A laboratory-scale, batch operated gasifier was used to evaluate the heating value, process and cooling water requirements, and water pollution potential of gasification of carbonaceous shales. These potentially valuable fossil fuels are found over large areas of Southern and Eastern Utah and vary widely in quality depending on the amount of intermixed inorganic material. The results indicate that a synthesis gas, consisting primarily of hydrogen and carbon monoxide, can be produced from carbonaceous shales. The total heating values of the synthesis gas from the carbon shales examined ranged from 4 to 62 percent of that of coal. The process water requirements per unit of heating value obtained for gasification of the carbonaceous shales tended to be 5 to 15 percent higher than that for coal. Cooling water requirements were similarly higher due to the greater quantity of ash quenching water needed for the shales. The quantity of phenols, ammonia-N, and total organic carbon produced from the gasification of coal was significantly greater than for either of the shales, when compared on a mass basis. Differences in process condensate constituents, such as mutagenicity and trace elements, were also determined for the coal and shale samples.

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The Water Requirements and Pollutant Potential in the Gasification of Carbonaceous Shales

Many factors may affect the formation and disposition of minor and trace constituents in coal gasification processes, e.g., the coal feedstock, the gasification conditions, and the gas processing conditions. Adequate knowledge of the forms and amounts of these constituents and the controlling factors which dictate their final disposition would be desirable for the complete design of a full scale plant. However, the current data base is weak for some of the more volatile inorganic trace constituents that may be gasified with the coal. In this paper, theoretical projections are made on the amount and final disposition during coal gasification of volatile trace constituents formed from arsenic, boron, lead, selenium, and mercury present in coals. Note that these predictions are theoretical; they are intended to provide insight into what might occur in coal gasification processes, to provide direction for future experimental work for improving the data base on these constituents, and to indicate areas where further investigations would prove useful for the design of full scale processes. The results of these studies indicate that high recoveries of these trace inorganics are to be expected, with low discharge to the environment, in most coal gasification process designs.

D.K. Fleming

Papers

Predictions of the disposition of select trace constituents in coal gasification processes