| 摘要 |
First and second identical filters (6, 20) are connected in series. A backpressure unit (30) for intermittent backwashing is connected to the outlet from the second filter. Means are provided for measuring or setting the pressure P1 at the inlet to the first filter, the backpressure P2, the pressure P3 of the liquid between the two filters and the pressure P4 at the outlet from the second filter. Means (34) determine A=P1-2P3+P4, and B=(K/2N)(P2-2P1+P4), where K and N are constant coefficients, and a circuit (35) causes the backpressure unit to apply backpressure for backwashing when A=B. This amounts to comparing conditions in the first and second filters and triggering backwashing only when required, thereby avoiding wasting time with too frequent backwash operations, or conversely with dismantling and regenerating the filters due to too infrequent backwashing leading to clogging that cannot be cleaned by backwashing. The filter is particularly applicable to filtering organic liquids, such as milk, wine or beer. |
