| 摘要 |
<p>1320171 Rotary kilns USS ENGINEERS & CONSULTANTS Inc 2 July 1970 [2 July 1969] 32254/70 Heading F4B Apparatus for processing raw material in the form of pellets containing moisture comprises a rotary kiln receiving the pellets at the upper end and moving them towards the lower end where a burner 16a directs hot gases through the kiln, and drying means 38 at the upper end of the kiln using the hot gas to dry out the pellets and having means for admitting fresh air to reduce the temperature in the drying means, the rotary kiln having a preheating zone adjacent the drying means and a reaction zone at the lower end, means being provided between these two zones for reflecting heat back into the reaction zone so that sintering of the charge is effected with less fuel. Combustion gases are withdrawn from the kiln through backhouse 22, bustle pipe 44, drier 38 and exhaust conduit 48 by variable speed induced draught fan 28a. Tempering cooling air from pipe 46 may be drawn into the bustle pipe 44. The reaction zone temperature is automatically regulated by control of the fuel supply to burner 16a, the pressure in the kiln by adjustment of exhaust damper 46b in pipe 42 and the temperature of the combustion gases leaving the drier 38 by control of the fuel supply to an auxiliary burner 68 in the pipe 42, whilst the amount of tempering air drawn into the bustle pipe is controlled by adjusting damper 46a in pipe 46 to produce a constant gas mass flow through Venturi section 49 in exhaust conduit 48. The feed of material to the kiln, past material valve 72d is varied in accordance with the rate of rotation of the kiln. In another embodiment (Fig. 1, not shown) in place of a separate drier, the initial portion of the kiln forms a drying zone to which the raw material is directly charged from a weigh feeder, by a shot extending through the backhouse. Longitudinally extending partitions and baffle means (18a, 18b, 18c) in the drying zone, divide the material in this zone into four separate streams. An automatically dampered supply of tempering air from a shroud (24) surrounding the kiln at the downstream end of the drying zone is drawn into the kiln at this point to limit the drying zone temperature to 700‹ F. A restricted diameter particle reservoir forming portion (26) between the preheating and reaction zones effectively limits the material layer thickness in the latter zone to ensure complete reaction of the raw material. A rotary cooler (30) for the sintered product is provided. In a further modification (Fig. 4, not shown) the restricted diameter portion extends over the whole length of the preheating zone. Dimensions of, and material residence times in the various kiln portions are given.</p> |
