JP2006281123A - Oil/water separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a simple oil/water separator capable of demulsifying emulsified oil of fine diameter contained in bilge water or the like and emulsified by a surfactant without the need of adding chemicals for demulsifying from the outside, nor causing flock by demulsified oil, and capable of separating and recovering as normal oil droplets without causing flock of demulsified oil. <P>SOLUTION: The bilge water in a bilge tank 1 is guided into a parallel plate type separator 2, large oil droplets are made to float and are separated by passing the bilge water through gaps between parallel plates, thereafter the bilge water is led to a demulsifying tank 3, and Ca ions eluted from a packing material 3a such as gypsum is reacted with a surfactant in the bilge water to demulsify emulsified oil. Demulsified oil is led to a coagulation separator 4 and passed through a coalescer 4a having a layer of fibers of large diameters at the flow-in side and a layer of fibers of small diameters at the flow-out side, to coagulate extremely fine oil droplets into sizes easy to float up for floating separation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oil / water separator, and more particularly to an oil / water separator suitable for separating and recovering emulsified oil contained in bilge water generated in a ship.

  New regulations have been introduced since 2005 regarding the oil concentration when discharging bilge water in the ship. This regulation is implemented for the purpose of preventing marine pollution and further improving the environment, and requires that the concentration of oil containing emulsified oil be suppressed to 15 PPM or less by oil-water separation. Therefore, in particular, a technique for thoroughly removing emulsified oil (O / W emulsion) contained in bilge wastewater is required.

  Conventionally, as a method of oil-water separation, separation is performed by passing a liquid to be treated by combining a floating separation method that applies a difference in specific gravity or viscosity between water and oil of fine oil particles, or an element laminated with lipophilic fibers. The method was common.

  In the floating separation method, applying the characteristic that fine oil particles are attracted to each other, water to be treated is passed between multilayer parallel plates, and oil droplets adhering to the parallel plates grow greatly, and the parallel plates are lifted to the upper part. .

  Also, in the method of combining laminated elements, an element in which stainless steel wires and special fibers with heat and corrosion resistance are stacked in layers is used, and the characteristics of the lipophilic material are applied to the treated water that has passed through the special fiber layer. The fine oil particles are attached to the fiber, which is a lipophilic material, and is grown to a large extent, leaving the fiber to float upward.

  The actual oil / water separation process is a combination of the above two methods. FIG. 3 shows an example of a conventional oil / water separation process.

  In this example, bilge water in the bilge tank 1 is guided to the condensation separation tank 4 through the parallel plate type separation device 2, and the waste liquid that has passed through the condensation separation tank 4 is discharged to the outside.

  The parallel plate separation device 2 is a floating separation type separation device, in which bilge water passes through a gap between parallelly laminated plates 2a called parallel plates, and at that time, large oil droplets in the bilge water gather. The diameter further increases and floats and separates. As a result, oil droplets of about 50 to 60 microns can be captured.

  Then, when the small oil droplets pass through the coalescer 4a made of an accumulation layer such as a metal net or a glass fiber net in the condensation / separation tank 4, the oil droplets gather to increase the diameter, and the size becomes 5 to 10 microns. It floats and separates in the form of oil droplets.

  However, there are oil droplets (emulsified oil) emulsified in the bilge water so as to have a small diameter, and such a fine diameter emulsified oil cannot be completely separated only by the above process. The emulsified oil is an emulsion dispersed by a surfactant and is dispersed in water as oil droplets having a minute diameter of 1 micron or less. Therefore, in order to float and separate this, the oil droplets having a minute diameter are assembled, It is necessary to increase the diameter. The emulsified oil has a charge on the surface due to the ionization of the surfactant attached to the surface of the oil droplets, which causes the oil droplets to repel each other and disperse in water. It is oil droplets. In general, since an anionic surfactant is often used, the surface of the oil droplet is negative (minus).

  Therefore, it is conceivable to collect the oil droplets by neutralizing and demulsifying the charge on the surface of the oil droplets by some method.

  As a neutralization technique, a method of supplying a cation such as Ca 2+, Mg 2+, Al 3+ and reacting with an anion of a surfactant, or a method of neutralizing by making a strong alkali or strong acid atmosphere is known.

  And in the method of supplying a cation such as Ca 2+, Mg 2+, Al 3+ and reacting the surfactant with an anion, a method of adding a water-soluble compound solution that becomes an ion source of calcium, magnesium, and aluminum, as well as an ion source A method of adding a powder is generally used. However, the process of neutralization by these methods requires adjustment of the pH of the treated water before the addition of the chemical, a quantitative supply device of the chemical, and the adjustment of the treated water Ph. Further, in this process, after the reaction, the oil droplet becomes a floc, and the post-treatment of the floc becomes very complicated. The method of adding a strong alkali or strong acid also has the same problem.

As a device that separates and removes emulsified oil from liquid mixed with fine emulsified oil emulsified by stirring with hydraulic hydraulic oil, etc., it consists of lipophilic fibers, and a plurality of fiber diameters and fiber densities are changed in stages There has also been proposed an emulsified oil separation device that uses a coalescer (separator) and continuously flows the liquid to be treated to gradually increase the size of oil particles mixed in an emulsified state and separate them (for example, patents). Reference 1)), which separates and removes the emulsified emulsified oil by stirring, and the oil droplets have electric charges on the surface due to emulsification by a surfactant like emulsified oil in bilge water. It is difficult to separate and remove the emulsified oil in a state where the oil droplets are repelled.
JP-A-8-309102

  As described above, in order to collect oil droplets of fine emulsified oil in bilge water and increase the diameter to float and separate, it is necessary to neutralize and demulsify the charge on the surface of the oil droplets. However, in the conventional demulsification method using neutralization technology, it is necessary to perform pH adjustment of treated water before chemical addition, chemical supply device, Ph adjustment of treated water, complicated treatment of generated floc, etc. It had to be a complicated process.

  The present invention is capable of demulsifying a fine-diameter emulsified oil emulsified with a surfactant contained in a liquid to be treated such as bilge water without the need for chemical addition for external demulsification. It is an object of the present invention to realize a simple oil-water separator that can separate and recover the emulsified oil as normal oil droplets without becoming a floc.

  The oil-water separator of the present invention is an oil-water separator that demulsifies and aggregates the emulsified oil emulsified with the surfactant contained in the liquid to be treated, and floats and separates it. The oil-water separator does not require an external chemical injection device. A demulsifying apparatus using chemicals and a coagulation / separation apparatus including a single coalescer that floats and separates oil droplets that have been demulsified after passing through the demulsifying apparatus are provided.

  This oil / water separator has a simple structure consisting of a demulsifier and a coagulator / separator, and a fine-diameter emulsified oil emulsified by the surface activity contained in the liquid to be treated such as bilge water is externally applied to the demulsifier. It is possible to demulsify without adding chemicals for the demulsification, and to separate and recover the demulsified oil without causing flocs by floating and separating with a coagulation separator.

  Solid chemicals used in the demulsifying device are one kind of inorganic substances that elute divalent cations such as gypsum (calcium sulfate), calcium hydroxide, Portland cement, alumina cement, magnesium hydroxide, or a mixture thereof. The mold is molded into a predetermined shape and size, and the filling amount is set so that the amount of cations necessary for demulsification is continuously supplied during the period of use, and the demulsification apparatus is filled. It is good.

  In particular, since gypsum exhibits a slow solubility in water, it is possible to continuously supply a cation in an amount necessary for demulsification. Further, the aqueous solution is neutral, and the use of gypsum eliminates the need for neutralization treatment of the treatment liquid, thereby simplifying the apparatus.

  Even when gypsum is used, not only gypsum alone but also a combination of one or more of calcium hydroxide, Portland cement, alumina cement, and magnesium hydroxide is used as necessary. Thereby, the elution ion amount and elution rate can be controlled.

  Needless to say, when combined, calcium hydroxide, Portland cement, alumina cement, and magnesium hydroxide are strong alkalis, so that the pH must be within the allowable range of wastewater regulations.

  When gypsum is combined with calcium hydroxide, Portland cement, alumina cement, and magnesium hydroxide, the ratio of materials other than gypsum is 1.5 or less, preferably 1.0 or less with respect to gypsum 1. Above 1.5, the pH becomes high and the treated water must be neutralized and discharged.

  The size of the gypsum or the mixture is, for example, a spherical one having a diameter of 5 to 100 mm, preferably 10 to 50 mm, and a rectangular or rectangular solid having a diagonal length of 6 to 30 mm, preferably 9 to 28 mm, a cylinder, In the truncated cone shape, the square root of the sum of the square of the lower base radius and the square of the height is 10 to 140 mm, preferably 14 to 70 mm. In any shape, below the respective lower limit values described above, the water permeability of the packed bed made of gypsum or a mixture decreases and the pressure loss increases, and above the upper limit value, the gap between the fillers becomes large and contact with water occurs. It worsens and the reaction efficiency decreases.

  The ratio G / V of the amount of gypsum or mixture G (weight) to be charged to the processing amount V (weight / hour) is 3/40 to 3/4, preferably 1/10 to 5/10. When G / V is 3/40 or less, the ion elution amount necessary for the reaction cannot be achieved. On the other hand, if it is 3/4 or more, the amount of elution becomes excessive and the amount of ions in the wastewater increases, which is not preferable.

  Also, the coalescer shall be a non-woven fabric of glass fibers or metal fibers having a diameter of 0.03 to 0.45 mm, or a cloth made of spun fabrics that are woven in a cylindrical shape so as to have a predetermined thickness. In particular, it is preferable to combine the layers so that a layer made of fibers having a large diameter is formed on the inflow side of the liquid to be treated and a layer made of fibers having a small diameter is formed on the outflow side.

  A specific coalescer structure is, for example, a non-woven fabric or cloth made of a large diameter lipophilic fiber on the inner layer side is wound around a pipe having a plurality of holes, and the outer layer side has a very small diameter lipophilic fiber. It is assumed that the nonwoven fabric or cloth made of is wound several times.

  With this arrangement, oil droplets having large diameters can be gathered in order, and even oil droplets having a very small diameter after demulsification can be efficiently gathered.

  In this case, the gap formed between the fibers becomes smaller as the fiber diameter becomes smaller, and the smaller the gap, the more efficiently the oil droplets with smaller diameter are adsorbed. The oil droplets after demulsification are very small and cannot be efficiently adsorbed unless they are voids made of extremely small diameter fibers. Therefore, oil droplets after demulsification can be efficiently absorbed by setting the fiber diameter to a minimum diameter. Then, the adsorbed oil droplets gradually gather and grow into oil droplets with an easy floating surface. Therefore, in particular, the glass fiber or metal fiber used for the outer layer of the coalescer is either a nonwoven fabric using a very small diameter fiber having a diameter of 3 to 9 microns or a cloth made by spinning a very small diameter fiber into a woven fabric, or It is desirable to configure with a combination of them.

  And it is desirable that the coalescer is constituted by stacking (rolling) the cloth made of the nonwoven fabric or the woven fabric so as to form 2 to 6 layers, preferably 2 to 3 layers. If the number of layers is one, a sufficient coagulation effect cannot be obtained, and if the number of layers is seven or more, the pressure loss becomes high and the flow of treated water is hindered.

  In addition, it is preferable that a part of the drainage from the coalescer is returned to the demulsification tank, so that excess residual ions in the drainage can be reused.

  As described above, according to the present invention, by using a demulsification device that uses solid chemicals that does not require an external chemical injection device, it is not necessary to add chemicals for external demulsification by the chemical solution injection device. In addition, it is possible to demulsify the emulsified oil of fine diameter emulsified by the surface activity contained in the liquid to be treated such as bilge water, and the demulsified oil does not become floc and is separated as normal oil droplets. A simple oil-water separator that can be recovered can be realized.

  In particular, when gypsum is used as a solid, slowly soluble inorganic material used in a demulsifying device, since gypsum is neutral, pH adjustment before chemical solution injection and neutralization treatment after chemical treatment are unnecessary.

  In addition, demulsified ultra-small oil droplets can be collected by a coalescer, floated and separated, so that no floc is generated, so that the floc treatment is not necessary, and the recovered oil can be recycled as fuel. become.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram of an oil-water separator according to an embodiment of the present invention, and FIG. 2 is a schematic structural diagram of a coalescer in the oil-water separator.

  The oil-water separator of this embodiment performs oil-water separation of bilge water generated in a ship, for example, and the bilge water in the bilge tank 1 is first guided to the parallel plate type separator 2. Then, the bilge water passes through the gap between the parallel plates 2a in the parallel plate separation device 2, and at that time, large oil droplets in the bilge water gather and further increase in diameter and float and separate.

  The bilge water that has passed through the parallel plate separation device 2 is guided to the demulsification tank 3 (demulsification device). Then, Ca ions eluted from the filler 3a such as gypsum filled in the demulsification tank 3 react with the surfactant in the bilge water, and the effect of the surfactant disappears. As a result, the emulsified oil is demulsified. Is done.

  Then, the demulsified oil is guided to the agglomeration separation tank 4 and passes through the coalescer 4a, so that the oil droplets having a very small diameter are aggregated and floated and separated so as to float. 13 is discharged to the outside.

  The structure of the coalescer 4a is as shown in FIG. 2. A large-diameter glass or a non-woven fabric or cloth of metal fibers is wound as the inner layer 9 on the outer side of the perforated pipe 11, and a very small-diameter glass is formed as the outer layer 8 on the outer side. Or the nonwoven fabric or fiber of a metal fiber is wound. The treated water 12 containing the demulsified oil is introduced into the pipe 11, gathers when passing through the inner layer 9, and further passes through the outer layer 8, becomes larger in diameter, and floats and separates as floating oil 13. Discharged. In FIG. 2, the code | symbol 10 has shown the flow of the treated water.

  The treated water that has passed through the coagulation / separation tank 4 is subjected to final treatment by the filter 5, partly refluxed to the demulsification tank 3 through the reflux pipe 7, and the rest is discharged as waste liquid 6 to the outside.

  In addition, this oil-water separation device can be applied to wastewater treatment of general factories in addition to treatment of bilge water, and various embodiments are possible.

  The waste liquid (bilge water) containing 3000 ppm emulsified oil was processed by the oil-water separator of the above embodiment shown in FIGS. 1 and 2. The surfactant contained in the waste liquid is dodecylbenzene sulfonic acid soda (DBS), the content is 30 ppm, and the treatment amount is 1000 kg / hour.

  The demulsification tank 3 was filled with 200 kg of gypsum molded into a 15 × 15 × 15 mm cube. As the coalescer, a glass cloth made of a fiber having a diameter of 0.3 mm was wound in two layers, and a nonwoven fabric made of a very small diameter glass fiber having a diameter of 3 to 9 microns was wound on the outside in three layers.

  As a result of the treatment, the emulsified oil having a concentration of 3000 ppm decreased to a concentration of 3 ppm at the stage of the waste liquid 6 after passing through the filter 5.

It is a system configuration figure of an oil-water separator of an example of an embodiment of the invention. It is a schematic structure figure of the coalescer in the oil-water separator of an example of an embodiment of the invention. It is a system block diagram of the conventional oil-water separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bilge tank 2 Parallel plate type separation device 2a Parallel plate 3 Demulsification tank 3a: Filler (gypsum etc.)
4 Coagulation separation tank 4a Coalescer 5 Filter 6 Waste liquid 7 Reflux pipe 8 Outer layer (nonwoven fabric or cloth made of extremely small diameter fibers)
9 Inner layer (non-woven fabric or cloth made of large diameter fibers)
10 Liquid flow 11 Pipe 12 Treated water 13 Floating oil

Claims (4)

An oil-water separator that demulsifies, aggregates, and floats and separates emulsified oil emulsified with a surfactant contained in the liquid to be treated, and uses a solid chemical that does not require an external chemical injection device; and An oil / water separation device comprising a coagulation separation device composed of a single coalescer that floats and separates oil droplets that have been demulsified after passing through the demulsification device. The solid chemical used in the demulsifier is one kind of an inorganic substance that elutes a divalent cation such as gypsum, calcium hydroxide, Portland cement, alumina cement, magnesium hydroxide, or a mixture thereof. It is formed into a shape and size, and the filling amount is set so that the amount of cations necessary for demulsification is continuously supplied during the period of use, and the demulsification apparatus is filled. The oil-water separator according to claim 1. The coalescer is characterized in that a non-woven fabric of glass fibers or metal fibers having a diameter of 0.03 to 0.45 mm or a cloth made of a spun fabric is stacked in a cylindrical shape so as to have a predetermined thickness. The oil-water separator according to claim 1 or 2. The coalescer is a non-woven fabric of glass fibers or metal fibers having a diameter of 0.03 to 0.45 mm or a cloth made of spun fabric, and a layer made of fibers having a large diameter on the inflow side of the liquid to be treated. The oil-water separator according to claim 3, wherein the oil-water separator is formed so that a layer made of fibers having a small diameter is formed on the outflow side.

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