JPH08332304A - Oil-water separation method and apparatus - Google Patents

Abstract

PURPOSE: To inexpensively, efficiently and continuously separate oil and water by passing an aq. washing soln. containing an oil component through a packed bed composed of a fibrous packed material on which sedimented molecular association matter of a low cloud point nonionic surfactant of which the cloud point temp. is within a specific range is supported as ascending streams. CONSTITUTION: An aq. washing soln. is passed through a cartridge 3 packed with a fibrous packing material 4 on which sedimentation molecular association matter of a low clound point nonionic surfactant of which the cloud point temp. is within a range of 20-40 deg.C is supported as ascending streams from an aq. washing soln. tank 1 using a liquid sending pump 2 and the oil particles in the aq. washing soln. are bonded to the packed bed to be, grown into coarse particles. The aq. washing soln. issued from the cartridge 3 is introduced into an oil separation tank 9 from a washing soln. inlet 5 to be stagnated therein. Thereafter, the aq. washing soln. is allowed to flow out of the washing soln. outlet 6 provided to the lower part of the oil separation tank 9 to be returned to the aq. washing soln. tank 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stains (oil, dust or burrs) from a product or an intermediate product in the process of manufacturing an industrial product (hereinafter also referred to as "workpiece") such as a metal part, a semiconductor wafer, glass or liquid crystal. Etc.) for cleaning and removing, in particular, oil removal technology.

[0002]

2. Description of the Related Art Since it has been confirmed that chlorine-based organic solvents such as CFCs and trichloroethane, which have been widely used as industrial detergents, are ozone depleting substances, they were discontinued by international agreement by 1995. . In that situation,
There is an urgent need to develop CFC / trichloroethane alternative cleaning agents, such as water-based cleaning agents that contain surfactants and alkalis as main components, semi-water-based cleaning agents that combine water with an organic solvent such as alcohol or glycol ether, and hydrocarbon-based cleaning agents. Non-aqueous detergents represented by solvents are becoming mainstream. However, in the case of non-aqueous cleaning agents, the cleaning cost is high because they are cleaned with the cleaning agent itself, and most of them are flammable substances, so the cleaning equipment needs explosion-proof specifications and is expensive, or increases in size. I have a difficulty that I can not do it.

On the other hand, in the case of water-based and semi-water-based systems, especially water-based systems, since the cleaning agent is diluted with a large amount of water before use, the running cost is low, and since it is not a dangerous substance, a cleaning device using it is large. It is easy to commercialize and is relatively inexpensive.
However, using a large amount of water also requires a water treatment system capable of coping with oil-water separation of a large amount of water-based cleaning liquid and wastewater treatment of rinse water in the cleaning system. For example, in the case of cleaning a work using a water-based cleaning liquid, dirt such as oil content from the work is gradually accumulated in the water-based cleaning liquid along with the cleaning, and the cleaning power of the water-based cleaning liquid is reduced. Therefore, in order to reduce the drainage amount of the water-based cleaning liquid and extend the service life of the water-based cleaning liquid while maintaining the cleaning power of the water-based cleaning liquid, it is necessary to constantly separate and remove dirt such as oil from the water-based cleaning liquid. Conventionally, oil-water separation methods for water-based cleaning liquids include emulsion breakage / float separation methods that use chemicals such as emulsion breakers, electrostatic separation methods, coalescer methods that promote coalescence and coarsening of oil particles, and microfiltration membranes or limiters. There is a membrane separation method using an outer filtration membrane.

However, each of these conventional techniques has problems. For example, in the emulsion destruction / floating separation method using an emulsion breaker, there is a problem that the water-based cleaning liquid after oil separation loses its cleaning power and cannot be reused. Further, in the electrostatic separation method and the general coalescer method, the oil-water separation effect is small when the oil content in the aqueous cleaning liquid exists as fine emulsion particles. In the microfiltration membrane and ultrafiltration membrane methods, the detergent component is removed at the same time as the oil component, and there are problems that it cannot be reused and that the device is expensive. When the shower cleaning of the work is performed using the water-based cleaning liquid, the oil content attached to the work is brought into the water-based cleaning liquid in an emulsified state by the emulsifying power of the water-based cleaning liquid and the mechanical force of the shower. Usually, the oil component in such an emulsified state is a fine one having an average particle size of several μm to several tens of μm. In this state, oil-water separation is carried out by a flotation separation method utilizing the difference in specific gravity between the oil component and the water-based cleaning liquid. It is practically impossible to do. As a solution to this problem, there is the coalescer method that can coarsen the oil particles.

The coalescer method is a method in which the liquid is passed through a packed bed of granules or fibers before introducing the liquid for separating oily water into the oil flotation tank. It is an oil-water separation method that promotes floating separation of oil components in an oil flotation tank by coarsening particles. However, in the coalescer method, as described above, the oil-water separation effect is small when the oil content in the cleaning liquid exists as fine emulsion particles. Among the conventional coalescer methods, Japanese Patent Laid-Open No.
As disclosed in JP-A-315681, a cartridge (that is, a packed layer) simply filled with inorganic fibers or an aggregate thereof, or hydroxide fine particles such as aluminum hydroxide on the surface of the inorganic fibers or the aggregate. There is a known technique in which a cartridge filled with a carrier carrying a is used for oil-water separation of an aqueous cleaning liquid.

[0006]

However, in this known technique, the effect of separating oil and water is small when a cartridge not filled with hydroxide fine particles is used. On the other hand, when a cartridge filled with a large amount of hydroxide fine particles is used, the oil-water separation effect is improved, but there is a problem that the pressure loss of the cartridge is large and clogging easily occurs. In the case of using a cartridge filled with hydroxide fine particles such as aluminum hydroxide, aluminum hydroxide is dissolved in a water-based cleaning liquid having a pH of 9.0 or more to be separated into oil and water, and the performance of the cartridge is deteriorated. There is. Furthermore, the process of manufacturing the cartridge is complicated, and the salt of the reaction product generated in the process of manufacturing the cartridge and unreacted trace amount of filled metal ions (for example, Al ³⁺ when filling with aluminum hydroxide) are sufficiently washed with water. Therefore, there are also problems such as increased manufacturing costs. The present invention relates to the development of a low-cost and efficient continuous oil-water separation method and an apparatus thereof that overcomes the above-mentioned problems of the conventional art.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors have found that a filling layer filled with a fibrous filler such as a fiber or an aggregate of fibers has a cloud point temperature in the range of 20 to 40 ° C. An aqueous cleaning solution containing oil is upwardly flowed into a packed bed having a fibrous packing carrying a settling molecular association of a low clouding point nonionic surfactant (hereinafter also referred to as a low clouding point nonion) It was found that the oil particles in the water-based cleaning liquid can be adhered to the filling layer and coarsened by passing through the system in the above method, and further, in the filling layer filled with the fibrous filling, a low cloud point nonion The aqueous solution of the surfactant is heated to a temperature higher than the cloud point temperature and then passed through, and the sedimentary molecular association of the low cloud point nonionic surfactant is preliminarily supported on the surface of the fibrous packing. The inventors of the present invention have found that it is possible to achieve the present invention.

The above problems can be solved by the method for separating oil and water and the apparatus for separating oil and water according to the present invention. That is, the oil-water separation method of the present invention comprises (1) a fibrous packing in which a surface of the surface of the low-clouding-point nonionic surfactant having a clouding point temperature in the range of 20 ° C to 40 ° C is used as a settling molecular association. An aqueous cleaning liquid containing oil is passed through the packed bed having a substance in an upward flow to coarsen oil particles on the fibrous packing, and an aqueous cleaning liquid containing coarse oil particles from the packed bed is obtained. Is introduced into an oil / water separation tank to separate an oil component. Further, the oil-water separator of the present invention has (2) a cloud point temperature of 20 ° C.
An oil / water separator comprising a packed bed having a fibrous packing carrying a settling molecular associate of a low cloud point nonionic surfactant in the range of -40 ° C, or
Preferably, (3) the oil-water separator according to (2) above, wherein the packed bed is a cartridge type. Further, the packed bed having the fibrous packing to be installed in the oil-water separator of the present invention,
(4) A low cloud point nonionic surfactant having a cloud point temperature in the range of 20 ° C. to 40 ° C. is heated to the cloud point temperature or higher and passed through the packed bed having the fibrous filler. In the method for adjusting a packed layer, it is preferable to form a packed layer having an oil particle coarsening function by a method of supporting a sedimentable molecular association product of the low cloud point nonionic surfactant on the surface of the fibrous packing. is there.

An aqueous solution of a low cloud point nonionic surfactant is heated to a temperature higher than the cloud point temperature and then passed through a packed bed filled with the fibrous filler such as the fiber or the aggregate of fibers, By preliminarily supporting the precipitating molecular association of the low cloud point nonionic surfactant on the surface of the fibrous packing, the performance as a coalescer of the packing layer was remarkably improved. In the present invention, as its skeleton, the oil particles can be sufficiently coarsened on the supported molecular association, so that the oil flowing out in the upward flow has good separability, and the volume of the oil flotation tank does not pass. A size having a residence time of 20 minutes or less with respect to the flow rate of the water-based cleaning liquid to be liquid is sufficient.

The nonionic surfactant dissolves in water at a cloud point temperature or lower, but is insoluble at the cloud point temperature or higher and becomes a precipitating molecular associate. The present invention utilizes this property. That is, after the water in which a predetermined amount of the low cloud point nonionic surfactant according to the present invention is dissolved is heated to a cloud point temperature or higher to convert the low cloud point nonionic surfactant into a sedimentable molecular aggregate, Alternatively, the performance as a coalescer of the cartridge is remarkably improved by passing water through the cartridge filled with the aggregate of fibers and adhering it to the surface of the fibers. Since the normal temperature of the washing liquid is 40 to 70 ° C., the low cloud point nonionic surfactant can be maintained as a precipitating molecular associate on the surface of the fiber. Of course, in a special situation where the temperature condition of the cleaning liquid is higher than this, the cleaning liquid may be heated. It is not certain that the method of supporting the sedimentation molecular association of the low cloud point nonionic surfactant on the surface of the fiber has the function of coarsening oil particles, but preventing the wall flow of the cartridge, Increasing the contact surface area between the oil and the surface-active agent sedimentation molecule association, and improving the action of the oil particles to aggregate with each other from the active agent-covered oil content particles on the surface-active agent sedimentation molecule association It is possible.

The low cloud point nonionic surfactant to be used may be any one having a cloud point temperature in the range of 20 to 40 ° C., but specifically, it is a polyoxyethylene alkylphenyl ether type, Examples thereof include polyoxyethylene alkyl ether type, polyethylene glycol type, sorbitan fatty acid ester type, polyoxyethylene sorbitan fatty acid ester type, and pluronic type.

The cloud point temperature of the low cloud point nonionic surfactant is more preferably in the range of 25 to 30 ° C. Also, the amount of low cloud point nonionic surfactant used is
The ratio of the low cloud point nonionic surfactant may be 0.5 to 1.0 liter per 10 liters of the packed layer of the fiber or the fiber aggregate. The material and the kind of the fiber according to the present invention are not limited in material and kind, but an aggregate of fine inorganic fibers such as rock wool, slag wool and ceramic fiber is preferable.

[0013]

The cloud point temperature is 20 to 40 ° C., preferably 25 to 3
Using a low cloud point nonionic surfactant (low cloud point nonionic surfactant) in the range of 0 ° C., the cartridge volume 1
The low cloud point nonionic surfactant in an amount corresponding to the ratio of 0.5 to 1.0 liter to 0 liter has a concentration of 2%.
Dissolve in water to a certain extent. Approximately 50
After heating to 0 ° C., water is passed through the cartridge to preliminarily support the low cloud point nonionic surfactant, which has become a precipitating molecular association, on the surface of the fiber or the fiber aggregate filled in the cartridge. Of course, the oil particle coarsening layer does not have to be of the cartridge type, but if the cartridge type is used, a cartridge supporting the settling molecule associate of the low cloud point nonionic surfactant can be prepared in advance. Handling is extremely good. By passing the aqueous cleaning liquid through the cartridge thus manufactured, the oil particles in the aqueous cleaning liquid are coarsened. Then, by introducing an aqueous cleaning liquid containing coarsened oil particles into the oil flotation tank, the oil can be easily floated and separated. Here, the volume of the oil flotation tank is sufficient to have a residence time of 20 minutes or less with respect to the flow rate of the cleaning liquid to be passed.

[0014]

EXAMPLES The oil-water separation method of the present invention will be specifically described below with reference to examples. However, the following example is one example of the oil-water separation method of the present invention, and the present invention is not limited thereto.

Example Here, a 5% solution of a commercially available water-based cleaning agent was used as a cleaning solution for an oil-water separation test. The pH of the aqueous cleaning solution is 9.8.
Met. Further, a typical non-water-soluble cutting oil is used as the oil content to be separated, and the oil-water separation device of the present invention used in the example in which the initial concentration of the oil content in the water-based cleaning liquid is 2% is shown in FIG. Illustrated in. In FIG. 1, 200 liters of the water-based cleaning liquid was prepared in the water-based cleaning liquid tank 1 and the liquid temperature was adjusted to 6
It was kept at 0 ° C. It has been confirmed that such an aqueous cleaning liquid has the maximum cleaning power at 60 ° C. Next, 4 liters of oil was added to the cleaning liquid so that the oil concentration was 2%. In order to make the added oil component a stable emulsified state, the washing liquid was stirred for 30 minutes at a flow rate of 15 liters / minute using a casquette type pump of 3600 rpm. as a result,
A very stable emulsified state was obtained in which the average particle size of the oil particles in the washing liquid was 2.5 μm.

On the other hand, as the low cloud point nonionic surfactant loaded on the cartridge, a polyoxyethylene alkylphenyl ether type nonionic surfactant having a cloud point temperature of 29 ° C. was used. 1 liter of the nonionic surfactant was dissolved in 50 liter of city water at 14 ° C. Since the water temperature during dissolution was below the cloud point temperature, the solution was transparent. Then
The solution was heated to 50 ° C. with an electric heater before sending the solution to the cartridge. At this time, the solution temperature is 29 ° C.
It began to become cloudy from the point of exceeding. As the cartridge 3, there was used a stainless steel cylinder having an inner diameter of 200 mm and a height of 300 mm filled with 2.8 kg of an aggregate of slag fibers having an average fiber diameter of 4.8 μm (fibrous filler 3). The solution was sent to the cartridge 3 by using the solution sending pump 2 at a flow rate of 3 l / min. Since the water that passed through the cartridge 3 was transparent, it was clear that the cloudy component in the solution, that is, the settling molecular association of the nonionic surfactant was attached to the fiber surface in the cartridge. there were.

The test procedure and test results will be described in detail below. The cartridge 3 filled with the fibrous filler 4 prepared as described above was used to supply 3 L / liter by using the liquid feeding pump 2.
The above-mentioned water-based cleaning liquid is sent from the water-based cleaning liquid tank 1 to the cartridge 3 by an upward flow at a flow rate of a minute, and the fibrous filler 4
The water-based cleaning liquid discharged from the cartridge 3 filled with is introduced into the oil-water separation tank 9 through the cleaning liquid inlet 5, the water-based cleaning liquid is retained in the oil-water separation tank 9, and is caused to flow out from the cleaning liquid outlet 6 at the bottom of the tank, and the outflowing water-based cleaning liquid is discharged. Was returned to the water-based cleaning liquid tank 1. The volume of the oil / water separation tank 9 used here is 36 liters, and the residence time of the aqueous cleaning liquid in the oil / water separation tank 9 is 12 liters.
It was a minute. It should be noted that the time required to complete one cycle of 200 liters of cleaning liquid (referred to as one pass here) is about 67.
It was a minute. Thus, oil-water separation of the water-based cleaning liquid was performed while circulating the water-based cleaning liquid. The amount of oil discharged (the amount of oil 7) in the oil / water separation tank 9, the oil content concentration in the cleaning liquid tank 1, and the average particle diameter of the oil particles in the water-based cleaning liquid before it leaves the cartridge and enters the oil / water separation tank 9 are measured for each pass. The measured values are shown in Table 1.

Comparative Example In order to clarify the effect of the present invention, as a comparative example,
A similar oil-water separation test was carried out using the oil-water separation device shown in FIG. 1 described in the above example except that the polyoxyethylene alkylphenyl ether type nonionic surfactant was not attached to the cartridge 2. The test results are also shown in Table 1 for comparison.

[0019]

[Table 1]

As can be seen from Table 1, the average diameter of the oil particles steadily increased as the number of passes increased, and the sufficiently coarse oil particles were floated and separated in the oil levitation tank. That is, the coalescing action of the cartridge was remarkable. Thus, by using the method according to the present invention, oil-water separation of the aqueous cleaning liquid can be performed. From Table 1, in the case of the comparative example, the particle size of the oil component in the water-based cleaning liquid did not increase, and the oil component did not float at all. That is, the cartridge to which the nonionic surfactant according to the present invention was not attached had almost no coalescing action.

[0021]

INDUSTRIAL APPLICABILITY In the oil-water separation of the water-based cleaning liquid for the purpose of extending the service life of the water-based cleaning liquid, a stable emulsified oil content can be obtained by using the coalescer-based oil-water separation method and apparatus according to the present invention. Oil-water separation can be performed even with the water-based cleaning liquid containing it. The present invention provides a simple and cost-effective method for separating oil / water of an aqueous cleaning liquid and an apparatus therefor.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining oil / water separation by an oil / water separator of the present invention.

[Explanation of symbols]

 1 Water-based cleaning liquid tank 2 Pump 3 Cartridge 4 Fibrous filling 5 Cleaning liquid inlet 6 Cleaning liquid outlet 7 Oil component 8 Oil drain valve 9 Oil-water separation tank

Claims (4)

[Claims] 1. A packing layer having a fibrous packing on the surface of which a settling molecular associate of a low cloud point nonionic surfactant having a cloud point temperature in the range of 20 ° C. to 40 ° C. Is passed through in an upward flow to cause the oil particles to coarsen on the fibrous packing, and the aqueous cleaning solution containing the coarser oil particles from the packed bed is introduced into an oil-water separation tank to remove oil. A method for separating oil and water, characterized in that 2. A packing layer having, on the surface thereof, a fibrous packing having a low cloud point nonionic surfactant having a low cloud point in the range of 20.degree. C. to 40.degree. An oil-water separator characterized by. 3. The oil / water separator according to claim 2, wherein the packed bed is a cartridge type. 4. A low cloud point nonionic surfactant having a cloud point temperature in the range of 20 ° C. to 40 ° C. is heated to above the cloud point temperature and passed through a packed bed having the fibrous packing. Then, a method of preparing a packed bed having a function of coarsening oil particles, comprising causing the surface of the fibrous packing to support a sedimentable molecular association of the nonionic surfactant.