CA1178542A - Method and apparatus for oil-water separation by coalescence - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

A method and apparatus for oil-water separation by coalescence. First of all, a coalescing element is obtained by forming a coalescing layer on a porous material. This layer is of water-insoluble hydrousgel. The thus obtained coalescing element has oil-resisting and repelling properties as well as water transmitting and absorbing properties. When oil-contaminated water is passed through the coalescing element, oil matter contained in the water coalesces on the element surface. The invention is characterized by changing the direction of the flow of oil-contaminated water passing through the coalescing element, and thus preventing said element from being clogged.

Description

11~7~

BACKGROUND OF TH~ INVENTION
This invention is related to the method and deYice for oil water separation by ~oalescing the oil-particles toseparate oil effectively from such oil-con~aminated water including finely divided and scatteredoil or oil in an emulsified state.
Conventional methods for separating oil from oil-contaminated water include a gravity separation method, filtration method, adsorption method, cohesion disposition method, air floating method, microbiological process, electrolytic method, physical chemistry method and a coalescing method.
The gravity -separating method can be applicable ~or oil granules, and is unsuitable for the separation of finely divided oil while the filtration method easily causes clogging, and requires large-sized equipment for the back flushing process which does still encounter difEiculties in complete prevention of such clo~ging. The air floating method also requires a large system and makes it impossible to separate finely divided oil. The micro-biological method requires large-sized equlpment and is timeconsuming, and the electrolytic or physical chemistry method is accompanied by secondary processing, thus offering problems in connection with the size of installation involved and the procedures of processing. Further, the coalescing--method now available is an ideal method;
which, however, cannot be applied for the range of emulsion type particles of a dimension smaller than 10~ except for precision filtration or ultrafiltration. The ultrafiltration can only be used for specific cases, because the equipment is large and expensive and the running cost is also high.

- 2 -On the other hand, an adsorbent, depending on its lipophlic nature, requires a high C05t and a great deal of manpower for replacing it at a saturating point due to its adsorp-tion limit being a major drawback due to impediment of oil film in the case of high oil concentration and high viscosity oil. The method of using an adsorbent for granulation of smaller than 1OJU oil particle matters i5 impractical, and therefore this method is not adequate for the separation of emulsified materials. No practical small-sized equipment for economically performing separation-by-granulation in the ran~e of oil matters with smaller than 10 ,u particles is available at the present time.
SUMMARY OF THE INVENTION
The present invention is based upon recognition of this difficulties, and extensive studies have resulted in a method and apparatus to efficiently separate high concentration and/or high yiscous oil matters or emulsified oil matters by forming a specific layer having an oil water separation function and consisting mainly of a water insoluble hydrousgel layer having an oil-resisting and oil-repeling function as well as water-permeating and water-absorbing functions on the surface part of a porous material and/or the surface part of a fluid passage and using the element thus formed with this material. The inve~tion is based on the idea of using the specific coalescinq element through which oil holding water is passed, alternatively changing the direc-tion of material flow, and adding structures which may

- 3 -ll~,t~5(~

suit diversified conditions such as high concentration or high viscosity oil or emulsified oil, to allow coalescing of oil drops in the state of smaller than 10 ~ particles, and thus offer a novel means of oil water separation.
The invention attains a new field of removing oil matters, of the granules having a particle size of smaller than 10 ~, which had been desired by society for a long period, and is the development in the field in which numerous research and developments project have been performed without success, and thus is of great significance in that it will enable one to cope with the requirement of 15 PPM which is required as the performance of marine use of an onboard oil water separator based on the Sea Pollution Prevention Act in accordance with the IMCO Convention.
The present invention is concerned with a method of oil-water separation by coalescence comprising the steps of:
- forming a coalescing layer having oil-resisting and repelling properties as well as water transmitting and absorbing properties on at least one surface of a porous material by forming thereon a water-insoluble hydrousgel layer while maintaining a porous nature of the material to obtain coalescing element; and - subjecting said coalescing element to a flow of an oil-contaminated water to coalesce the oil matter contained therein on the coalescing element, said oil-contaminated water passing through the coalescing element alternately from each side thereof to the other.
In the coalescing process of the present invention, an oil-water separating element consisting of a specific porous materi~l is used. It is important that a water-insoluble hydrousgel layer is formed on at least one of the porous material surfaces to come in contact with oil-containing

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( 117854~

water and/or to the liquid passage surface. For example, various types of synthetic fiber, inorganic fiber, natural fiber, natural pulp, synthetic pulp, etc., are used to form a porous material, on which a specific water insoluble hydrousgel layer is formed as a granulation layer.
The types of water insoluble hydrousgel or its means of formation are not specifically limited, and can be selected and exemplified in a ~ider range. For example 1~'78S4~

as the means of forming hydrousgel, the following are 1) A method in which an aqueous solution of a mixture of a water soluble monomer such as acrylamide, acrylic calcium or acrylic soda.with methylene bisacrylamide or N-methylolacrylamide, added with a polymerization catalyst such as ammQnium persulfate or persulfate soda, potassium persulfate, hydrogen per oxide and a condensation catalyst such as ammonium chloride or mono ammonium phosphate, is prepared, and such a solution is adhered to the porous sheet by means of immersion, painting, spraying, etc., and is then dried at a temperature of about 80 - 110C
to effect polycondensation, thereby obtaining a water-insoluble hydrousgel layer; (2) a method comprising the steps of applying an aqueous solution of a material having a plus (+) ion charge (.compounds having a cation charge such as pyridine or quatenary ammonium group) on a porous sheet, and applying an aqueous solution of a material having a negative (-) charge (compounds having an anion charge such as carboxyl group or sulfone group) on the sheet, whereby such materials are ionically coupled to each other at the surface or in the interial of sheet to form a so-called ion complex; (3~ a method in which a gel compound is obtained by the coupling reaction of a water soluble polymeric substance such as carboxymethyl cellulose, polyphosphate, polyphosphoric acid salt, polyacrylic soda with a polyvalent metallic salt such as magnesium sulfate or calcium chloride, i.e.
by previously applying an aqueous solution of polyvalent 1;1'7~

metallic salt on a porous sheet by way of immersion, coating, spraying, etc., then adding an aqueous solution of the above stated water soluble polymetric compound capable of being crosslinked with a metal, followed by intermediary action of polyYalent metallic ions; (4) a method for making natural or synthetic hydrophilic polymeric sub-stance insoluble without losing its water absorbing characteristics, i.e. wherein a porous sheet is pre~iously applied with a crosslin~er such as chrome alum, potash alum, formalin, zinc-chloride, boric acid, magnesium chloride, etc., and a gel compound is formed through a chemical crosslinking reaction by adding a gelatinizer such as gelatin, polyvinyl alcohol, alginic acid, mannan, or cellulose compound; and (5) a method of utilizing a material which absorbs water and swells to form a water insoluble hydrousgel, for example, a method of applying a crosslinked polyethylene oxide (soluble in an organic solvent) to a porous sheet by way of immersion, coating, or spraying or a method of adding lower-substituted carboxymethylated cellulose or polyvinyl fiber by mix spinning or mix weaving.
In the present inYentiOn, the layer which is insoluble in water and capable of absorbing water as mentioned above is applied on the surface of a porous sheet and/or the surface of a liquid passage to come in contact with oil-containing water; however, of importance is that there is no lowering of the porosity of the porous sheet filter after formation of the water-absorbing gel layer. In the selection of one or a mixture of filter materials (having a sufficient porosity), the porosity must be taken into account. When llt7~

the amount of water transmitted is too large, the efficiency of oil-water separation drsps with increases in the amount of water leached out. ~hen the amount of water transmitted is too small, on the other hand, the rate of oil-water separation drops sharply.
In the present invention it is desirable to provide a further process for enhancing and maintaining the effect of the oil separation function such as an oil-repelling function, oil-collecting $unction, granulating ability for oil drops, as well as ~orming the water-absorbing gel.
For example, a lipophilic agent such as a fluorine compound or chrome fluorine compound, lipophilic agent or oil collecting agent such as stearic acid compound, silicone base compound, wax compound, surface tension-reducing agent or oil collecting agent such as a higher alkyl alcohol, silicone alkylene oxide or fluorine surfactant are added t:o the water insoluble hydrousgel layer.
Alternatively the porous sheet will be treated with such an agent by coating, immersing or spraying before or after forming the water absorbing gel. The porous sheet may have a lipophilic portion formed with the water absorbing gel layer. For example, an oil-separating effect by oil collection, growth and separation can be improved by construc-ting a filter material by means of mixed making or mixed spinning of polyolefin fiber or pulp, synthetic fiber of glass fiber.
In this invention any material having characteristics sufficient for use as a filter, i.e. material having 1~ 5~

water permeability, water resistance, pressure resistance and durability, can be widely used as the porous sheet without any restriction. For example, board, non-wo~en fabric, paper or foam seet can be used. Non-woven materials such as paper or non-woven fabric made mainly of cellulose fiber such as cotton, rayon or acetyl cellulose are used after being given the characteristics of water resistance, pressure resistance, durability, etc., by reinforcing treatment such as described in the tJapanese Patent No. 659628. With a porous sheet made of woven fabric such as fi~ter cloth, the aforesaid reinforcement can be omitted as the material itself has characteristics required for filtering, such as water resistance, pressure resistance;
however, the reinforcement process is preferably applied.
Use may be made of other methods such as those comprising the steps of making a non-woven porous sheet by forming a mixture of heat melting synthetic pulp (polyolefin, nylon, polystyrene, etc.), and applying synthetic pulp thereto by a heating process, or applying a crosslinking compound such as urea - formalin condensate, melamine -formalin condensate, epichlorohydrin compound, methylol group containing compound, divinyl sulfone compound, etc., to ~he porous sheet by coating, immersing, spraying, etc., so that the filter function will not be lost.
On the other hand, the porous sheet of the present invention can be made of synthetic fiber material such as polyethylene, polypropylene, phenoric resin thread, polyester, polyamide or of inorganic fibers such as glass fiber, ceramic fiber, asbestos, or of a composite of such various fiber mixtures.

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1~7~54~

In a preferred e~bodiment of the invention, use is made of a fixing process in order that specific water absorbing gel layer will not separate from the porous sheet.
For example, this process is implemented by using a cation fixing asent such as polyethylene imine, epichlorhydrin polyamide, dicianidiamido - formalin condensate, or an anion fixing agent such as urea - formalin condensate, melamine - formalin condensate in dependence upon the type of the porous sheet, and applying it on the porous sheet by way of coating, immersing, spraying before and after formation of the gel layer or impregnating it into the gel layer.
The element for the embodiment of the present invention is advantageously of small size. For example, the porous materials may simply be arranged in multistages. However, it is most preferable to make structures having a number of small passages formed by corrugated carboard flutes or similar structure of the porous material.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better unaerstood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
FIG. 1 is a general Yiew of the oil holding water processing system in one embodiment of the method of the present invention;
FIG. 2 is a sectional side view of the suction port equipment in the system;
FIG. 3 is a sectional side view of a first example of an element;

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FIG. 4 is a section~l plan o~ FIG. 3, FIG. 5 is a perspective view of a second example of the element used in this invention;
FIG. 6 is a plan view illustrating one end of the ele-ment shown in FIG. 5;
FIG. 7 is a plan view of the element of FIG. 5explaining the condition of oil containing water-permeating the element;
FIG. 8 is a sectional side Yiew indicating another embodiment of the element;
FIG. 9 is a schematic drawing indicating another embodiment of implementation of the present invention;
FIGS. lQ(a), (b) and (c) are views explaining the process of ~ranulation to form a larger lump of oil in the oil containing water through the element.
FIG. 11 shows a further embodiment of the present inven-tion;
- FIG. 12 shows one example of the element used in the embodiment of FIG. 11;
FIG. 13 is a side view of a conventional oil-water separator;
FIGS. 14 - 16 are side Yiews of oil-water separators used in the apparatus of the invention;
FIG. 17 shows a still further embodiment of the in~ention;
FIG. 18 is a side view of the element used in the embodi-ment of FIG. li;
FIG. 19 shows a still further embodiment of the invention;
FIG. 20 is a side view of the element used in the embodi-ment of FIG. 19; and FIG. 21 is a plan view illustrating one end of the element of FIG. 20.

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~ESCRIPTIQN O~ THE PREFERRED EMBODIMENTS
-FIG. 1 is a general outline of the embodiment of this invention, in which numeral 101 is a crude water tank to store oil7contaminated water. ~~ne oil-con~nated water 102 is taken out through a suction port equipment 103.
The suction port equipment 103 is constructed as shown in FIG. 2, by which outer cylinder 105 is joined with take-out tube 104 to the bottom and fixed at an appropriate place below the liquid level in the crude water tank 101, inside this outer cylinder 105, is a weir cylinder 107 having a float 106 is inserted to move freely and vertically such that the brim of the weir cylinder is positioned slightly below the liquid level. The weir cylinder 107 provides communication with the take-out tube lQ4. This brim of the weir cylinder 107 may be formed so as to be flat, but uneveness 108 of a saw edge type or notch type is preferable. The suction port e~uipment 103 enables automatic absorption of the high oil concentration part at the surface of the oil containing water 102 in the crude zo water tank 101, and is constructed to allow oil contain water 102 to flow in from the upper end of the weir cylinder 107 which moves in accordance with changes of the height of the liquid surface by way of the function of a float.
The purpose of suction port equipment 103 is to move the suction port in accordance with the change of the fluid level so that the oil~con i nated water will be continuously sucked in from the high oil concentrated surface part, as the fluid level of the crude water tank varies about 200 to 300 mm up and down when items to be washed are put into or removed from the crude watex tank 101.

The take-out tube 104 of the suction port equipment 103 passes through pipe line 109 outside the crude water tank 101 and is connected to a strainer 110. The strainer is mainly provided to remo~e foreign elements in the oil-contaminated water and the strainer 110 is selected fromconventional known products.
The oil-contaminated water from the strainer 110 passes through a pipe 111, a pump 112 and a pipe 113 and enters into a firstflotation separation tank 144. High concentration oil and high viscous oil are removed here.
As for the firstflotation separation tank, are providing as high a coalescent effect as possible will be used.
The oil-contamlnated water is sent to the next ~oalescing equipment 114 in the form of a reduced oil charge, after much of the high concentration and high yiscosity oil is remoyed as the oil-contamlnated water passes ~hrough the first flotation separation tank 144. If there is no possibility in yielding high concentration or high viscosity oil in the oil-con~lunated water,. the first flotation sel)a~ation tank 144 can be eliminated and the oil-contaminated-wat-er from the pump 112 may directly ~e sent to the coalescing equipment 114.
FIG. 3 is a longitudinal sectional side view of the coalescing equipment 114, and FIG. 4 is a cross-sectional plan view of the same equipment. Equipment 114has a middle floor 117 at the bottom of a cylindrical case 115 to form a passage chan~er 118. An opening 119 is formed in the center portion of the middle floor and an ele-ment chamber 120 is formed over the middle floor 117, with ~r ~ 1 2 11'7~

chamber 120 accom~odating the-coale~cing element 121-which has porous material 124 on which specific coalescinq-layer having water permeable and absorbing function is formed. The structure of element 121 is the same as that of a conventional element. That is, around cylinder 123, which is formed with many through ~oles 122, at the center part thereof, porous material 124 is formed in a zigzag shape and the cylinder 123 is positioned over the opening 119 of the middle floor, and the upper end of the case 115 is coYered with a lid 116 to which an element-holder 125 is installed to ~ix element 121. Also, an appropriately wide space is formed to the peripheral side and upper portion of the element 121.
Further in this apparatus, each end of the flow in branch tube 127a and 127b which is separated through a changeover valve 126 and is attached and opened to flow to the inside of element chamber 120 and the passage chamber 118, and similarly each end of the flow out tuhe 124a and 129b, which is split from changeover valve 128, is opened to flow outside, opposing the opening of the flow-in tubes 127a, and 127b- The flow-in siae changeover valve 126 i5 attached to a pipe line 130 from the pump 112) and the flow-out side changeover valve 128 is attached to a pipe li.ne 131 which leads to a floating separatio~ tank 132.
In equipment 114, oil holding water from the pipe line 13~ flows into the equipment 114 either from branch tube 127a or 127b according to the operation of the change-over valve 128, such that flow out from the upper branch ~f' tube 129a occurs onl~ when flow occurs in fr~m the lower branch tube 127a, and on the contrary flows out from the lower branch tube 129b only while flow occurs in through the upper branch tu~e 127b. By virtue of the opera-tion of the changeover Yalves 126 and 128, the oil holding water ~assing in from lower branch tube 127a flows as ~x~n by a solid arrow rom the passage chamber 118 through the opening 119, the holes 122 of the cylinder 123, permeating through the material 124, through the branch tube 129a and exits to pipe line 131. Also, when~changeover valves 126 ana 128 are shifted to pass the oil holding water from the branch tube 127b, it flows as shown by the dotted arrow mark to permeate through the material 124 from the outer side and enter into the cylinder 123, through the opening 119, t.he passage chamber 118 and lower branch pipe 129b and passes out to the piping. In other words, by changing the flow-in and flow-out position with respect to the equipment 114 by the operation of changeover valves 126 and 128, the direction of oil holding water permeating through the element 121 is reversed.
When oil ~olding water flows into the equipment 114 and pe~meates through the element 121, not only the Coalesced--oil p~icles but also finely divided and scattered oil of the size less t~an 10 p is positively caught and collected by the oil separation function of the action of element material 124 which is formed with a coalescinc ~layer provid-ing a water penmeating and absorbing function, and the oil collection grows into a coarse oil particle which can ;~`'~''~' ~,i automatic~lly float, and is separated out due to ~his floating characteristic as well as due to the oil separa-tion function of the gel layer on the porous material 124 Moreover, by permeating through the element, by virtue of its special function, emulsion type oil dxop which were hiterto considered unable to be separated, grows from a coarse particle to a coarse sized lump which can be removed.
Oil-nolding water thus ~ermeating throu~h the element 121 is removed as water and a c0~2 oil particle through branch tube 129a or 129b and the pipe line into the next stage floating separat~on tank 132.
Now, in the oil~ nated water many types of admixtures (SS) such as suspension and small dust are generally included.
Therefore, the element will be choked so as to cause reduction of function during servicin~. In many conventional systems, operation of the equipment was stopped in such case to wash the element so as to recover its function, and this resulted in a reduction of processing a~ility to a marked degree. This invention has solved this deficiency splendidly, so as to enable the equipment to be operated continuously without stopping accompanied with cleaning effect of the element.
The equipmen~ can be operated with the manipulation of changeover valves 126 and 128 to divert the inflow between the branch tubes 127a and 127b~ and the outflow between the branch tubes 129a and 129b. The manipulation of these changeover valves causes the flow of oil~ontamunated - lS -water to be reYersed as showr. by solid line arrow mark and dotted line arrow mark in FIG. 3. l~is reYersal flow causes SS attached to the face opposite to the flow of the porous material 124 to ~e remo~ed. Moreover coarse parti~ulates, and enlarged oil drops which are attached to this surface will also be removed and separated by this reversal of ~low. Both sides of the element serve equally for coalesc~ng and enlargement of oil drops notwithstanding the direction of the flow of oil--contaminated water.
The manipulation of the changeover Yalves 126 and 128may be performed manually after an established time, after collection of an established amount, or by the increase of feed water pressure; however, automatic operation can be adopted by interlocking the operation of the valYes 126 and 128 with a timer, a flow meter, or a feed water pre~ssure gage. In the so-called reverse washing operation which will be performed by reversing the direction of flow of oil-~contar.l~nated water, removal of oil particles from the element is effecti~e as well as is the pressure loss at one element so as to be as low as about 0.1. 0.4 k~/cm2, which results in a good water permeating efficiency an~ therefore allows water feeding under low pressure.
Generally in oil water separation, oil will be finely divided to reduce coarse particulation separation as the feeding water pressure increases; however, in this invention a lower pressure can be used as stated before, - 16 ~

50 as to preYent oil fxom being finely diYided, and result in a synergistic effect for better coarse particulation of oil particles.
FIG~ 5 through ~IG. 8 indicates another example of the embodiment of the element and the coalescing equipment, in this example in the form of a 5ta~k of alternate flat an~ corrugated car~xxrd sheets to for~ arr~s of alternate inlet and outlet passages ~epara~ed by porous cardboard are used as the element as shown in FIG. 5.
This element 121 is made similar to the element 124 of the above-example; plain boards 140, which are made of porous material formed with a coalescing layer having a water permeable and water absorbing function and the corrugated boards 141 of the same material are placed alternately to form laminated structure, making many fine tubular passages 142, bein~ positioned between those plain board and the corrugated board. Either the top Or the bottom end of respective fine tubular passages 142 formed as noted abo~e are plugged by elements 143 as shown in FIG. 6, to allow each neighboring passage to be oppositely plugged.
Consequently, the oil holding water coming into each passage 142 is caused to flow only ~y permeating either plain board 140 or corrugated board 141. The pluggin~ 143 can be accomplished by an arbitrary method such as pressed adhesion using adhesive, or filling the opening with adhesive filler, etc.
FIG. 8 indicates coalescing equipment accommodating the elements as shown in above FIG. 5, in which many through holes 134 are formed in the middle floor 117 located on the bottom of the cylindrical case 115, the ele-ments 121 are placed on this middle floor 117, and a cavity ~ ~7~

133 is fo~ed a,boYe the elements 121, branch tubes 127a, 127b, and 129a, 129b are respecti~ely opened to the,passage chamber 118 ana the cavity 133. The oil-con~ami~ate~ water flowing in from either branch tube 127a or 127b enters into the passage 142, the ends of which are opened respectively as shown by the solid line ~rrow mark or the dotted line arrow mark, enters into the neighboring passage permeating the plain board 140 or the corrugated board 141, enters into the passage chambex 118 or the ca~ity 133 throu~h the opened end of the passa~e, ana,flows through the branch tube 129a or 129b.
The structure o~ the flute type element 121 as shown by FIG. 5 through FIG. 7 is more efficient than the conven-tional common structure as shown in FIG, 3 and FIG. 4, and their application as shown in FIG. 8 is easier to make smaller equipment, and the use of this type is more practical.
Specially such smaller configuration is indispensable in the case of limit:ed installation space as in the case of marine application, and this invention can comply with such a stringent installation condition.
As stated above referring to FI~. 1, oil-contaminated water is treated such that coarse particles are separated and float in the water through operation of coalescin~
, equipment 114 and flows into the next flotA~ion tank 132 through the pipe line 131.
The flotation tank 132 can be of any known type. In this example, physically enlarged oil particles naturally float to the upper portion of the tank 132 by 7l~iS~

means of their difference in reaction to gravity, and are taken into an oil collecting cylindPr 136 from the upper part of the tank 132 through a pipe 135 or discharged outside. At this stage~ the treated water is led to the crude water tank 101 or discharged outside.
The aboYe example indicates a ~asic oil water -separation system as a unit of the coalescin~ equipment;
however, multistage water ~low by air alternate series installation of the plurality o~ the coalescing equipment and ~lotation tanks may in many cases lea~:-t~--effective results according to the condensation and viscosity of the oil included. With such a multistage water flow system, coarse particulated oil is remo~ed prior to the next coarsing process, interim resistance of oil in the next process can positiYely be reduced and the oil separation rate can be impro~ed. Therefore, adoption of such multistage water flow system is ~esirable as far as the installation area permits it.
FIG. 9 indicates the outline of this multistage water flow sytem, in which oil holding water from the crude water tank 101 passes throu~h ~he preliminary flotation tank 144, then passes throuyh a water flow system of ~erially and multistaged coalescing equipment and flotation tanks in the order o~ the first coalescina equipment 114a -the first flotation tank 13~-a- the second coalesclng equipment 114b- the second flotation tank 132b, and feeds almost completely s~parated oil into the oil collecting cylinder 136. In this case the oil from the upper part of the second ~lotation tank 132b is :elown into the oil collecting cylinder 136 automatically or manually, and the processed water from the lower part of the second ~lotation tank 132b ~lows into the crude water tank 101 for the case of circulating use, and is otherwise dischargedO
This system is not only adequate for the efficient transient processing of oil containin~ water, but also demonstrates an especiall~ superior effect in the processing of emulsified finely divided oil containing water including oil particles smaller than 1 p b~ the effect of a surface active element, which could not be attained by conventional technique. For example, it has been experimentally confirmed that the water containing 250,0Q0 ppm of light oil can be processed to less than 5 ppm under the test specification of ship's equipment in accordance with the IMCO-Convention, and that 5 ppm determined as the limit for industrial waste water for environmental protection can perfectly be attained.
This invention has especially novel features in permitting separation of not only the finely divided oil but also the emulsified oil content, ~ecause of the forma-tion of the specific layer mainly consists of water insoluble hydrousgel layer having an oil water separation function as well as an oil resisting and oil repelling functionO
Althrough the theoretical base for this is not sufficiently clear, the following reason can easily be surmised from its structural characteristics. The abstract of the oil separation process is shown in FIG. 10. When oil-contaminated ~1~7~

water permeaters thr~ugh the element material 124 from one side, oil particles or emulsified oil particles in the oil-cont~nated water attach lightly onto the surface of the material 124 by its oil resisting and oil repelling function to form multiple coalesced oil a, and when oil in the continuously inflowing oil-contaminated water are formed as particles in the other part, some of them are caught in the coalesced oil particle a, and grow to become a large oil particle b, by and ~y those grown oil particles, b, b, will contact ea~h other to grow and form a large oil lump c as shown by the dotted line. This enlarged oil lump c will be separated from the surface of the material 126 ~y the repelling action of the material 124, ana is transformed to have a flotationcondition due to the self floating function in the oil-co~t~nated water as shown by the arr~ mark and begins to float. And many of these growing oil particles or lumps easily adsorb SS, and can removes SS as well as oil from the oil-contaminated water.
Another special feature of this invention is that, ~ecause Of its desirable SS xemoving performance stated above, the strainer 110 placed prior to enter in the coalescing- equipment 114 is not required to have such a fine straining mesh to collect e~en fine SS. For the requirement to catch relati~ely large SS only, a strainer of above 30 to 40 mesh will be sufficient for the purpose.
The conventional method requires use of as fine a mesh as possible to catch and remove SS there, and oil drops are finely divided there because of the effect of pressure caused by passing the fine strainer, and the fine ~1~7~

oil particles were thus emulsified to make raK~l of oil mDre difficult. On the contrary, by thi5 invention pressure resistance o the strainer is lower, does not cause emulsifi-cation and resul~s in easier oil separation in the coarse particulating equipment 114, which enables almost perfect removal o~ emulsified oil which is prevented from being further emulsified. Further, high pressure water feeding for high viscosity oil to a strainer causes a deficiency in intensifying emulsi~ication; however, the invention does not require high pressure water feeding equipment~ does not cause any impediment thereof, and because of simultaneous discharge of SS entrapped in the oil particle at the surface of the element, results in efficient removal of SS
simultaneous'y with oil separation.
Referring to FIG. 11, there is shown a flow chart of the methodaccordin~ to the present invention, wherein reference numercsl 221 stands for an element, 214 a granulator including element 221, 251 an oil extractor equipped with a motor 252 and an extracting pump 253, 226 a main changeover valve, 212 a main pump, 244 a first flota~iontank, 232 a secondflotation tank, and 254 an oil matter discharge pipe.
A feed of oil-contaminate~ water is passed through pre- ~
treatment device such as a strainer and the like, and pumped into the coalescing equipment 214 havin~ an element 221 via the pump 212, the first flotati~ll tank 244 and the main cha~geover valve 226.
FIG. 12 is a longitudinal section of the coalescing equip~nent 214. The coalescing-equi~ment 214 includes a coalescing cylinder 215 prQYided at its lower portion with a middle flooring 217 to form a passage chamber 218. An openin~ 219 is formed in the central portion of the ~looring 217 over which is mounted an element chamber 220. The chamber 220 is incorporated with the coalescing element including a porous material 224 on which is applied a specific coaleseing layer capable of absorbing and transmitting water therethrough.
The element 221 may ~e identical in construction with ~
the widely available element. More specifically, the porous material 124 treated as mentioned aboYe is corniced around a cylindrical member 223 haYin~ a numbex of through holes 222, 222 at the center~ The member 223 is positioned in alignment with the opening 219 in the flooring 217 and fixed thereon. There s then left an appropriate space 233 around and aboYe the element 221.
The ~oalescing equipment 214 is also fo ~ d with c~ inlet (outlet) pipes 227a, 229a in communication with the changeover valve 226 and with a pipe 227b for connecting a plurality of cylinders 215 with each other, if applied. It is noted that, where the coalescing cylinder 215 is of a single stage arrangement, the process liquid returns from the connecting pipe 227b to the changeover valYe 226.
The oil-con~nated water fed by the main pump 212 is passed through the changeover valve 226 as indicated by the solid lines in FIG. 12, enters the element chamber 22Q, permeates through the porous material 224, and enters an element chamber 220 of the next coalescing cylinder 215 from the out-let pipe 227b via the opening 219 in the middle flooring

5'~,~

217. A material ~low similar to that in the first cylinder 215 is also foImed in the second cylinder 215. This flow is fed to the changeoYer valve 226 via the element chamber 220 ana the element 221, from which it is supplied into the second flotation tank 2~2.
As the oil-contam~ted water enters the c~alescing equipment 214 and permeates through the element 2 1, a dispersion ~-?ith fine oilparticles having a size of at most 1~ microns being dispersed, to say nothing of the coalesced-oil matter, is positively collected owing to the oil-absorbing function under the action of the porous material 224 on which is applied the specific layer capable of separating oil from water due to its water-transmitting and -absorbing' properties. The thus collected oil matter grows into a larger oil granule which is sPontaneously floatable, and is separatecl out due to floatage as well as the oil-separating function provided by the (oil-repelling~ gel layer on the porous material 224. With the element 221 having such a unique function, it has now been found that oil drops in the emulsion form can grow into ~ larger particles and be separated off, despite the fact that they have been considered unable to be isolated.
me oil matter reaching the top of coalescina equip~.ent 214.
shown in FIG. 12 is positively extracted as occasion arises or at regular intervals by the pump 253 incorporated in the extractor 251, and is fed into the second flotation tank 232. Especially where a p~urality of coalescinq equip~ent.214 are arranged in multistage manner, an extractor is provided ;

. :
- 24 - ~

~1~7~

for each coalescing equi~nt. with this arrangeme~t, the oil mHtter having a high oil content and/or a high oil concentration serves to xeduce a load applied on the surface layer of element 221 in the next coalescinq e~uirment 214 in the course of coalescen~e, ~hus making marked improvements in the efficiency and durability of coalescing equipment 214.
It ~as been ~ound that the provision of extractors results in considerable reductions in the number of coalescinq equipment 214.
The concentrated oil matter thus fed to the second flotation ~ 232 is further fed to an oil-water separator which automotically separate the oil from the water by use of different levels resulted from the different specific gravities.
A typical conventional sep~rator by specific gravity i5 illustrated in FIG. 13. A water reservoir 362 into which is introduced a feed of oil-con~ nated water is provided at its lower portion with an inlet portion 364 for a water discharge pipe 363, which extends vertically from the inlet 20 portion 364 and terminates in an outlet port 365 positioned outside of the reservoir 362. The reservoir 362 is also provided at its inner upper portion with an inlet port 369 for an oil discharge pipe 368 terminating in an outlet port located outside of the reservoir 362. The inlet port 369 for the oil dischar~e pipe is then positioned at a level higher than the outlet port 365 for the water discharge pipe. Such a level difference is shown at Hd.
On the other hand, an oil matter of high concentrations built up in the upper portion of a ~lotation tank 332 is ,~ i '135~

slowl~ pumped into the reserv~ir 362 ky adjustment of a ~al~e 3321 mounted on an oil-ascending pipe. Only the oil matter of high concentrations is separated from the oil- cont~nated water in the res~rvoir 362, and automatically forms an oil layer in the upper portion thereof. Upon the oil layer reaching at its uppermost surface the inlet portion 369 for the oil discharge pipe, only the oil matter is auto-matically discharged throu~h the inlet port 369 to the out-side. Ihe treated water Xree from oil matters of high con-centrations enters from the inlet portion 364 providedin the bottom of water res~rvoir 362 into the water discharge pipe 363, and is discharged through the outlet port 365 to the outside. It is noted that, since there is a level difference Hd between the inlet port 369 for the oil 15 discharge pipe and the outlet port 365 for the water dis- !
charge pipe, only the treated water is automatically discharged with no removal of the oil matters until the thickness of the oil layer amounts to Hd No automatic discharge of on:Ly the oil matters takes place through the outlet port 369 until the oil layer has a thickness amounting to Hd. The oil level is always maintained at a level higher than the water leYel due to the difference in specific gravity between the oil and water parts.
The prior art oil-water separator illustrated is characterixed in that, by making use of such a level difference Hd, an oil matter can be removed through an oil discharge pipe only after an oil layer is surely formed, having a thickness amounting to at least Hd.

11 7~59;~ l The con~Tentic~n~l ar~angelnent ~f FIG. 13, although functioning satisfactorily in a stationary s ate, has a disadYantage in that it ca2mot follow a tilting movement.
That is to say, a level di~ference ~d varies in an inclined 5 state with resultant discharge of a part water through the inlet poxt 369 for the oil discha.rge pipe, since there is a distance between the outlet port 365 for the water -discharge pipe and the inlet port 369.
The following apparatus proYides an oil-water separator 10 which is free from the above-mentioned drawbacks, and can sufficiently be us~3d in, for example, shipping experiencing tilting and rolling moYements.
Referring to FI(;. 14 which is a sectional yiew of one embodiment of the present invention, a 7ater reservoir 362 is provided at its lowex portion with an inlet 364 for a water discharge pipe, ar~d at its central upper portion with an outlet 365 for the water discharge pipe, which is positioned vertically. Above the outlet 365, there is an opening space 367 which is covered with a water 20 discharge pipe sleeve 366 positioned at a level sufficiently higher than a liquid level. The water treated is discharged through the pipe 366. ~n inlet port 369 for an oil discharge pipe is provided around the sleeYe 366. The oil discharge pipe inlet 369 is positioned at a level higher than the water 25 discharge pipe outlet 365 (with a level difference Hd), whereby an oil matter is separeted from oil-contaminated water and constantly discharged in an automated manner.

The arrangement of FIG. 14 is dif:Eerent from that of FIG. 13 in the ~ollowing points. In ~ccoxd~nce with the FIG. 13 embodiment, the water discharye pipe outlet 365 and the oil discharge pipe inlet 369 are located at the center portion of the water reservoir and positioned in proximity to each other with a level difference Hd, and the opening 367 in the water dischar~e pipe sleeve 366 applied on the port 365 is positioned at a level sufficiently higher than a liquid level. With such an arran~ement, there is no ~irtural variation in the leYel di~ference Hd between the outlet port 365 and the inlet port 367, even in an inclined state. Consequentlyl only an oil matter can be dischar~ed through the oil discharge pipe inlet 369, even when the arrangement is out of the pe~pendicular.
There is also no possibility that an oil matter may enter the water discharge pipe 366 due to tilting or rolling, since the opening 367 in the sleeve 366 is positioned considerably above a liquid level. Namely, the separator of the present invention is not affected by tilting or rolling, and can constantly effect automated separation of oil matters from oil~ontamlnated water-, and discharge of the oil matters and the treated water. As shown in FIGo 14 ~ ¦
the angular disposition of the oil discharge pipe 368 and the water discharge pipe 366 assures satisfactory discharge of oil and water eYen in a state where the separa-tor is out of the perpendicular. The device explained in the foregoing is suited for a ship which is sub~ected to vibration or tilt. In order to prevent waves from bPing created on the liquid surfaces, oil resistant and net-shaped ~ 28 -~'7~35~

structure may be proYided below the surface of the liquid shown in FIG. 14. In such an exampler it is preferable that the structure has a predetermined thickness and extend from the water discharge pipe 366 and the oil discharge pipe inlet 369 to cover the entire liquid surface such as to meet the minimum tilting re~uirement o~ 25 degrees in all directions stipulated in the Ocean Pollution Preven-tion Law according to ~he IMCO Convention.
Another example of oil water separator will be explained referring to FIG. 15,. In a water reseryoir 36-~ a water discharge pipe 363, an oil discharge pipe 363 and a water discharge pipe sleeve 366 are at their middle portions with flexible pipe members 363', 368' and 366'. A plurality of floating rod 372 extend sideways from the pipe 368, and are provided with floats 373. The floating rod 372 are also formed at the distal ends with float guides 374 which serve to maintain a water discharge pipe outlet 365 and an oil discharge pipe inlet 36~ at the center of reservoir 362, when the separator is out of the perpendicular. In the embodiment as illustrated in FIG. 16, the float guide comprises a radially extending L-shaped lever 374-pivotable around its apex, a balance weight 3742 attached to its inside and a guide 3743 attached to its outer end.
With such an arrangement, the water discharge pipe outlet 365 and the oil discharge pipe inlet 369 can follow a tilt of the associated vessel, i.e., an inclination of the water reser~oir. The water discharge pipe outlet 365 and the oil discharge pipe inlet 369 are maintained at the central position of the water reservoir 362 under that ~ . .

54~

action o~ the guides 374~ That is to say, when a til~
is given to ~he reservoir 352 to form the liquid surface into an ellipitical shape, the balance weight 3742 in correspondence with the major axis thereof descends and forces out the guide 3743, so that the outlet 365 and the inlet 369 are always maintained at the central position of the reservoir 362. The embodiment of FIG. 14 can sufficiently follow a tilt of the xeservoir 362, provided that the oil aischarge pipe inlet 369: h~s sufficiently small diameter relative to the reservoir 362. When it is requixed to increase the diameter o~ the inlet 36~ for attachment to a large-sized vessel, however, there is a risk that a portion of water below the oil layer may possibly enter the oil discharge pipe inlet 369 of FIG. 14 by an inclination thereof. The example of FIG. 15 is characterizecl in that it can completely follow a tilt of the liquid surface since the diameter of the oil discharge pipe inlet 369 is relatively large. Thus, this example provides an automated oil discharge device which, if applied to a large-sized vessel, can function satisfactorily without being affected by a tilt of the vessel. An automated discharge device using an electric sensor is known; however, it practically presents mal-function problems when used with a creamy oil matter having a larger content of water. This is the reason why the separa-tor according to the present invention is developed.
As mentioned above, the above separator can automatically separate and discharge oil matters from oil--contaminated without being affected by tilting and rolling movements 3~ -3 l'î'~34~

of a Yessel to which it is attached, and can be best-suited for use in shipping with good performance, thus meeting the abo~e mentioned IMCO requirements.
Further, it is preferable that a coalescer is provided in the reservoir 3S2 and/or the flotation tank 332 to prompt the oil particles to float in a shortest possible time.
As shown in FIG. 16, there is provi~ed a coalescer 370 in the flotation tank 332, which coalescer includes a plurality of slanting plates 371 maintaining predetermined spacings.
It is known in general that, the larger the di~meters of oil particles dispersed in the water are~ the quicker those particles float on the water surface. If the tank 332 is, partitioned by the slanting plates, the particles reach the plates in a shorter time than they float onto the water surface where no coalescer is provided. Thus, even if the diameters of the particles are small, they reach the slanting plates one after another to coalesce each other to become lar~er-sized oil particles. Those oil particles ascend along the plates 371 to reach the liquid surface. This is known as coalescence effect. m e coalescer may be provided not only in ~he form of the example shown in FIG. 16 but may be providea in the reservoir 362.
Moreover, if it is provided in th~ flotation tank 144, 244, or 232 in the embodiments of ~IGS. 1, 9, and 11, the efficiency of oil-water separation of the entire system shows remarkable improvement.
Referring to ~IG. 17, there is shown a flow chart of another embodiment, wherein reference numeral 421 'l l 17~5~

stands for an element, 414 a coalescing e~ipment including therein eiement 421, 451 an oil extractor equipped with a driving device 452 and an extracting pump 455, 456 an extraction tan~ 426 changeoYer valve, 430 a water supply pipe, 458 a discharge pipe, a main pump, 444 a first ~lota~ion tank, 432 a second flotation tank, and 459 an ~utomated oil matter discharge device.
A feed of oil-contaminated water is passed through a pretreatment device such as a strainer and the like, an~ pumped into the coalesci~g-equipment 414 having element 421 via the pump 412, the first 1Otation -tank 444 and the change-over valYe 426.
FIG~l~ is a longitudinal ~ tion of the coalescing equi~ment 414. me coalescing equi~ment 414 includes a co~lescing cylinder 415 provided at its lower portion with a middle flooring 417 to form a passage chamber 418. An opening 419 is formed in the central portion of the flooring 417 which -defines an element chamber 420. The chamber 420 is incorporated with the ~oalescing element including a porous material 424 on which is applied a specific coalescing layer capable of absorbing and transmitting water therethrough. The element 421 which takes a horizontal position may be identical in construction with the widely available element. More specifically, the porous material 424 treated as mentioned above is corniced around a cylindrical member 423 having a number of through holes 422, at the center. The member 423 is positioned in alignment with the opening 419 in the flooring 417 and fixed thereon. There is then left an appropriate space 433 around and above the element 421.

XI;~ I

Theccalescing ~quipment 414 is also f~rmed with inlet (outlet) pi~es 427a, 429b, 427b in communication with the changeo~er valve 426. The mechanism 451 for extracting oil matters built up in the coalescing esui~ent 414 is connected with the coalescing ~guipment 414 with an inlet(out'et~ pipe 42gb. The oil mat~er~
are extracted in the upper portion of the tank 456, and the water from which the oil matters haYe been separatea in the ~ 456 is returned to the ne~t coalescmq ecui~ment 414 ~r the changeover YalYe 426 via the plpe 429c j or 427b. The oil~contaminated WRter fed by the pump 412 is passed through the changeover valYe 426 as indicated by the solid lines in FIGS. 18 and 19, enters the passage chamber 418, permeates through the porous material 424 of the element 421, and is forcibly fed into the extraction tank 456. The oil matters extracted in the upper portion of the mechanism 451 is extracted via the extraction valve 455, and is supplied into the second ~lotation tank 432.
The water treated is returned to the changeover valve 426 via the pipe 427h, and forcibly supplied into the second ~ flotation tank 432 via the discharge pipe 431.
As the oil-contaminated waterenters the c~alescing eouipment 414 and permeates through the element 421, a dispersion with fine oil particles haYing a size of at most 10 microns being dispersed, to say nothing of the coalesced oil matter, is positively collected owing to the oil-absorbing func-tion under the action o the porous material 424 on which is applied the specific layer capable of separating oil from water due to its water-transmitt.ing and -absorb.ing properties. The thus collected oil matter grows into a larger oil granule which is spontaneously floatable, and 7~

is separated out due to flo~tage as well ~s the oil-separating function pxovided by the (oil-repelling) gel layer on the porous material 424~ With the element 421 ha~ing such a unique function, it has now ~een found that oil drops in the emulsion fo~m can grow into a larger granule and be separated off, despite the fact that they have been considered una~le to be isolatedO
The oil matters coalesced by the coalescing equipment 414 is accumulated in the upper portion of the tank 456, and positively extracted as occasion arises or at regular inter~als by the extraction YalYe 455 of the mechanism 451 operable by the driving mechanism 452. The oil matters are then supplied into the second flotation tank 432.
ÆsreciallyT,~ere a æl~ralit~ of coalescing ~ipment 41~ are arr~nged in multistage manner, an extractox is provided for each coalescino ~ipmént~ With this arrangement, the-oil matter having a high oil content and/or a high oil concentration serves to reduce a load applied on the surface layer of element 421 in the next coalesc:ing equipment 414 in the course of coalescence thus making marked improvements in the efficiency and durability of coalescing- æq~ipment 414.
It has been found that the pro~ision of extractors 451 results in considerable reductions in the number of coalescing equipment 414. In general, the oil-c3nta~ted wat~r is contaminated with many kinds of impurities (SS) such as suspended matters and fine dust. For this reason, clogging of the element 421 t~kes place during use with resultant lowering of the efficiency thereof. In such a case, most of conventional systems were shut down to wash the element 1 ~7~

for the puxpose of xecoYering their function, leading to a reduction of processing ability to a marked degree.
The present invention offers a skillful solution to this problem, and enables the apparatus to be operated in a continuous manner without shutdown, w~ile the element is washed.
In the present invention, the direction of material flow is changed by the operation of the changeoYer valve 426 to cause reversal of the flow before clogging of the element 421 occurs. The manipulation of the changeover valve causes the flow of oil-conta~inated water to be reversed as shown by solid line arrows and dotted line arrows in FIG. 18. This reversal flow causes removal of SS deposited onto the face of the porous material 424 opposite to the flow. Moreover, oil granules of smaller and larger sizes which are ~eposited onto this face will also be removed and separated by this xeversal of the ~low. Both sides of the element serYe e~ually for the ~oalescence and growth of oil drops notwithstanding the direction of the flow of oil- aontaminated water. The operation of the changeover valve 426 may ~e performed manually independence upon the giYen duration of operation, the given throughput and the increase in feed pressures. Alternatively, the changeover valve may be automatically operated in coopearation with a timer, a flow meter or a feed water pressure gauge.
In the alternating operation according to the present invention wherein the direction of material flow is altered, successful removal of oil ~articlesfrom the element is attained with attendant pressure loss amounting to as low as about 0.1 to 0.4 Kg/cm , so that the element 421 is ~ 35--s'~

of high water pexmeability. Such ~ high water permeability, coupled to the extraction of oil matters, enables the element 421 to coalesce an oil matter having a high viscosity at lower pressures. This offers one of the characteristic features of the present invention.
In the oil-water separator systems, it is generally said that the higher the feed pressure, the lower will be the separation efficiency because of fine coalescence of oil. In the present invention, however, a lower pressure can be applied as discussed above, so that such fine ~oalescence ~ oil is avoided. This has a synergistic effect that assures satisfactory coalescence of oil drops in the present invention. These considerations lead to the realization of the present invention.
While the foregoing explanation implies a case where a plurality of element cylinders 414 are arranged in multistage manner, whether the apparatus is of a single stage or multistage arrangement may be dependent upon the throughput of oil-contd~nated water , and the concentration and viscosity of an oil matter. Alternati~ely, it may be possible to operate part of the multistage apparatus under normal conditions, which apparatus can be operated in its entirety only under severer conditions.
Further ~lotation tank 432 may be provided on top of the automatic oil discharge section 459, which is shown by ar.y of the FIGS. 14 to 16.
Referring to FIG. 19 which schematically shows the method of the present invention, a feed of oil-con~nated water is fed into a changeo~er valve 526 via a first .~

7854~

flotation tank 544. Cr.ude oil matters are eliminated by an oil matter-remoYing deYice 559 in the first flota~ion t~n~ 544. A flow~direction chanqeover mechanism 577 for the oil-conta~inated water comprises a motor 575 and a changeover YalYe 526 for effecting flow direction changeoyer of the oil con~amina~ed water~ Such changeo~er way be effected by reversal of ~he predetermined tilt of an element column 523 ~y puttin~ the Yalve in operable association with a mechanism 576 for preventing a build-up of oil matters. Referring to the case where a feed of oil-contaminated water.: is ~uided in the direction as indicated by the solid lines in FIG. 1, it is fed into a passage chamber 518 in the element column 523 having therein an element 521, and directed into an oil matter extractor 551 via the element 521 and an element chamber 520.
FIG. 20 is a longitudinal section of the element column 523, and FIG. 21 is a par~ial cross-section of the element 521, illustrative of the flow direction of oil-contaminated , water. The element 521 may be identical in construction with the wIdel~ available element. More preferabl~, however, ~he élement is in the form of a stack of flat and corrugated cardboard sheets to form arrays of alternate inlet and outlet passages 542 separated by the porous cardbo~rd. The elongated passages 542 as shown in F~G.-20 have one ends 539 opened and the other ends 543 closed as depicted in FIGS 20 to 21, $o that --~i'/'~54~

the oil-cont~n~na,e~--~te~ pen~tes throu~h adjacent ~as~ges 542 by way of the aboYe-mentioned specific layers. The oil matter extractor 551 comprises a motor 575, an extraction val~e 555 and an extraction column 556, and is operated malnually or automatically depending upon operating time or pressure to extract the oil matters which are then fed into a second flotation tank 532.
The water thus treated by extraction is passed into the next element column 523~ It is noted that, with the ele-ment column 523 of a single stage arrangement, the watertreated returns from the extraction column 556 to the change-over val~e 526. m is is true of the case where the oil-cont~na~ed w~ter is passed in the direction as indicated by the dotted lines in FIG. 19 by changeover of the valve 526 and opposite to that as indicated by the solid lines.
The treated water leaving the final stage extraction column 556 returns to the chanyeover val~e 526, from which it is feZ
into the second flotation tank 532.
As the oil-cont~nated water permeates through of the unique layer of the element 521, a dispersion with fine oil?articles having a size of at most 1 micron being dis-persed, to say nothing of the coalesced oil matter, is positively collected owing to the oil-absorbing function under the action of the porous material on which is applied the specific layer capable of separating oil from water due to its water-transm tting and -absorbing properties.
The thus collected oil matter grows into a larger oil granule which is spontaneously floatable, and is separated out due to floatage as well as the oil-separating function 11'7~4~

provided by the ~oil-repelling~ gel layer on the porous material. With ~he element 521 haYing such a unique function, it has now been found that oil drops in the emulsion form can grow into a larger ~article and be separated off, despite the fact that they have been ~onsidered unable to be isolated.
The oil mattex reaching the top of the element column 523 is posi~ively extracted by an extractor 551. Especially where a plurality of element cylinders 523 are arranged i~ in multistage manner, an extractor is provided ~or each c~alescing equip~lent. I~ith this arr~ngement, the oil matter having a high oil content and/or a high oil concentration serves to reduce a load applied on the surface layer of element 521 in the next element 521 in the course of coalescence making marked improvements in the efficiency and durability of coalescing.equipment.
The embodiment is further characterized in that the mechanism 576 is proYided for the pxevention of a build-up of the oil matters coalesced in the element 521 and 20 element column 523. Referring to the embodiment o~ FIG. 19, the coalescing element 523 is inclined at an angle Al, and is disposed for pivotal movement that is caused by the motor 575 such that open ends of the elongated passages 542 normally take raised positions. With the aforesaid angle is set Al, a flow of oil-contaminated water is passed in the direction indicated by the solid lines. For reversal of the flow, the column is inclined at an angle A2.

~ ~.",0, - 39 ~

~ ~7~

As ~entioned aboYe, xeYexsal of the angle of tilt of the element column causes the oil matters coalesced in the elongated passages 542 of element 521 and the el~ment column 523 to ascend and reach the inclined upper extrac~or s 551 without discontinuities, thus resulting in considerable in~reases in the efficiency of separation and removal of oil matters.
It has been found that the proYision of extractors 551 results in considerable reductions in the number of element cDlumns 523. In general, the oil-contaminated water is contaminated with many kinds o~ contaminants or impurities (SS) such as suspended matters and fine dust.
For this reason, clogging of the element 521 takes place during use with resultant lowering of the efficiency thereof. In such a case, most of conventional systems were shut down to wash the element for the purpose of recovering their function, leading to a reduction of processing ability to a marked degree. The present invention offexs a skillful solution to this problem, and enables the apparatus to be operated in a continuous manner without shutdown, while the element is washed.
It has now been confirmed that the aboYe-mentioned two requirements, i.e., prevention of accumulation of the oil matter in both the element 521 and the element column 523 and changeover of material flow, have a synergistic effect in maintaining the efficiency of the apparatus for a very extended period of time even when it is used with an oil matter a high viscosity.

Xn the pxesent inYention~ the direction of material ~low is chanyed by the operation of the changeover Yalve S26 to cause reversal of the flow ~efore cloggins of the ~lement 521 occurs. The manipulation of the changeo~er valYe causes the flow of oil-con~nated waterto be reversed as shown by solid line arrows and dotte~ line arrows in FIG. 1~.
This reversal flow causes removal o~ SS deposited onto the face of the porous material opposite to the flow.
~oreover, oil granules of smaller and larger sizes which are deposited onto this face will also be removed and separated by this reversal of the flo~. Both sides of the element 521 serve equally for the .coalescence and growth of oil drops notwithstanding the direction of the flow of oil-contaminatedwater . m e operation of the changeover valve 526 may be performed manually independence upon the given duration of operation, the given throughput and the increase in feed pressures. Alternatively, the change-over valve may be automatically operated in cooperation with a timer, a flow meter or a feed water pressure gauge.
In the alternating operation according to the present invention wherein the direction of material flow is altered, successful removal of oil granules from the element is attained with attendant pressure loss amounting to as low as about 0.1 to 0.4 Kg/cm2, so that the element 521 is of high water permeability. Such a high water permeability, coupled to the forced extractor 551 for oil matters, enables the element S21 to coalesce an oil matter having a high viscosity at low pressures. This offers one of the characteristic features of the present invention.

~,,~
~ 41 In the oil-water separ~t~r systems, it is senerally said that the hi~her the feed pressure, the lower will be the separation efficiency because of fine granulation of oil.
In the present invention, however, a lower pressure can be applied as discussed aboYe, so that such fine ~ranulation of oil ~s avoided. This has a synergistic effect that assures satisfactory granulalion of oil drops in the present invention. These considerations leads to the realization of the present inYention.
While the foregoing explanation implies a case where a plurality of element column 523 are arranged in multistage manner, whether tfie apparatus is of a single stage or multistage arrangement may be dependent upon the throughput of Oil-contaminated water and the concentration and viscosity of an oil matter. Altern~tiYely, it may be possible ~o operate part of the multista~e apparatus under normal conditions, which apparatus can be operated in its entirety only under severer conditions.
This syste~m is not only adequate for the batchwise processing of oil-contamunated water, but also demonstrates an especially superior effect in the processing of emulsified finely di~ided oil-conta~inated water including oil particles made smaller than 1 ~ by the effect of a surface active agent, which could not be attained by con~entional technique. For example, it has been confirmed by experiment that the water containing 250,000 ppm of light oil can be processed to less than 5 ppm under the test specification of ship's equipment in accordance with ' ~
- 4~ -~'7~

the IMCO-Convention r and that 5 ppm determined a~ the limit for industrial waste water for environmental protection can perfectly be attained.
This invention has especially novel features in permitting separation of not only the finely dividea oil but also the emulsified oil matter, because of the fo~mation of the specific layer mainly consists of water insoluble hydrousgel layer ha~ing an oil water separation function as well as an oil-resisting and oil-repelling function.

Claims (25)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for oil-water separation by coalescence comprising the steps of:
forming a coalescing layer having oil-resisting and repelling properties as well as water transmitting and absorbing properties on at least one surface of a porous material by forming thereon a water-insoluble hydrousgel layer while maintaining a porous nature of the material, to obtain a coalescing element; and subjecting said coalescing element in a coalescing equipment to a flow of an oil-contaminated water such that said oil-contaminated water passes through the porous material to catch emulsified oil particles upon said at least one surface, said oil-contaminated water passing through the coalescing element alternately from each side thereof to the other.

2. A method according to claim 1, further including prior to said subjecting step, a step of gravity separating an oil matter from said oil-contaminated water in a flotation tank.

3. A method according to claim 2, wherein said subjecting step and said separating step are repeated.

4. A method according to claim 1, further including a step of extract removing the coalesced oil matter from said coalescing equipment.

5. A method according to claim 4, wherein said subjecting step is performed in plural consecutive stages.

6. A method according to claim 4, wherein said removed oil matter is subjected to a further gravity separation step to discharge the separated oil matter.

7. An apparatus for oil-water separation by coalescence comprising:
a coalescing element having a coalescing layer having oil-resisting and repelling properties, said element being formed by forming a water-insoluble hydrousgel on at least one side of a porous material while maintaining a porous nature thereof;
a casing to accommodate said coalescing element; and inlet and outlet means provided in said casing for allowing an oil-contaminated water to pass through the coalescing element alternately from each side thereof to the other.

8. An apparatus according to claim 7, further including a flotation tank to receive an oil-contaminated water prior to its flow into said casing.

9. An apparatus according to claim 8, further including a reservoir provided on top of said flotation tank to receive the oil-contaminated water from said flotation tank;
a water discharge pipe having an inlet portion thereof at its lower portion and extending vertically from a central bottom of said flotation tank up to a predetermined level below the water surface;

a water discharge pipe sleeve enclosing the water pipe discharge pipe from the oil-contaminated water, an upper end of said water discharge pipe allowing to overflow dis-charge water into said sleeve and extending higher than the water surface, said sleeve being adapted to discharge the water separated from oil outside the reservoir; and an oil discharge pipe provided to enclose the water discharge pipe sleeve and having an inlet port slightly below the liquid level and above the upper end of the water discharge pipe such that the oil separated from the water is discharged outside of the reservoir by use of a difference of levels due to that of specific gravities of the oil and the water.

10. An apparatus according to claim 9, further including coalescer means within at least one of the said flotation tank and said reservoir.

11. An apparatus according to claim 7, wherein said coalescing element is in the form of a stack of alternate plat and corrugated cardboard sheets to form arrays of alternate inlet and outlet passages separated by porous cardboard.

12. An apparatus according to claim 11, wherein said alternate inlet and outlet passages have ends thereof close and open alternately.

13. An apparatus according to claim 7, further including means for extracting a built-up oil in said casing.

14. An apparatus according to claim 7, wherein said inlet and outlet means is adapted to change the flow of oil-contaminated water passing through the coalescing element.

15. An apparatus according to claim 13, further including a flotation tank to store the concentrated oil-contaminated water extracted by said extracting means;
a reservoir provided on top of the flotation tank and into which said concentrated oil-contaminated water is incorporated from the flotation tank;
a water discharge pipe having an inlet portion thereof at its lower portion and extending vertically from a central bottom of said flotation tank up to a predetermined level below the water surface;
a water discharge pipe sleeve enclosing the water pipe discharge pipe from the oil contaminated water, an upper end of said water discharge pipe allowing to overflow discharge water into sleeve, and extending higher than the water surface, said sleeve being adapted to discharge the water separated from oil outside the reservoir; and an oil discharge pipe provided to enclose the water discharge pipe sleeve and having an inlet port slightly below the liquid level and above the upper end of the water dis-charge pipe such that the oil separated from the water is discharged outside of the reservoir by use of a difference of levels due to that of specific gravities of the oil and the water.

16. An apparatus according to claim 15, further including coalescer means within at least one of the said flotation tank and said reservoir.

17. An apparatus according to claim 15, wherein intermediate portions of said water discharge pipe, said water discharge pipe sleeve, and said oil discharge pipe are flexible, said water discharge pipe sleeve or said oil dis-charge pipe having plural floating rod radially extending therefrom, said floating rods carrying a ring-shaped float at their intermediate portions and an L-shaped lever pivotally at an apex thereof on an end of each floating rod, an inside end of the lever carrying a balance weight and an outside end of the same carrying a guide.

18. An apparatus according to claim 7 or 11, wherein said coalescing element takes a position such that said inlet and outlet passages is oriented vertically.

19. An apparatus according to claim 12, wherein the inlet and outlet means provides a flow of the oil-contaminated water passing through a coalescing element alternately from each side thereof to the other, said coalescing element being adapted for pivotal movement such that open ends of the passages normally take raised positions.

20. An apparatus for oil-water separation by coalescence comprising:
a plurality of coalescing elements each having a coalescing layer having an oil-resisting and repelling properties, said element being formed by forming water-insoluble hydrousgel on at least one side of a porous material while maintaining a porous nature thereof;
a casing to accommodate each coalescing element; and inlet and outlet means provided in said casing for allowing an oil-contaminated water to pass through the coalescing element alternately from each side thereof to the other.

21. An apparatus according to claim 20, further including means for extracting a built-up oil in said casing.

22. An apparatus according to claim 21, wherein said inlet and outlet means is adapted to change the flow of oil-contaminated water passing through the coalescing element,

23. An apparatus according to claim 7, further including a crude water tank to store the oil-contaminated water which is to be admitted into the casing prior to thereof and suction means for sucking high oil-concentration part at the surface of the oil-contaminated water stored in said crude water tank.

24. An apparatus according to claim 23, wherein said suction means includes an outer cylinder having a take-out tube at a bottom thereof and positioned below the liquid level and a weir cylinder provided vertically movably within the outer cylinder and adapted to keep a brim thereof posi-tioned slightly below the liquid level and providing communication with said take-out tube.

25. An apparatus according to claim 24, wherein said brim has a saw-edge configuration.