Clarification performance test using modified (6000rpm) centrifugal clarifier, I

Nakashima, Kazuya; Yasu, Takami; Kawata, Tomio

Object: The centrifugal clarifier in the EDF (II) was modified into a higher rotation speed (6000rpm type) one. By conducting performance tests using modified one, its characteristic is compared with the old one and obtained data will be reflected in a machine design which will be equipped in a future plant. Method: A number of tests in connection with mechanical perfomance, clarification performance, sludge washing, etc. have been carried out using the modified one under the cold condition. Result: The following results were obtained. (1)Operation of the clarifier was conducted under the nearly same condition as those of the RETF (Recycling Equipment Test Facility). The results of these tests show that there were no problems on mechanical performance in the clarification operation, but it happened unstable vibration in the downward rotation. Accordingly, for the application of the modified clarifier to the RETF clarification process, it is pointed out to make the vibration characteristics stable in the downward rotation. (2)Concerning clarification performance, though fractional separation efficiency depended on average particle size, it was more than 94% for 0.5m particle size at rotation speed 6000rpm and feed-rate 100/h. (3)The relations of the leak rate of feed solution and the condition of feed at 6000rpm were confirmed and the optimum feed condition was verified. (4)As compared with the modified one (6000rpm type) and sub-critical typed one(3000rpm type), it was confirmed that the former was superior to the latter with respect to the clarification performance of smaller particle size, but increased with respect to the leak rate of feed solution.