Effects of various parameters on ultrasonic comminution of coal in water media

•Ultrasonic treatment was used for comminution of coal in water media.•Effects of power level, treatment time, solid ratio and pulp temperature were investigated.•High degree of coal comminution was succeeded by ultrasonic treatment.•SEM and stereo microscope examination supported the test results.•Selective comminuting ability of ultrasonic treatment was revealed.

This paper investigates the potential use of ultrasonic treatment in comminution of coal in water media. A laboratory type, high intensity ultrasonic generator (750 W, 20 kHz) equipped with a horn transducer system and a titanium alloy horn tip (13 mm in diameter) was used as a source of ultrasonic treatment. The tests were performed at different levels of variables including ultrasonic power level (9.5–113.6 W/cm2), ultrasonic treatment times (5–20 min) and solid ratio of pulp (5–20% w/w). Temperatures of pulp atmosphere during ultrasonic treatment at different solid ratios and ultrasonic power levels were recorded. Particle size distribution curves were used to determine the degree of comminution. It was observed that ultrasonic treatment improved size reduction of coal significantly. Higher ultrasonic power levels and treatment times provided coal particles to be reduced to finer sizes. In addition, scanning electron microscope (SEM) and stereo microscope examinations were carried out to support test results. Selective comminuting ability of ultrasonic treatment was revealed from pyritic sulfur analysis for different size fractions of treated coal.