CATALYTIC DECOMPOSITION OF AMMONIA IN A MEMBRANE REACTOR

Catalytic decomposition of ammonia in the gas feed to the turbine is a potential method for reducing NO, emissions in coal gasification powe r plants. Since the decomposition reaction is equilibrium limited at g asification conditions, a membrane reactor is necessary to achieve a h igh conversion of ammonia to nitrogen and hydrogen. The objective of t his study was to experimentally demonstrate the use of a membrane reac tor for ammonia decomposition at temperatures, pressures, and ammonia, nitrogen, and hydrogen concentrations within the range of conditions found at coal gasification plants. A composite palladium-ceramic membr ane was used in the membrane reactor. Ammonia conversions from the pac ked bed membrane reactor are compared to experimental conversions from a conventional packed bed reactor operated under identical conditions to show the advantage of using the membrane reactor. An ammonia conve rsion of over 94% was achieved in the membrane reactor compared to a c onversion of 53% in the conventional reactor at a temperature of 873 K and pressure of 1618 kPa. The advantage of the membrane reactor is ev en more pronounced at lower temperatures. The ammonia conversion at 82 3 K was 79% in the membrane reactor compared to a conversion of only 1 7% in the conventional reactor. Experimental results are also compared to those predicted by a membrane reactor model. The experimental conv ersions and conversions predicted by the model generally showed good a greement. The percent difference between predicted and experimental co nversions was generally less than 10%.