| 摘要 |
<PICT:1011594/C1/1> A self-fluxing pellet is produced by kilning a pellet comprising a core of iron ore and flux material, e.g. compounds of Ca or Mg, surrounded by a flux-free iron ore coating. In Fig. 6, a mixture of flux (32%) and iron ore (68%) in hopper 1, ground to - 14 U.S. mesh, is funnelled on to conveyer 2 and delivered to drum 3 where it is sprayed with water and forms into balls which roll down the rotating drum. Screening device 5 delivers cores of diameter 3/8 inch, via conveyer 6, to drum 10. Iron ore from 11, and water, are introduced along the length of the drum and the resulting ore-coated pellets are screened at 17 to deliver pellets of diameter 1/2 -inch to furnace 20. A gas permeable conveyer 21 carries pellets through drying zone 24 (at 500 DEG F.), burning zone 25 (at 2200-2400 DEG F.) and cooling zone 26. Cool air from wind-box 31 passes up through 26 to conduit 35. This preheated air supports combustion of fuel introduced into 25 through nozzle 40 and also flows through conduit 37 to zone 24. These gases are drawn into suction box 30 and exhausted at 42. In a preferred embodiment, furnace 20 is replaced by furnace 70, illustrated in Fig. 7. Hood structure 72 and baffles 73 define three zones: 74 for preliminary drying, 75 for final drying at 500-900 DEG F., and 76 for preburning at 1600-1800 DEG F., while rotary kiln 77 defines final burning zone 78, at 2200-2400 DEG F. Pellets are carried on conveyer 81 at such a rate that in 75 water vapour escapes through, but does not crack, their coating, and in 76 any magnetite in the ore is converted to haematite and bridging of grains of haematite is initiated in the coating. Pellets are then tumbled in 78, where a continuous network of haematite is produced and the coating is densified and confines any liquid slag formed; and are finally cooled in an upward-flowing air stream in 83. This preheated air enters firing hood 86 of kiln 77 having burner 90, and hot gases proceed through 78, downward through 76 to suction box 91 and conduit 92, downward through 75 to conduit 94 and wind-box 95, upwards through 74, and are exhausted at 96. Ca and Mg ferrites are shown to be present in the core. Specification 835,981 is referred to. |
