Improvement of low-quality fine coal by ultrasonic hydrophobic flocculation

Abstract

ABSTRACT In this study, the effect of ultrasonic pretreatment on hydrophobic flocculation of fine coal was investigated and named as ultrasonic hydrophobic flocculation (USHF) technique. First, it was found that the ultrasonic power of 150 W and the ultrasonic pretreatment time of 180 sec was required to achieve for more combustible and good-quality coal. Then, the effects of ultrasound on the hydrophobic flocculation of coal with kerosene as bridging liquid were investigated and optimum kerosene concentration value was obtained 4 g/dm3 under the experimental conditions. Also, it was found that a stirring speed of 750 rpm was sufficient to achieve the maximum combustible recovery and minimum ash content values of fine coal particles. The effects of sodium silicate, sodium hexametaphosphate, and sodium pyrophosphate used as inorganic dispersants on the ultrasonic hydrophobic flocculation of coal were also studied. Sodium silicate was more effective than other dispersants in the presence of kerosene. Thus, it was concluded that the ultrasonic pretreatment is an effective method for the beneficiation of fine particle coal. Coal with an ash content of 17.63% was enriched and clean coal was recovered with an ash content of 9.75% with the efficiency of 94.35% by ultrasonic hydrophobic flocculation technique.