JP6905430B2 - Crude oil-containing waste liquid treatment method and crude oil-containing waste liquid treatment equipment - Google Patents

Description

The present invention relates to a method for treating crude oil-containing waste liquid and a treatment facility used therein, and is suitable for use in treating waste liquid discharged from a cleaning step of a crude oil storage tank.

Crude oil imported from overseas is once stored in a crude oil tank and sent to the refining process as needed. The tank used for storage needs to be inspected regularly, at which time all the stored crude oil is drawn out and the inside of the tank is cleaned. As a method for cleaning the tank, a Crude Oil Washing method (hereinafter referred to as "COW") for washing away sludge accumulated in the tank with heated crude oil is widely applied. After the COW is carried out, hot water washing is performed to discharge a washing waste liquid called "warm water washing SLOP" in which sludge and water are mixed with crude oil.
The hot water washing SLOP contains sludge accumulated in the crude oil tank and high boiling point hydrocarbons such as wax and asphaltene contained in the crude oil. In addition, since the hot water washing SLOP also contains sludges remaining in the tank, it is desirable to separate and treat them by an appropriate treatment in order to treat them.
On the other hand, since the oil contained in the hot water washing SLOP is derived from crude oil, it is desirable to recover and refine it for effective use of resources. However, since oil containing water and sludge cannot be supplied to the crude oil refining process as it is, it is desirable that the sludge and water content of the recovered oil be as low as possible.

The crude oil refining process is not originally intended to process crude oil containing a large amount of water, and processes a large amount of crude oil-containing waste liquid having a high water content in which sludge and water are mixed with crude oil, such as hot water washing SLOP. If this is attempted, problems such as corrosion of the refining equipment may occur due to the influence of water and salts contained in the hot water washing SLOP. Therefore, the hot water washing SLOP is treated little by little, and there is a problem that the untreated hot water washing SLOP must be stored in the storage tank for a long period of time. Therefore, there has been a demand for the development of equipment capable of processing a large amount of hot water washing SLOP.

In order to meet these demands, various oil-water separation methods have been conventionally proposed. For example, an API that uses the difference in specific gravity between water and oil to supply oil-containing wastewater to a water tank with a certain residence time to float the oil, and an oil-water separation device called CPI that uses an inclined plate have been put into practical use. There is.

However, in the oil-water separation apparatus utilizing such a difference in specific densities, it is necessary to retain wastewater for a long time in the apparatus for separation, and there is a problem that the apparatus becomes large and the treatment time is long. In addition, the oil and water contained in the hot water washing SLOP are emulsions of oil droplets in water and water droplets in oil due to the presence of surface-active components and suspended solids in wax and crude oil, and are stably present. In some cases. In such a state, there is a problem that it is difficult to sufficiently separate oil and water by the separation method using the difference in specific densities.
In this respect, if a centrifuge is used, oil-water separation can be performed in a short time. For example, Patent Document 1 discloses a method of supplying oil containing water to a centrifuge and separating water and oil in a short time.
Further, Patent Document 2 also discloses a method of separating water and sludge from oil containing water by centrifugation. The oil-water separation method using such a centrifuge has an advantage that it can be performed in a relatively short time as compared with the oil-water separation due to the difference in specific gravity.
Further, in Patent Document 3, an anionic surfactant and an inorganic flocculant are added to the oil-containing wastewater to form oil flocs in advance, and then a nonionic surfactant is added and centrifuged to separate the oil from water. A method for separating sludge has been proposed.
Further, in Patent Document 4, an oil-water separation technique by centrifugation is described as a background technique, but it is pointed out that the high water content of the oil recovered by this technique is a problem.
Further, Patent Document 5 discloses a method for removing solids and salts from crude oil containing solids and salts. That is, warm water is added to the crude oil, an emulsion breaker is further added, and then these are mixed well with a stirrer. After that, the mixed liquid is demineralized in a static separation tank to separate water and solids. However, in the static separation tank, the mixture to be treated is left to stand and separated by using the difference in specific gravity between oil and water or solids, so it takes a long time to process, and if the amount of treatment is large, the capacity of the separation tank And water area needs to be increased

Japanese Unexamined Patent Publication No. 2006-104233 JP-A-2015-199848 JP-A-59-112808 Japanese Unexamined Patent Publication No. 2012-229403 Japanese Patent No. 4679680

However, when crude oil forms an emulsion in the hot water washing SLOP, it may be difficult to separate water and oil by the separation method using a centrifuge. Even in the test conducted by the present inventors, even if the hot water washing SLOP is simply centrifuged by the method of the above-mentioned patent document, water and oil may not be separated, and the oil-water separation is completed in a short time. There has been a demand for a more reliable oil-water separation treatment method for crude oil-containing waste liquids that makes the best use of these characteristics.
In addition, although various methods have been proposed for separating water and oil by using centrifugation, the water content of the recovered oil is still high, and further reduction has been desired. Therefore, when the oil is separated and refined from the hot water washing SLOP using a centrifuge and used, it has been desired to further reduce the water content.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to efficiently and reliably separate and recover oil and water from crude oil-containing waste liquid such as hot water washing SLOP in a short time. It is an object of the present invention to provide a method for treating crude oil-containing waste liquid and its treatment equipment.

The method for treating a crude oil-containing waste liquid according to the present invention includes an addition step of adding a coagulant to the crude oil-containing waste liquid, and the addition of the waste liquid at least at least before, at the time of addition, and after the addition of the coagulant. It is characterized by having a heating step of heating and a centrifugation step of separating the waste liquid to which the coagulant is added into three components of oil, water and solid.
Further, the crude oil-containing waste liquid treatment equipment according to the present invention includes an addition equipment for adding a coagulant to the crude oil-containing waste liquid, a heating equipment for heating the waste liquid, and the coagulant added and added. It is characterized by being equipped with a centrifuge for separating the warmed waste liquid into oil, water and solid matter.
Furthermore, another crude oil-containing waste liquid treatment equipment of the present invention is a crude oil-containing waste liquid treatment equipment, which is an addition equipment for adding a flocculant and an emulsion breaker to the waste liquid, and heating the waste liquid. It is characterized by being provided with a heating facility for heating, and a centrifuge for separating the heated waste liquid into oil, water and solid matter to which the coagulant and the emulsion breaker are added.

According to the present invention, it is possible to efficiently and reliably separate crude oil, water, and solid matter in a crude oil-containing waste liquid in a short time. Further, by separating crude oil from water and solid matter, crude oil in crude oil-containing waste liquid, which has been difficult to reuse in the past, can be recovered and used as a resource.

It is a schematic diagram of the treatment facility of the crude oil-containing waste liquid of Embodiment 1. It is a schematic diagram of the crude oil-containing waste liquid treatment equipment of Embodiment 2. It is a schematic diagram of the treatment facility of the crude oil-containing waste liquid of Embodiment 3. It is a schematic diagram of the hot water washing SLOP processing equipment of Embodiment 4 and Example 4. It is a schematic diagram of the treatment facility of the crude oil-containing waste liquid of Embodiment 5. It is a figure which shows the state of the hot water washing SLOP after centrifugation of Examples 2 and 3 and Comparative Examples 1 and 2. It is a graph which shows the relationship between the emulsion breaker addition rate and the water content of the recovered oil in Example 4. It is a graph which shows the relationship between the temperature and the water content of the recovered oil in Example 4.

As a result of intensive research to solve the above problems, the present inventor has added a flocculant to the waste liquid before separating the crude oil-containing waste liquid into oil and water by a centrifuge, so that the oil and water separation can be completed in a short time. We have found that it can be performed efficiently and reliably, and have completed the present invention.
That is, the method for treating the waste liquid containing crude oil of the present invention includes an addition step of adding a coagulant to the waste liquid containing crude oil, and the waste liquid at least at least before, at the time of addition, and after the addition of the coagulant. It is characterized by having a heating step of heating and a centrifugal separation step of separating the waste liquid to which the coagulant is added into three components of oil, water and solid.

Here, the coagulant refers to an additive added to agglomerate particles and oil droplets in a crude oil-containing waste liquid, and examples thereof include a coagulant composed of a polymer flocculant and an inorganic salt. As the polymer flocculant, one or a plurality of cationic polymer flocculants, anionic polymer flocculants, and nonionic polymer flocculants are appropriately selected in consideration of the surface charge of particles in the crude oil-containing waste liquid. do it. Further, as the flocculant composed of inorganic salts, aluminum sulfate (sulfate soil), polyaluminum chloride, iron chloride, polyiron sulfate and the like can be applied.

Examples of the cationic polymer flocculant include polyamine-based, polyimine-based, polydialyldialkylammonium chloride, and Mannich-modified products of polyacrylamide. Particularly preferred is a polyamine-based flocculant. The present inventors have confirmed that by using a polyamine-based flocculant as a flocculant, oil-water separation by centrifugation can be performed efficiently and reliably in a short time. Examples of the polyamine-based flocculant include polyamine-based condensates.
Examples of the anionic polymer flocculant include poly (meth) acrylic acid and salts thereof.
Examples of the nonionic polymer flocculant include poly (meth) acrylamide and the like.

Further, according to another embodiment of the present invention, it is preferable to add an emulsion breaker to the crude oil-containing waste liquid before performing the centrifugation treatment. For example, when the present invention is applied to the oil-water separation of the hot water washing SLOP, the hot water washing SLOP contains a wax component derived from crude oil and a component having surface activity. In such a waste liquid, wax components and components having surface activity gather at the interface between water and oil, forming a state in which it is difficult for water and oil to come into direct contact with each other. In this state, it is in the state of an O / W type emulsion in which minute oil droplets are stably present in water or a W / O type emulsion in which minute water droplets are stably present in oil.
Since the oil droplets in the emulsion (water droplets in the case of W / O type emulsion) are stabilized and it is difficult to separate them by a simple difference in specific density, such a waste liquid promotes separation by a difference in specific density using centrifugation. Is preferable.
By the way, when an emulsion breaker is allowed to act on the emulsified oil droplets (or water droplets), oil-water separation can be performed efficiently and reliably in a shorter time. The emulsion breaker is not particularly limited as long as it destroys the emulsion in the crude oil-containing waste liquid, and examples thereof include a cationic emulsion breaker, an anionic emulsion breaker, and a nonionic emulsion breaker. A plurality of these may be added.

Examples of the anionic emulsion breaker include sulfate ester type and sulfonic acid type anionic emulsion breakers. Examples of the sulfate ester type and sulfonic acid type anionic emulsion breakers include polyoxyalkylene alkyl ether sulfate (preferably polyoxyalkylene, oxyethylene having an average addition molar number of 1 to 5) and alkyl ether sulfate. (Preferably, the alkyl group has 8 to 22 carbon atoms), dialkyl sulfosuccinate salt, petroleum sulfonate, alkylnaphthalene sulfonate (preferably, the alkyl group has 0 to 5 carbon atoms), and the like. One or more selected species. These salts may be used, for example, ammonium salts, alkali metal (potassium, sodium, etc.) salts, alkaline earth metal (calcium, barium, etc.) salts, tertiary amines (eg, monoethanolamine, diethanolamine, triethanolamine). Etc.) etc. Examples of the polyoxyethylene alkyl ether sulfate ester salt include triethanolamine polyoxyethylene lauryl ether sulfate and sodium polyoxyethylene lauryl sulfate.

Examples of the nonionic emulsion breaker include polyoxyalkylene alkyl ether, alkylphenol alkylene oxide adduct / formalin condensate, polyalkylene glycol copolymer, alkylamine alkylene oxide adduct, and polyether polyol-based urethane resin. Can be mentioned. Examples of the cationic emulsion breaker include polyamine compounds such as N-polyoxyethylene polyalkylene polyamine, and one or more selected from these can be used.

Further, when the emulsion breaker is added to the waste liquid, it is preferable that an alkylphenol condensate is contained. The present inventors have confirmed that oil-water separation by centrifugation can be performed more effectively by using an alkylphenol condensate as an emulsion breaker. Examples of the alkylphenol condensate include an alkylene oxide adduct of the alkylphenol condensate.

On the other hand, it is also effective to heat the emulsified waste liquid to separate it into oil and water. Here, taking the crude oil-containing waste liquid as an example, the waxes cover the circumference of the oil droplets (or water droplets) as described above to prevent the oil droplets from coming into direct contact with the surrounding water and stabilize the emulsion. .. By the way, when the waxes are heated, they dissolve on the oil side, so when the waste liquid is heated, the waxes dissolve, and the oil droplets come into direct contact with the surrounding water, destabilizing the interface. The oil-water separation is promoted by the conversion.

In addition, suspended solids contained in crude oil-containing waste liquid such as hot water washing SLOP have a role of stabilizing the emulsion by covering the oil droplets (or water droplets) together with waxes, but float by heating. The waxes attached to the substance are also dissolved and removed in the oil, which destabilizes the emulsion. The suspended solids are recovered as sludge in the centrifugation step, but the removal of waxes from the suspended solids by heating can also be expected to have the effect of reducing the oil content in the sludge.

Heating also has the role of reducing the viscosity of the crude oil-containing waste liquid. When the viscosity is lowered, the effect of facilitating mixing of the above-mentioned chemicals such as emulsion breaker and flocculant can be expected. The emulsion breaker has the effect of entering the surfactant layer on the surface of oil droplets (or water droplets) and making the surfactant layer easily disturbed. Therefore, when the oil droplets collide with each other, they are likely to coalesce, and as a result, the oil droplets become coarse and separation is promoted. Since heating has the effect of dispersing the emulsion breaker and increasing the fluidity of the surfactant layer itself, it can be expected to have the effect of promoting oil-water separation.

For the above reasons, it is preferable to heat the waste liquid so that the temperature of the waste liquid is 45 ° C. or higher. If the temperature of the waste liquid is less than 45 ° C., the waxes that stabilize the emulsion of the waste liquid may not dissolve, so that the emulsion may be difficult to break due to the dissolution of the waxes, and oil-water separation may become difficult. .. Further, when the temperature of the waste liquid is less than 45 ° C., the viscosity of the waste liquid does not decrease so much, so that the effect of facilitating mixing of chemicals such as an emulsion breaker and a coagulant becomes difficult to be exhibited, and oil-water separation may also become difficult. There is.

On the other hand, when the temperature of the crude oil-containing waste liquid rises, the volatilization of oil components in the crude oil is promoted. Therefore, the temperature of the waste liquid is preferably 65 ° C. or lower. In particular, when the temperature of the waste liquid exceeds 60 ° C, it also exceeds the flash point of heavy oil, which is generally considered to be difficult to ignite. Therefore, it is more preferable to heat the crude oil-containing waste liquid to 55 ° C or less. Further, it is desirable to seal each equipment so that the volatilized oil component does not stay around the equipment and to have a structure in which flammable gas does not easily leak. Alternatively, it is desirable to have a structure that sucks the volatilized gas from each facility and volatilizes it in a safe place.

For the above reasons, the heating of the waste liquid is preferably in the range of 45 ° C. or higher and 65 ° C. or lower, and more preferably in the range of 45 ° C. or higher and 55 ° C. or lower.

The crude oil-containing waste liquid treatment equipment of the present invention is a crude oil-containing waste liquid treatment equipment, and the addition equipment for adding a coagulant to the waste liquid, the heating equipment for heating the waste liquid, and the coagulant are It is characterized by being provided with a centrifuge for separating the added and heated waste liquid into oil, water and solid matter.

Furthermore, another crude oil-containing waste liquid treatment facility of the present invention is a crude oil-containing waste liquid treatment facility, which aggregates the waste liquid into a heating facility for heating the waste liquid and the waste liquid before and after the heating. It is characterized by being provided with an addition facility for adding an agent and an emulsion breaker, and a centrifuge for separating the heated waste liquid to which the emulsion breaker is added into oil, water and solid matter. do.
In this case, it is preferable that the heating equipment can control the temperature of the waste liquid to a predetermined temperature of 45 ° C. or higher and 65 ° C. or lower. If the temperature of the waste liquid is less than 45 ° C., the waxes that stabilize the emulsion of the waste liquid may not dissolve, so that the emulsion may be difficult to break due to the dissolution of the waxes, and oil-water separation may become difficult. .. Further, when the temperature of the waste liquid is less than 45 ° C., the viscosity of the waste liquid does not decrease so much, so that the effect of facilitating mixing of chemicals such as an emulsion breaker and a coagulant becomes difficult to be exhibited, and oil-water separation may also become difficult. There is. On the other hand, from the viewpoint of preventing dissipation due to volatilization of oil components in crude oil as much as possible, the temperature of the waste liquid is preferably 65 ° C. or lower. In particular, when the temperature of the waste liquid exceeds 60 ° C, it also exceeds the flash point of heavy oil, which is generally considered to be difficult to ignite. Therefore, it is more preferable to heat the crude oil-containing waste liquid to 55 ° C or less.

Further, in the crude oil-containing waste liquid treatment equipment of the present invention, the oil-water separation equipment for removing the oil contained in the water separated from the centrifuge and the oil content separated by the oil-water separation equipment are stored in the waste liquid. It is preferable to have a return facility for returning to the tank and processing with a centrifuge again. Here, examples of oil-water separation equipment for removing oil contained in water separated from a centrifuge include equipment for separating oil by a pressurized flotation method, a membrane separation method, and API or CPI using a specific gravity difference. ..

<Explanation of Embodiment>
(Embodiment 1)
The treatment facility of the first embodiment is a facility for treating a crude oil-containing waste liquid, for example, a hot water washing SLOP which is a cleaning waste liquid of a crude oil storage tank, and as shown in FIG. 1, a flocculant and an emulsion breaker are added to the crude oil-containing waste liquid. A mixing tank 1 for adding, a heat exchanger 2 for heating the waste liquid flowing out of the mixing tank, and a centrifuge 3 for centrifuging the heated waste liquid flowing out of the heat exchanger 2. I have. The mixing tank 1 is connected to a coagulant storage tank (not shown) via a chemical injection pump 4, and is connected to an emulsion breaker storage tank (not shown) via a chemical injection pump 5. Further, the heat exchanger 2 is connected to a steam generating boiler (not shown) via a steam pipe 6. Further, a circulation pipe 7 for feeding back the heating waste liquid flowing out of the heat exchanger 2 to the mixing tank 1 is provided, and a circulation pump 8 is provided in the middle of the circulation pipe 7.

In the processing equipment of the first embodiment configured as described above, the crude oil-containing waste liquid is first supplied to the mixing tank 1, the coagulant and the emulsion breaker are added by the chemical injection pumps 4 and 5, and the stirrer or the like (not shown) is used. Stir and mix. Then, the waste liquid flowing out of the mixing tank 1 enters the heat exchanger 2, is heated by the steam supplied from the steam pipe 6, and is sent to the centrifuge 3. Further, it is centrifuged by a centrifuge 3 and separated into a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge and discharged. Hot water can also be used as the heat source supplied to the heat exchanger 2. Further, since the condensed water of steam supplied from the steam pipe 6 to the heat exchanger 2 becomes hot water at a high temperature, it can also be used as an auxiliary heat source for raising the temperature of the crude oil-containing waste liquid.
As described above, in the processing equipment of the first embodiment, the flocculant and the emulsion breaker are added and mixed in the mixing tank 1 before the crude oil-containing waste liquid is separated into the light liquid, the heavy liquid, and the sludge by the centrifuge 3. NS. Therefore, the oil, water, and solid matter of the crude oil-containing waste liquid can be efficiently and reliably separated and recovered in a short time. Further, since the wastewater is fed back from the heat exchanger 2 to the mixing tank 1 by using the circulation pipe 7 and the circulation pump 8, the crude oil-containing wastewater can be uniformly heated. For this reason, the waxes that stabilize the emulsion of the waste liquid dissolve and the emulsion is destroyed, facilitating the separation of oil and water.

(Embodiment 2)
As shown in FIG. 2, in the processing equipment of the second embodiment, the heat exchanger 12 is provided on the upstream side of the mixing tank 11. Other configurations are the same as those of the processing equipment of the first embodiment shown in FIG. 1, and the same configurations are designated by the same reference numerals and detailed description thereof will be omitted.

In the treatment equipment of the second embodiment, since the waste liquid is heated by the heat exchanger 12 before the coagulant and the emulsion breaker are added and mixed, the oil content in the waste liquid is before the coagulant and the emulsion breaker are added. There is an advantage that the viscosity is lowered and the chemicals can be mixed and dispersed in the mixing tank 11 more smoothly and in a short time. Other actions and effects are the same as those of the processing equipment of the first embodiment.

(Embodiment 3)
In the processing facility of the third embodiment shown in FIG. 3, the recovery oil tank 21 for recovering the light liquid discharged from the centrifuge 3 and the oil content in the heavy liquid discharged from the centrifuge 3 are separated. An oil-water separation tank 22 and a recovery oil return pipe 23 for returning the oil separated in the oil-water separation tank 22 to the mixing tank 1 and the circulation pipe 7 are provided. Other configurations are the same as those of the processing equipment of the first embodiment shown in FIG. 1, and the same configurations are designated by the same reference numerals and detailed description thereof will be omitted.

In the processing facility of the third embodiment, the light liquid is composed of the oil remaining after the water and sludge are separated, but the discharged light liquid is returned to the oil refining process again as recovered oil through the recovered oil tank 21. Will be. Further, although the main component of the heavy liquid is water, some of the oil and sludge that could not be separated may remain. Therefore, after discharging from the centrifuge 3, the heavy liquid is once supplied to the oil-water separation tank 22. After removing oil and sludge, it is discharged as treated water. Here, in the oil-water separation tank 22, in order to separate and remove oil and sludge from water, it is possible to apply API or CPI, which is a separation device utilizing the difference in specific gravity, but instead of this, for example, not shown. A membrane filtration device or a pressurized flotation device using a microfiltration membrane may be installed instead of the oil-water separation tank 22. Further, in order to further recover the oil from the concentrated oil or sludge, it is preferable to return the oil to the crude oil-containing waste liquid through the recovered oil return pipe 23. This is the suction of the circulation pump 8 installed in the inlet of the mixing tank 1 in the previous stage or in the circulation pipe 7 that feeds back the oil from the heat exchanger 2 to the mixing tank 1 when the oil remains in the water tank after the oil-water separation. It is returned to the side as needed to improve the oil recovery rate. Further, since the water separated in the oil-water separation tank 22 contains aggregated flocs, it is possible to enhance the aggregation effect by returning the flocs to the crude oil-containing waste liquid.
Other actions and effects are the same as those of the processing equipment of the first embodiment.

(Embodiment 4)
As shown in FIG. 4, the treatment equipment of the fourth embodiment has a structure in which a crude oil-containing waste liquid such as a hot water washing SLOP is circulated between the mixing tank 31 and the heat exchanger 32. The crude oil-containing wastewater discharged from the mixing tank 31 has a structure in which the emulsion breaker and the coagulant are supplied from a chemical supply tank (not shown) and then sent to the centrifuge 33. The crude oil-containing waste water is separated into a light liquid containing a large amount of crude oil, a heavy liquid containing a large amount of water, and sludge by the centrifuge 33, and the light liquid is stored in the light liquid tank 34 and the heavy liquid is stored in the heavy liquid tank 35. It has become so. The mixing tank 31, the light liquid tank 33, and the heavy liquid tank 34 have a closed structure, and a pipe 36 for eliminating the generated gas is connected, and the other end of the pipe 36 is connected to the odor stack 37. There is.

In the treatment equipment of the fourth embodiment configured as described above, since the crude oil-containing wastewater is heated by the heat exchanger 32 before being sent to the centrifuge 33, before adding the coagulant or the emulsion breaker. The viscosity of the oil in the wastewater is reduced, the flocculant and the emulsion breaker are easily mixed, and the oil-water separation of the emulsion is promoted. It is desirable to keep the heating at about 60 ° C. in order to suppress the volatilization of the components in the crude oil. It is also possible to install a mixing facility such as a line mixer or a stirring tank after adding a flocculant or an emulsion breaker. Further, in order to maintain the temperature up to the centrifuge, it is preferable that the heated piping and the centrifuge have a heat insulating structure.

Further, in the fourth embodiment, in order to remove the volatile components from the hot water washing SLOP, the mixing tank 31, the light liquid tank 34, the heavy liquid tank 35, etc. have a closed structure, and the pipe 36 for eliminating the generated gas is provided. Since it is guided to the odor stack 37 through the pipe, the volatile component can be safely diffused into the atmosphere. Since it is possible that the volatile component exceeds the lower limit of explosion depending on the concentration of the volatile component, it is desirable to provide a flashback prevention device in the odor stack and piping as necessary.

(Embodiment 5)
In the fifth embodiment shown in FIG. 5, the fourth embodiment is provided with the exception that the chemical supply tank for the emulsion breaker is not installed, and the pipe 36 and the odor stack 37 for removing the generated gas are not installed. It is the same as the processing equipment, and the same reference numerals are given to the same configurations, and detailed description thereof will be omitted.
According to the processing equipment of the fifth embodiment, the waste liquid is heated while being circulated between the mixing tank 31 and the heat exchanger 32, and then the coagulant is added. That is, since the coagulant is added to the waste liquid which has been heated and the viscosity of the oil has decreased, there is an advantage that mixing and dispersion with the coagulant can be performed more smoothly and in a short time. Other actions and effects are the same as those of the processing equipment of the first embodiment. In the fifth embodiment, the centrifugal separation is performed by adding only the coagulant without adding the emulsion breaker, but depending on the properties of the crude oil-containing waste liquid to be treated, the effect of separating oil and water only by adding the coagulant is effective. May be obtained. Therefore, it is desirable to carry out a laboratory-scale treatment test in advance to select an appropriate chemical and determine the injection rate.

The coagulant used in the treatment equipment of the first to fifth embodiments means an additive added to agglomerate particles in a crude oil-containing waste liquid, and for example, a coagulant composed of a polymer flocculant or an inorganic salt. Can be mentioned. As the polymer flocculant, one or a plurality of cationic polymer flocculants, anionic polymer flocculants, and nonionic polymer flocculants are appropriately selected in consideration of the surface charge of particles in the crude oil-containing waste liquid. do it. As the flocculant, a polyamine-type flocculant such as Hakuto Hakutron B-733 is suitable.
Further, the emulsion breaker used in the treatment equipment of the above-described first to fifth embodiments is a chemical that makes it easy to separate the liquid in the emulsion state into the aqueous phase and the oil phase, and is a nonionic alkylphenol such as Hakuto Hakuto E-523. A condensate, a nonionic polyether polyol urethane resin such as Hakuto EW-01, and an anionic dialkylsulfosuccinate salt such as Hakuto EW-02 are suitable.
The injection amount of each of these chemicals may be determined by conducting an oil-water separation test on a small scale in advance and appropriately determining the optimum addition amount.
In the first embodiment, the wastewater to which the coagulant and the emulsion breaker are added and mixed in the mixing tank 1 is heated by the heat exchanger 2, and in the second embodiment, the wastewater heated by the heat exchanger 12 is heated. When a flocculant or an emulsion breaker is added / mixed in the mixing tank 11, the viscosity of the oil in the wastewater decreases, whereby centrifugation is appropriately performed. According to the test results of the inventors, it is desirable to heat the oil-water separation to 40 ° C. or higher in order to properly treat the oil-water separation. However, depending on the components in the oil contained, oil having a low boiling point may be present, and if the temperature is too high, the amount of evaporation of such volatile components increases, so appropriate temperature control is important. Further, since the low boiling point component evaporates and vaporizes and diffuses into the atmosphere, which may cause an odor, the mixing tank 1, the centrifuge 3 in the subsequent stage, and the oil-water separation tank 22 are generated as a closed structure. It is desirable to separately suck the gas into the treatment facility or guide it to the odor stack and diffuse it. In addition, since the light liquid and the recovered oil may ignite due to static electricity, it is desirable that the centrifuge and the piping through which the light liquid and the recovered oil flow are grounded. It is also preferable to seal the constituent tanks and centrifuges, replace them with nitrogen gas, and maintain an environment in which ignition is difficult to occur.

The heated crude oil-containing waste liquid is supplied to the centrifuge 3. It is desirable to use a three-phase separator type centrifuge as the centrifuge used in the present invention. In general, crude oil-containing waste liquids such as hot water washing SLOP often contain sludge, which is a solid substance, in addition to oil and water. With a three-phase centrifuge, it is possible to separate oil, water, and sludge in one step.
For crude oil-containing waste liquid, it is desirable to determine the amount of oil-containing waste water supplied to the centrifuge while checking the distribution status of the light liquid and heavy liquid water discharged from the centrifuge.

An example of the method for treating a crude oil-containing waste liquid of the present invention will be described in detail in comparison with a comparative example.
(Example 1)
In Example 1, in order to examine the oil-water separation of the hot water washing SLOP using a three-phase centrifuge, an evaluation was carried out at the laboratory level.
The hot water washing SLOP (water content 18.8% by mass) discharged from the crude oil storage tank was used as the waste liquid for the test. After heating this test waste liquid to 50 ° C. in a water bath, an emulsion breaker (Hactol E-523) containing an alkylphenol condensate was added at a ratio of 10 mg / kg per crude oil to be treated, and the mixture was well stirred. Next, a polyamine-based flocculant (Hactron B-733) was added at a ratio of 500 mg / kg, and then further stirring was performed. The mixed solution thus obtained was supplied to a centrifuge and centrifuged, and separated into three phases of light liquid, heavy liquid, and sludge. The volume ratio of each phase was 15:23: 2. The light liquid was a viscous brown liquid, and the water content was measured to be 0.8% by mass, and the light liquid was considered to be almost oil. The heavy liquid was a transparent liquid with a slight brown tinge. The COD of the heavy liquid, the amount of the hexane extract, the total nitrogen, the total phosphorus, and the concentrations of various heavy metals were measured. As a result, as shown in Table 1, the concentration of the normal hexane extract was 1.4 mg / L, and it was considered that the heavy liquid consisted of almost water. Regarding other components, although the iron concentration was slightly high, the concentrations of nitrogen, phosphorus and heavy metals were low, and good water quality was obtained.

(Example 2)
In Example 2, the hot water washing SLOP (moisture content = 82%) discharged from the crude oil storage tank was subjected to the test. Hactron B-733 as a flocculant was added to the test oil so as to be 500 mg / kg, and the mixture was stirred, and no emulsion breaker was added. Others were treated by the same method as in Example 1.

(Example 3)
In Example 3, Hactol E-523 as an emulsion breaker was added to the test oil so as to be 10 mg / kg in the same warm water washing SLOP as in Example 2, and after stirring, Hactron B-733 as a coagulant was added to 500 mg / kg. It was added to the test oil and stirred so as to be. Others were treated in the same manner as in Example 1.

(Comparative Example 1)
In Comparative Example 1, neither a flocculant nor an emulsion breaker was added to the same hot water washing SLOP as in Example 2. Others were treated in the same manner as in Example 1.

(Comparative Example 2)
In Comparative Example 2, Hactol E-523 was added as an emulsion breaker to the test oil so as to be 10 mg / kg without adding a flocculant to the same warm water washing SLOP as in Example 2, and stirring was performed. Others were treated in the same manner as in Example 1.

<Results>
The result of the processing is shown in FIG. In Comparative Example 1 in which neither an emulsion breaker nor a flocculant was added, oil and water did not separate even after centrifugation. Further, the same result was obtained in Comparative Example 2 in which only the emulsion breaker was added.
On the other hand, in Example 2 in which only the flocculant was added and stirred, and in Example 3 in which the emulsion breaker and the flocculant were both added and stirred, the oil, water and sludge were separated into three phases. From the above, it was clarified that the addition of a coagulant is indispensable for separating the water, oil and sludge of the hot water washing SLOP.

(Example 4)
In Example 4, the equipment shown in FIG. 4 was used to attempt to treat the hot water washing SLOP generated from the washing of the crude oil tank. The water content of the hot water washing SLOP used in the test was 26 to 35%, and the toluene insoluble content was about 1%.
In the treatment test, the hot water washing SLOP, which is the raw water, was heated to a predetermined temperature. Then, Hactol E-523 as an emulsion breaker and Hactron B-733 as a flocculant were added, and then the mixture was supplied to a three-phase separator type centrifuge.
FIG. 7 shows the water content of the recovered oil (light liquid) when the hot water washing SLOP was supplied to the centrifuge at 400 L / hr and the E-523 addition rate was added at a ratio of 0 to 40 mg / L. The liquid temperature of the hot water washing SLOP was set to 52 ° C., and the addition rate of B-733 was set to 300 mg / L.
As a result, as shown in FIG. 7, it was observed that the water content of the recovered oil tended to decrease as the addition rate of E-523 increased, and the water content decreased to about 1.1% under the condition of the addition rate of 40 mg / L. did. From this result, it was shown that increasing the addition rate of the emulsion breaker while adding the flocculant is effective in reducing the water content of the recovered oil. In general, an emulsion breaker is a kind of surfactant, and it is known that emulsification is promoted again when the addition rate becomes excessive. Therefore, in this example, the maximum emulsion breaker addition rate was set to 40 mg / L. ..

(Example 5)
In Example 5, in order to evaluate the effect of adding the flocculant, after warming the warm water washing SLOP, E-523 was added at a ratio of 20 mg / L and B-733 was added at a ratio of 500 mg / L to form a three-phase separation type. The test supplied to the centrifuge was carried out.
As a result, the concentration of suspended solids in the obtained heavy liquid was 1000 mg / L, and the COD was 670 mg / L.

(Comparative Example 3)
In Comparative Example 3, after heating the same hot water washing SLOP as in Example 5, only 20 mg / L of E-523 was added, and a test was carried out in which it was supplied to a three-phase separation type centrifuge.
As a result, the obtained separated water (heavy liquid) contains a black suspended solid, and as in the case of Comparative Example 2, the suspended solid in the heavy liquid remains as it is without precipitating, and the appearance is apparent. It was a black suspension. From this result, it was considered effective to add a coagulant to facilitate the coagulation of suspended solids in order to improve the water quality of the heavy liquid, as in the cases of Examples 2 and 3. The properties of the recovered heavy liquid were a suspended solid concentration of 3400 mg / L and a chemical oxygen demand (COD) of 1800 mg / L.
From the comparison between Example 5 and Comparative Example 3, it was confirmed that the coagulant was added before centrifugation, which was effective in improving the heavy liquid properties.

(Example 6)
In Example 6, the relationship between the temperature of the hot water washing SLOP and the oil content was investigated. Here, the supply amounts of the hot water washing SLOP to the centrifuge were set to 250 L / hr and 500 L / hr. The results are shown in FIG. Here, the temperature of the hot water washing SLOP was adjusted so that the temperature of the recovered oil (light liquid) discharged from the centrifuge became the set value.
As a general tendency, the water content of the recovered oil tends to decrease as the temperature rises, and the water content tends to decrease when the amount of hot water washing SLOP supplied to the centrifuge is low at the same temperature. Was recognized.
Under the condition of 250 L / hr, the water content decreased to less than 2% at 50 ° C. or higher, and the water content decreased to 0.9% at 55 ° C. Further, under the condition that the hot water washing SLOP supply amount was 500 L / hr, the water content became less than 2% when the temperature exceeded 55 ° C., and the water content decreased to 1.4% at 66 ° C., but this temperature ignited heavy oil. Since the point is exceeded and measures are required to prevent the recovered oil from catching fire, it was necessary to recover the light liquid in a container that can be sealed in Example 4.

(Example 7)
In Example 7, the hot water washing SLOP was treated in the same treatment equipment as in Example 4. The hot water washing SLOP was heated to 50 ° C. Next, 200 mg / L of EW-01 and 20 mg / L of EW-02 (both from Hakuto Co., Ltd.) were added as emulsion breakers, 300 mg / L of Hactron B-733 was added as a flocculant, and then three phases were added. It was supplied to a separation type centrifuge.
The amount supplied to the centrifuge was set to 400 L / hr, and the recovered oil (light liquid), separated water (heavy liquid), and sludge were recovered. The water content of the recovered oil was 0.6%, which was slightly lower than the water content of the recovered oil obtained in each test of Example 4.

The present invention is not limited to the embodiment of the above invention and the description of the examples. Various modifications are also included in the present invention as long as they do not deviate from the claims and can be easily conceived by those skilled in the art.

The present invention can be used for treating waste liquids containing crude oil.

Claims (6)

It is a method of treating waste liquid containing crude oil.
An addition step of adding a flocculant and an emulsion breaker to the waste liquid, and
A mixing step of mixing the coagulant and the waste liquid to which the emulsion breaker is added in a mixing tank, and
A heating step in which the waste liquid mixed by the mixing step is heated by a heating facility, and
A part of the waste liquid heated by the heating step is returned to the mixing tank by connecting pipes, and circulated between the mixing tank and the heating equipment to make the temperature of the waste liquid uniform, and to make the temperature of the waste liquid uniform. A circulation process that breaks the emulsion and facilitates oil-water separation,
The flocculant and the emulsion breaker are added and mixed, and the heated waste liquid is centrifuged to separate it into a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge. Process and
The light liquid tank supply process for supplying the light liquid containing the oil as the main component to the light liquid tank, and
The heavy liquid tank supply process for supplying the heavy liquid containing water as the main component to the heavy liquid tank, and
The mixing tank, the light liquid tank, and the heavy liquid tank have a closed structure, pipes are connected to the tanks, and volatile components are connected to the pipes for eliminating volatile gas generated in the tanks. And the gas elimination process that diffuses the air into the atmosphere
Have a,
A method for treating a crude oil-containing waste liquid, which comprises returning the heavy liquid containing the water as a main component supplied to the heavy liquid tank to the mixing tank. It is a method of treating waste liquid containing crude oil.
A mixing step of mixing the waste liquid in a mixing tank and
A heating step in which the waste liquid mixed by the mixing step is heated by a heating facility, and
A part of the waste liquid heated by the heating step is returned to the mixing tank by connecting pipes, and circulated between the mixing tank and the heating equipment to make the temperature of the waste liquid uniform, and to make the temperature of the waste liquid uniform. A circulation process that breaks the emulsion and facilitates oil-water separation,
An addition step of adding a flocculant and an emulsion breaker to the waste liquid after the mixing step, and
The flocculant and the emulsion breaker are added and mixed, and the heated waste liquid is centrifuged to separate it into a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge. Process and
The light liquid tank supply process for supplying the light liquid containing the oil as the main component to the light liquid tank, and
The heavy liquid tank supply process for supplying the heavy liquid containing water as the main component to the heavy liquid tank, and
The mixing tank, the light liquid tank, and the heavy liquid tank have a closed structure, pipes are connected to the tanks, and volatile components are connected to the pipes for eliminating volatile gas generated in the tanks. And the gas elimination process that diffuses the air into the atmosphere
Have,
A method for treating a crude oil-containing waste liquid, which comprises returning the heavy liquid containing the water as a main component supplied to the heavy liquid tank to the mixing tank. It is a method of treating waste liquid containing crude oil.
A heating process in which the waste liquid is heated by a heating facility, and
An addition step of adding a flocculant and an emulsion breaker to the heated wastewater, and
A mixing step of mixing the coagulant and the waste liquid to which the emulsion breaker is added in a mixing tank, and
A part of the waste liquid mixed by the mixing step is returned to the heating equipment by piping connection, and the temperature of the waste liquid is made uniform by circulating between the heating equipment and the mixing tank, and the emulsion of the waste liquid is made. A circulation process that causes destruction and facilitates oil-water separation,
A centrifugal separation step of separating the waste liquid mixed by the mixing step into a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge.
The light liquid tank supply process for supplying the light liquid containing the oil as the main component to the light liquid tank, and
The heavy liquid tank supply process for supplying the heavy liquid containing water as the main component to the heavy liquid tank, and
The mixing tank, the light liquid tank, and the heavy liquid tank have a closed structure, pipes are connected to the tanks, and volatile components are connected to the pipes for eliminating volatile gas generated in the tanks. And the gas elimination process that diffuses the air into the atmosphere
Have a,
A method for treating a crude oil-containing waste liquid, which comprises returning the heavy liquid containing the water as a main component supplied to the heavy liquid tank to the mixing tank. The method for treating a crude oil-containing waste liquid according to any one of claims 1 to 3, wherein the emulsion breaker contains an alkylphenol condensate. The method for treating a crude oil-containing waste liquid according to any one of claims 1 to 4 , wherein the waste liquid containing crude oil is heated at a temperature within the range of 45 ° C. or higher and 65 ° C. or lower before the centrifugation step. .. The method for treating a crude oil-containing waste liquid according to any one of claims 1 to 5 , wherein the flocculant contains a polyamine-based flocculant.

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