The mineralogy and inorganic geochemistry of coal and combustion products from the Mae Moh Mine, Thailand: Environmental implications of resource utilization.

摘要

The coals, associated sediments and combustion products, from the Tertiary, Mae Moh Lignite Mine Lampang, Thailand, have been investigated using XRD, XRF, NAA and SEM/EDS. The investigation is primary aimed at documenting the overall mineralogy and geochemistry of the coal and combustion products, in an attempt to briefly describe the local environmental impacts of resource utilization.; Ash content in composite run of mine samples in three important (J, K and Q) coal zones averages 44%. Ash in the power plant feed coal averages 41%. Dominant mineral phases in the zones include: detrital quartz, illite and kaolinite along with authigenic calcite and pyrite. The detrital minerals plus pyrite dominate the lignite horizons while calcite dominates the intra-seam partings.; The highest ash content and major element (Si, Al, Ca, Fe, K and S) concentrations in coal is reported in samples from J zone. There is an overall decrease in ash and major element concentration from J to Q zones. These coals are particularly high in S ranging from 0.3 to 14%, with an average of 8%.; As with the major elements, the trace elements are enriched in J zone, particularly in the upper portion, and show an overall concentration decrease from J to Q zone. The As content of these coals, which ranges from 3 to 488 ppm with an overall average of 60 ppm, is significantly higher than the reported global average.; The minerals identified in the combustion products include quartz, magnetite, hematite, anhydrite, mullite, gehelenite, anorthite and clinopyroxene. Silicon, Al, Fe and Ca, which account for more than 90% of the major elements in the ash, show little partitioning between samples of bottom ash (BA) and electrostatic precipitator ash (ESP). Arsenic, Co, Cr, Mo, Sb, Se, U and Zn, which are all enriched in samples of ESP ash relative to BA, show a distinct concentration increase with decreasing particle size.; Based on an annual coal consumption of approximately 16 million tons, 6.5 million tons of ash, which contain significant proportions of potentially toxic trace elements, are produced annually. Calculations show that for most trace elements selective mining would result in an annual emission reduction of 20 to 50%. For these elements cleaning the coal prior to combustion could produce a 30% decrease.