Coal Preparation » Environmental Improvement
The aim of this project was to test a broad range of samples of clay mineral-rich run-of-mine (ROM) and tailings materials from coal mines across the various coal basins that are currently mined on the east coast of Australia. The clay mineral-rich samples and, for comparison purposes, a number of commercially pure clay samples, were characterised to identify their mineralogical, geochemical, geotechnical and micro-structural parameters and then subjected to various dewatering processes and treatments in order to understand their dewatering performance.
The treatments applied included:
· Variation of water quality;
· Application of various inorganic coagulants;
· Application of an organic polyelectrolyte cationic coagulant and an anionic flocculant.
A synthesised standard water with a quality modelled on a typical mine process water was used as a benchmark for all samples and all dewatering processes. Various other water qualities were also tested including process water collected from the mines from which the samples were sourced.
The dewatering processes utilised were:
· Settling as would occur in a plant thickener;
· Secondary flocculation as is applied to pre-thickened tailings in preparation for their disposal or filtration by belt press or screw press filtration;
· Pressure filtration.
The results for each dewatering process and treatment were analysed to determine the existence of any correlations between clay types, their parameters and dewatering performance.
Numerous relationships were found that provide broad guidelines for the likely dewatering performance of a given ROM or tailings sample, based on its composition, particle size distribution, geochemical and geotechnical parameters, and its micro-structure.