GB296697A - Improvements in and relating to ball mills for pulverising coal and the like and feeding it to a burner or furnace - Google Patents

Abstract

296,697. Crowe, P. L. March 1, 1927. Ball and like mills.-A combined ball mill and pulverized fuel feeder for burners or furnaces comprises a unitary rotatable structure in the form of two or more ball mills 27, 39 separated from one. or more fans 33 by one or more screens 32, 36 through which the pulverized material is impelled and simultaneously mixed intimately with air by the action of the fans due to the rotation of the structure whereby the mixture is finally delivered to the burners or furnaces. The mills 27, 39 and fan 33 rotate together in bearings 1, tubular portions 28, 36 of which form the journal bearings. A hopper 29 is provided for the mill 27 and is furnished with tubes 43, 30 for supplying hot air and atmospheric air respectively to the mill. A hopper 41 is provided for the mill 39, an annular lip 42 entering the mouth end of the mill 39 to prevent the outflow of balls and material therefrom. Hot air is supplied to the mill through a tube 43. The tubular portion 36. which forms one journal bearing, enters the mill 39 and is perforated around the circumference. A partition, forming a screen 38 in the mill 39 blanks the end of the tube 36. The fan 33 has blades on each side of opposite inclination so: that the pulverized coal and air are drawn from the mill 27 and discharged into the mill 39 as indicated in Fig. 1 by the arrows. The coal dust is again pulverized, together with any material fed through the hopper 41 in the mill 39 from which it is discharged through the screen 38 and outlet 40 to the burners. In a modification the mill 27 is divided by annular partitions into three compartments, the balls of which grind to different degrees of fineness. Fig. 3 shows three ball mills 86, 95 and 102 mounted upon a common shaft running in bearings, the shaft being formed by concentric tubes which merge into fans 119, 115, 113 and 106. The fans 119, 115 are covered by a casing 88 provided with hoppers 89<1>, 90 for supplying the mill 95 and hoppers 99, 109 are provided on each side of the fans 106, 113 for supplying material to the mills 102, 95, the mill 95 being divided into two compartments by a partition 96. The mill 86 is divided into two stages by an annular partition 87 and the mill 102 is divided into three stages by similar partitions, these stages varying- the degree of fineness of the ground material. The central tube 110 of the concentric shaft communicates with fans 115, 119 and 113 and the ground material from the mills 86, 95 passes through perforations 93, 97 respectively, in the outer tube 104 of the concentric shaft, to these fans, for delivery through the tubular shaft 110. The mill 102 discharges the coal dust through perforations 105 in a concentric tube 101 which communicates with the fan 106, the dust being discharged from the fan by way of the annular space formed by the tubes 110, 104. Annular lips are formed at the mouth of each mill to prevent the outflow of the balls and material, and hot air may be introduced into the mill through the hoppers. The mills are driven preferably by an induction motor, the pole pieces 129, Fig. 1, being secured to the casing 31. Two or more induction motors may drive the mill shown in Fig. 3. Specification 296,682 is referred to.