Porous earthenware supporting members for reverse osmosis membranes, process of manufacture and apparatus using same

Claim 2

A POROUS EATHENWARE SUPPORTING MEMBER FOR REVERSE OSMOSIS MEMBRANES COMPRISING AN ELONGATED CYLINDRICAL EARTHENWARE BODY, A CYLINDRICAL LONGITUDINAL INNER BORE ALONG THE AXIS OF SAID BODY AND CONCENTRICAL WITH THE OUTER SURFACE TEREOF, SAID CYLINDRICAL BODY HAING FLAT ENDS SAID CONCENTRICAL BORE BEING OPEN AT BOTH SAID FLAT ENDS AND COMPRISING AN OUTWARDLY FLARING TAPER AT EACH OF SAID ENDS, SAID CYLINDRICAL BODY COMPRISING A POROUS EARTHENWARE MATERIAL WHICH IS A CALCINED CLAYED HIGH-PLASTIC-WHEN-WET MATERIAL OF THE MONTMORILLONITE TYPE AND HAVING THE CONDENSED FORMULA "A12 SI40010(OH)2," SAID CALCINED EARTHENWARE MATERIAL HAVING FULLY INTERCONNECTED PORES THROUGHOUT SAID BODY AND OF A SIZE NOT LARGER THAN 1 MICRON IN THEIR LARGEST DIMENSION, SO AS TO PROVIDE FOR THE FREE LIQUID INTERCOMMUNICATION BETWEN THE SAID BORE AND THE OUTER SURFACE OF SAID BODY WITHOUT APPRECIABLE PRESSURE DROP THERETHROUGH, SAID CYLINDRICAL EARTHENWARE BODY HAVING A TENSILE STRENGTH SUFFICIENT TO WITHSTAND RADIAL OUTWARD PRESSURE APPLIED ON THE WALL OF SAID BORE OF UP TO ABOUT 100 KG/CM2, WHEREBY A REVERSE OSMOSIS MEMBRANE CAN BE EVENLY ADAPTED TO SAID INNER BORE FOR EFFECTING AN OUTWARD HIGH PRESSURE FLOW OF A LIQUID TO BE OSMOTICALLY FILTRATED.

Claim 3

A process for manufacturing a porous earthenware supporting member for reverse osmosis membranes which comprises the steps of: a. comminuting a clayey material of the montmorillonite type and having the formula ''''Al2Si4O10(OH)2'''' to a very fine particle size of less than 1 nanometer; b. admixing the finely divided clayey material with a finely divided volatile material which will completely volatilize at a temperature of over 1,000*C. and having a particle size of under 1 micron; c. adding a suitable amount of water to said mixture so as to obtain a thick mud or paste; d. vigorously kneading the thus formed paste to thoroughly homogenize the same; e. continuing the kneading operation while adding more water to maintain a proper fluidity in the paste; f. powdering the paste to a small particle size a applying a vacuum thereto in order to expel any trace of air contained therewithin; g. extruding the deaerated paste to from a green elongated cylindrical member or tube having a cylindrical inner bore open at both ends thereof; h. drying the extruded green tube to a moisture content of not more than about 0.5% by weight; and i. calcining the dried tube at a high temperature sufficient to cure the earthenware material and to completely volatilize said volatile material previously added in order to leave a very fine and dense intercommunicated pore structure throughout the body of the tube.

Claim 4

A process for manufacturing a porous earthenware supporting member for reverse osmosis membranes which comprises the steps of: a. comminuting a clayey material of the montmorillonite type and having the formula ''''Al2Si4O10(OH)2'''' to a very fine particle size of less than 1 nanometer; b. admixing the finely divided clayey material with a finely divided volatile material which will completely volatilize at a temperature of over 1,000*C. and having a particle size of under 1 micron; c. adding a suitable amount of water to said mixture so as to obtain a thick mud or paste; d. vigorously kneading the thus formed paste to thoroughly homogenize the same; e. continuing the kneading operation while adding more water to maintain a proper fluidity in the paste; f. powdering the paste to a small particle size a applying a vacuum thereto in order to expel any trace of air contained therewithin; g. extruding the deaerated paste to from a green elongated cylindrical member or tube having a cylindrical inner bore open at both ends thereof; h. drying the extruded green tube to a moisture content of not more than about 0.5% by weight; and i. calcining the dried tube at a high temperature sufficient to cure the earthenware material and to completely volatilize said volatile material previously added in order to leave a very fine and dense intercommunicated pore structure throughout the body of the tube.

Claim 5

A process as claimed in claim 2 wherein said finely divided volatile material is a polysaccharide having a particle size of under 1 micron in its largest particle dimension.

Claim 6

A process as claimed in claim 3 wherein said polisaccharide is wheat flour.

Claim 7

A process as claim in claim 3 wherein said drying step is carried out stepwise and comprises the steps of: a. predrying the extruded tube with warm air at a temperature of from 30* to 40*C., preferably 35*C. during a period of time of from 4 to 8 hours, preferably 6 hours in order to reduce the moisture contEnt to between 8 and 12%, preferably about 10% by weight; b. drying the predried tube at a temperature of from about 70* to 180*C., preferably 150*C. for a period of time of from about 4 to 10 hours, preferably 6 hours, to reduce the moisture content to between about 1 and 3%, preferably about 2% by weight; and c. thereafter increasing the drying temperature up to about 300* to 400*C., preferably about 350*C. for one additional hour in order to reduce the moisture content to less than about 0.5% by weight.

Claim 8

A process as claimed in claim 2 wherein the dried tube is calcined at a temperature of from about 1,000* to 1,050*C., preferably about 1,020*C. for a period of time of from about 4 to 8 hours, preferably about 6 hours in order to reduce the moisture content to 0.0% and to completely volatilize said volatile material.

Claim 9

A process as claimed in claim 2 wherein said volatile material is present in the extruded green tube in a proportion of from 5% to 15%, preferably about 10%, by weight.

Claim 10

A reverse osmotic filtration apparatus comprising a plurality of reverse osmosis assemblies each comprising a porous supporting tube made of an earthenware material which is a calcined clayey highly-plastic-when-wet material of the montmorillonite type and having the condensed formula ''''Al2Si4O10(OH)2'''', said supporting tube having flat ends and a cylindrical inner bore open at both said ends with each said end being provided with a flaring taper as a continuation of the surface of said bore, said tube having fully intercommunicated pores of a size not larger than 1 micron and a tensile strength sufficient to withstand radial outward pressures of up to about 100 Kg/cm2, and a cylindrical reverse osmosis membrane bonded to the surface of said inner bore by means of an adhesive, said membrane being flared at its ends to conform to the end tapers of the porous tube and being evenly supported throughout the surface of said inner bore end tapers; said plurality of reverse osmosis assemblies being arranged as a tube bundle; a discharge header having a perforate plate arranged to receive one of the ends of said tube bundle and bonded thereto by means of said adhesive; a feeding header having a perforate plate arranged to receive the other ends of said tube bundle and bonded thereto by means of said adhesive; said feeding header, tube bundle and discharge header forming a high pressure leak-proof flow-path; an inlet provided in said feeding header; an outlet provided in said discharge header; pressure control valve means in said outlet; and liquid collecting means arranged to collect the liquid flowing through said reverse osmosis assemblies.

Claim 11

A reverse osmotic filtration apparatus comprising a plurality of reverse osmosis assemblies each comprising a porous supporting tube made of an earthenware material which is a calcined clayey highly-plastic-when-wet material of the montmorillonite type and having the condensed formula ''''Al2Si4O10(OH)2'''', said supporting tube having flat ends and a cylindrical inner bore open at both said ends with each said end being provided with a flaring taper as a continuation of the surface of said bore, said tube having fully intercommunicated pores of a size not larger than 1 micron and a tensile strength sufficient to withstand radial outward pressures of up to about 100 Kg/cm2, and a cylindrical reverse osmosis membrane bonded to the surface of said inner bore by means of an adhesive, said membrane being flared at its ends to conform to the end tapers of the porous tube and being evenly supported throughout the surface of said inner bore end tapers; said plurality of reverse osmosis assemblies being arranged as a tube bundle; a discharge header having a perforate plate arranged to receive one of the ends of said tube bundle and bonded thereto by means of said adhesive; a feeding header having a perforate plate arranged to receive the other ends of said tube bundle and bonded thereto by means of said adhesive; said feeding header, tube bundle and discharge header forming a high pressure leak-proof flow-path; an inlet provided in said feeding header; an outlet provided in said discharge header; pressure control valve means in said outlet; and liquid collecting means arranged to collect the liquid flowing through said reverse osmosis assemblies.

Claim 12

A reverse osmotic filtration apparatus as claimed in claim 8 wherein said reverse osmosis membranes comprise elongated hollow cylinders of cellulose acetate which are bonded to the surface of said inner bores of the said supporting tubes and tapers thereof by means of an epoxy resin adhesive.