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Depending on the base material, the attrition cleaning of contaminated mineral residues or other raw materials can be markedly improved by the systematic intensification of the attrition, classification and dosing processes in combination with an integrated dedicated measurement and control system. This ensures a constant solids concentration, which is essential for high efficiency. Tests have been carried out on quartz sand fractions contaminated with mineral oil and the results obtained are superior to those of conventional attrition processes. The system can be retrofitted and costs can be kept low due to the relatively simple process equipment required., Depending on the base material, the attrition cleaning of contaminated mineral residues or other raw materials can be markedly improved by the systematic intensification of the attrition, classification and dosing processes in combination with an integrated dedicated measurement and control system. This ensures a constant solids concentration, which is essential for high efficiency. Tests have been carried out on quartz sand fractions contaminated with mineral oil and the results obtained are superior to those of conventional attrition processes. The system can be retrofitted and costs can be kept low due to the relatively simple process equipment required.

Since July 1999, the bentonite slurry used to support the tunnel face and remove cuttings in hydroshield tunnelling has been regenerated in what is currently the world's largest separation plant. Problems are encountered with the dewatering of separated material in such plants, when a tunnel is being driven through extremely clayey soils so that the clay size distribution overlaps with that of bentonite. A plant concept centred on three stages of hydrocyclones has avoided the high cost of dewatering centrifuges and guaranteed compliance with the limits on bentonite in discharge to the Westerschelde river., Since July 1999, the bentonite slurry used to support the tunnel face and remove cuttings in hydroshield tunnelling has been regenerated in what is currently the world's largest separation plant. Problems are encountered with the dewatering of separated material in such plants, when a tunnel is being driven through extremely clayey soils so that the clay size distribution overlaps with that of bentonite. A plant concept centred on three stages of hydrocyclones has avoided the high cost of dewatering centrifuges and guaranteed compliance with the limits on bentonite in discharge to the Westerschelde river.

A new process for cleaning surface-contaminated mineral wastes has been developed by analogy with wet ultrafine grinding in stirred mills. The process can be used to clean contaminated soils, oil sand or sand-trap residues, even down to the fines range. Acceptable attrition of particles smaller than 200 micrometres can only be achieved with the addition of grinding media, which must be specifically adjusted to the feed material in terms of size, type and quantity: for materials smaller than 100 micrometres, steel beads with a diameter of 200-400 micrometres are best when supplied in a defined ratio to feed material. The use of grinding media also substantially improves cleaning of the surfaces of larger particles. In a series of tests on sands contaminated with mineral oil, cleaning efficiencies of over 80% were obtained while other techniques could not produce acceptable results., A new process for cleaning surface-contaminated mineral wastes has been developed by analogy with wet ultrafine grinding in stirred mills. The process can be used to clean contaminated soils, oil sand or sand-trap residues, even down to the fines range. Acceptable attrition of particles smaller than 200 micrometres can only be achieved with the addition of grinding media, which must be specifically adjusted to the feed material in terms of size, type and quantity: for materials smaller than 100 micrometres, steel beads with a diameter of 200-400 micrometres are best when supplied in a defined ratio to feed material. The use of grinding media also substantially improves cleaning of the surfaces of larger particles. In a series of tests on sands contaminated with mineral oil, cleaning efficiencies of over 80% were obtained while other techniques could not produce acceptable results.

During the wet mechanical remediation of contaminated soils, particles in the size range 63 micrometres to 2 mm undergo attrition by agitation in a high-solids suspension, to produce a clean coarse fraction and very fine-grained abraded contaminant. A new process has been developed with an integrated dedicated measurement and control system to ensure that the solids concentration during attrition remains constant at 45% (1 200 g/l for quartz), so that free mobility of the individual particles is largely restricted and adequate attrition assured. Part of the fraction greater than 0.5 mm is separated from the abraded material and recirculated back to the material feed, where it can be added whenever a torque sensor on the drive shaft motor determines that suspension consistency has fallen below the programmed set value. The technology has already demonstrated its efficiency at pilot-plant scale, in tests with different contaminated residues such as sand-trap wastes., During the wet mechanical remediation of contaminated soils, particles in the size range 63 micrometres to 2 mm undergo attrition by agitation in a high-solids suspension, to produce a clean coarse fraction and very fine-grained abraded contaminant. A new process has been developed with an integrated dedicated measurement and control system to ensure that the solids concentration during attrition remains constant at 45% (1 200 g/l for quartz), so that free mobility of the individual particles is largely restricted and adequate attrition assured. Part of the fraction greater than 0.5 mm is separated from the abraded material and recirculated back to the material feed, where it can be added whenever a torque sensor on the drive shaft motor determines that suspension consistency has fallen below the programmed set value. The technology has already demonstrated its efficiency at pilot-plant scale, in tests with different contaminated residues such as sand-trap wastes.