REMOVING SLUDGE FORMED IN SOLUTIONS USED IN METAL PRE-TREATMENT PROCESSES

摘要

1361489 Removal of sludge from solutions used for treating metals CARRIER DRYSYS Ltd 4 April 1972 [12 May 1971] 14495/71 Headings BID and B2P Sludge-containing solution, such as zinc phosphate solution which has collected in tank 4 after being sprayed over automobile bodies 1 moving through compartment 3, is withdrawn from tank 4 by pump 9 at a rate in excess of the capacity of a subsequent filter and is passed through pipe 23 to centrifuge 14 which separates some of the soultion from the mixture, this solution being returned from the top of the centrifuge through pipe 26 to tank 4. The concentrated sludge leaving the bottom of the centrifuge flows to a band 17 of filter paper drawn from a reel across trough 19, the rate of flow being controlled to within the capacity of the filter, and the filtered solution is returned through pipe 20 to tank 4. Clear solution flows over weir 12, and is pumped through heater 6 to the spray means 7 in compartment 3. When the thickness of sludge on band 17 is too great to allow liquid to run through the filter as fast as it is being supplied thereto, the liquid level in trough 19 rises and operates a float switch (not shown) which causes the band 17 to run on and expose a fresh section of the band. The band carrying collected sludge moves down chute 21 to skin 22. The lower outlet 15 of centrifuge 15 may comprise an adjustable valve. In one embodiment, sludge-containing solution is pumped to centrifuge 14 at the rate of 110 gallons per minute, and concentrated sludge is delivered to filter-band 17 at 10 gallons per minute. Two or more centrifuges leading either directly, or via a further centrifuge, to one or more filters may be employed. The piping is preferably made of stainless steel.