Abstract
Coal undergoes a series of beneficiation processes that aims at extracting as much coal as possible in all size fractions. However, there are over 30 billion tons of coal fines and ultrafines discarded in the top ten coal producing countries. The study aims to contribute to the ongoing research on the beneficiation of fine and ultrafine coal by focusing on the optimization of the hydrocyclone process as a pretreatment stage on the beneficiation of fine and ultrafine coal. The coal attributes were understood by using sieves for the particle size distribution (PSD), Xray fluorescence (XRF) for elemental analysis, X-ray diffraction (XRD) for mineral phase identification, calorific value (CV), and proximate analysis for coal ranking. The project made use of the Taguchi design of experiment to optimize the hydrocyclone classifier. The parameters investigated were the % solids, spigot size, F80, and inlet pressure. The parameters were optimized in response to obtaining low percentage ash, high coal yield, high CV, large d50, low % passing 150μm, and high % separation efficiency. Chemical analysis revealed that major gangue elements associated with ash-bearing minerals were Si and Al assaying at 23.3% and 13.37% respectively. Proximate analysis showed that the coal sample contained 34.03% ash, 1.37% moisture, 24.02% volatile matter and 40.58% fixed carbon content by calculation. The calorific value and the sulphur content were determined to be 19.66 MJ/kg and 0.69% respectively. The results revealed that the level of parameter significance varies depending on the response variable. However, with regards to the CV, the parameter level of significance was observed to be distributed equally. With the application of ANOVA and multiple regression analysis, models were developed which assisted in studying the parameter effect and parameter interaction of operational and response variables. The models for ash %, % coal yield, d50, % passing 150μm, and CV obtained R2 that ranges greater than 80% with p-values of less than 0.05. The % separation efficiency obtained R2 of 59.95% with a p-value greater than 0.05. The standard estimate error of regression was higher for the d50 as compared to other response variables. The optimized parameters for the operation of the hydrocyclone were 10% solids, 20mm spigot size, 770μm F80, and the inlet pressure of 50kpa. The optimum results were: % ash of 23.71%, the calorific value of 23.06MJ/kg, coal yield of 79.18%, % separation efficiency of 84.34%, d50 of 465μm, and % passing 150μm of 25.23%. However, when the model's accuracy was tested, the response obtained was 25.81% ash, 23.74 MJ/Kg CV, 83.00% yield, the % separation efficiency of 93.50%, d50 of 462μm, and % passing -150μm of 30.43%...
M.Tech. (Extraction Metallurgy)