Cleaning limestone by high-pressure water jetting

The removal of clay constituents from crushed limestone continues to be a major problem in the lime industry. Conventional washing methods using washing drums, log washers or underwater vibrating screens are expensive and of only limited effectiveness. These methods can now be replaced by very efficient high-pressure water jetting. In high-pressure water jetting the raw crushed rock is exposed to a jet of water from solid- or flat-jet nozzles on an existing vibrating screen. Pressures of 7 to 20 bar or even higher in difficult cases, are needed depending on the toughness of the clay impurities. Several lime works and a gravel works are now using this method successfully High-pressure water jetting can be substantially intensified if the entire processing sequence, in particular the process stages of primary crushing and passage through the silos, are included for deformation, soaking and softening the clay impurities. A report is given of examples of applications and the experience gained so far.