Preparation of semicokes by medium–low temperature pyrolysis of long flame coal and their adsorption performance on sodium lignin sulfonate dispersant for high concentration coal water slurry

To get a high concentration of coal water slurry (CWS) for gasification application, semicokes were prepared by pyrolysis of Dongrong long flame coal (DRC) at medium–low temperature. The obtained semicokes were characterized by thermogravimetry, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, and nitrogen adsorption-desorption methods. After preparation, the adsorption experiment of sodium lignin sulfonate (NaLS) on these semicokes was also carried out. It was found that medium–low temperature pyrolysis have changed the pore structure, surface properties, and molecular structure of DRC, which increased the saturated adsorption capacity of semicokes for NaLS dispersant. The enhanced adsorption capacity for dispersant can significantly reduce the apparent viscosity of CWS and increase its concentration. Under the optimized pyrolysis conditions, the maximum solid concentration of CWS prepared with as-prepared semicokes reached up to 68.09% when the dosage of NaLS disperdant was 1%, which met the gasification application of CWS. Such medium–low temperature pyrolysis method is an effective way to large-scale development and utilization of low rank coal through modifying their physicochemical properties.