameter of the unit, and this ratio is controlled by adjusting the gas-to-air ratio. In addition to setting proportional control for the flow rates of air and acidic gases (primary adjustment), considering the impact of changes in the composition of acidic gases on the H2S/SO2 ratio, online analyzers are typically installed after the final condenser (or trap) to provide feedback control (fine adjustment) of the air volume. 　　The operating temperature of the reactor depends not only on thermodynamic factors but also on the sulfur dew point and gas composition. From a thermodynamic perspective, the lower the operating temperature, the higher the equilibrium conversion rate; however, if the temperature is too low, sulfur vapor will condense on the surface of the catalyst, causing it to become inactive. Therefore, the temperature of the process gas entering the reactor should be at least 10–30°C higher than the dew point of sulfur vapor. 　　The hydrolysis reactions of COS and CS2 in the process gas increase as the temperature rises. To reduce the loss of sulfur in the form of COS and CS2, industry generally adopts the approach of raising the temperature of the process gas at the inlet of the primary reactor to promote the hydrolysis of COS and CS2, and uses secondary or tertiary reactors to compensate for the decrease in equilibrium conversion rate resulting from the increased temperature. When a regeneration exhaust gas treatment device is installed downstream, there is no need to increase the inlet temperature of the process gas in the primary reactor, as COS and CS2 are easily hydrolyzed in the hydrogenation reactor of the exhaust gas treatment device.