Model to predict packing efficiency in coal water slurry: Part2 prediction and application

Abstract

Increasing the solid loading of coal water slurry (CWS) by 1 wt% in the gasification process can reduce the emission of CO2 by 15 million t/a indirectly in China alone. The compartment packing model can guide the preparation of CWS with lower viscosity, and thus increase solid loading. In this paper, the verification, discussion and application of the compartment packing model on the prediction of the viscosity are conducted, which also shows some interesting findings. The packing efficiency obtained by the compartment packing model can clearly point out the sample with the lowest viscosity, though the viscosity and solid loading of the samples are quite different. Moreover, the trend of viscosity from different gradation groups can also be illustrated on the order that the higher the packing efficiency, the lower the viscosity. For CWS made by Hailar coal at 45 wt%, the packing efficiency increases from 72.9% to 82.3%, the viscosity decreases to accordingly from 1862 mPa·s to 411 mPa·s. It is found that the traditional experience (double peak or three peak particlegradation) is not valid to design a particle size distribution (PSD) for lowest viscosity. The effective index for PSD with lowest viscosity is the packing condition that the fine particles efficiently fill all the void of the large particles, namely the highest packing efficiency. Therefore, the concept of systematic gradation is proposed that at same concentration and additive, the slurry with lowest viscosity can be predicted by the highest packing efficiency, which can be screened out by the compartment packing model from all the possible combination of grinded samples.