System Issues and Tradeoffs Associated with Syngas Production and Combustion

The purpose of this article is to provide an overview of the basic technology of coal gasification for the production of syngas and the utilization of that syngas in power generation. The common gasifier types, fixed/moving bed, fluidized bed, entrained flow, and transport, are described, and accompanying typical product syngas compositions are shown for different coal ranks. Substantial variation in product gas composition is observed with changes in gasifier and coal feed type. Fuel contaminants such as sulfur, nitrogen, ash, as well as heavy metals such as mercury, arsenic, and selenium, can be removed to protect the environment and downstream processes. A variety of methods for syngas utilization for power production are discussed, including both present (gas turbine and internal combustion engines) and future technologies, including oxy-fuel, chemical looping, fuel cells, and hybrids. Goals to improve system efficiencies, further reduce NOx emissions, and provide options for CO2 sequestration require advancements in many aspects of IGCC plants, including the combustion system. Areas for improvements in combustion technology that could minimize these tradeoffs between cost, complexity, and performance are discussed.