| 摘要 |
1,263,407. Filtering process and apparatus. PULLMAN Inc. 25 Feb., 1970 [11 March, 1969], No. 9194/70. Heading B1D. A slurry 42 of phosphoric acid and calcium sulphate is applied to a filter medium 48 to form a cake 58 which may crack during the initial part of the filtering cycle B, the cake surface being broken up by rake 56 before washing liquid is applied (nozzles 50), so that loosened cake particles are washed into the cracks and fill them, thereby obviating wash liquid channelling. Fig. 3 shows the process performed on an inward-flow rotary filter drum, with a final scraper blade 52 and a pan 44 having a vibrator-mixer 46. In Figs. 1, 2 (not shown) the process is performed on a downward-flow rotary table filter, whose cells 10 are inverted downstream of the washing stage. The rake may comprise hairpin-like wires whose closed ends extend from an elastomeric and adjustable support. The first fraction of wash liquid, passed before the cracks fill, may be discarded. There may be several successive cake-loosening and washing stages. The process is applicable to stationary leaf filters, using moving rakes. |
