Effect of hydroacoustic cavitation treatment on the spiral processing of bituminous coal

Testing was conducted to evaluate the effects of hydroacoustic cavitation (HAC) treatment on spiral separation when processing nominal -1500 m Illinois-basin bituminous coal. Cavitation was produced either by flow through an ultrasonic resonator chamber or enhanced cavitation by initial flow through a cavitation box followed by flow through the ultrasonic chamber. After treatment, the slurry was passed through a hydrocyclone for desliming, and the underflow stream was used as spiral feed. Spiral tests were carried out using a two-stage spiral at three volumetric flow rates for different HAC treatment conditions. HAC treatment reduced the overall size distribution of the spiral feed material. Likewise, desliming of the treated material led to a reduction in the ash values for each size interval. For example, after HAC treatment, the ash value of the deslimed material was reduced to 25% compared to 41% for the untreated deslimed material. Subsequent spiral separation of the treated material produced clean coal with an ash value of 15% at a yield of 79% compared to an ash value of 18% at a yield of 59% for the untreated material. HAC treatment had only a minimal effect on sulfur reduction.