Study on the Production of Ultraclean Coal

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Studies on the production of ultraclean coal were carried out. The results are summarized as follows;1) A total of six domestic and foreign coal samples were used. The basic properties were initially measured and the floatability, density of pure coal, calorific value and minimum limit of ash content were determined.2) Impurity minerals in coal were grouped into quartz, pyrite, kaolinite and iron oxide minerals. The changes of the size distribution of each mineral before and after crushing and gravity separation were utilized to determine their liberation characteristics.3) Based on the results of Inductively Coupled Plasma Automatic Emission Spectroscopy of high temperature ash, it was shown that the minimum limit of ash content depends on the type and amount of minerals which are difficult to remove. A new method for predicting the minimum limit of ash content was demonstrated.4) The effects of grinding parameters on grindability of coal were investigated. The wear of the internal pa … More rts of media agitated mill was caused by the hard minerals present in the coal. The grinding time needed to reduce the coal to a specified size was shortened by using a grinding media with smaller diameter and/or by increasing the speed of agitation.5) The estimation of liberation degree by using the liberation model developed from this research was demonstrated.6) A new type of flotation column was built and modified. Comparative experiments using the new flotation column and other conventional coal cleaning methods were carried out. The results showed that the new flotation column was effective even with fine particles which are difficult to recover in conventional methods.7) The deashing of ultrafine coal using the method of agglomeration in water was superior than that using the release analysis method. Proper selection of bridging liquid was needed for each coal. The method for predicting the amount of minerals and the ash content in clean coal was established. The predicted results were in good agreement with the measured values from the method of agglomeration in water. Less