GB395912A - Improvements in or relating to drying devices for separated coarse material in ball or tube mills - Google Patents

Abstract

395,912. Ball or tube mills ; drying. JACKSON, L. MELLERSH-, 28, Southampton Buildings, London.-(Krupp Grusonwerk Akt.-Ges., F. ; Buckau, Magdeburg, Germany.) Oct. 21, 1932, No. 29489. [A Specification was laid open to inspection under Sect. 91 of the Acts, Oct. 22, 1932.] [Class 59.] In a ball mill in which an air current passing through the mill carries the ground material to a sifter where the coarse material is separated out and is conducted back to the mill drum, the coarse material is dried previous to its re-introduction to the drum. The coarse material may be dried either in the sifter or in the return pipe to the drum. As shown in Fig. 1, the material to be ground is fed into the drum 21 through a pipe 2, through which the air current enters, and the ground material is carried by the air current up a pipe 22 to a sifter 23, the air then passing through a dust extractor 24 and back to the mill through fan 38 and pipe 40. Material separated in the sifter 23 passes through a pipe 26 to a drying column 27 comprising staggered ledges 28 from which the material is deflected as it falls downwardly into the pipe 40 through which it is carried by the air blast into the mill. Hot air is admitted to the dryer through a pipe 29 and ascends through the falling separated material and leaves either through a pipe 32 or is led through a pipe 33 into the dust extractor 24. An alternative feeding device 36 discharges fresh material into a byepass pipe 37 through which a current of air from the fan 38 passes and the fine material is carried thereby into the sifter 23. The coarse material passes through a pipe 39 into the pipe 40 and is carried into the mill through an extension 401. In a modification, Fig. 2, hot air from a pipe 41 is branched at 42 to the inlet of the mill, the return air from the fan 52 surrounding this pipe and conveying the ground material to a sifter 46 from which the coarse material returns to the mill through a pipe 47 and the fines are conveyed to a cyclone 49. Branch pipes 55, 56, 57 from the pipe 41 supply hot air to various parts of the circuit. The mill, separator and cyclone may be jacketed to receive hot air separately or in succession or the hot air may pass through the jackets and then into the mill circuit.