Method for oil-water separation of oil-in-water suspension and separation device

Abstract

To provide a novel method for oil-water separation of an oil-in-water suspension and an oil-water separation device.SOLUTION: A method for oil-water separation is provided, comprising: contacting an oil-in-water suspension with water, which may contain microbubbles, such that a suspension-rich phase is positioned above and a water-rich phase is positioned below; supplying new microbubbles to the water-rich phase so as to prevent uniform mixing between the suspension-rich phase and the water-rich phase; and floating microbubbles having adsorbed micelles in the suspension. Also provided is an oil-water separation device comprising: a separation tank that houses an oil-in-water suspension and water, which may contain microbubbles, such that a suspension-rich phase is positioned above and a water-rich phase is positioned below; and a microbubble generator that generates microbubbles to be supplied into the separation tank, wherein the microbubble generator is disposed such that the generated microbubbles are supplied to the water-rich phase, and the interior of the separation tank is not stirred during microbubble generation in a manner of preventing uniformity inside the tank.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for separating oil from water in an oil-in-water suspension. [Background technology]

[0002] The production of useful compounds using biological cells is widely carried out. When useful compounds are not secreted outside the cells but are stored in intracellular vesicles, it is necessary to disrupt the cell walls and cell membranes in order to extract the useful compounds. A commonly used method for disrupting cells is to apply strong shearing force (Patent Document 1, etc.). When the useful compound is a lipophilic compound (hydrophobic compound), the useful compound is extracted into a non-polar organic solvent by liquid-liquid extraction in which a non-polar organic solvent is brought into contact with water containing cell fragments. Here, when culturing microorganisms, etc., an antifoaming agent is usually added to the culture tank. When the culture liquid containing the microorganisms is extracted from the culture tank and disrupted by applying shear force, the antifoaming agent may act as an emulsifier and form a water-in-oil suspension (emulsion). When a water-in-oil suspension is formed, the oil phase cannot be efficiently separated, resulting in problems such as a decrease in yield, high costs due to an increase in the amount of organic solvent used, and complicated post-treatment. Patent Document 2 proposes a stable and efficient method for producing fat-soluble bioactive substances, in which an aqueous suspension of microbial cell lysates containing the fat-soluble bioactive substances is heated in the presence of a specific nonionic surfactant and alkali, and then mixed with an organic solvent to extract the fat-soluble bioactive substances.

[0003] A method for separating hydrophobic compounds by adsorbing them onto the surface of bubbles is known. Patent Document 3 proposes a method for separating hydrophobic compounds produced by a biological reaction in an aqueous medium, in which bubbles are brought into contact with the aqueous medium to collect the hydrophobic compounds contained in the aqueous medium at the bubble interface, and then the bubbles are separated from the aqueous medium. In the method described in Patent Document 3, the hydrophobic compounds dissolved or dispersed in water are adsorbed onto bubbles blown out from a porous body. When the method described in Patent Document 3 was applied to an emulsified water-in-oil suspension, the bubbles that were generated became large, and it was not possible to adsorb the micelles. The inventors of the present invention conducted an investigation and, although the mechanism is unclear, it was confirmed that when micelles adhere to the surface of a porous body, the micelles collapse and the oil covers the surface of the porous body, blocking the pores that release fine bubbles, and bubbles are generated only from the large pores that are not blocked, causing the bubbles to become large.

[0004] The present applicant has proposed a biological reaction apparatus comprising a culture tank for accommodating a biological culture solution, a micro-nano bubble generator for causing the biological culture solution extracted from the culture tank to contain micro-nano bubbles formed from air with an increased oxygen content, and a pipeline for returning the biological culture solution containing the micro-nano bubbles to the culture tank (Patent Document 4). When an oil-in-water suspension containing cell fragments was placed in the culture tank of the biological reactor described in Patent Document 4 and microbubbles were generated, the micelles that passed through the microbubble generator became even finer, leading to further emulsification. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-162499 A [Patent Document 2] JP 2016-208909 A [Patent Document 3] JP 2008-49243 A [Patent Document 4] International Publication No. 2017 / 017998 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a novel method for oil-water separation of an oil-in-water suspension and an oil-water separation apparatus. [Means for solving the problem]

[0007] The means for solving the problems of the present invention are as follows. 1. Contacting an oil-in-water suspension with water, which may contain microbubbles, such that the suspension-rich phase is on the top and the water-rich phase is on the bottom; Supplying new microbubbles to the water-rich phase so as not to uniformly mix the suspension-rich phase with the water-rich phase; A method for oil-water separation, characterized by floating up microbubbles that adsorb micelles in the suspension. 2. An oil-water separation method as described in 1, characterized in that the suspension contains crushed cell material. 3. An oil-water separation method described in 1. or 2., characterized in that the water is a salt solution having a concentration of 1% by weight or more. 4. The oil-water separation method described in 3., characterized in that the aqueous solution is a saline solution. 5. An oil-water separation method described in any one of 1. to 4., characterized in that the microbubbles have a number-average diameter of 10 μm or more and less than 100 μm. 6. An oil-water separation method described in any one of 1. to 5., characterized in that the total liquid volume does not increase with the supply of new microbubbles. 7. A separation tank that contains an oil-in-water suspension and water that may contain microbubbles, with the suspension-rich phase at the top and the water-rich phase at the bottom; a microbubble generator for generating microbubbles to be supplied to the separation tank; Equipped with The microbubble generator is installed so that the generated microbubbles are supplied to the water-rich phase, and the inside of the separation tank is not stirred so as to be uniform when the microbubbles are generated. 8. An oil-water separation apparatus as described in 7., characterized in that the microbubble generator is installed in a circulation piping whose extraction port and supply port are both connected below the separation tank. 9. An oil-water separation apparatus as described in 7., characterized in that the microbubble generator is a micropore type that blows out microbubbles from a porous body installed below the separation tank. Effect of the Invention

[0008] The oil-water separation method and oil-water separation device of the present invention enable efficient separation of oil from an oil-in-water suspension. In the oil-water separation method and oil-water separation device of the present invention, the micelles of the oil-in-water suspension may collapse on the liquid surface to form an oil layer, in which case the oil can be recovered very easily. Even if the micelles do not collapse, they accumulate in high concentration near the liquid surface, so the amount of hydrophobic solvent or chemical required to separate the oil from the recovered micelles can be reduced. The oil-water separation method and oil-water separation device of the present invention can be applied to an oil-in-water suspension containing crushed cells, thereby enabling efficient recovery of high-value-added lipophilic components. The oil-water separation method and oil-water separation device of the present invention can efficiently separate and recover oil from crushed cells (plant cells, yeast) that have cell walls and are prone to becoming oil-in-water suspensions because high energy is required to crush the cells. By making the water denser than the suspension, it is possible to reduce mixing between the water-rich phase and the suspension-rich phase, thereby efficiently supplying microbubbles to the suspension-rich phase located above and preventing malfunctions caused by micelles coming into contact with the microbubble generator. [Brief description of the drawings]

[0009] [Figure 1] A diagram showing an overview of a first embodiment of an oil-water separation device of the present invention. [Diagram 2] A diagram showing an overview of a second embodiment of the oil-water separation device of the present invention. [Diagram 3] Graph showing the change in transparency over time in Experiment 1. [Figure 4] Graph showing the change in transparency over time in Experiment 2. [Diagram 5]FIG. 11 is a diagram showing the appearance of each test example at a specified time in Experiment 2. [Figure 6] FIG. 11 shows the appearance near the liquid surface of each test example in Experiment 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] ·Oil / water separation method The oil-water separation method of the present invention comprises: contacting an oil-in-water suspension with water, which may contain microbubbles, such that the suspension-rich phase is on the top and the water-rich phase is on the bottom; New microbubbles are supplied to the water-rich phase located below so that the suspension-rich phase and the water-rich phase are not mixed uniformly, The microbubbles that adsorb the micelles in the suspension are caused to float.

[0011] The oil-in-water suspension to be treated by the oil-water separation method of the present invention is not particularly limited, and may be any of industrial wastewater, washing wastewater from a car wash or the like, wastewater from a restaurant or the like, but it is preferable that the suspension be cell fragments, since the oil recovered by oil-water separation contains lipophilic components with high added value.

[0012] The oil-water separation method of the present invention will be explained below step by step using crushed cell material as an example. First, the cultured cells are disrupted. The cells to be disrupted are not particularly limited, and may be any microorganism such as animal cells, plant cells, mushrooms, yeast, fungal cells such as Fusarium and Mucor, and oil-producing algae such as Cyanobacterium, Euglena, Aurantiochytrium, and Labyrinthula. Among these, cells with cell walls that are easily emulsified (plant cells and fungal cells (especially yeast)) are preferred because strong shear force is required during disruption. In addition, by increasing the cell concentration of the culture solution by centrifugation, membrane concentration, etc. before cell disruption, the amount of cells to be subjected to the disruption process can be reduced, which contributes to reducing the capital investment required for purification after the cell disruption.

[0013] The method of disrupting cells is not particularly limited, and may be a combination of one or more of known methods such as a method of applying shear force using a high-pressure homogenizer or ultrasonic homogenizer, a method of applying a pulsed electric field, and non-mechanical methods such as freeze-drying, reduced pressure, osmotic shock, and liquid vibration by ultrasonic irradiation. In the case of cells having a cell wall, it is preferable to disrupt the cells in a liquid in which one or more of cell wall decomposing enzymes, fine bubbles (ultra-fine bubbles or microbubbles, air, nitrogen, or carbon dioxide depending on the target process), and carbon dioxide are dissolved in order to promote the disruption of the cell wall. In the case of microorganisms having a cell wall, when extracting intracellular valuables, it is also preferable to extract intracellular valuables from the cells by adding one or more of cell wall decomposing enzymes, fine bubbles (ultra-fine bubbles or microbubbles, air, nitrogen, or carbon dioxide depending on the target process), carbon dioxide, and organic solvents such as hexane in addition to the above disruption method. The oil-in-water suspension containing the disrupted cell material can be used as is, but it is preferable to remove solids by filtration, centrifugation or the like after disruption.

[0014] An oil-in-water suspension containing cell fragments is contacted with water (hereinafter also referred to as MB water) which may contain microbubbles, with the suspension-rich phase on the top and the water-rich phase on the bottom. The suspension-rich phase means a phase in which the proportion of suspension is greater than the proportion of MB water, and the water-rich phase means a phase in which the proportion of MB water is greater than the proportion of suspension. The suspension-rich phase and the water-rich phase can be easily distinguished from each other by turbidity, transparency, color tone, concentration of one or more components, etc.

[0015] The oil-in-water suspension and MB water can be mixed uniformly. In the present invention, the oil-in-water suspension and MB water are gently poured into one another so that they do not mix uniformly but form a suspension-rich phase and a water-rich phase. When pouring one liquid from above, it is preferable to gently pour the suspension into the MB water so that the water-rich phase tends to be at the bottom. When pouring one liquid into the other liquid, it is preferable to pour the MB water little by little from near the bottom of the suspension so that the suspension-rich phase tends to be at the top.

[0016] Microbubbles are bubbles with a diameter of 1 μm or more and less than 100 μm (see ISO / TC281). The number-average diameter of newly supplied microbubbles and the microbubbles contained in water that may contain microbubbles from the beginning is preferably 10 μm or more and less than 100 μm. When the number-average diameter of the microbubbles is 10 μm or more and less than 100 μm, the adsorption of the micelles is excellent and the floating speed of the microbubbles is appropriate. In addition, in order for the microbubbles to be efficiently adsorbed to the micelles, the number-average diameter of the microbubbles is preferably equal to or less than the number-average diameter of the micelles. The number-average diameter of the microbubbles is more preferably 80% or less of the number-average diameter of the micelles, more preferably 60% or less, and even more preferably 50% or less. The number-average diameter of the microbubbles and micelles can be calculated by measuring the diameters of 1,000 or more microbubbles or micelles by image analysis, laser diffraction scattering, electrical detection zone method, resonance mass measurement method, optical fiber probe method, etc., and averaging the measured diameters.

[0017] New microbubbles are supplied to the water-rich phase located below so that the suspension-rich phase and the water-rich phase do not mix uniformly. In the oil-water separation method of the present invention, new microbubbles are supplied to the water-rich phase located below, but the microbubbles are supplied so that the suspension-rich phase and the water-rich phase are not mixed uniformly due to the liquid flow accompanying the supply of the microbubbles. By supplying the microbubbles in this manner, contact between the microbubble generator and the micelles can be prevented, and problems such as enlargement of the microbubbles caused by contact of the micelles with the microbubble generator and further progress of emulsification can be prevented. In order to prevent contact between the microbubble generator and the micelles, the density of the micelles (pcs / L) in the water-rich phase is preferably 50% or less of the density of the micelles (pcs / L) in the suspension-rich phase, more preferably 30% or less, still more preferably 10% or less, still more preferably 5% or less, still more preferably 3% or less, and still more preferably 1% or less.

[0018] Microbubbles rise due to buoyancy, passing from the water-rich phase through the suspension-rich phase to reach the liquid surface. In the process of rising, micelles are adsorbed to the microbubble surface, and the micelles reach the liquid surface together with the microbubbles. In the method of the present invention, new microbubbles are supplied to the water-rich phase, so even if the number of micelles in the suspension-rich phase is large and the initial supply of microbubbles is insufficient, the newly supplied microbubbles can adsorb the micelles, and the micelles in the suspension-rich phase can be efficiently collected at the liquid surface.

[0019] The water used for the microbubble water is not particularly limited, and tap water, industrial water, deionized water, salt solution, etc. can be used. Among these, a salt solution with a concentration of 1% by weight or more is preferable because the number-average diameter of the microbubbles becomes small. The solute of the salt solution is not particularly limited, but from the viewpoint of safety, table salt (sodium chloride), potassium chloride, calcium chloride, magnesium chloride, etc. are preferable, and table salt is more preferable because it is inexpensive. The concentration of the salt solution is preferably 3% by weight or more, more preferably 5% by weight or more, and even more preferably 10% by weight or more. In addition, it is expected that MB water formed from the salt solution will be difficult to mix with the suspension.

[0020] The gas that forms the microbubbles is not particularly limited, and can be air, nitrogen gas, carbon dioxide gas, etc. From the viewpoint of cost, air is preferable, and when it is desired to prevent oxidation, it is preferable to use nitrogen gas.

[0021] Although the method of supplying microbubbles is not particularly limited, if the total amount of liquid increases with the supply of new microbubbles, the cost required for post-treatment will increase. Therefore, when supplying new microbubbles, it is preferable that the total amount of liquid does not increase. Examples of methods for supplying new microbubbles without increasing the total amount of liquid include a method of releasing microbubbles from a porous body installed in the water-rich phase and a method of installing a microbubble generator in the middle of a circulation pipe that circulates the liquid in the water-rich phase.

[0022] According to the oil-water separation method of the present invention, micelles adsorbed on microbubbles rise to the surface of the liquid, but the oil droplets may coalesce on the surface of the liquid to form an oil layer. Although the mechanism is unclear, the present inventors speculate that when the microbubbles adsorbing the micelles burst, the molecular arrangement at the interface of the micelles is disturbed by the stimulation, and the oil flows out from the disturbed area. When an oil layer is formed on the surface of the liquid, the oil containing the lipophilic component can be easily recovered, and the recovered oil can be dried and refined by a known method to obtain the lipophilic component. Even if an oil layer is not formed on the liquid surface, micelles accumulate in high concentration near the liquid surface, so that the oil containing the lipophilic component can be separated by recovering the liquid near the liquid surface and extracting it using a conventionally known method. Since the recovered liquid contains micelles in high concentration, the amount of non-polar organic solvents and chemicals used for oil-water separation and oil washing can be reduced.

[0023] ·Oil water separator The oil-water separation apparatus of the present invention comprises a separation tank that accommodates an oil-in-water suspension and water that may contain microbubbles, with the suspension-rich phase being at the top and the water-rich phase being at the bottom; a microbubble generator that generates microbubbles to be supplied to the separation tank; Equipped with This microbubble generator is installed so that the generated microbubbles are supplied to a water-rich phase located at the bottom inside the separation tank, and the inside of the separation tank is not stirred so as to be uniform when the microbubbles are generated. The oil-water separation method of the present invention can be suitably carried out by the oil-water separation device of the present invention.

[0024] FIG. 1 shows an oil-water separation device 10 according to a first embodiment of the present invention. The oil-water separation device 10 of the first embodiment includes a separation tank 1, a circulation pipe 2 connected to the separation tank 1, a pump P provided midway along the circulation pipe 2, and a microbubble generator 3. Separation tank 1 contains an oil-in-water suspension and water (MB water) that may contain microbubbles, with the suspension-rich phase at the top and the water-rich phase at the bottom. Separation tank 1 has an injection pipe (not shown) that is provided so that the suspension and MB water can be injected without being mixed uniformly. The injection pipe may be a single pipe that can inject both the suspension and MB water, or two pipes that inject them separately. The supply port of the injection pipe on the separation tank 1 side is preferably formed so that the liquid can be injected horizontally or downward to suppress agitation of the liquid in the vertical direction.

[0025] The separation tank 1 can be used only for oil-water separation, or can also be used for, for example, cell crushing, cell cultivation, etc. In addition to the injection piping, the separation tank 1 can be equipped with piping for extracting the layer containing a high concentration of oil and the water layer after oil-water separation, as well as devices, piping, sensors, etc. according to the application.

[0026] The circulation pipe 2 connects an extraction port 21 and a supply port 22 provided in the separation tank 1. A pump P and a microbubble generator 3 are provided in the circulation pipe 2, and the liquid extracted from the extraction port 21 becomes a liquid containing microbubbles and is supplied into the separation tank 1 from the supply port 22. The extraction port 21 and the supply port 22 are preferably provided at the lower part of the separation tank 1, and when the depth direction of the separation tank 1 is expressed as 0% at the bottom surface and 100% at the top surface, they are preferably provided at a position of 0 to 50%, more preferably at a position of 0 to 30%, even more preferably at a position of 0 to 20%, even more preferably at a position of 0 to 10%, and even more preferably at a position of 0 to 5%. By providing the circulation pipe 2 at the lower part of the separation tank 1, the water-rich phase contained in the separation tank 1 can be circulated preferentially, and it is possible to prevent micelles from entering the circulation pipe 2 and the micelles that have passed through the microbubble generator 3 from being finely divided, which causes further emulsification. The direction of the extraction port 21 is not particularly limited, but it is preferable that the supply port 22 is provided horizontally or horizontally downward. By forming the supply port 22 in a direction downward from the horizontal direction, it is possible to prevent the liquid in the separation tank 1 from being agitated vertically by the supply of the liquid containing microbubbles.

[0027] FIG. 2 illustrates a second embodiment of an oil-water separator 20 of the present invention. The oil-water separation device 20 of the second embodiment has the same configuration as the oil-water separation device 10 of the first embodiment, except that a porous body 4 is installed as a microbubble generator near the bottom surface of the separation tank 1. In the oil-water separation device 20 of the second embodiment, the same members as those in the oil-water separation device 10 of the first embodiment are denoted by the same reference numerals.

[0028] The porous body 4 is preferably provided at a position of 0 to 50% in the depth direction of the separation tank 1, more preferably at a position of 0 to 30%, even more preferably at a position of 0 to 20%, even more preferably at a position of 0 to 10%, and even more preferably at a position of 0 to 5%. By providing the porous body 4 below the separation tank 1, it is possible to prevent the suspension rich phase 11 contained in the separation tank 1 from contacting the porous body 4, and it is possible to prevent the porous body 4 from being covered with oil in the micelles. EXAMPLES

[0029] "Experiment 1" Palm oil and water (tap water) were mixed at palm oil concentrations of 0.1 wt%, 0.5 wt%, and 1 wt%, and stirred at 5000 rpm for 1 minute using a homogenizer (OLLIRG, Dispersion and Homogeneous Emulsifier Mixer) to obtain a water-in-oil suspension. Water (tap water) was supplied to a small test microbubble generator (manufactured by Nishiyama Pump Service, a combination of pressurized dissolution method and swirling method) to obtain microbubble-containing water with an average diameter of 53.5 μm and a microbubble concentration of approximately 6,500 bubbles / ml.

[0030] 1 L of each suspension was placed in an acrylic tank with a black acrylic plate installed on the back, and 4 L of microbubble water was gently added from near the bottom of the tank so as not to mix the suspension and microbubble water evenly. The water depth at the time when the microbubble water was added was 30 cm. Immediately after the addition of the microbubble water was set as 0 seconds, and images were taken with a digital camera at each specified time. The images were converted to 8-bit grayscale using image processing software (Image J, free software) and quantified in 256 gradations (gradation 0 is black, gradation 255 is white). The average brightness was calculated for an area of ​​150 pixels horizontally and 75 pixels vertically at a position 25 cm from the bottom. Since the water does not become completely transparent or completely suspended, the transparency was calculated from the brightness value, with a gradation of 220 in the image of tap water (transparent, with the black color of the back visible) as 100% transparency and a gradation of 70 in the image of a 1 wt% palm oil suspension (cloudy white). The change in transparency over time is shown in Figure 3.

[0031] At palm oil concentrations of 0.1wt% and 0.5wt%, transparency increased over time, and at a palm oil concentration of 0.1%, the transparency increased from 33% at the start to 53% after 300 seconds. In contrast, at a palm oil concentration of 1wt%, transparency barely changed, reaching 35% after 300 seconds. This is thought to be because at a palm oil concentration of 1wt%, the number of microbubbles was insufficient compared to the number of micelles in the suspension, and the micelles that were not adsorbed by the microbubbles remained without floating up.

[0032] "Experiment 2" The experimental procedure was the same as in Experiment 1, except that the measurement height was changed to 5 cm from the bottom surface. 25 g of salt was dissolved in 100 ml of water to prepare a 20% salt solution. Microbubble-containing water made with salt water (MB (salt water) water), MB water, and salt water were added to a suspension with a palm oil concentration of 0.5 wt%, and the transparency was measured at specified intervals. MB (salt water) water had a number-average diameter of about 18 μm, with a mode of 10 to 20 μm, and MB water had a number-average diameter of about 24 μm, with a mode of 20 to 30 μm. Since the small microbubble generator used for the test was not of the circulation type, the transparent part at the bottom was extracted with a syringe 240 seconds and 480 seconds after adding MB (salt) water, and the same amount of new MB (salt) water as that extracted was gently poured in from near the bottom of the tank so as not to mix uniformly with the suspension, thereby artificially supplying new microbubbles continuously (MB (salt) water_continuous). Figure 4 shows the change in transparency over time, and Figure 5 shows photographs of saline water, MB water, and MB (salt) water after 240 seconds, and MB (salt) water_continuous after 1080 seconds. In Figure 4, for MB (salt) water_continuous, the time required from the start of extraction to the end of adding new MB water salt is subtracted, so that the time is shown as continuous.

[0033] The transparency of the saline solution remained almost constant, and oil-water separation was not promoted. Compared to MB water, MB water had a higher transparency. This is thought to be because the microbubbles became smaller when salt water was used, making them easier to adsorb to micelles. In addition, the transparency of both MB water and MB water increased and then decreased. This is thought to be due to the progress of mixing of the suspension and MB water / MB water. When MB water (salt water) was continuously supplied as a simulation, the transparency increased after new microbubbles were supplied. When new MB water / salt water was supplied, the transparency decreased, but this was due to partial mixing of the suspension and the newly supplied MB water / salt water. The effect of the decrease in transparency due to mixing during supply was removed, and the data was connected to form MB water (salt water)_continuous (assumption), shown by the dotted line in Figure 4, and the transparency after 1080 seconds was 73%. This confirmed that supplying new microbubbles can promote oil / water separation.

[0034] "Experiment 3" The culture solution of Aurantium cerevisiae (containing fatty acids) was heat-treated to kill the bacteria, and then it was crushed with a homogenizer (OLLIRG, Dispersion and homogenization emulsifier mixer). After centrifuging, the supernatant was collected, and the collected supernatant was made into a water-in-oil suspension. 50 ml of microbubble-containing water (number-average diameter: approximately 24 μm, mode: 20-30 μm) or water (tap water) was added to a 100 ml beaker, and 50 ml of a water-in-oil suspension (supernatant) was gently added thereto and allowed to stand.

[0035] Figure 6 shows the appearance of the liquid surface 5 minutes after the suspension was added. When MB water was added, an oil layer formed on the liquid surface after 5 minutes. In contrast, when water (tap water) was added, oil droplets were observed on the liquid surface after 5 minutes, but no oil layer was formed and the amount of oil was small. It was confirmed that the micelles in the suspension accumulate at high density at the top due to the microbubbles, and that the micelles may collapse and form an oil layer. [Explanation of symbols]

[0036] Oil / water separator 10, 20 Separation tank 1 Suspension rich phase 11 Water-rich phase 12 Circulation piping 2 Extraction port 21 Supply port 22 Microbubble generator 3 Pump P Porous body 4

Claims

1. contacting an oil-in-water suspension with water, which may contain microbubbles, such that the suspension-rich phase is on the top and the water-rich phase is on the bottom; Supplying new microbubbles to the water-rich phase so as not to uniformly mix the suspension-rich phase with the water-rich phase; A method for oil-water separation, characterized by floating up microbubbles that adsorb micelles in the suspension.

2. 2. The oil-water separation method according to claim 1, wherein the suspension contains crushed cell material.

3. 3. The oil-water separation method according to claim 1, wherein the water is a salt solution having a concentration of 1% by weight or more.

4. The oil-water separation method according to claim 3, characterized in that the aqueous solution is a saline solution.

5. 3. The oil-water separation method according to claim 1, wherein the microbubbles have a number-average diameter of 10 μm or more and less than 100 μm.

6. The oil-water separation method according to claim 1 or 2, characterized in that the total liquid volume does not increase with the supply of new microbubbles.

7. A separation tank that contains an oil-in-water suspension and water that may contain microbubbles, with the suspension-rich phase at the top and the water-rich phase at the bottom; a microbubble generator for generating microbubbles to be supplied to the separation tank; Equipped with The microbubble generator is installed so that the generated microbubbles are supplied to the water-rich phase, and the inside of the separation tank is not stirred so as to be uniform when the microbubbles are generated.

8. The oil-water separation apparatus according to claim 7, characterized in that the microbubble generator is installed in a circulation piping whose extraction port and supply port are both connected below the separation tank.

9. The oil-water separation apparatus according to claim 7, characterized in that the microbubble generator is a micropore type that blows out microbubbles from a porous body installed below the separation tank.

Images