GB930190A - Method of and apparatus for grinding solid material - Google Patents

Abstract

930,190. Grinding. HARDINGE CO. Inc. Nov. 3, 1960 [Nov. 12, 1959], No. 37800/60. Class 59. A method of grinding solid material comprises the steps of treating an elastic fluid to provide it with desired characteristics, introducing said treated elastic fluid together with solid feed material into the feed entrance of a grinding mill which is substantially unprotected relative to the passage of said solid material and untreated surrounding elastic atmospheric fluid, causing said elastic fluid to flow through the mill, withdrawing said elastic fluid from the exit of the mill, and regulating the pressure of the treated elastic fluid discharged into the unprotected feed entrance of the mill to produce at said feed entrance a predetermined pressure operable to control the inlet of any of the surrounding untreated atmospheric elastic fluid to the mill through said feed entrance as desired. As shown in Fig. 1, material 18 is supplied by means of a conveyer 20 and feed shoot 14 to the feed opening 22 of a mill 10 through which air is circulated by means of a fan 38, conduits 30, 40 and a classifier 26. A heater 50 located at the pressure side of a fan 54 to which air is supplied by an inlet tube 52 controlled by a damper 56, supplies hot air through a conduit 62 to the feed opening 22. Conduits 40, 62 have branch conduits 42, 64 which deliver into a collector 46 the upper end of which communicates with a fan 68, the inlet tube 70 of which is controlled by a damper 72. The pressure differential at the feed opening 22 may be controlled by a draft gauge 76 connected electrically to a control panel 78 which is connected to motorized modulating control linkages 80, 82 whereby the dampers 56, 72 may be controlled. In a modification, Fig. 5, a blower 165 introduces air under pressure to a heater 166, the outlet of which communicates with the feed and discharge ends of a mill 172 by means of conduits 170, 168. Material and moistureladen air is drawn through grate 176 and any oversize material from classifier 178 is discharged back into the interior of the mill. Fine material from the classifier may be delivered to a classifier 184 any oversize from which is returned by conduit 186 to the feed end of the mill while fine products from classifier 184 are withdrawn by a fan 188 controlled by damper 190. In a further modification, Fig. 6, the circulating system for the interior of a mill 198 comprises a fan 200, the pressure end of which is divided between conduits 202, 204, conduit 202 communicating with the lower portion of the mill so as to direct a current of air from the lower to the upper portion thereof for entraining the finer products produced by the mill for removal therefrom. The inlet end of fan 200 communicates with a product collector 206. Conduit 204 communicates with a dust collector 216. The system is supplied with hot air by a heater 220 connected to the pressure side of a fan 224 controlled by a damper 228.