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Roland Dreesen, VITO (Belgium)
Peter Nielsen , VITO (Belgium)
Ben Laenen, VITO (Belgium)
Johan Matthijs, VITO (Belgium)
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Coal waste dump rocks are the sterile residual material stored at the surface (coal mining tips) resulting from both coal mining and from the subsequent surface treatment of the mined material (washing of the bulk coal). The stony coal waste material consists dominantly of argillaceous rock types (70%), sand- or siltstones (20%) and coal (10% including carbonaceous shale). After crushing and homogenisation this material can be used in the ceramic industry as an important additive in the production of bricks. The bulk mineralogical composition of the coal waste dump rocks consists chiefly of kaolinite, illite and quartz with minor carbonates and feldspar. Consequently, important savings on raw materials can be obtained besides a modest reduction of the fuel costs due to the presence of residual coal. Moreover, the mixing of basic clay raw materials with coal waste dump rocks that have a sulphur content of less than 1 %, has a positive environmental impact, especially with respect to the atmospheric SOX and HF-emissions. European, national or regional legislations favour the idea of coal waste dump materials being considered as secondary raw materials instead of waste products. However, a major constraint to their exploitation or reclamation in Flanders is the desired or wished for destination, i.e. nature reserve, greenbelt, recreational, residential or industrial area.
In order to assess the actual available volumes, different methodologies have been applied. Firstly, all available coal mining maps have been GIS-processed, allowing a detailed calculation of the total volume of the extracted rock material. Stone drifts, blind shafts and all underground working panels have been digitized, taken into account the information about coal seam composition for each mined panel. Based on the coal/sterile rock ratio, the residual coal content of the coal waste dumps (3% by volume) and the average rock densities, a bulk volume has been calculated for the extracted material. Secondly, a calculation of the actual volumes of the dumps (after remodelling and reclamation) has been carried out by using the digital height model of Flanders. Volume to reserve calculations were based on average densities of coal waste dump material from adjacent coal fields. The differences between the results of the two methodologies are related to the fact that important volumes of coal waste have been used for levelling purposes and for backfilling the mined panels. The calculated volume of the actual residual coal waste material in the former Campine coal fields amounts to about 240 million tons, 90 million tons of which are still available as secondary raw material, taken into account the actual or planned destinations with respect to land use.
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