초록 ▼

Limitation of the number of cassettes in an assembly currently used for the production of permeate is obviated by grouping plural cassettes into racks one or more of which may be isolated while permeate production from the remaining racks is uninterrupted. Ancillary functions such as back-pulsing, c

Limitation of the number of cassettes in an assembly currently used for the production of permeate is obviated by grouping plural cassettes into racks one or more of which may be isolated while permeate production from the remaining racks is uninterrupted. Ancillary functions such as back-pulsing, chemical cleaning and testing for defects in membranes ("integrity testing") in one or more racks may proceed while production of permeate continues. The number of racks in a bank is determined by the period of the overall filtration cycle, typically 15 min, in which filtration period the ancillary period is a minor portion, typically 30 sec. The racks make it possible to use automatic on/off valves which open and close quicker than larger ones. The resulting saving in time, energy, and equipment costs, which when back-pulsing with permeate is surprisingly economical, is even greater when a chemical cleaning solution is to be used. In addition, the saving in cost of equipment and avoiding the wear and tear of pumps which are intermittently stopped and started, produces unexpected economic benefits. For even greater savings in operating costs, a bank of cassettes, or a bank of racks may be operated with a "gravity flow" system.

대표청구항 ▼

[ We claim:] [1.]1. In a large plant comprising a bank of multiple cassettes for filtering a contaminated substrate, immersed in said substrate, and in open fluid communication with each other, each cassette comprising a multiplicity of membrane modules connected for operation in parallel in the cas

[ We claim:] [1.]1. In a large plant comprising a bank of multiple cassettes for filtering a contaminated substrate, immersed in said substrate, and in open fluid communication with each other, each cassette comprising a multiplicity of membrane modules connected for operation in parallel in the cassette, a method comprising,connecting said multiple cassettes having a total of at least 100 modules, for operation in parallel in said bank without selectively isolating any module thereof;isolating at least one cassette in said bank for a predetermined period of time sufficient to execute an ancillary operation with said cassette; and,continuously withdrawing permeate from said bank and from said cassettes left unisolated. [2.]2. The method of claim 1 wherein each said module has a membrane area of at least 10 m.sup.2 and comprises fibers greater than 0.5 meter long; and, providing one automatic cassette valve on a manifold in each cassette to control withdrawal of permeate from modules in each cassette, and to control flow of back-pulsing fluid into modules in each cassette, respectively. [3.]3. The method of claim 2 including isolating from 6 percent to 50 percent of the cassettes in said bank to provide at least one isolated cassette; and, said ancillary operation comprises flowing a back-pulsing fluid through said isolated cassette.