GB181044A - Improvements in or relating to the filtration of liquids - Google Patents

Abstract

181,044. Bramwell, B. Jan. 6, 1921. Filters with loose filtering- materials; separating by gravity. - Sand or other granular filtering-medium is removed layer by layer from a filter chamber, until the chamber is empty; the sand is washed, and uniformly distributed in a similar manner to the same or a like filter chamber. The sand may be removed by means of one or more suction nozzles moving over the bed and adapted to be lowered automatically. A suction nozzle 9, Fig. 1, is connected by swivel-jointed pipes or a flexible hose 13 to a pump 8, which, with a sand-washer 10, is mounted on a carriage 7 moving on rails on a gantry 5, which itself moves on rails 5 extending along the sides of filter chambers A, B. Sand removed from the chamber A is passed to the washer and distributed through an outlet 17 to the chamber B. Dirty water leaving the washer by an outlet 18 is discharged into a trough 19 on the gantry 5 and passes away by a channel 20. Below the nozzle 9 may be carried a propeller 14 or other stirring-device driven by a vertical spindle on an electric motor 15. Or jets of water may be directed near to the orifice of the nozzle. The water for carrying the sand in suspension may be wholly or in part supplied by a reverse flow upwards through the filter bed. The suction pipe may be supported by a float 23, the vertical movement of which is controlled automatically by the permitted fall of the water-level in the chamber A, and the vertical movement of the suction pipe may be electrically controlled. In operation, the carriage 7 is traversed to and fro across the gantry 5 while the latter is moved slowly, either continuously or intermittently along the length of the filter chambers. The uppermost layer from the chamber A, consisting of mud and other impurities may be discharged directly into the trough 19. By swinging through 180‹ an arm 11 which supports the suction pipe, the apparatus can be brought into position for cleansing the chamber B and returning the sand for use in chamber A. Where a reverse flow of water upwards through the filter bed is used for the cleaning operation the floor of the chamber may be constructed, as shown in Fig. 5, with shallow ridges, between each pair of which is a collecting and distributing pipe 29 covered by a shield 31 and having a slot or perforation 30 at the top. A separate valve may be provided for controlling the reverse flow through each of these pipes, the valves being operated by the movement of the gantry 5. Instead of using two filters, one filter and a receiving tank may be used, the sand from the filter being passed through a washer on its way from the filter to the tank, or on its return from the tank to the filter. In an arrangement of an annular filter with a concentric annular tank, the gantry carrying the pump, sand-washer &c. travels on circular rails. Several filter chambers may be placed in one or more rows or in a circle and the chambers cleansed successively, sand being passed from the, chamber undergoing cleansing to the adjacent chamber that has last been cleansed. A further arrangement is illustrated in Fig. 12. A carriage supporting a suction pipe travels over the filter E - - K. To - cleanse any filter the suction pipe is connected by a flexible hose to the corresponding branch 36 of a pipe system and the sand is drawn by a pump 33 through a washer 34 to a tank Q. When the filter has been emptied, the valves of the pipe system are altered so that the pump returns the sand from the tank Q to the filter. Automatic electrical means may be provided for opening and closing the necessary operating-valves in the above-described systems of filters and for moving the cleansing-apparatus over a filter and from one filter to another. Fig. 16 shows an arrangement for this purpose. A pivoted valve 48 at the base of a sand-washer 10 is normally held open by the weight of sand therein. When a filter chamber has been emptied and sand ceases to pass to the washer, the valve closes and its lever 49 closes electric contacts 47 to establish a circuit by means of which valves are operated and motors started or stopped on the requisite sequence. Fig. 17 shows a closed filter with suction nozzles 9 depending from a cranked pipe, which passes through the top of the filter and can be both rotated and moved vertically. It is stated that for small filter units a sufficient number of branched suction nozzles may be provided that the horizontal traverse of the nozzles need only be slight. Apparatus similar to that for withdrawing sand by suction from a filter is applied, Fig. 14, for withdrawing sludge from a settling- tank through which the dirty water from a sandwasher is passed previous to re-use in connection with the cleansing operation.