Study on pulping performance of a novel coal water slurry additive for Shenhua coal slurry with high concentration
Shenhua coal is difficult to form slurry of high concentration, low viscosity for its strong hydrophilicity. Based on that, coal water slurry (CWS) additive, denoted as LS-A, was used to prepare Shenhua coal blending slurry with high concentration, and then the slurry ability, rheological characteristic and static stability of LS-A were investigated. The results show that, the performances of CWS were improved by LS-A, and it had good viscosity reducing effect. The slurry concentration could reach 65.5%, and the apparent viscosity is smaller than 1200 MPa·s with good flow property under 100 s-1 of shearing rate when the dosage of LS-A was 0.7%. The rheological investigation indicated that the slurry pumped with LS-A is pseudoplastic fluid, and it had rheological property of shear-thinning, evident thixotropic property and good stability. Moreover, the comparison of pulping properties and stability between LS-A and the additive SPHF-3 of National CWS Center showed that, the slurry ability was similar under same additive dosage.
Rheological Behavior of Coal-Water Slurry
The rheological behavior of some Indian coal-water slurry (CWS) was investigated using a HAAKE RV30 viscometer. The objective was to study the effect of solid concentration, ash content, pH, and temperature on the rheology of CWS. It was found that CWS exhibits pseudoplastic behavior. The apparent viscosity varies with the amount of coal in the slurry, pH, and temperature, which is the highest around pH 6 and the lowest near pH 8. The effect of temperature on the viscosity could be described using an Arrhenius type of relation.
Effect of temperature on the flow properties of suspensions
Fine powder of CaCO3 was dispersed in H2O, ethylene, glycol (EG), and 50% aqueous solution of polyethylene glycol (PEG). In all cases, the apparent viscosity, η, of the suspensions decreased with temperature. The results are discussed on the basis of the energy dissipation theory. The total energy dissipation of flow, ET(=ηaD2), per cm3 per sec was divided into two terms, i.e., Ep due to the interaction of flow units (flocs) and Ev, the viscous energy. Ev plays a dominant role when the viscosity of the medium, ηo, is large (e.g., for EG), whereas Ep is responsible for the overall flow behavior for the system with small ηo (e.g., for H2O). From the analysis of Ep with respect to the rate of shear, D, and the effective floc concentration, a parameter m2 was obtained, which is independent of D and of solid concentration, and serves as a measure of the extent of energy dissipation due to the interaction between flocs.