Abstract
The experimental determination of mineral matter in coal is a tedious as well as time consuming process, and requires highly skilled analyst to carry out the chemical analysis of coal and ash. On the other hand, determination of moisture and ash is relatively easy using moisture oven and muffle furnace and can be determined anywhere with little care. Most of the methods reported till date for the evaluation of mineral matter in coal involves indirect determination of mineral matter using high temperature ash as one parameter. All these methods offer conversion of ash yield into mineral matter with the help of correlations based on certain assumptions. Although, the method for direct determination of mineral matter by chemical analysis is also reported, but is of little use as it requires extensive chemical analysis. In this study mineral matter is determined directly by oxygen plasma asher in coal samples collected from different regions of India. The results obtained were compared with those obtained by existing correlations. It has been observed that all the existing correlations including Parr’s, are found to be unrealistic for high ash Indian coal. An attempt has been made to develop a new correlation for the estimation of mineral matter based on two simple parameter i.e. moisture content and ash yield. Present model was developed after analyzing 75 coal samples. The developed correlation appears to be more simple and better and is represented as Mineral Matter(MM)= 0.74(Moisture) + 1.17(Ash)
Highlights
Coal is a solid fossil fuel and it incorporates inorganic materials from the original swamp environment or any that may have been washed or blown into the accumulating coal seam
The mineral described as “mineral matter” (MM) in coal encompasses dissolved salts in the pore water and inorganic elements associated with the organic compounds, as well as discrete crystalline and non-crystalline mineral particles [1]
Indian coals suffer from the great disadvantage that the mineral matter content is high and of an intimately associated [2] [3] type due to its drift origin
Summary
Coal is a solid fossil fuel and it incorporates inorganic materials from the original swamp environment or any that may have been washed or blown into the accumulating coal seam. Precise determination of the mineral matter percentage in coal by low temperature ashing involves correcting the oxygen-plasma ash yield for any un-oxidised organic carbon residues, and for any sulphur fixed in the low temperature ash from the organic sulphur component [10] These are often relatively small corrections, and for many purposes the proportion of low temperature ash gives an adequate indication of the percentage of mineral matter present [1]. Five coal samples of varying ash content were taken to compare the results of MM obtained by existing correlations and experimental MM. The ash of these samples ranges from 30.7 to 45.3 percent. The Gondwana coals, from which the thermal coals are drawn, are generally found to be intimately mixed with fairy large proportion of mineral matter resulting in ash yields of 30 to 60 percent on air dried basis [11]
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