Patent GB-374070-A (GB)
Title: Improvements in the chlorination of material containing iron sulphide
IPC: C22B1/08
Filed: 1931-02-25
Abstract: In the recovery of sulphur from ores &c. containing sulphides of iron and other metals such as nickel and copper, sulphur chloride is passed over the material into a zone of increasing temperature to produce sulphur and nickel, copper and ferrous chlorides from which the chlorine is recovered and returned to the process.  Ore is fed in a finely divided condition into one end of a rotary reaction chamber and sulphur chloride, alone or mixed with inert gases, is passed from the other end in counter-current, a temperature of from 450-550 DEG C., preferably 500 DEG  C., being maintained near the ore-charging end and 300-350 DEG  C. at the discharging end.  The vaporized sulphur is collected and condensed and the mixture of chlorides heated with air to form ferric, nickel, and copper oxides together with chlorine and ferric chloride which is condensed.  Nickel and copper are separated from the iron oxide by treatment with hydrogen chloride which acts selectively forming nickel and copper chlorides, these being separated from the iron oxide by water.  Complete removal of the iron from the chloride residue may be effected by treatment with chlorine instead of air to produce and vaporize ferric chloride which is hydrolised by superheated steam at 300-400 DEG  C. forming ferric oxide and hydrogen chloride.  The hydrogen chloride is dried by sulphuric acid and treated with air at 420-530 DEG  C. in presence of a catalyst, such as ferric or other oxide, carried by packing material, e.g. pumice, the catalyst being kept at a temperature of 370-400 DEG  C. or up to 470 DEG  C.  The reaction is not complete and the gases are dried, passed through a second catalytic chamber, washed with water to remove hydrogen chloride and dried.  Sulphur chloride is regenerated by passing the chlorine formed through molten sulphur maintained at a temperature above the boiling-point of sulphur chloride, e.g. 150 DEG  C.  The sulphuric acid used for drying is mixed with the water used for removing the hydrogen chloride and concentrated, the first part of the steam given off being used for treating the ferric chloride.  The chlorination of the sulphide ore may be so conducted that ferrous chloride is separated from the other chlorides by regulating the temperature so that it gradually increases from normal at the charging end to 550 DEG  C. at a midway point and decreases to about 350 DEG  C. at the discharge end, a gas outlet being provided where the temperature is about 450 DEG  C. Sulphur chloride is introduced at the discharge end and moves in countercurrent to the ore.  Ferrous nickel and copper chlorides are first formed, and as the charge moves along the reaction chamber, the ferrous chloride is converted to ferric which is vaporized and reduced by fresh ore to ferrous chloride, a separation thus being effected.  The operation may be conducted as a batch operation or as a continuous one.  The ferrous chloride concentrate may be treated with air to produce chlorine or with air and steam to produce hydrogen chloride.  Specifications 306,107, 306,691, [both in Class 1 (iii), Oxides &c., Metallic], and 374,071 are referred to.  The Specification as open to inspection under Sect. 91 (3) (a) states also that when a mixture of sulphur chloride and inert gases is used for treating the sulphide material, a temperature of 300-350 DEG  C. may be maintained throughout the reaction chamber. This subject-matter does not appear in the Specification as accepted.