Method for recovering oil fraction in crude oil sludge and method for producing regenerated crude oil

Abstract

The present invention addresses the problem of providing a method for recovering the oil fraction in crude oil sludge that continuously and easily separates the oil fraction in crude oil sludge.　Provided is a method for recovering the oil fraction in crude oil sludge that is a method for separating a crude-oil-sludge-containing material into a first layer (recovered oil fraction), a second layer (heavy hydrocarbons), and a water layer in a separation zone by supplying the crude-oil-sludge-containing material at 40-200°C to a decanter centrifuge and centrifuging the same, the method comprising: while supplying the crude-oil-sludge-containing material to the separation zone, (i) recovering a first layer (recovered oil fraction) from a light side at one end of the separation zone; (ii) recovering at least part of a water layer and a second layer (heavy hydrocarbons) from a heavy side at one end of the separation zone, (iii) discharging the remainder of the heavy hydrocarbons from a solids fraction discharge port at the other end of the separation zone, during which time the "(distance from the rotation axis center to the water layer side end of the baffle plate-ri') / (distance from the rotation axis center to the water layer side end of the baffle plate-rB)" is kept within a predetermined range.

Description

Method for recovering oil from crude oil sludge and method for producing recycled crude oil

[0001] The present invention relates to a method for recovering oil from crude oil sludge accumulated in a crude oil tank in which crude oil is stored, and a method for producing recycled crude oil.

[0002] After crude oil sludge accumulates in crude oil tanks, it is generally treated as industrial waste after being removed from the tank, but this disposal process is expensive. On the other hand, crude oil sludge often contains approximately 30 to 80% by volume of oil, so there is a great need to recover the oil from crude oil sludge.

[0003] Therefore, attempts have been made to recover oil from crude oil sludge by vacuum distillation, thermal separation, centrifugal separation, etc. (see, for example, Patent Documents 1 to 3).

[0004] International Publication No. 2012 / 141024 Japanese Patent Application Laid-Open No. 3-226481 Japanese Patent Application Laid-Open No. 2004-243300

[0005] However, the above-mentioned methods, such as vacuum distillation and thermal separation, require large-scale equipment, resulting in increased capital investment costs, and the centrifugation method requires multiple separation steps when centrifuging a substance that separates into multiple layers, resulting in complicated processing.

[0006] Under these circumstances, a method for recovering oil from crude oil sludge includes a first step of obtaining a heated and stirred crude oil sludge and crude oil; The obtained heated and stirred product (crude oil sludge-containing product) is supplied to a decanter centrifuge and centrifuged to separate it into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, an aqueous layer, and solids in the separation zone of the decanter centrifuge. While supplying the heated and stirred product to the separation zone, (i) the first layer is discharged from the light side at one end of the separation zone to recover the recovered oil, and (ii) the aqueous layer is discharged from the heavy side at one end of the separation zone to recover the water, and (iii) the heavy hydrocarbons and the solids are mixed at the other end of the separation zone to form a solid mixture of heavy hydrocarbons and solids, and then the solid mixture of heavy hydrocarbons and solids is discharged outside the separation zone to recover the heavy hydrocarbon and solid mixture. A method for recovering oil from crude oil sludge has been proposed (see JP 2018-2899 A).

[0007] According to the method described in JP 2018-2899 A, oil in crude oil sludge can be recovered using simple equipment and fewer steps.

[0008] In the method described in JP 2018-2899 A, a screw plate spirally disposed inside the centrifuge is rotated around a rotation axis to discharge solids (a mixture of heavy hydrocarbons and solid matter such as sand) from a solids outlet provided at the other end of the separation region. However, the inventors have conducted studies and found that, depending on the centrifugation conditions, the solid viscous heavy hydrocarbons may adhere to the screw plate, making it difficult to transport them in the direction of the solids outlet, or the solid viscous heavy hydrocarbons may clog the solids outlet, making it impossible to continuously separate the oil to be recovered from other components.

[0009] Under these circumstances, an object of the present invention is to provide a method for recovering oil from crude oil sludge, which allows for simple and continuous separation of the oil from crude oil sludge, and a method for producing recycled crude oil.

[0010] As a result of research conducted by the present inventors in order to solve the above technical problems, they came up with the idea of: when centrifuging a crude oil sludge-containing material in a decanter centrifuge, the obtained oil is recovered while the by-product heavy hydrocarbons are discharged from the other end of the separation zone, and a portion of these are further discharged together with water from one end of the separation zone, thereby dispersing the discharge path for the heavy hydrocarbons, thereby suppressing adhesion of heavy hydrocarbons to the screw plate and clogging of the solids discharge port with solids (a mixture of heavy hydrocarbons and solids such as sand).

[0011] On the other hand, further investigation by the present inventors revealed that when an attempt is made to discharge a portion of the heavy hydrocarbons separated by the decanter centrifuge together with water, the recovered oil is discharged together with the heavy hydrocarbons, making it difficult to recover the recovered oil.

[0012] In order to solve the above technical problems, the present inventors conducted extensive research and found that the above technical problems can be solved by centrifuging crude oil sludge in a decanter centrifuge while controlling the position of the estimated oil-water interface so that a specific ratio shown in the following formula (II) falls within a predetermined range. Based on this finding, the present invention has been completed.

[0013] That is, the present invention provides a method for recovering oil from crude oil sludge, which is separated into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and a water layer, in a separation zone of a decanter centrifuge having: (1) an inner cylinder formed with a material feed port for discharging a material containing crude oil sludge, which is a material to be treated, from the inside to the outside and for supplying it to a separation zone; and an outer cylinder provided coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and with a solids discharge port for discharging heavy hydrocarbons from the inside to the outside, the outer cylinder forming a separation zone between the inner cylinder and the outer cylinder; by supplying the material containing crude oil sludge at 40 to 200°C and centrifuging it, the method comprising: (i) discharging the first layer to the outside of the separation zone from a light component discharge port of a light component discharge path provided on the light component side at one end of the separation zone, and recovering the recovered oil; (ii) discharging at least a portion of the aqueous layer and the second layer from the heavy side at one end of the separation zone into a heavy component discharge channel over a baffle that defines one end of the separation zone, and then retaining them inside a weir that is connected to the separation zone and is provided in the heavy component discharge channel adjacent to the baffle, and then discharging at least a portion of the aqueous layer and the second layer from a heavy component discharge port provided in the heavy component discharge channel to recover water and heavy hydrocarbons; (iii) discharging the remainder of the heavy hydrocarbons out of the separation zone from the solid component discharge port provided on the other end of the separation zone to recover the heavy hydrocarbons; and (where r ｉ ': Distance (m) from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface Ａ　 r: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ｂ　 ρ: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ａ : density of the water (kg / m ３ ) ρ Ｂ : density of the recovered oil (kg / m ３ ) and h Ａ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the heavy component discharge port, calculated by Ａ : the flow rate (m) of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge ３ / s), v Ａ : outflow velocity of the discharged liquid at the heavy fraction discharge port (m / s), ω: angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the heavy fraction discharge port, N Ａ : number of heavy component discharge ports, C: outflow coefficient, S Ａ : the vertical cross-sectional area (m ２ ) is) h Ｂ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, calculated by Ｂ : the flow rate (m ) of recovered oil discharged from the light fraction discharge port of the decanter centrifuge ３ / s), v Ｂ : outflow velocity of the discharged liquid at the light fraction discharge port (m / s), ω: angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the light fraction discharge port, N Ｂ : number of light component discharge ports, C: outflow coefficient, S Ｂ : the vertical cross-sectional area (m ２ )), the following formula (II) (the distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r ｉ ') (m) / (distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ) (m) (II) to be 0.170 to 0.450, (2) A method for recovering oil content in crude oil sludge, characterized in that the crude oil sludge is centrifuged while controlling the ratio represented by the formula (1) to (2) so that the ratio represented by the formula (1) is 0.170 to 0.450, (2) A method for recovering oil content in crude oil sludge, characterized in that the crude oil sludge is supplied to a decanter-type centrifuge having an inner cylinder formed with a material supply port for discharging the material from the inside to the outside and supplying it to a separation region, an outer cylinder provided coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and having a solids discharge port for discharging the heavy hydrocarbons from the inside to the outside, and forming a separation region between the inner cylinder and the outer cylinder, a screw plate wound helically around the outer wall of the inner cylinder, and an outer cylinder fixing member provided on one end of the separation region and having a light component discharge path for discharging the recovered oil close to the inner cylinder and a heavy component discharge path for discharging water and heavy hydrocarbons close to the outer cylinder, (3) A method for recovering oil from crude oil sludge according to (1) or (2) above, wherein the aqueous layer formed in the decanter centrifuge contains metal chloride salts at a concentration of 3.0 to 5.0% by mass; (4) A method for recovering oil from crude oil sludge according to any of (1) to (3) above, wherein a crude oil sludge-containing material to be centrifuged is stored in a storage tank having a heating means at a temperature of 40 to 200°C, and is circulated so that it is sent out through an external circulation line provided outside the storage tank and returned to the storage tank, and a portion of the crude oil sludge-containing material circulating in the external circulation line is extracted from an extraction line installed midway through the circulation line at a speed of 20 to 60% of the circulation speed of the crude oil sludge-containing material, and supplied to the decanter centrifuge; (5) A method for producing recycled crude oil, characterized in that the oil in crude oil sludge obtained by the recovery method according to any of (1) to (4) above is mixed with crude oil.

[0014] According to the present invention, when a crude oil sludge-containing material is centrifuged using a decanter centrifuge, the resulting oil is recovered while the by-product heavy hydrocarbons are discharged from the other end of the separation zone, and a portion of the heavy hydrocarbons is also discharged together with water from one end of the separation zone, thereby dispersing the heavy hydrocarbon discharge paths. By controlling the position of the estimated oil-water interface so that the specific ratio represented by Equation (II) falls within a predetermined range, the recovered oil is prevented from being discharged together with water, and a portion of the heavy hydrocarbons can be discharged together with water to the outside of the separation zone before the heavy hydrocarbons adhere to the screw plate or before solids (a mixture of heavy hydrocarbons and solids such as sand) clog the solids discharge port. Therefore, the present invention provides a method for recovering oil from crude oil sludge, which allows for simple and continuous separation of the oil from the crude oil sludge, and a method for producing recycled crude oil.

[0015] 4 is a schematic cross-sectional view of an example of a decanter centrifuge. FIG. 5 is a schematic view showing the outer cylinder fixing member 25 in FIG. 1. FIG. 6 is a schematic view showing the separation state after centrifugal separation of material containing crude oil sludge using a batch centrifuge. FIG. 7 is an enlarged view of the lower part of the decanter centrifuge 1 shown in FIG. 1, and a schematic cross-sectional view showing the state in which each layer is separated in the separation region 6. FIG. 8 is a view showing the range of the separation region 6 in FIG. 4. FIG. 9 is an enlarged view of the upper part of the decanter centrifuge 1 shown in FIG. 1, and a schematic cross-sectional view showing the state in which each layer is separated in the separation region 6. FIG. 10 is a view showing the range of the separation region 6 in FIG. 6. FIG. 11 is an enlarged view of the vicinity of a heavy component discharge path 37 in the decanter centrifuge shown in FIG. 1, and a schematic cross-sectional view for explaining the positional relationship between the vicinity of the heavy component discharge path 37 and the center Ax of the inner cylinder rotating shaft 23 or the outer cylinder rotating shaft 24. 10( a ) is an enlarged view of the vicinity of the light fraction discharge path 38 in the decanter centrifuge shown in FIG. 1 , and is a schematic cross-sectional view for explaining the positional relationship between the vicinity of the light fraction discharge path 38 and the center Ax of the inner cylinder rotating shaft 23 or the outer cylinder rotating shaft 24.

[0034] FIG. 10( a ) is a schematic view showing the outer cylinder fixing member 25 in FIG. 1 , and FIG. 10( a ) is a front view of the outer cylinder fixing member 25 in FIG. 1 from the heavy fraction discharge port 374 or the light fraction discharge port 384 side (the discharge side of the discharged liquid from the heavy fraction discharge port 374 or the light fraction discharge port 384). FIG. 10( b ) is an enlarged view of the heavy fraction discharge port 374 in FIG. 10( a ), and FIG. 10( c ) is an enlarged view of the light fraction discharge port 384 in FIG. 10( a ).

[0035] FIG. 10( a ) is a schematic view for explaining an example of how crude oil sludge accumulated in a crude oil tank is removed from the crude oil tank. FIG. 1 is a schematic diagram illustrating an example in which a crude oil sludge-containing material stored at a predetermined temperature in a storage tank is circulated in an external circulation line, and a portion of the material is extracted from the circulation line at a predetermined speed and supplied to a decanter centrifuge.

[0016] First, the method for recovering oil from crude oil sludge according to the present invention will be described. The method for recovering oil in crude oil sludge according to the present invention is a method for recovering oil in crude oil sludge, which is separated into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and a water layer in a separation zone of a decanter centrifuge having an inner cylinder formed with a material feed port for discharging a material containing crude oil sludge, which is a material to be treated, from the inside to the outside and for supplying it to a separation zone, and an outer cylinder provided coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and having a solids discharge port for discharging heavy hydrocarbons from the inside to the outside, the outer cylinder forming a separation zone between the inner cylinder and the outer cylinder, wherein the material containing crude oil sludge is supplied and centrifuged at 40 to 200°C, and the method comprises the steps of: (i) while supplying the material containing crude oil sludge to the separation zone, (i) discharging the first layer to the outside of the separation zone from a light component discharge port of a light component discharge path provided on the light component side at one end of the separation zone, and (ii) recovering the recovered oil; (ii) discharging at least a portion of the aqueous layer and the second layer from the heavy side at one end of the separation zone into a heavy component discharge channel over a baffle that defines one end of the separation zone, and then retaining them inside a weir that is connected to the separation zone and is provided in the heavy component discharge channel adjacent to the baffle, and then discharging at least a portion of the aqueous layer and the second layer from a heavy component discharge port provided in the heavy component discharge channel to recover water and heavy hydrocarbons; (iii) discharging the remainder of the heavy hydrocarbons out of the separation zone from the solid component discharge port provided on the other end of the separation zone to recover the heavy hydrocarbons; and (where r ｉ ': Distance (m) from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface Ａ　 r: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ｂ　 ρ: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ａ : density of the water (kg / m ３ ) ρ Ｂ : density of the recovered oil (kg / m３ ) and h Ａ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the heavy component discharge port, calculated by Ａ : the flow rate (m) of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge ３ / s), v Ａ : outflow velocity of the discharged liquid at the heavy fraction discharge port (m / s), ω: angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the heavy fraction discharge port, N Ａ : number of heavy component discharge ports, C: outflow coefficient, S Ａ : the vertical cross-sectional area (m ２ ) is) h Ｂ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, calculated by Ｂ : the flow rate (m ) of recovered oil discharged from the light fraction discharge port of the decanter centrifuge ３ / s), v Ｂ : outflow velocity of the discharged liquid at the light fraction discharge port (m / s), ω: angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the light fraction discharge port, N Ｂ : number of light component discharge ports, C: outflow coefficient, S Ｂ : the vertical cross-sectional area (m ２ )), the following formula (II) (the distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r ｉ ') (m) / (distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ ) (m) (II) and performing centrifugation while controlling the ratio to be 0.170 to 0.450.

[0017] In the method for recovering oil from crude oil sludge according to the present invention, crude oil sludge refers to sediment that is generated from crude oil stored in the tank and accumulates on the bottom of the crude oil tank.

[0018] Examples of crude oil sludge include crude oil sludge that is generated from crude oil in a crude oil tank after solids, water, etc. have been removed and the crude oil is stored in the crude oil tank before it is shipped to an oil refinery and that accumulates at the bottom of the crude oil tank; crude oil sludge that accumulates at the bottom of a crude oil tank in a crude oil tanker; crude oil sludge that is generated from crude oil in a crude oil storage tank before it is refined at an oil refinery and that accumulates at the bottom of the crude oil tank, etc. The crude oil sludge may be generated from one type of crude oil or from multiple types of crude oil.

[0019] Crude oil sludge contains oil, asphaltene, iron, sand, water, etc. The oil in crude oil sludge is mainly paraffin and aromatic hydrocarbons having a carbon number of 40 or more. This oil in crude oil sludge is the component recovered from crude oil sludge by the method for recovering oil from crude oil sludge of the present invention.

[0020] The oil content in crude oil sludge is not particularly limited, but is usually 30 to 80 mass %. In the method for recovering oil from crude oil sludge according to the present invention, as described below, the crude oil sludge-containing material is heated to a predetermined temperature to uniformly disperse the oil in the crude oil sludge-containing material, and then supplied to a decanter centrifuge and centrifuged.

[0021] The method for removing crude oil sludge accumulated in a crude oil tank from the tank is not particularly limited, and examples thereof include: (1) a method of mixing crude oil with the crude oil sludge after the crude oil in the tank has been removed from the tank, such as a method of injecting high-pressure crude oil into the crude oil sludge accumulated in the tank and using the crude oil to push the crushed or partially dissolved crude oil sludge out of the tank (COW: Crude Oil Washing); (2) a method of manually removing the crude oil in the tank from the tank; and (3) a method of pressure-transporting the remaining crude oil sludge using a pump or the like after the crude oil in the tank has been removed from the tank.

[0022] In the above-mentioned (1) method of mixing crude oil with crude oil sludge after discharging crude oil from a crude oil tank to the outside of the crude oil tank, the crude oil to be mixed with the crude oil sludge is not particularly limited, and may be crude oil after crude oil extraction and before solids, moisture, etc. are removed and stored in a crude oil tank, crude oil that has been recently stored in a crude oil tank after crude oil extraction and after solids, moisture, etc. are removed and before crude oil sludge is generated, or crude oil that is the supernatant in a crude oil tank after crude oil sludge is generated at the bottom of the crude oil tank due to storage in the crude oil tank for a certain period of time. The crude oil may be the same type of crude oil as the crude oil that is the source of the crude oil sludge, or a different type of crude oil.

[0023] As a method of (1) above, in which crude oil is mixed with crude oil sludge after the crude oil in the crude oil tank is extracted to the outside of the crude oil tank, specifically, as shown in FIG. 11(a), after the crude oil in the crude oil tank 100 is extracted to the outside of the crude oil tank, the crude oil sludge S remaining in the crude oil tank 100 is pumped out of the crude oil tank 100 by a pump P. １ The crude oil sludge S and the crude oil C are mixed to obtain a mixture m by supplying the crude oil C from the crude oil tank 110 to the crude oil tank 100 through the circulation line r while performing a process of extracting the crude oil from the crude oil tank 100 using the pump P and circulating it through the circulation line r and returning it to the crude oil tank 100. ２ The crude oil can be supplied from the crude oil tank 100 to the decanter centrifuge 1 by the above method.

[0024] In the above-mentioned (1) method of mixing crude oil with crude oil sludge after the crude oil in a crude oil tank has been removed from the tank, the crude oil sludge and crude oil are mixed so that the ratio of crude oil sludge to the total of the crude oil sludge and crude oil is preferably 20 to 99% by mass, more preferably 40 to 98% by mass, and even more preferably 60 to 95% by mass. By setting the ratio of crude oil sludge to the total of the crude oil sludge and crude oil at or above the above-mentioned lower limit, the processing volume during centrifugation using a decanter centrifuge is reduced, resulting in improved economic efficiency. Furthermore, by setting the ratio at or below the above-mentioned upper limit, it becomes easier to recover oil from the crude oil sludge depending on the properties of the crude oil sludge.

[0025] As a method of (3) pumping the crude oil sludge remaining in the crude oil tank after the crude oil in the tank is extracted to the outside, specifically, as shown in FIG. 11(b), after the crude oil in the crude oil tank 100 is extracted to the outside of the crude oil tank, the crude oil sludge S remaining in the crude oil tank 100 is pumped out by the pump P. ３ The crude oil sludge S obtained is pumped out of the crude oil tank 100 by using a pump P ３ The crude oil can be supplied from the crude oil tank 100 to the decanter centrifuge 1 by the above method.

[0026] In the method for recovering oil from crude oil sludge according to the present invention, the "crude oil sludge-containing material" supplied to the decanter centrifuge means a material consisting of crude oil sludge alone or a material consisting of crude oil sludge mixed with crude oil.

[0027] In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge-containing material preferably has a crude oil sludge content of 10 to 100 mass%, more preferably 40 to 100 mass%, and even more preferably 60 to 100 mass%.

[0028] When the crude oil sludge-containing material supplied to the decanter centrifuge is a mixture obtained by the above-mentioned method (1) of mixing crude oil with crude oil sludge after discharging crude oil from a crude oil tank out of the crude oil tank, the crude oil sludge content ratio refers to the weight ratio of the crude oil sludge to the weight of the mixture of crude oil sludge and the crude oil mixed with the crude oil sludge. In the method for recovering oil from crude oil sludge according to the present invention, crude oil may be further added to any of (1) a mixture obtained by discharging crude oil from a crude oil tank out of the crude oil tank and mixing crude oil with crude oil sludge, (2) crude oil sludge obtained by discharging crude oil from a crude oil tank out of the crude oil tank, and (3) crude oil sludge obtained by discharging crude oil from a crude oil tank out of the crude oil tank and then pumping it out with a pump or the like, to obtain a crude oil sludge-containing material with a crude oil sludge content adjusted to a desired ratio, and this may be supplied to the decanter centrifuge.

[0029] In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge-containing material is supplied to a decanter centrifuge at 40 to 200° C. and centrifuged. In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge-containing material is preferably supplied to a decanter centrifuge at 50 to 150° C. and centrifuged, and more preferably supplied to a decanter centrifuge at 60 to 100° C. and centrifuged.

[0030] By keeping the temperature of the crude oil sludge-containing material that is supplied to the decanter centrifuge and centrifuged within the above range, when the crude oil sludge-containing material is supplied to the decanter centrifuge and centrifuged, it is possible to easily recover a sufficient amount of oil from the crude oil sludge while suppressing the loss of light fractions due to volatilization.

[0031] In the method for recovering oil from crude oil sludge according to the present invention, a crude oil sludge-containing material is heated to a desired temperature and then supplied to a decanter-type centrifuge. Specifically, for example, in the example shown in FIG. 11(a), a mixture m of crude oil sludge S and crude oil C obtained by mixing in a crude oil tank 100 is pumped through a pump P. ２ In the example shown in FIG. 11(b), the crude oil sludge S in the crude oil tank 100 is pumped by a pump P ３ For example, a heater (not shown) may be provided in the line supplying the decanter centrifuge 1.

[0032] In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge-containing material is preferably thoroughly stirred before being fed to the decanter centrifuge. By thoroughly stirring the crude oil sludge-containing material, the components in the crude oil sludge-containing material can be thoroughly dispersed and homogenized.

[0033] In the method for recovering oil from crude oil sludge according to the present invention, the method for heating and stirring the crude oil sludge-containing material to a desired temperature and then supplying it to a decanter centrifuge can include the following method: The crude oil sludge-containing material to be centrifuged is stored in a storage tank equipped with a heating means at a temperature of 40 to 200°C, and is circulated from an external circulation line provided outside the storage tank to return to the storage tank, while a portion of the crude oil sludge-containing material circulating in the external circulation line is extracted from an extraction line installed midway through the circulation line at a speed of 20 to 60% of the circulation speed of the crude oil sludge-containing material, and supplied to the decanter centrifuge.

[0034] In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge-containing material stored in a storage tank at a predetermined temperature is circulated in an external circulation line, and a portion of it is extracted from the circulation line at a predetermined speed and supplied to a decanter centrifuge. This makes it possible to control the temperature of the crude oil sludge-containing material within a desired range while sufficiently stirring it in the external circulation line, and therefore the components of the crude oil sludge-containing material can be continuously supplied to the decanter centrifuge in a sufficiently dispersed and homogenized state.

[0035] Specifically, as illustrated in FIG. 12(a), the crude oil sludge-containing material (mixture m) obtained by the method shown in FIG. 11(a) is stored at a predetermined temperature in a storage tank 200 having a heating means (not shown), and the crude oil sludge-containing material stored in the storage tank 200 is circulated through an external circulation line R provided outside the storage tank 200. １ Pump P ４ circulating the water back to the sending storage tank 200 using the external circulation line R １ One example of a method is to extract a portion of the crude oil sludge-containing material circulating within the decanter centrifuge 1 from an extraction line installed midway along the circulation line so that the extraction speed is a predetermined ratio to the circulation speed of the crude oil sludge-containing material, and supply it to the decanter centrifuge 1.

[0036] Specifically, as illustrated in FIG. 12(b), the crude oil sludge-containing material (crude oil sludge S) obtained by the method shown in FIG. 11(b) is stored at a predetermined temperature in a storage tank 200 having a heating means (not shown), and the crude oil sludge-containing material stored in the storage tank 200 is circulated through an external circulation line R provided outside the storage tank 200. ２ Pump P ５ circulating the water back to the sending storage tank 200 using the external circulation line R ２ One example of a method is to extract a portion of the crude oil sludge-containing material circulating through the circulation line from an extraction line installed midway through the circulation line so that the extraction speed is a predetermined ratio to the circulation speed of the crude oil sludge-containing material, and supply it to the decanter centrifuge 1.

[0037] The storage temperature of the crude oil sludge-containing material (mixture m and crude oil sludge S in the examples shown in Figures 12(a) and 12(b)) in the storage tank is preferably 40 to 200°C, more preferably 50 to 150°C, and even more preferably 60 to 100°C.

[0038] The external circulation line (the external circulation line R in the examples shown in FIGS. 12(a) and 12(b)) １ and external circulation line R ２ The circulation rate of the crude oil sludge-containing material circulated through the reactor is preferably 5 to 50 kL / h, more preferably 10 to 50 kL / h, and even more preferably 20 to 50 kL / h.

[0039] The external circulation line (the external circulation line R in the examples shown in FIGS. 12(a) and 12(b)) １ and external circulation line R ２ The feed rate at which a portion of the crude oil sludge-containing material circulating in the external circulation line is extracted from an extraction line installed midway through the circulation line and supplied to the decanter-type centrifuge is preferably 20 to 60% of the circulation rate of the crude oil sludge-containing material circulating in the external circulation line, more preferably 30 to 60%, and even more preferably 30 to 50% of the circulation rate of the crude oil sludge-containing material circulating in the external circulation line.

[0040] By withdrawing a portion of the crude oil sludge-containing material circulating in the external circulation line from an extraction line installed midway in the circulation line and supplying it to the decanter centrifuge at a supply speed within the above range, the crude oil sludge-containing material can be continuously supplied to the decanter centrifuge in a state in which the constituent components of the crude oil sludge-containing material are sufficiently dispersed and homogenized.

[0041] In the method for recovering oil from crude oil sludge according to the present invention, the crude oil sludge is fed to a decanter centrifuge and centrifuged, whereby the sludge is separated in the separation zone of the decanter centrifuge into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and an aqueous layer.

[0042] The recovered oil forming the first layer corresponds to the oil in the crude oil sludge when the crude oil sludge-containing material consists solely of crude oil sludge, and corresponds to the mixture of oil and crude oil in the crude oil sludge when the crude oil sludge-containing material is a mixture of crude oil sludge and crude oil. The heavy hydrocarbons forming the second layer correspond to heavy hydrocarbons such as asphaltene in the crude oil sludge. The water forming the aqueous layer corresponds to the water in the crude oil sludge. The aqueous layer may contain a metal chloride salt at a concentration of 3.0% to 5.0% by mass, preferably 3.5% to 4.8% by mass, and more preferably 4.0% to 4.7% by mass. The metal chloride salt may be one or more selected from sodium chloride, magnesium chloride, calcium chloride, etc. Having the metal chloride content in the aqueous layer within the above range is preferred because it improves oil separation. In the present application, the concentration of the metal chloride salt refers to a value measured in accordance with the provisions of JIS K 2601. Furthermore, in the separation zone of the decanter centrifuge, solid matter may precipitate below the aqueous layer, and examples of such solid matter include one or more selected from metals such as iron in crude oil sludge, sand, drilling cuttings, etc. Furthermore, the density of the aqueous layer (80°C) is usually 1.010 to 1.040 g / cm. ３ The density of the water layer within the above range is preferred because it allows for better oil separation.

[0043] In the method for recovering oil from crude oil sludge according to the present invention, the temperature at which the crude oil sludge-containing material is centrifuged using a decanter centrifuge is 40 to 200° C., preferably 50 to 150° C., and more preferably 60 to 100° C. By keeping the centrifugation temperature within the above range, it is possible to suppress the loss of light fractions during centrifugation and to perform the centrifugation in an appropriate manner without solidifying the crude oil sludge-containing material or significantly reducing the fluidity of the crude oil sludge-containing material.

[0044] In the method for recovering oil from crude oil sludge according to the present invention, the decanter centrifuge has at least an inner cylinder having a material feed port formed therein for discharging the material containing crude oil sludge, which is the material to be treated, from the inside to the outside and feeding it to a separation region, and an outer cylinder which is provided coaxially with the inner cylinder so as to surround the inner cylinder on the outside and has a solids discharge port formed therein for discharging heavy hydrocarbons from the inside to the outside, and which forms a separation region between the inner cylinder and the outer cylinder.

[0045] In the method for recovering oil from crude oil sludge according to the present invention, the decanter centrifuge preferably comprises: an inner cylinder having a material feed port formed therein for discharging the material containing crude oil sludge, which is the material to be treated, from the inside to the outside and supplying it to a separation zone; an outer cylinder which is arranged coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and has a solids discharge port formed therein for discharging heavy hydrocarbons from the inside to the outside, and which forms a separation zone between the inner cylinder and the outer cylinder; a screw plate wound helically around the outer wall of the inner cylinder; and an outer cylinder fixing member which is arranged on one end side of the separation zone (the side where the first layer consisting of recovered oil, part of the second layer consisting of heavy hydrocarbons, and the water layer are discharged from the separation zone), and which has a light component discharge path formed near the inner cylinder for discharging the recovered oil, and a heavy component discharge path formed near the outer cylinder for discharging water and heavy hydrocarbons.

[0046] A decanter centrifuge used to carry out the method for recovering oil from crude oil sludge according to the present invention will be described below with reference to Figure 1. Figure 1 is a schematic cross-sectional view of an example of a decanter centrifuge. In Figure 1, the decanter centrifuge 1 has an inner cylinder 2, an outer cylinder 3, an inner cylinder rotating shaft 23, an outer cylinder rotating shaft 24, a gearbox 13, a screw plate 7, and an outer cylinder fixing member 25 having a partition wall 10.

[0047] The inner cylinder 2 is a cylindrical member and is attached rotatably around the inner cylinder rotation shaft 23. A hollow material supply pipe 27 is connected to the material supply side of the inner cylinder 2 for supplying the material to be treated, which is crude oil sludge-containing material 29, into the inner cylinder 2. An inner cylinder fixing member 26 is provided on the side of the inner cylinder 2 opposite the material supply side for closing the side of the inner cylinder 2 opposite the material supply side for fixing the inner cylinder 2 to the inner cylinder rotation shaft 23. The inner cylinder 2 is formed with a plurality of material supply ports 4 in the circumferential direction of the inner cylinder 2 for discharging the material to be treated, which is crude oil sludge-containing material 29, supplied inside from the inside to the outside and supplying it to the separation region 6. The position, number, and size of the material supply pipes 27 formed in the inner cylinder are selected as appropriate.

[0048] The outer cylinder 3 is a cylindrical member and is provided coaxially with the inner cylinder 2 so as to surround the outer cylinder 2. The outer cylinder 3 is rotatably attached around the outer cylinder rotation shaft 24. An outer cylinder fixing member 25 is provided on the side of the outer cylinder 3 opposite the workpiece supply side (the side where the workpiece supply pipe 27 is provided) to close the side of the outer cylinder 3 opposite the workpiece supply side and to fix the outer cylinder 3 to the outer cylinder rotation shaft 24. The outer cylinder 3 also has a solids discharge port 5 for discharging solids. The outer cylinder fixing member 25 is provided on one end of the separation region 6 (the side where the first layer consisting of recovered oil, part of the second layer consisting of heavy hydrocarbons, and the water layer are discharged from the separation region), and the solids discharge port 5 is provided on the other end of the separation region (the side where the remainder of the second layer consisting of heavy hydrocarbons is discharged from the separation region). The number and size of the solid discharge ports 5 formed in the outer cylinder 3 can be selected appropriately, and can be provided at a position where the first layer made of recovered oil, which will be described later, will not be discharged.

[0049] The inner cylinder 2 is disposed inside the outer cylinder 3 , so that a separation region 6 is formed between the inner cylinder 2 and the outer cylinder 3 .

[0050] A spirally wound screw plate 7 is provided on the outer wall of the inner cylinder 2. The screw plate 7 is a member for transporting solid matter present between the inner cylinder 2 and the outer cylinder 3 to the solids discharge port 5 of the outer cylinder by rotating the inner cylinder 2 around its axis relative to the outer cylinder 3. Therefore, the screw plate 7 has a spiral shape such that solid matter such as heavy hydrocarbons present between the inner cylinder 2 and the outer cylinder 3 is transported to the solids discharge port 5 of the outer cylinder by rotating the inner cylinder 2 around its axis relative to the outer cylinder 3.

[0051] The partition wall 10 is a member for separating the discharge side of the light fraction (recovered oil) from the discharge side of the heavy fraction (water and heavy hydrocarbons) in the separation region 6 formed between the inner tube 2 and the outer tube 3. The partition wall 10 is provided with a light fraction discharge path 38 having a light fraction discharge port 381 disposed so as to be closer to the inner tube when installed (as also shown in FIG. 2 ), and a heavy fraction discharge path 37 having a heavy fraction discharge port 371 disposed so as to be closer to the outer tube when installed. The partition wall 10 is installed in the circumferential direction of the inner tube 2 and the outer tube 3. In the embodiment shown in FIG. 1 , the partition wall 10 is integrally formed with the outer tube fixing member 25. Crude oil sludge-containing matter is a mixture containing recovered oil, heavy hydrocarbons, and water. When this crude oil sludge-containing matter is centrifuged, it separates into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and a water layer due to differences in specific gravity in the separation region of the decanter centrifuge. During centrifugation, the first layer is discharged from the separation region into the light component discharge path 38, and the recovered oil that formed the first layer is discharged through the light component discharge path 38 into the light component discharge space 142. During centrifugation, the water layer and at least a portion of the second layer are discharged from the separation region into the heavy component discharge path 37, and the water and heavy hydrocarbons that form the water layer and the second layer are discharged through the heavy component discharge path 37 into the heavy component discharge space 141.

[0052] Referring to Figure 2, the light component discharge path (discharge path for recovered oil components) 38 and the heavy component discharge path (discharge path for moisture and heavy hydrocarbons) 37 will be described. Figure 2 is a schematic diagram showing the outer cylinder fixing member 25 in Figure 1, where Figure 2(a) is a view of the outer cylinder fixing member 25 in Figure 1 from the separation region 6 side, and Figure 2(b) is a cross-sectional view taken along line A-A' in Figure 2(a). In the outer cylinder fixing member 25, the portion facing the space between the outer cylinder and the inner cylinder is the partition wall 10. In the embodiment shown in Figure 2, the partition wall 10 is integrally formed with the outer cylinder fixing member 25. A plurality of light component discharge ports 381 are formed concentrically with the outer periphery of the partition wall 10 on the surface of the outer tube fixing member 25 facing the partition wall 10, and a communication passage 382 connecting the light component discharge ports 381 with the light component discharge space 142 and a light component discharge port 384 for discharging the light components into the light component discharge space 142 are formed inside the outer tube fixing member 25. The path including the light component discharge ports 381, the communication passage 382, ​​and the light component discharge ports 384 is the light component discharge path 38. Furthermore, a plurality of heavy component discharge ports 371 are formed concentrically with the outer periphery of the partition wall 10 on the surface of the outer cylinder fixing member 25 facing the partition wall 10 and on the outer peripheral side of the light component discharge port 381, and a communication passage 372 connecting the heavy component discharge ports 371 with the heavy component discharge space 141 and a heavy component discharge port 374 for discharging the heavy components into the heavy component discharge space 141 are formed inside the outer cylinder fixing member 25. The path including the heavy component discharge ports 371, the communication passage 372, and the heavy component discharge port 374 constitutes the heavy component discharge path 37.

[0053] As shown in Figure 2(b) , the partition wall 10 defines one end of the separation region 6 at least near the heavy component discharge port 371 and has a baffle 11 that restricts the discharge of heavy components (water and heavy hydrocarbons) from the separation region 6 to the heavy component discharge path 37. Also, as shown in Figure 2(b) , a weir 373 is provided in a part of the communication passage 372 so as to communicate with the separation region 6 and adjacent to the baffle 11. As will be described later, during centrifugation, the heavy components (water and heavy hydrocarbons) flowing out of the separation region 6 pass over the baffle 11 and flow into the communication passage 372, are retained at the weir 373, and then are discharged to the outside (heavy component discharge space 141) from a heavy component discharge port 374 provided at the end of the communication passage 372 and communicated with the weir 373.

[0054] 1 is connected to a drive unit (not shown), and is rotatably attached by being supported by bearing 21 on the side where the material is fed, and by having an outer cylinder rotating shaft 24, fixed via an outer cylinder fixing member 25, supported by bearing 22 on the side opposite the side where the material is fed. Furthermore, inner cylinder 2 is rotatably attached by being supported by bearing 18 on the side where the material is fed, and by being supported by bearing 19 on the side opposite the side where the material is fed.

[0055] The outer cylinder rotating shaft 24 shown in Fig. 1 is hollow, with one end connected to the gear box 13 and the other end to which an outer cylinder fixing member 25 is fixed. The inner cylinder rotating shaft 23 is disposed inside the outer cylinder rotating shaft 24, with one end connected to the gear box 13 and the other end to which an inner cylinder fixing member 26 is fixed. The gear box 13 generates a rotational speed difference between the outer cylinder 3 and the inner cylinder 2, and transmits power. Therefore, when the outer cylinder 3 is rotated about its axis by the drive device, the inner cylinder 2 rotates about its axis at a rotational speed slightly slower than that of the outer cylinder 3.

[0056] A housing 20 is provided to surround the outside of the outer cylinder 3 shown in FIG. 1 . A solids discharge space 16 through which solids are discharged from the outer cylinder 3 is provided on the feed side of the material to be treated in the housing 20, and a solids discharge port 17 is also formed for discharging the solids to the outside of the decanter centrifuge 1. On the side opposite the feed side of the material to be treated in the housing 20, a light-component discharge space 142 through which light components (recovered oil components) are discharged from the outer cylinder 3 and a heavy-component discharge space 141 through which heavy components (water and heavy hydrocarbons) are discharged from the outer cylinder 3 are provided. The light-component discharge space 142 and the heavy-component discharge space 141 are separated within the housing 20 to prevent the light and heavy components from mixing. In addition, a light-component discharge port 152 for discharging the light components to the outside of the decanter centrifuge 1 and a heavy-component discharge port 151 for discharging the heavy components to the outside of the decanter centrifuge 1 are also formed.

[0057] Next, the centrifugal treatment of a material containing crude oil sludge will be explained using the decanter centrifuge 1 shown in Figure 1 as an example. With the temperature inside the decanter centrifuge 1 maintained at a predetermined treatment temperature and the inner cylinder 2 and outer cylinder 3 each rotating around their axes at a predetermined rotational speed, a material containing crude oil sludge 29 treated at the predetermined treatment temperature is supplied to the inside of the inner cylinder 2 through the material supply pipe 27. The material containing crude oil sludge 29 supplied into the inner cylinder 2 passes through the material supply port 4 and is supplied to the separation region 6 formed between the inner cylinder 2 and the outer cylinder 3.

[0058] The crude oil sludge-containing material 29 supplied to the separation region 6 is centrifuged in the separation region 6. The centrifugal separation process will now be described with reference to FIGS. 3 to 7. FIG. 3 is a schematic diagram showing the separation state after centrifuging the crude oil sludge-containing material 29 at a predetermined processing temperature using a batch centrifuge. FIG. 4 is an enlarged view of the lower part of the decanter centrifuge 1 shown in FIG. 1, showing the state in which each layer is separated in the separation region 6. FIG. 5 is a diagram showing the range of the separation region 6 in FIG. 4. FIG. 6 is an enlarged view of the upper part of the decanter centrifuge 1 shown in FIG. 1, showing the state in which each layer is separated in the separation region 6. The components of the decanter centrifuge shown in FIG. 6 basically correspond to those shown in FIG. 4, except for the fact that a light-component discharge path 38 is shown instead of the heavy-component discharge path 37. FIG. 7 is a diagram showing the range of the separation region 6 in FIG. 6.

[0059] As shown in FIG. 3, when centrifuging is performed using a batch centrifuge, crude oil sludge-containing material 29 is centrifuged in a centrifuge tube 30, and due to differences in specific gravity, it separates into, from the top, a first layer 34 consisting of recovered oil 31, a second layer 35 consisting of heavy hydrocarbons 32, and an aqueous layer 36 consisting of water 33, and in some cases, a solid material 28 consisting of sand or the like.

[0060] When centrifuged using a decanter centrifuge, as shown in Figures 4 and 6, in the separation region 6, the mixture separates into three layers from the inner cylinder 2 side, in other words, from the side with the lowest specific gravity: a first layer 34 (comprising recovered oil 31), a second layer 35 (comprising heavy hydrocarbons 32), and an aqueous layer 36 (comprising moisture 33). In addition, solids 28 such as sand may settle in the aqueous layer 36 on the outer cylinder 3 side near the position where the material supply port 4 is formed. Here, the separation region 6 corresponds to the entire region where the first layer 34, second layer 35, and aqueous layer 36 are formed, as shown by the diagonal lines between the inner cylinder 2 and the outer cylinder 3 in Figures 5 and 7.

[0061] Then, by centrifugal separation using a decanter centrifuge, the crude oil sludge-containing material 29 is separated into a first layer 34, a second layer 35, an aqueous layer 36, and optionally solids 28 within the separation region 6. While continuously supplying the crude oil sludge-containing material 29 to the separation region 6, the first layer 34 is discharged from the separation region 6 as recovered oil 31 through a light fraction discharge path 38 formed in the outer cylinder fixing member 25 (as shown in Figure 6), and part of the aqueous layer 36 and the second layer 35 are discharged from the separation region 6 as a mixture of water 33 and heavy hydrocarbons 32 through a heavy fraction discharge path 37 formed in the outer cylinder fixing member 25 (as shown in Figure 4). The remainder of the second layer 35, together with a solid material 40 consisting of a mixture of solids 28 and heavy hydrocarbons 32, is discharged from the solids discharge port 5 as heavy hydrocarbons 32 to the separation region 6.

[0062] At this time, as the crude oil sludge-containing material 29 is continuously supplied into the separation area 6, the recovered oil is continuously separated by centrifugation in the separation area 6, and the first layer 34 increases accordingly, and the increased recovered oil 31 is discharged outside the separation area 6 from the light fraction discharge port 384 via the light fraction discharge path 38 (as shown in Figure 6).

[0063] Furthermore, as the crude oil sludge-containing material 29 is continuously supplied into the separation region 6, the water and the second layer are continuously separated by centrifugation in the separation region 6, and the water layer 36 and the second layer 35 increase accordingly, and the increased water 33 and at least a portion of the heavy hydrocarbons 32 are released outside the separation region 6 as heavy components (water 33 and heavy hydrocarbons 32) via the heavy component discharge path 37.

[0064] As shown in Figure 4 (and Figure 2(b)), at least a portion of the partition wall 10 is provided with a baffle 11 that defines one end of the separation region 6 and restricts the discharge of heavy components (water 33 and heavy hydrocarbons 32) from the separation region 6. Also, as shown in Figure 4 (and Figure 2(b)), a weir 373 is provided in a part of the communication passage 372 so as to communicate with the separation region 6 and adjacent to the baffle 11. During centrifugation, the heavy components (water 33 and heavy hydrocarbons 32) that have flowed out of the separation region 6 pass over the baffle 11 and flow into the communication passage 372, remain at the weir 373 that forms part of the communication passage 372, and are then discharged to the outside from a heavy component discharge port 374 that is provided at the end of the communication passage 372 and communicates with the weir 373.

[0065] 4, by continuously supplying the crude oil sludge-containing material 29 into the separation region 6, solids 28 such as sand are easily separated by centrifugation in the separation region 6, and the separated solids 28 are easily settled on the outer cylinder 3 side in the aqueous layer 36 of the separation region 6. By continuously supplying the crude oil sludge-containing material 29 into the separation region 6, heavy hydrocarbons 32 are continuously separated by centrifugation in the separation region 6, and the second layer 35 increases accordingly. The settled solids 28 are then transported by the screw plate to the other end 39 of the second layer 35, where they come into contact with the heavy hydrocarbons 32 and form solids 40. In this way, the remainder of the second layer 35 discharged from the heavy component discharge path 37 (or the remainder of the second layer 35 and the solid component 40, if any) is produced is transported by the screw plate to the solid component discharge outlet 5 of the outer cylinder, discharged to the outside of the separation region 6, and discharged as heavy hydrocarbons 32 from the solid component discharge outlet 5 of the outer cylinder to the outside of the outer cylinder 3, possibly together with the solid component 40 consisting of a mixture of solid components 28 and heavy hydrocarbons 32.

[0066] In this way, at least a portion of the heavy hydrocarbons 32 constituting the second layer 35 is discharged together with the moisture 33 from the heavy hydrocarbon discharge path 37, and the remainder is discharged from the solids discharge port 5 of the outer cylinder. This distributes the discharge paths for the heavy hydrocarbons 32, and effectively prevents the heavy hydrocarbons 32 from adhering to the screw plate and from clogging the solids discharge port 5 with the heavy hydrocarbons 32.

[0067] In the method for recovering oil from crude oil sludge according to the present invention, it is preferable that 50 to 99 mass% of the heavy hydrocarbons constituting the second layer are discharged from the heavy component outlet, more preferably 60 to 99 mass% of them are discharged from the heavy component outlet, and even more preferably 70 to 99 mass% of them are discharged from the heavy component outlet.

[0068] As described above, in the method for recovering oil from crude oil sludge according to the present invention, (i) the first layer 34 is discharged to the outside of the separation region 6 from the light component discharge port 384 of the light component discharge path 38 provided on the light component side at one end of the separation region 6, thereby recovering the recovered oil component 31; and (ii) at least a portion of the aqueous layer 36 and the second layer 35 is discharged from the heavy component side at one end of the separation region 6 into the heavy component discharge path 37, over the baffle 11 that defines one end of the separation region 6, and then retained inside the weir 373 that is provided in the heavy component discharge path 37 adjacent to the baffle 11 and communicates with the separation region 6; and then at least a portion of the aqueous layer 36 and the second layer 35 is discharged from the heavy component discharge port 374 provided in the heavy component discharge path 37, thereby recovering the water 33 and heavy hydrocarbons 32; (iii) At the other end of the separation zone 6, the remainder of the heavy hydrocarbons 32, optionally together with solids 40 consisting of the heavy hydrocarbons 32 and the solids 28, are discharged out of the separation zone 6 and recovered.

[0069] In this way, the decanter centrifuge 1 is used to centrifuge the crude oil sludge-containing material, thereby obtaining a light fraction (recovered oil fraction 31), a heavy fraction (a mixture of water 33 and heavy hydrocarbons 32), and solid heavy hydrocarbons 32 (possibly together with solid matter 40).

[0070] In the method for recovering oil from crude oil sludge according to the present invention, when a crude oil sludge-containing material is centrifuged, a sieve containing a sieve of the following formula (I) is added to the sieve. (where r ｉ ': Distance from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface (m) r Ａ　 r: Distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ｂ　 ρ: Distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom of the discharged liquid layer discharged from the light fraction discharge port Ａ : Moisture density (kg / m ３ ) ρ Ｂ : Density of recovered oil (kg / m ３ ) and h Ａ :The following formula and the following formula: The thickness (m) of the liquid layer discharged from the heavy component discharge port, calculated by Ａ : Flow rate of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge (m ３ / s), v Ａ : Outflow velocity of the discharged liquid at the heavy fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the heavy fraction discharge port, N Ａ : number of heavy component outlets, C: outflow coefficient, S Ａ : Vertical cross-sectional area (m) of the discharged liquid layer discharged from the heavy fraction discharge port with respect to the center of the rotation axis of the decanter centrifuge ２ ) is) h Ｂ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, calculated by Ｂ : Flow rate of recovered oil discharged from the light fraction discharge port of the decanter centrifuge (m ３ / s), v Ｂ : Outflow velocity of the discharged liquid at the light fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the light fraction discharge port, N Ｂ : number of light component outlets, C: outflow coefficient, S Ｂ : Vertical cross-sectional area (m) of the discharged liquid layer discharged from the light fraction discharge port with respect to the center of the rotation axis of the decanter centrifuge ２ )), the following formula (II) (the distance from the center of the rotation axis of the decanter centrifuge to the end of the baffle plate on the water layer side - r ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ ) (m) (II) is controlled to be 0.170 to 0.450 during the centrifugation treatment.

[0071] The centrifugal separation process controlled by the above formulas (I) and (II) will be described below with reference to the accompanying drawings. Fig. 8 is an enlarged view of the vicinity of the heavy-component discharge path 37 in the decanter centrifuge 1 shown in Fig. 1, and is a schematic cross-sectional view for explaining the positional relationship between the vicinity of the heavy-component discharge path 37 and the center Ax of the inner tube rotating shaft 23 or the outer tube rotating shaft 24. Fig. 9 is an enlarged view of the vicinity of the light-component discharge path 38 in the decanter centrifuge shown in Fig. 1, and is a schematic cross-sectional view for explaining the positional relationship between the vicinity of the light-component discharge path 38 and the center Ax of the inner tube rotating shaft 23 or the outer tube rotating shaft 24. 10A is a front view of the outer tube fixing member 25 in FIG. 1 from the heavy component discharge port 374 to the light component discharge port 384 side (the discharge side of the discharged liquid from the heavy component discharge port 374 to the light component discharge port 384). FIG. 10B is an enlarged view of the heavy component discharge port 374 located at the lower end of the outer tube fixing member 25 in FIG. 10A, and FIG. 10C is an enlarged view of the light component discharge port 384 located at the upper end of the outer tube fixing member 25 in FIG. 10A.

[0072] The following formula (I) r represented by ｉ ' means "the distance (m) from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface."

[0073] In the method for recovering oil from crude oil sludge according to the present invention, the estimated oil-water interface refers to the oil-water interface (the interface between the recovered oil phase and the aqueous phase) when it is assumed that the crude oil sludge content separates into only two phases in the separation zone of the decanter centrifuge: a first layer (recovered oil phase) consisting of recovered oil and an aqueous layer (aqueous phase) consisting of water. As described above, the crude oil sludge content contains heavy hydrocarbons in addition to the recovered oil and water. Therefore, in the separation zone of the decanter centrifuge, a second layer (heavy hydrocarbon phase) consisting of heavy hydrocarbons will actually be formed in addition to the first layer (recovered oil phase) consisting of recovered oil and the aqueous layer (aqueous phase). However, since heavy hydrocarbons have a density intermediate between that of the recovered oil and water, it is assumed that the second layer consisting of heavy hydrocarbons will be located near the estimated oil-water interface.

[0074] Furthermore, when the centrifugal separation of the crude oil sludge-containing material is continued using a decanter centrifuge, it is assumed that the position and thickness of the second layer consisting of heavy hydrocarbons will fluctuate periodically as follows: That is, taking the decanter centrifuge shown in Figure 8 as an example, when the centrifugal separation of the crude oil sludge-containing material is continued using the decanter centrifuge, the second layer consisting of heavy hydrocarbons 35 will increase in thickness as the supply of heavy hydrocarbons increases due to the centrifugal separation of the crude oil sludge-containing material, and when one end of the second layer reaches the water layer side end 11e of the baffle, the heavy hydrocarbons will be discharged together with the water that forms the water layer 36 through the heavy component discharge path 37, and the density of the fluid in the heavy component discharge path 37 will decrease, causing the position of the interface between the first layer 34 consisting of recovered oil and the second layer 35 consisting of heavy hydrocarbons to move closer to the water layer side end of the baffle than the position of the estimated oil-water interface Ep, and the thickness of the second layer 35 consisting of heavy hydrocarbons will also decrease. Thereafter, when a certain amount of the heavy hydrocarbons constituting the second layer 35 has been discharged, the amount of heavy hydrocarbons discharged from the heavy component discharge path 37 decreases, the density of the fluid in the heavy component discharge path 37 returns to its original state, and the position of the second layer consisting of heavy hydrocarbons returns to the vicinity of the estimated oil-water interface Ep. Then, if the crude oil sludge-containing material is continuously supplied to the decanter centrifuge and the centrifugation process is continuously performed, the second layer 35 consisting of heavy hydrocarbons will cyclically repeat the above-mentioned movement.

[0075] 8 , the method for recovering oil from crude oil sludge according to the present invention will be described in detail below. Taking the decanter centrifuge shown in FIG. 8 as an example, the closer the position of the estimated oil-water interface Ep, i.e., the estimated position of the second layer 35 consisting of heavy hydrocarbons, to the water layer-side end of the baffle 11e, the more easily the heavy hydrocarbons constituting the second layer are released together with water from the heavy-component discharge port 374, and the less likely it is that heavy hydrocarbons will adhere to the screw plate or that the solids (a mixture of heavy hydrocarbons and solids such as sand) will clog the solids discharge port. Meanwhile, the closer the position of the estimated oil-water interface Ep, i.e., the estimated position of the second layer 35 consisting of heavy hydrocarbons, to the water layer-side end 11e of the baffle, the more likely it is that the interface between the first layer 34 consisting of recovered oil and the second layer 35 consisting of heavy hydrocarbons will reach the water layer-side end 11e of the baffle during the periodic fluctuations, and the more likely it is that the recovered oil 31 will be discharged together with water 33 from the heavy-component discharge port 374. In addition, when the recovered oil constituting the first layer passes over the water layer side end 11e of the baffle and is discharged into the heavy component discharge path 37, the density of the fluid in the heavy component discharge path 37 drops to a value close to the density of the first layer 34, and the distance from the rotation axis center Ax of the decanter centrifuge to the liquid surface of the first layer 34 increases, so that the recovered oil cannot be discharged from the light component discharge port 384, and the centrifugal separation process of the crude oil sludge-containing material cannot be continued. The method for recovering oil from crude oil sludge-containing material according to the present invention uses the distance r from the rotation axis center of the decanter centrifuge to the estimated oil-water interface as a variable indicating the location of the second layer consisting of heavy hydrocarbons. ｉ '(m) and this distance r ｉ By controlling '(m) within an appropriate range, it is possible to suppress the discharge of recovered oil together with water, while also making it possible to discharge part of the heavy hydrocarbons together with water outside the separation zone before the heavy hydrocarbons adhere to the screw plate or before the solids (a mixture of heavy hydrocarbons and solids such as sand) clog the solids discharge port.

[0076] In addition, in the method for recovering oil from crude oil sludge according to the present invention, the center of the rotation axis of the decanter centrifuge refers to the center of the rotation axis of the inner cylinder or the center of the rotation axis of the outer cylinder that constitutes the decanter centrifuge. That is, in the method for recovering oil from crude oil sludge according to the present invention, the inner and outer cylinders that constitute the decanter centrifuge are arranged coaxially, and the center of the rotation axis of the inner cylinder is the same as the center of the rotation axis of the outer cylinder, so either the center of the rotation axis of the inner cylinder or the center of the rotation axis of the outer cylinder corresponds to the center of the rotation axis of the decanter centrifuge. In the example shown in Figure 8 (and Figure 1), the center of the inner cylinder rotation axis 23 and the center of the outer cylinder rotation axis 24 are the same, and either rotation axis center can be expressed as the rotation axis center Ax. Therefore, in the example shown in Figure 8, ｉ The length indicated by ' (m) corresponds to the distance between the center of the rotation axis Ax of the decanter centrifuge and the estimated oil-water interface Ep. In the method for recovering oil from crude oil sludge according to the present invention, the estimated oil-water interface must be located at a predetermined position, in other words, the distance r between the center of the rotation axis of the decanter centrifuge and the estimated interface between the first layer and the water layer (estimated oil-water interface) must be ｉ By controlling ' within a predetermined range, the recovered oil obtained can be recovered suitably, while at the same time, the heavy hydrocarbons constituting the second layer can be effectively discharged together with moisture from the heavy hydrocarbon discharge path before at least a portion of them adheres to the screw plate or before the solids (a mixture of heavy hydrocarbons and solids such as sand) cause clogging of the solids discharge port, thereby effectively preventing clogging of the solids discharge port by heavy hydrocarbons.

[0077] In formula (I), r Ａ means "the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port." In this application document, "the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port" means the deepest part of the discharged liquid layer discharged from the heavy fraction discharge port. In the examples shown in Figures 8 and 10(b), D Ｗ corresponds to the discharge surface of the discharged liquid layer containing water and heavy hydrocarbons discharged from the heavy component discharge port 374 in the direction parallel to the rotation axis of the outer cylinder 3, and this discharge surface D ＷIn contrast, in the examples shown in Figures 8 and 10(b), the bottom surface D of the discharged liquid layer discharged from the heavy component discharge port ＷＤ corresponds to the deepest part of the discharged liquid layer at the heavy component discharge port 374, and constitutes the lower end of the discharged liquid layer at the heavy component discharge port 374. As shown in FIG. 10(b), the heavy component discharge port 374 is usually provided with a cap C for adjusting the outflow amount from the heavy component discharge port 374. Depending on the shape of this cap C, the bottom surface D ＷＤ and the bottom surface D of the discharged liquid layer discharged from the heavy component discharge port. ＷＤ The cap C is detachably attached to the heavy component discharge port 374, and by replacing the cap C, the bottom surface D of the discharged liquid layer discharged from the heavy component discharge port can be adjusted. ＷＤ and the bottom surface D of the discharged liquid layer discharged from the heavy component discharge port. ＷＤ In the example shown in FIG. Ａ The center of the rotation axis Ax of the decanter centrifuge shown in (m) and the bottom surface D of the discharged liquid layer discharged from the heavy fraction discharge port ＷＤ The distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port corresponds to the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port.

[0078] In formula (I), r Ｂ means "the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port." In the present application, "the bottom surface of the discharged liquid layer discharged from the light fraction discharge port" means the deepest part of the discharged liquid layer discharged from the light fraction discharge port. In the examples shown in Figures 9 and 10(c), D Ｏ corresponds to the discharge surface of the discharged liquid layer containing the recovered oil component discharged from the light component discharge port 384 in the direction parallel to the rotation axis of the outer cylinder 3, and this discharge surface D Ｏ 9 and 10(c), the bottom surface D of the discharged liquid layer discharged from the light fraction discharge port 384 is ＯＤcorresponds to the deepest part of the discharged liquid layer at the light fraction discharge port 384, and constitutes the lower end of the discharged liquid layer at the light fraction discharge port 384. As shown in FIG. 10(c), the light fraction discharge port 384 is usually provided with a cap C for adjusting the outflow amount from the light fraction discharge port 384, and the shape of this cap C determines the depth of the bottom D of the discharged liquid layer discharged from the light fraction discharge port. ＯＤ and the bottom surface D of the discharged liquid layer discharged from the light fraction discharge port. ＯＤ In the example shown in FIG. Ｂ The center of the rotation axis Ax of the decanter centrifuge shown in (m) and the bottom surface D of the discharged liquid layer discharged from the light fraction discharge port ＯＤ The distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port corresponds to the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port.

[0079] In formula (I), ρ Ａ is the density of water (kg / m ３ ) and ρ Ｂ is the density of the recovered oil (kg / m ３ ) means

[0080] In the examples shown in FIGS. 8 and 9, the density of the moisture 33 (kg / m ３ ) is ρ Ａ (kg / m ３ ) and the density of the recovered oil 31 (kg / m ３ ) is ρ Ｂ (kg / m ３ In the method for recovering oil from crude oil sludge according to the present invention, ρ Ａmeans the density measured using a hydrometer density tester conforming to the specifications of JIS B 7525 while heating the sample in a water bath to the same temperature as the centrifugation temperature (the temperature of the sample containing crude oil sludge supplied to the decanter centrifuge). Ｂ means the density measured using a float density tester conforming to the specifications of JIS B 7525 while heating the crude oil sludge-containing material to be centrifuged in a water bath at the same temperature as the centrifugation temperature (the temperature of the crude oil sludge-containing material supplied to the decanter centrifuge).

[0081] The flow rate Q of the discharged liquid (water and heavy hydrocarbons) discharged from the heavy fraction discharge port of the decanter centrifuge is Ａ (m ３ / s) is generally represented by the following formula: (However, Q Ａ : Flow rate of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge (m ３ / s), v Ａ : Outflow velocity of the discharged liquid at the heavy fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the heavy fraction discharge port, N Ａ : number of heavy component outlets, C: outflow coefficient, S Ａ : Vertical cross-sectional area (m) of the discharged liquid layer discharged from the heavy fraction discharge port with respect to the center of the rotation axis of the decanter centrifuge ２ ) is represented by

[0082] Here, the outflow velocity of the discharged liquid at the heavy component discharge port v Ａ Since the decanter centrifuge has a symmetrical structure around the center of the rotation axis, the pressure difference dp between the distance r from the center of the rotation axis of the decanter centrifuge to the discharge liquid at the heavy fraction discharge port and r + dr when a fluid with density ρ is rotating around the center axis of the decanter centrifuge at angular velocity ω, is given by It is expressed as:

[0083] The pressure p of the liquid discharged at the heavy fraction discharge port at a distance r from the center of the rotation axis of the decanter centrifuge is calculated by the above formula: dp = ρrω ２ dr is the distance r from the center axis of the decanter centrifuge at the heavy fraction discharge port. Ａ -h Ａ the discharge surface D of the discharged liquid layer Ｗ By integrating from the distance r from the center of the rotation axis of the decanter centrifuge of the discharged liquid at the heavy fraction discharge port, the following equation can be obtained.

[0084] When the discharged liquid flows out from the heavy fraction discharge port, if we assume that all pressure is converted into kinetic energy according to Bernoulle's theorem, the discharged liquid flow rate at the heavy fraction discharge port will be v Ａ is expressed by the following formula:

[0085] The above formula In the above formula Substituting the above, the flow rate Q of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge is Ａ (m ３ / s) is represented by the following formula (A): It is expressed by:

[0086] As mentioned above, h Ａ means the thickness (m) of the discharged liquid layer discharged from the heavy component discharge port, in other words, the distance from the discharge surface of the discharged liquid layer discharged from the heavy component discharge port to the bottom surface of the discharged liquid layer. Specifically, in the examples shown in Figures 8 and 10(b), h Ａis the thickness (m) of the discharged liquid layer discharged from the heavy component discharge port, that is, the discharge surface D of the discharged liquid layer discharged from the heavy component discharge port Ｗ From the bottom surface D of the released liquid layer ＷＤ In addition, in the above formula (A), S Ａ is the vertical cross-sectional area (m ２ ) and in the example shown in FIG. 10(b), the discharge area S of the discharge flow at the heavy component discharge port 374 when the heavy component discharge port 374 is viewed from the front from the heavy component discharge port 374 side (the discharge side of the discharged liquid at the heavy component discharge port 374) Ａ is equivalent to

[0087] Here, the flow rate Q of the discharged stream discharged from the heavy component discharge port Ａ The angular velocity ω of the outer cylinder of the decanter centrifuge is determined by the operating conditions, and the number of heavy fraction outlets N Ａ and the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port. Ａ is determined by the structure of the decanter centrifuge. The discharge coefficient C is 0.62 when the treatment target is a heavy oil content such as crude oil sludge containing material and the Reynolds number Re is 8 or more, and 0.25Re when the treatment target is a heavy oil content such as crude oil sludge containing material and the Reynolds number Re is less than 8. ０．４５ It is known that the discharge coefficient is 0.62 (see "On the discharge coefficient of a weir in a centrifugal field" by Yoshitoshi Oyama and Shiro Ito, Chemical Machinery, Vol. 16, No. 2, pp. 47-50, published in 1952). Since the Reynolds number Re at the heavy fraction discharge port of a decanter centrifuge is usually 8 or more, the discharge coefficient is set to 0.62. For this reason, in the above formula (A), the thickness h of the discharged liquid layer at the heavy fraction discharge port is Ａ and the vertical cross-sectional area S of the discharged liquid layer at the heavy fraction discharge port Ａ are unknown variables, but since they have a one-to-one correspondence in which determining one determines the other, there is only one independent unknown variable, which can be uniquely determined by solving the above formula (A) (note that in formula (A), since the integral part is a definite integral, the integral variable "r" does not remain as a variable).

[0088] (The thickness of the discharged liquid layer at the heavy component discharge port h Ａ Calculation method 1 (h Ａ / r Ａ (1) In formula (A), first, h Ａ Assuming that, S is determined by Ａ The integral value of the right side is calculated using the trapezoidal rule with the integral range of Q on the left side of the equation (A). Ａ There will be a difference between the values ​​of Q and Q, but the absolute value (deviation) is within the tolerance (| (integral value of the right side - Q Ａ ) / Q Ａ |<0.001) or less Ａ is calculated using a root-finding algorithm such as the Newton-Raphson method.

[0089] (The thickness of the discharged liquid layer at the heavy component discharge port h Ａ Calculation method 2 (h Ａ / r Ａ ≦0.05)) Thickness h of the discharged liquid layer discharged from the heavy component discharge port Ａ is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port. Ａ is sufficiently small compared to Ａ / r Ａ ≦0.05), and the shape of the heavy fraction discharge port is such that the width of the discharged liquid layer can be considered constant within the integral range, the right side of equation (A) can be expressed as follows: Here, l Ａ is the width (m) of the bottom surface of the discharged liquid layer discharged from the heavy component discharge port, and integrating the right-hand side gives the following equation. where: It is. Ａ / r Ａ ≦0.05, i.e., h Ａ / r Ａ <<1, and approximate the right side of the above formula (B) to h Ａ By solving for, the following equation is derived, and h Ａ can be calculated.

[0090] The thickness of the discharged liquid layer at the heavy component discharge port h Ａ h in "Calculation Method 2"Ａ For clarity, the details of the calculation method are listed below.

[0091] In the method for recovering oil from crude oil sludge according to the present invention, first, the thickness h of the discharged liquid layer at the heavy component discharge port is measured. Ａ Using "Calculation Method 2" to calculate the thickness h Ａ (=h Ａ The thickness h Ａ ', h Ａ ' / r Ａ If the thickness of the discharged liquid layer at the heavy component discharge port is greater than 0.05, the thickness of the discharged liquid layer at the heavy component discharge port is Ａ Using "Calculation Method 1" to calculate the thickness h Ａ Recalculate h Ａ ' / r Ａ If the thickness is ≦0.05, the thickness h of the discharged liquid layer at the heavy component discharge port is Ａ The thickness h calculated using "Calculation Method 2" Ａ The thickness h that we want to obtain Ａ That is, the thickness of the discharged liquid layer at the heavy fraction discharge port h Ａ Since "Calculation method 2" is easier to calculate, "Thickness h of the discharged liquid layer at the heavy fraction discharge port" is used. Ａ Using "Calculation Method 2" to calculate the thickness h Ａ (=h Ａ ') is calculated provisionally, and the obtained thickness h Ａ (=h Ａ ') Based on the calculation results, the thickness of the discharged liquid layer at the heavy fraction discharge port h Ａ The following is required.

[0092] Furthermore, in formula (I), h Ｂ is expressed by the following formula: and the following formula: The thickness (m) of the discharged liquid layer discharged from the light fraction discharge port is calculated by the following formula (where Q Ｂ : Flow rate of recovered oil discharged from the light fraction discharge port of the decanter centrifuge (m ３ / s), v Ｂ: Outflow velocity of the discharged liquid at the light fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance from the center of the rotation axis of the decanter centrifuge to the discharged liquid at the light fraction discharge port, N Ｂ : number of light component outlets, C: outflow coefficient, S Ｂ : Vertical cross-sectional area (m) of the discharged liquid layer discharged from the light fraction discharge port with respect to the center of the rotation axis of the decanter centrifuge ２ )).

[0093] The above formula In the above formula Substituting the above, the flow rate Q of recovered oil discharged from the light fraction discharge port of the decanter centrifuge is Ｂ (m ３ / s) is represented by the following formula (C): As mentioned above, h Ｂ means the thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, in other words, the distance from the discharge surface of the discharged liquid layer discharged from the light fraction discharge port to the deepest part of the discharged liquid layer. Specifically, in the examples shown in Figures 9 and 10(c), h Ｂ is the thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, that is, the discharge surface D of the discharged liquid layer discharged from the light fraction discharge port Ｏ From the bottom surface D of the released liquid layer ＯＤ In addition, in the above formula (C), S Ｂ is the vertical cross-sectional area (m ２ ) and in the example shown in FIG. 10(c), the discharge area S of the discharge flow at the light component discharge port 384 when the light component discharge port 384 is viewed from the front from the light component discharge port 384 side (the discharge side of the discharge liquid at the light component discharge port 384) Ｂ is equivalent to

[0094] Here, the flow rate Q discharged from the light component discharge port Ｂ The angular velocity ω of the outer cylinder of the decanter centrifuge is determined by the operating conditions, and the number of light fraction outlets N Ｂ and the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ｂis determined by the structure of the decanter centrifuge. The discharge coefficient C is 0.62 when the treatment target is a heavy oil content such as crude oil sludge containing material and the Reynolds number Re is 8 or more, and 0.25Re when the treatment target is a heavy oil content such as crude oil sludge containing material and the Reynolds number Re is less than 8. ０．４５ It is known that the discharge coefficient is 0.62 (see "On the discharge coefficient of a weir in a centrifugal field" by Yoshitoshi Oyama and Shiro Ito, Chemical Machinery, Vol. 16, No. 2, pp. 47-50, published in 1952). Since the Reynolds number Re at the light fraction discharge port of a decanter centrifuge is usually 8 or more, the discharge coefficient is set to 0.62. Therefore, in the above formula (C), the thickness h of the discharged liquid layer discharged from the light fraction discharge port is Ｂ and the vertical cross-sectional area S of the discharged liquid layer discharged from the light fraction discharge port Ｂ These two variables are unknown, but since they have a one-to-one correspondence, where determining one determines the other, there is only one independent unknown variable, which can be uniquely determined by solving the above formula (C) (note that in formula (C), since the integral part is a definite integral, the integral variable "r" does not remain as a variable). The thickness h of the discharged liquid layer discharged from the light fraction discharge port is Ｂ Regarding the thickness of the discharged liquid layer discharged from the heavy component discharge port, h Ａ Similarly, "the thickness h of the discharged liquid layer at the light fraction discharge port" Ｂ Calculation method 1 (h Ｂ / r Ｂ >0.05) and "the thickness of the discharged liquid layer at the light fraction discharge port h Ｂ Calculation method 2 (h Ｂ / r Ｂ ≦0.05) and "the thickness h of the discharged liquid layer at the heavy component discharge port" Ａ Calculation method 1 (h Ａ / r Ａ >0.05) and "the thickness of the discharged liquid layer at the heavy fraction discharge port h Ａ Calculation method 2 (h Ａ / r Ａ ≦0.05)) can be calculated in the same manner as in

[0095] In the method for recovering oil from crude oil sludge according to the present invention, the following formula (II) (the distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ The centrifugation treatment is carried out while controlling the ratio represented by the following formula: ##EQU1## to be 0.170 to 0.450.

[0096] In the method for recovering oil from crude oil sludge according to the present invention, it is preferable to carry out centrifugation while controlling the ratio represented by formula (II) to be 0.170 to 0.450, more preferably 0.180 to 0.450, and even more preferably 0.180 to 0.440.

[0097] In the example shown in Fig. 8, the end 11e of the baffle 11 on the water layer 36 side corresponds to the "water layer side end of the baffle." Also, in the example shown in Fig. 8, as described above, the rotation axis center Ax of the inner cylinder 2 or the outer cylinder 3 corresponds to the "rotation axis center of the decanter centrifuge." Therefore, in the example shown in Fig. 8, the "distance (m) from the rotation axis center of the decanter centrifuge to the water layer side end of the baffle" is the distance D from the water layer side end 11e of the baffle to the rotation axis center Ax of the decanter centrifuge. ｅ Equivalent to (m).

[0098] In addition, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface ｉ ' (m) and the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ The details of (m) are as described above.

[0099] In the method for recovering oil from crude oil sludge according to the present invention, the decanter centrifuge is controlled and operated so that the ratio represented by formula (II) falls within the above range. That is, the variable in formula (I), "the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port," Ａ" and "The distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ "The distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface can be adjusted by adjusting at least one of the following: ｉ 10(b) and 10(c), the bottom D of the discharged liquid layer discharged from the heavy component discharge port 374 is controlled to be within a desired range, and the ratio expressed by the formula (II) is controlled to be a desired value. Specifically, as shown in FIG. 10(b) and FIG. 10(c), by appropriately replacing the caps C attached to the heavy component discharge port 374 and the light component discharge port 384, ＷＤ and the bottom surface D of the discharged liquid layer discharged from the light fraction discharge port 384 ＯＤ and thereby adjusting at least one of the positions selected from the variable "distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port" in formula (I). Ａ " and "The distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ In formula (II), at least one of the following can be adjusted: "the distance from the center of the rotation axis of the decanter centrifuge to the end of the baffle plate on the water layer side" and "the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port." Ｂ " is a fixed value determined by the structure of each decanter centrifuge used. Therefore, controlling the ratio expressed by formula (II) to be within a predetermined range means controlling the ratio r ｉ This is equivalent to controlling r' to be within a desired range (to obtain the effects of the present invention). ｉ The desired range of ' (the range in which the effects of the present invention can be obtained) varies depending on the structure and size of the decanter centrifuge used. Therefore, in the method for recovering oil from crude oil sludge according to the present invention, ｉ The range of the ratio represented by formula (II) is specified instead of the range of ', thereby making the method for recovering oil from crude oil sludge according to the present invention applicable regardless of the structure and size of the decanter centrifuge used.

[0100] According to the method for recovering oil from crude oil sludge of the present invention, by controlling the decanter centrifuge so that the specific ratio represented by formula (II) falls within a predetermined range, it is possible to suppress the recovered oil from being discharged together with water, and to discharge a portion of the heavy hydrocarbons together with water to the outside of the separation region before the heavy hydrocarbons adhere to the screw plate or before solids (a mixture of heavy hydrocarbons and solid matter such as sand) clog the solids discharge port, thereby enabling the oil from the crude oil sludge to be separated and recovered simply and continuously.

[0101] As described above, according to the method for recovering oil from crude oil sludge of the present invention, the oil, heavy hydrocarbons, water, and possibly solids contained in the crude oil sludge can be separated into (1) oil, (2) a mixture of water and heavy hydrocarbons, and (3) solid heavy hydrocarbons (possibly together with solid matter consisting of a mixture of solid matter and heavy hydrocarbons), and each of these can be recovered.

[0102] In the method for recovering oil from crude oil sludge according to the present invention, the physical properties of the recovered oil are not particularly limited, but the density (25°C) is preferably 800 to 950 kg / m ３ , more preferably 800 to 880 kg / m ３ The melting point is preferably 40 to 150°C, more preferably 40 to 110°C, and even more preferably 40 to 90°C, the freezing point is preferably 30 to 140°C, more preferably 30 to 100°C, and even more preferably 30 to 80°C, and the oil content is preferably 60% by mass or more.

[0103] The oil in the recovered crude oil sludge content, i.e., the recovered oil, has properties that allow it to be used as crude oil. Furthermore, in the method for recovering oil from crude oil sludge of the present invention, continuous centrifugation is possible using a decanter centrifuge, so that oil useful as crude oil from the crude oil sludge can be recovered with excellent recovery efficiency.

[0104] Furthermore, since heavy hydrocarbons in crude oil sludge are components that reduce the quality of crude oil, the method for recovering oil from crude oil sludge according to the present invention makes it possible to selectively remove or reduce the components that reduce the quality of crude oil while recovering oil that is effective as crude oil from crude oil sludge.

[0105] Furthermore, the water separated from the crude oil sludge by the method for recovering oil from crude oil sludge of the present invention can be appropriately treated by a wastewater treatment method. In addition, the heavy hydrocarbons and solids, which are unnecessary components in the crude oil sludge, can be recovered together in a solid form. Therefore, the method for recovering oil from crude oil sludge of the present invention makes it easy to dispose of the crude oil sludge.

[0106] Furthermore, since the oil content effective as crude oil and the water content treatable by wastewater treatment methods can be separated from the crude oil sludge, the heavy hydrocarbons and solids can be disposed of as industrial waste. Therefore, the method for recovering oil from crude oil sludge of the present invention can reduce the amount of industrial waste.

[0107] As described above, the present invention can provide a method for recovering oil from crude oil sludge, which allows for simple and continuous separation of the oil from crude oil sludge.

[0108] Next, the method for producing recycled crude oil according to the present invention will be described. The method for producing recycled crude oil according to the present invention is characterized in that the oil content in the crude oil sludge obtained by the recovery method according to the present invention is mixed with crude oil.

[0109] In a specific embodiment of the method for producing recycled crude oil according to the present invention, the oil in the crude oil sludge recovered by the recovery method according to the present invention can be mixed with the crude oil, for example, by mixing the recovered oil with the crude oil in a crude oil transfer pipe. The crude oil transfer pipe is a transfer pipe for transporting crude oil, and the crude oil flows through it, so mixing the recovered oil with the crude oil in the crude oil transfer pipe means mixing the recovered oil with the crude oil flowing through the crude oil transfer pipe.

[0110] The crude oil with which the recovered oil fraction is mixed is not particularly limited, and may be crude oil after crude oil extraction before solids, water, etc. are removed and the crude oil is stored in a crude oil tank; crude oil that has been recently stored in a crude oil tank after crude oil extraction after solids, water, etc. are removed and before crude oil sludge is generated; or crude oil that is the supernatant in a crude oil tank after crude oil sludge has been generated at the bottom of the crude oil tank by storing it in the crude oil tank for a certain period of time. The crude oil with which the recovered oil fraction is mixed may be the same type of crude oil as the crude oil that is the source of the crude oil sludge, or a different type of crude oil. When the crude oil sludge-containing material is a mixture of crude oil sludge and crude oil, the crude oil with which the recovered oil fraction is mixed may be the same type of crude oil as the crude oil that constitutes the crude oil sludge-containing material, or a different type of crude oil.

[0111] Methods for introducing recovered oil into crude oil in a crude oil transfer pipe include line mixing, mixing using a static mixer, an injection nozzle, a mixing valve, etc., but it is preferable to use line mixing because it is easier to prevent sludge caused by the recovered oil from being generated in the crude oil after the recovered oil is introduced and mixed.

[0112] According to the present invention, the oil component in crude oil sludge can be separated simply and continuously, and recycled crude oil can be produced simply and easily.

[0113] The present invention will be explained in more detail below by showing examples, but the present invention is not limited thereto.

[0114] The following crude oil sludge and crude oil were used: <Crude oil sludge> Crude oil sludge a recovered from a crude oil tank <Crude oil> Crude oil b having the following analytical values: API 35.4°, water mud content 0 vol %

[0115] (Example 1) 1. Recovery of oil from crude oil sludge A crude oil sludge-containing material, which was a mixture of crude oil sludge a and crude oil b such that the ratio of crude oil sludge a to the total was 95% by mass, was introduced into a storage tank adjusted to 80°C and stored therein. At the same time, the crude oil sludge-containing material stored in the storage tank was sent out to an external circulation line provided outside the storage tank using a liquid feed pump, and while circulating at 40 kL / h so as to return to the storage tank, a portion of the crude oil sludge-containing material circulating in the external circulation line was extracted from an extraction line installed midway along the circulation line so as to obtain an extraction rate of 20 kL / h, and supplied to the decanter centrifuge 1 shown in Figure 1. Next, the crude oil sludge-containing material supplied to the decanter centrifuge 1 was subjected to a temperature control at 80°C, 3500 G, a crude oil sludge-containing feed rate of 20 kL / h, and a pressure of "(the distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ When the centrifugation process was carried out while controlling the ratio (calculated by formula (II)) expressed as "(m)" to 0.180, it was possible to continuously separate and recover the recovered oil, the mixture of water and heavy hydrocarbons, and the mixture of heavy hydrocarbons and solids (mixture of heavy hydrocarbons and sand). During the centrifugation process, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was ｉ '(m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ａ (m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ (m), the flow rate Q of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge Ａ , the flow rate Q of recovered oil discharged from the light fraction discharge port of the decanter type centrifuge Ｂ (m ３ / s), number of heavy component outlets N Ａ , the number of light component outlets N Ｂ The discharge coefficient C is as shown in Table 1. The distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface isｉ The thickness h of the liquid layer discharged from the heavy component discharge port required for calculating '(m) Ａ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ａ Between (m) and h Ａ / r Ａ ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated using the calculation method 2. ｉ The thickness h of the discharged liquid layer discharged from the light component discharge port required when calculating '(m) Ｂ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ｂ Between (m) and h Ｂ / r Ｂ Since the relationship was ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly to "Calculation method 2" (the above-mentioned "Thickness h of the discharged liquid layer at the light fraction discharge port"), Ｂ In the above centrifugation treatment, the amount of recovered oil was 60 mass%, the amount of a mixture of water and heavy hydrocarbons was 40 mass%, and the amount of a mixture of heavy hydrocarbons and solid matter was 2 mass% relative to the total amount of recovered matter. The density (80°C) of water, which is obtained by subtracting heavy hydrocarbons from water and heavy hydrocarbons, was 1.031 g / cm ３ The content of metal chloride contained in the water (measured according to JIS K 2601) was 4.5 mass %.

[0116] 2. Production of Reclaimed Crude Oil The recovered oil fraction obtained was then diluted 6 times with crude oil b and mixed with crude oil b so that the recovered oil ratio was 2% by mass, yielding a blended crude oil. The blended crude oil and crude oil b were each centrifuged at 600 G for 12 minutes, yielding a crude oil sludge yield of 1.0% by volume in both cases. These results demonstrate that the recovered oil fraction obtained can be effectively used as reclaimed crude oil by blending it with crude oil.

[0117] (Examples 2 to 5) By changing the amount of crude oil sludge-containing material fed to the centrifuge, the amount of the material fed to the centrifuge was increased by 1 / r (the distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate). ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ The ratio (calculated by formula (II)) expressed by "(m)" was changed so that the values ​​shown in Table 1 were obtained. The distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated. ｉ '(m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ａ (m) The distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ (m), the flow rate Q of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge Ａ , the flow rate Q of recovered oil discharged from the light fraction discharge port of the decanter type centrifuge Ｂ (m ３ / s), number of heavy component outlets N Ａ , the number of light component outlets N Ｂ The centrifugal separation process was carried out in the same manner as in "1. Recovery of oil from crude oil sludge" in Example 1, except that the flow coefficient C and the flow rate coefficient C were changed as shown in Table 1. The recovered oil, the mixture of water and heavy hydrocarbons, and the solid matter were each continuously separated and recovered. In the centrifugal separation process, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was ｉ The thickness h of the liquid layer discharged from the heavy component discharge port required for calculating '(m) Ａ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ａ Between (m) and h Ａ / r Ａ ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated using the calculation method 2. ｉThe thickness h of the discharged liquid layer discharged from the light component discharge port required when calculating '(m) Ｂ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ｂ Between (m) and h Ｂ / r Ｂ Since the relationship was ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly to "Calculation method 2" (the above-mentioned "Thickness h of the discharged liquid layer at the light fraction discharge port"), Ｂ The calculation was carried out using "Calculation Method 2" below.

[0118] (Comparative Example 1 to Comparative Example 4) By changing the amount of crude oil sludge-containing material fed to the centrifuge, the amount of the material fed to the centrifuge was increased by 1 / r (the distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate). ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ The ratio (calculated by formula (II)) expressed by "(m)" was changed so that the values ​​shown in Table 1 were obtained. The distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated. ｉ '(m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ａ (m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ (m), the flow rate Q of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge Ａ , the flow rate Q of recovered oil discharged from the light fraction discharge port of the decanter type centrifuge Ｂ (m ３ / s), number of heavy component outlets N Ａ , the number of light component outlets N Ｂ The centrifugal separation process was carried out in the same manner as in "1. Recovery of oil from crude oil sludge" in Example 1, except that the flow coefficient C and the discharge coefficient C were changed as shown in Table 1. In the centrifugal separation process, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was ｉ The thickness h of the liquid layer discharged from the heavy component discharge port required for calculating '(m) Ａ(m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ａ Between (m) and h Ａ / r Ａ ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated using the calculation method 2. ｉ The thickness h of the discharged liquid layer discharged from the light component discharge port required when calculating '(m) Ｂ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ｂ Between (m) and h Ｂ / r Ｂ Since the relationship was ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly to "Calculation method 2" (the above-mentioned "Thickness h of the discharged liquid layer at the light fraction discharge port"), Ｂ As a result, in all of Comparative Examples 1 to 4, the discharged liquid (recovered oil) did not flow out from the light component discharge port, and a mixture of recovered oil, water, and heavy hydrocarbons was discharged from the heavy component discharge port, and in all cases, the oil to be recovered could not be continuously separated from the other components.

[0119] (Comparative Examples 5 to 8) By changing the amount of crude oil sludge-containing material fed to the centrifuge, the amount of the material fed to the centrifuge was increased by 1 / r (the distance from the center of the rotation axis of the decanter centrifuge to the end of the baffle plate on the water layer side). ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ The ratio (calculated by formula (II)) expressed by "(m)" was changed so that the values ​​shown in Table 1 were obtained. The distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated. ｉ '(m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ａ (m), the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ｂ(m), the flow rate Q of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge Ａ , the flow rate Q of recovered oil discharged from the light fraction discharge port of the decanter type centrifuge Ｂ (m ３ / s), number of heavy component outlets N Ａ , the number of light component outlets N Ｂ The centrifugal separation process was carried out in the same manner as in "1. Recovery of oil from crude oil sludge" in Example 1, except that the flow coefficient C and the discharge coefficient C were changed as shown in Table 1. In the centrifugal separation process, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was ｉ The thickness h of the liquid layer discharged from the heavy component discharge port required for calculating '(m) Ａ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ａ Between (m) and h Ａ / r Ａ ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly, the distance r from the center of the rotation axis of the decanter centrifuge to the estimated oil-water interface was calculated using the calculation method 2. ｉ The thickness h of the discharged liquid layer discharged from the light component discharge port required when calculating '(m) Ｂ (m) is the distance r between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port. Ｂ Between (m) and h Ｂ / r Ｂ Since the relationship was ≦0.05, the thickness of the discharged liquid layer at the heavy component discharge port h Ａ Similarly to "Calculation method 2" (the above-mentioned "Thickness h of the discharged liquid layer at the light fraction discharge port"), Ｂ The oil content was calculated using "Calculation Method 2 for the solid content of the oil." As a result, the solid viscous heavy hydrocarbons adhered to the screw plate, making it difficult to convey them in the direction of the solids outlet, and the solid viscous heavy hydrocarbons clogged the solids outlet, making it impossible to continuously separate the oil to be recovered from the other components. The results of the above-mentioned Examples and Comparative Examples are shown in Table 2.

[0120]

[0121]

[0122] As can be seen from Tables 1 and 2, in Examples 1 to 5, a crude oil sludge-containing material is supplied to a decanter centrifuge at 80°C and centrifuged, thereby separating the crude oil sludge into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and an aqueous layer in the separation zone of the decanter centrifuge. While supplying the crude oil sludge-containing material to the separation zone, the following steps are carried out: (i) the first layer is discharged to the outside of the separation zone from a light fraction discharge port of a light fraction discharge path provided on the light side at one end of the separation zone to recover the recovered oil; and (ii) at least a portion of the aqueous layer and the second layer is discharged from the heavy side at one end of the separation zone over a baffle that defines one end of the separation zone into a heavy fraction discharge path, and then retained inside a weir that is connected to the separation zone and provided in the heavy fraction discharge path adjacent to the baffle. (iii) at least a portion of the water layer and the second layer is discharged from a heavy component discharge port provided in the heavy component discharge path to recover water and heavy hydrocarbons, and (iv) at the other end side of the separation zone, the remaining portion of the heavy hydrocarbons is discharged to the outside of the separation zone to recover the heavy hydrocarbons, ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ It can be seen that by controlling the value of (m) to be within a predetermined range, the oil content in the crude oil sludge can be separated easily and continuously.

[0123] On the other hand, from Tables 1 and 2, in Comparative Examples 1 to 8, the distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate during centrifugation - r ｉ ') (m) / (distance from the center of the rotation axis of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ) (m)" is outside the specified range, the discharged liquid (recovered oil) does not flow out from the light component discharge port (Comparative Examples 1 to 4), the solid viscous heavy hydrocarbons adhere to the screw plate, making it difficult to transport them in the direction of the solid component discharge port, or the solid viscous heavy hydrocarbons clog the solid component discharge port (Comparative Examples 5 to 8), and it is therefore not possible to continuously separate the oil to be recovered from the other components.

[0124] According to the present invention, it is possible to provide a method for recovering oil from crude oil sludge, which allows for simple and continuous separation of the oil from crude oil sludge, and a method for producing recycled crude oil.

[0125] REFERENCE SIGNS LIST 1 Decanter-type centrifuge 2 Inner cylinder 3 Outer cylinder 4 Material to be treated (material containing crude oil sludge) supply port 5 Solids discharge port of outer cylinder 6 Separation area 7 Screw plate 10 Partition wall 11 Baffle plate 13 Gear box 16 Solids discharge space 17 Solids discharge port of housing 18, 19, 21, 22 Bearing 20 Housing 23 Rotating shaft for inner cylinder 24 Rotating shaft for outer cylinder 25 Outer cylinder fixing member 26 Inner cylinder fixing member 27 Material to be treated supply pipe 28 Solids 29 Material containing crude oil sludge (material to be treated, heated and stirred) 30 Centrifugal separation tube 31 Recovered oil 32 Heavy hydrocarbons 33 Water 34 First layer 35 Second layer 36 Water layer 37 Heavy component discharge path 38 Light component discharge path 39 Other end side of second layer 40 Solid matter (mixture of heavy hydrocarbons and solid matter) 141 Discharge space for heavy components 142 Discharge space for light components 151 Heavy component discharge port of casing 152 Light component discharge port of casing 371 Heavy component discharge port 372 Connecting passage 373 Weir 374 Heavy component discharge port 381 Light component discharge port 382 Connecting passage 384 Light component discharge port

Claims

1. A method for recovering oil from crude oil sludge, which is separated into a first layer consisting of recovered oil, a second layer consisting of heavy hydrocarbons, and a water layer in the separation region of a decanter-type centrifuge having an inner cylinder formed with a material feed port for discharging the material containing crude oil sludge from the inside to the outside and supplying it to a separation region, and an outer cylinder provided coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and having a solids discharge port for discharging heavy hydrocarbons from the inside to the outside, and for forming a separation region between the inner cylinder and the outer cylinder, the method comprising: supplying the material containing crude oil sludge at 40 to 200°C and centrifuging the material, the method comprising the steps of: (i) discharging the first layer to the outside of the separation region from a light fraction discharge port of a light fraction discharge path provided on the light side at one end of the separation region, and recovering the recovered oil; (ii) discharging at least a portion of the aqueous layer and the second layer from the heavy side at one end of the separation region into a heavy component discharge path over a baffle plate that defines one end of the separation region, and then retaining them inside a weir that is connected to the separation region and adjacent to the baffle plate and that is provided in the heavy component discharge path, and then discharging at least a portion of the aqueous layer and the second layer from a heavy component discharge port provided in the heavy component discharge path to recover water and heavy hydrocarbons, and (iii) discharging the remainder of the heavy hydrocarbons to the outside of the separation region through the solid component discharge port provided on the other end of the separation region to recover the heavy hydrocarbons, and (where r ｉ ': Distance (m) from the center of the rotation shaft of the decanter centrifuge to the estimated oil-water interface Ａ　 r: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the heavy fraction discharge port Ｂ　 ρ: the distance (m) between the center of the rotation axis of the decanter centrifuge and the bottom surface of the discharged liquid layer discharged from the light fraction discharge port Ａ : density of the moisture (kg / m ３ ) ρ Ｂ : density of the recovered oil (kg / m ３ ) and h Ａ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the heavy fraction discharge port, calculated by Ａ : the flow rate (m) of water and heavy hydrocarbons discharged from the heavy fraction discharge port of the decanter centrifuge ３ / s), v Ａ : Outflow velocity of the discharged liquid at the heavy fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance of the discharged liquid at the heavy fraction discharge port from the center of the rotation axis of the decanter centrifuge, N Ａ : the number of the heavy fraction discharge ports, C: outflow coefficient, S Ａ : Vertical cross-sectional area (m ２ ) h Ｂ :The following formula and the following formula: The thickness (m) of the discharged liquid layer discharged from the light fraction discharge port, calculated by Ｂ : The flow rate (m) of recovered oil discharged from the light fraction discharge port of the decanter type centrifuge ３ / s), v Ｂ : Outflow velocity of the discharge liquid at the light fraction discharge port (m / s), ω: Angular velocity of the outer cylinder of the decanter centrifuge (rad / s), r: Distance of the discharge liquid at the light fraction discharge port from the center of the rotation axis of the decanter centrifuge, N Ｂ : the number of the light fraction discharge ports, C: outflow coefficient, S Ｂ : Vertical cross-sectional area (m ２ (the distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r ｉ ') (m) / (distance from the center of the rotation shaft of the decanter centrifuge to the water layer side end of the baffle plate - r Ｂ ) (m) (II) is controlled to be in the range of 0.170 to 0.450, and the centrifugation treatment is performed while controlling the ratio represented by the following formula:

2. A method for recovering oil in crude oil sludge as set forth in claim 1, comprising: supplying the crude oil sludge-containing material to a decanter-type centrifuge having: an inner cylinder formed with a material supply port for discharging the material from the inside to the outside and supplying it to a separation area; an outer cylinder arranged coaxially with the inner cylinder so as to surround the inner cylinder on the outside of the inner cylinder and having a solids discharge port for discharging the heavy hydrocarbons from the inside to the outside, and forming a separation area between the inner cylinder and an outer cylinder; a screw plate wound helically on the outer wall of the inner cylinder; and an outer cylinder fixing member arranged on one end of the separation area, and having a light component discharge path for discharging recovered oil closer to the inner cylinder and a heavy component discharge path for discharging water and heavy hydrocarbons closer to the outer cylinder.

3. A method for recovering oil from crude oil sludge as described in claim 1, wherein the aqueous layer formed in the decanter centrifuge contains metal chloride salts at a concentration of 3.0 to 5.0 mass %.

4. A method for recovering oil from crude oil sludge as set forth in claim 1, comprising storing the crude oil sludge-containing material to be centrifuged at a temperature of 40 to 200°C in a storage tank having a heating means, sending it out through an external circulation line provided outside said storage tank and circulating it back to said storage tank, and extracting a portion of the crude oil sludge-containing material circulating in said external circulation line from an extraction line provided midway along the circulation line at a speed of 20 to 60% of the circulation speed of the crude oil sludge-containing material, and supplying it to said decanter-type centrifuge.

5. A method for producing recycled crude oil, comprising mixing the oil in the crude oil sludge obtained by the recovery method according to any one of claims 1 to 4 with crude oil.

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