Patent GB-374069-A (GB)
Title: Improvements in the chlorination of iron sulphide containing material
IPC: C22B1/08
Filed: 1931-02-25
Abstract: In the recovery of sulphur from iron sulphide materials, sulphuryl chloride is used as the chlorinating agent under conditions such that ferrous chloride, sulphur and sulphur dioxide are produced, chlorine being recovered from the ferrous chloride and used to reform the sulphuryl chloride.  The sulphide ore &c. contains nickel and copper sulphide in addition to iron and is fed into a rotary reaction chamber, the sulphuryl chloride is introduced in liquid or gaseous form at the opposite end and the gaseous reaction products, containing sulphur dioxide and sulphur vapours, are removed at a point near the charging end.  A temperature of 500-550 DEG  C. is maintained near the charging end and 250-350 DEG  C. near the discharge end.  The sulphur is condensed from the effluent gases and the sulphur dioxide therein is combined with chlorine, recovered from the ferrous chloride produced, in the presence of a catalyst, e.g. camphor or active carbon, to reproduce the sulphuryl chloride.  The catalyst may be saturated with sulphur dioxide prior to the reaction and the temperature employed may be above or below the boiling-point of sulphuryl chloride.  The hot residue leaving the reaction chamber is first treated, at a temperature of 300-350 DEG  C. with chlorine in countercurrent in a rotary reaction chamber to produce and vaporize ferric chloride, leaving nickel and copper chlorides in the residue.  The chlorine employed may be mixed with inert gases serving to carry away the ferric chloride which, after condensation, is hydrolised with superheated steam to produce ferric oxide, hydrogen chloride, and water vapour.  The gaseous products are dried by sulphuric acid and the dry hydrogen chloride, preheated to 530 DEG C., is passed with air at the same temperature over a catalyst, e.g. nickel or copper chloride or sulphate distributed on inert carriers. The catalyst may be applied directly to the carrier or formed therein by the action, for example, of the hydrogen chloride on copper oxide distributed throughout the mass.  The towers carrying the catalyst may be arranged in series so that the catalyst may be renewed when necessary; temperatures between 205 and 470 DEG  C. may be used.  The reaction gases contain chlorine, hydrogen chloride, and water vapour to complete the reaction, these may be dried and passed over fresh catalyst, after which they are washed with water to separate hydrogen chloride, dried with sulphuric acid and used for the formation of sulphuryl chloride and the treatment of the ferrous chloride.  The wash water is mixed with the sulphuric acid which has been used for drying the hydrogen chloride, heated to drive off this gas and concentrated for re-use; the steam formed may be used for treating the ferric chloride.  Inert gases with the chlorine, are eliminated during the condensation of the ferric and sulphuryl chlorides. Alternatively, hydrogen chloride is produced together with the metallic oxides from the ferrous chloride with or without the other chlorides by treatment with air and steam at 400-600 DEG  C., preferably 500 DEG  C., in a rotary reaction chamber containing porcelain balls &c. to prevent adhesion of the chloride to the container.  Direct recovery of chlorine from the ferrous chloride may be effected by heating with air at 700-800 DEG  C.  In a modification, the process may be so operated as to deliver from the reaction chamber the ferrous chloride separately from the other chlorides, the temperature being regulated so that it increases gradually from normal at the charging end to about 550 DEG  C. at a midway point and decreases to about 300 DEG  C. at the discharging end, a gas outlet being situated between the charging end and the zone of maximum temperature.  No sulphuryl chloride is introduced until the ore reaches the zone of maximum temperature, the ferrous chloride first formed being converted as it nears the discharge end into ferric chloride which is vaporized and is reduced by fresh sulphide ore to ferrous chloride; the process is so controlled that iron compounds are eliminated from the material situated at the discharge end.  The ore may be fed in one batch or continuously during the chlorination. Specifications 374,070 and 374,071 are referred to.