GB261218A - Pressure filters - Google Patents

Abstract

261,218. McCaskell. J. A. Jan. 18, 1926. Rotary filters.-Liquid is fed to a filter by air under pressure which is also used to force the liquid through the filter, means being provided for maintaining the liquid in the filter at a constant level, for subjecting the filtering medium to a rapid pulsation and for discharging the solid matter, while filtration is taking place, without allowing the air under pressure to escape. The filter shown is of the type comprising disc elements 2, built up of separate sector-shaped parts, mounted on a rotary shaft 13, which is provided with longitudinal passages for the flow of the filtered liquid from within the sectors to a rotary valve at the end of the shaft. The rotary valve provides for the discharge of the filtered liquid and has a connection whereby the sectors are subjected to pulsations of air under pressure at that point in each rotation at which the adhering cake is removed. The material for treatment is supplied to a montejus 131 through a non-return valve 135, air being vented from the montejus through one port of a three-way valve 136. When the montejus is sufficiently full a float 139 operates a pilot valve 138 which supplies air to a cylinder 137 containing a piston connected to the valve 136. The vent is then closed and the montejus connected to a pipe 130 which supplies air under pressure to force the material from the montejus through a non-return valve 134, a pipe 150, and a valve 113 to the closed filter casing. The valve 113 is operated similarly to the valve 136 by means of a float in the filter, a pilot valve 117, and a cylinder containing a piston. An electric contact is provided so that if the operation of the valve 113 fails a valve 127 is closed by a solenoid 125 and shuts off the supply of air to the montejus. Filtration takes place under the pressure of air supplied to the filter casing through a pipe 114 with a pressurereducing valve 144. At the side where the filter discs in their rotation pass into the liquid the casing is provided with a separate pocket for each disc. The air under pressure supplied to the rotary valve at the end of the central shaft is passed first through a valve oscillated from the central shaft by eccentric gearing so that it reaches the sectors just before they enter the liquid in pulsations which cause the cake on each sector to fall away therefrom. Scrapers 28', Fig. 6, mounted on the edges of the pockets and pressed against the discs by springs 30<1> direct the cake into spaces between the pockets leading to a chuta 16. Fig. 1, and casing 17, Fig. 7. The casing 17 has an extension 17<a> and an inner casing 20. A worm 18 compresses the solid matter into the tapered end of the casing 20 and discharges it through a nozzle 26. The solid thus forms a plug preventing the escape of air from the filter. The outer end of the casing 20 is perforated and surrounded with filter cloth, some liquid escaping through the filter cloth to an outlet 45. The solid matter is directed to the worm by a rotary device with paddles 40, Fig. 1. A modification is described in which the nozzle 26 is bent downwards and provided with a spring- controlled valve. A reciprocating plunger may take the place of the worm 18.