Coal Preparation » Dewatering
Results of a bench scale, proof-of-concept study aimed at improving the handling, transport and marketability of coal fines are summarised and discussed. The concept involves integration of conventional filtration with size enlargement, by adding a binder to the filter feed slurry. Success would result in a lower moisture product with sufficient strength to maintain integrity in downstream handling/transport infrastructure. Moisture reduction without cake strengthening, or cake strengthening without moisture reduction are also worthwhile outcomes.
A wide range of binders were evaluated and screened and a short list of three preferred candidates, code named Binders X, Y and T, drawn up. Binder X (a styrene acrylate copolymer) produced outstandingly strong, water resistant cakes with no change in moisture. Binder Y (a heavy oil emulsion) substantially reduced moisture (from ca 22wt% to below 14wt%) although the cakes were weak, and Binder T (a bitumen emulsion) gave some improvement in both strength and moisture reduction although less than Binders X and Y.
Preliminary cost estimates suggest that the benefits from lower moisture should substantially exceed the costs of adding Binder Y. Furthermore, the cost of Binder X required to produce a filter cake from -0.125+0mm coal, strong enough to pass repeated cycling through a Durham Cone/Drop Shatter test procedure, is ca $6/tonne of coal treated and this could be lowered given further optimisation of binder dose.
It is concluded that there is merit in the concept of adding binders prior to dewatering. Further bench scale optimisation studies, broadening the test work to a range of coals and pilot scale trials using continuous filters are proposed.