Trace Element Studies on Coal Gasification Process Streams

摘要

The primary endeavor of this research was to attempt to elucidate some of the elemental chemistry that is operative during coal gasification. Several significant aspects of trace element chemistry were either confirmed or established. A comprehensive, 65 to 70 element spark-source mass spectrometric survey of all process streams (excluding the product gas) was conducted for the purposes of determining elemental distributions and to attempt to relate these distribution patterns to various physiochemical parameters of the gasification process. The results revealed several important points. The gasifier char material was the major repository for most of the trace and minor elements. This conclusion agrees with data of others and is important since this material will either be further utilized for process heat or be disposed of. In either case, recognition of the high and potentially hazardous levels of certain elements will be required. Studies are therefore needed to delineate the chemistry and fate of these elements during combustion and/or disposal of this char material. Very volatile elements were found to exist in significant concentrations in the condensable water and tar by-products of the coal gasification unit. A major fraction of the Se in the effluent streams was found in the condensate water. The water and tar material was also heavily concentrated in sulfur. It is believed that Se may be hydrogasified or volatilized (as H sub 2 Se) in much the same manner as sulfur is converted to H sub 2 S during the gasification process. Although a significant portion of the Se deposits in the condensate water, much of it is not accounted for in the process streams analyzed. This suggests that it is lost in the product gas. Partial volatilization of As (as AsH sub 3 ) may also be inferred from the data. (ERA citation 04:025211)