MODELING THE VACUUM FILTRATION OF FINE COAL

The dewatering of fine coal using vacuum filters is widespread in Aust ralia, and is very important to the coal industry since the fines frac tion of the product coal can contain up to 50% of the moisture. Optimi sing and maintaining filter performance can only be achieved with the aid of a suitable model applied at plant scale. As a first step toward s such optimisation, the paper describes bench-scale studies to assess a model, devised by Wakeman in the late 1970s, for calculating both m oisture reduction kinetics and gas consumption during fine coal filtra tion,The model provided a good simulation of both desaturation kinetic s and gas consumption using a range of cake thicknesses and pressure d ifferences, The equilibrium dewatering parameters (pore size distribut ion index, breakthrough pressure and equilibrium saturation) that are required to run the model had to be determined by experiment, since th e formulas available for calculation of these parameters provided erro neous results, Although the model is only strictly applicable to incom pressible cakes, it coped well with the slight compressibility of typi cal (-0.5+/-0 mm) coal filter cakes. However, this compressibility mig ht explain why the model was least accurate with thin cakes or at high vacuum levels, Further development of the model will be undertaken pr ior to applying it on commercial-scale filters.