GB467033A - Improvements in and relating to rotary kilns - Google Patents

Abstract

467,033. Automatic control systems. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 12, 1935, No. 34514. Convention date, Dec. 12, 1934. [Class 38 (iv)] [Also in Group XII] Temperature; fluid pressure.-A constantspeed rotary kiln has its fuel and air supplies automatically controlled in response to temperature in the kiln. The fuel supply means includes a hopper 24 for powdered fuel, a motor 26 feeding the fuel to a burner 23 at an adjustable rate and a motor driven compressor or booster 32 supplying primary air acting as a vehicle for the fuel. The kiln is provided with an external wind box 38, a perforated conveyer 50 for clinker issuing from the kiln and a cooling tower 60 into which the conveyer discharges and from which the clinker is discharged under manual or automatic control. Air is forced by a motor compressor 43 into a conduit 45 from which primary air is conducted to the booster 32, the remaining air dividing and being preheated in the wind box 38 and in the casing of the cooling tower 60 before furnishing secondary air for combustion in the kiln. Regulating devices 130, 145 ensure respectively a constant weight of air and a constant rate of fuel supply under steady temperature conditions in the kiln ; the air pressure entering the wind box 38, which encloses a spiral fin 48 on the rotating kiln, is maintained constant by a device 143 and a motor operated valve 135 whereas the air passing through the cooling tower 60 is manually adjusted at 144. The speed of rotation of the kiln and the speed of the conveyer 50 are adjusted by rheostats 18, 55 so coupled as to maintain speed relationship. The discharge of clinker from the cooling tower is dependent either upon the temperature in the tower or the air pressure in the tower casing at will and tends to maintain one or other of these conditions constant. A photo-electric cell 96 is trained upon the clinkering zone in the kiln and connected through an amplifier 100 so that the contact 107 of a two-position relay is in a median position at normal temperature. Temperature variations cause this relay to actuate a reversible electric motor which changes the position of a rod 122 carrying pairs of contacts 120, 121 so as to vary the delivery of air and fuel to the burner 23. The fuel supply is automatically controlled to a steady rate by a rheostat 31 in series with the motor 26 and operated by a reversible motor and the contact 148 of an ammeter or wattmeter responsive to the power draft of the motor 26. The air supply is automatically controlled by the contact 128 of a wattmeter responsive to the power consumed by the compressor 43 as described in Specification 308,369, [Class 110 (i)]. The contacts 128, 148, co-operate with the pairs of contacts 120, 121 respectively. The discharge of clinker is effected by a motor 62 operating a dumping wheel. A switch 66 permits manual operation. A relay 72 may be energized by a switch 83 or 84 chosen by operating manual switches 81, 82. The switch 83 is operated when the cooling tower temperature is low enough and the switch 84 when the air pressure in the tower casing is high enough. The actuated relay 72 starts the motor 62 and is retained energized through a switch 78 opened at each 90‹ of revolution of the dumping wheel, so that dumping continues until the temperature has risen or the air pressure has fallen. U.S.A. Specification 1,945,652 is referred to.