METHODS AND APPARATUS FOR MEASURING THE THICKNESS OF FILTER CAKES ON FILTER ELEMENTS

摘要

1354721 Monitoring thickness of filter cake SEITZ-WERKE GmbH 9 July 1971 [10 July 1970] 32319/71 Heading B1D The attainment of a predetermined thickness of filter cake on uppermost filter element 31 is detected by continuously drawing off liquid through a vertically adjustable filter body 13, whose lower surface includes a by-pass opening (18) adapted to be closed by the filter cake on the upper surface of element 31, such closure causing body 13 to act as a filter so that the drawn off liquid suddenly changes from unfiltered slurry to clear filtrate, the change be observable visually or detected by a turbidity meter at window 28. The meter may automatically switch off slurry pump 36 and actuate signal 45. Fig. 1 (not shown) illustrates the construction of flat two-sided filter body 13 and its mouting on an axially adjustable spindle carrying, outside the filter housing 30, a scale indicating the distance between body 13 and element 31 and hence the predetermined thickness at which the signal will be given. Fig. 2 shows the use of body 13 in a multi-element filter using filter aid, which is added to reservoir 33 through which slurry is circulated via 35, 36, 30, 31, 37, 38 and 39 to deposit the filter aid on elements 31 as an initial step. Thereafter slurry is delivered through line 34 and reservoir 33, and valve 38 is switched to discharge filtrate through line 40. Reservoir 33 is under atmospheric pressure so that pump 36 causes the drawn off liquid to flow through filter body 13 and line 41 to reservoir 33. Filter aid may be continuously added to the slurry during filtering. The body 13 can be used to measure the thickness of cake on element 31 when filtering therethrough is interrupted, the body being progressively lowered until the change from slurry to filtrate is observed and scale (22) then indicating the cake thickness.