GB652098A - Process and apparatus for heat-treating solids - Google Patents

Abstract

<PICT:0652098/III/1> <PICT:0652098/III/2> <PICT:0652098/III/3> <PICT:0652098/III/4> <PICT:0652098/III/5> The invention relates to a process of heat-treating small masses of consolidated mineral particles at a predetermined treating temperature between the boiling point of water and the fusion temperature of said particles. Ore to be treated is fed under gravity into similar heating chambers 1, 11 at 6, 61 respectively, Fig. 1, relatively cool treated ore being discharged, either intermittently or continuously, at the lower ends 8, 81 of the heating chambers. A treating gas, e.g. air, is blown through a conduit 21, valve 20 and conduit 19 into an annular chamber 17 surrounding the base of the chamber 1, thence, through annular louvre arches 15, into the bed of ore. This incoming gas cools the previously heated ore and is itself heated thereby in its passage up through the ore. From a space 30 above the ore bed the gas passes through a cross-over 5 where it is further heated by a burner 24 and hot gas and combustion products pass down through the bed of ore in the other chamber 11, thereby to heat it, and out through louvres 151, chamber 171, conduit 191, valve 20, and conduit 23 to the atmosphere. The valve 20 is periodically actuated to reverse the gas flow through the chamber 1, 11. The control of the valve 20 and the rate of removal of treated ore is dependent upon the low temperature in the lower part of the chambers 1, 11. Thermo-couples in the open spaces 30, 301 control the supply of fuel to the burners 24, 241. In a modification, Fig. 3, untreated material is fed through a single shoot at the top of the chamber 1 and treated material is discharged through shoots 45, 47 in a conical grate structure 43, treating gas being supplied beneath said grate. In another modification, Fig. 4, treating gas is supplied into a space 50 formed beneath an inwardly sloping lateral wall 51; a revolving plate 52 spaced beneath the discharge point 8 of the chamber permits of a continuous discharge of treated material. A bell and hopper type charging means may be used. A modified construction of cross-over, Fig. 6, includes a cylindrical chamber 70 into which fuel gas is introduced through burners 42 or 421. A further form of heating chamber, Fig. 7, has a grate 75 inclined at an angle equal to the angle of repose of the material being treated. Various features of the modifications may be combined or interchanged. The heating chambers may be broad and long relative to their depth. Fuel may be introduced, e.g. by previously described burners, into the open spaces 30, 301 above the beds of ore instead of into the cross-over 5. Several pairs of chambers suitably interconnected may be used together. One of the chambers may function purely as a thermal regenerator and contain a gas-traversable bed of heat-absorbing solids such as fireclay shapes. In addition to indurating, the above apparatus may be used thermally to decompose cabonates of iron, manganese, calcium and magnesium; to reduce Fe2O3 to Fe3O4 by treatment with a mildly reducing gas in which case some of the exhaust gas is re-cycled through the systems; to thermally treat clays, bauxite, phosphate rock, chrome ore, pyrites; to reduce Fe3O4 to FeO; to reduce FeO to metallic iron; to oxidize FeO to Fe3O4; to oxidize Fe3O4 to Fe2O3; to oxidize the sulphur in high-sulphur iron ore. U.S.A. Specification 307,667 is referred to.