Effect of ultrasonic cavitation treatment on liberation and hydrocyclone separation of bituminous coal

Abstract

Testing was conducted to evaluate the effects of hydroacoustic cavitation (HAC) treatment on two bituminous coal slurries and the subsequent separation of each slurry in a classifying hydrocvclone. HAC treatment was performed using a pilot-scale circuit fabricated by Fumess-Newb urge Inc. The circuit was designed to induce cavitation by means of flow through an ultrasonic resonator chamber or enhanced cavitation by initial flow through a cavitation chamber followed by flow through the ultrasonic chamber. The test materials were nominal −1,500-micron and −150-micron lllinois-basin bituminous coal slurries, which were obtained from an operating coal preparation facility. After 5 sec of HAC treatment, the median size of the −1,500-micron material was reduced, with ash values for certain size fractions decreasing more than 5 percent compared with untreated samples. Extending treatment time led to greater degradation of the +1,180-micron material and an increase in the −25-micron material, with ash reductions occurring for material in the −850+150-micron size range. Size degradation was less for the −150-micron material. Subsequent separation of the treated slurries was carried out in a hydrocvclone with diameter of 102 mm. HAC treatment led to a decrease in the ash value and an increase in the heating value of the underflow stream compared with the feed material. For example, the ash value was reduced by about 16 percent for the −1,500-micron material and 25 percent for the −150-micron material with heating value increases of 7 and 33 percent, respectively, after HAC treatment. Overall, HAC treatment appeared to have a slight effect on the size selectivity curves.