Investigation Of Flow Characteristics of Coal and Water Slurry

Abstract

The present study on the coal water slurry rheology was conducted at the Mechanical Engineering Department, Thapar University, Patiala. The influence of the coal particle size on the coal properties, rheological behavior of CWSFs, and packing characteristics of CWSFs was studied. Three Indian coal samples were procured from different thermal plants and were designated as S-I, S-II, and S-III and were investigated by using Anton Paar RheolabQC rheometer to generate extensive rheological data. The coal particle size was found to have a major influence on its proximate composition. It was observed that the inherent moisture was negatively correlated with particle size ranging from 53-106 μm. This implies that the inherent moisture does not cause coarsening of pulverized coal. It was also observed that a higher volatile content would favor coal pulverizing. The rheological results indicated that the viscosity of the CWSFs is a function of particle size distribution. A mixture of coarse and fine particles must be used for the preparation of CWSFs. A comparative study of uni-modal, bi-modal and tri-modal distributed slurries were made. The best coarse : fine ratios for bi-modal slurries for the three coal samples for which the lowest viscosity was observed, were found out. They were 70:30 (30f) for S-I, 40:60 (60f) for S-II, and 60:40 (40f) for S-III. It was also observed that the tri-modal distributed slurries showed a much lower viscosity when compared to uni-modal and bi-modal slurries, implying that CWSFs must be prepared with a variation of coarse and fine particles to achieve appreciable viscosity. The viscosity is also a function of temperature. With increase in temperature, the viscosity of the slurry was found to decrease owing to an increase in kinetic energy of the particles and a vi decrease in cohesive forces between the particles. This result was found to be common for uni- modal, bi-modal, and tri-modal slurries.