Other Gasification Systems

In addition, other gasification systems will be touched on and displayed in the diagram (e.g., carbon dioxide (CO2)-gasification, biomass). 

As part of our total gasification program, we have made numerous design and cost studies to evaluate our process ideas as well as process systems being pursued by others. The comments that I will make today are based on the understanding of gasification systems that we have developed from this work. 

One other problematic ingract of the tars within gasification systems is the condensation of heavy PAHs on fly ash particles. Since most of PAHs have hazardous properties, study of the PAH capture on fly ash becomes of vital importance. 

Oxidation of sulfite to sulfate can proceed by mechanisms other than those involving oxygen from air. The reaction kinetics and the mechanics are not yet understood, but our experiments show that oxygen-free sulfite in lime/limestone slurries, exposed to sulfur dioxide, slowly decomposes under process conditions. In fact, our experiments indicate that auto-redox reactions of sulfur oxyacids can occur in all coal desulfurization systems, including coal-gasification systems and that impurities present in commercial flue gas systems are capable of catalyzing the reaction under process conditions. 

Conventional Wet Scrubbers. Wet scrubbers are used for final particulate control in all currently operated coal gasification systems except those that operate at atmospheric pressure. (Low-pressure gasification systems use electrostatic precipitators.) High operating pressure allows for operation at reasonably high pressure drops, making scrubbers very small, efficient, and inexpensive. Scrubbers also remove ammonia, chlorides, and other trace components from the gas. The scrubber blowdown water is subsequently steam stripped, and the stripped gas sent either to the Claus plant or an incinerator. 

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