JPS61293507A - Separating method for oil from water in oil-containing salt solution - Google Patents

Abstract

PURPOSE:To remove oil component in an oil-contg. salt soln. having high salt concn. effectively by electrolyzing pure water or salt soln. contg. <=0.1% NaCl using Al as anode, and allowing to aggregate and adsorb to generated floc of Al(OH)3. CONSTITUTION:Pure water or salt soln. contg. <=0.1% NaCl is fed from a feeding port 6 of an electrolytic cell 1, and electrolyzed by passing DC between an Al anode 2 and a cathode 3. Floc of Al(OH)3 and gaseous H2 generated by the electrolysis are floated upward together with bubbles blown through a gas dispersing plate 5, and fed to a mixing tank 9 through a floc transfer pipe 7. The oil-contg. salt soln. having high salt concn. which is fed through an oil-contg. salt soln. feed pipe 15 is stirred uniformly by the floc and the bubbles blown through the gas dispersing plate 11 and the oil is aggregated and adsorbed to the floc. Floated floc is gathered by a scraper 12 and discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for separating and removing oil from oil-containing salt water, particularly from salt water containing oil emulsified in salt water, by aluminum electrolysis treatment.

[Conventional technology]

Methods for separating and removing oil from oil-containing wastewater include gravity separation, chemical coagulation separation, adsorption or filtration separation, and electrolytic separation. In the case of wastewater containing emulsified oil, electrolytic separation methods are employed.

One of these electrolytic separation methods is, for example, Japanese Patent Publication No. 53-298
As described in Japanese Patent No. 55, there is an electrolytic separation method using aluminum as an anode.

In this electrolytic separation method using aluminum as an anode, an aluminum anode and an iron cathode are installed in an electrolytic tank containing oil-containing wastewater, and the aluminum hydroxide flocs generated at the anode are The oil droplets are coagulated and adsorbed and separated by flotation.

[Problem that the invention seeks to solve]

However, this electrolytic separation method using aluminum as an anode,
In other words, the aluminum electrolytic separation method is sufficiently effective in the case of oil-containing wastewater from general factories that does not contain sodium chloride, but water containing sodium chloride, that is, salt water, for example, in bilges that collect at the bottom of the engine room of ships. It has been confirmed that sufficient separation effects cannot be achieved in the case of wastewater from seafood processing plants (mixtures of seawater, fresh water, fuel oil, lubricating oil, etc.) or wastewater (mixtures of seawater, fresh water, fish oil, etc.). .

That is, Table 1 shows the results of measuring the amount of aluminum hydroxide produced at the anode when the concentration of sodium chloride relative to water was changed in electrolysis using aluminum as the anode, and Table 2 shows This figure shows the results of an experiment in which oil-containing brine was separated using the conventional aluminum electrolytic separation method. In Table 2, the oil-containing brine was obtained by stirring a mixture of distilled water, sodium chloride, A heavy oil, and a surfactant for about 1 minute using a household mixer to emulsify A heavy oil.

(Margin below) Table 1 Table 2 As shown above, in the aluminum electrolytic separation method, when the concentration of IJum exceeds 0.3% (3000 ppm), the oil content is A phenomenon was observed in which the separation effect was extremely reduced. The reason for this is that when the concentration of sodium chloride in oil-containing brine increases, an oxide film is formed on the surface of the aluminum anode, making the aluminum anode non-dissolvable and making it difficult to produce aluminum hydroxide. It is assumed that there is.

The present invention provides a method in which this aluminum electrolytic separation method can be applied to oil-containing brine with a high concentration of sodium chloride as described above.

Means for Solving Problem C] Therefore, based on the results of the above-mentioned experiments, the present invention provides a solution by electrolyzing fresh water or salt water with a sodium chloride concentration of 0.1% or less in an electrolytic cell using aluminum as an anode.
Aluminum hydroxide flocs are generated, and the flocs are transferred to a mixing tank where they are mixed with oil-containing brine with a high concentration of sodium chloride to be separated. Through this mixing, the oil content in the oil-containing brine is removed from the They decided to coagulate and adsorb it on Flo-Tsuku.

[Action/effect of the invention]

In this way, in an electrolytic cell using aluminum as an anode, fresh water or sodium chloride concentration of 0. Since this method electrolyzes 1% or less salt water, a large amount of aluminum hydroxide flocs can be produced regardless of the sodium chloride concentration in the oil-containing salt water to be separated.

Therefore, according to the present invention, the oil contained in salt water with a high sodium chloride concentration, which could not be separated using the conventional aluminum electrolytic separation method, can be removed from fresh water or with a sodium chloride concentration of 0.1.
The aluminum hydroxide flocs produced in large quantities in an electrolytic cell that electrolyzes salt water of less than 10% coagulates and adsorbs and floats to the surface, making it possible to perform highly efficient and precise oil-water separation treatment.

Moreover, the amount of flocs produced in an electrolytic cell that electrolyzes fresh water or salt water with a sodium chloride concentration of 0.1% or less is
In addition to being stable regardless of the concentration of 1-lium chloride in the oil-containing brine to be separated, there is little dirt on the surfaces of both electrodes in the electrolytic cell, so the concentration of sodium chloride can be reduced significantly, as in the bilge of a ship. This has the effect of maintaining a stable oil-water separation process over a long period of time even when the oil-water separation temperature fluctuates.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. An anode 2 made of aluminum cuttings or waste aluminum cans filled in the direction of the lines is immersed in an electrolytic cell 1, and the inner peripheral surface of the anode 2 is filled with ferrite. A cathode 3 made of aluminum is provided, and both electrodes 2.
3 is applied with a DC voltage rectified by a DC rectifier 4, and the bottom of the electrolytic cell 1 is provided with an air diffuser plate 5 for aeration and a fresh water supply port 6; is equipped with a pipe 7 for transferring flocs.

The coagulation adsorption device 8 is composed of a mixing tank 9 and a separation tank 10. Inside the mixing tank 9, there is a diffuser plate 11 for aeration at the bottom and an endless belt type scraper 12 for scum removal at the top. The mixing tank 9 is connected to the adjacent separation tank 10 across the cascade weir 13, and one end of the mixing tank 9 is connected to a supply pipe 15 with a pump 14 for oil-containing brine to be separated. , and the floc transfer pipe 7 are visible.

Inside the separation tank lo, there is a mesh 16 for filtering and removing flocs, and an air diffuser plate 17 for backwashing the mesh 16.
Furthermore, a scum discharge port 1 is provided at the upper part of the separation tank 1o.
8, and a treated water outlet 19 is provided at the bottom.

Note that 20 is a compressor for sending compressed air to each of the air diffuser plates 5, 11, and 17.

Oil-containing brine to be separated is supplied to supply pipe 1 with pump 14.
5 into the mixing tank 9.

On the other hand, fresh water (or
Electrolysis is performed by supplying salt water with a sodium chloride concentration of 0.1% or less. Due to this electrolysis, flocs of aluminum hydroxide are generated at the anode 2 and hydrogen gas is generated at the cathode 3. These flocs and hydrogen gas float to the bottom of the electrolytic cell 1 together with bubbles blown from the air diffuser plate 5, and then float to the floc transfer pipe 7 by the action of the air lift pump.
The water is supplied into the mixing tank 9 through the mixing tank 9.

Note that the purpose of blowing bubbles into the bottom of the electrolytic cell 1 from the diffuser plate 5 is not limited to transferring the flocs and hydrogen gas into the mixing tank 9 as described above, but also because of the agitation effect accompanying the blowing of bubbles. This prevents concentration polarization of the electrolyte near both electrodes 2.3 and the formation of an oxide film on the electrode surface, and also cleans the electrode surface with air bubbles to prevent scale and oil droplets from adhering to the electrode surface. It's for a reason.

The oil-containing brine and flocs thus supplied into the mixing tank 9 are uniformly stirred and mixed by the air bubbles blown into the bottom of the mixing tank 9 from the air diffuser plate 11, and the minute oil droplets in the oil-containing brine are , it is coagulated and adsorbed by the flocs, becomes coarse, and floats to the surface of the water along with air bubbles.

The flocs or scum containing oil droplets that have surfaced on the water surface are
After being scraped up by the scraper 12, it is discharged to the outside of the mixing tank 9.

The salt water in the mixing tank 9 passes through the cascade weir 13 with the remaining flocs and enters the adjacent separation tank 10, and after the remaining flocs are filtered and separated by the mesh 16, it is discharged as purified water from the treated water outlet 19. Sent out.

Further, the flocs collected on the mesh 16 are backwashed by air intermittently ejected from the air diffuser plate 17 and are discharged from the scum discharge port 18 at the top.

[Brief explanation of drawings]

The drawings are diagrams showing embodiments of the invention. 1... Electrolytic cell, 2... Anode, 3... Cathode, 4...
・DC rectifier, 7...Flock transfer pipe 7.9・
...Mixing tank, 1o...Separation tank, 15...Oil-containing salt water supply piping, 5,11.17...Diffuser plate.

Claims (1)

[Claims] (1) Oil-containing brine from which oil should be separated is treated with fresh water or 0.0% sodium chloride in an electrolytic cell with an aluminum anode.
An oil-water separation method for oil-containing salt water, which comprises supplying and mixing flocs of aluminum hydroxide generated on an aluminum anode by electrolyzing salt water of 1% or less, and coagulating and adsorbing the oil in the oil-containing brine to the flocs. .