Enhancing flotation cleaning of intruded coal dry-ground with heavy oil

Intruded coal is one type of unconventional coal resources in many coal fields of China. The research into the flotation of intruded coal has not received enough attentions. Plenty of intruded coal fines are produced during coal mining, screening and gravity separation. However, the intruded coal fines are difficult to float using common oily collectors because the intruded coal surface is porous and naturally hydrophilic. In this investigation, heavy oil was used as a collector associated with dry-grinding process to enhance the flotation recovery of intruded coal. The flotation recovery of intruded coal dry-ground with heavy oil was 82.40% which was higher than that (71.28%) of coal dry-ground with kerosene. The mechanism of heavy oil enhancing the flotation recovery of intruded coal was fully discussed by a combination of Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), attachment time measurements. FTIR results showed the heavy oil contained more unsaturated hydrocarbon and oxygen containing groups than the kerosene. The coal-bubble attachment was greatly improved because the attachment time was reduced after the dry-grinding with collectors. The intruded coal surface hydrophobicity was effectively improved by heavy oil through the adsorption of heavy oil drops, which made bubble catch intruded coal particles readily. In addition, the pores of intruded coal surface were filled by plenty of crushed coal fines during the dry-grinding process, which enlarged the contacting area for coal-bubble attachment.