JPS6145680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention primarily relates to a method and apparatus for desalinating fuel oil for gas turbines.

Gas turbines are widely used for power generation and other purposes because they can generate a large amount of power with a small device. The function of a gas turbine is to generate power by blowing high-temperature gas generated from the combustion of fuel oil onto turbine blades, but impurities in the fuel oil cause high-temperature corrosion of gas turbine materials. .
The impurity that is the main factor causing this high temperature corrosion is
These are Na and K compounds, and to prevent high-temperature corrosion, Na and K compounds remaining in fuel oil must be
It is necessary to reduce the amount to about 1 ppm or less in terms of K. In the present invention, the fuel oil to be cleaned is Na, K
It is an oil that contains about 1 ppm or more of a compound, such as crude oil, residual oil, and refined oil that contain these oils.

Most of the Na, K compounds are NaC, KC
It is in the form of a salt, dissolved in a small amount of water present in fuel oil, and also contained in fuel oil as a minute solid. Removal of Na, K compounds is Na, K
Since it is the removal of salt, it is generally called desalination.

Next, conventional desalination technology will be explained. Na, K salts dissolve well in water. Therefore, when fuel oil and water are mixed, stirred and washed and the water is separated, the Na and K salts can move into the water and be desalted. However, when water is added to fuel oil and mixed and stirred, an emulsion is formed, as is generally known, and it is difficult to separate water and fuel oil by normal means. For this reason,
Conventionally, when washing fuel oil with water, a chemical for preventing or destroying emulsions (hereinafter referred to as an emulsion breaker) was added to the fuel oil, and then electrostatic electricity or centrifugal force was used to separate the water and fuel. Separated from oil and desalted.

This conventional desalting method and apparatus will be explained in more detail with reference to FIG. In the figure, 1a is a first stage centrifugal separator, 1b is a second stage centrifuge, 2 is a fuel oil tank, 3 is an emulsion breaker tank, and 4 is a fuel oil tank.
5a and 5b are pumps that supply the fuel oil 10 or emulsion breaker 15 from the tanks 2 and 3, respectively; 7 is a filter; 12
is clean water, 13 is wastewater, 14 is sludge, and 16 is wash water. The centrifugal separators 1a and 1b are for liquid processing, and are capable of separating substances having different specific gravities, ie, fuel oil, water, sand, and organic solids, by centrifugal force.

The raw material fuel oil 10 is supplied to the pump 5 from the fuel oil tank 2.
The emulsion breaker 15 extracted from the tank 3 by the pump 5b and the second emulsion breaker
Washing water 16 which is water separated by the stage centrifuge 1b
is added. The fuel oil to which these have been added is sufficiently stirred and washed in the mixer 4a, and then enters the first stage centrifugal separator 1a. Here, due to the action of strong centrifugal force and the action of the emulsion breaker 15, the fuel oil, water, and solid matter consisting of fine particles contained in the fuel oil are separated, and the water becomes wastewater 13 and the solid matter becomes sludge 14. It is discharged outside the machine as a waste and undergoes the following processing. On the other hand, the fuel oil discharged from the first stage centrifugal separator 1a is further mixed with an emulsion breaker 15 and clean water 12, and is stirred and washed again in the mixer 4b. Next, fuel oil, water and solids are separated in the second stage centrifugal separator 1b, the water is refluxed as wash water 16 as described above, and the solids are sent to the sludge 14.
The fuel oil is extracted as cleaning oil 11a, and after being subjected to a dust removal action by the filter 7, it is supplied to the gas turbine (11b). It should be noted that since the clean water 12 may remain in the fuel oil, it is desirable that the content of Na and K is low, so generally the content of these impurities is 10 to 10%.
Water with a concentration of about 100 ppm is used. Further, the filter 7 is for removing particulates from fuel oil in order to protect the gas turbine, and may not be installed in some cases.

As described above, conventionally, fuel oil is desalinated by repeating a combination of washing the fuel oil with water and separating it using centrifugal force. and,
Since it is necessary to treat fuel oil at a rate of several tens of m ³ /hr or more, the desalination operation is a continuous operation. However, in continuous operation, it is unavoidable that water is entrained in the fuel oil during the separation process, and this water contains Na. Since the salt is dissolved, desalting cannot proceed sufficiently with only one stage of washing and separation, so in many cases, the combination of washing and separation is a two-stage system.

As described above, in conventional desalting, the washing and separation steps must be performed in two or more stages, but the centrifuges 1a and 1b are high-speed rotating machines and expensive. Since two or more of these devices are required, there is a drawback that the device price inevitably becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus that can eliminate the drawbacks of the prior art described above and desalinate fuel oil at low cost and efficiently.

The feature of the desalination method of the present invention for achieving this purpose is that after the solid matter in the fuel oil is removed as sludge using a centrifuge, the fuel oil is put into an oil-water separator to remove moisture. The purpose is to remove
Since oil-water separators are cheaper than centrifuges, desalination can be performed with inexpensive equipment overall.

In addition, the features of the desalination equipment according to the present invention include a centrifugal separator that removes solids from fuel oil, and an oil water made of fibers that removes moisture from the fuel oil flowing out from the centrifugal separator. a separator, and the centrifugal separator is provided with a fuel oil introduction hole, a sludge outlet hole, and a fuel oil outlet hole after sludge removal on a rotating shaft, and communicates with each of the holes around the rotating shaft. The present invention is comprised of a centrifugal extractor having an annular rotor with a space defined by a partition wall, and a means for adjusting the amount of sludge flowing out.

As mentioned above, one of the features of the present invention is the use of an oil-water separator, and the reason why this can be used will be explained below.
Water in oil generally causes corrosion of materials in various machines and equipment. For example, aircraft fuel oil is sufficiently refined by distillation, etc., but water is removed using an oil-water separator to prevent corrosion caused by water. This oil-water separator is a device made of synthetic fibers, natural fibers, glass fibers, etc. in the form of cloth or rope, which are arranged in one or multiple layers.When oil is passed through this oil-water separator, water droplets in the oil are removed. It aggregates into large-diameter water droplets, and separates water and oil based on the difference in specific gravity in a gravitational field. The oil/water separator according to the present invention is intended for a device having such a configuration. By the way, in order for such an oil-water separator to fully exhibit its separation function, the openings (hereinafter referred to as openings) between the fibers through which the liquid passes are as small as several μm to several tens of μm. On the other hand, the fuel oil to be treated in the present invention contains a large number of solids with a size of several μm to several tens of μm, and these solids cause clogging.
Becomes unable to drive. Since it is difficult to regenerate an oil-water separator without removing the fine particles that adhere to the minute openings, it has been thought that it is impossible to treat water separation in fuel oil with an oil-water separator. It was getting worse.

The present inventors investigated the properties of solid matter in fuel oil, and conducted various experiments and studies on methods for removing solid matter. Fuel oil contains water, inorganic particulates such as sand, and organic particulates such as wax and asphaltene, which have a higher specific gravity than fuel oil, so they can be separated by applying centrifugal force. A highly viscous substance called sludge is formed from these fine particles and water droplets. When the amount of water in the sludge is large, the viscosity of the sludge decreases and fluidity improves.

Furthermore, according to experimental results, it has been found that when an emulsion breaker is added to fuel oil as in the past, fine particles such as sand are entrained in the fuel oil. This is because water in fuel oil is in the form of particles, but fine particles such as sand are attached to these water particles, and when an emulsion breaker is added, the water particles coalesce to form a water layer. This is to release particles such as sand that adhere to the fuel oil.

The present invention skillfully utilizes the properties of a fluid composed of fuel oil, water, and fine particles as described above. That is, the present invention does not add an emulsion breaker to the fuel oil introduced into the centrifugal separator, and wash water is added or not added depending on the amount of water in the fuel oil, and the centrifugal separator In this method, effective removal of fine particles is made possible by creating a sludge in which fine particles are sufficiently mixed in water, and water is removed by an oil-water separator after the fine particles are removed. Since water is removed from the mixed fluid of fuel oil and water from which most of the particulate matter has been removed, clogging of the oil-water separator is reduced, making it practical.

The details of the present invention will be explained below with reference to the drawings. Second
The figure shows an embodiment of the present invention, in which 1 is a centrifuge, 5 is a pump for introducing fuel oil 10 into the centrifuge, and 4 is for supplying clean water 12 to the fuel oil discharged from the centrifuge 1. Mixer for mixing after addition, 7 is a filter,
Reference numeral 6 denotes an oil-water separator that removes moisture in the fuel oil after passing through the filter and discharges it as waste water 13, and obtains purified fuel oil 11 to be supplied to the gas turbine. As the centrifugal separator 1, a conventional one as shown in FIG. 5, which will be described later, or a centrifugal separator configured according to the present invention as shown in FIGS. 6 and 7 can be used. Further, as the oil/water separator 6, a fabric made of the above-mentioned fibers knitted into a cloth or rope shape is used.
The opening of the filter 7 was 5 μm, which was smaller than the opening of the oil-water separator 6.

In FIG. 2, feedstock fuel oil 10 enters centrifuge 1 via pump 5. Here, solid matter in the fuel oil is removed as sludge 14. In this case, as mentioned above, since no emulsion breaker is added to the fuel oil, fine particles are not released into the fuel oil from the water layer and are effectively absorbed together with a part of the water, which has a larger mass than the fuel oil. removed. Next, clean water 12 is added to the fuel oil discharged from the centrifugal separator 1, agitated and washed in a mixer 4, and then passed through a filter 7 into an oil-water separator 6. The water used for cleaning is separated here and discharged as waste water 13, and the fuel oil becomes cleaning oil 11 and goes to the gas turbine. The fuel oil heading to the oil-water separator 6 has an extremely small amount of particles because the centrifuge 1 effectively removes the particles and the filter 7 with a small opening removes the particles.

The results of an experiment in which fuel oil was desalinated by such an operation will be explained in comparison with the conventional technique shown in FIG. Na30ppm in raw fuel oil 10,
As a result of experiments using the conventional method using crude oil with a water content of 5000 ppm and an emulsion breaker input amount of 50 ppm, the properties of cleaning oil 11 were found to be 0.9 ppm Na and 50 ppm water.
It became 2000ppm. On the other hand, in the example, the properties of the cleaning oil 11 are 0.5 ppm Na and 600 ppm water.
The cleaning effect was significantly improved compared to conventional methods. In addition, the pressure loss of filter 7 increased only within 0.1Kg/cm ² even after 70 hours of operation, which is a low value, and the allowable pressure loss for operation was set at 1Kg/cm ²
In this case, it was found that it would be possible to operate for more than 700 hours. Furthermore, the installation cost of the oil-water separator 6 is about 1/5 that of the conventionally used second stage centrifugal separator 1b, making it possible to provide an inexpensive desalination device.

Note that the filter 7 is not necessarily necessary since most particulates are removed by the centrifuge 1 as described above, but since the filter 7 is about 1/3 the price of the oil/water separator 6, the filter 7 is not necessary. Operation costs can be kept low by allowing operation to continue by replacing 7.

By the way, there are many types of crude oil, and some crude oil has a low Na concentration. In the case of oil with low Na concentration,
Since almost all impurities such as Na can be removed by the centrifuge 1, the treatment can be performed without adding clean water 12. Some of the water in the oil, which dissolves some impurities, is entrained in the fuel oil flow, but this water is removed in the oil-water separator 6, which allows the impurities to be removed and desalted. can. According to experiments, when the Na concentration in the raw fuel was 5 ppm, it was possible to reduce the Na concentration in the cleaning oil to 0.7 ppm. If the clean water 12 is not used in this way, water and its purifying device become unnecessary, and economy is achieved, which is particularly effective in places where water is scarce.

In the above embodiment, water was not added to the fuel oil introduced into the centrifugal separator 1, but if the raw material fuel oil contains little water, it becomes relatively difficult for the sludge to flow out from the centrifuge 1. In this case, as shown in the embodiment of FIG. 3, part or all of the water 13 separated by the oil-water separator 6 is added to the introduction side of the centrifugal separator 1 and mixed by the mixer 4c. By performing such an operation, a large number of emulsions are formed in the raw material fuel oil, and water droplets in the sludge created by centrifugal force improve the fluidity of the sludge, making it easier to drain the sludge.

As shown in Fig. 3, when washing water is added to raw fuel oil, a large number of water particles are created and an emulsion is formed, but the oil-water separator 6 unites the water particles and separates the water as large-diameter water particles. are doing. Therefore, in order to promote the coalescence of this water, an emulsion breaker 15 is added together with the clean water 12 between the centrifugal separator 1 and the filter 7, as in the embodiment shown in FIG. By such an emulsion breaker addition operation, the water separation action of the oil/water separator 6 is promoted, and the water content in the cleaning oil 11 can be reduced. In this example, washing water 16 is added before the centrifugal separator 1, but it goes without saying that depending on the oil, it is not necessary to add this, and the effect of adding an emulsion breaker is also exhibited in this case. It goes without saying that it can be done.

By the way, some organic solids contained in fuel oil melt at a temperature of 40 to 70°C and dissolve in the fuel oil. Therefore, depending on the fuel oil, if the operating temperature of the oil-water separator 6 is lower than the operating temperature of the centrifuge 1, dissolved substances may precipitate and organic solids may be generated, causing clogging. There is. In such a case, a heater is installed in front of the filter 7 shown in each of the embodiments described above, and the centrifugal separator 1 is operated with the temperature of the fuel oil higher than the operating temperature of the centrifugal separator 1. Due to this heating operation, the organic solids entrained in the fuel oil after the centrifuge 1 are dissolved, and other organic solids do not precipitate, thereby preventing clogging of the filter 7 and oil/water. Separator clogging can be prevented.

According to each of the above-mentioned embodiments, a reduction in equipment cost and an improvement in the desalination effect are achieved as described above.Next, the operating cost will be compared with the conventional method. According to the conventional system, the emulsion breaker is inserted at two locations in front of the first and second stage centrifugal separators 1a and 1b, but in the present invention, the emulsion breaker is inserted at one location or not at all as described above. In the conventional system, the amount of emulsion breaker added to the fuel oil is 50 ppm at each of two locations. Now, assuming a throughput of 100m ³ /hr, the input amount of the emulsion breaker is
10Kg/hr, and the unit cost is approximately 800 yen/
Since it is Kg, it will be 8K ￥/hr. According to experiments,
For those with filter 7, the filter does not need to be replaced for 700 hours. The emulsion breaker cost consumed by the conventional method during these 700 hours is 5,600K yen. On the other hand, the element cost for filter 7 is approximately 700K yen. Therefore, operating costs can be reduced to about one-eighth.

On the other hand, if the filter 7 is not installed, it is necessary to replace the element of the oil/water separator 6, but the cost of the element is approximately 2000K yen. Therefore, in this case, the operating cost can be reduced to about one-third compared to the conventional method, and in any case, the important effect of significantly reducing the operating cost can be achieved.

Note that the clean water 12 used in the above embodiment is entrained in the cleaning oil 11 at about 200 to 700 ppm, so if there is Na in this water, this Na will be absorbed into the cleaning oil 11.
clean water 12 has Na and K concentrations.
It is desirable to use water with a concentration of 1000 ppm or less.
Further, since the mixers 4 and 4c mix fuel oil and water, they do not necessarily have to have an agitator structure; for example, a pump or an orifice may be used for mixing.

Next, the centrifugal separator used in the present invention will be explained. Conventionally, a centrifugal separator as shown in FIG. 5 has been used to desalinate fuel oil. In the figure,
20 is a centrifugal separator, 21 is a shaft, 22 is a non-rotating raw material oil introduction pipe attached to a stationary part, 23
2 is a treated oil outlet pipe, 24 is a water outlet pipe, 25 is a blade, 2
Reference numeral 6 denotes a sludge outlet hole opened in the outermost periphery of the rotating body 27, and in the figure, all parts other than the raw oil inlet pipe 22 rotate together with the shaft 21.

The oil introduced from the feedstock oil introduction pipe 22 is guided to the lower outer circumferential side of the centrifuge 20 and enters between the blades 25, where it is rotated by being given rotational force by the walls and blades 25 of the centrifuge 20. . The wings 25 are triangular pyramid-shaped plates, and the spacing between the plates is small, and the oil that enters between these plates is subject to centrifugal force due to the rotation of the oil itself. , the sludge moves to the outer periphery to separate water and sludge from the oil. The oil from which the water and sludge have been separated is ejected out of the machine through the treated oil outlet pipe 23 by centrifugal force. There is a cover (not shown) outside the machine that does not rotate and is separate from the machine, and this covers the spilled oil to collect it. On the other hand, water and sludge are transferred to centrifuge 2.
0 and the water with low viscosity is transferred to the water outlet pipe 2.
4 and is ejected to a water receiving cover (not shown) outside the machine and collected. Sludge has a high viscosity and cannot pass through the water outlet pipe 24, so the sludge outlet hole 2
6 and is collected by a sludge cover (not shown). The sludge outlet hole 26 is a small hole,
The sludge passes through this small hole using the high hydraulic pressure inside the machine. Since it is constructed and operates as described above, water and sludge can be separated from oil.

However, the centrifugal separator used in the present invention may be one that can separate sludge in a liquid using centrifugal force.

Figure 6 shows an example of a centrifugal separator suitable for carrying out the present invention, which is similar to what is called a centrifugal extractor and uses a mechanical seal as shown in Figure 7. Therefore, we will call it a mechanical separator. In this mechanical separator 31, a rotating shaft 33 is supported by a frame 43 via a bearing 42, and a rotational force is applied to this rotating shaft via a pulley 41 to rotate the rotating shaft. 32 is a disk-shaped rotor that forms an annular space around the rotating shaft 33; 35 is a raw oil introduction hole bored in the axial direction of the rotating shaft 35; 36 is a treated oil outlet hole; 37
34 is a sludge outlet hole, and 34 is an oil introduction pipe provided radially in the center of the rotor 32 and has oil outlets 34a on both sides of the tip, and the oil introduction pipe communicates with the feedstock oil introduction hole 35. . 38a and 38b are the oil introduction pipe 34 and the side wall surface 32a of the rotor 32,
32b, there is a partition wall whose inner end is integrated with the rotating shaft 33, and the radius of the partition wall is the same as that of the oil outlet 3.
A space 50 that is larger than the radius of the oil introduction pipe up to 4a and serves as an oil outlet flow path communicating with the treated oil outlet hole 36 between the oil introduction pipe 34 and the partition walls 38a and 38b.
Furthermore, a space 51 serving as a sludge discharge passage communicating with the sludge discharge hole 37 is formed between the partition walls 38a, 38b and the rotor side wall surfaces 32a, 32b facing them. 52,53,5
Reference numeral 4 denotes a raw material oil inlet pipe, a treated oil outlet pipe, and a sludge outlet pipe, which are connected to the raw material oil inlet hole 35, treated oil outlet hole 36, and sludge outlet hole 37 through mechanical seals 40, respectively. 53
And the sludge outlet pipe 54 is provided with a back pressure valve 45 and a sludge valve 46 whose opening degree can be adjusted, respectively.
In addition, a pressure gauge 47 is attached to each pipe.

The mechanical seal 40 in FIG. 7 is shown on the left side of the drawing in FIG. 6, and 55 is the frame 43.
a cover fixed to and covering an end of the rotating shaft 33;
6 is a sludge outlet opened in the cover, 57 is a carbon ring whose tip is pressed against the end surface of the rotating shaft by a spring 59, and 58 is the carbon ring 5.
This is a sealing O-ring interposed between the outer circumference of the cover 7 and the inner circumference of the cylindrical portion of the cover 55.

In the configurations shown in FIGS. 6 and 7, the feedstock fuel oil passes through the mechanical seal 40 and enters the feedstock oil introduction hole 35.
The oil then passes through the oil introduction pipe 34 and enters the rotor 32. Inside the rotor 32, due to the strong centrifugal force,
Oil with low specific gravity flows through the flow path 50 toward the inner circumferential side of the rotor 32.
The processed oil outlet hole 3 provided on the rotating shaft moves through the
6, mechanical seal 40, treated oil outlet pipe 53,
It exits to the outside through the back pressure valve 45. On the other hand, water and sludge move inside the rotor 32 toward the outer circumference, pass through the flow path 51, and then exit through the sludge outlet hole 37, the mechanical seal 40, the sludge outlet pipe 54, and the sludge valve 46. Sludge and water can be separated from fuel oil by the operations described above.

In this mechanical separator, liquid can be made to go in and out of the rotating body through the mechanical seal 40, and the liquids that go in and out do not mix with each other, and each flow path can be understood as one conduit. That is, it is also possible to make these liquids under negative pressure or pressurize them. For example, when the back pressure valve 45 is closed, the input pressure of the raw material fuel oil 10 becomes the pressure at the sludge outlet, and the sludge is washed away with strong pressure. Conversely, when the sludge valve 46 is closed and the back pressure valve 45 is opened, oil flows out from the back pressure valve 45. Therefore,
By setting the back pressure valve 45 and the sludge valve 46 to appropriate opening degrees, an appropriate amount of sludge can be extracted while the rotor 32 is rotating. This withdrawal amount can be controlled by monitoring the pressure 47 and adjusting the back pressure valve 45 and sludge valve 46. Furthermore, it is also possible to control the extraction amount by adjusting the valves 45 and 46 by installing a flow meter instead of the pressure gauge and monitoring the flow rate.

Since this mechanical separator has the above-mentioned flow rate adjusting means, it has the feature that the amount of sludge extracted can be controlled depending on the properties of the raw oil, the processing mode, etc. The structure of the mechanical seal 40 is not limited to the structure shown in FIG. 7; for example, a triple-layer structure in which a mechanical seal is provided only at one end of the shaft 33 is also possible.

As described above, the method for desalinating fuel oil according to the present invention is characterized by separating fine particles in fuel oil using a centrifugal separator and then separating water using an oil-water separator. Compared to the method of desalting using two centrifuges, desalination can be carried out more efficiently.

Furthermore, the desalination apparatus according to the present invention is equipped with a centrifugal separator and an oil-water separator, and the oil-water separator only includes a fiber oil-water separation element, and does not require power at the same time. , it is possible to significantly reduce not only the equipment cost but also the amount of operation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an apparatus for desalting gas turbine fuel oil, Fig. 2 is a block diagram showing an example of an apparatus carrying out the desalination method according to the present invention, and Fig. 3 is a block diagram showing another embodiment of the present invention. A configuration diagram showing an example, FIG. 4 is a configuration diagram showing another embodiment of the present invention different from each of the above embodiments,
FIG. 5 is a sectional view showing an example of a centrifugal separator that can be used in the present invention, FIG. 6 is a sectional view showing an example of a centrifugal separator according to the present invention, and FIG.
FIG. 3 is a sectional view showing a mechanical seal portion of the centrifugal separator shown in the figure. 1, 1a, 1b, 20...centrifuge, 4, 4a
~4c...mixer, 5...pump, 6...oil/water separator,
7... Filter, 10... Raw material fuel oil, 11... Cleaning oil, 12... Clean water, 13... Waste water, 14... Sludge, 15... Emulsion breaker, 31... Centrifugal extractor, 32... Rotor, 33... Shaft, 34... Oil introduction pipe, 35... Raw oil introduction hole, 36... Processed oil outlet hole, 37... Sludge outlet hole, 38a, 38b... Partition wall, 40... Mechanical seal, 45... Back pressure valve, 4
6... Sludge valve, 47... Pressure gauge.

Claims (1)

[Claims] 1. Fuel oil is charged into a centrifuge to separate fine particles in the fuel oil as sludge, and then water in the fuel oil is separated by an oil-water separator using fibers as oil-water separation elements. A method for desalinating fuel oil characterized by: 2. A method for desalinating fuel oil according to claim 1, characterized in that water is added to the fuel oil and then the fuel oil is charged into the centrifugal separator. 3 In claim 1 or 2,
A method for desalinating fuel oil, characterized by adding clean water to the fuel oil after removing particulates using the centrifugal separator. 4. The method for desalinating fuel oil according to claim 2, characterized in that part or all of the water separated by an oil-water separator is used as the water added to the fuel oil. 5 In claim 1 or 2,
A method for desalinating fuel oil, characterized in that fine particles remaining in the fuel oil discharged from the centrifugal separator are separated by a filter, and then the fuel oil is introduced into the oil-water separator. 6 In claim 1 or 2,
A method for desalinating fuel oil, characterized by making the temperature of the fuel oil in the oil-water separator higher than the temperature of the fuel oil in the centrifugal separator. 7. The method for desalinating fuel oil according to claim 3, characterized in that an emulsion breaker is further added to the fuel oil discharged from the centrifugal separator. 8. A centrifugal separator that separates fine particles in fuel oil;
A method for desalinating fuel oil, comprising: an oil-water separator that separates moisture in fuel oil discharged from the centrifugal separator, the oil-water separator comprising fiber as an oil-water separation element. . 9. In claim 8, the centrifugal separator is arranged around a rotating shaft provided with a feedstock oil introduction hole, a sludge outlet hole, and a treated oil outlet hole after sludge removal, each of which communicates with each of the holes. 1. A fuel oil desalination device comprising a centrifugal extractor having an annular rotor with a space formed therein and having a sludge outflow control means.