Method for recovering oil from oil-containing waste liquid

Abstract

To provide a method for recovering oil from an oil-containing waste liquid, enabling efficient separation and recovery of oil from the oil-containing waste liquid through a solvent extraction method.SOLUTION: The method for recovering oil from an oil-containing waste liquid includes: an extraction step for extracting an oil-containing waste liquid using a solvent, thereby transferring oil in the oil-containing waste liquid to the solvent; a separation step for separating the solvent including the extracted oil and the waste liquid from each other; and an oil recovery step for separating and recovering the oil from the separated solvent-containing oil. In the method for recovering oil, the solvent is n-hexane, an oil concentration in the oil-containing waste liquid supplied to the extraction step is 1,000-5,000 mg / L, a volume ratio (solvent / waste liquid ratio) of the solvent to the oil-containing waste liquid is 0.01-0.05, and the oil concentration in the solvent containing the oil separated in the separation step is 4 mass% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for recovering oil from oil-containing waste liquid, and particularly to a method and an apparatus for recovering oil from oil-containing waste liquid using solvent extraction.

Background Art

[0002] In the water treatment for separating and recovering oil from oil-containing waste liquid, separation by a separation weir (oil trap) that utilizes the fact that oil floats on water, and floating treatment using micro air or micro air and chemicals are common (for example, Patent Document 1). Furthermore, a method of distributing oil to the solvent side by solvent extraction using a solvent and a mixer settler, etc., and then recovering the oil by volatilizing the solvent is also conceivable.

[0003] The oil separated by such a method has a large amount of energy and is of high utilization value. In addition, using the separated and recovered oil as an energy source also leads to waste reduction. Therefore, waste energy recovery including waste power generation using oil is expected to be increasingly emphasized in the future for the formation of a recycling-based society.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Among the conventional oil-water separation technologies, in the floating treatment, components other than oil are mixed into the components separated by floating, that is, SS components other than the oil contained in the wastewater, components derived from chemicals, moisture, etc. Therefore, in order to separate only the oil and use it for fuel, etc., a step of removing these contaminants by purification using centrifugation, etc. is required. In the separation and recovery of oil by solvent extraction, since the solvent used for extraction has no polarity, impurities such as hydrophilic substances such as ions are not taken in, and it is considered a method suitable for the utilization of the recovered oil. However, there are almost no examples of applying solvent extraction to the field of wastewater treatment, and the current situation is that there is no knowledge about the treatment conditions for application.

[0006] An object of the present invention is to provide a method and an apparatus for recovering oil from an oil-containing waste liquid that can efficiently separate and recover oil from the oil-containing waste liquid by a solvent extraction method.

Means for Solving the Problems

[0007] As a result of repeated studies to solve the above problems, the present inventor has found that by controlling the oil concentration of the oil-containing waste liquid to be subjected to solvent extraction and the volume ratio of the solvent used for extraction to the oil-containing waste liquid to appropriate values, the oil can be efficiently separated and recovered from the oil-containing waste liquid by solvent extraction. The gist of the present invention is as follows.

[0008] [1] An oil recovery method from an oil-containing waste liquid, comprising an extraction step of transferring the oil in the oil-containing waste liquid to a solvent by extracting the oil-containing waste liquid with a solvent, a separation step of separating the solvent containing the extracted oil from the waste liquid, and an oil recovery step of separating and recovering the oil from the separated solvent containing the oil, wherein the solvent is n-hexane, the oil concentration in the oil-containing waste liquid to be subjected to the extraction step is 1000 to 5000 mg / L, the volume ratio of the solvent to the oil-containing waste liquid (solvent / waste liquid ratio) is 0.01 to 0.05, and the oil concentration in the solvent containing the oil separated in the separation step is 4% by mass or more.

[0009] [2] The oil recovery method from an oil-containing waste liquid according to [1], wherein in the oil recovery step, the oil is separated from the solvent containing the oil by heating distillation to recover the solvent, and the recovered solvent is reused in the extraction step.

[0010] [3] In the separation by the heating distillation, the heat of the separated solvent or oil component is utilized for heating the solvent containing the oil component by using a heat exchanger or a heat pump, in the method for recovering oil from an oil-containing waste liquid according to [2].

[0011] [4] The method for recovering oil from an oil-containing waste liquid according to any one of [1] to [3], further having a concentration step of concentrating the oil-containing waste liquid or a dilution step of diluting the oil-containing waste liquid prior to the extraction step.

[0012] [5] The oil-containing waste liquid is any one of waste liquids from parts manufacturing factories such as automobiles containing mineral oil, aqueous cutting waste liquids, waste liquids from paper or paperboard factories containing turpentine oil, oil refineries, food and beverage factories, or food service industries, in the method for recovering oil from an oil-containing waste liquid according to any one of [1] to [4].

[0013] [6] An oil recovery apparatus for an oil-containing waste liquid, having an extraction means for transferring the oil in the oil-containing waste liquid to the solvent by subjecting the oil-containing waste liquid to an extraction treatment with a solvent, a separation means for separating the solvent containing the extracted oil from the waste liquid, and an oil recovery means for separating and recovering the oil from the separated solvent containing the oil, wherein the solvent is n-hexane, the oil concentration in the oil-containing waste liquid to be subjected to the extraction means is 1000 to 5000 mg / L, the volume ratio of the solvent to the oil-containing waste liquid (solvent / waste liquid ratio) is 0.01 to 0.05, and the oil concentration in the solvent containing the oil separated by the separation means is 4% by mass or more.

[0014] [7] The oil recovery means is a means for separating the oil from the solvent containing the oil by heating distillation, and the oil recovery apparatus for an oil-containing waste liquid according to [6], having a liquid supply means for feeding the solvent from which the oil has been separated by the oil recovery means to the extraction means.

[0015] The oil content recovery apparatus according to [7], which has a heat exchanger or a heat pump for heating the solvent containing the oil content by using the heat possessed by the solvent or the oil content separated by the heating distillation.

[0016] [9] The oil content recovery apparatus according to any one of [6] to [8], further comprising a concentration means for concentrating the oil content-containing waste liquid or a dilution means for diluting the oil content-containing waste liquid, upstream of the extraction means.

[0017]

[10] The oil content recovery apparatus according to any one of [6] to [9], wherein the oil content-containing waste liquid is any one of waste liquids from parts manufacturing factories such as automobiles containing mineral oil, aqueous cutting waste liquids, waste liquids from paper or paperboard factories containing turpentine oil, oil refineries, food and beverage factories or the food service industry containing animal and vegetable oils.

Advantages of the Invention

[0018] According to the present invention, the oil content can be efficiently separated and recovered from the oil content-containing waste liquid by solvent extraction. According to the present invention, the oil content in the oil content-containing waste liquid that inhibits wastewater treatment can be significantly reduced, and high-purity oil content can be recovered and effectively reused as an energy source in various fields. In addition, the amount of waste generated, such as sludge containing a large amount of oil content that has been waste so far, can be significantly reduced. Therefore, the industrial utility value of the present invention is extremely high.

Brief Description of the Drawings

[0019]

Figure 1

Embodiments for Carrying Out the Invention

[0020] Before explaining the embodiments of the oil recovery method and the oil recovery apparatus from the oil-containing waste liquid of the present invention, first, the mechanism of solvent extraction in the present invention will be described.

[0021] In the oil-containing waste liquid, usually, after solvent extraction, when the solvent is evaporated from the solvent containing oil by heating distillation in the oil recovery step to separate the oil, the oil-containing waste liquid contains an amount of oil that can supply energy equal to or more than the energy required for this heating distillation. On the other hand, considering a system in which n-hexane is used as the extraction solvent, oil is extracted from the oil-containing waste liquid by solvent extraction, the n-hexane used in the extraction is evaporated to separate and recover the residual oil, the evaporated n-hexane is recovered by natural cooling (air cooling) and reused for extraction, and the recovered oil is used as fuel (energy source), it is considered that a large amount of energy is occupied for evaporating n-hexane (however, there is also pump power for continuous processing, solvent loss, etc. as energy consumption other than solvent evaporation). Therefore, from the viewpoint of energy balance, the following formula needs to hold. Energy consumption (the amount of heat required to heat n-hexane containing oil to its boiling point and further evaporate all of the n-hexane) < Energy obtained (the amount of heat obtained by burning the recovered oil) From the heat quantity basic information of n-hexane and oil shown in Table 1 below, when the energy consumption is regarded as electricity (efficiency 100%) and the energy obtained is also regarded as electricity (the efficiency for generating electricity from oil is about 25%), as shown in Table 2 below, the oil concentration in n-hexane containing the extracted oil needs to be 4% by mass or more.

[0022]

Table 1

[0023]

Table 2

[0024] On the one hand, when a large amount of oil or the like dissolves in a solvent by solvent extraction, the specific gravity and viscosity of the resulting mixture of the solvent and the oil increase. As a result, it becomes easier for solids and water to mix into the mixture, making it difficult to extract and separate only pure oil from the oil-containing waste liquid. From these facts, limiting the range of the extracted oil concentration in the solvent from which the oil has been extracted is effective for efficiently extracting the oil in the oil-containing waste liquid to the solvent side. From the above, by performing pretreatment such as concentration or dilution as necessary to set the oil concentration range in the oil-containing waste liquid to be subjected to extraction within a predetermined range and limiting the amount of solvent used, and further setting the oil concentration in the solvent containing the extracted oil to a predetermined value or more, the separability between the solvent and water can be improved, and the loss of the solvent to the water side can also be made to be below a certain amount. Also, the appropriate size of the oil extraction facility with respect to the amount of extracted oil is determined, and the extraction of oil into the solvent can be performed efficiently.

[0025] Based on such a mechanism, according to the present invention, by setting the oil concentration of the oil-containing waste liquid to be subjected to extraction and the volume ratio of the solvent to the oil-containing waste liquid at this oil concentration (hereinafter, may be simply referred to as "solvent / waste liquid ratio") within a predetermined range, and setting the oil concentration in the solvent containing the extracted oil to a predetermined value or more, efficient solvent extraction can be performed. Furthermore, the separated and recovered oil can be efficiently and effectively utilized as an energy source.

[0026] In the present invention, the oil concentration in the oil-containing waste liquid to be subjected to solvent extraction is set to 1000 to 5000 mg / L. When the oil concentration of the oil-containing waste liquid is less than 1000 mg / L, the recovered oil as an energy source for heating and distilling the solvent (n-hexane) after extraction is insufficient. On the other hand, when the oil concentration exceeds 5000 mg / L, as described above, due to the increase in the specific gravity and viscosity of the mixture of the solvent from which the oil has been extracted and the oil, it becomes impossible to recover high-purity oil, the separation of the oil after extraction becomes difficult, and furthermore, the loss of the solvent also increases. From such a perspective, the oil concentration in the oil-containing waste liquid to be subjected to solvent extraction is preferably 1000 to 3000 mg / L, more preferably 1200 to 2500 mg / L.

[0027] In the present invention, the solvent (n-hexane) and the oil-containing waste liquid are subjected to solvent extraction so that the solvent / waste liquid ratio is 0.01 to 0.05. If the solvent / waste liquid ratio is less than 0.01, the amount of the solvent used for extraction is too small to perform efficient oil extraction, and oil will remain on the oil-containing waste liquid side. On the other hand, if the solvent / waste liquid ratio exceeds 0.05, the amount of the solvent used for extraction is too large to be economical, and the oil concentration in n-hexane also becomes low, which is not preferable from the viewpoint of increasing the size of the extraction apparatus. From such a perspective, the solvent / waste liquid ratio is preferably 0.02 to 0.04, more preferably 0.025 to 0.03.

[0028] In the present invention, the oil concentration of the solvent after extracting oil from the oil-containing waste liquid is made to be 4% by mass or more. Therefore, when extraction is performed using n-hexane according to the present invention, the oil concentration of n-hexane after extraction is 4% by mass or more, preferably 4 to 12% by mass, and more preferably 4 to 7% by mass, which is preferable from the viewpoints of oil separation efficiency and thermal energy efficiency in solvent regeneration.

[0029] Hereinafter, embodiments of the method and apparatus for recovering oil from the oil-containing waste liquid of the present invention, which are performed by controlling the oil concentration and the solvent / waste liquid ratio of such an oil-containing waste liquid, will be described with reference to FIG. 1. However, the present invention is not limited to the following in any way, and various modifications can be made and implemented within the scope of the gist of the present invention.

[0030] FIG. 1 is a flowchart showing a method and apparatus for recovering oil from an oil-containing waste liquid according to an embodiment of the present invention.

[0031] In the present invention, the oily waste liquid to be treated is a water-based waste liquid in which the water content in the waste liquid is 85% by mass or more. For example, it includes concentrated oily waste liquids generated from petroleum processes, steel rolling processes, paper or pulp manufacturing, metal cutting processes, food manufacturing, leather manufacturing, kitchens, sewage, etc. Specifically, it includes aqueous cutting waste liquids, terpene oil-containing wastewater discharged from paper and pulp factories, and food wastewater, but is not limited thereto. The oil in the oily waste liquid may be either mineral oil or animal and vegetable oil. The oil concentration of these oily waste liquids is usually about 0.05 to 1% by mass (500 to 10,000 mg / L). Therefore, when the oil concentration of the oily waste liquid to be treated in the present invention is outside the range of 1000 to 5000 mg / L, a concentration step for concentrating the oily waste liquid or a dilution step for diluting the oily waste liquid is provided in the front stage of the extraction step.

[0032] More specifically, the oily waste liquid includes waste liquids from parts manufacturing factories such as automobile factories containing mineral oil, waste liquids from paper pulp factories containing terpene oil, waste liquids from oil refineries, food and beverage factories, or the food service industry containing animal and vegetable oil. The oily waste liquid may be an organic substance-containing waste liquid extracted into a non-polar solvent.

[0033] In FIG. 1, the oily waste liquid is introduced into the membrane separation device 2 through the pipe 1 and concentrated to the aforementioned oil concentration by membrane separation. A part of the permeated water that has passed through the membrane is returned from the pipe 4A to the membrane separation device 2. The remaining part of the permeated water is sent through the pipe 4B to a wastewater treatment facility (not shown) for treatment.

[0034] The concentrated water and the extraction solvent of the membrane separation device 2 are respectively supplied to the mixing part 6a of the extraction device 6 through the pipes 5 and 7 at the aforementioned solvent / waste liquid ratio.

[0035] The concentrated water and the extraction solvent supplied to the mixing section 6a are mixed in the mixing section 6a, and the oil component in the concentrated water is taken into the solvent. That is, the oil component in the concentrated water dissolves in the extraction solvent. The solvent in which the oil component is dissolved and the concentrated water (residual liquid) from which the oil component has been extracted are naturally separated (specific gravity separation) in the separation section 6b, and the solvent in which the oil component is dissolved is supplied to the cold heat source flow path of the heat exchanger 9 via the pipe 8. This solvent in which the oil component is dissolved exchanges heat with the solvent vapor flowing through the fluid to be cooled flow path, is heated up, and is introduced into the distillation column 11 from the pipe 10. In the distillation column 11, the solvent (n-hexane) having a lower boiling point than the oil component flows to the top side of the column, and the high-boiling oil component flows to the bottom side of the column. The solvent vapor is supplied from the distillation column 11 to the fluid to be cooled flow path of the heat exchanger 9 via the pipe 12, is cooled by exchanging heat with the extraction device effluent (low-temperature liquid) flowing through the cold heat source flow path, and becomes a liquid solvent. This liquid solvent is sent to the mixing section 6a of the extraction device 6 by the pipe 7 and reused as the extraction solvent. In addition, for the solvent portion that has migrated into the treated water described later or has volatilized from the device and been lost, it is newly additionally supplied from outside the system.

[0036] From the bottom of the distillation column 11, the separated oil component is taken out via the pipe 14. This oil component is used as recovered oil for liquid fuel, combustion aid, etc. in power generation and other various applications. If necessary, further treatment may be performed on the recovered oil.

[0037] From the separation section 6b of the extraction device 6, the residual liquid from which the oil component has been extracted is taken out via the pipe 20. This residual liquid is sent to the membrane separation device 21, and the solvent component (residual solvent) in the residual liquid is concentrated by membrane separation.

[0038] The permeated water that has permeated through the membrane 21a of the membrane separation device 21 is taken out as treated water via the pipe 22. The concentrated water of the membrane separation device 21 is discharged via the pipe 23 and sent to a waste liquid treatment process (not shown) for concentration treatment or wastewater treatment, etc.

[0039] In the above-described embodiment, the oil-containing waste liquid is subjected to membrane separation treatment by the membrane separation device 2 to increase the oil concentration. However, for oils that can be easily separated from water, separation treatment may be performed using an oil-water separator that utilizes a specific gravity difference or micro air, and then, immediately or as necessary, separation treatment such as membrane separation treatment may be performed, followed by feeding the liquid to the extraction device 6.

[0040] The extraction device 6 may be either a continuous type or a batch type. Examples of continuous liquid-liquid extraction devices used on an industrial scale include mixer-settler type, spray tower, countercurrent contact tower, perforated plate tower (tray tower), and the like. The extraction device may be any of these, or other types.

[0041] In the present invention, since n-hexane (boiling point 67°C), which has a boiling point lower than the boiling point of the oil to be separated (about 250 to 600°C), is used as the extraction solvent, it is more energy-efficient when separating the oil from the solvent containing the oil by heating and distillation than when directly distilling the oil-containing waste liquid.

[0042] In FIG. 1, the solvent is regenerated by separating the oil from the solvent containing the oil by heating and distillation. For the regeneration of the solvent, heating and distillation utilizing the boiling point difference between the oil and the solvent as described above is suitable. As the method of heating and distillation, either batch distillation or continuous distillation can be applied, and methods such as flash distillation, plate column, and packed column can be applied. As a method for separating the oil from the solvent containing the oil, vacuum distillation may be performed in addition to heating and distillation.

[0043] As described above, in the present invention, the oil concentration in the oil-containing waste liquid to be subjected to extraction is set to 1000 to 5000 mg / L. Therefore, when the oil concentration of the oil-containing waste liquid is lower than the above range, prior to the extraction treatment, the oil-containing waste liquid is concentrated by gravity separation, pressure flotation, a membrane separation device, or other concentration means. On the other hand, when the oil concentration in the oil-containing waste liquid to be subjected to extraction is higher than the above range, a dilution mixing tank or the like for diluting the oil-containing waste liquid with industrial water, tap water, drainage from a different system from the target oil-containing drainage, drain water, etc. is provided to dilute the oil-containing waste liquid.

[0044] In order to promote the separation of oil from the oil-containing waste liquid, salts such as sodium chloride, alkalis, or acids may be added to the oil-containing waste liquid prior to the extraction treatment. For example, in the case of sodium chloride, by adding about 0.1 to 30% by mass to an oil-containing waste liquid containing about 0.05 to 1% by mass of oil, or by reducing the pH to about 2, the separation efficiency of the oil can be increased.

[0045] As described above, the oil concentration of the solvent after extracting the oil from the oil-containing waste liquid is set to 4% by mass or more. Therefore, when extraction is performed using n-hexane according to the present invention, the oil concentration of the n-hexane after extraction is 4% by mass or more, preferably 4 to 12% by mass, and more preferably 4 to 7% by mass, so that the oil separation efficiency and the thermal energy efficiency in solvent regeneration can be increased.

[0046] In FIG. 1, the membrane separation device 21 separates the residual substances in the waste liquid (residual liquid) after oil separation by applying reverse osmosis membrane treatment. However, adsorption treatment using activated carbon or the like may be applied to separate the solvent components in the waste liquid (residual liquid) after oil separation. Further, the residual solvent may be decomposed by adding an oxidizing agent or by biological treatment.

Examples

[0047] The effects of the present invention are shown below by giving experimental examples instead of examples.

[0048] [Experimental Example 1] Assuming the washing wastewater of dairy products as the oil-containing waste liquid, milk (milk fat content 3.5% by mass, non-fat milk solids 8.4% by mass, water 88.1% by mass) was diluted with pure water to prepare a simulated oil-containing waste liquid, and an oil extraction experiment using n-hexane was carried out. Milk, pure water, and n-hexane were placed in a 2000 mL flask with a lid, and the extraction operation was performed by horizontal shaking at 180 rpm for 30 minutes. Then, it was put into a separating funnel and left standing for 30 minutes to separate the n-hexane phase and the water phase. The transparent part of the n-hexane phase was collected, and n-hexane was evaporated in a constant temperature bath at 80 °C, and the weight of the remaining residue was measured. In addition, there were cases where the n-hexane phase was almost an emulsion with no transparent part (poor separability). In such cases, centrifugation (3000 rpm, 10 minutes) was performed to collect the transparent part. The results are shown in Table 3. The maximum extraction concentration in Table 3 is the concentration assuming that all the oil components (milk fat components) in the sample (milk diluted with pure water) were extracted into the n-hexane used for extraction. The extraction rate is a value with this concentration as the denominator and the actual extraction concentration as the numerator. Also, the criteria for judging separability are as follows. <Separability> ○: Good separability △: Separable ×: Inseparable

[0049]

Table 3

[0050] It can be seen from Table 3 that The smaller the solvent / waste liquid ratio, and furthermore, the larger the oil component concentration in the sample, the more likely the separability is to deteriorate. When the solvent / waste liquid ratio is 0.01, if the oil component concentration in the sample exceeds 5000 mg / L and reaches 8750 mg / L, it becomes inseparable. On the other hand, the oil component concentration (extraction concentration) in n-hexane is less than 4% by mass, the concentration obtained from the above-mentioned energy balance, when the solvent / waste liquid ratio is large. However, it can be seen that this is satisfied when the solvent / waste liquid ratio is reduced. That is, in the solvent extraction of oil components from oil-containing waste liquid using n-hexane, it can be seen that there are appropriate oil component concentrations in the oil-containing waste liquid, solvent / waste liquid ratios, and extraction concentrations.

Explanation of symbols

[0051] 2,21 Membrane separation device 6 Extraction device 11 Distillation column

Claims

1. An oil recovery method from an oil-containing waste liquid, comprising: an extraction step of transferring the oil in the oil-containing waste liquid to a solvent by extracting the oil-containing waste liquid with the solvent; a separation step of separating the solvent containing the extracted oil from the waste liquid; and an oil recovery step of separating and recovering the oil from the separated solvent containing the oil, wherein the solvent is n-hexane, the oil concentration in the oil-containing waste liquid to be subjected to the extraction step is 1000 to 5000 mg / L, the volume ratio of the solvent to the oil-containing waste liquid (solvent / waste liquid ratio) is 0.01 to 0.05, and the oil concentration in the solvent containing the oil separated in the separation step is 4% by mass or more.

2. The oil recovery method from an oil-containing waste liquid according to claim 1, wherein in the oil recovery step, the oil is separated from the solvent containing the oil by heating and distillation to recover the solvent, and the recovered solvent is reused in the extraction step.

3. The oil recovery method from an oil-containing waste liquid according to claim 2, wherein in the separation by heating and distillation, the heat of the separated solvent or the oil is used to heat the solvent containing the oil by using a heat exchanger or a heat pump.

4. The oil recovery method from an oil-containing waste liquid according to claim 1 or 2, further comprising a concentration step of concentrating the oil-containing waste liquid or a dilution step of diluting the oil-containing waste liquid prior to the extraction step.

5. The oil-containing waste liquid is any one of waste liquids from parts manufacturing factories of automobiles or the like containing mineral oil, aqueous cutting waste liquids, waste liquids from paper or paperboard factories containing turpentine oil, waste liquids from oil refineries, food and beverage factories or the food service industry containing animal and vegetable oils.

6. An oil recovery apparatus for an oil-containing waste liquid, comprising: an extraction means for transferring the oil in the oil-containing waste liquid to a solvent by extracting the oil-containing waste liquid with the solvent; a separation means for separating the solvent containing the extracted oil from the waste liquid; and an oil recovery means for separating and recovering the oil from the separated solvent containing the oil, wherein the solvent is n-hexane, the oil concentration in the oil-containing waste liquid to be subjected to the extraction means is 1000 to 5000 mg / L, the volume ratio of the solvent to the oil-containing waste liquid (solvent / waste liquid ratio) is 0.01 to 0.05, and An oil recovery device from an oil-containing waste liquid, characterized in that the oil concentration in the solvent containing the oil separated by the separation means is 4% by mass or more. **Claim 7** The oil recovery means is a means for separating the oil from the solvent containing the oil by heating distillation, The oil recovery device from an oil-containing waste liquid according to claim 6, further comprising a liquid supply means for feeding the solvent from which the oil has been separated by the oil recovery means to the extraction means. **Claim 8** The oil recovery device from an oil-containing waste liquid according to claim 7, further comprising a heat exchanger or a heat pump for heating the solvent containing the oil by using the heat of the solvent or the oil separated by the heating distillation. **Claim 9** The oil recovery device from an oil-containing waste liquid according to claim 6 or 7, further comprising a concentration means for concentrating the oil-containing waste liquid or a dilution means for diluting the oil-containing waste liquid, upstream of the extraction means. **Claim 10** The oil-containing waste liquid is any one of waste liquids from parts manufacturing factories such as automobiles containing mineral oil, aqueous cutting waste liquids, waste liquids from paper or paperboard factories containing turpentine oil, oil refineries, food and beverage factories, or food service industries containing animal and vegetable oils. The oil recovery device from an oil-containing waste liquid according to claim 6 or 7.

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