GB365148A - Improvements in or relating to dewatering solid materials - Google Patents

Abstract

365,148. Filters. WILLIAMS, P. T. and MINERALS SEPARATION, Ltd., 62, London Wall, London. Oct. 8, 1930, No. 30187. [Class 46.] In a process of vacuum filtration for liquids in mineral-dressing plants, including coal concentrates and ore pulp, the filtering medium used has a large percentage of open area and a vacuum is applied such that the average amount of water passed through the medium is greater than twenty cubic feet per hour per square foot of filter surface, the filtering medium being moved through the liquid fast enough to carry away the larger solid particles as rapidly as they are introduced to the filter. A filter medium having an open area of 40 per cent arranged on a drum having a peripheral speed of twenty feet per minute is mentioned as suitable. The apertures in the filtering medium may be of the same order of size as the maximum particles to be separated. Figs. 1 and 2 show a rotary drum filter for use in the process. The drum comprises a casting 13 which supports a filter medium 14 of wire cloth, the space beneath the cloth being divided into numerous longitudinal cells, for example thirty-two, by ribs 15. The space within the drum is occupied by a stationary valve 24 divided by a central partition 27 and having suction connections 25, 26. The casting is shaped so that each cell slopes to a central pocket 18, from which the liquid is discharged through a passage 19, inclined contrary to the direction of rotation. The passages 19 of adjacent cells are arranged to communicate alternately with the two compartments of the valve, the valve face having openings 21, 22, so that the cells dipping into the material under treatment in a tank 28 and the cells rising therefrom are subjected to suction. The passages 19, as the cells rotate, also pass over a port 33 in a chest 34, a blast of air or steam from which aids the removal of the cake by a doctor 30. The leading edges of the ports at the ends of the passages 19 are made to conform in shape with the co-operating edges of the ports 21, 22, 33, so that the suction and blast start sharply.