Kinetics of wet versus dry grinding of lignite by a porcelain mill

Abstract

The kinetics of dry versus wet grinding of several feed size fractions of lignite in a laboratory size porcelain mill are reported here using feed fractions prepared to 600+425, -425+300 and -300+212 mum mono-sizes. The kinetics process is first-order up to 8 min for dry grinding while it is first-order up to 16 min for wet grinding. However, the specific rates of breakages decrease as feed sizes decrease for both dry and wet grinding. Rates of breakage (S-i) of wet grinding are found to be consistently higher than those of the dry values. The dry B-ij rates are also gamma=1.58, phi=0.58 and beta=7.11, 8 the wet values obtained to be gamma=1.45, phi=0.63 and beta=6.45. The breakage parameters, therefore, indicate that wet grinding in a porcelain ball mill is more efficient to get finer product sizes. The simulated product size distributions of both dry and wet grinding are in good agreement with the experimental product size distributions using a standard ball mill simulation program.