Pneumatic flotation - an alternative to the conventional mechanical flotation machines?

In response to the increasing economic pressure on producers of coking coal in Germany, the Ruhrkohle Bergbau AG (RBAG) opted to undertake an extensive increase of their existing flotation capacity. Two new flotation units were built in 1996, with aim of reducing the ash content of the coking coal by 0.7% and therefore take advantage of the higher sales prices attainable for the improved product. The flotation units were designed according to different concepts. Whereas the operators of the Heinrich Robert mine decided to install a conventional floatation unit with a mechanical cell, at the Lohberg colliery, the existing floatation unit with Denver system cells was extended with a two-stage pneumatic flotation system. Since commissioning of the units in 1997, tests have been carried out at the both plants, primarily to optimize the performance of the units, but also to establish a reliable data set enabling comparison of the different flotation techniques. Tests were conducted on laboratory scale by the school of mines `Technische Fachhochschule Georg Agricola' in Bochum and on industrial scale at the processing plants by the RBAG and DMT Gesellschaft fuer Forschung und Pruefung mbH (DMT). Although the optimization work has not yet reached its conclusion, the results obtained so far clearly demonstrate the success of the new concepts.