SELECTIVE CATALYTIC-OXIDATION OF NH3 IN GASIFICATION GAS .1. EFFECT OF IRON SINTER AND DOLOMITE OIL THE REACTIONS OF NH3, NO, AND O-2 IN GASIFICATION GAS

Possibilities to selectively oxidize NH3 in gasification gas to N-2 ha ve been investigated. Either O-2 or NO or both oxidizers simultaneousl y were added to the hot synthetic gasification gas, which was led thro ugh a catalyst bed positioned in the electrically heated furnace. In t he empty reactor and in the nonporous quartz bed, only a slight NH3 re duction was achieved. When dolomite or iron sinter was used as catalys t, the added NO formed more NH3. The reactions of H-2 with NO in fact may limit the use of certain catalysts in gasification atmosphere. In the experiments with silicon carbide, the silicon carbide surface was oxidized to porous oxide layer, which catalyzed the selective oxidatio n of NH3 to N-2 at the temperature of 700-800 degrees C. Even with O-2 addition alone large NH3 reduction was achieved. At the same time, si gnificant NO formation was, however, noticed. The reason for the diffe rent behavior of the porous silicon dioxide layer, and dolomite and ir on sinter, is probably their different capability to adsorb various ga s species on their surface.