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System for filtering a liquid
| Details |
Inventors: Galaj, Stanislas;
Assignee: Compagnie Generale D'Electricite (Paris, FR)
Primary Examiner: Therkorn; Ernest G.
Assistant Examiner:
Attorney, Agent or Firm: Sughrue, Mion, Zinn, MacPeak & Seas
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 P.sub.1 at the inlet to the first filter, the backpressure P.sub.2, the pressure P.sub.3 of the liquid between the two filters and the pressure P.sub.4 at the outlet from the second filter. Means (34) determine A=P.sub.1 -2P.sub.3 +P.sub.4, and B=(K/2N)(P.sub.2 -2P.sub.1 +P.sub.4), 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. |
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DETAILED DESCRIPTION The present invention provides a filter of the above-defined type, wherein said filter is designated a first filter, said first constant pressure is a predetermined pressure P.
sub.
1, and said second constant pressure is a predetermined pressure P.
sub.
2 which is greater than P.
sub.
1, the improvement wherein the system further includes: (h) a second filter identical to the first filter, the inlet to the second filter being connected to the opening of the outlet from the enclosure of the first filter by a first pipe, the outlet from the second filter being closed, the opening of the outlet from the second filter enclosure being connected to the flow rate measuring apparatus via the backpressure unit; (i) means for impressing said predetermined speed parallel to the inside surface of the porous member of the second chamber to the liquid contained therein; (j) a manometer for measuring the pressure P.
sub.
3 of the liquid flowing in said first pipe; (k) means for maintaining the pressure P.
sub.
4 of the liquid flowing in a second pipe constant when the backpressure unit is not operating, said second pipe connecting the outlet of the back pressure unit to the inlet of the flow rate measuring apparatus; (l) a processor circuit receiving signals representative of the pressures P.
sub.
1, P.
sub.
2, P.
sub.
3, and P.
sub.
4, said circuit being capable of determining firstly the value: A=P.
sub.
1 -2P.
sub.
3 +P.
sub.
4 and secondly the value: B=(K/2N)(P.
sub.
2 -2P.
sub.
1 +P.
sub.
4), where K is a predetermined safety factor less than unity, and N is a predetermined coefficient depending on the membranes of the porous members; and (m) a control circuit connected to the processor circuit and to the backpressure unit, said control circuit being capable of delivering a control signal when the values A and B as determined by the processor circuit are equal to each other, said control signal causing said backpressure unit to operate.
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Liquid Purification 
