Modelling the vacuum filtration of fine coal : Part 2

Abstract Wakeman's model has been applied to predict the kinetics of desaturating fine coal using vacuum filtration. The model was initially tested against experimental data, and then used to investigate, in a purely theoretical context, the effect of each of the main dewatering parameters on the rate of cake moisture reduction. These parameters, such as vacuum level, cake thickness, filtrate surface tension, filter cake permeability etc., were varied between the extreme limits which might be feasible in conventional fine coal filtration. It was found that increasing the filter cake permeability was the most effective way of increasing the moisture reduction rate, while reducing the filter cake thickness or increasing the vacuum exerted lesser, although still significant, beneficial effects. By comparison, the effects of increasing the coal/air/water contact angle or reducing the filtrate surface tension were small. Use of the model with the best combination of parameters identified, suggested that substantial advances in fine coal filtration are theoretically feasible, provided that an appropriate way of conditioning the slurry prior to filtration can be identified.