Spiral wound membrane element

Details Spiral wound membrane element Spiral wound membrane element

1994-10-19

1996-07-23

Spear, Frank

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

21032183, B01D 6310

Patent

active

055386423

DESCRIPTION:

BRIEF SUMMARY
The present invention relates generally to spirally wound membrane devices useful for separation of components of fluid feed streams by means known as ultrafiltration, microfiltration, nanofiltration, reverse osmosis, and separations of gas mixtures.
Simple, single leaf spirally wound membrane devices have been known for some time. For example, British Patent 489,654 (Sep. 1, 1938) describes a countercurrent spiral membrane device containing a cellulosic membrane material used for dialyzing caustic soda lye. As discussed therein, with such a design it is possible to fit considerable effective surface area of dialyzing membrane into an extraordinarily small volume, for example, a cylindrical container. Similar single leaf spiral membrane devices are broadly used today in a variety of applications. The advent of reverse osmosis desalination of saline waters in the early 1960's led to a number of improvements in spiral membrane devices, especially in terms of size. U.S. Pat. No. 3,417,870 describes a means of spirally winding a plurality of reverse osmosis membrane sheets and spacer materials around a perforated hollow core in a manner so as to provide large diameter spiral devices. The design illustrated and described in U.S. Pat. No. 3,417,870 has since been commonly applied to reverse osmosis, ultrafiltration, gas separations, and other types of membrane applications. The membrane element comprises a plurality of membrane leaves. A permeate flow channel is affixed to and surrounds a porous central mandrel. Membrane leaves comprise semi-permeable membrane sheet folded so as to enclose the feed flow channel on the major surfaces separated by permeate fluid flow channel sheets. The permeate flow channel sheets are placed between folded major surfaces of semi-permeable membrane. The membrane leaves of permeate flow channel, semi-permeable membrane and feed fluid flow channel are then wrapped about the central mandrel. The permeate flow channel is sealed along the axial edges and radially distal edge to prevent permeate fluid communication with feed fluid. The feed fluid flow channel sheets are open at the axial ends to feed fluid flow axially through the spiral winding adjacent to the semi-permeable membrane.
U.S. Pat. No. 4,235,723 describes an alternate method of assembling spiral membrane devices, in which a flow guide member is attached to a perforated hollow core, and a parallel array of membrane envelopes are attached together in a manner such that the permeate from each membrane envelope empties into the flow guide member. Such an arrangement has been termed a "tributary design," since a series of tributaries feed into a main stream, that is, the flow guide member, which empties into the hollow core.
More recently, a number of patents have appeared which incorporate improved materials and modified flow paths in single and multiple leaf spiral elements. U.S. Pat. No. 4,834,881 discloses a variety of improved corrugated spacers for use in feed fluid channels. U.S. Pat. Nos. 4,8612,487 and 4,902,417 describe improved channel spacers consisting of ribbed plastic nettings. A similarly ribbed plastic screen useful as a permeate channel flow spacer is described in U.S. Pat. No. 4,476,022. Flow channel spacers in the context of spiral wound membrane elements are occasionally described as two-dimensional articles, when the context permits. However, it is essential that the flow channel spacer have a thickness and open volume for the movement of fluid between membrane layers.
U.S. Pat. No. 3,386,583 to Merten describes an axially fed membrane element having a continuous membrane. Also taught is a continuous permeate fluid channel sheet, and a continuous feed fluid channel sheet. Manufacture of this design is cumbersome as it requires a complicated jig and the insertion of a position maintainer at the radially proximal end of each membrane envelope fold and a similar position maintainer at the radially distal end of each fold. During manufacture, the position maintainer must be inserted in the jig for each fold th

REFERENCES:
patent: 4137113 (1979-01-01), Kanamaru et al.
patent: 4765893 (1988-08-01), Kohlheb
patent: 4802982 (1989-02-01), Lien
patent: 5073263 (1991-12-01), Fagundes et al.

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