A PROCESS AND AN APPARATUS FOR OBTAINING SODIUM HYDROXIDE AND USEFUL PRODUCTS FROM A SODIUM CHLORIDE- CONTAINING WASTE MATERIAL

摘要

A process and an apparatus for obtaining caustic soda (87) and hydrochloric acid, preferably in solution (67), or another useful product containing chlorides (243'), such as an anti-icing solution (244'), from a sodium chloride-containing a waste material (12,17), typically a tannery waste material, wherein a step is provided of contact, at a predetermined temperature, comprising reactions of the sodium chloride of the saline solution (17), of an amount of a carbonaceous material (18'), of steam (49) and of preferably atmospheric oxygen, from which a gas mixture is obtained (62) that contains hydrogen chloride, preferably subjected to an absorption into water (73) to obtain an aqueous solution (67), and also sodium oxide is obtained stuck on the carbonaceous residue (18"). The step of contact may comprise alternate steps of supplying steam and air. A step is provided of washing the carbonaceous residue (18") preferably in a tubular conveyor apparatus (71) such as a screw conveyor in which water (72) is preferably countercurrently recycled until a caustic soda solution (72') is obtained at a predetermined concentration. The process makes it possible to obtain useful products from saline waste water such as the brine resulting from a preliminary washing of skins and from treatment of fleshings in tanning industry.