Abstract:
Provided is a crude oil recovery device for recovering crude oil from an oil-containing mixture in a stable manner and at low running cost. The crude oil recovery device for extracting crude oil from an oil-containing mixture composed of crude oil and both or one of water and solid, including an extraction tank for mixing the oil-containing mixture with an extracting solvent, and an evaporation/liquefaction unit for distilling an extraction solution after extraction, wherein naphtha, which is a crude oil component of the oil-containing mixture, is reused as the extracting solvent, the naphtha being a distillate obtained by distillation of the extraction solution.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the foreign priority benefit under Title 35, United States Code, §119 (a)-(d) of Japanese Patent Application No. 2015-190629, filed on Sep. 29, 2015, the disclosure of which is herein incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a crude oil recovery device for recovering crude oil from sludge containing crude oil by using hydrocarbon. 
       BACKGROUND ART 
       [0003]    For example as the crude oil recovery device, there are Patent Document 1 and Patent Document 2. Patent Document 1 discloses a method of extracting oil content from a mixture of solid, water and oil content by using hydrocarbon. Patent Document 2 discloses a method and device configuration for recovering oil from oil-contaminated soil. 
       CITATION LIST 
     Patent Literature 
       [0004]    [Patent Document 1] 
         [0005]    Japanese Patent Application Publication No. H02-273502 
         [0006]    [Patent Document 2] 
         [0007]    Japanese Patent Application Publication No. 2005-081166 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    As a method for recovering oil from a mixture of oil, water and solid, such as extraction of bitumen from tar sand, and separation of organic matter from refinery sludge, Patent Document 1 discloses a method of using hydrocarbon as an extracting solvent, obtaining an extraction solution containing oil (solute) extracted from the mixture by the extracting solvent, separating the extraction solution into the solute and the extracting solvent by distilling the extraction solution, and reusing the obtained extracting solvent for an extraction operation. However, in this method, since low boiling point hydrocarbons contained in the solute are also evaporated during reproduction of the extracting solvent, they are mixed into the reproduced extracting solvent, and a composition of the extracting solvent constantly changes. When the composition of the extracting solvent changes, extraction performance and evaporation characteristics also change, and thus appropriate extraction operation and evaporation operation are difficult. 
         [0009]    As a method of recovering oil from the oil-contaminated soil, Patent document 2 discloses a method of extracting oil (solute) in the soil by mixing hydrocarbon such as kerosene as the extracting solvent with the oil-contaminated soil. However, in this method, since a new solvent is always used as the extracting solvent, running cost is increased. 
         [0010]    Therefore, an object of the present invention is to provide a crude oil recovery device for recovering crude oil from an oil-containing mixture in a stable manner and at low running cost. 
       Solution to Problem 
       [0011]    In order to solve the above problems, the present invention is a crude oil recovery device for extracting crude oil from an oil-containing mixture composed of water, solid and crude oil, including an extraction tank for mixing the oil-containing mixture with an extracting solvent, and an evaporation/liquefaction unit for distilling an extraction solution after extraction, wherein naphtha, which is a crude oil component of the oil-containing mixture, is reused as the extracting solvent, the naphtha being a distillate obtained by distillation of the extraction solution. 
       Advantageous Effects of Invention 
       [0012]    According to the present invention, with the crude oil recovery device for recovering crude oil from the oil-containing mixture, it is possible to provide the crude oil recovery device which can be stably operated and can reduce running cost. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is an example of a configuration diagram of a crude oil recovery device according to an embodiment of the present invention; and 
           [0014]      FIG. 2  is another example of a configuration diagram of a crude oil recovery device according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    An example of an embodiment of the present invention will be described with reference to  FIG. 1 . 
         [0016]    At first, sludge as an extraction feed and naphtha as an extracting solvent are introduced into a mixing tank  1  and are stirred, and thus crude oil in the sludge is dissolved and extracted by the naphtha. After they are sufficiently stirred and extraction is completed, a valve  21  is opened so that a mixed solution is transferred to a liquid-liquid separation tank  2 . In the liquid-liquid separation tank  2 , the mixed solution is separated into an oil phase and an aqueous phase primarily by gravity. Since a solid contained in the sludge has a high density, the solid is stored in the aqueous phase side. After the mixed solution is sufficiently left to stand and separation is completed, a valve  22  is opened so that the solid is discharged together with water. After water discharge is completed, the valve  22  is closed and a valve  23  is opened, so that the naphtha containing crude oil, which is an extraction solution, is transferred to a recirculation tank  3 . 
         [0017]    When concentration of crude oil in the extraction solution stored in the recirculation tank  3  is low, the extraction solution can be reused for extraction as the extracting solvent. Therefore, when the sludge is introduced into the mixing tank  1 , the extraction solution is transferred to the mixing tank  1  by a pump  32  and is reused as an alternative of the naphtha to be introduced into the mixing tank  1 . 
         [0018]    The above-described operation can be repeated a plurality of times, however, since the concentration of the crude oil in the extraction solution is gradually increased and viscosity thereof is increased, extraction efficiency is reduced. Therefore, when the number of repetitions exceeds a predetermined number of times, when the concentration of the crude oil in the extraction solution exceeds a predetermined concentration of the crude oil, or when the viscosity thereof exceeds a predetermined viscosity, a valve  24  is opened so that the extraction solution is transferred to an extraction solution tank  4 . 
         [0019]    Next, flash evaporation is performed to separate the extraction solution into the extracting solvent and a solute. The extraction solution stored in the extraction solution tank  4  is transferred by a pump  31 , and temperature of the extraction solution is increased through a heat exchanger  11  and a heat exchanger  12  by receiving heat from a distillate and bottom product to be described below. Further, the extraction solution is heated to a predetermined temperature by a heater  13 , and is transferred to a gas-liquid separator  5  while low boiling point naphtha is evaporated. In the gas-liquid separator  5 , since heavy component in the crude oil remaining without evaporation accumulates in a bottom thereof, the heavy component is discharged as the bottom product from the bottom thereof by adjusting an open degree of a valve  25  as needed. Further, the heavy component is cooled by the extraction solution in the heat exchanger  12  and can be recovered as the crude oil. Meanwhile, vaporized naphtha is discharged from a top of the gas-liquid separator  5 , and is cooled in the heat exchanger  11  and a cooler  14  to be the distillate, and then is stored in a reproduced naphtha tank  6 . 
         [0020]    When there is not the extraction solution to be used as the extracting solvent in the mixing tank  1 , reproduced naphtha is transferred to the mixing tank  1  using a pump  33 , and is reused as the extracting solvent. 
         [0021]    As described above, in the present embodiment, almost all of the naphtha to be used as the extracting solvent circulates in the device, and further naphtha in the sludge is also incorporated into a circulation cycle of the extracting solvent by distillation. Therefore, a total amount of the naphtha in a circulation system increases, and thus it is possible to properly maintain the total amount of the naphtha in the circulation system and to recover surplus naphtha by opening a valve  26  as needed. 
         [0022]    Further, by reducing a control temperature of the heater  13 , it is possible to decrease an amount of circulating naphtha, and to increase an amount of crude oil to be recovered. Further, when there is a lot of heavy component in the crude oil in the sludge, there is a possibility that a portion of the naphtha is discharged as the bottom product, and the amount of the naphtha in the circulation cycle of the extracting solvent is decreased, however, in this case, it is possible to make up for insufficient naphtha by increasing the control temperature of the heater  13 . In general, it is preferable to distill the extraction solution at 80° C. or lower, since heat loss is increased as the temperature is increased. When there is a lot of heavy component in the crude oil in the sludge, extraction capability is improved if the extracting solvent contains aromatic compounds, and thus it is preferable to set the control temperature of the heater  13  to about 180° C. at which the aromatic compounds are evaporated. 
         [0023]    This device is characterized in that since component (naphtha) contained in the solute is used as the extracting solvent, when a maximum temperature in the distillation is set to be constant, the component of resulting distillate is substantially constant, and the extraction capability and a specific heat of the circulating naphtha in the device are substantially constant, and thus temperature control of distillation and mixing control in the mixing tank are very easy. 
         [0024]    Further, the liquid-liquid separation tank  2  used here may be improved in separation performance by using an inclined plate or the like. Further, it is possible to improve the separation performance among the oil phase, the aqueous phase and a solid phase by using a centrifugal separator instead of the liquid-liquid separation tank  2 . 
         [0025]    As described above, the present invention can recover the crude oil at high efficiency from the sludge containing crude oil. 
         [0026]    Next, another example of an embodiment of the present invention will be explained with reference to  FIG. 2 . 
         [0027]    At first, the sludge as the extraction feed and the naphtha as the extracting solvent are introduced into the mixing tank  1  and are mixed, and thus the crude oil in the sludge is dissolved and extracted by the naphtha. After they are sufficiently stirred and the extraction is completed, they are left to stand. When they are sufficiently left to stand, they are separated into the oil phase and the aqueous phase containing the solid under influence of gravity. After separation is completed, the valve  22  is opened so that the solid is discharged together with the water. Here, the naphtha containing the crude oil remains as the extraction solution in the mixing tank  1 . At this time, when the concentration of the crude oil in the extraction solution is low, the extraction solution can be reused as the extracting solvent, and thus it is possible to repeat the same operation after introducing the sludge into the mixing tank  1  again. When this operation is repeated, the concentration of the crude oil in the extraction solution is gradually increased and a viscosity thereof is increased, and thus the extraction performance is reduced. Therefore, when the number of repetitions exceeds a predetermined number of times, when the concentration of the crude oil in the extraction solution exceeds a predetermined concentration of the crude oil, or when the viscosity thereof exceeds a predetermined viscosity, the valve  23  is opened so that the extraction solution is transferred to the extraction solution tank  4 . 
         [0028]    Next, flash evaporation is performed to separate the extraction solution into the extracting solvent and the solute. The extraction solution stored in the extraction solution tank  4  is transferred by the pump  31  to be heated to a predetermined temperature by the heater  13 , and is transferred to the gas-liquid separator  5  while the low boiling point naphtha is evaporated. In the gas-liquid separator  5 , the heavy component in the crude oil remaining without evaporation accumulates in the bottom thereof, and thus it is possible to recover the crude oil as the bottom product by adjusting the open degree thereof. Meanwhile, vaporized naphtha is discharged from the top of the gas-liquid separator  5 , and is cooled by the cooler  14  to be the distillate, and then is stored in the reproduced naphtha tank  6 . 
         [0029]    When the extracting solvent used in the mixing tank  1  is transferred to the extraction solution tank  4 , the reproduced naphtha is transferred to the mixing tank  1  by the pump  33  and is reused as the extracting solvent. 
         [0030]    As described above, in the present embodiment, almost all of the naphtha to be used as the extracting solvent circulates in the device, and naphtha in the sludge is also incorporated into the circulation cycle of the extracting solvent by distillation. Therefore, the total amount of the naphtha in the circulation system increases, and thus it is possible to properly maintain the total amount of the naphtha in the circulation system and to recover the surplus naphtha by opening the valve  26  as needed. 
         [0031]    This device is characterized in that since the component (naphtha) contained in the solute is used as the extracting solvent, when the maximum temperature in the distillation is set to be constant, the component of resulting distillate is substantially constant, and the extraction capability and the specific heat of the circulating naphtha in the device are substantially constant, and thus temperature control of the distillation and mixing control in the mixing tank are very easy. 
         [0032]    The distillation of the present invention has been described with an example of flash evaporation, but it may be simple distillation if it is allowed to sacrifice stability of composition of a circulating extracting solvent. Further, when the naphtha cannot be prepared at start-up of the device, it is possible to use low boiling point hydrocarbons other than the naphtha or a mixture thereof as the extracting solvent although stability of the device is reduced. 
         [0033]    Note that, the present invention is not limited to the embodiments described above, but includes various modifications. For example, the heat exchanger  11  and the heat exchanger  12  are provided to improve thermal efficiency of the whole device, but they can be omitted. Further, the recirculation tank  3  and the extraction solution tank  4  are separately provided to improve stability of operation of the device, but they can be integrated into one. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : mixing tank 
           2 : liquid-liquid separation tank 
           3 : recirculation tank 
           4 : extraction solution tank 
           5 : gas-liquid separator 
           6 : reproduced naphtha tank 
           11 : heat exchanger 
           12 : heat exchanger 
           13 : heater 
           14 : cooler