초록 ▼

High flow, low-pressure ultrafiltration or microfiltration spiral wound membrane cartridges are used in filtration of liquid feedstocks having high suspended solids. Applications may utilize either vacuum or pumping for transmembrane drive pressure (TMP), and gas may optionally be bubbled up through

High flow, low-pressure ultrafiltration or microfiltration spiral wound membrane cartridges are used in filtration of liquid feedstocks having high suspended solids. Applications may utilize either vacuum or pumping for transmembrane drive pressure (TMP), and gas may optionally be bubbled up through the cartridges with certain feedstocks. Water permeate flux rates as high as 90 gallons per square foot per day (gfd) can be obtained at TMPs below 5 pounds per square inch. By locating each spiral wound cartridge in its own casing and supplying liquid feedstock to an open lower end of the casing, as opposed to submerging such cartridges in a tank filled with feedstock, overall low pressure performance is greatly improved. High permeate flow can be maintained for long periods of time between shutdowns for intensive cleaning. TMP is gradually increased to maintain a substantially constant rate of permeate discharge until a target is reached, indicative of solids accumulation on the membrane surface to an undesirable extent; then backflushing is effected for a short time. Discarding the hold-up volume of feedstock in the cartridge, the backflushing fluid and dislodged solids, allows production to be promptly resumed with fresh feedstock at performance at near original levels.

대표청구항 ▼

The invention claimed: 1. A system for the filtration of a liquid feedstock high in suspended solids for the purpose of economically producing permeate lean in suspended solids, which system comprises: a) a plurality of spiral wound membrane filtration cartridges which each includes membrane filter

The invention claimed: 1. A system for the filtration of a liquid feedstock high in suspended solids for the purpose of economically producing permeate lean in suspended solids, which system comprises: a) a plurality of spiral wound membrane filtration cartridges which each includes membrane filter sheet material, feed spacer sheet material and permeate carrier sheet material spirally wound about a perforated permeate collection tube and confined within an open-ended tubular casing in a generally cylindrical, liquid-tight configuration, which casing is not submerged in liquid in a tank but has its exterior surface in contact with the atmosphere, b) an interconnected group of bases each of which supports one said cartridge in a substantially vertical orientation, c) said interconnected group of bases being connected to a supply of a liquid feedstock, d) a seal between each said base and each said cartridge so that liquid feedstock being supplied flows upward in said cartridge through said feed spacer material, e) means for creating a vacuum within each said permeate collection tube to cause liquid lean in suspended solids to permeate through said membrane sheet material as a result of transmembrane pressure (TMP) thereacross and for withdrawing permeate from said cartridge, means for controlling the supply of liquid feedstock so that liquid level in said casing is maintained at about a constant height therewithin and said filtration cartridge operates in dead end mode, f) a bubbler in each said base for creating an upwardly flowing stream of gas bubbles in the liquid feedstock below said cartridge, which stream will enter said open end at the bottom of said cartridge and exit to the atmosphere at an open upper end of said tubular casing, g) a source of pressurized back-flush fluid, h) means for periodically initiating reverse flow of such back-flush fluid through the collection tube and the permeate carrier fabric sheet into said feed spacer material to back-flush said cartridge whenever permeate flow from said cartridge is indicative of an undesirable extent of solids accumulation on said overall membrane surface, and i) means for withdrawing from said system the liquid in said cartridge feed spacer sheet material of each cartridge which includes said back-flush fluid and solids dislodged by said back-flush fluid and the volume of feedstock in said interconnected supporting bases following completion of said back-flush flow and before resupplying fresh liquid feedstock to said bases and said cartridges. 2. The system of claim 1 wherein said feed spacer sheet material has a thickness of at least about 0.05 inch (about 1.3 mm) and not exceeding about 0.25 inch and has a corrugated pattern of between 2 and 6 corrugations per inch such as to allow an upwardly flowing stream of bubbles to rise in the axially extending spiral passageways provided by said feed spacer sheet material in a manner such that bubbles reach and scour active surfaces of said membrane sheet material flanking said feed spacer sheet material, whereby the provision of a net driving pressure of at least about 0.5 psi (about 26 mm of Hg) across said membrane sheet material causes permeation of water lean in solids and low in turbidity into said permeate carrier sheet material at a flux of at least about 5 gfd per psi of average net driving pressure over an extended period of time. 3. The system of claim 1 wherein said membrane has a permeability to water of at least about 50 gfd/psi and is of a microfiltration or ultrafiltration type made from polysulfone, polyethersulfone, polyvinylidene fluoride or polyacrylonitrile, and wherein feed spacer material is between 0.05" to 0.15" in thickness. 4. The system of claim 1 wherein an open cap is connected to each tubular casing at its top which allows gas bubbles to escape to the atmosphere and wherein a plurality of said caps are mechanically interconnected to collect overflow liquid flow therefrom for return to said supply of liquid feedstock. 5. A system for the filtration of a liquid feedstock high in suspended solids for the purpose of economically producing permeate lean in suspended solids, which system comprises: a) a plurality of spiral wound membrane filtration cartridges which each includes membrane filter sheet material, feed spacer sheet material and permeate carrier sheet material spirally wound about a perforated permeate collection tube and confined within an open-ended tubular casing in a generally cylindrical, liquid-tight configuration, which casing is not submerged in liquid in a tank but has its exterior surface in contact with the atmosphere and its top open to the atmosphere, b) an interconnected group of bases each of which supports one said cartridge in a substantially vertical orientation, c) said interconnected group of bases being connected to a supply of a liquid feedstock, d) a seal between each said base and each said cartridge so that liquid feedstock being supplied flows upward in said cartridge through said feed spacer material, e) means for controlling the supply of liquid feedstock so that liquid level in said casing is maintained at about a constant height therewithin and said filtration cartridges operate in dead end mode, f) means for creating a vacuum in each said permeate collection tube so as to cause liquid to permeate through said membrane sheet material as a result of transmembrane pressure (TMP), and for withdrawing liquid lean in solids from said cartridge, g) a bubbler in each said base for creating an upwardly flowing stream of gas bubbles in the liquid feedstock below said cartridge, which stream of bubbles will enter said open end at the bottom of said cartridge and exit to the atmosphere at an open upper end of said tubular casing, h) a source of pressurized back-flush fluid, i) means for periodically initiating reverse flow of such back-flush fluid through the collection tube and the permeate carrier fabric sheet into said feed spacer material to back-flush said cartridge whenever permeate flow from said cartridge is indicative of an undesirable extent of solids accumulation on said overall membrane surface, and j) means for withdrawing from said system following periodic reverse flow the volume of liquid in each said cartridge feed spacer sheet material which includes said back-flush fluid and any solids dislodged by said back-flush fluid and the volume of feedstock in said interconnected supporting bases and following said withdrawal resupplying fresh liquid feedstock to each said base and each said cartridge. 6. The system of claim 5 wherein said feed spacer sheet material has a thickness of at least about 0.05 inch (about 1.3 mm) and not exceeding about 0.25 inch and has a pattern of between 2 and 6 axially oriented corrugations per inch such as to allow an upwardly flowing stream of bubbles to rise in the axially extending passageways provided by said spirally wound feed spacer sheet material in a manner such that bubbles reach and scour active surfaces of said membrane sheet material flanking said feed spacer sheet material, whereby the provision of a net driving pressure of at least about 0.5 psi (about 26 mm of Hg) across said membrane sheet material causes permeation of water lean in solids and low in turbidity into said permeate carrier sheet material at a flux of at least about 5 gfd per psi of average net driving pressure over an extended period of time. 7. The system of claim 4 wherein said membrane has a permeability to water of at least about 50 gfd/psi and is of a microfiltration or ultrafiltration type made from polysulfone, polyethersulfone, polyvinylidene fluoride or polyacrylonitrile, and wherein feed spacer material is between 0.05" to 0.15" in thickness. 8. A system for the filtration of a liquid feedstock high in suspended solids for the purpose of economically producing permeate lean in suspended solids, which system comprises: a) a plurality of spiral wound membrane filtration cartridges which each includes membrane filter sheet material, feed spacer sheet material and permeate carrier sheet material spirally wound about a perforated permeate collection tube and confined within an open-ended tubular casing in a generally cylindrical, liquid-tight configuration, which casing is not submerged in liquid in a tank but has its exterior surface in contact with the atmosphere, b) an interconnected group of bases each of which supports one said cartridge in a substantially vertical orientation, c) said interconnected group of bases being connected to a supply of a liquid feedstock, d) a seal between each said base and each said cartridge so that liquid feedstock being supplied flows upward in said cartridge through said feed spacer material, e) means for withdrawing liquid which permeates through said membrane sheet material of each said cartridge by applying vacuum to said permeate collection tube through said base to create a net driving transmembrane pressure (TMP) of at least about 0.5 psi (about 26 mm of Hg) across said membrane sheet material to cause, such permeation and means for controlling the supply of liquid feedstock so that liquid level in said casing is maintained at about a constant height therewith in and said filtration cartridge operates in dead end mode f) a bubbler in each said base for creating an upwardly flowing stream of gas bubbles in the liquid feedstock below said cartridge, which stream will enter said open end at the bottom of said cartridge and exit to the atmosphere at an open upper end of said tubular casing, g) a source of pressurized back-flush fluid, h) means for periodically initiating reverse flow of such back-flush fluid through said base, the permeate collection tube and the permeate carrier fabric sheet into said feed spacer material to back-flush said cartridge whenever permeate flow from said cartridge is indicative of an undesirable extent of solids accumulation on said overall membrane surface, i) means connected to said interconnected group of bases for withdrawing from said system all of the volume of liquid in each said cartridge feed spacer sheet material, which includes any of said back-flush fluid and solids dislodged by said back-flush fluid, and the volume of feedstock in said supporting base following completion of said back-flush flow, and j) means for resupplying fresh liquid feedstock to said base and said cartridge following operation of said withdrawing means whereby permeation of water lean in solids and low in turbidity into said permeate carrier sheet material is achieved at a flux of at least about 5 gfd per psi of average net driving pressure over an extended period of time,. 9. The system of claim 8 wherein said feed spacer sheet material has a thickness of at least about 0.05 inch (about 1.3 mm) and not exceeding about 0.25 inch and has a corrugated pattern of between 2 and 6 corrugations per inch such as to allow an upwardly flowing stream of bubbles to rise in the axially extending spiral passageways provided by said feed spacer sheet material in a manner such that bubbles reach and scour active surfaces of said membrane sheet material flanking said feed spacer sheet material. 10. The system of claim 8 wherein an open cap is connected to each tubular casing at its top which allows gas bubbles to escape to the atmosphere and wherein a plurality of said caps are mechanically interconnected to collect overflow liquid flow therefrom for return to said supply of liquid feedstock. 11. The system of claim 8 wherein said membrane has a permeability to water of at least about 50 gfd/psi and is of a microfiltration or ultrafiltration type made from polysulfone, polyethersulfone, polyvinylidene fluoride or polyacrylonitrile, and wherein feed spacer material is between 0.05" to 0.15" in thickness.