GB1263419A - A method and apparatus for controlling the roasting temperature of ore - Google Patents

Abstract

1,263,419. Multiple hearth furnaces; controlling hearth temperatures. AMERICAN METAL CLIMAX Inc. 4 Aug., 1970 [22 Sept., 1969], No. 37614/70. Heading F4B. [Also in Division C1] The oxidation roasting of sulphide ore concentrates e.g. iron sulphide, copper sulphide, zinc sulphide, nickel sulphide or molybdenum sulphide in a multiple hearth furnace is controlled by supplying to individual hearths a spray mixture of water and air under pressure, temperature measurement in each of said hearths being utilized to vary either the air pressure or the water pressure to restore a desired temperature in said hearth. Either of two control systems may be used, one (Embodiment A, Fig. 7) in which the spray cooling control system uses a variable air pressure and a constant water pressure, and the other (Embodiment B, Fig. 8) in which a constant air pressure and a variable water pressure is used. With the first system if the hearth temperature rises unduly the air pressure and therefore the air flow is decreased, reducing the heat developed, and consequential increased water flow increases the amount of heat dissipated. With the second system an increased hearth temperature results in an increased water pressure, an increased flow of water to the hearth and therefore a lowering of the temperature. With both systems as the hearth temperature falls below the desired temperature, the reverse action occurs. Using a twelve hearth furnace, Fig. 1, and numbering the hearths from the top downwardly it is usually sufficient to control hearths 2-7 or 2-8. The furnace 10, Fig. 1, comprises a refractory shell 11 with hearths 13 apertured centrally for a hollow rotary shaft 14 driven by a motor 18 through bevel gears 16 and 17 and supplied with air at 20 for distribution through rabble arms 21 over the hearths. Material (e.g. MoS 2 ) fed in at the top is discharged from alternate hearths 13 at the centre of the periphery by the rabble arms, said material leaving at 22. SO 2 is discharged with waste gases through a flue 23. As shown in Fig. 6 three pressure nozzles 27A, 27B and 27C are disposed symmetrically around the periphery of a hearth 13D and supplied with water and air through pipes 28 and 29. Rakes 31 on the rabble arms 21 are angled to feed the ore to the inside or the periphery of alternate hearths and work doors 30 are provided in the wall 11.