Selective catalytic oxidation of NH3 in gasification gas: 3. Experiments at elevated pressure

In this study the ability of aluminum oxide to catalyze the selective oxidation of NH3 in hot pressurized (20 bar) synthetic gasification gas was examined. When the mixture of NO and O₂ was used as oxidizer, it was found that part of the NO may be converted to NO₂ in the gas feeding system. It was found that the ratio of NO/NO₂ in the oxidizer mixture can be controlled by controlling the residence time and the temperature of the gas feeding system. Increasing the pressure increased the rate of NO₂ formation. When the oxidizer consisted of NO₂ and O₂, large NH₃ conversion was attained below 500 °C. With NO and O₂ addition into the hot gasification gas the highest NH₃ conversion took place at 550 °C. The addition of O₂ alone to the aluminum oxide bed at high pressure reduced also the NH₃ content of the gas. It was shown that aluminum oxide catalyzes the reaction between NH₃ and O₂.