Gasifiers convert coal into synthesis gas feed streams that can be used in advanced power cycles to generate electricity and in the production of a wide variety of chemicals. However, the coal-derived synthesis gas contains a myrid of trace contaminants that cannot be released to the environment if the syngas is burned to generate power or may poison the catalysts used in the downstream chemical manufacturing process. Therefore, removal of these contaminants is critical for the widespread and environmentally-friendly utilization of coal.

TDA Research Inc. (TDA) is developing a sorbent-based system that can reduce the concentration of the trace metal contaminants (i.e., mercury, arsenic, selenium and cadmium) to less than parts per billion levels in the coal-derived synthesis gas at elevated temperatures (260C). This paper discusses the results of our sorbent development efforts.

In series bench-scale experiments, it is first shown that the sorbent is capable of removing Hg, As, and Se separately using simulated synthesis gas. The sorbent performance was also evaluated for combined removal of these contaminants. The impact of using syngas from different types of gasifiers (primarily the effect of steam partial pressure) and the presence of sulfur (as hydrogen sulfide and carbonyl sulfide) on sorbent performance were also evaluated. This paper will also summarize the results of a small-scale demonstration using real coal gas.