Study of Ammonia Removal from Coal-Gasified Fuel

Abstract

In integrated coal gasification combined-cycle power-generation (IGCC) systems, ammonia in gasified fuel is passed through a hot/dry type gas clean-up facility into a gas turbine. The ammonia is converted to nitrogen oxides in the gas turbine combustion process. Therefore, ammonia removal from coal-gasified fuel effectively reduces NO x emissions in IGCC systems. We clarified the optimum NO/NH 3 ratio, the optimum concentration of added O 2, and the influence of CO, H 2, and CH 4 in the coal-gasified fuel on NH 3 decomposition and NO reduction through experiments using a tubular flow reactor and numerical analysis based on reaction kinetics. The main results were as follows: (1) The optimum NO/NH 3 ratio for maximizing NH 3 decomposition and NO reduction was about 1. (2) The NH 3 decomposition ratio depended only on H 2, and decreased rapidly with increasing H 2 concentration. (3) The NO reduction ratio decreased with an increasing H 2 concentration. (4) The remaining CH 4, which was not decomposed by pyrolysis, increased with an increasing CH 4 concentration and caused the reaction temperature to rise, as opposed to cases of CO and H 2. (5) The method was effective in decreasing total fixed nitrogen (TFN) by up to 40% and minimizing the total concentration of remaining NH 3 and NO in air-blown, coal-gasified fuel.