Research On Rheological Characterization And Effect On Sedimentation Dehydration Of Coal Slime Suspension

Coal slurry treatment is one of the most vital processes in Chinese coal preparation plant because of the wide use of wet cleaning method. It would hamper the other coal preparation process if coal slurry were not treated effectively. Slime water is the suspension consisting of water and solid particles including coal particles and various minerals. The rheological property of suspension is, therefore, related to characteristic of dispersed particles and scattered mediums, as well as environmental conditions. In this paper, rheological behavior and variable laws of coal slurry suspension under different conditions will be studied, fitting with the rheological equations. The slime suspension added different ion types of polyacrylamide is studied, analyzing the relationship between the settling dewatering effect and the rheological characteristic. The main conclusions are as follows:(1) Under different conditions, coal slurry suspension is a kind of plastic fluid exhibiting a shear-thinning characteristic which means the apparent viscosity of suspension will decrease with the increase of shear rate. The rheological curve is respectively fitted with Herschel–Bulkley model, Casson model and Bingham model. Compared with the other two fitting models, the fitting effect of Bingham model is reasonable, and the parameters of dynamic shear force in Bingham equation indicate the degree of dispersion of particles from the irregular movement to the directional rearrangement with the increase of shear stress.(2) Rheological property of suspension is affected by granularity which includes particle size and particle size distribution. The wider the distribution range is, the small the apparent viscosity is, and the smaller the particle size, the bigger the apparent viscosity is. The degradation of rheological behavior is caused by decreasing of particle density and increasing of solid content. The apparent viscosity of suspension falls with increasing of temperature and decreasing of water hardness.(3) Coal sample is oxidized by hydrogen peroxide. With the increasing of the concentration of hydrogen peroxide, the number of oxygen-containing functional groups is decreased while the apparent viscosity of coal slurry suspension is decreased. The rheological properties of slime suspension of long flame coal, coking coal, anthracite coal 3 different metamorphic grade and the surface property of which are studied. The best rheological property of coal slime suspension is long flame coal, followed by anthracite coal and coking coal. The number of oxygen-containing functional groups of long flame coal is the largest,followed by anthracite coal and coking coal.(4) The slime suspension of long flame coal added different ion types of polyacrylamide is studied, analyzing the relationship between the settling dewatering effect and the rheological characteristic. Nonionic polyacrylamide has less influence on the rheological property of suspension and greater benefit in setting and filter dehydration than other types of polyacrylamide. For other types of polyacrylamide, the effect of sedimentation dehydration and the rheological property can be improved simultaneously at a low dosage, and get worse when the addition is increased. Cationic polyacrylamide and amphoteric polyacrylamide have similar influence on the effect of sedimentation dehydration and the rheological property. The apparent viscosity of suspension adding anionic polyacrylamide is between that adding nonionic polyacrylamide and cationic polyacrylamide, however, the filtration characteristic is the worst.