Experimental studies on the enhancement of coal-water slurry concentration and rheological properties of low-grade coal by combining waste engine oil with composite dispersants

As a new type of coal-based fluid fuel, coal water slurry (CWS) has been widely used in coal chemical industry, power generation, petroleum and other industries. For low-grade oil-rich coal, it is difficult to prepare high-quality CWS due to its low coalization degree and strong water absorption, and low free water content in the CWS. In this paper, waste engine oil (WEO) is utilized as a surface modifier that attaches to the coal surface to reduce the water content within the pores of the coal particles and decrease the interparticle viscosity. WEO is used as a surface modifier, with an addition amount of 0.2–0.5%. It adheres to the surface of coal to reduce the moisture content in the internal pores of coal particles and lower the viscosity between particles. When the addition amount of WEO is 0.4%, the maximum pulping concentration of CWS is 59%, and the apparent viscosity at this time is 1091 mPa·s (The industrial standard is < 1200 mPa·s). This work confirms that WEO is an effective additive, which can promote waste recycling and improve the rheological properties of CWS.