Effect of particle size distribution on rheology of high concentration limestone-water slurry for economic pipeline transportation

Abstract

The preparation of high concentration slurry requires careful selection of particle size distribution to achieve the required rheological properties for economic and efficient pipeline transportation. In the present study, the maximum static settled concentration (C-W-(max)) tests pertaining to limiting achievable concentration and rheological measurements were performed for limestone samples in the slurry concentration range of 60-78.5% by mass. The limestone samples with four distinct particle size ranges; i.e., <38, 38-90, 90-210, 210-300 mu m were used to prepare five representative experimental samples by blending the fines (<38 mu m) with other three coarse size ranges in definite mass proportions. The rheological behavior of the five limestone slurry samples with mono-modal, bimodal and multimodal packing characteristics indicated non-Newtonian flow behavior and fitted well to Bingham Plastic model in the concentration range of 60-78.5% by mass. The slurry samples with bimodal and multimodal packing characteristics indicated substantial reduction in slurry viscosity, yield stress and improved solids loading as compared to mono-modal one. The higher C-W-(max) values obtained for the specific blended (fines with coarse) limestone slurry samples were attributed to the packing effect and was correlated to the ratio of surface to surface separation for the coarse particles (beta) to the average fine particle size (d(50-f)) to achieve higher solids concentration. The reduction in slurry viscosity observed for the specific limestone samples was further substantiated by correlating the distribution modulus (psi) derived from Farris theory. It may be inferred that these theoretical treatments correlating the experimental data can provide highly reliable guidance to the preparation of high concentration limestone slurry for economic pipeline transportation.