Patent GB-1113630-A (GB)
Title: Improved method and apparatus for use in the reverse osmotic separation of liquid solvents from liquid feed solutions
IPC: B01D61/08
Filed: 1966-03-22
Abstract: 1,113,630. Membrane diffusion apparatus GENERAL DYNAMICS CORPORATION. 11 March, 1966 [22 March, 1965; 25 Feb., 1966]. No. 10763/66. Headings BIL and BIX. In an apparatus for the separation of liquids and gases by diffusion through semi-permeable membranes, several "sandwiches" each comprising at least one sheet of semi-permeable membrane and a sheet of a porous backing material, which provides a passageway for flow in, the plane of the backing material are spirally wound round a hollow central mandrel, sheets of a separator material being provided to separate the semi-permeable membranes of adjacent spirally wound sandwiches and to ensure that the feed fluid passes through the membrane before contacting the porous backing material. To central hollow mandrel 26 (see Fig. 2) having slots 60 therein are attached sheets 38a-d membrane, and 34a-d of porous backing material with sheets 44a-d of separator material in the folds of the memtrane sheets. The whole is spirally wound as in Fig. 3 (not shown) and the edges (52) and (53) of the membrane sealed to the backing material to preclude access of the fluid mixture to be separated to the backing material. Instead of having slots as shown in Figs. 2 and 3, the mandrel may be constructed from two or more parts. In Fig. 6 (not shown), the mandrel (126) is constructed from arcuate parts (142) to which are attached sheets of separator material (144), and between which pass sandwiches of membrane (138) and porous backing material (134a-d). In Fig. 7 (not shown) the mandrel (226) is constructed from two arcuate parts (242), to each of which is attached a sandwich of membrane (238) and separator material (244), and between which passes a pair of sheets of porous backing material 234 which are divided outside the mandrel in both directions by sandwiches of membrane (238) and separator material (234a-d). In a further embodiment (Fig. 9, not shown), the mandrel is a composite of sections (342) each having axial passages (325) and communicating with the backing material through holes (347). Between the sections pass sandwiches of porous backing material (334), membrane (338) and separator material (344). Such a system may be made as shown in Fig. 8 (not shown), in which the layers on the sandwich are withdrawn continuously from supply rolls, to form a five-layer sandwich (358) whose edges have been sealed with adhesive at (372) (the separator material not being so sealed), and extended into leaves by pulley system (374-379). The mandrel sections (342) are then inserted between the leaves. In another embodiment (Fig. 12, not shown), the mandrel comprises a solid core having cavities around the periphery into which fit inserts having axial passageways therein which passages are connected to the surfaces of the inserts by passages (447). Surrounding the inserts are sandwiches of porous backing material (434) and membrane (438), while successive sandwiches are separated by separator material (444). There may be one or more such inserts. The assembled module of membranes, backing material, separators and mandrel is used in a fluid-tight vessel (18) (Fig. 1, not shown) having an inlet (74) for the mixture to be separated, an outlet (76) for waste mixture, and an outlet (94) in communication with the mandrel for the permeated component. 0-ring (82) prevents the passage of the mixture along the outside of the module. The mandrel has a cap (64) at the top. The fluid mixture passes down the unit along the separator material. The permeated component passes into the backing material and thence into the mandrel. The apparatus may be used for the desalination of salt water or the concentration of aqueous liquids such as fruit juices by reverse osmosis using any suitable osmotic membrane, or for the separation of gaseous mixtures when the membrane is suitably cellulose acetate. The backing material should have high porosity but sufficient strength to withstand the pressures used. Specified materials include graphite cloth, and materials made by binding silicon carbide grit to a sheet of plastic felt, and felts made from glass fibres may be used at pressures above 500 psi, while various synthetic fibrous materials such as nylon, polyester, rayon, rayon viscose, and acrylics may be used at lower pressures. The separator material need not resist such high pressures, and woven polyethylene may for example be used for this purpose.