GB1364150A - Pellets and their production - Google Patents

Abstract

1364150 Ore pellets; silicon carbide F O WIENERT 26 Sept 1972 44418/72 Heading C1A [Also in Divisions B5 and C5] Rounded pellets, especially of carbon-reducible iron ores or of carbon, are formed from a mixture of particles and an aqueous liquid by vibrating the mixture whilst rolling it into a dense uniform layer, dividing this mass into equal pellet-sized bodies, rounding the bodies into pellets and drying them. The amount of liquid present in the mixture should exceed that held by the densely packed particles, the amount of the excess depending upon the particulate material. The mixture may be fed to a conveyer 13, having side plates (not shown), whereon it is doctored by a roll 21, and compacted by a pair of rolls 27 carrying a vibrator 31. The compacted layer is sliced into strips by slitting knives 33, the strips being cut transversely into cubes by a flying cutter 35. The cubes fall on to a sloping oscillating table 39 where they are rounded. This table may additionally be vibrated and provided over its surface with rounded protuberances. Other tumbling means such as a rotary drum may replace the oscillating table. Drying may be effected by hot gas, or by coating the pellets with powder which may remain thereon to form a shell either of the same or a different composition. In an alternative arrangement (Fig. 2, not shown) the compacting vibrator is below the conveyer and the two cutters are replaced by an endless belt mechanism comprising hinged sections of width equal to that of the compacted layer and each comprising a grid which is brought down on to the compacted layer to penetrate it, assisted by a vibrator, the cut out pieces then being discharged on to the shaking table as before, a further vibrator being used to assist in dislodging them from the grid. After partial drying the pellets may be impregnated, or the coating thereon impregnated with binder in a liquid, e.g. water and then completely dried. Examples 1 to 5 describe in detail the use of the method for producing pellets of various iron ores, the green pellets being dried and hardened by hot oxidizing gases. A small quantity of bentonite may be added and the ore-bentonite powder may be used to coat the pellets during tumbling. Bituminous coal may be used with coarse titaniferous magnetite ore, the proportions being such that upon heating the pellets in a kiln most of the oxide is reduced to metallic iron and sufficient carbon is left to reduce and combine with the titanium when the pellets are subsequently smelted. The dried pellets were cooled in an inert atmosphere. Partially pre-reduced iron oxides may be used and blast furnace dust, other waste ferrous material, and coke breeze may be included (Examples 6-7). Iron-oxide with carbon pellets may have limestone particles added to improve desulphurization during smelting (Example 11). Other oxides may be pelletized by the method, Example 12 describing pellets formed from silica, coal, pitch and tar.