Optimization of the oil agglomeration for high-ash content coal slime based on design and analysis of response surface methodology (RSM)

Oil agglomeration is an alternative technique for the cleaning and upgrading of low-rank coal or high-ash content coal slimes. Therefore, this approach was used to beneficiate coal slime with high-ash content of 31.34% in this work. The single-factor tests of oil agglomeration were performed to determine the appropriate ranges for various operational factors, including pulp concentration, reagent concentration, and agitation speed. The separation results suggested that considering the yield and ash content of clean coal, and combustible material recovery, the optimal pulp concentration and reagent concentration should be adjusted as 12%-16%, and 20%-24%, respectively, and the optimal agitation speed should be controlled as 800-1200 rmin. The Response surface methodology (RSM) based on Box-Behnken design (BBD) was adopted to investigate the significance of various operational factors, and the interactions between various operational factors on the response of combustible material recovery. A mathematical model was established to predict the response, and the results indicated that the established model was proved to be highly accurate in the prediction of response. The optimization of the solutions suggested that the maximal combustible material recovery of 97.49% was obtained with the pulp concentration of 12%, reagent concentration of 20%, and agitation speed of 1200 rmin. This work provides an experimental foundation for the operation design and process optimization in the oil agglomeration of coal slimes.