JP6809997B2 - 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 device for treating crude oil-containing waste liquid, for example, a method for treating crude oil-containing waste liquid suitable for treating waste liquid discharged from a cleaning step of a crude oil storage tank and a device for treating crude oil-containing waste liquid. Regarding.

Crude oil imported from overseas is once stored at a crude oil storage base 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 The tank used for storage needs to be inspected regularly, at which time all the stored crude oil is withdrawn and the inside of the tank is cleaned. As a method for cleaning the tank, a Crede Oil Washing method (hereinafter referred to as COW) for washing away sludge accumulated in the tank with heated crude oil is widely applied. At COW, cleaning waste liquid called hot water cleaning slop, in which sludge and water are mixed with crude oil, is discharged.

The hot water cleaning slop contains sludge such as iron and sand accumulated in the crude oil tank, and high boiling point hydrocarbons such as wax and asphaltene contained in the crude oil.The hot water cleaning slop separates these by appropriate treatment. It is desirable to process.

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 from the viewpoint of effective use of resources and reduction of waste amount. However, it is difficult to supply oil containing water and sludge to the crude oil refining process as it is, and it is desirable to recover the oil from which sludge and water have been removed.

Originally, the crude oil refining process is not supposed to process crude oil containing a large amount of water, and when refining a large amount of oil mixed with water or sludge such as hot water washing slop, it is included in the hot water washing slop. Due to the influence of water and salts, there are problems such as corrosion of refining equipment and difficulty in separating oil and water. For this reason, 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 an apparatus 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 raw water to a water tank having a certain residence time to float the oil, and an oil-water separation device called a CPI that uses an inclined plate have been put into practical use.

However, in the oil-water separation apparatus utilizing such a difference in specific gravity, 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 slop may emulsify 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 may exist stably. .. In such a state, there is a problem that it is difficult to sufficiently separate oil and water even if a separation method using a difference in specific gravity is used. 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. Patent Document 2 also discloses a method for 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.

In Patent Document 3, an anionic surfactant and an inorganic flocculant are added to oil-containing wastewater, heated to 40 ° C. to 50 ° C., oil flocs are formed in advance, and then a nonionic surfactant (emulsion) is formed. A method has been proposed in which water and sludge are separated from the oil by adding (corresponding to a breaker) and centrifuging. Patent Document 4 describes an oil-water separation technique by centrifugation as a background technique, but it has been pointed out that the high water content of the oil recovered by this technique is a problem.

Patent Document 5 discloses a method for removing solids and salts from crude oil containing solids and salts. Warmed water is added to the crude oil, an emulsion breaker is further added, and these are mixed well with a stirrer. It is stated that. The mixed solution is supplied to a static separation tank to separate desalted oil and water or solids.

Patent Document 6 discloses a configuration in which a flocculant is added, then heated, and centrifuged. Patent Document 7 describes a configuration in which a flocculant is added, then heated, and a dehuminant (emulsion breaker) is added and then centrifuged. Patent Document 8 describes that the emulsion is broken and then heated or centrifuged. It is stated that. Patent Document 9 describes an example of an emulsion breaker (mineral oil emulsion separating agent).

Japanese Unexamined Patent Publication No. 2006-104233 JP-A-2015-199848 JP-A-59-112808 JP 2012-229403 Japanese Patent No. 4679680 Special Table 2007-526123 International Publication No. 2013/091032 Japanese Unexamined Patent Publication No. 50-131876 Japanese Unexamined Patent Publication No. 53-137883

However, in the method described in Patent Document 1, the oil-containing waste liquid is heated to 75 ° C. to 92 ° C. and then separated into oil, water and sludge by a centrifuge. The generated sludge and water are incinerated and disposed of in a kiln, and if the amount of separated water is large, combustion becomes difficult and there is a problem that a combustion improver or the like is required.

In Patent Document 2, coarse particles are removed from the oil-containing waste liquid by floating separation and sedimentation separation, and then separated into oil, water, and sludge by a centrifuge. Here, in order to reduce the water content of the oil, the separated oil is heated to about 100 ° C. to evaporate the water content, and the amount of energy required to reduce the water content of the oil becomes large. Moreover, since the separated water is incinerated, if the amount of separated water is large, the energy consumption becomes excessive.

In Patent Document 3, it is necessary to add an anionic surfactant and an inorganic flocculant to the oil-containing wastewater, the amount of the chemicals added increases, and problems such as the cost of using the two kinds of chemicals and the labor of addition remain. Was there. In addition, if pollutants remain in the generated separated water, they are treated by the activated sludge treatment method, resulting in an excessive facility.

In Patent Document 4, it was a problem that the water content of the recovered oil was high. In Patent Document 5, since the static separation tank allows the mixed solution to be treated to stand still and separates it by utilizing the difference in specific gravity between oil and water or a solid substance, the treatment time is long and the amount of treatment is large. In that case, it is necessary to increase the capacity of the separation tank.

In Patent Document 6, in order to separate the emulsified oil-containing waste liquid, an emulsion breaker is added to promote oil-water separation, then the oil is separated, and further, the oil, water, and solid content are separated by the second-stage oil-water separation. This method requires two sets of oil-water separation equipment, so if the equipment becomes excessive or the separated water is contaminated, treatment is required.

In Patent Document 7, in order to separate the oil-containing waste liquid, after performing a heating treatment and a filtration treatment, the oil, water and sludge are separated by a centrifuge. The separated oil is further separated into oil, water and sludge by a centrifuge, and the separated water is further separated into oil, water and sludge by a centrifuge. Since this method requires multiple centrifuges, sludge and oil are separated by centrifuging the separated water again and the equipment becomes excessive, but pollutants with a small specific gravity difference from water are sufficient. It cannot be completely removed.

Patent Document 8 describes an emulsion breaker added to separate oil and water from an emulsified oil-containing waste liquid, but there is no description about the separated water treatment, and when the separated water is contaminated, further Processing is required. Patent Document 9 does not show a specific treatment method using centrifugation, which only discloses an emulsion breaker.

As described above, in the past, depending on the type of crude oil, the crude oil formed an emulsion in the crude oil-containing waste liquid slop, and it was difficult to separate by the separation method using a centrifuge. Even in the tests conducted by the present inventors, oil and water may not be separated even if the crude oil-containing waste liquid slop is simply centrifuged by the method of each patent document described above, 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 takes advantage of the characteristics of separation.

In addition, various methods have been proposed in each patent document as a method for separating water and oil by using centrifugation. For example, when oil is separated from a hot water washing slop and the oil is refined and used. Although it is desirable that the water content in the recovered oil is low, there is a limit to the reduction in the water content in the recovered oil, and there are still problems.

The inventors studied to solve these problems, and in Japanese Patent Application No. 2017-036731, proposed a method for treating crude oil-containing waste liquid. In this proposal, the crude oil-containing waste liquid is preheated before centrifugation, and then centrifuged after adding a flocculant and an emulsion breaker. This makes it possible to reduce the water content of the oil recovered after centrifugation (hereinafter referred to as "light liquid") to about 1%, which has been difficult with conventional centrifuges. It makes it possible to reduce the rate.

However, in this proposal, sludge and oil may still remain in the water (hereinafter referred to as "heavy liquid") obtained after separating the crude oil-containing waste liquid, so it is difficult to discharge it into the environment as it is. Therefore, a treatment method that can obtain separated water with better water quality has been required.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to efficiently recover oil and water in a crude oil-containing waste liquid such as slop, reduce the amount of coagulant used, and further. It is an object of the present invention to provide a method for treating a crude oil-containing waste liquid and an apparatus for treating the crude oil-containing waste liquid, which can further improve the water quality of the separated wastewater.

As a result of diligent studies to solve the above problems, the present inventors have added a flocculant to the heavy liquid obtained after separating the crude oil-containing waste liquid into oil and water by a centrifuge, or carried out a membrane filtration treatment. By doing so, it was found that the properties of the obtained treated water were improved, and the present invention was completed.

The present invention completed based on the above findings has, in one aspect, a heating step of heating a waste liquid containing crude oil to 45 to 65 ° C. and an emulsion breaker addition step of adding an emulsion breaker to the heated waste liquid. , The waste liquid to which the emulsion breaker is added is centrifuged to separate it into three components: a light liquid containing oil as the main component, a heavy liquid containing water as the main component, and sludge. Provided is a method for treating a crude oil-containing waste liquid, which comprises a step of adding a coagulant to the obtained heavy liquid and coagulating oil and sludge remaining in the heavy liquid.

In one embodiment, the method for treating a crude oil-containing waste liquid according to the present invention further includes a solid-liquid separation step of solid-liquid separation treatment of a heavy liquid to which a coagulant is added to obtain treated water and a solid substance.

In another embodiment, the method for treating a crude oil-containing waste liquid according to the present invention includes a solid-liquid separation step of floating and separating a heavy liquid to which a coagulant is added to obtain floating sludge and treated water.

In still another embodiment of the method for treating crude oil-containing waste liquid according to the present invention, in the solid-liquid separation step, a heavy liquid to which a coagulant is added is settled in water under the action of gravity to be treated with treated water. Includes obtaining with solids.

In another aspect of the present invention, a heating step of heating a waste liquid containing crude oil to 45 to 65 ° C., an emulsion breaker addition step of adding an emulsion breaker to the heated waste liquid, and an emulsion breaker are added. The waste liquid is centrifuged, and the light liquid containing oil as the main component, the heavy liquid containing water as the main component, and the sludge are separated into three components, and the heavy liquid obtained in the centrifugation step is a film. Provided is a method for treating a crude oil-containing waste liquid, which comprises a membrane filtration treatment step for performing a filtration treatment.

In still another aspect of the present invention, there are a heating means for introducing a waste liquid containing crude oil into a mixing tank and heating the waste liquid from the mixing tank to 45 to 65 ° C., and a mixing tank and a heating means. A circulation means for circulating the waste liquid between them, an emulsion breaker addition means for adding an emulsion breaker to the heated waste liquid, and a light liquid containing oil as a main component and water by centrifuging the waste liquid to which the emulsion breaker is added. A coagulant is added to a centrifuge that separates the heavy liquid and sludge containing the main component into three components, and the heavy liquid obtained from the centrifuge to coagulate the oil and sludge remaining in the heavy liquid. A crude oil-containing waste liquid treatment apparatus including a coagulant-adding means and a solid-liquid separation means for solid-liquid separation treatment of a heavy liquid to which a coagulant is added is provided.

In yet another aspect of the present invention, a heating means for introducing a waste liquid containing crude oil into a mixing tank and heating the waste liquid from the mixing tank to 45 to 65 ° C., and a mixing tank and a heating means. A circulation means for circulating the waste liquid between them, an emulsion breaker addition means for adding an emulsion breaker to the heated waste liquid, a waste liquid to which the emulsion breaker has been added, and a light liquid containing oil as a main component and water. Provided is a crude oil-containing waste liquid treatment device equipped with a centrifuge that separates a heavy liquid containing the main component and sludge into three components, and a membrane filtration means that performs membrane filtration treatment of the heavy liquid obtained from the centrifuge. Will be done.

According to the present invention, oil and water in crude oil-containing waste liquid such as slop can be efficiently recovered, the amount of coagulant used can be reduced, and the quality of separated wastewater can be further improved. A method for treating the contained waste liquid and a device for treating the crude oil-containing waste liquid can be provided.

It is a schematic diagram which shows an example of the crude oil-containing waste liquid processing apparatus which concerns on 1st Embodiment of this invention, and is the schematic diagram of the slop processing apparatus of Example 1. It is a schematic diagram which shows an example of the crude oil-containing waste liquid processing apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows an example of the crude oil-containing waste liquid processing apparatus which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows an example of the crude oil-containing waste liquid processing apparatus which concerns on 4th Embodiment of this invention, and is the schematic diagram of the slop processing apparatus of Example 2. It is a graph which shows the relationship between the addition amount of an emulsion breaker, and the water content of a recovered oil (light liquid). It is a graph which shows the relationship between the light liquid outlet temperature and the water content. It is a graph which shows the relationship between COD in treated water and the amount of coagulant added. It is a graph which shows the relationship between the addition amount of a flocculant and the concentration of suspended solids in treated water.

Hereinafter, the first to fourth embodiments of the present invention will be described with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. It should be noted that the embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention describes the structure, arrangement, etc. of the components as follows. It is not specific to the thing.

(First Embodiment)
As shown in FIG. 1, the crude oil-containing waste liquid treatment apparatus according to the first embodiment of the present invention includes a mixing tank 1 for storing crude oil-containing waste liquid (hereinafter referred to as “crude oil-containing waste liquid”) and a mixing tank. A heating means 2 for heating the crude oil-containing waste liquid in 1, an emulsion breaker adding means 3 for adding an emulsion breaker to the heated crude oil-containing waste liquid, and a centrifuge for centrifuging the crude oil-containing waste liquid to which the emulsion breaker is added. The separator 4 is provided with a coagulant adding means 6 for adding a coagulant to a heavy liquid containing water as a main component obtained from the centrifuge 4 and coagulating oil and sludge remaining in the heavy liquid.

The crude oil-containing waste liquid to be treated in the present invention is not limited to the following, and examples thereof include a hot water washing slop in which sludge and water generated in COW are mixed with crude oil.

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. This state is called 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.

The oil droplets (water droplets in the case of W / O type emulsion) in the emulsion are stabilized, and it is difficult to separate them by a separation method based on a simple specific gravity difference such as API or CPI. Therefore, in the present invention, the centrifuge 4 is basically used to promote oil-water separation by the difference in specific gravity.

The mixing tank 1 and the heating means 2 are connected by a circulation means 15. The crude oil-containing waste liquid stored in the mixing tank 1 is supplied to the heating means 2 via the circulation means 15, heated, and circulated to the mixing tank 1. The heating means 2 is not particularly limited as long as it is a device for heating the crude oil-containing waste liquid, but a heat exchanger or the like is preferably used. For example, the heating means 2 is supplied with steam for heating as a heat source from the outside, and can heat the crude oil-containing waste liquid supplied from the mixing tank 1 to a predetermined temperature.

The crude oil-containing waste liquid stored in the mixing tank 1 is heated by the heating means 2 to reduce its viscosity, and the fluidity of the surfactant layer contained in the crude oil-containing waste liquid is increased, so that it is easily disturbed. As a result, the effect that oil-water separation can be performed more efficiently can be expected. In addition, the suspended solids contained in the crude oil-containing waste liquid have a role of stabilizing the emulsion by covering the oil droplets (or water droplets) together with the waxes. The effect of destabilizing the emulsion can also be expected by dissolving and removing the waxes adhering to the suspended solids in the oil phase by heating.

The heating temperature of the crude oil-containing waste liquid is appropriately set depending on the components in the crude oil-containing waste liquid. Generally, when the temperature of the crude oil-containing waste liquid rises, the volatilization of the oil components in the crude oil is promoted, so the temperature is set to 65 ° C or lower. Is preferable. On the other hand, if the temperature of the crude oil-containing waste liquid exceeds 60 ° C, it may exceed the flash point of heavy oil, which is generally considered to be difficult to ignite. Therefore, the temperature of the crude oil-containing waste liquid should be 60 ° C or less, further 55 ° C or less. It is desirable to stay. The lower limit of the heating temperature of the crude oil-containing waste liquid may be 45 ° C. or higher, more preferably 50 ° C. or higher, in consideration of the above-mentioned effects of heating and the effect of lowering the water content of the light liquid due to the addition of the emulsion breaker. preferable.

There is an emulsion breaker injection point between the mixing tank 1 and the centrifuge 4, and the emulsion breaker is injected from this injection point by the emulsion breaker adding means 3. The emulsion breaker has the effect of entering the surfactant layer on the surface of oil droplets (or water droplets) in the crude oil-containing waste liquid 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 (or water droplets) become coarse and the separation is promoted. It should be noted that the decrease in the viscosity of the crude oil-containing waste liquid due to the above-mentioned heating can be expected to have the effect of facilitating the dispersion of the emulsion breaker and the mixing of the emulsion breaker with the surfactant layer.

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 a sulfate ester type and a sulfonic acid type anionic emulsion breaker. Examples of the 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), alkyl ether sulfate ester salt (preferably oxyethylene having an average addition molar number of 1 to 5) Preferred are alkyl groups having 8 to 22 carbon atoms), dialkyl sulfosuccinate salts, petroleum sulfonates and alkylnaphthalene sulfonates (preferably alkyl groups having 0 to 5 carbon atoms), and the like, which are selected from these. One or more of these. 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, polyether polyol urethane resin, and polyamine compound. For example, N-polyoxyethylene polyalkylene polyamine and the like can be mentioned, and one or more selected from these.

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.

As for the addition amount of the emulsion breaker, it is desirable to carry out an addition test on a small scale in advance to determine an appropriate addition amount. As an example, it is preferably 0 to 40 mg / L with respect to the crude oil-containing waste liquid.

Although omitted in FIG. 1, in order to mix the emulsion breaker well with the crude oil-containing waste liquid, a stirring facility such as a line mixer or a stirring tank may be installed between the injection point of the emulsion breaker and the centrifuge 4. It is possible. The emulsion breaker may be added in the mixing tank 1 and the emulsion breaker and the crude oil-containing waste liquid may be mixed by using the circulation means 15 for heating. By circulating the crude oil-containing waste liquid between the mixing tank 1 and the heating means 2, the temperature is stabilized, and thus the effect of the emulsion breaker can be stably obtained.

The crude oil-containing waste liquid to which the emulsion breaker has been added is supplied to the centrifuge 4. As the centrifuge 4, it is desirable to apply a three-phase separation type centrifuge 4. The crude oil-containing waste liquid supplied to the centrifuge 4 is separated into three components: a liquid containing oil as a main component (light liquid), a liquid containing water as a main component (heavy liquid), and sludge.

The sludge is discharged to the outside of the system, and the light liquid is stored in the light liquid tank 5. Since the rotation speed of the centrifuge 4 and the supply amount of the crude oil-containing waste liquid affect the separation of the three components in the centrifuge 4, the optimum treatment conditions are determined according to the actual properties of the crude oil waste liquid. Is desirable.

Since the light liquid generated from the centrifuge 4 has a low water content and sludge is also separated, it can be effectively used by supplying it to a crude oil tank or a refining process. Due to centrifugation, the heavy liquid is mixed with oil and part of sludge in addition to water. Therefore, since the heavy liquid cannot be discharged into the environment as it is, the heavy liquid is further treated in the present invention.

That is, in the processing apparatus according to the first embodiment, the coagulant is added from the coagulant adding means 6 to the heavy liquid obtained in the centrifugation step to coagulate the oil and sludge remaining in the heavy liquid. Perform the coagulant addition treatment. By removing the agglomerates from the heavy liquid that has been subjected to the coagulant addition treatment, the water quality of the separated wastewater can be further improved.

The coagulant refers to an additive added to coagulate particles and oil droplets in a crude oil-containing waste liquid, and examples thereof include a coagulant composed of a polymer coagulant and an inorganic salt. As the polymer flocculant, one or more of a cationic polymer flocculant, an anionic polymer flocculant, and a nonionic polymer flocculant 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. Further, examples of the nonionic polymer flocculant include poly (meta) acrylamide and the like.

It is desirable to centrifuge the crude oil-containing waste liquid in advance and perform a small-scale treatment test using the obtained heavy liquid to determine the appropriate amount of the coagulant to be added. As an example of the amount of the flocculant added, it is preferably 100 to 200 mg / L with respect to a heavy liquid having a suspended substance concentration of 3400 mg / L and a chemical oxygen requirement (COD) of 1800 mg / L.

The heavy liquid to which the flocculant is added is supplied to the solid-liquid separation means 7 and subjected to solid-liquid separation treatment to obtain treated water and solid matter (sludge). The solid-liquid separating means 7 is not particularly limited as long as it can remove the agglomerated aggregates in the heavy liquid. For example, an apparatus utilizing gravity sedimentation separation, centrifugation, levitation separation, coagulation separation, membrane separation and the like can be used as the solid-liquid separation means 7.

According to the crude oil-containing waste liquid treatment apparatus and treatment method according to the first embodiment of the present invention, an emulsion breaker is added and mixed before the crude oil-containing waste liquid is centrifuged by the centrifuge 4. The oil and water of the crude oil-containing waste liquid can be efficiently and reliably separated and recovered in a short time.

Further, although a coagulant is added to the heavy liquid generated after centrifugation, the centrifugal separation efficiency is improved by adding and mixing the emulsion breaker, so that the amount of oil and sludge remaining in the heavy liquid is small. .. Therefore, the amount of the flocculant added can be small. Oil and sludge contained in the heavy liquid after centrifugation are aggregated by a flocculant and separated, so that treated water having good water quality can be obtained.

(Second Embodiment)
As shown in FIG. 2, the crude oil-containing waste liquid treatment apparatus and treatment method according to the second embodiment of the present invention are connected to a mixing tank 1, a centrifuge 4, a light liquid tank 5, and a solid-liquid separation means 7. The odor stack 9 is further provided.

Further, in the treatment apparatus shown in FIG. 2, as the solid-liquid separation means 7, a settling basin in which a heavy liquid to which a coagulant is added is settled in water under the action of gravity to obtain treated water and a solid substance is provided. Have been placed. Others are substantially the same as the crude oil-containing waste liquid treatment apparatus and treatment method according to the first embodiment, and thus the description thereof will be omitted.

Since the crude oil-containing waste liquid contains volatile oil, the amount of evaporation of volatile components increases when heated. In particular, if low boiling point components evaporate and vaporize and diffuse into the atmosphere, there is a risk of ignition. In the processing apparatus and processing method according to the second embodiment, the mixing tank 1, the centrifuge 4, the light liquid tank 5, and the solid-liquid separating means 7 have a closed structure, and the generated gas is odorized via the line A. Lead to bump 9 and spread in a safe environment. Alternatively, although the odor stack 9 is shown in FIG. 2, the odor stack 9 is separately sucked into a safe processing facility via the line A instead of the odor stack 9. As a result, the processing device can be operated more safely.

Depending on the concentration of the volatile component contained in the crude oil-containing waste liquid, the volatile component may exceed the lower limit of the explosion. Therefore, it is desirable to provide a flashback prevention device in the odor stack 9 and the piping as necessary. Further, it is desirable to seal each treatment device so that the volatilized oil component does not stay around the treatment device so that the flammable gas does not easily leak. Alternatively, it is desirable to have a structure that sucks the volatilized gas from each processing device and volatilizes it in a safe place. It is also preferable to seal the mixing tank 1 and the centrifuge 4 and replace them with nitrogen gas to maintain an environment in which ignition is difficult to occur. Since light liquids and recovered oils may ignite due to static electricity, it is desirable that the centrifuge 4 and the piping through which the crude oil-containing waste liquid flows are grounded.

(Third Embodiment)
As shown in FIG. 3, the crude oil-containing waste liquid treatment apparatus and treatment method according to the third embodiment of the present invention floats and separates a heavy liquid to which a coagulant is added as a solid-liquid separation means. Floating separation means 10 for obtaining sludge and treated water is used. Others are substantially the same as the crude oil-containing waste liquid treatment apparatus and treatment method according to the first embodiment, and thus the description thereof will be omitted.

Depending on the components contained in the heavy liquid after centrifugation, for example, when the proportion of oil in the heavy liquid is high, the specific gravity of the coagulated sludge generated by the addition of the coagulant is light and may float. According to the crude oil-containing waste liquid treatment apparatus and treatment method according to the third embodiment, by using the floating separation means 10 as the solid-liquid separation means 7, the aggregated sludge can be separated from the treated water more efficiently. It is possible to improve the quality of treated water.

As a specific example of the levitation separation means 10, various levitation separation means 10 using, for example, a pressure levitation method or a normal pressure levitation method can be used. To select whether to adopt the floating separation type device as shown in FIG. 3 or the sedimentation separation type device as shown in FIG. 2 as the solid-liquid separation means, a treatment test on a small scale is performed in advance. It is desirable to carry out and adopt a method suitable for the properties of the generated heavy liquid.

(Fourth Embodiment)
As shown in FIG. 4, the crude oil-containing waste liquid treatment apparatus and treatment method according to the fourth embodiment of the present invention include a heavy liquid storage tank 11 for storing heavy liquid obtained from the centrifuge 4, and a heavy liquid storage tank. A membrane filtration means 12 connected to 11 and obtained by membrane filtration of a heavy liquid obtained from a centrifuge 4 to obtain treated water and concentrated water is provided.

The processing apparatus shown in FIG. 4 is different from the processing apparatus shown in FIGS. 1 to 3, and the case where the coagulant is not added to the heavy liquid obtained from the centrifuge 4 will be described. Needless to say, the flocculant addition means 6 shown in FIGS. 1 to 3 may be further arranged if necessary.

The heavy liquid primarily stored in the heavy liquid storage tank 11 is supplied to the membrane filtration means 12 via the pump 13 and is separated into treated water and concentrated water. The concentrated water is circulated to the heavy liquid storage tank 11. As the separation membrane used in the membrane filtration means 12, any membrane having a pore size capable of separating oil and sludge remaining in the heavy liquid can be applied. Specifically, a microfiltration membrane or an ultrafiltration membrane can be applied. Membranes and the like are available. As the material of the separation film, a polymer film, a ceramic film, or the like can be used, and it is preferable to select the separation film according to the properties of the heavy liquid.

Ceramic films are preferable because they have high chemical resistance and durability, and even if oil, iron, sand, etc. are contained in the heavy liquid, the effect on the film material is small. Further, the ceramic film is also characterized in that a higher membrane permeation flux can be obtained as compared with the polymer film. On the other hand, the polymer film is advantageous in that the initial cost is lower than that of the ceramic film.

According to the crude oil-containing waste liquid treatment apparatus and treatment method according to the fourth embodiment, the heavy liquid stored in the heavy liquid storage tank 11 is supplied to the membrane filtration means 12, and the membrane filtration treatment is performed by the membrane filtration means 12. Since the concentrated liquid discharged from the membrane filtration means 12 is circulated to the heavy liquid storage tank 11, a cross flow can be formed on the membrane surface of the separation membrane perpendicular to the filtration direction. As a result, the accumulation of the blocking substance on the surface of the separation membrane can be suppressed. As a result, the membrane filtration treatment can be continued for a long period of time while suppressing the membrane contamination of the separation membrane included in the membrane filtration means 12.

Examples of the present invention are shown below together with comparative examples, but these examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

(Example 1)
In Example 1, an attempt was made to treat the hot water washing slop generated from the washing of the crude oil tank by using the treatment device as shown in FIG. The water content of the hot water washing slop used in the test was 26 to 35%, and the toluene insoluble content (hereinafter referred to as FS) was about 1%.

In the treatment test, the warm water wash slop was heated to about 50 ° C. Next, an emulsion breaker (trade name: Hakutoru E-523, manufactured by Hakuto Co., Ltd.) was added at a ratio of 20 mg / L, and then 150 L of hot water washing slop was added to a three-phase separation type centrifuge at a flow rate of 400 L / hr. Supplied. As a result, the water content of the obtained light liquid was 1.9%.

FIG. 5 shows an example of the relationship between the amount of emulsion breaker (E-523) added and the water content of the recovered oil. From FIG. 5, it was observed that the water content of the recovered oil tended to decrease as the addition rate of the emulsion breaker increased. The condition of the addition rate of 20 mg / L was about 1.9%, and the condition of the addition rate of 40 mg / L was about 1.1. Moisture content decreased to%.

From this result, it was shown that increasing the addition rate of the emulsion breaker 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. In addition, since the running cost increases as the amount added increases, the emulsion breaker addition rate is set to 20 mg / L in this example.

FIG. 6 shows an example of the relationship between the temperature of the crude oil-containing waste liquid and the water content of the recovered oil. Although the amount supplied to the centrifuge in FIG. 6 is different from that in Example 1, it was confirmed that the water content of the recovered oil decreases as the temperature of the crude oil-containing waste liquid increases. Although it depends on the flow rate, it was confirmed that the water content can be reduced to 2% or less by setting the temperature to 45 ° C or higher.

On the other hand, the amount of separated water (heavy liquid) obtained was about 25 L, which contained a black suspended solid, and was apparently a black suspension, which had a suspended solid concentration of 3400 mg / L. The chemical oxygen demand (COD) was 1800 mg / L. A flocculant (trade name: Hakutron B-733, manufactured by Hakuto Co., Ltd.) was added to this heavy liquid in a range of 25 to 400 mg / L, and a treatment test was carried out on a small scale. In the treatment test, a predetermined amount of a flocculant was added to 500 mL of a heavy liquid, the mixture was stirred for 6 minutes, the reaction solution was allowed to stand, and treated water (supernatant) was obtained by sedimentation separation.

The relationship between the COD in the treated water and the amount of the flocculant added is shown in FIG. In Example 1, the concentration of suspended solids was measured by filtering a glass filter paper having a pore size of 1 μm according to the method for measuring suspended solids of JISK0102. In addition, COD was measured according to the method for measuring oxygen consumption by potassium permanganate at 100 ° C. according to the method for measuring chemical oxygen demand of JIS K0102.

As shown in FIG. 7, the COD of the treated water gradually decreased by adding the flocculant, and increased again when the amount of addition exceeded a predetermined amount. When the amount of the flocculant added was 100 to 200 mg / L, the COD of the treated water was the lowest, and it decreased to about 150 mg / L.

FIG. 8 shows the relationship between the amount of coagulant added and the concentration of suspended solids in the treated water. The concentration of suspended solids (SS) in the treated water decreased to 8 mg / L at a coagulant addition rate of 100 mg / L. From these results, it was considered that an appropriate coagulant addition rate in Example 1 was 100 to 200 mg / L. The treated water after coagulation and precipitation had a slightly brownish and transparent appearance.

(Reference example 1)
The hot water wash slop was treated using the same treatment equipment as in Example 1 except that the flocculant was added with the emulsion breaker prior to the centrifugation step. First, the warm water wash slop was heated to about 50 ° C. Next, an emulsion breaker (trade name: Hakutoru E-523, manufactured by Hakuto Co., Ltd.) was added at a ratio of 20 mg / L, and a flocculant (trade name: Hakutron B-733, manufactured by Hakuto Co., Ltd.) was added at a ratio of 500 mg / L. It was supplied to a three-phase separation type centrifuge under the same conditions as in Example 1. The concentration of suspended solids in the obtained heavy liquid was 1000 mg / L, and the COD was 670 mg / L.

In Reference Example 1, a flocculant was added with an emulsion breaker prior to the centrifugation step. Although the predetermined effect of adding the flocculant can be obtained in Reference Example 1, the suspended solids concentration and COD of the obtained heavy liquid are higher than those in Example 1, and the treated water having better water quality can be obtained in Example 1. It was. Further, from the test results of Example 1 and Reference Example 1, it was confirmed that the method of adding the flocculant to the heavy liquid obtained after centrifugation is better than adding it before centrifugation. Was done.

In Example 1, since the flocculant was added at a ratio of 200 mg / L to about 25 L of the generated heavy liquid, the amount of the flocculant used was about 5 g, but in Reference Example 1, hot water washing supplied to the centrifuge was performed. Since the flocculant was added at a ratio of 500 mg / L to 150 L of the slop, the total amount of the flocculant used was about 75 g, and in Example 1, the amount of the flocculant used could be significantly reduced.

In Reference Example 1, a coagulant was added to the crude oil-containing waste liquid before oil-water separation. The coagulant is added to agglomerate sludge and the like in the crude oil-containing waste liquid, but in Reference Example 1, it is necessary to add a coagulant that acts on the total amount of sludge in the crude oil-containing waste liquid before centrifugation. Therefore, the required amount of coagulant was excessive. Further, the amount of coagulant added is generally determined by conducting a treatment test on a small scale, but it is difficult to determine an appropriate amount of coagulant added by the treatment test because the proportion of oil and sludge is high in the crude oil-containing waste liquid. Therefore, it is difficult to obtain good separated water quality.

In Example 1, since the flocculant is added to the separated water after centrifugation, most of the sludge and oil have already been removed. Therefore, the amount of the flocculant added may be smaller than that of Reference Example 1. In addition, since the treatment test can be easily carried out, the treatment can be performed with an appropriate amount of coagulant added, and good water quality can be obtained.

(Example 2)
In Example 2, a membrane filtration treatment test was carried out using the treatment apparatus shown in FIG. The same equipment as in Example 1 was used as the heating equipment and the centrifuge. On the other hand, in order to treat the separated water (heavy liquid) discharged from the centrifuge, a membrane filtration facility was provided instead of the coagulation sedimentation facility used in Example 1.

A heavy liquid storage tank and a pressure pump were arranged in front of the membrane filtration means, and the concentrated liquid obtained by the membrane filtration means was returned to the heavy liquid storage tank. In Example 2, the same hot water washing slop as in Example 1 was supplied to a three-phase separator type centrifuge at a flow rate of 400 L / hr. The obtained heavy liquid was stored in a heavy liquid storage tank and a membrane filtration test was carried out.

As the membrane filtration means, a ceramic membrane element made of silicon carbide (manufactured by LiqTech, diameter 25 mm, flow path diameter 3 mm × 25 flow paths, length 305 mm, nominal pore diameter: 0.08 μm) was used. This ceramic membrane element was used as a separation membrane for membrane filtration means, and heavy liquid was circulated and filtered at a circulation flow rate of 2 m / sec. The heavy liquid was operated while being heated to about 45 ° C. The quality of the treated water obtained by the membrane filtration treatment was that the suspended solids concentration was less than 1 mg / L and the COD was 100 mg / L, and it was confirmed that the heavy liquid could be treated by the membrane filtration treatment.

1 ... Mixing tank 2 ... Heating means 3 ... Emulsion breaker adding means 4 ... Centrifuge 5 ... Light liquid tank 6 ... Coagulant adding means 7 ... Solid-liquid separating means 9 ... Odor stack 10 ... Floating separation means 11 ... Heavy liquid Storage tank 12 ... Membrane filtration means 13 ... Pump 15 ... Circulation means

Claims (8)

Containing crude oil, a liquid waste containing emulsion, and heating step of heating to a temperature for increasing the fluidity of the oil lowers the stability of the emulsion,
An emulsion breaker addition step of adding an emulsion breaker to the heated waste liquid, and
A centrifugal separation step of centrifuging the waste liquid to which the emulsion breaker has been added and separating it into three components, a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge.
A coagulant addition step of adding a coagulant to the heavy liquid obtained in the centrifugation step and coagulating oil and sludge remaining in the heavy liquid.
A method for treating a crude oil-containing waste liquid, which comprises a solid-liquid separation step of floating and separating the heavy liquid to which the coagulant is added to obtain floating sludge and treated water . A heating step of heating the waste liquid containing crude oil and containing an emulsion to a temperature for increasing the fluidity of the crude oil and decreasing the stability of the emulsion.
An emulsion breaker addition step of adding an emulsion breaker containing an alkylphenol condensate to the heated waste liquid, and
A centrifugal separation step of centrifuging the waste liquid to which the emulsion breaker has been added and separating it into three components, a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge.
A coagulant addition step of adding a coagulant to the heavy liquid obtained in the centrifugation step to coagulate the oil and sludge remaining in the heavy liquid.
A solid-liquid separation step in which the heavy liquid to which the coagulant is added is settled in water under the action of gravity to obtain treated water and a solid substance.
Method of processing characteristics and be RuHara oil-containing waste liquid, further comprising a. The method for treating a crude oil-containing waste liquid according to claim 1 or 2, wherein the emulsion breaker is added to the waste liquid at 40 mg / L or less. The method for treating a crude oil-containing waste liquid according to any one of claims 1 to 3, wherein 100 to 200 mg / L of the flocculant is added to the heavy liquid. The method for treating a crude oil-containing waste liquid according to any one of claims 1 to 4 , wherein the temperature is 45 to 65 ° C. A heating means for introducing a waste liquid containing crude oil and containing an emulsion into a mixing tank and heating the waste liquid from the mixing tank to a temperature for increasing the fluidity of the crude oil and lowering the stability of the emulsion. When,
A circulation means for circulating the waste liquid between the mixing tank and the heating means,
An emulsion breaker adding means for adding an emulsion breaker to the heated waste liquid, and
A centrifuge that centrifuges the waste liquid to which the emulsion breaker has been added and separates it into three components: a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge.
A coagulant addition means for adding a coagulant to the heavy liquid obtained from the centrifuge and aggregating oil and sludge remaining in the heavy liquid.
A solid-liquid separation means for floating and separating the heavy liquid to which the flocculant is added to obtain floating sludge and treated water.
A crude oil-containing waste liquid treatment device characterized by being equipped with. Containing crude oil, by introducing a liquid waste containing emulsion to the mixing tank, the said effluent from the mixing tank, heating means for heating to a temperature for increasing the fluidity of the oil lowers the stability of the emulsion When,
A circulation means for circulating the waste liquid between the mixing tank and the heating means,
An emulsion breaker adding means for adding an emulsion breaker containing an alkylphenol condensate to the heated waste liquid, and
A centrifuge that centrifuges the waste liquid to which the emulsion breaker has been added and separates it into three components: a light liquid containing oil as a main component, a heavy liquid containing water as a main component, and sludge.
A coagulant addition means for adding a coagulant to the heavy liquid obtained from the centrifuge and aggregating oil and sludge remaining in the heavy liquid.
A crude oil-containing waste liquid treatment apparatus provided with a solid-liquid separation means for precipitating the heavy liquid to which the coagulant is added in water under the action of gravity to obtain treated water and a solid substance. .. The mixing tank, the centrifuge, and the solid-liquid separation means have a closed structure.
A line for guiding a gas containing a volatile component generated by the mixing tank, the centrifuge and the solid-liquid separating means to a safe environment is connected to the mixing tank, the centrifuge and the solid-liquid separating means. The crude oil-containing waste liquid treatment apparatus according to claim 6 or 7, wherein the crude oil-containing waste liquid is treated.