Patent GB-433861-A (GB)
Title: Improvements in methods for the removal of lead and/or cadmium from zinciferous materials
IPC: C22B19/02
Filed: 1934-01-22
Abstract: A process for removing lead and cadmium from zinc sulphide ores, concentrates, &c., comprises a blast-roasting operation in which the ore &c. is mixed with a granular or nodular material in such quantity as to ensure a high porosity in the charge and a lead content thereof of below 1,5 per cent, and in which the draught through the charge bed and the fuel value of the charge are adjusted to give a temperature, e.g. 1300 DEG  C., above that required to eliminate sulphur without the lead content in the exit gases exceeding 280 m. grms. per cubic foot N.T.P.  The fuel value of the charge may be increased by lowering the proportion of nodular material to raise the sulphur content above 7 per cent when the lead content is not too high, or otherwise by adding coal or coke, and the draught may be increased to 40 cubic feet N.T.P. or over per sq. ft. of grate area. The nodular material may consist of graded deleaded returns of particle size greater than \ba1/8\be to \ba1/16\be of an inch.  To maintain the bottom of the charge at a sufficiently high temperature, a layer of coke breeze may be provided on the grate below the charge. Residual lead in the sintered product may be removed by crushing and tabling or by floation separation.  Lead and cadmium may be removed from desulphurized zinciferous material by a similarly-conducted blast-roasting operation, fuel being supplied by carbon in the form of coal, coke, or oil.  When the sintered product is distilled for the production of zinc, the small amount of residual lead is recovered during the first portion of the distillation period together with any remaining cadmium.  Specification 306,569, [Class 82 (i)], is referred to.ALSO:A process for removing lead and cadmium from zinc sulphide ores, concentrates, &c., comprises a blast-roasting operation in which the ore &c. is mixed with a granular or nodular material in such quantity as to ensure a high porosity in the charge and a lead content thereof of below 1,5 per cent, and in which the draught through the charge bed and the fuel value of the charge are adjusted to give a temperature, e.g. 1300 DEG C., above that required to eliminate sulphur without the lead content in the exit gases exceeding 280 m. grms. per cubic foot N.T.P.  The fuel value of the charge may be increased by lowering the proportion of nodular material to raise the sulphur content above 7 per cent when the lead content is not too high, or otherwise by adding coal or coke, and the draught may be increased to 40 cubic feet or over per sq. ft. of grate area.  The nodular material may consist of graded deleaded returns of particle size greater than 1/8 to 1/16 of an inch.  To maintain the bottom of the charge at a sufficiently high temperature, a layer of coke breeze may be provided on the grate below the charge.  Residual lead in the sintered product may be removed by crushing and tabling or by flotation separation.  Lead and cadmium may be removed from desulphurized zinciferous material by a similarly conducted blast-roasting operation, fuel being supplied by carbon in the form of coal, coke, or oil.  When the sintered product is distilled for the production of zinc, the small amount of residual lead is recovered during the first portion of the distillation period together with any remaining cadmium.  Specification 306,569, [Class 82 (i)], is referred to.