| abstract |
The process separates sludge from other substances such as earth, building refuse, waste materials, and containing chemical compounds which are insoluble or poorly soluble in water. Such substances include zinc sulfide, zinc oxide, lead sulfide, lead oxide, cadmium sulfide, cadmium oxide and arsenic oxide. The solids contained within the sludge are washed in a contra-flow and dissolved compounds precipitated from the solution. A coarse-grained fraction is separated from the washed solids, and has a grain size greater than 5 mm, preferably 10 mm, in diameter is separated. The residual fraction is then partially drained of water and subjected to wet milling, from which a fine fraction is removed together with overflow fluid from the washing process, and having a particle size of less than 10 micro m, but preferably less than 5 micro m. |