DK144084B - MEDUL FOR USE IN ULTRA-FILTRATION AND PROCEDURE FOR THE PREPARATION OF A PIPE ORGAN USED IN THE MODULE - Google Patents

Description

(19) DENMARK (^)

fjf (12) PUBLICATION WRITING (11) 141 + 084 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 2521/74 (51) IntCI. · B 01 D 31/00 (22) Filing date May 8, 1974 (24) Running day May 8, 1974 (41) Aim. available Nov. 11; 1974 (44) Presented 7- Dec. 1981 (86) International application # - (86) International filing day (85) Continuation day - (62) Master application no -

(30) Priority May 10, 1973 * 358942, US

(71) Applicant UNION CARBIDE CORPORATION, New York, US.

(72) Inventor Olof Conrad Trulson, US: Lawrence Marvin Litz, US.

(74) Associate Engineer Lehmann & Ree.

(54) Module for use in ultra filtration as well as a method for producing a tubular member used in the module.

The invention relates to a module for use in ultrafiltration for concentration and separation of constituents in liquids, which module comprises: (i) at least one inlet opening, (ii) at least one outlet opening, (iii) a permeate collection zone with at least one outlet opening, 33 and (iv) a plurality of axially directed hollow tubular members disposed in this zone close to each other, which 3 members are supported and mounted tightly in the zone so that food liquid entering the module must contact the members; and any component of the liquid which permeates the walls of the organs is collected in the permeate collection zone.

144084 2 In recent years, a number of processes have been described in the literature relating to ultrafiltration techniques. Much of the work in the ultrafiltration field has been done at the Oak Ridge National Laboratories of the United States Atomic Energy Commission, which has conducted in-depth studies of ultrafiltration or cross-flow filtration (sometimes referred to as). The work there primarily comprised high pressure systems (34 - 65 atmospheres or 500 - 950 psi) using porous, tubular carbon or aluminum silicate support structures or a microporous membrane on a stainless steel perforated sleeve.

The researchers at Oak Ridge found that for some aqueous systems, a layer of particles evenly distributed over a porous substrate acts as an effective filter medium that blocks the passage of particles and molecules whose size exceeds the openings between adjacent particles in the porous layer . It was suggested that the particles deposited on the surface of the substrate could be of any material that was inert to solutions in contact with the surface. A variety of materials such as diatomaceous earth, perlite, asbestos fibers, cellulose fibers, dried silica gel and carbon have been used.

In other experiments at Oak Ridge, it was shown that colloidal aqueous oxides can be used as penetration barriers in connection with hyperfiltration by reverse osmosis treatment of solutions, thereby concentrating in water-soluble substances of even lower molecular weight, provided the aqueous solution is pumped over above the surface of the permeable membrane under high pressure (3.4 - 68 atmospheres or 50 - 1000 psi). In this case, the colloids are formed from polyvalent metal salts by heating an aqueous solution of the salt until a cloudy solution is obtained. To form the membrane, small concentrations of the turbid solution (above 10 ppm) are circulated over the support structure at moderate speed and below pressure. This process results in the formation of a thin interface layer (thickness up to 0.05 mm) which serves as an interface between the wastewater solution and the porous substrate. (See, for example, U.S. Patent Nos. 3,413,219, 3,449,245, and 3-537988.) U.S. Patent No. 3-537-988 relates to a process for removing dissolved organic matter from an aqueous solution by conducting the solution over a dynamically established membrane. This dynamic membrane can is established by passing a colloidal solution of aqueous zirconia through a porous substrate or substrate. However, when the membrane is constructed, it must be maintained during use by providing the liquid to be filtered with a content of the membrane-forming material, e.g. aqueous zirconia. In the description of this United States patent, it is column 2, line 43 fn. mentioned that membranes formed from the colloidal aqueous oxides will continue to have retention properties for a day or more, however, withholding being gradually reduced. However, the retention ability can be improved by adding an additive to the liquid to be treated, but this, of course, is itself a disadvantage of these known membranes.

From the specification of US Patent No. 3-442,002, an apparatus for separating fluid substances is known. However, the operation of this apparatus is based on selective passage of gases or liquids through non-porous membranes by permeation or active diffusion. Thus, this apparatus is not an actual ultrafiltration apparatus and, because of its operation, the substance separation produced is a slow and time-consuming process, and furthermore, this apparatus is of course only suitable for separating substance mixtures of very specific types, since this is not an actual mechanical filtration based on the molecular sizes of the substances.

Further, from the specification to US Patent No. 3,022,187, membranes and a process for their preparation are known. The membranes are in the form of slices of a sintered stainless steel porous substrate onto which a layer of submoxic metal oxide particles is deposited. However, due to their geometric shape, these membranes are not suitable for use in an ultrafiltration module based on cross-flow filtration, and because of the porous substrate in combination with the proposed coating, they provide poor and / or slow filtration.

Finally, from U.S. Patent No. 3,462,362, a method of treating an ionic feed solution by reverse osmosis is known. The membranes used for this contain single particles of a polyelectrolyte which are held in place by a high pressure difference between the opposite surfaces of the membrane or by a "bridging" type bond between cationic and anionic polymers. These membranes are stated to be suitable for separating ionically-formed substances, such as salts, from nonionically-constituted substances such as water. Thus, the membranes and process are not suitable for treating liquids such as water containing oil, or chemically stabilized or emulsified oil.

4 144084

Thus, while the prior art encompasses a number of ultrafiltration, filtration apparatus and methods, these are not generally suitable for ultrafiltration, thereby providing a separation and concentration of liquids containing relatively large diameter molecules from relatively small diameter molecules, or for separation of emulsified oil, dirt and various other suspended materials from solutions.

However, this is achieved with the module according to the present invention, which is characterized in that the walls of the tubular members have a pore volume of at least approx. 0.08 cm 2 / g within the pore diameter range of the distribution peak, with the majority of the pores having a diameter of from approx. 0.1 to approx. 2.0 microns, and that the surface of the walls in direct contact with the introduced food liquid has a substantially uniform, continuous, continuous, porous coating of pre-formed aggregate metal oxide particles, the aggregate metal oxide particles having a mean size of less than approx. 5 microns and the coating has a thickness of approx.

0.01 to approx. 10.0 microns without significant penetration of the particles into the walls of the organs.

The module according to the invention is suitable for use in an ultrafiltration apparatus for concentrating and separating ingredients contained in liquids, the apparatus also having means for supplying a food liquid to the module, means for withdrawing a concentrated liquid from the module, and means for withdrawing a liquid. -meat liquid from the permeate collection zone.

The invention also relates to a method for producing a tubular member in the module according to the invention, characterized in that the inner surface of the wall of a tubular member having a pore volume of at least about 20 cm. 0.08 cnr / g within the pore diameter range of the distribution peak, with the majority of the pores having a diameter of from approx. 0.1 to approx. 2.0 microns, is contacted with an aqueous suspension of aggregate metal oxide particles until a coating is formed having a thickness of at least approx. 0.01 to approx. 10.0 microns and a weight of at least approx. 0.16? mg per day cm surface area of the wall.

Another embodiment of the method according to the invention is characterized in that the outer surface of the wall of a tubular member having a pore volume of at least approx. 0.08 cm 2 / g within the pore diameter range of the distribution peak, with the majority of the pores having a diameter of from approx. 0.1 to approx. 2.0 microns, is contacted with an aqueous suspension of aggregated metal oxide 5 1 UQ84 particles until the coating has a thickness of at least approx. 0.01 to approx. 10.0 microns and a weight of at least about .06 mg. cm surface area of the wall.

The invention and the preferred embodiments thereof can best be understood in connection with the accompanying drawing, in which: Fig. 1 shows a form of the ultrafiltration system according to the invention, Fig. 2 is a uncovered view of the multi-tube module for ultrafiltration, Figs. Fig. 7 is a longitudinal cross-sectional view of one of the hollow tubular portions; and Fig. 8 is an enlarged view of a portion of this cross section showing the porous support and metal oxide coating. .

The ultrafiltration system of the invention, soip is v; Lst in FIG. 1, is composed of the ultrafiltration module 10, a tank 12, pumps 14 and 16 and valve control equipment 18, The liquid to be concentrated and separated is pumped from the tank 12 via pipelines 20, 22, 24 and 26 into the ultrafiltration module 10. As shown in the uncovered image of FIG. 2, module 10 is composed of a plurality of tightly packed tubes 32 held at each end by tube holders 34 and 36. The tubes are arranged in the module in such a way that liquid entering the module through the conduit 26 must pass through the pipes. The liquid and the low molecular weight dissolved phases, i.e. small diameter molecules, penetrate through the walls of the tubes and into the chamber 38 and pass out through the tubing 28. The high molecular weight dissolved phases, i.e. large diameter molecules, as well as non-dissolved material, pass out through the conduit 30.

Pig. 3 shows a way of inserting the tubes 32 into the module sleeve 40. The tube holder 42 has a plurality of openings 44 of sufficient size to accommodate the ends of the tubes. O-rings 46 are then placed over the pipe ends and plate 48 is placed over the pipe ends, the sheath 50 is then secured to the pipe holder 42, the O-rings being compressed to form a tight closure.

Figures 4, 5 and 6 show another method of placing the tubes 32 in the module housing. The tube holder 34 has openings through which the tubes 32 can be inserted. The outer side of the tube holder has open diameters larger in diameter than the tubes, thereby providing a recess for a gasket closure 52 which may consist of rubber or rubbery material. The module sheath 56 containing the tubes 32 and provided with a permeate outlet 54 is shown in FIG. 4, with a portion of the end 58 removed to allow the interior to be seen.

FIG. 7 shows a cross-section taken along the axis of one of the hollow tubular portions 32. Feeding fluid enters at position 60, passes through tubular portion 32 and exits at position 62. The low molecular weight dissolved phases penetrate walls 64 of the tubular portion. part and into the penetration zone 66.

FIG. 8 shows a cross section enlarged approx. 2,000 times of a portion of tubular portion 32, which cross section e.g. is taken into position 68. The tubular portion 32, e.g. a carbon tube, consists of bonded carbon particles 70 and has a substantially continuous coating of aggregated metal oxide particles 72. The particles 72 penetrate only partially into the pores 74, which pores are characteristic of the carbon tubes used in this invention. The aggregated metal oxide particles typically penetrate to a depth M of no more than 5.0 microns. The pores with a diameter below approx. 0.05 microns are essentially free of the metal oxide coatings. In operation, a filter cake 76 consisting of dissolved phases of high molecular weight, i.e. large diameter molecules or undissolved particles are formed on the coated surface.

The module of the apparatus can be constructed and assembled in such a way that the metal oxide coating can be either on the inner hollow surface or on the outer surface of the tubular parts. In each case, the coating of metal oxide particles is on the surface of the tubular portion which is in direct contact with the food liquid. For example, if the module. are constructed as shown in FIG. 2, where the food liquid enters through the conduit 26 and exits at the conduit 30, the metal oxide coating is on the hollow inner portion of the tubes. If the coating is on the outer surface of the tubular members, the food liquid would enter through the conduit 28, contact the outer surface of the tubular members and pass out of the module 10 through a conduit not shown in FIG. 2. The permeate which passed through the walls of the tubular sections could then be removed through the pipeline 30.

Of the two module types, the one shown in FIG. 2 because of better hydrodynamic properties compared to the arrangement where the food liquid is in contact with the outer surface of the parts. The feed liquid passes through the inner hollow portion of the tubular member and the permeate collects in the permeate zone and can be withdrawn through the conduit 28.

U4084 7

As mentioned above, the apparatus of this invention is particularly suitable for long-term operation with a high concentration and separation of constituents in liquids. Unlike many of the currently available ultrafiltration units, the apparatus of this invention maintains a high flow level without the need for additives.

The ultrafiltration module according to the invention can be assembled into an apparatus together with means for supplying food liquid and means for collecting and withdrawing a concentrated liquid and a per-meat liquid. The module itself is composed of a plurality of axially directed hollow tubular members disposed within the module's permeate collection zone.

As shown in Fig. 2, the tubular members 32 are aligned in parallel and supported and held in place by tube holders 3 and 36. Although the tubular members can be made of a variety of materials, it is preferred that they are largely of inorganic composition. It has been found that tubular parts consisting of inorganic materials are highly resistant to abrasion and can withstand higher temperatures than those largely composed of organic materials. In practice, it has been found that tubular parts composed of carbon, alumina, aluminum silicate and the like can be used in the apparatus according to the invention.

It is critical for successful practice of the invention that the tubular portions have a well-defined porosity. If the pore diameter is too large, the separation will not be selective and the inner pores may even be blocked by the larger diameter molecules. If the pore diameter is too small, the rate at which liquid passes through to the permeate collection zone will be greatly reduced and the overall efficiency of the apparatus thus diminished.

It has been found that tubular parts which are peculiar to a pore volume of at least approx. 0.08 cm / g at the top of the distribution within the pore diameter range, with the majority of the pores having a diameter between approx. 0.1 and approx. 2.0 microns is ideal for use in the ultrafiltration apparatus. Particularly preferred are tubular portions of carbon in which the majority of the pore diameters are within the above range. Pore size measurements on samples of carbon tubes used in the modules show that they have a sharp peak in the range of 0.10 - 0.50 microns. Pores in this size range make up nearly 50% of the distribution in the tube. The preferred tubular portions are made by a binderaid portion coking process followed by a heat treatment. The carbon tubes used are well known in the art, e.g. those usually 8 U4084 are used for the production of cut-out ball arches for projection apparatus for live images. The carbon tubes serve as an outer casing which is then filled with rare earth graphite and oxides to provide the desired light intensity.

The size of the tubular parts and the length-to-diameter ratio can vary over a wide range. A length-to-diameter ratio of at least 20: 1 is advantageous for many applications.

The particular size chosen will undoubtedly be influenced by the total size of the module as well as the type of fluid and components to be separated. In practice, tubular portions having an inner diameter of from approx. 0.25 cm to approx. 2.5 cm and a wall thickness of approx. 0.08 cm to approx. 0.63 cm and a length of approx. 122 cm has been used with very good results. Tubular parts with an inner diameter of 0.63 cm, a wall thickness of approx. 0.15 and a length of approx.

122 cm is particularly preferred.

In addition to the well-defined porosity of the tubular portions, it has been found that optimum ultrafiltration can be achieved when the inner surface of the porous tubular portions is coated with certain aggregate metal oxide particles as defined below. Use of selected size range and metal oxide coating represents a significant improvement over the prior art in developing a microporous ultrafiltration filter for cross-flow filtration. Based on the use of carbon, alumina, aluminum silicate or other porous tubular parts as support material with the addition of aggregated metal oxide particles, i.e. a microporous metal oxide coating, it has been found that several different industrial process streams and wastewater streams can be treated, thereby separating suspended solids, colloids, oils or high molecular weight polymers by ultrafiltration at rates several times higher than that of the tube alone or the known, previously preferred membrane of aqueous zirconia.

In the present invention, as a coating, aggregate metal oxide particles having a narrow size range of less than ca.

5 microns and roughly between approx. 0.1 and approx. 2.0 microns. The aggregated particles can be further subdivided and classified as fine (less than 0.1 micron), medium (0.1 - 1.0 micron) and coarse (1.0 micron and above). Particularly preferred are aggregated metal oxide particles in which a significant portion, i.e. at least $ 50, has a size of approx. 0.1 to approx.

1.0 micron.

Although commercially available metal oxide powders can be used, in some cases these require long grinding times to reduce the particle size to the proper range. Particularly preferred metal oxide powders which have been found to be ideal for use in this invention are those made by the so-called "precursor process". In this process, a metal compound is first brought into contact with a carbohydrate material, the material ignites so that the carbohydrate material decomposes and is removed and so that conversion of substantially the entire metal compound to brittle agglomerates of the corresponding metal oxide is ensured followed by comminution of the thus formed agglomerates. obtaining the finer microporous aggregate particles used in the invention.

Eg. For example, a supply of the metal oxide powder assembly prepared by the precursor process, such as zirconia, may contain

8-1055 yttrium oxide is ball milled by placing 1500 grams in a 3.8 liter container and adding zirconia balls. The container is then filled approx. 3/4 with deionized water and acidify to a pH of 4 with acetic acid. The contents are then ground for approx. 18 hours.

The particles produced by the precursor process are so small that the settling rate is slow, so that aggregates that have not been completely destroyed during wet ball milling can be separated from the dispersed suspension of released particles by sedimentation, centrifugation or other separation methods. based on particle size or mass. Eg. For example, size splitting can be accomplished by centrifuging a wide distribution of particle sizes to obtain aggregated metal oxide particles substantially within the desired range as described below. Once separated, the released particles remaining in suspension can be conveniently collected by treatments that reduce the surface charge and make the colloidal suspension unstable. Typical treatments are the addition of an acid to lower the pH of the suspension or the addition of a salt with a multivalent anion. The suspensions treated in this way return to the flocculated state and in this form the powder can be separated from the main mass of the suspension medium by filtration or sedimentation.

It has been found that the mean size of the single particles, from which the preferred aggregates of size from 0.1 to 1.0 micron are obtained, is below 1.0 micron, and usually below 0, in microns. The single particles remain undissolved at a magnification of 11,000 times. X-ray powder diffraction analysis shows a final particle size in the range of approx. 0.01 to approx. 0.1 micron.

144084 ίο

A variety of metal oxide particles can be used as the coating of the invention. Eg. the metal in the metal oxide, either alone or in mixtures, may comprise beryllium, magnesium, calcium, aluminum, titanium, strontium, yttrium, lanthanum, zirconium, hafnium, thorium, iron, manganese, silicon and the like. , α-alumina and magnesium-alumina spinel.

If the metal oxide powder used is zirconia, in many cases it is preferred to produce the zirconia powder in stabilized form. Therefore, a compound of yttrium, calcium, magnesium, alkaline earth metal or other known metal forming a stabilizing oxide can be used with the zirconium-containing compound in the preparation of the material. The amount ratio of the zirconium compound to the stabilizing metal compound should be chosen such that the desired type of stabilized zirconia is obtained.

A further and more detailed description of the precursor process for preparing the metal oxide powders used in the present invention is found in the specification of Belgian Patent No. 766,962.

In practice, the metal oxide coating is applied to the tubular portions by allowing an aqueous suspension of the aggregate particles to circulate through the tubes at linear flow rates of from ca. 0.15 m / sec. to 12.2 m / sec. and at pressures of from 2.0 atmospheres to 34 atmospheres (30 to 500 psi). The concentration of aggregated particles in the suspension is typically in the range of from ca. 10 to approx. 100 mg per liter. The suspension is generally maintained at a pH sufficient to maintain a stable suspension of the aggregates. As the water is filtered through the pores of the tubes, the particles are filtered out and cover the pore opening of the substrate with a layer of very fine pores. It is this uniform, continuous, highly porous structure with very fine pores that gives it higher throughput and improved resistance to contamination compared to either pipes alone or pipes coated with less porous materials. For optimum efficiency and throughput, it has been found that the coating should have a thickness of approx. 0.01 to approx. 10.0 microns without penetration into the tubular portion of significance exceeding approx. 5 microns. It is also desirable, but not necessary, to coat the tubular parts at pressures which are at least equal and at flow rates not greater than those which will be used when the module is in operation.

For most applications, the tubular portions are coated with the aggregated metal oxide particles, so as to provide a p. 1.3 mg / cm of the tubular surface.

For some applications, it may be desirable to further apply a second coating on top of the first of fine-grained particles.

1U084 11

For most applications, it has been found that the smallest amount of aggregate metal oxide particles to be used is approx. 0.16 mg / cm. Larger amounts give higher and more stable flux levels.

2

While a metal oxide coating of 1.3 mg per cm in average e.g. is useful, it may be desirable to coat as much as 4.7 mg per day. cm 2.

The coating of the tubular portions with the metal oxides is preferably carried out within a selected pH range. The particular pH range is the region in which the metal oxide particles remain in suspension. When the tubular parts e.g. coated with zireonium dioxide particles, the preferred pH range is from approx. 1 to approx. 5, and preferably from ca. 2 to approx. 3} 5 · Adjustment of pH can be accomplished by the addition of an acid such as acetic acid, oxalic acid, hydrochloric acid and the like. In practice, oxalic acid and hydrochloric acid are preferred as these tend to keep any iron present in solution.

It should be noted that, contrary to the methods previously described, it is not necessary to form a colloid before depositing the metal oxide on the surface of the tubular portion, as described for the aqueous zirconia gel (3,413,219). The metal oxide aggregates are formed in advance and the desired particle size range is separated before the coating step. The coating is essentially a mechanical step in which the metal oxide assemblies penetrate to some extent into the pores of the tubular members and build up the desired coating on the surface. The aggregated metal oxide particles do not fill the pores of the tubular portions so that they become clogged, but "bridge" the pores, allowing small diameter feed stream molecules to pass through at high speed.

As previously mentioned, the ultrafiltration apparatus of the invention can operate effectively at pressures of about 34 atmospheres (500 psi) and below. Of course, various factors such as temperature, pressure, and flow rates will vary according to the particular feed flow. In addition, the current geometric configuration of the interior of the tubular members will also be a factor. Eg. the interior of the parts need not be cylindrical but may be star-shaped, hexagonal, octagonal, saw-toothed or the like.

It has been found that for concentration and separation of certain dissolved phases, optimum results are obtained if the hollow tubular portions containing the metal oxide coating are covered with a further coating such as e.g. the fine quality of the metal oxide powder (less than 0.1 micron) or an aqueous zirconia gel.

Thus, a coating according to the invention is characterized in that it consists of a coating of aggregate metal oxide particles having an average size of from about 20 to about 40 mm. 0.1 to approx. 1.0 micron and a second coating of metal oxide particles having an average particle size of less than ca. 0.1 micron.

According to another embodiment of the coating, the coating consists of a coating of aggregated metal oxide particles having an average particle size of from ca. 0.1 to approx. 1.0 micron and another coating of aqueous zirconia.

Methods for applying aqueous zirconia gel coating are well known in the art, and are e.g. U.S. Patent No. 3 * 537-988.

It should be noted that such coatings are in addition to the metal oxide coating. Attempts to apply the aqueous zirconia gels alone to the tubular portions do not provide the high degree of concentration and separation as in the present invention. Eg. Examples 4 and 5 of this invention are directed to the use of ultrafiltration apparatus one for concentrating polyvinyl alcohol in a textile liquid. As shown in Table V in Example 5, both the metal oxide coated carbon tube and the additional aqueous metal oxide coating tubes gave significantly improved results over the uncoated carbon tube.

As shown in Fig. 8, during operation, initially, a filter cake composed of the larger diameter molecules, as well as of solid and suspended material in the food liquid, will form on the coated tubular portions. When the ultrafiltration apparatus is in operation, the feed stream, such as an aqueous oil emulsion, is applied under pressure over the filter surface at rates sufficiently high to push away most of the accumulated filtered substances. Since this flow is perpendicular to the flow direction of the filtered liquid through the filtration surface, the term "cross flow filtration" is used. Importantly, the flow rate through the tubular portions is such that turbulent conditions are obtained. The liquid should pass through the tubular portions at a linear velocity of at least approx. 0.30 cm / sec. and at a Reynolds number of at least approx. 2000.

Eg. For example, an ultrafiltration apparatus containing a single module of approx. 151 tubular parts (inner diameter 0.64 cm and length 122 cm) process over 11.4 m 2 (3000 gallons) per per day at a pressure of 6.8 atmospheres (100 psi) and a feed stream temperature of approx. 22 ° C.

When two or more modules are used in the same apparatus, or as the number of tubular parts is increased, volumes as large as 13 1Λ408Λ can be tens of thousands of gallons per unit. day and above (10,000 gallons equivalent to 37.9 m 2) are treated effectively.

By usual filtration, the filtered material would build up as a thick filter cake, greatly reducing the filtration rate. Depending on the geometry of the system and the type of material being filtered, the velocities parallel to the filtration surface may be from approx. 0.15 m / sec. to approx. 12.2 m / sec. A particularly significant feature of the present process is that the filter interface is such that dissolved, colloidal or suspended particles of the food liquid in the size range of 10 microns and above to as little as 0.002 microns can be removed at filtration rates through the surface as high as several hundred gallons per . per square foot per day (100 gallons per square meter)

Ύ Oh

dratefoot equals 4.1 no / m) at 6.8 atmospheric pressure (100 psi or less).

While ultrafiltration has been used to remove suspensions, colloids and high molecular weight materials in aqueous solutions, the discovery was unexpected that oil emulsions could be concentrated and separated from the aqueous main phase by ultrafiltration through coated fine-pore tubes. Such oil emulsions are e.g. those used in the manufacture of refrigerants and lubricants for steel and rolling mills or such emulsions as are used in cutting, drawing, punching or other metalworking operations. Further, the types of oil-water-dirt-metal-chip emulsions that result from washing of fabricated metal parts, etc. with detergents, also separated into a concentrated oil-dirt particle solution and a clear filtrate phase containing water plus soluble detergent.

Currently, accumulations of oil, dirt and various other suspended solids in an aqueous system are removed by the addition of acid and / or other chemicals at relatively high temperatures to break the emulsion and separate the oil from the suspension; then the water is placed in large storage containers to remove particulate matter by precipitation, and the remaining soluble constituents are either neutralized or chemically treated otherwise by the addition of acid or alkali and then fed to a wastewater or transported to a suitable discharge or treatment facility. Transportation is relatively expensive and in no case is the water-soluble components of the waste water separated purely for recycling. Furthermore, the cost of treatment with chemicals is considerable, both in terms of materials and work, as well as in terms of treatment equipment. Additional fees for the chemical-containing aqueous phase are often quite high.

In an ever-increasing number of places, such discharges are prohibited by UÅ084 14 pollution control laws. As a result, further treatment of the aqueous phase is required before the water itself can be thinned out.

The ultrafiltration process of the invention can reduce the volume of the oil-dirt aqueous phase by as much as a factor of 5 to 30 or more, depending on the oil content of the starting material. Thus, the volume of material requiring further processing before depletion is greatly reduced. Since the oil level in this concentrate phase can typically further rise to a level of $ 20 to $ 40, which is a sufficiently high level to sustain combustion without further fuel addition, the depletion problem can be greatly simplified by combustion. This also allows the utilization of the bulk of the oil's thermal energy.

The oil-free aqueous phase can be led to a wastewater pipe or recycled back into the process. Reusing the water promotes closed circuit operation, which is highly desirable from a water conservation standpoint. When there are valuable water-soluble substances, such as detergents, which are entrained in the filtrate, an additional operating saving is obtained, avoiding the loss of these materials in the usual wastewater flow.

Another significant advantage obtained by using the method of the invention for the continuous removal of dirt and oil from a metal washer at a paint plant is, for example, that the cleaner washing liquid increases the purity of the subsequent rinse bath and other commonly used pretreatment baths. before painting. As a result, the quality of the paint coating on the cleaner metal blank has greatly improved.

Another embodiment of the present invention is directed to the ultrafiltration module itself and to methods for assembling the tubular members. Of course, although a single tubular part can cause concentration and separation, it is more practical to construct a module with a plurality of tubes. The number of tubular parts used will vary depending on a number of factors. Modules containing as little as 25 or less or up to 1000 or more tubular parts have been manufactured.

As shown in FIG. 2, the tubular members are aligned in parallel and are adjacent to each other. Each tubular member is held in place by tube holders 34 and 36. The tube holders themselves are mounted in the module so as to provide a permeate zone 38 which is blocked from the feed liquid entering through the inlet opening via the pipeline 26. The only liquid that can enter in the permeate zone is that which is filtered through the walls of the tubular portions.

15

1U08A

The outer casing of the module and the tube holders can be made of a variety of materials. Eg. For example, a wide variety of plastics such as polyvinyl chloride and the like or metals such as stainless steel can be used. Few because of the wide variety of liquids that can be treated, and the temperature fluctuations of the feed stream, it is preferable to manufacture the stainless steel module or other material compatible with the food liquid and operating conditions.

As mentioned above, FIG. 3 and 4 are two ways of assembling the tubular parts in the tube holders so that a liquid-tight seal is obtained. In both cases, the ends of the. tubular parts sealed and resilient by a rubber or rubber-like gasket, such as a synthetic rubbery material. However, the gasket may also be metal. Unlike a cemented closure device or other rigid closure device, the assembly method used in connection with this invention provides a kind of "liquid closure" so that fragile pipe parts, e.g. those made of carbon can withstand a certain amount of impact.

The FIG. 3 uses O-rings 46 which are placed over the ends of the tubular members. The plate 48 is then placed over the pipe ends and the O-rings. When the sheath 50 is attached to the end plate 42, the O-rings are compressed and seal and retain the tubular parts in place.

Figures 4-6 show a more preferred mounting of the tubular parts in the ultrafiltration module. As shown in FIG. 6, the end plate 34 contains openings of sufficient diameter to accommodate the tubular members. The surface of the end plate opposite the permeate zone is retracted so that a gasket closure 52 can be placed over the end of the tube and pressed into the recessed area. This seals and holds the tubular parts in place. An advantage of this mounting form over the previous one is that it allows the tubular parts to be very close to one another. For certain applications and taking into account space requirements, it may be advantageous to produce a relatively compact module without sacrificing the desired number of tubular parts.

For most efficient utilization of the ultrafiltration apparatus of the invention, it is often preferred to operate in a closed loop, i.e. that the feed stream after passage through the module, where it becomes slightly more concentrated in terms of larger molecular weight molecules, is recycled back to the module. When the liquid reaches a sufficient concentration, it can then be withdrawn from the system. Various automatic control equipment can be used in removing the concentrate as well as in circulating the feed stream.

m 084 16

While Fig. 1 shows an ultrafiltration apparatus using a single module 10, for some applications it may be desirable to use two or more modules in the same apparatus. In that case, the modules may be arranged in series, i.e. that the concentrate from a first module serves as a feed stream to a second, etc., or in parallel, wherein the same feed stream simultaneously enters all modules. A number of factors may influence which arrangement will provide the best concentration and separation of the components for a particular application.

Due to the excellent properties of the apparatus according to the invention, it is particularly suitable for separating and concentrating ingredients in a wide variety of liquids. As mentioned earlier, a particularly attractive use of the ultrafiltration apparatus of the invention is for concentrating and separating oil-water emulsions. Such emulsions occur in a wide variety of metalworking and metalwashing operations. Prior to the present invention, there was no satisfactory method of effectively concentrating such liquids to minimize waste and recover many of the usable constituents of the liquids. However, the apparatus of the invention has proven to be extremely successful in treating a wide variety of liquids containing emulsified and / or chemically stabilized oil.

As shown in the examples, the ultrafiltration apparatus is also useful for concentrating and separating solutions used in textile processing. Eg. polyvinyl alcohol is easily concentrated and separated from textile treatment solutions with high efficiency.

The apparatus is also useful for the extraction and recirculation of detergents from various types of washing water, such as from car wash, laundry and the like.

It has also been found that the ultrafiltration apparatus of the invention is useful in electrophoretic coating operations. After a painted object e.g. is removed from an electric paint bath, in many cases it is sprayed with water to remove excess extraction. By passing this paint-containing wash water through the apparatus of the invention, solid paint material can be concentrated and returned to the paint bath. The apparatus is also useful for removing excess water-soluble salts or excess solubilizers from the paint bath. As mentioned in Example 6, the rejection of the pigment phase can be as high as 99.95%. In contrast to methods previously described, e.g. in U.S. Patent No. 3,663,399, the penetration rates obtained with the apparatus of this invention are much higher.

144084 17

The apparatus of the invention has further proved useful in the treatment of a variety of food and beverage products.

Eg. For example, the apparatus is useful for concentrating and separating mask liquid in the production of beer. It has also been found useful for the concentration of proteins from cheese whey, clarification of wine vinegar and the like.

In certain applications, such as in desalination of seawater, the ultrafiltration apparatus may be used as an initial treatment to clear the water before passing through a reverse osmosis unit.

It has also been observed that the ultrafiltration apparatus is useful for concentrating and separating blood serum from cattle, egg albumin, enzymes and the like.

Finally, the ultrafiltration apparatus is also suitable for concentrating and separating paper pulp from liquids containing this paper pulp.

The following examples serve to illustrate the invention.

Example 1

An aqueous solution (solution A) containing ca. 2% by weight of foreign substances and soluble oils together with approx. 3% by weight of soluble industrial detergent and sodium hydroxide were circulated through an ultrafiltration module at various pressures and flow rates. The wastewater itself came from the storage tank of an industrial washing machine which is used to clean dirt, metal shavings and oil residues from the metal parts after their manufacture. Various oils are found on the finished parts, including lubricating oils used in the drawing operation, soluble oils from the shaping operation and various cutting oils from the machining operation. The total oil concentration in the feed material was determined by sulfuric acid addition and subsequent separation.

The operating conditions and the results obtained are listed in Table I: 144084 18

Table I

Operating conditions of ultrafiltration system for the treatment of oil-water detergent Solution A

Operating pressure 6.8 atmospheres

Circulation speed 5.5 m / sec.

Filtrate flux 3.7 m3 / m2 per day

Operating temperature 60 ° C

Total operating time 30 hours.

Characteristics of feed stream, filtrate and concentrate Feed stream Filtrate Concentrate pH 12.5 12.5 12.5

Oil content 2% <100 ppm 1S%

Detergent content 3% 3% 3%

As shown in the table, an eight-fold concentration of feed flow was obtained. The filtrate contained less than 100 ppm oil, but still had the same detergent concentration as the feed stream, making it suitable for recycling.

Example 2

Another oil-water detergent solution (solution B) was investigated in which the essential oil component consisted of the soluble oil used in a metal extruding operation; the detergent phase was identified as Amchem 1001. In this case, the feed stream contained ca.

0.4% by volume of oil determined by sulfuric acid separation. Operating conditions and properties of the feed stream, filtrate and concentrate are shown z o in Table II below. Flux values above 4.1 no / m per per day was measured over operating periods over 30 days at different oil concentrations. 55 times concentration was obtained.

144084 19

Table II

Properties of ultrafiltration system for the treatment of oil-water detergent Solution B

Operating pressure 6.8 atmospheres

Circulation speed 4.6 m / sec.

Operating temperature 66 ° C

Filtrate flux 4.6 m 2 / m 2 day

Total operating time 720 hours

Properties of feed stream, filtrate and concentrate Feed stream Filtrate Concentrate pH 9.5 9.5 9.5

Oil content 0.4 <100 ppm 22%

Detergent content 3% 3% 3¾

Example 3 In a third experiment, Texaco Soluble Oil Type C was treated in a single-pipe system with a feed flow concentration of approx. 5%. The data in Table III indicates operating conditions for a 30 hour experiment during which time the oil concentration increased from 5% to 20¾.

Table III

Operating conditions of ultrafiltration system for treating Texaco-C oil / water emulsion

Operating pressure 6.8 atmospheres

Circulation speed 6.7 m / sec.

* z 2

Mean filtrate flux 5.6 no / m day

Average operating temperature 55 C

Total operating time 24 hours

Characteristics of feed stream, filtrate and concentrate Feed stream Filtrate Concentrate Oil content 5% <100 ppm 29¾ 144084 20

Example 4

To illustrate the applicability of the ultrafiltration system to various other industrial waste products, samples of polyvinyl-alcohol-water solutions were treated at concentrations of 1.0 to 4.0 4. The data in Table IV indicate the operating conditions of the system and the properties of feed stream, filtrate and concentrate. The molecular size of the polyvinyl alcohol ranged from 50,000 to 100,000 as used? in a textile treatment bath. In this case, a particulate coating of a zirconia layer was covered with another coating of an aqueous zirconia gel. The aqueous zirconia was prepared by boiling a 0.25 M ZrOClg solution for 30 hours to hydrolyze the oxychloride. For the 9 cm long inner tube 0.64 cm, 12.5 µl of this basic solution was added to 3 liters of distilled water to produce the feed stream which passed through the tube at 6.8 atmospheres for about 1 hour, returned to the reservoir to deposit the aqueous zirconia gel on top of the previous coating. When used, the apparatus provided over 97% retention of the polyvinyl alcohol.

Table IV

Operating conditions for ultrafiltration system with polyvinyl alcohol solution

Operating pressure 6.8 atmospheres

Circulation speed 6.1 m / sec.

• z p

Mean filtrate flux at 1% concentration 28.5 no / m day at 4 $ concentration 0.85 nwm ^ per day

Average operating temperature 86 ° C

Total operating time 112 hours.

Characteristics of feed stream, filtrate and concentrate Feed stream Filtrate Concentrate pH 6.8 6.8 6.8 PVA 1% 0.03 $ 4 $ 21 U608Å

Example 5

Comparison experiments with the polyvinyl alcohol concentration were carried out with uncoated carbon tubes, with carbon tubes coated with a particulate layer and with carbon tubes coated with a particulate layer plus the aqueous zirconia. All measurements were performed at an input pressure of 6.8 atmospheres and a flow rate near 6.1 m / sec. Data in Table V indicate comparability, retention and flux properties for the three experiments and show the greatly enhanced flux obtained with the zirconia particles and the improved retention with sustained high flux when the aqueous layer of zirconia gel was added.

Table V

Comparison of Retention and Flux Properties of Carbon Pipe Permeate, Carbon Pipe Particle Layer Permeate, Carbon Pipe Particle Layer Aqueous Metal Oxide Permeate Using 1% PVA Solution

Flux Back- Temperature -7 2

no / in pr. day holding ° C

_% _

Carbon tubes alone 0.61 0-50 57

Carbon Pipe Particle Layer 4.1 63-66 87

Carbon tube particle layer aqueous metal oxide layer 4.1 97 ~ 99 8l

Example 6

The ultrafiltration apparatus of this invention was used to concentrate a primer paint from an electro-application system.

3

A porous carbon tube with a pore volume of approx. 0.2 g per and most of the pores in the diameter range from 0.1 to 1.0 microns as determined by Hg porosimetry were coated at 6 mg / ml. particles precursor ZrC 2 particles, sorted by centrifugation to have a size in the range of 0.1 to 1.0 micron. The coating was carried out by adding ZrC> 2 to ca. 3 l of acidified water and circulation of the water through the interior of the tube at 6.8 atmospheres for 1 hour, while the water penetrating through the tube wall was returned to the circulating feed stream. The tube was then inserted into a circulation system in which a 7 ½% solids solution of an electro-applied paint, Porbes 2000, was passed through the tube at 6.8 atmospheres and 27 ° C and at a linear flow rate of from 4.5 m / sec. to 7s5 m / sec. Over a period of 214 hours, the permeation rate remained between 3> 5 and 4.1 m / m. day. In other experiments with this paint and this tube, which stretched for another 412 hours, the flux kept between 2.0 and 2.6 no / m 2. day. The retention of the pigment phase was 99> 95% 3 and of the ionic constituents $ 48.8. Typical penetration rates for ultrafiltration systems of the film type with this type of paint are from 0.4l to 1.2 clock / m day.

Example 7 In another example in which another type of high porosity and high surface area powder was used as a coating, a slurry of γ-alumina having a size in approximately the same range as the precursor zirconia, i.e. from 0.1 to 1.0 micron. The carbon tube was of the same type as in the previous example. Its flux at 3 2 o 6.8 atmospheres with pure water was above 16.3 no / no per day. day at 43 ° C. With 3 2 applied pre-coating it dropped to 11.4 m / m. day at an operating temperature of 71 ° C. This tube was used to treat a sample of the black liquid from wood pulp degradation. Flux of the order of 2.9 to 3j3 m / m day was achieved with color retention above 90% and approx. 30% retention of the ionic constituents.

Example 8 In another experiment with the black liquid from the paper mill, a carbon tube as above was first coated with the particulate zireonium dioxide and then with the aqueous zirconium dioxide from the ZrOCl2 solution as set forth in Example 4. After treatment of the black liquid overnight at 6.8 atmospheres and 60 ° C, the penetration rate was 3.3 no. day with over 90% retention of color. The feed stream had a conductivity of 32,000 mho, while the permeate had a conductivity of approx. 17,000 mho, which shows an ionic retention of the order of 47%.

Example 9

A comparison was made with a number of carbon and aluminum oxide tubes to show the wide variation in properties associated with pore diameter, pore volume and air ™ and water permeability.

As mentioned earlier, tubular parts having a pore diameter of from approx. 0.1 to approx. 2.0 microns, such as the samples with the numbers 1 - 7 in Table VI, have been found to provide optimal concentration and separation of constituents from liquids.

The tubular portions having pore diameters generally greater than ca. 2 microns (the samples with numbers 8-15) tended to clog the pores in depth with the metal oxide particles and the ultrafiltered material of the retained product, giving undesirably low penetration rates. When most of the pore volume further had pore diameters less than ca. 0.1 micron, the water flow rate in the uncoated tube was too low and therefore the permeation rate was unacceptably low. In contrast, the samples with numbers 1 - 7 and a pore volume at the distribution peak of ca. 0.8 cm per grams or more in the pore diameter range substantially from about. 0.1 to 2.0 microns very good results. Such earbon tubes can also be known to have a density of less than ca. 1.60 grams per cm ^.

Sample # 7 was a useful tubular member composed of alumina, while the others were composed of carbon.

All measurements were performed using standard pore volume, pore diameter, air and water flow rates, and bulk density techniques.

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Example 10

Ultrafiltration apparatus of this invention was also used to concentrate and separate the protein fraction in cottage cheese whey from the main mass of water, lactose and dissolved salts. Porous carbon nanotubes with pore volumes in the aforementioned preferred range were coated with a precursor magnesium-aluminum spinel in a manner similar to that described in Example 6. A feed stream solution with 90% of the liquid phase extracted was passed through the apparatus at 49 ° C for 20 hours and substantially all the protein was retained in the concentrate. The penetration rate at the end of the experiment was 2.4 m 2 / m day. The tubes were purged with distilled water and a new feed stream solution passed through the apparatus. After 6.5 hours of operation, the penetration rate dropped from 2.1 to 1.3 no / m per minute. day. After washing with Tergitol 15-S-5, the rate of penetration of the feed stream solution returned to 2.3 no. day. The tubular portions were then purified with Tergitol and purified with steam at 1.5 ata to sterilize the tubes and remove particulate matter.

A new feed stream solution was introduced to the apparatus, and the penetration rate was initially 2.6 no / m 2. day. After 2 to 3 2 months of continuous operation, the penetration rate was 2.1 no.

3 2 days, and after 24 hours 1.5 m / m per day. day. It was therefore clear that the tubular part and the metal oxide coating could be purified and steam sterilized to bring the performance back to a high level.

Although the invention has been illustrated by the foregoing examples, it should not be construed as being limited to the materials used herein, but rather the invention relates to the area described above. Various changes and embodiments may be made without departing from the spirit of the invention and the scope thereof.

Claims (2)

26 144084 Pat e n t k r a v. A module for use in ultrafiltration for concentrating and separating constituents in liquids, comprising: (i) at least one inlet opening (26), (ii) at least one outlet opening (30), (iii) a permeate collection zone (38 , 66) having at least one outlet opening (28), and (iv) a plurality of axially directed hollow tubular members (32) disposed in this zone close to each other, which members are supported and mounted tightly in the zone so that food liquid entering the module must contact the means, and any component of the liquid which permeates the walls (64) is collected in the permeate collection zone (38,66), characterized in that the walls (64) of the tubular members (32) ) has a pore volume of at least approx. 0.08 cnrVg within the pore diameter range of the distribution peak, with the majority of the pores having a diameter of from approx. 0.1 to approx. 2.0 microns, and that the surface of the walls (64) which is in direct contact with the introduced liquid has a substantially uniform, continuous, porous coating (72) of previously formed aggregate metal oxide particles, wherein the aggregated metal oxide particles have a mean size of less than about 5 microns, and the coating (72) has a thickness of approx. 0.01 to approx. 10 microns without significant penetration of the particles into the walls (64) of the members (32). A method of manufacturing a tubular member (32) in the module according to claim 1, characterized in that the inner surface of the wall (64) of a tubular member (32) having a pore volume of at least approx. 0.08 cm 2 / g within the pore diameter range of the distribution peak, with the majority of the pores having a diameter of from ca. 0.1 to approx. 2.0 microns, is contacted with an aqueous suspension of aggregate metal oxide particles until a coating is formed having a thickness of at least approx. 0.01 to approx. 10.0 microns and a weight of at least approx. 0.16 mg per cm surface area of the wall.