Oxidized oil shale for removal of nitrogen oxides in combustion gas streams

Abstract

Oxidized oil shale from the combustor in the Lawrence Livermore National Laboratory (LLNL) hot recycled solids (HRS) oil shale retorting process has been found to be a catalyst for removing nitrogen oxides from laboratory gas streams, using NH 3 as a reductant. Oxidized Green River oil shale, heated at 10 °C min −1 in an Ar/O 2/NO/NH 3 mixture (~93%/6%/2000 ppm/4000 ppm) with a gas residence time of ~0.6 s, removed NO between 250 and 500 °C, with maximum removal of 70% at ~400 °C. Under isothermal conditions with the same gas mixture, the maximum NO removal was ~64%. When CO 2 was added to the gas mixture at ~8%, the NO removal dropped to ~50%. However, increasing the gas residence time to ~1.2 s, increased NO removal to 63%. Nitrogen balances of these experiments suggest selective catalytic reduction of NO is occurring using NH 3 as the reductant. These results are not based on completely optimized process conditions, but indicate that oxidized oil shale is an effective catalyst for NO removal from combustion gas streams using NH 3 as the reductant. Parameters calculated for implementing oxidized oil shale for NO x remediation on the current HRS retort, indicate an abatement device is practical to construct.