Coal Preparation » Dewatering
Conventional dry processing methods engage a single beneficiation device (e.g. FGX, Air Jigs) employing air (and vibration) in place of water or medium, as is typical in wet coal preparation. More contemporary dry sorting methods employ advanced electromagnetic sensors coupled with analysers, fast processors and air jets. The air based methods are suited to higher throughputs but display low efficiencies. The electromagnetic sensing and sorting technologies display good and improving efficiencies but are constrained by low throughput. By combining these two technologies in a manner best suited to their respective strengths, higher throughputs and improved metallurgical efficiencies may be achieved. Dry sorting technologies are valued where water is scarce, wet processing impacts thermal coal CV(gar) or when there are cold climate considerations in play. It has the potential to partially beneficiate coal in-pit, thus reducing haulage costs. Dry sorting processes can also offer a low cost processing option for suitable coal types, enabling some junior and mid-tier miners to begin operations by means of a lower capital hurdle. The work undertaken in this project could potentially increase the longevity of existing operations or lead to the opening of additional resources and facilitate new projects which would otherwise remain undeveloped.
Dry separation is utilised for a number of applications. Current applications include use in arid areas where processing of coal reserves are restrained due to low water availability; low value coal product inhibits processing costs, logistic constraints or ex-plant product moisture impacts; removal of high-density material from thin seam mining operations and for coal beneficiation. Dry beneficiation devices are primarily used in China and North America, with installations in South Africa, Indonesia, Vietnam, and Mongolia. Worldwide, it is estimated that there are over 1500 FGX-units in operation (World Coal, 2013). This project looks at two dry beneficiation devices, the FGX and the X-ray Sorter (XRS). The FGX is one of the most prevalent technologies in this space, whilst the X-ray sorter is gaining significant traction across a number of mineral types with a fast-evolving capability. This project looks at both devices both individually and in series as ways to improve conventional dry processing.
The test work has demonstrated both devices provide a beneficiation when dry conditions need to be considered. Whilst the FGX provided the increased throughput capacity, the XRS configured in a second stage application enabled optimisation of product ash and yield. The combined efficiency of the two machines delivered an outcome that ensured minimal misplacement of coal to reject.
Further optimisation suggests these combined technologies provide an option to optimise resource recovery when wet processes are not an option. For operations that currently use or plan to use wet processes, these dry technologies can increase the percentage of ROM that currently qualifies as bypass coal or, to be more precise, coal that is not washed via conventional wet processes. This can be particularly beneficial for thermal operations given that the CV is of paramount importance. Existing bypass coals can be partially dry cleaned for higher sales price or to extend the degree of downstream blending that can be employed.