GB787292A - Process and apparatus for heat-treating fluidized solids - Google Patents

Abstract

Finely divided solids are heated in a process wherein a part of said solids is passed successively through at least three fluidized beds comprising a preheating zone, a heating zone and a final treatment zone, and the remaining portion <PICT:0787292/III/1> is passed directly from the preheating to the final zone: the heat supplied in the heating zone is greater than that required by the solid in the final zone which has passed thereto from the heating zone. The process is described with reference to the treatment of haematite to form magnetite by reduction in the final stage. A gas at 1100 DEG C. comprising H2, CO, CH4 and diluents was passed into the reduction stage which had a temperature of 650 DEG C. whilst the heating zone was at 800 DEG C. and the preheating zone at 220 DEG C.; 54.3 per cent of the solids bypassed the heating stage. In the illustrated embodiment, the preheating zone A is divided into two portions 30 and 31 by means of a partition 26, each of which is separately supplied with ore. The ore is fluidized and preheated by the gases rising through grid 21 from the heating zone B and the ore in bed 30 is passed into the heating zone. An inlet pipe 60 supplies air to the heating zone directly or through the upper part of chamber 45, whereby the combustible reducing gas passing through the final zone C is burnt in said bed 40. The solids in bed 40 are passed into the reducing bed 45 together with cooler solid directly from the preheating zone, and there mix. The proportions of ore entering the reducing zone from the preheating and heating zones are arranged to give a suitable temperature for reduction, and the partition may be so placed that the cross-sectional areas of beds 30 and 31 correspond to these proportions; the depths of these beds may then be maintained substantially equal.