GB643282A - Improvements in or relating to methods and apparatus for reactivating bone-char - Google Patents

Abstract

Bone char used in decolorizing sugar is reactivated by slowly passing it successively through drying, heating and burning zones in a multiple hearth furnace fitted with rabbling means, withdrawing gases from a point preceding the burning zone in the direction of flow of the char, and reintroducing the withdrawn gas together with hot fuel combustion gases including a small amount of superheated steam and <PICT:0643282/III/1> a limited quantity of oxygen such that a coating of activated carbon remains on the char particles in the burning zone. Hot gaseous combustion products from combustion chamber 41 enter the furnace through openings 42, 43, at a temperature about 1100 DEG C. and are in part withdrawn through pipes 33, 34, filtered and recirculated to the combustion chamber. Air enters the furnace through the base 27 of the central hollow rotating shaft 19, fitted with rabble arms 22, and the combustion products which have not been recirculated are withdrawn from the top of the shaft at 28 and through pipe 30. The reactivated char is removed from the base of the furnace and cooled by known means.