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Show 2 INTRODUCTION Trace element emissions pose a potential problem to two emerging coal gasification electric power-generating systems: integrated gasification combined cycle (IGCC) and integrated gasification fuel cell (IGFC) systems. The potential problems associated with trace elements are the release of substances that are considered air toxics and the degradation of fuel cell efficiency due to contamination with minor elements. In order to develop effective technologies to control trace element emissions within anticipated regulatory requirements and to ensure the efficient operation of fuel cells, the type and quantity of trace elements emitted from coal gasification-based systems must be determined as a function of system, system conditions, and coal composition. This paper is a result of initial work being performed to identify the important physical and chemical transformation mechanisms of selected trace elements during gasification as a function of coal composition (trace element abundance and association) and gasification conditions. The fate of trace elements in coals used in IGCC and IGFC systems is closely tied to how the trace elements are associated in the coal and the gasification conditions. Trace elements in coals are associated in several forms, including organic associations, such as salts of carboxylic acid groups and organic coordination complexes, and mineral associations, such as sulfides, sulfates, silicates, phosphates, and carbonates (1-7). Coal trace metals of primary concern include As, B, Cd, Hg, Mo, Ph, Se, Cr, Cu, Ni, V, and Zn (1-3). During gasification, these inorganic elements are partitioned into gases, liquids, and solids. The transformation of these trace elements into the various states and phases depends upon the fundamental characteristics of the elements and their association with minerals and coal particles. The primary transformations that occur to major and minor trace species during coal conversion are illustrated in Figure 1. The two principal paths |
