| 摘要 |
<p><PICT:0361903/III/1> Materials containing iron in combination with sulphur are treated in a finely divided condition with dilute chlorinating gases to form ferrous chloride, liberated sulphur is removed as vapour substantially free from heavy metal chlorides, the ferrous chloride formed is oxidized with preheated air with formation of ferric chloride diluted with nitrogen which is returned to the chlorination step, and the chlorinating and oxidizing reactions are carried out at such temperatures that no bulk fusion of the solids present takes place. The material to be chlorinated may be supplied in a finely divided state, or be brought into such state during the treatment, for instance by effecting the reaction in a drum loosely filled with pebbles or balls, such as that described in Specification 348,651; preferably also the material is moved countercurrent to the heated chlorinating gases. The chlorinating and oxidizing reactions may be carried out in separate kilns, or as shown in Fig. 1, ore preheated to 300-350 DEG C. may be fed in at X to a single kiln and dry air and chlorine, preheated say to 300-350 DEG C. be supplied at Y. After passing a preheating zone A, the ore is chlorinated by residual chlorine (sulphur chloride) in the zone B1, and by ferric chloride coming from zone C in zone B2. Sulphur free from heavy metal chlorides, but containing possibly arsenic, antimony, and bismuth chlorides, and nitrogen from the air, exits at X. In zone C ferrous chloride formed in zone B2 is oxidized by the air in the gases to ferric chloride and oxide, the former passing to zone B2 and the latter being discharged with gangue and unaltered chlorides such as those of copper, nickel, zinc, and lead at Y. Manganese if present is discharged as oxide. The kiln is jacketed to ensure uniform temperatures, and with preheated ore and gases external heating is unnecessary. The permissible temperatures are such that no ferric chloride appears in the gangue, and no substantial amount of ferrous chloride is included in fused chlorides of other metals present. In zone C a temperature of 280 DEG C. is necessary to volatilize all ferric chloride, and in zones B2, B1 ferric chloride and sulphur must remain in the vapour state. Make-up chlorine may be introduced as chlorine, sulphur chloride, or ferric chloride, but when copper, nickel, or cobalt are present, the presence of free chlorine in the oxidizing zone is advantageous as it protects their chlorides from oxidation. When a separate kiln is used for the oxidation step, chlorine is mixed with the heated air for oxidation, and the ferric chloride vapours together with make-up chlorine, if necessary, are passed into the chlorinating kiln. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following subject-matter:--the air for oxidation is not necessarily preheated, nor is the sulphide material necessarily finely ground. This subject-matter does not appear in the Specification as accepted.</p> |
