Viscosity-temperature characteristics of high-concentration coal-oil slurry preheated by light solvent

The viscosity and stability of coal-oil slurry (COS) with different concentrations prepared by recycle solvent and low-rank coal were investigated. The effect of light solvent naphtha preheating treatment on the viscosity-temperature characteristics of high-concentration COS and properties of pulverized coal was studied. Results show that when the concentration is higher than 48 wt%, the viscosity and swelling viscosity peak value of conventional COS increase exponentially, resulting in the significant deterioration of the stability of COS. The concentration of COS can be increased to 50 wt% by preheating with light solvent. With the increase of preheating temperature and time, the viscosity of COS decreases as a whole. The viscosity of high-concentration COS with the optimum preheating temperature of 375 °C and time of 4 h is 383 mPa·s (60 °C), which is 30% lower than that of conventional COS (543 mPa·s (60 °C)) with 50 wt%. Due to the influence of the full swelling, irreversible swelling, and primary pyrolysis of pulverized coal, the physical structure and chemical composition of pulverized coal changes, the swelling viscosity peak no longer appears, and the stability of COS is improved.