JP3354257B2 - Oil-water separation method and oil-water separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil / water separation method and an oil / water separation apparatus for recovering an oil having a low water content from an oil / water mixture.

[0002]

2. Description of the Related Art In a production process such as food production, textile processing, machining, or petroleum refining, or a waste liquid treatment process, a separation treatment for separating an oil-water mixture into oil and water is also performed as a part of the process. Have been done. Conventionally, specific gravity separation, pressure flotation, centrifugation, adsorption separation, electric methods, and the like have been performed as the above-mentioned separation method, but in recent years, high concentration separation is possible and it is advantageous in terms of energy saving. Na, reverse osmosis,
Attention has been focused on membrane separation methods such as microfiltration and ultrafiltration. As such a membrane separation method of an oil-water mixture, a method using a polymer porous membrane as disclosed in JP-A-54-152680, or a ceramic filter as disclosed in JP-A-1-139107 is disclosed. Is used.

[0003]

In the grinding of metals and ceramics, for example, grinding oil is circulated, but the grinding oil contains a lot of water. In order to use the oil for a long period of time, it is necessary to separate and remove the water in the grinding oil so as not to have a water content (generally about 0.1 vol%) that affects the grinding performance. Such a membrane separation method may be used to recover an oil having a low water content from the oil-water mixture. However, the conventional membrane separation method disclosed in the above publication generally employs an oil-water mixture. This is a technology for recovering water with a low oil content from water. That is, the above-mentioned conventional membrane separation technology utilizes that the speed at the time of permeation through a filtration membrane is greatly different between water and oil due to the difference in viscosity thereof. Since it is larger than oil having a high viscosity, the water content in the permeated liquid is higher than that in the undiluted liquid. Then, since the water having a relatively low oil content is recovered from the undiluted solution, that is, the oil-water mixture, the undiluted solution is concentrated. However, even in the concentrated undiluted solution, the water content is relatively high. In general, it has been generally difficult to recover an oil having a low water content from an oil-water mixture.
Therefore, for example, when the water content of the grinding oil is such that the grinding performance is affected as described above, there is a problem that the grinding oil has no other option than to be treated as a waste liquid.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an oil / water separation method and an oil / water separation apparatus for recovering an oil having a low water content from an oil / water mixture. Is to do.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the oil / water separation method of the present invention is to provide a filter having a first chamber and a second chamber separated by a filtration membrane. An oil-water separation method for recovering oil having a low water content from an oil-water mixture using (a) an oil-impregnation step of previously impregnating the filtration membrane with oil, and (b) an oil-impregnation step Circulating the oil / water mixture through the first chamber of the filter at a predetermined pressure to filter the oil having a low water content through the filtration membrane to the second chamber of the filter. It is in.

[0006]

In this way, the oil is previously impregnated into the filtration membrane prior to the filtration step, so that the pores of the filtration membrane are hardly permeable to water and easily permeable to oil. Therefore, oil having a low water content is recovered through the filtration membrane, as opposed to the conventional membrane separation method. The same effect can be obtained regardless of the degree of impregnation of the filtration membrane with oil, either to the extent that an oil film is formed on the membrane surface or to the extent that oil is filled in the pores.

[0007]

In order to achieve the above-mentioned object, the gist of the oil-water separator of the present invention is to provide a filter having a first chamber and a second chamber separated by a filtration membrane. An oil / water separation system in which an oil / water mixture is circulated to a first chamber of the filter at a predetermined pressure to thereby filter and recover oil having a low water content through the filtration membrane to a second chamber of the filter. An apparatus comprising: (a) an oil supply;
(b) prior to circulating the oil-water mixture to the first chamber, oil introducing means for introducing oil from the oil supply source into the first chamber and impregnating the filtration membrane. is there.

[0008]

In this way, prior to the circulation of the oil-water mixture to the first chamber of the filter, the oil from the oil supply source is transferred to the first chamber of the filter by the oil introducing means. It is introduced and impregnated in the filtration membrane. Therefore, after that, the first mixture is circulated by circulating the oil-water mixture.
As in the invention, an oil having a low water content is recovered as a filtrate. In the present apparatus, as in the first invention, the state of impregnation of the filter membrane with oil is either the degree to which an oil film is formed on the membrane surface or the degree to which oil is filled in the pores. Is also good.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an example of the oil-water separation device of the present invention. In the drawing, a filter 10 has, for example, a cylindrical double structure, and its interior is partitioned into two chambers by a ceramic filter 12. A stock solution inlet 16 provided at one end of the first chamber 14 is connected to a stock solution tank 24 via a supply path 22 having a supply valve 18 and a circulation pump 20, and is provided at the other end. The undiluted solution outlet 26 is connected to the undiluted solution tank 24 via a return path 30 having a return valve 28.
A filtrate outlet 32 is provided at an end of the outer peripheral surface of the filter 10 on the side of the undiluted solution outlet 26, and the other second chamber 34 in the filter 10 is provided with a filtrate outlet valve 36. It is connected to a filtrate tank 40 via a filtrate path 38. The filtrate in the filtrate tank 40, that is, the oil having a low water content,
The liquid is sent to the next step (not shown) by the liquid sending pump 44 via the three-way valve 42 and reused. On the other hand, a filtrate introduction port 46 is provided at the end of the outer peripheral surface of the filter 10 on the side of the undiluted solution introduction port 16, and the second chamber 34 is provided with a backwash path 50 provided with a backwash valve 48. It is connected to the three-way valve 42 through the above. In this embodiment, the ceramic filter 12 corresponds to a filtration membrane.

A three-way valve 52 is provided between the circulating pump 20 and the stock solution tank 24 in the supply passage 22, and the three-way valve 52 is provided with an oil introduction passage 56 having an oil introduction valve 54. An oil tank 58 is connected via the oil tank 58. The three-way valve 52 connects the circulating pump 20 to the stock solution tank 24 or the oil introduction path 56 alternatively. In addition, a glass tube 60 is provided in the middle of the filtrate passage 38 so that the arrival of the oil in the filtrate passage 38 can be confirmed. In the present embodiment, the three-way valve 52 and the oil introduction path 56 correspond to oil introduction means.

The ceramic filter 12 is made of, for example, alumina ceramics, and has a filter membrane having relatively uniform fine pores of any size within a range of, for example, about 0.05 to 3 μm. It is formed in a cylindrical shape for the surface. The filter 10 is configured such that the ceramic filter 12 is fixed in a cylindrical container 62 made of, for example, stainless steel, and the ceramic filter 12 is sealed at its end surface with EP rubber, silicon rubber, or the like. An inner peripheral surface, that is, a filtration membrane, is communicated only with the supply path 22 and the return path 30. Thereby, the second chamber 34 is formed in a closed cylindrical shape. The size of the pores is appropriately selected according to the stock solution to be filtered.

A method for separating water from a grinding oil (raw liquid) containing water by using the oil-water separator configured as described above will be described below. With the three-way valve 52 connected to the oil introduction path 56 to the circulation pump 20, the supply valve 18, the filtrate outlet valve 36 and the oil introduction valve 54 are opened, and the return valve 28 and the backwash valve 48 are closed. I do. Next, when the circulation pump 20 is operated, the oil in the oil tank 58 is sent to the filter 10. At this time, since the return valve 28 is closed, a relatively high pressure is applied to the ceramic filter 12, and the pores of the filtration membrane are impregnated with oil. This impregnation is performed until the oil reaches the inside of the glass tube 60, whereby the oil is surely impregnated into the filtration membrane. In this embodiment, this step corresponds to an oil impregnation step. Thereafter, when the return valve 28 is opened and the three-way valve 52 is switched so that the circulating pump 20 is connected to the stock solution tank 24, the oil-water mixture in the stock solution tank 24 pressurizes the first chamber 14 of the filter 10 at a predetermined pressure. The filtrate, i.e., oil containing no water, is recovered from the filtrate outlet 32 and stored in the filtrate tank 40. Oil / water mixture is in stock solution tank 2
4, the water content is increased by the permeation of the oil through the filtration membrane, the water is returned to the stock solution tank 24, and the oil is repeatedly circulated in the filter 10.

Table 1 shows the results of separating water from grinding oil containing water by the above oil / water separator. The ceramic filter 12 has a diameter of 10 m.
m, a cylindrical filter having a length of 300 mm, formed with a filtration membrane having an average pore diameter of 0.2 μm, and provided with 19 stock solution passages having a diameter of 7 mm and a filtration pressure of 100 kPa and a membrane surface of At a flow rate of 3 m / s, the viscosity of the grinding oil was 2.3 cSt at 30 ° C. The moisture content before and after the filtration was measured with a portable moisture meter (AQUA TEST FINA manufactured by Asano Chemicals Co., Ltd.). As a result, the water content in the filtrate was 0.01% or less in any case of the grinding oil having any water content of 5 to 95 vol%. The detection limit of this moisture meter is 0.01 vol.
%, Which was below the detection limit in each case. In general, in the case of grinding oil, if the water content is 0.1 vol% or less, there is no problem regarding the grinding performance, and even in the case of new oil, the water content may be about 0.05 to 0.08 vol%. From this, it is clear that according to this example, a grinding oil having an extremely low water content can be obtained. For reference, the water content of the filtrate when filtration is performed without performing the oil impregnation step is also shown. The water content of the filtrate is higher than the water content of the stock solution in most cases.

[0015]

[Table 1]

The backwash valve 48 and the backwash path 50 are for cleaning the ceramic filter 12 using oil stored in the filtrate tank 40, and are provided at predetermined intervals. For example, every 24 hours, the circulation pump 20 is stopped, the filtrate outlet valve 36 is closed, the backwash valve 48 is opened, and the three-way valve 42 is connected to the liquid feed pump 44 and the backwash path 50. By switching to the position and operating the liquid feed pump 44 for 10 to 15 seconds, the pressure in the second chamber 34 is made higher than that in the first chamber 14, and the oil flows back from the second chamber 34 to the first chamber 14. Thus, clogging of the ceramic filter 12 is removed.

Here, in this embodiment, the oil tank 5
8 is connected to the supply passage 22 by a three-way valve 52,
The oil is supplied to the filter 10 before the flow of the undiluted solution (that is, filtration), so that the pores of the filtration membrane of the ceramic filter 12 are impregnated with the oil. Then, since the filtration is performed thereafter, the oil easily permeates the pores of the filtration membrane and the water hardly permeates, and the oil having a low water content is recovered as the filtrate. Note that the oil impregnation step does not necessarily have to be performed each time filtration is started, and is unnecessary if the pores of the filtration membrane have been impregnated with oil by the previous operation. Therefore, for example, the oil impregnation step may be performed when a new ceramic filter 12 is used or when the ceramic filter 12 is washed with a chemical or the like.

In this embodiment, the backwash valve 4
8 and the backwash passage 50, the clogging of the ceramic filter 12 is performed by periodically sending oil to the second chamber 34 as described above, and a high filtration flux is provided for a long period of time. Be maintained.

Since the filtration membrane is made of alumina ceramics, if a high filtration flux cannot be obtained even by back washing, the initial filtration flux can be obtained by performing a chemical treatment or a heat treatment. Is recovered and becomes usable, so that high economic efficiency can be obtained.

FIG. 2 is a diagram showing the configuration of another example of the oil introducing means of the present invention. In the present embodiment, the three-way valve 52 of the above embodiment is not used, and the undiluted solution inlet 16 and the supply valve 18 are used.
And a three-way valve 64 is provided between the
6 is provided between the three-way valve 64 and the oil introduction valve 54. In this embodiment, the supply valve 18 and the return valve 28
Is closed, the three-way valve 64 is switched so that the oil introduction path 56 and the undiluted solution introduction port 16 are connected, the oil introduction valve 54 is opened, and the liquid supply pump 66 is operated.
The filtration membrane of the ceramic filter 12 is impregnated with oil. Thereafter, the return valve 28 is opened, and the three-way valve 64 is switched so that the stock solution inlet 16 and the supply valve 18 are connected, and the circulation pump 20 is operated.
The filtrate or oil is recovered. The configuration of the other parts is the same as that of the first embodiment, and the same reference numerals are given and the description is omitted. According to the present embodiment, the distance from the oil tank 58 to the filter 10 can be reduced, and therefore, the amount of oil necessary for impregnating the filter membrane with oil is reduced, and It is possible to reduce the required amount of oil to be prepared for.

FIG. 3 is a view showing the structure of still another oil introducing means. In the present embodiment, a compressor 68 is connected to the three-way valve 64 of FIG.
The oil tank 58 is provided with a branch 70 having an oil introduction valve 54.
Is connected to the oil introduction path 56 via the. In this embodiment, after operating the valve in the same manner as in the second embodiment,
By operating the compressor 68, oil is sent to the filter 10 by compressed air.

FIG. 4 is a view showing the structure of still another oil introducing means. In this embodiment, a piston 72 is used instead of the liquid feed pump 66 used in the second embodiment.
Is provided, and a valve 76 is provided between the oil tank 58 and the cylinder 74. In this embodiment as well, the oil is sent to the filter 10 by operating the piston 72 after operating the valve as in the second embodiment.

While the embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be embodied in still another embodiment.

For example, in the above-described embodiment, a cylindrical alumina ceramic was used as the ceramic filter 12, but a plurality of through holes are provided in the axial direction, and the inner peripheral surface of the through holes is the same as in the embodiment. A cylindrical so-called multi-type filter provided with respective filtration membranes may be used, or another ceramic or resin filtration membrane may be used. In addition, filters made of ceramics have high rigidity so that high filtration pressure can be applied, and because they have high chemical resistance, chemical cleaning is easy, and they have high heat resistance. Therefore, it is most preferable because the temperature of the stock solution can be raised to lower the viscosity to increase the filtration rate, or to incinerate and remove organic clogging. As the material of the ceramics, alumina, zirconia, cordierite, mullite and the like are preferable.

The shape of the filter is not only cylindrical but also
A plate type, a multi type as described above, a honeycomb type or the like is used. The multi-type and the honeycomb type have a relatively large filtration area per unit volume, and can reduce the size of the apparatus.

In order to impregnate the filter membrane with oil, it is not always necessary to provide oil introduction means in the oil-water separator as in the above-described embodiment. For a suitable time to impregnate the oil.

In the above-described embodiment, the case where the present invention is applied to a cross-flow type oil / water separator has been described. However, the present invention can be applied to other types of oil / water separators. However, the cross-flow type is most preferable because the formation of the filter cake is relatively small and the water content in the stock solution near the filtration membrane is prevented from increasing.

In order to maintain a high purity of the filtrate, it is desirable that the oil provided in the oil tank 58 be the same as the oil to be filtered as much as possible.

In the above embodiment, the filtration pressure was set to 100 kPa, but the filtration pressure was set to 10 to 300 kP.
It is set appropriately within the range of a. However, in order to perform efficient filtration, it is desirable that the pressure is 20 kPa or more, and if the pressure is higher than the capillary pressure of the oil, water may enter the pores of the filtration membrane and the water content of the filtrate may increase. The pressure is preferably 200 kPa or less, and most preferably set in the range of 20 to 200 kPa. Also, if the filtration pressure is higher than necessary, the adhesion of clogging of the filtration membrane due to the solid content and tar content in the oil-water mixture becomes strong, and it becomes difficult to remove the clogging by washing or back washing. Speed decreases.

In the above-described embodiment, the pores of the filtration membrane were filled with oil. However, it was not necessary to completely impregnate the pores. For example, an oil film was formed on the surface of the filtration membrane on the first chamber 14 side. It may be in the state that it was in.

Further, a glass tube 6 for confirming oil impregnation is provided.
0 does not necessarily have to be used. For example, the impregnation state may be controlled by setting the oil impregnation step to a fixed time.

The three-way valve 52 for connecting the oil introduction path 56 to the undiluted liquid introduction port 16 is not always required. For example, an on-off valve that is separately operated may be provided in the oil introduction path 56 and the supply path 22. Further, the three-way valve 42 does not necessarily have to be provided.

The backwash means such as the backwash valve 48 and the backwash path 50 need not always be provided.

Although not specifically exemplified, the present invention can be variously modified without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an oil-water separation device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of another example of the oil-water separation device.

FIG. 3 is a diagram showing a configuration of still another example of the oil-water separation device.

FIG. 4 is a diagram showing a configuration of still another example of the oil-water separation device.

[Explanation of symbols]

 10: Filter 12: Ceramic filter (filtration membrane) 14: First chamber 22: Supply path 30: Return path 34: Second chamber ｛52: Three-way valve, 56: Oil introduction path｝ (Oil introduction means) 58: Oil Tank (oil supply source)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Yoshikawa 3-36 Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture Noritake Co., Ltd. Limited (72) Inventor Shinobu Okada 3-chome Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture No. 36 Noritake Co., Ltd. Noritake Co., Ltd. (56) References JP-A-5-31342 (JP, A) JP-A-63-44902 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ B01D 17/00-17/12 C02F 1/40 B01D 63/00-71/82

Claims (2)

(57) [Claims] 1. An oil-water separation method for recovering an oil having a low water content from an oil-water mixture using a filter having a first chamber and a second chamber separated by a filtration membrane, An oil impregnation step of previously impregnating the membrane with oil, and after the oil impregnation step, circulating the oil / water mixture to the first chamber of the filter at a predetermined pressure to remove the oil having a low moisture content into the filtration membrane. And a filtration step of filtering into a second chamber of the filter through a filter. 2. An oil having a low water content, comprising a filter having a first chamber and a second chamber separated by a filtration membrane, and circulating an oil-water mixture to the first chamber of the filter at a predetermined pressure. An oil / water separator of the type for filtering and recovering through the filtration membrane into the second chamber of the filter, comprising: an oil supply source; and circulating the oil / water mixture to the first chamber.
An oil introducing means for introducing oil from the oil supply source into the first chamber to impregnate the filtration membrane.