DE1937392

1308639 Extracts VEREINIGTE ALUMINIUM-WERKE AG 10 July 1970 [23 July 1969] 33738/70 Heading B1Q [Also in Divisions C1 and D2] A process for the acid, alkaline or neutral wet treatment of solids which contain constituents extractable on wet treatment, except the extraction of bauxite with sodium aluminates, comprises passing a suspension of the solid in a reagent capable of extracting the required constituent through a digester tube of constant cross-section at a velocity of at least 0.5 metres per second at a volumetric through put rate of from 0.01 to 0.5 cubic metres per metric ton of solid to be treated per day and heating the suspension during its passage through the tube to a temperature at which digestion occurs. The Examples describe the extraction of Hemite (FeTiO 2 ) with sulphuric acid, Scheelites (CaWO 4 ) with soda solution, the extraction of chromium ores with caustic soda, the extraction of cellulose from peeled and ground wood using sodium liquor or a mixture of caustic soda, sodium sulphite, sodium carbonate and sodium sulphate and the extraction of sulphite cellulose from ground wood using potassium bisulphite liquor.