GB469512A - Method and apparatus for the roasting of mineral sulphides - Google Patents

Abstract

<PICT:0469512/III/1> In the roasting of sulphide ores in suspension, the heat necessary for the roasting being provided wholly or in part by the combustion of the sulphur content of the ore, preliminary drying of the latter is effected, by heat derived from the combustion stage, in a plurality of steps, the moisture-laden gases from the respective steps being either returned to the combustion chamber for attemperating purposes or evacuated to the atmosphere according to the thermal value and the moisture content of the charge. As shown, a combustion chamber 8, into which finely divided dried ore and an oxidizing gas, such as oxygenated air, are introduced through a nozzle 20, is surmounted by superposed drying hearths 2, 5, the former being enclosed by a sealing cover 70 which is fitted with a feed shoot 69 having a pivoted self-charging valve 75. The lower drying chamber receives hot gases direct from the combustion chamber 8 through the space 6 around the central rabble shaft 4 while a conduit 32, fitted with a valve 21 is provided for the supply of an adjustable quantity of hot gases to the upper drying chamber 72. The ore passes from the hearth 2 to the hearth 5 through drop-holes 3 and when fully dried, is delivered to a grinding-mill 17 from which it is raised by an elevator 18 to the hopper 19 supplying the nozzle 20. The gases leaving the upper and lower drying chambers are either evacuated to atmosphere by way of valve controlled pipes 37, 35, 33 and a dust separator 28 or returned to the combustion chamber to lower the temperature therein through pipes 37, 35 and nozzle 20. The upper drying chamber is also provided with a valve-controlled outlet 52 leading directly to the atmosphere. Below the combustion chamber 8 are arranged receiving hearths 9, 11, 77 which provide a chamber discharging through a valve-controlled shoot 13 to a bin 15 and a lower chamber 39 in which the roasted particles received from the upper chamber may be sulphated before being delivered by a screw-conveyer 78 to a bin 14. The main body of the combustion gases passes off from the chamber between the hearths 9, 11 through a conduit 27 fitted with a two-way valve 26 by which all or a part of the gases may be diverted from a conduit 12 leading to a waste-heat boiler 76 to a heat-exchanger 46 through which the oxidizing gas for the nozzle 20 is forced by a fan 47. The gases leaving the boiler 76 may be passed to atmosphere through the dust separator 28 or returned to the combustion chamber for attemperating purposes through pipe 33 and nozzle 20.