JP2003190940A - Freeze-concentration and separation method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently obtain ice in which little amount of solvent is contained. <P>SOLUTION: Dissolved air in water having absorbed the solvent is removed by a degassing device 96 and the generation of air bubbles becoming a cause taking in the solvent when the water having absorbed the solvent is frozen by a freezer 21 is suppressed. Therefore, clean ice is obtained because air bubbles (the solvent is take in air bubbles) are not contained in ice frozen by the freezer 21. Separation efficiency can be enhanced by separating unfrozen concentrated water and ice. Further, the concentration of the solvent in the concentrated water separated from ice becomes high and concentrated water containing the solvent in a high concentration can be also used as a washing agent, fuel and a coating solution applied to a planographic printing plate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a freeze concentration separation method and a freeze concentration separation apparatus for separating ice containing no solvent and concentrated water containing a solvent.

[0002]

2. Description of the Related Art As shown in FIG. 5, the water used in a sprinkler type gas-liquid contactor 158 for absorbing VOC gas G discharged from a plant or the like into the atmosphere is treated in treatment towers 160, 16.
In 2, 164, the solvent concentration gradually increases due to contact with the gas. The water that has absorbed this solvent (hereinafter referred to as “solution”) is used as it is in the processing tanks 166, 168, 1
When it is refluxed to 70, the solvent concentration in the water in the entire treatment tank increases, and even if this solution is supplied to the treatment tower, the solvent cannot be continuously absorbed in a good state (solvent collection efficiency decreases. ).

Therefore, in order to maintain the solvent absorption efficiency, it is necessary to continuously supply fresh water W from the water conduit 172 to the treatment tank 170, and it is not possible to reduce the amount of makeup water.

In addition, how high the concentration of the solvent contained in the water W1 finally discharged from the drain pipe 174 of the treatment tank 166 of the sprinkler type gas-liquid contactor 158 and how to distill it and reuse it is determined. This is a major point in reducing running costs.

Therefore, the present applicant has proposed a gas-liquid contactor for separating a solution into ice and concentrated water containing solvent-containing water by a freeze concentration / separation device (Japanese Patent Application No. 2000-0747).
No. 83).

By using this gas-liquid contactor, the amount of make-up water can be reduced, the efficiency of solvent absorption can be maintained, and the concentration of the concentrated water finally discharged can be increased. However, in order to prevent the solvent from being contained in ice during freeze-concentration separation, some more work needs to be done.

That is, when the solution has a high concentration, if the cooling power is strengthened to form and grow ice crystals (ice particles) in a short time, ice taken in with the solvent is formed, so the cooling power is weakened for a long time. It is necessary to form and grow ice particles over time. However, if the freezing takes a long time, the concentration and separation efficiency of the solvent decreases, so that there is a demand for a technique for producing ice close to pure water in a short time.

[0008]

In consideration of the above facts, the present invention has an object to efficiently obtain ice containing as little solvent as possible.

[0009]

According to the first aspect of the present invention, there is provided a freeze-concentration separation method in which water having absorbed a solvent is frozen and separated into ice containing no solvent and concentrated water containing the solvent. A step of degassing the water that has absorbed the solvent, a step of freezing the water that has absorbed the degassed solvent with a freezing device to make ice, and a step of separating the ice and concentrated water containing the solvent. Is characterized by having.

In the above structure, the deaerator removes the dissolved air of the water that has absorbed the solvent, and suppresses the generation of bubbles that cause the solvent to be taken in when the water that has absorbed the solvent is frozen by the freezer. In this way, the water that has absorbed the solvent from which the dissolved air has been removed is frozen by the freezing device, the solvent does not freeze due to the difference in freezing point, and the water freezes to become ice and concentrated water. This ice is clean because no air bubbles (the air bubbles take in the solvent) are taken in. Then, the separation efficiency can be improved by separating the unfrozen concentrated water and the ice.

For this reason, the ice becomes close to pure water, and clean ice that does not contain much solvent can be melted and reused as water. For example, this melted water was supplied to the treatment tank of the exhaust gas recovery apparatus. In this case, the amount of fresh water supplied can be reduced.

Further, the concentration of the concentrated water solvent separated from the ice is high, and the concentrated water containing this high concentration solvent should be used as a cleaning agent, a fuel, and a coating liquid for coating lithographic printing plates. Will also be possible.

According to a second aspect of the present invention, in a freeze-concentration separation apparatus that freezes water that has absorbed a solvent and separates it into solvent-free ice and concentrated water that contains the solvent, A degassing device for degassing, a freezing device for freezing the water that has absorbed the degassed solvent, and a separation means for separating the ice and concentrated water containing the solvent, .

In the invention of the above structure, the deaerator removes the dissolved air of the water that has absorbed the solvent, and suppresses the generation of bubbles that cause the solvent to be taken in when the water that has absorbed the solvent is frozen by the freezer. To do. Therefore, almost no bubbles are taken into the ice made, and the ice becomes clean. The ice and unfrozen concentrated water are separated by a separating means and used for each purpose.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the freeze concentration / separation device 22 according to the present embodiment is incorporated in a gas / liquid contact device 10 for collecting exhaust gas in a processing line.

A replenishment pipe 24 is connected to the processing tank 14 of the gas-liquid contactor 10. The supply pipe 24 is provided with the pump 20, and by operating the pump 20, fresh water and recycle water described later are supplied from the storage tank 52 as treated water. Further, the water supply pipe 26 connected to the side wall of the treatment tank 14 is provided with a liquid feed pump 28, and water is pumped to the top of the treatment tower 12. Processing tower 12
The water that has been pumped to the top of the is sprinkled downward by the sprinkler 32.

A gas pipe 34 for taking in the volatile organic compound (VOC) gas discharged from the plant P is connected to the outer peripheral wall of one of the processing towers 12, and the VOC gas is continuously introduced into the processing tower 12. Will be sent.

The VOC gas taken from the gas pipe 34 into the treatment tower 12 is brought into contact with the water sprinkled by the sprinkler 32 while being subjected to batch treatment, and the concentration of the contained solvent is lowered. Then, the VOC gas that has come into contact with water is released to the atmosphere as a gas that does not affect the environment through the exhaust pipe 40 connected to the top of the processing tower 12.

A drain pipe 44 is connected to the processing tank 14. The drain pipe 44 is provided with an electromagnetic valve 78, and by operating this electromagnetic valve 78, the water in the processing tank 14 is drained to the intermediate tank 16.

The amount of water replenished from the replenishment pipe 24 to the treatment tank 14 and the amount of water drained from the treatment tank 14 are substantially the same, and the solvent can be recovered in batch processing without stopping the VOC gas. Has become.

On the other hand, the processing tank 14 is provided with a concentration sensor 80, which detects the solvent concentration of the processing tank 14 and sends a signal to the control unit 84. The control unit 84 is connected to the solenoid valve 78 and the pump 20, and switches the water in the processing tank 14 based on the detection result of the concentration sensor 80.

When the solvent concentration of the water in the processing tank 14 detected by the concentration sensor 80 exceeds a predetermined value, the pump 2
0 to activate fresh water through the supply pipe 24
4, the solenoid valve 78 is opened and the water having a high solvent concentration is drained from the drainage pipe 44 to replace the inside of the treatment tank 14 with fresh water.

By repeating the above operation,
The solvent in the VOC gas can be collected with high efficiency, and the solvent concentration of the drained water also becomes high. For this reason, the recovery efficiency of the next process is improved, and the equipment cost and running cost can be reduced.

As the gas-liquid contact method, a water spray method,
Filling schemes are known but not specified. Further, the number of gas-liquid contact units is not limited to one as in the present embodiment, and may be plural.

Further, the concentration of the volatile organic compound gas to be treated is preferably 100 ppm or more, and 1000 p
A remarkable effect appears when pm or more. Also, as the type of solvent gas, the difference in solubility parameter with water is 19 (cal.
cm ^-3 ) ^{1/2 or} less is preferable, and 15 (cal · cm ^-3 ).
Less than ^1/2 is more preferable (Solubility parameter: Hild
solubility parameter of ebrand).

Further, the solvent of the volatile organic compound is not limited to methyl ethyl ketone as long as it is water-soluble, and alcohols such as methanol, ethanol and n-propanol, polyhydric alcohols such as ethylene glycol, acetone and methyl are used. Ketones such as acetone and cyclohexane, and esters such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, and ethyl lactate may be used. further,
It can also be treated with mixed solvent gas.

The temperature of the replenished water is preferably 30 ° C. or lower, more preferably 15 ° C. or lower. The solvent concentration of the water to be replenished is preferably 2000 ppm or less. Further, in this example, water was used as the treated water for recovering the solvent in the VOC gas, but the same effect can be obtained with sludge water or activated sludge containing microorganisms.

Next, how to use the wastewater for one batch stored in the intermediate tank 16 as recycled water will be described.

The water that has absorbed the solvent in the intermediate tank 16 (hereinafter referred to as "solution") is supplied to the bottom of the deaerator 96 through the supply pipe 38 by driving the water supply pump 18 by the control unit 84. The solution sent to the degassing device 96 is sent to the front side of the degassing film 25.

The degassing film 25 is made of tetrafluoroethylene-
A sheet-like or bag-like thin film (size: 8000 x 350 mm) made of hexafluoropropylene copolymer is used, but as another degassing film, a fluororesin film can be used. An ethylene-hexafluoropropylene copolymer resin film, a tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin film, or a tetrafluoroethylene-ethylene copolymer resin film can be used. The thickness of the fluororesin film is preferably 100 μm or less, more preferably 50 μm or less.

A suction pipe 94 is connected to the back side of the degassing film 25. Vacuum pump 98 through the suction pipe 94
The back side of the degassing film 25 is sucked by the pressure of 30 ×
It is dropped to 1.33322 × 10 ² Pa. And
The solution in which the residual rate of dissolved oxygen is reduced by the degassing film 25 is sent to the freezing device 21 through the water supply pipe 100.

Regarding the pressure of the deaerator 96, 2
00 × 1.33322 × 10 ² Pa or less is preferable and 3
It is more preferably 0 × 1.33322 × 10 ² Pa or less.

Further, the material and shape of the housing constituting the deaerator 96 are not particularly limited, and further, regardless of whether the deaerator is non-porous or porous, it may be in the form or sheet, The bag may be in the form of a bag, or the pressure in the hollow fiber may be lowered to pass the solution around it.

Although the degassing method is not particularly limited, in this example, the membrane degassing method was used in order to avoid the possibility of the solvent volatilizing.

On the other hand, the freezing device 21 is provided with a tubular cooling pipe 36 connected in an annular shape. In this cooling pipe 36,
The degassed solution is supplied through the water supply pipe 100. Then, the water in the cooling pipe 36 flows along the cooling surface 36A (see FIG. 3) at a set flow velocity (for example, 1.0 m / sec) by the circulation pump 42 whose driving force is controlled by the controller 84. Circulate.

The vertical portion of the cooling pipe 36 is cooled by the cooling coil 46 in which the refrigerant circulates, and the cooling coil 46 shown in FIGS.
As shown in (B), the ice plate C is formed on the cooling surface 36A. An opening / closing door 48 is provided below the cooling pipe 36 so that the ice plate C can be taken out from below. In addition, the unfrozen concentrated water in the cooling pipe 36 is
When 1 is opened, it is sent to the distiller 64 through the drain pipe 50.

On the other hand, the ice plate C taken out from the freezing device 21 is temporarily stored in the ice storage tank 56 through the input pipe 54, and is supplied as cold water (or water containing ice particles) by the pump 58 through the cold water pipe 62. It is sent to the heat exchanger 60. As described above, by storing ice and supplying it as cold water, it is possible to stably supply the refrigerant to the heat exchanger 60. The heat exchanger 60 uses cold heat of cold water and is used for air conditioning in a factory.

Further, the cold water (water containing almost no solvent) that has undergone heat exchange in the heat exchanger 60 is sent to the storage tank 52 as recycled water, and is again sent to the processing tank 14.

On the other hand, the concentrated water containing the high-concentration solvent discharged from the freezing device 21 is sent to the distiller 64. The distiller 64 separates the solvent and water by vaporization by utilizing the difference in boiling points between the solvent and water, and water containing a high-concentration solvent is introduced into the distillation column 66 from the supply port 68. In the distillation column 66, the vapor and the liquid come into contact with each other, the solvent having a low boiling point component is collected in the vapor, and the water having a high boiling point component is concentrated in the liquid.

As a result, the solvent is sent as vaporized vapor to the condenser 72 through the exhaust pipe 70, and is condensed in the condenser 72 to be recovered in the recovery tank 74 as a solution containing a high-concentration solvent. Also, the water separated from the solvent is
It is drained from the drainage port 76 and sent to the storage tank 52 through the water supply pipe 82 equipped with the water supply pump 86.

Here, a procedure for freezing and separating water containing a solvent by the freezing device 21 into ice containing almost no solvent and water containing a high concentration of solvent will be described.

First, the solution is sent from the intermediate tank 16 to the deaerator 96 by the water feed pump 18, and the dissolved air in the solution is removed. This suppresses the generation of bubbles that become a factor for taking in the solvent when the freezing device 21 makes the solution ice. The degassed solution is supplied to the cooling pipe 36, and a predetermined flow velocity (1.0 m / sec) is applied to the cooling surface 36a as shown in FIGS. 3 (A) and 3 (B).
An ice plate C having a reduced solvent content is made on the surface of the ice plate.
In this way, by applying a flow rate to the water containing the solvent, the ice plate C having a small content of the solvent can be produced. In addition, the solution from which dissolved air has been removed becomes clean ice that does not entrap air bubbles.

Next, in order to demonstrate the effect of the present invention, an ice making test was conducted under different conditions as shown in the table of FIG. The present invention is not limited to the numerical values of this experiment and is included in the present invention as long as it does not depart from the gist of the present invention.

From the exhaust gas containing methanol discharged from the plant P, methanol was recovered by a scrubber as a gas-liquid contactor.

Exhaust gas containing methanol is 1.0 Nm
^It was introduced into the processing tower 12 at a rate of ³ / min. The content of methanol in the exhaust gas was 3000 ppm. When water drawn up from the treatment tank 14 was sprinkled from the sprinkler 32 of the treatment tower 12 and exhaust gas was introduced to perform batch treatment, the concentration of methanol in the water discharged from the treatment tank 14 was 1000.
It became 0 ppm.

Concentration of methanol as this solvent 1000
Intermediate tank 1 of freeze concentration and separation device 22
The solution was stored in No. 6 and 80 kg of the solution was freeze-concentrated and separated.

In the experiment, 60 kg of ice was made with a freezing device. The 60 kg of ice making means the amount of ice taken out from the freezing device. In the experiment in which the solution was not degassed before being sent to the freezing device (the residual ratio of the dissolved air in the solution was 100%), the concentration of the solvent in the ice made was 3500 ppm, and the solvent of the concentrated water after removing the ice The concentration is 29500ppm
Met.

In the experiment, a solution having a residual ratio of dissolved air of 80% was made into 60 kg of ice with a freezing device. The solvent content concentration of the ice making was 2000 ppm, and the solvent concentration of the concentrated water after removing the ice was 34000 ppm.

In the experiment, a solution having a residual ratio of dissolved air of 50% was made into 60 kg of ice with a freezing device. The solvent-containing concentration of the ice-made ice was 1000 ppm, and the solvent concentration of the concentrated water after removing the ice was 37000 ppm.

In the experiment, a solution having a residual ratio of dissolved air of 30% was made into 60 kg of ice with a freezing device. The solvent content concentration of ice-making was 800 ppm, and the solvent concentration of the concentrated water after removing the ice was 37600 ppm.

Thus, as can be seen by comparing experiments with each other, by reducing the residual ratio of dissolved air in the solution to be frozen, it is possible to produce clean ice without taking in the solvent and to enhance the concentration of concentrated water. .

Further, the concentrated water concentrated by the freeze concentration / separation device 22 may be reused as it is as an alternative fuel such as a cleaning liquid or heavy oil. When the concentrated water is sent to the distiller 64, the concentration of the solvent component contained in the water is preferably 1% or more, more preferably 10% or more.

Further, the heat-exchanged cold water may be decomposed in a wastewater treatment facility using activated sludge or the like, and depending on the concentration of the solvent component contained (if the COD value and the BOD value are within the allowable values). ), It may be discharged as it is.

The method of the water scrubber is not limited to the spray type, the filling type and the like, and the method of absorbing gas in water need not be the scrubber. Furthermore, the freezing device 21
Although the distiller 64 was used as a means for separating the water containing the solvent concentrated in 1. into the solvent and the water, a membrane separator, a centrifugal separator, or the like may be used.

Here, the PS plate manufacturing process, which is one of the manufacturing processes for generating the VOC gas, will be briefly described.

The PS plate is a JIS plate containing aluminum of 99.5% by weight, 0.01% by weight of copper, 0.03% by weight of titanium, 0.3% by weight of iron and 0.1% by weight of silicon.
-A1050 aluminum material with a thickness of 0.30 mm and rolled with 400 mesh pumice stone (manufactured by Kyoritsu Kiln)
Wt% aqueous suspension and rotating nylon brush (6,10-
Nylon) and the surface thereof was grained and then thoroughly washed with water.

This was immersed in a 15% by weight sodium hydroxide aqueous solution (containing 4.5% by weight of aluminum) to perform etching so that the amount of aluminum dissolved was 5 g / m ² , and then washed with running water. Furthermore, neutralize with 1 wt% nitric acid,
Next, in a 0.7% by weight nitric acid aqueous solution (containing 0.5% by weight of aluminum), a rectangular wave alternating waveform voltage (current ratio r = 0.9, voltage at anode: 10.5 V, voltage at cathode: 9.3 V).
0, the current waveform described in JP-B-58-5796) was used to perform electrolytic surface roughening treatment at an anode hour electricity of 160 coulomb / dm ² . After washing with water, 1 at 35 ℃
It was immersed in a 0 wt% sodium hydroxide aqueous solution, etched so that the amount of aluminum dissolved was 1 g / m ² , and then washed with water. Next, it was immersed in a 30% by weight sulfuric acid aqueous solution at 50 ° C., desmutted, and washed with water.

Further, a porous anodic oxide film forming treatment was carried out by using a direct current in a 20% by weight sulfuric acid aqueous solution (containing 0.8% by weight of aluminum) at 35 ° C. That is, electrolysis was performed at a current density of 13 A / dm ² , and the anodic oxide film weight was set to 2.7 g / m ² by adjusting the electrolysis time. In order to prepare a negative photosensitive lithographic printing plate using a diazo resin and a binder, this support was washed with water, immersed in a 3% by weight aqueous solution of sodium silicate at 70 ° C. for 30 seconds, washed with water and dried.

[0060] The thus-obtained aluminum support, reflection density was measured with Macbeth RD920 reflection densitometer 0.30, the center line average roughness R _a as defined in JIS B00601 is 0.58μm met It was

Next, methylmethacrylate /
The coating amount of a 1.0 wt% aqueous solution of ethyl acrylate / 2-acrylamido-2-methylpropanesulfonate copolymer (average molecular weight of about 60,000) (molar ratio 50/30/20) was dried by a roll coater. 0.05 g
It was applied so as to be / m ² .

Further, the following photosensitive solution-1 was used as a coating solution.
Apply using the bar coater used in the present embodiment, 110 ℃
And dried for 45 seconds. The dry coating amount was 2.0 g / m ² . Photosensitive solution-1 Diazo resin-1 0.50 g Binder-1 5.00 g Stilite HS-2 (manufactured by Daido Industry Co., Ltd.) 0.10 g Victoria Pure Blue BOH 0.15 g Tricresyl phosphate 0.50 g Dipicolinic acid 0 20 g FC-430 (surfactant manufactured by 3M Co.) 0.05 g Solvent 1-methoxy-2-propanol 25.00 g Methyl lactate 12.00 g Methanol 30.00 g Methyl ethyl ketone 30.00 g Water 3.00 g The above diazo resin-1 Is obtained as follows. First, 29.4 g of 4-diazodiphenylamine sulfate (purity 99.5%) was added to 96% sulfuric acid 70% at 25 ° C.
Slowly added to ml and stirred for 20 minutes. to this,
About 1 part of 3.26 g of paraformaldehyde (purity 92%)
The mixture was gradually added over 0 minutes, and the mixture was stirred at 30 ° C. for 4 hours to allow the condensation reaction to proceed. The condensation molar ratio between the diazo compound and formaldehyde is 1: 1. The reaction product was poured into 2 liters of ice water with stirring and treated with a cold concentrated aqueous solution in which 130 g of sodium chloride was dissolved. The precipitate is collected by suction filtration, the partially dried solid is dissolved in 1 liter of water, filtered, cooled with ice and washed with potassium hexafluorophosphate.
It was treated with an aqueous solution in which g was dissolved. Finally, the precipitate was collected by filtration and air dried to give 1 g of diazo resin-1.

Binder-1 is a 2-hydroxyethyl methacrylate / acrylonitrile / methyl methacrylate / methacrylic acid copolymer (weight ratio 50/20/26 /
4, average molecular weight 75,000, acid content 0.4 meq /
g) Water-insoluble, alkaline water-soluble film-forming polymer.

Stilite HS-2 (manufactured by Daido Industry Co., Ltd.)
Is a polymer compound having a higher oil sensitivity than the binder,
It was a copolymer of styrene / maleic acid mono-4-methyl-2-pentyl ester = 50/50 (molar ratio) and had an average molecular weight of about 100,000. The matte layer was formed by spraying the matte layer forming resin liquid on the surface of the photosensitive layer thus prepared as described below.

Methyl methacrylate / ethyl acrylate / 2-acrylamide-as a mat layer forming resin liquid
2-Methylpropanesulfonic acid (charge ratio 65: 2)
0:15) 12% with part of the copolymer as sodium salt
Prepare an aqueous solution, and rotate the atomizing head with a rotary atomizing electrostatic coating machine to a rotation speed of 2
5,000 rpm, the amount of resin liquid to be sent is 4.0 ml / min,
The applied voltage to the atomizing head was -90 kV, the ambient temperature during coating was 25 ° C, and the relative humidity was 50%. The coating solution was sprayed with steam for 2.5 seconds to wet it, and then 3 seconds after wetting. Warm air having a temperature of 60 ° C. and a humidity of 10% was blown for 5 seconds to dry. The height of the mat was about 6 μm on average, the size was about 30 μm on average, and the coating amount was 150 mg / m ² .

[0066]

Since the present invention has the above-mentioned constitution, it is possible to efficiently obtain ice containing as little solvent as possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a gas-liquid contact device in which a freeze concentration / separation device according to the present embodiment is used.

FIG. 2 is a block diagram showing a gas-liquid contactor in which the freeze concentration / separation device according to the present embodiment is used.

FIG. 3 is a schematic diagram showing how an ice plate is made into ice.

FIG. 4 is a table showing results of ice making experiments.

FIG. 5 is a side view showing a conventional gas-liquid contact device.

[Explanation of symbols]

21 Freezing device 48 Open / close door (separation means) 50 Drain pipe (separation means) 96 deaerator

Claims (2)

[Claims] 1. A freeze-concentration separation method in which water that has absorbed a solvent is frozen and separated into ice that does not contain a solvent and concentrated water that contains the solvent, a step of degassing the water that has absorbed the solvent, A freeze-concentration separation method comprising: a step of freezing the degassed solvent-absorbed water in a freezing device to make ice; and a step of separating the ice into concentrated water containing the solvent. 2. A freezing and concentrating separation apparatus for freezing solvent-absorbed water and separating it into solvent-free ice and solvent-containing concentrated water, wherein the solvent-absorbed water is deaerated. A freezing device that freezes the water that has absorbed the degassed solvent, and a separation means that separates the ice and concentrated water containing the solvent,
A freeze concentration / separation device comprising: