JPH09176659A - Method for purifying oil-containing sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process by which oil-containing sludge produced from, e.g. an oil refinery can be purified to form a product in a recyclable state. SOLUTION: This method comprises the step (I) of bringing oil-containing sludge S into contact with a solvent K to extract the oil component contained in the sludge with the solvent K and separating a product of contact into a solid phase R and an oil phase L and the step (II) of washing the separated soil phase R with water to transfer it to a water phase and separating a solid phase D from the water phase M.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning oil-containing sludge generated in an oil refinery or the like and discharging it in a reusable form.

[0002]

2. Description of the Related Art Crude oil tanks and the like of refineries are inspected once every seven years according to the Fire Service Law. At this time, the crude oil in the tank is drained to clean the inside, but as a result, a large amount of oil-containing sludge is discharged.
Its emissions reach, for example, about 5000 tons per year at refineries with a capacity of 200,000 barrels / day. At present, the oil-containing sludge is incinerated, but the cost is said to be 25,000 yen / ton to 30,000 yen / ton, which is a heavy burden on each refinery.

[0003]

As a disposal method other than incineration, dumping at sea or backfilling in the soil can be considered.
Since the oil-containing sludge contains a considerable amount of crude oil, environmental pollution is significant, and neither method can be carried out with the oil-containing sludge as it is. In addition, it is not preferable to incinerate the oil-containing sludge in the state of containing crude oil from the viewpoint of effective use of resources. However, a simple method for cleaning oil-impregnated sludge to effectively utilize resources while preventing environmental pollution has not been found yet. The present invention has been made to solve the above problems, and an object thereof is to provide a simple method for cleaning oily sludge and discharging it in a reusable form.

[0004]

[Means for Solving the Problems] The above-mentioned problems include an extraction step in which an oil-containing sludge is brought into contact with a solvent to extract an oil component contained in the sludge into the solvent, and then a solid phase and an oil phase are separated, and the extraction step. The problem can be solved by providing a method for cleaning oil-containing sludge, which has a water washing step of washing the solid phase separated in the step with water to transfer the residual oil content to the water phase and then separating the solid phase and the water phase.

The extraction in the above extraction step is performed at 50 ° C.
It is preferable to carry out at a temperature within the range of 100 ° C. The extraction in the above extraction step is preferably performed in the presence of a surfactant. The separation of the solid phase and the oil phase in the above extraction step is preferably performed by centrifugation. The washing with water in the washing step is preferably performed in the presence of a surfactant. The separation of the solid phase and the aqueous phase in the above washing step is preferably performed by centrifugation.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings by way of an embodiment. FIG. 1 shows an example of a cleaning device suitable for carrying out the present invention. In FIG. 1, this cleaning apparatus is roughly shown in the following: an extraction tank 10 for contacting an oil-containing sludge S with a solvent to extract the oil content contained in the sludge into the solvent, a solid phase R and an oil phase L for the mixture in the extraction tank 10. A first centrifuge 20 for separating into a solid phase R, a washing tank 30 for washing the separated solid phase R with water to transfer the residual oil to a water phase, and a mixture in the washing tank 30 for a solid phase D and a water phase M. And a second centrifuge 40 for separating into

An embodiment for carrying out the cleaning method of the present invention using the above cleaning apparatus will be described below. Extraction step (I): The oil-containing sludge discharged from the crude oil tank or the like is extracted as oil-containing sludge S from the line 1 by, for example, a belt conveyor after the contaminants such as bolts and iron rust are removed by a screen or an electromagnet in advance. Tank 1
0 is introduced. The extraction tank 10 includes a heating jacket 11 and a stirrer 12. Steam is introduced into the jacket 11 from a boiler (not shown) to heat the contents of the extraction tank 10.

A solvent K having a high flash point such as kerosene or light gas oil is supplied from the line 2 to the extraction tank 10 together with the oil-containing sludge S. In the extraction tank 10, the oil-containing sludge S and the solvent K are about 70 by the jacket 11.
The mixture is heated to 0 ° C. and mixed by stirring by the stirrer 12. As a result, the oil contained in the oil-containing sludge S is extracted by the solvent K, and the oily slurry Y composed of the solid phase and the oil phase is formed in the tank. The oily slurry Y is extracted from the bottom of the extraction tank 10 and sent from the line 3 to the first centrifuge 20 by a pressure feed pump or the like (not shown).

In the oily slurry Y supplied to the first centrifuge 20, most of the oil phase contained in the oily slurry Y is separated from the solid phase R by centrifugation, and the separated oil phase is discharged oil. Collected as L. The solid phase R of the centrifugally separated residue is taken out from the first centrifuge 20 while being wet with the oil phase, and sent to the next water washing step (II) via a line 4 such as a belt conveyor.

Washing step (II): The solid phase R is first introduced into the washing tank 30. The water washing tank 30 includes a heating jacket 31 and a stirrer 32. Jacket 31
Steam is introduced into the tank from a boiler (not shown) to heat the contents of the washing tank 30.

An aqueous solution of a surfactant is supplied to the washing tank 30 from the line 5. In the washing tank 30, the solid phase R and the aqueous surfactant solution are heated to about 70 ° C. by the jacket 11 and mixed by stirring by the stirrer 32. As a result, the residual oil adhering to the solid phase R is emulsified or suspended in the aqueous phase and transferred, and an aqueous slurry H composed of the solid phase and the oil-containing aqueous phase is formed in the tank.

The aqueous slurry H is extracted from the bottom of the water washing tank 30 and sent from the line 6 to the second centrifuge 40 by a pressure feed pump or the like (not shown). In this second centrifuge 40, the aqueous slurry H is centrifuged,
Most of the oil-containing aqueous phase contained in the aqueous slurry H is separated from the solid phase and recovered as oil-containing wastewater M.

The residue of the second centrifuge is rinsed with water in the basket 41 of the second centrifuge 40, and this rinse water is centrifuged and combined with the oil-containing wastewater M and rinsed. The solid phase is discharged as cleaning sludge D from the second centrifuge 40 via line 7.

In the above method for cleaning oil-containing sludge, the oil content of the obtained purified sludge D is removed, so that the amount of oil is significantly reduced from the original oil-containing sludge S.
In addition, since it does not substantially contain oil, the cost can be reduced even if it is incinerated, and it is possible to perform a process such as backfilling in the ground with or without biological treatment.

The discharged oil L discharged in the extraction step (I) is
Since the components are the oil content in the oil-containing sludge S and the solvent K such as kerosene or light gas oil, it can be returned to the oil refining process as a part of the raw material in an oil refinery or the like, and can be effectively used as fuel or the like. You can also

Oil-containing wastewater M discharged in the water washing step (II)
Is because oil is emulsified or suspended in water,
If oil / water is separated in a water treatment step (not shown), the oil phase can be combined with the discharged oil L and reused, and the water phase can be newly added with a surfactant to perform the washing step (II). It can be circulated in the line 5 as the aqueous surfactant solution used in step 1, or can be discharged as waste water through a normal water treatment process.

According to the above method for cleaning the oil-containing sludge S, in the extraction step (I), the oil-containing sludge S is brought into contact with the solvent K under heating, so that the oil contained in the sludge is extracted into the solvent, An oily slurry Y composed of a solid phase and an oil phase having a relatively low viscosity is formed. This allows centrifugal separation with good drainage, and improves the oil recovery rate in this step.

In the water washing step (II), the oil phase attached to the solid phase R in the previous step is preferably mixed with water containing a surfactant, so that the oil phase attached to the solid phase R becomes dispersed particles. Transfers to the aqueous phase and forms an aqueous slurry H. Therefore, if this aqueous slurry H is separated by centrifugation, the oil-containing wastewater M and the purified sludge D containing no oil can be recovered.

The oil-containing wastewater M can be demulsified by a known method even if the oil content is emulsified by the effect of the surfactant. After the emulsion is destroyed, the oil phase and the water phase can be easily separated due to the difference in specific gravity, so that both the oil phase and the water phase can be recovered and reused without waste.

Also, throughout the above-mentioned oil-containing sludge cleaning process, the only discharges are the discharged oil L, the oil-containing wastewater M, and the cleaning sludge D, all of which can be effectively utilized as described above. Therefore, not only is there no resource loss, but environmental pollution can be prevented. The equipment used in the above-mentioned cleaning process is generally used in petroleum refining plants and the like, and consumes less energy, so compared to conventional incineration methods, etc.
The treatment cost of oil-containing sludge is reduced.

In the extraction step (I) of the above embodiment,
Solvent K such as kerosene or light gas oil is used as the solvent. Kerosene or light gas oil can be easily and inexpensively obtained at refineries, and can well extract the oil contained in the oil-containing sludge S, and has relatively low volatility, and is recovered by centrifugation. It is a suitable solvent because the discharged oil L can be directly returned to the oil making process or the like. However, the solvent that can be used in the method of the present invention is not limited to this,
Petroleum fractions having other boiling points and aromatic hydrocarbons can also be used.

The mixing ratio of the solvent to the oil-containing sludge S includes the oil content of the oil-containing sludge S, the type of solvent, the extraction temperature,
It changes depending on the viscosity of the oily slurry Y suitable for stirring. Generally, 10 per 100 parts by weight of oil-containing sludge
It is preferable to set it within the range of 100 parts by weight to 100 parts by weight. However, 100 parts by weight or more of solvent may be used.

The suitable range for the extraction temperature in the extraction step (I) is determined by the type of solvent and the legal restrictions involved. Generally, the temperature is preferably in the range of 50 ° C to 100 ° C, more preferably 60 ° C to 70 ° C.
If the temperature is lower than 50 ° C, the oil adhered to the oil-containing sludge S is unlikely to swell, and it may take a long time for extraction. If the temperature exceeds 100 ° C, the volatilization loss of the solvent is increased and the legal regulation is strengthened. However, there are disadvantages such as increased bulk.

An oil-soluble surfactant may be added to this solvent as a penetrant or a swelling agent. These oil-soluble surfactants have the effect of permeating the solvent into the oil-containing sludge and swelling the fixed oil, and therefore can improve the extraction efficiency.

A centrifugal separator is preferably used for the separation of the solid phase and the oil phase in the above extraction step (I). The centrifuge used may be a batch type or a continuous type, and in the case of a batch type, may be a top discharge type or a bottom discharge type. A centrifuge is suitable as a device for separating the solid phase and the oil phase, but other separating devices such as an oil pressing device and a basket type oil removing device can also be used.

The washing in the above washing step (II) is
Although it can be carried out using only water, it is more preferably carried out in the presence of a surfactant. The surfactant is effective for dispersing the oil component adhering to the solid phase in water and preventing redeposition. The type of surfactant used is not particularly limited as long as it can effectively disperse the oil phase in water.
However, it is preferably biodegradable and phosphorus-free.
Suitable examples thereof include soap, higher alcohol-based surfactants, anionic surfactants such as α-olefinsulfonic acid-based surfactants, polyhydric alcohol fatty acid ester-based surfactants, polyoxyethylene-based surfactants. Agents, sorbitan polyoxyethylene-based surfactants, polyoxyethylene propylene-based surfactants, nonionic surfactants such as fatty acid alkylolamide-based surfactants, and the like.

The separation of the solid phase and the aqueous phase in the water washing step (II) is preferably performed by centrifugation. The centrifuge used may be a batch type or a continuous type, and in the case of a batch type, may be a top discharge type or a bottom discharge type.
A centrifuge is preferably used for the separation of the solid phase and the aqueous phase, but other separating devices such as an oil pressing device and a basket type draining device can also be used.

The cleaning apparatus shown in FIG. 1 has two mixing tanks 10,
Although 30 and two centrifugal separators 20 and 40 are used, it is not necessary to permanently install this device except for the case where oil-containing sludge is always generated, and it is a temporary diversion of the device of other process. Good. Further, the extraction tank 10 and the water washing tank 30, and the first centrifugal separator 20 and the second centrifugal separator 40 may be combined. In the case of the combined use, the solid phase R obtained in the extraction step (I) is temporarily stored until the entire amount of the oil-containing sludge S to be treated has been treated in the extraction step (I), and thereafter,
The stored solid phase R is preferably washed with water using the same mixing tank (10) and centrifuge (20).

[0029]

The method for cleaning oil-containing sludge of the present invention comprises:
An extraction step (I) for separating the solid phase and the oil phase after bringing the oil-containing sludge into contact with a solvent, and a washing step (II) for washing the separated solid phase with water and then separating the solid phase and the aqueous phase. Since it has, the purified sludge D discharged from the water washing step (II) has the oil content removed, and the amount is greatly reduced from the original oil-containing sludge. For example, the cost can be reduced even if it is incinerated. The possibility of environmental pollution can be mitigated by carrying out a treatment such as backfilling in the ground without or with biological treatment.

The oil component discharged in the extraction step (I) can be returned as a part of the raw material to, for example, the step of the refinery, or can be effectively used as fuel or the like. In the oil-containing wastewater discharged in the water washing step (II), the oil phase can be reused after the oil / water separation, and the water phase can be washed in the water washing step (I).
Since it can be reused as the washing water of I), environmental pollution is reduced and resource saving is effective.

The method for cleaning oil-containing sludge of the present invention uses a simple device that can be temporarily installed only during the period when oil-containing sludge is generated, and is used under conditions where energy consumption is low and safety is low. It has the advantage that it can be implemented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an oil-containing sludge cleaning device to which the present invention is applied.

[Explanation of symbols]

 1 …… Oil-containing sludge supply line 2 …… Solvent supply line 7 …… Cleaning sludge discharge line 10 …… Extraction tank 20 …… Centrifuge 30 …… Water washing tank 40 …… Centrifuge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Kondo 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation

Claims (6)

[Claims] 1. An extraction step in which an oil-containing sludge is brought into contact with a solvent to extract an oil component contained in the sludge into the solvent, and then a solid phase and an oil phase are separated, and the solid phase separated in this extraction step is washed with water. The method for cleaning oil-containing sludge, which comprises a step of rinsing the solid phase and the water phase after transferring the remaining oil component to the water phase. 2. The extraction in the above extraction step is performed at 50 ° C.
The method for cleaning oil-containing sludge according to claim 1, wherein the method is performed at a temperature in the range of -100 ° C. 3. The method for cleaning oil-containing sludge according to claim 1, wherein the extraction in the extraction step is performed in the presence of a surfactant. 4. The method for cleaning oil-containing sludge according to claim 1, wherein the separation of the solid phase and the oil phase in the extraction step is performed by centrifugation. 5. The method for cleaning oil-containing sludge according to claim 1, wherein the water washing in the water washing step is performed in the presence of a surfactant. 6. The method for cleaning oil-containing sludge according to claim 1, wherein the separation of the solid phase and the aqueous phase in the water washing step is performed by centrifugation.