Some 150 years of intensive coal mining in South Africa has produced about a billion tonnes of discarded thermal-grade coal fines. In the last decade, avenues of utilising this residual energy source are being explored with increasing commitment. Recognising both the economic potential and the environmental risk posed by the discards, Birkenmayer South Africa which produces mixing and granulation equipment says it is capable of processing the fines into usable coal-based commodities.
For the past one-and-a-half centuries, South Africa’s coal mining economy dictated that there was minimal value in the coal fines produced as a waste by-product. However, the increased cost of coal extraction due to rising energy prices; increased environmental concerns regarding the release of CO2, and diminishing vacant land for mine waste deposits, has led to a major shift in the approach to utilising this discarded energy in South Africa.
The historic discarding of coal fines is not due to its lack of thermal potential, but its intrinsically difficult handling and transport characteristics. The many heaps and slurry ponds that have emerged because of this, however, pose serious explosion and self-ignition risks during handling and are a major safety hazard.
There are three market streams for the fines market
- Briquetting and extrusion:
Fines can be processed for briquetting and extrusion purposes. This is a high value coal market, typically aimed at European and North American export to retail markets. The relatively large size (typically 40-60 mm) and shape of the intended end-product, as well as the degree of handling and distance to be transported, means that a high-strength and waterproof bond is essential. This application thus requires a more advanced, expensive binding.
Pelletising has a wide applicability in industrial demands where a cheaper heat source than is offered by conventional electrical means is sought. Intrinsically, due to both a smaller size as well as a far rounder composition than briquette pillows, these 15-50 mm coal pellets are less prone to breakage, meaning a less expensive binding option needs to be utilised. Depending on intended use, environment and transported distance, the pellets can be homogenised with waterproofing characteristics.
Granulated fines, of 1 – 15 mm, are best suited for electric power stations, which have the capabilities required to burn low-grade coal. Because South Africa’s power generation remains almost exclusively coal-reliant, there is an insatiable demand for this grade. The granulation of this coal is optimised solely in accordance with the nature of its transport requirements – minimised handling and smaller size means that the consistency does not need excessive strength – requiring an inexpensive binding solution. The mixer can also granulate 2 – 5 mm granules without binder, using the coal’s inherent ash content – an Eirich proprietary process. This eliminates a large cost component to the processing of the fines, but is best suited for conditions of minimal handling (in short or automated distances between mixer and power station). Granulated fines produced within the Eirich Industrial Mixer do not require additional upstream processing equipment, dramatically saving on capital costs.