Catalytic oxidation of H2S in Claus tail gas and subsequent removal of SO2 by wet scrubbing

摘要

Concentrated H2S gases from refineries are commonly treated in Claus plants. However, the tail gas from a Claus plant will contain small amounts of H2S due to equilibrium limitations of the Claus reaction. A new technology for catalytic oxidation of H2S in Claus tail gas is now offered by Haldor Topsoe. Oxidizing H2S to SO2 allows for cheap sulphur capture by wet scrubbing. The technology uses a novel catalyst (Sulphur Monolith Catalyst, SMC?) that is characterized by almost complete conversion of H2S to SO2 and with negligible oxidation to SO3. Since the catalyst has a monolith structure the pressure drop and tendency to physical plugging is low. The catalyst requires an inlet temperature of approximately 250 °C. This temperature is obtained using a feed-effluent heat exchanger, where the heat of reaction in the SMC reactor is transferred to the feed gas and thus support fuel can be avoided during normal operation. The slip of H2S is extremely low and typically below 3 ppm. A Claus tail gas cleaning by SMC reactor plus wet scrubber will combine low capital and low operational expenses unlike most other Claus tail gas technologies.