GB760272A - Improvements in or relating to filter plants - Google Patents

Abstract

760,272. Filters. NORSK HYDROELEKTRISK KVAELSTOFAKTIESLSKAB. May 18, 1954 [May 19, 1953], No. 14615/54. Class 46. A two-way valve A is moved over from the position shown by a time-controlled device. A container G is thus connected to the atmosphere, and liquid from column K and from a filtrate pipe F flow along pipe H into G until the level therein reaches that of an overflow P from a liquid trap J. A level-sensitive device in G causes reversal of a valve B (from the position shown) when this level is reached, the pressures on both sides of the valve B being then equal. (Pipes K and L are connected to a common vacuum source V). Thereafter the liquid in pipes K, H, and container G comes to rest while filtrate flows out at P. A time-controlled device causes return of valve B when the sludge layer on filters E reaches a desired thickness, and the device controlling valve A returns that valve to the position shown immediately afterwards. Compressed air from a pressure maintained reservoir N now flows into container G, and when the liquid level therein is forced below the level of overflow P liquid is forced along pipe H, through valve B, along pipe F and back through the filters E. The time during which air pressure is exerted on the liquid in the container G is sufficient for the sludge cakes to be loosened from the filter cloths and to fall to the bottom of the thickener D. Valve A is then reversed and the cycle is repeated. In a modification, Fig. 2 (not shown), the container D is a closed pressure-container on a level with the container G, and it is supplied with liquid to be filtered from an elevated tank containing liquid at atmospheric pressure. The trap J is dispensed with, and pipes K and L communicate with the atmosphere.