GB754724A - Improvements in or relating to a bowl mill for pulverizing coal and similar materials - Google Patents

Abstract

754,724. Bowl mills. COMBUSTION ENGINEERING, Inc. Jan. 14, 1954 [Feb. 3, 1953], No. 1108/54. Class 59. A bowl mill comprises a horizontally-disposed rotatable bowl 9 having an upwardlysloping and outwardly-extending grinding surface 9a co-operating with rolls 17 for crushing material fed to the centre of the bowl, a housing 10 surrounding the bowl and spaced from the periphery of the latter to provide an annular passage 40 for the upward flow of air, vanes 42 extending inwardly from the outer wall of the annular passage for deflecting the upward air stream in the direction of rotation of the bowl, a deflector 41 which projects inwardly from the inner wall of the housing immediately ahead of each roll 17 and is shaped to deflect material entrained in the upward air stream downwardly and inwardly towards the lower portion of the associated roll, and liners 44 secured to the inner wall of the housing above the annular passage for directing the upward flow of air and entrained material inwardly of the housing. Each of the rolls 17 is rotatably carried on a shaft 18 mounted on an arm 22 which is secured to a trunnion shaft 15 and acted upon by a spring 23 to urge the roll towards the grinding surface 9a ; each roller assembly (of which three are shown in Fig. 3) may be removed through an opening 16a in the housing closed by a door 16. The annular passage 40 communicates with the space above the bowl through three arc-shaped openings 40a extending over part of the distance between successive rolls 17 as shown in Fig. 3 and, intermediate these openings, is substantially closed off by arc-shaped plates 43, Figs. 1 and 3, extending inwardly from the casing; the vanes 42 are disposed in the passage 40 beneath the openings 40a so as to direct the air flow in the direction of rotation of the bowl and against the deflectors 41. Each liner 44 extends between adjacent rolls 17 and immediately above the annular passage and has its inner face disposed vertically at its lower portion 44a, Fig. 1, and inclined inwardly at its upper portion 44b. A further liner 45 extends between adjacent liners 44 and beneath each roll 17. The outer peripheral edge 39 of the bowl slopes upwardly and inwardly so as to be generally parallel to the opposite upper edge of the annular passage 40. Material which is fed through a shoot 33, Fig. 1, on to the centre of the bowl is propelled outwardly by the downwardly-sloping and vaned surface 34a of the bowl on to the grinding surface 9a, and after crushing passes over the lip 39 of the bowl into the rising air stream through the openings 40a; air is admitted to the housing through an opening 13. Some of the crushed material in the air stream is deflected downwardly by the deflectors 41 so that the heavier particles fall on to the grinding surface for further crushing and the remainder is carried upwardly and passes through openings 29 into a classifier 25 ; the liners 44 cause the material to flow generally upwardly and inwardly and minimise any tendency to spill through the annular passage 40. Material of desired fineness is discharged from the classifier through the outlet 31 and coarser particles are returned to the bowl through an outlet 28a.