REDUCTION OF NITRIC-OXIDE OVER MAGNESIUM-OXIDE AND DOLOMITE AT FLUIDIZED-BED CONDITIONS

The reduction of nitric oxide over lime and char at fluidized bed cond itions has been studied by many authors, but less attention has been p aid to other surfaces existing in the boiler. This investigation conce rns the reduction of nitric oxide by carbon monoxide, with or without oxygen present, and also the effect of small amounts of water. The rea ctions were studied in a fixed-bed quartz reactor with quartz, magnesi um oxide, magnesium hydroxide, and dolomite as bed materials in the te mperature interval 600-950 degrees C. The residence time and the conce ntrations of nitric oxide, carbon monoxide, and oxygen were varied. Ma gnesium oxide formed from heated magnesium hydroxide and calcined dolo mite were more active than magnesium oxide of analytical grade, which indicates that the origin of the surface is important for the reaction . The reaction between nitric oxide and carbon monoxide is very sensit ive to the presence of oxygen. When oxygen was present the reduction o f NO almost ceased. However, if the gases were thoroughly dried, the e ffect of oxygen addition was not that severe.