Novel Characterisation of Coal Petrography for Improving the Dewatering of Fine Coals Using Chemicals

This project aimed to develop alternatives to existing mechanical dewatering technology, improve water quality and usage, and encourage further projects in these dewatering areas.  Typically, concentrates of coal flotation are dewatered to provide fine coal products of approximately 20 wt% moisture. The desired dewatering of ultrafine (-0.045 mm) coal products is difficult (and expensive). The desliming of this ultrafine fraction of the flotation feed is not often feasible because of the loss of high-quality fine coals to tailings which can cause considerable environmental concerns. Improving the dewatering of fine coals not only increases the value of coal products and maximizes the efficiency of fine solids capture but also reduces water consumption and increases water recycling.

In this project, the novel coal grain analysis by optical petrography developed in C16039 and the novel coal washability analysis by non-destructive XCT (X-ray computed tomography) technology developed in C21050 were applied and combined. The objectives of the project were successfully achieved:

• A diagnostic tool based on high-resolution three-dimensional imaging of coal using microfocus XCT to optimize fine coal dewatering was developed;
• XCT results for coal composition and density information were benchmarked and validated against the traditional optical petrographic method;
• Coal grain composition information was used to develop an understanding of the response to dewatering of different grain types and predict the process performance under vacuum conditions;
• Microfocus XCT as a reliable method for determining the composition characteristics of fine coals for optimizing fine coal dewatering using chemicals was demonstrated and validated.

The outcomes of this project show that use of XCT provides benefits to the coal industry, including a novel technique, which integrates CGA and XCT information, that improves the dewatering of fine coals by using chemicals which can be combined with vacuum to efficiently increases the dewatering rate and reduce the final moisture of fine coal products. Since microfocus XCT technology will be used, no mechanical breakage and processing of coal samples will be required, showing this new technique to be fast, non-destructive and cost-effective.