Environmental aspects of coal gasification

From the work so far, it is clear that certain areas will require further work to insure against unexpected or unacceptable environmental impacts. Some of these concerns result from a lack of sufficient information, others from a realization that present control technology needs improvement. Leaching of salts and trace metals from refuse and slag is one concern that calls for additional testing. Emissions of gas effluents also needs attention. While stack gas clean up can take care of sulfur in the flue gas from furnaces, the CO/sub 2/ vent stream from acid gas removal in some operating and projected plants is unsatisfactorily high in sulfur and combustibles. Waste water clean up is now receiving greater scrutiny, with emphasis on clean up and reuse to minimize or eliminate net discharges of waste water. Trace metals also call for special attention because some of them are partially volatile at conditions used in coal gasification, and build up in concentration in the gas clean up system or in the liquid byproducts and effluents. We do not consider these problems insurmountable, but recognize that evaluation and planning are needed now in order to develop control technology needed to avoid unexpected troubles in large scalemore » operations. In considering the potential environmental impact of a plant, the following must be considered: gas emissions, liquid effluents, solids disposal, water consumption, trace elements, thermal effluent, odor and taste, noise, visual impacts, and land use. The area of trace elements warrants special mention because a large number of toxic trace elements have considerable volatility in the gasifier and become concentrated in the raw gas clean up system. Specific methods will have to be developed for their recovery or proper disposal.« less