Cleaning and upgrading of low-rank coal using a novel rotary triboelectric separator with the polyvinyl chloride as friction medium

In this work, a novel laboratory rotary triboelectric separator was designed for the beneficiation of low-rank coal using polyvinyl chloride as the friction medium. The friction charge polarity of the different components in the low-rank coal was determined by charge-to-mass ratio measurements. The separation performance of the rotary triboelectric separator was investigated by separating the simulated materials. The surface properties of the simulated minerals were analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The influence of different conditions on the separation of low-rank coal was studied using rotation speed, feed rate and plate voltage as variables. Under the optimum operating conditions, the ash removal rates of 0.25-0.5 mm, 0.125-0.25 mm and -0.125 mm low-rank coals were 50.05 %, 61.88 % and 25.56 %, respectively. Inductively coupled plasma mass spectrometry (ICP-MS) analysis of the separated products indicated that several harmful trace elements (i.e., Cd, Cr, Pb and Sb) were removed distinctly. Our results will provide an effective way for the separation and upgrading of low-rank coal.