Dry processing versus dense medium processing for preparing thermal coal

Abstract

Dense medium processing is the beneficiation process most widely employed in South Africa. Based on the fact that South Africa (and its neighboring countries) is a water-scarce area, dry processing technologies are being evaluated for implementation in the region. In addition to not requiring water, the technique is less expensive than dense medium processing - both in terms of capital cost and operating cost. An added benefit when preparing coal for use in power stations is the lower moisture content of the final product. The separation efficiency of dry processes is, however, not nearly as good as that of dense medium and, as a result, it is difficult to effectively beneficiate coals with a high near-dense content. The product yield obtained from some raw coals is lower than expected and control of product quality is not always easy with dry processes. In the case of easy-to-clean coals, dry processing gives good results and becomes a very attractive proposition – especially when the added benefit of low environmental impact is taken into consideration. The main consideration when implementing dry processing, especially for long-term projects, is whether the low cost of the process will be outweighed by the low recovery efficiency. This paper gives an overview of the performance as well as the economic advantages and disadvantages of dry processing technologies being evaluated in South Africa and compares it to dense medium.