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 NOx emissions in coal gasification power plants. Since the decomposition reaction is equilibrium limited at gasification conditions, a membrane reactor is necessary to achieve a high conversion of ammonia to nitrogen and hydrogen. The objective of this study was to experimentally demonstrate the use of a membrane reactor 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 membrane was used in the membrane reactor. Ammonia conversions from the packed 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 conversion of over 94% was achieved in the membrane reactor compared to a conversion of 53% in the conventional reactor at a temperature of 873 K and pressure of 1618 kPa. The advantage of the membrane reactor is even more pronounced at lower temperatures. The ammonia conversion at 823 K was 79% in the membrane reactor compared to a conversion of only 17% in the conventional reactor. Experimental results are also compared to those predicted by a membrane reactor model. The experimental conversions and conversions predicted by the model generally showed good agreement. The percent difference between predicted and experimental conversions was generally less than 10%.