WO2015156386A1

WO2015156386A1 - Oil/water separation method for water including emulsified oil

Info

Publication number: WO2015156386A1
Application number: PCT/JP2015/061212
Authority: WO
Inventors: 一三栗木
Original assignee: 一三栗木
Priority date: 2014-04-12
Filing date: 2015-04-10
Publication date: 2015-10-15
Also published as: JP2017140545A

Abstract

The present invention addresses the issue of providing an effective treatment method for water including emulsified oil, such as palm oil mill effluent (POME) generated as organic wastewater from a palm oil plant or petroleum-associated water generated at an oil drilling site. This oil/water separation method for water including emulsified oil, as a solution to said issue, circulates the water including the emulsified oil through a microbubble generation device.

Description

Oil-water separation method for water containing emulsified oil

The present invention relates to an oil-water separation method for water containing emulsified oil, such as POME (Palm Oil Mill Effect: palm oil waste liquid) generated as organic wastewater from a palm oil factory, and oil-associated water generated at an oil mining site. .

パーム Palm oil collected from oil palm is a vegetable oil used as a raw material for various products including food and cosmetics. The two major production areas are Malaysia and Indonesia, and palm oil factories in these countries produce large amounts of palm oil every day. Palm oil is produced by squeezing the fruit of oil palm. In the process, POME which is water containing palm oil is generated as organic waste water. POME contains palm oil as an emulsified oil and is difficult to dispose of. Therefore, at present, POME generated in large quantities from a palm oil factory is returned to the natural environment after being left in a pond for several months. However, such treatment methods make the pond oxygen-free and generate a large amount of methane gas, which is one of the main causes of global warming. As a result, palm oil contained in POME is recovered. It is not discarded. Regarding the POME treatment method, for example, in Patent Document 1, POME is drained after sufficiently reducing BOD (Biological Oxygen Demand) component and SS (Suspended Solid) component. However, a processing method capable of recovering palm oil contained in POME is desired.

Also, the oil-associated water generated at the oil mining site is water containing emulsified oil and is difficult to dispose like POME, and therefore an effective treatment method is required.

JP 2011-83745 A

Therefore, an object of the present invention is to provide an effective treatment method for water containing an emulsified oil such as POME or petroleum-associated water.

As a result of intensive studies in view of the above points, the present inventor found that when water containing an emulsified oil such as POME or oil-associated water was circulated through the microbubble generator, the water containing the emulsified oil was gradually added. It was found to separate into oil and water.

The oil-water separation method for water containing the emulsified oil of the present invention based on the above knowledge is based on circulating the water containing the emulsified oil to the microbubble generator as described in claim 1. is there.
The method according to claim 2 is the method according to claim 1, wherein the water containing the emulsified oil is POME or petroleum-associated water.

According to the present invention, water containing emulsified oil can be separated into oil and water without adding an adsorbent or a flocculant, and the oil can be recovered and separated from the oil. The used water can be reused and drained. Therefore, it is possible to effectively perform treatments such as POME and oil-associated water, which have been difficult to dispose of until now.

It is a conceptual diagram which the nano bubble has adhered to the oil drop in water. It is a graph which shows the microbubble generation | occurrence | production performance of the microbubble generator used in Example 1 (graph which shows bubble distribution of the microbubble generated from distilled water). It is a photograph which shows the mode in the processing tank immediately after starting the circulation to the microbubble generator in POME in Example 1 (a content is POME). It is the photograph which shows the mode in the processing tank about 30 minutes after starting the circulation to the microbubble generator of POME (the content changes from POME to water and the foam formed on the surface. ing).

The oil-water separation method for water containing emulsified oil according to the present invention is based on circulating water containing emulsified oil to a microbubble generator.

The water containing the emulsified oil that is the water to be treated in the present invention is, for example, water in which oil droplets having a particle size of 0.1 to 500 μm are dispersed in an emulsified state. Examples include POME generated as organic waste water and oil-associated water generated at an oil mining site.

The water containing the emulsified oil that is the water to be treated in the present invention may be POME, petroleum-accompanying water itself, etc., or water containing microbubbles may be added, Microbubbles may be generated. Water containing emulsified oil added with water containing microbubbles, for example, water containing microbubbles prepared by sending tap water or distilled water to a microbubble generator into water containing emulsified oil. It can be obtained by adding. The water containing the emulsified oil in which microbubbles are generated in the water can be prepared, for example, by feeding water containing the emulsified oil into a microbubble generator. The mechanism of separating water containing the emulsified oil into oil and water by circulating water containing the emulsified oil through the microbubble generator is as follows.

In the oil-water separation method for water containing emulsified oil of the present invention, the water itself containing the emulsified oil is added to the microbubbles generated in the water by sending the water itself containing the emulsified oil to the microbubble generator, or water containing the emulsified oil. The microbubbles contained in the water or the microbubbles generated in the water containing the emulsified oil are, for example, bubbles having a particle diameter of 1 to 100 μm. In the present invention, the expected effect of microbubbles is that they are integrated with oil droplets that are dispersed in water in an emulsified state, thereby making the oil droplets float by reducing the total specific gravity more than water, and as a result And to separate the water. Since the oil droplets have a hydrophobic property, they have a characteristic that the situation can be perpetuated when in contact with gas. However, oil droplets and microbubbles present in water are charged and charged with the same sign although they are of different degrees. In addition to the electrostatic repulsive force acting between them. Many of the microbubbles shrink while dissolving the gas contained in the water to become nanobubbles with a particle size of less than 1 μm (typically 200 to 700 nm). not many. Therefore, adding water containing microbubbles to water containing emulsified oil, or generating microbubbles in water containing emulsified oil, it is not possible to integrate oil droplets and microbubbles. It is difficult, and as a result, it is also difficult to separate oil and water.
Based on the above points, in the present invention, water containing emulsified oil is circulated through the microbubble generator. As described above, microbubbles have the property of shrinking into nanobubbles while dissolving the gas contained therein in water. Therefore, when microbubbles are present in water containing emulsified oil, most of the microbubbles shrink without contact with the oil droplets due to the electrostatic repulsive force acting between them. become. Microbubbles and nanobubbles have the effect of concentrating charges existing near the surface, but when microbubbles are reduced to nanobubbles, the degree of charge concentration increases, so the reduction rate is much slower than the reduction rate of microbubbles. As a result, the nanobubbles are temporarily stabilized and float in the water at approximately the same size for several minutes (typically 1 to 10 minutes). Even under such circumstances, since the nanobubbles are charged, the electrostatic repulsive force acts on the oil droplets unchanged. However, since nanobubbles are very small, a directional bias occurs in water molecules that collide with the bubble surface as a result of thermal molecular motion, and a so-called Brownian motion is recognized in the nanobubbles. As a result, when a force that moves in the direction of the oil droplet by the collision of water molecules is applied to the nanobubble located in the vicinity of the oil droplet, the nanobubble exceeds the electrostatic repulsive force that acts between the oil droplet and the oil. Contact with drops. Once the nanobubbles come into contact with the oil droplets, they both integrate because they have the same hydrophobic properties. Under a general situation, it appears that small nanobubbles are attached to the surface of relatively large oil droplets (see FIG. 1). However, since the size of the nanobubble is relatively smaller than the size of the oil droplet, even if a certain number of nanobubbles adhere to the surface of the oil droplet, the effect of floating the oil droplet is small. Therefore, by sending water containing oil droplets with nanobubbles attached to the surface to the microbubble generator, the nanobubbles attached to the surface of the oil droplets grow into microbubbles as nuclei, thereby floating the oil droplets. It is a gist of the present invention to enhance the effect of the above.
That is, according to the present invention, the water containing the emulsified oil is circulated through the microbubble generator, so that there are oil droplets with nanobubbles attached to the surface, and the water adheres to the surface of the oil droplets. Nanobubbles grow into microbubbles and float up oil droplets, and new microbubbles are generated. After shrinking into nanobubbles, they adhere to the surface of oildrops, and nanobubbles attached to the surface of oildrops grow into microbubbles. As a result, the phenomenon of oil droplets rising one after another is caused, and as a result, oil and water are effectively separated. It should be noted that the time for one cycle of circulation of the water containing the emulsified oil to the microbubble generator is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes. If the time for one cycle is too short, there is a possibility that a sufficient number of nanobubbles cannot adhere to the surface of the oil droplet because the microbubbles cannot be reduced to nanobubbles. On the other hand, if the time for one cycle is too long, the microbubbles become nanobubbles. There is a risk of disappearing.

The microbubble generator used in the oil-water separation method for water containing the emulsified oil of the present invention is not particularly limited as long as it is a device that can generate microbubbles in water. It may be a pressure melting type device or a two-phase flow swirl type device. However, the microbubble generator used in the present invention is a microbubble that uses nanobubbles attached to the surface of oil droplets as a nucleus without applying strong physical stress to the oil droplets that have nanobubbles attached to the surface that has been present in water. It is desirable that the apparatus can efficiently grow into bubbles and can generate new microbubbles efficiently. In view of the above points, the microbubble generator proposed by the present inventor in Japanese Patent No. 3836497, specifically, “a gas supply for supplying a gas to a fluid in a flow path of a transfer pipe for transferring the fluid” Part, a blade that guides the fluid in a spiral shape, and a surface of one or a plurality of plate-like members that are disposed downstream of the gas supply unit and the blade and disposed in the flow path, And a partition forming section in which a plurality of divided flow paths are formed to rectify the fluid that spirally guides and swirls with the blades, and passes through the gas supply unit and the blades. In the present invention, it is preferable that the ion bubble generating apparatus configured so that the gas contained in the swirling fluid is refined by passing through the partition forming portion and becomes an ion bubble having a positive or negative charge ”. Can be adopted. According to the microbubble generator proposed by the present inventor, since no strong physical stress is applied to the oil droplets with nanobubbles attached to the surface in the device, the nanobubbles attached to the surface of the oil droplets are nucleated. As described above, the microbubbles can be efficiently grown and new microbubbles can be efficiently generated. In this device, the pressure inside the device is increased to about 3 to 5 atm, and the gas taken in from the outside is dissolved in water by the action of vortex, so that the gas is supersaturated in water immediately after being released from the nozzle. include. Gas molecules present in water under supersaturated conditions tend to return to stable saturation conditions by forming a gas phase. Therefore, when an oil droplet with nanobubbles attached to its surface is exposed to such an environment, supersaturated gas molecules contained in the surrounding water pass through the interface of the nanobubbles attached to the surface of the oil droplet. Jump into the inside. As a result, the nanobubbles adhering to the surface of the oil droplets grow rapidly, especially when the release from the nozzle is performed after a pressure of about 4 atmospheres (3.5 to 4.5 atmospheres) is applied. Since the amount of gas molecules jumping into the inside of the nanobubble is very large, the nanobubble grows into a microbubble within a short time within 1 second, and the effect of floating the oil droplet is enhanced. In addition, nanobubbles adhering to the surface of the oil droplets are temporarily stabilized, and the charge concentration is suppressed, so that they become uniform with the charge of the oil droplets and adhere to the surface of the oil droplets The coalescence of nanobubbles also occurs. The larger the bubble, the smaller the rise in internal pressure, so the gas molecules at the gas-liquid interface move from water into the bubbles created by the coalescence of nanobubbles, and eventually, typically the particle size Bubbles larger than 100-200 μm microbubbles are integrated with oil droplets, thereby producing very large buoyancy. In addition, even in such a situation, since the integrated oil droplets and microbubbles maintain the hydrophobic nature, they are rapidly lifted upward and finally rise to the water surface. Normally, when a microbubble rises to the surface of the water, the pressurized gas inside the microbubble is released into the gas phase and collapses. However, microbubbles integrated with oil droplets will not collapse even if they rise to the surface of the water, and will repeat coalescence with microbubbles integrated with oil droplets rising one after another from the water or bubbles larger than microbubbles. Therefore, it comes to exist as a very big bubble and forms foam on the water surface. In addition, since the oil droplets also repeat coalescence, the foam is stabilized by the oil derived from the oil droplets. As a result, foam accumulates on the water surface one after another, and the concentration of oil droplets proceeds. The foam that grows in this manner drives the moisture contained in the foam interface downward due to the action of gravity, so that the ratio of water contained in the foam decreases and the ratio of oil increases. The microbubble generator proposed by the present inventor in Japanese Patent No. 3836497 is suitable for causing such a series of phenomena.

For example, the processing tank and the microbubble generator are connected by a circuit, and the water containing the emulsified oil in the processing tank is circulated to the microbubble generator, so that the contents of the processing tank gradually become on the water and its surface. It turns into a foam containing the oil formed. After the microbubble generator is operated for a predetermined time, for example, 10 minutes to 24 hours, the foam containing oil can be recovered by scraping with a scraper. Also, the water separated from the oil can be reused or drained. While circulating water containing emulsified oil in the treatment tank to the microbubble generator, water containing new emulsified oil is added to the system, or water separated from the oil is discharged from the system. You may do it.

In the present invention, the gas taken into the microbubble generator from the outside is not particularly limited. For example, the gas may be air, but water containing the emulsified oil to be treated is oxidized. If it is not desired, the gas taken into the microbubble generator from the outside is desirably an inert gas such as nitrogen or argon.

Further, in the oil-water separation method of water containing emulsified oil of the present invention, an adsorbent or a flocculant may be added to the water containing the emulsified oil to be treated, but it is separated from water. It is desirable not to add such an additive when using the obtained oil as a raw material for foods and cosmetics.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not construed as being limited to the following description.

Example 1:
A 35L treatment tank and a microbubble generator proposed by the inventor in Japanese Patent No. 3836497 (pump drive amount: 40L, generating microbubbles having a bubble distribution shown in FIG. 2 from distilled water by operation for about 5 minutes. Can be connected with a circuit, 20 L POME obtained from a palm oil factory in Indonesia as treatment target water was placed in a treatment tank and circulated in a microbubble generator (circulation cycle time: approx. 30 seconds). FIG. 3 shows a state in the processing tank immediately after the start of circulation, and FIG. 4 shows a state in the processing tank about 30 minutes after the start of the circulation. As apparent from FIGS. 3 and 4, by circulating POME to the microbubble generator, POME in the treatment tank changed to water and foam formed on the surface thereof. When the oil content of the foam formed on the surface of the POME oil and the water was measured by a normal hexane extraction method, it was found that about 86% of the oil content of the POME could be recovered as a foam. During the circulation of POME in the treatment tank to the microbubble generator, the bubble distribution of the microbubbles contained in the water separated from the oil was examined, and the bubble distribution shown in FIG. 2 was almost the same. .

Example 2:
When the same treatment as in Example 1 was performed except that the oil-associated water generated at the oil mining site in the Middle East was used as the treatment target water, the oil-associated water could be separated into oil and water. In addition, the treatment speed could be improved by adding, for example, polyaluminum chloride (PAC) as a flocculant in advance to the petroleum-associated water as the treatment target water.

The present invention has industrial applicability in that it can provide an effective treatment method for water containing emulsified oil such as POME and oil-associated water.

Claims

An oil-water separation method for water containing emulsified oil by circulating water containing emulsified oil to a microbubble generator.
The method according to claim 1, wherein the water containing the emulsified oil is palm oil waste liquid (POME) or petroleum-associated water.