Improving slurryability, rheology, and stability of slurry fuel from blending petroleum coke with lignite

Petroleum coke and lignite are two important fossil fuels that have not been widely used in China. Petroleum coke-lignite slurry (PCLS), a mixture of petroleum coke, lignite, water, and additives, efficiently utilizes the two materials. In this study, we investigate the effects of the proportion (alpha) of petroleum coke on slurryability, rheological behavior, stability, and increasing temperature characteristics of PCLSs. The results show that the fixed-viscosity solid concentration (omega(0)) increases with increasing alpha. The omega(0) of lignite-water slurry (LWS, alpha = 0) is 46.7 %, compared to 71.3 % for the petroleum coke-water slurry (PCWS, alpha = 100 %), while that of PCLS is in between the two values. The rheological behavior of PCLS perfectly fits the power-law model. The PCWS acts as a dilatant fluid. As alpha decreases, the slurry behaves first as an approximate Newtonian fluid, and then turns into a pseudo-plastic fluid that exhibits shear-thinning behavior. With increasing alpha, the rigid sedimentation and water separation ratio (WSR) increase, indicating a decrease in the stability of PCLS. When alpha is 60-70 %, the result is a high-quality slurry fuel for industrial applications, which has high slurryability (omega(0) = 57-60 %), good stability (WSR < 2 %), and superior pseudo-plastic behavior (n approximate to 0.9).