JP2003012855A - Polystyrol resin, solvent recovering apparatus, and solvent recovering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent stop of a continuous operation followed by an intermittent operation, due to a problem such that the volume of a gel mixture is sometimes full in a reaction vessel owing to a bubbling phenomenon from inside and therefore a separating rate of a solvent becomes insufficient, when vaporizing and separating the solvent from a viscous liquid such as the gel mixture. SOLUTION: A vaporizing apparatus according to this invention is composed of at least one stage or more of vaporizing units wherein a polystyrol resin and the solvent are separated from the gel mixture that is obtained by dissolving and mixing a foamable polystyrol resin in the solvent. At least a first stage vaporizing unit of the above apparatus has a double-helical ribbon blade. A bottom part of the vaporizing apparatus has a liquid collecting part. By controlling an exhausting volume of a exhausting pump from a liquid pressure of the above liquid collecting part and a gas phase pressure of the vaporizing apparatus, the intermittent operation is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene resin and a solvent by separating a polystyrene mixture and a solvent from a gel-like mixture obtained by dissolving and mixing the expanded polystyrene resin in a solvent in the field of waste recycling. The present invention relates to a recovery device and a recovery method for a polystyrene resin and a solvent for reusing styrene.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional apparatus for separating and collecting polystyrene resin and solvent. In this example, one receiving tank 400 and one paddle type stirring tank or a process mainly including an evaporation device such as a thin film evaporation device 401 is included. FIG. 6 shows an example of an evaporation device called a vertical thin film evaporation device 501.

The injected gel G is received in the receiving tank 400.
From the above, solid matters are removed by a filter 405, unnecessary water is removed by a dehydrator 410, and then the mixture is fed to an evaporator 401.
The solvent is evaporated by being heated by the heat mediums 401a and 401b and separated into the solvent and the polystyrene resin. In the evaporator 401, conventionally, a paddle type stirring tank for rotating the blade called a paddle to stir and mix the gel-like mixture to separate the solvent vaporized and foamed inside the gel-like mixture from the polystyrene resin portion, or The solvent vaporized and foamed inside the gel mixture as shown in FIG. 6 is pressed against the wall surface 512 by using the stirring blade 511 by driving the rotating shaft 510 provided on the upper portion so as to be easily vaporized as a thin film, and the vaporized solvent is separated. ,
On the other hand, the polystyrene is sent to the bottom of the container one by one by the blade-shaped stirring blade 511, and the recycled material outlet 52 is passed through the screw 550.
The thin film evaporator 501 which discharges from 1 is used. The recovered polystyrene resin 420 is recovered as a rod-shaped body. The evaporated solvent is discharged through the solvent vapor outlet 522, condensed in the heat exchanger 440, and collected as a liquid 455.

In a paddle type stirring tank type evaporator, stirring with a stirring blade called a paddle does not provide a sufficient stirring and mixing action when the viscosity of the fluid is high. The degassing performance was not always sufficient because the stirring was insufficient due to the rise in temperature and carry-over, and the gelled mixture swelled. The thin film evaporator 501 has a drawback that the structure is complicated and expensive.

[0005]

In the conventional method of the type such as a paddle type stirring tank, a viscous substance such as a gel-like mixture causes a volume increase of the gel-like mixture in the reaction vessel due to a foaming phenomenon from the inside. In some cases, the solvent separation speed was not sufficient, or continuous operation was stopped and intermittent operation was performed. Another problem is that the structure is complicated and expensive like a thin film evaporator.

In the present invention, a device having a simple structure is used, and the solvent vaporized and vaporized from the gel-like mixture containing the polystyrene resin is rapidly diffused into the gas phase to reduce the expansion of the viscous body due to foaming. (EN) An apparatus and method for facilitating the vaporization and separation of the solvent, recovering the solvent in a short time, and regenerating the polystyrene resin having a low solvent content by continuous operation.

[0007]

The feature of the present invention is that the gel mixture is swelled due to the formation of bubbles due to the evaporation of volatile components, so that the operation stop frequently occurring in the existing evaporator is prevented, It also provides an inexpensive device that enables continuous operation.
It will be explained based on. An evaporator according to the present invention is a recovery device provided with at least one or more evaporators for separating a polystyrene mixture from a gel-like mixture obtained by dissolving and mixing foamed polystyrene resin in a solvent. This is an evaporator using at least a first-stage evaporator using a double helical ribbon blade. The second feature of the present invention is that a liquid reservoir is provided at the bottom of the evaporator. A third solution means is to control the discharge amount of the discharge pump from the liquid pressure in the bottom liquid pool of the evaporator and the pressure in the vapor phase part of the evaporator.

This evaporator has a double helical ribbon blade, and the structure is such that the upper part of the evaporator 1 has a heating medium 3 as shown in FIG.
2, a tank portion for heating by 2 and 33 is arranged, and jackets 15a and 15 for keeping the temperature by heat mediums 30 and 31 are provided at the lower portion.
The liquid reservoir 40 including b is arranged. The double helical ribbon blade was installed by connecting it to a rotating shaft 10 connected to a motor (not shown) by connecting rods 11a, 11b, 11c with ribbon supporting rods 12a, 12b, 12c. The double helical ribbon blade 13 provided in the evaporator tank 1
Each of a and 13b has a width of about 1/10 of the inner diameter of the tank, has a spiral shape in which the diameter of the evaporator tank increases with one rotation, and is provided along the inner wall of the evaporator tank.

The double helical ribbon wings 13a, 13b
Of the double helical ribbon blades 13a, 13b
In order to prevent the liquid level 14 of the gel-like mixture from rising abnormally to reach the solvent vapor outlet 22 when stirring, the height is set to cover approximately half the height of the inner surface of the tank, and the amount of the gel-like mixture is When the double helical ribbon impeller is agitated, the height is set to be almost the same as that of the double helical ribbon impeller, and the third solution is used to control the amount so that the gel mixture does not agitate efficiently.

The gelled mixture containing the heated polystyrene resin is fed into the evaporator 1 through the gel inlet 20, and the double helical ribbon blades 13a and 13b are rotated to form the gelled mixture on the blade. By repeating lifting so as to be separated from the adjacent gel-like mixture, the mixture is sufficiently agitated and mixed, and is lifted upward on the wall surface side of the evaporator tank 1.
At the center of the gel surface, the gel surface is lowered to form a deep concave surface 14 and the surface area of the gel-like mixture can be remarkably increased.

Since the above phenomenon occurs due to the stirring and mixing by the rotation of the double helical ribbon impeller, the bubbles generated by the evaporation and evaporation of the solvent from the inside of the gel-like mixture are promptly discharged to the free surface, and the volatile components are released into the free space. It is possible to quickly dissipate and eliminate abnormal bubbles.

The double helical ribbon wings 13a, 13
240 ° C. to 245 ° C. under normal pressure due to the increase of the surface area of the gel-like mixture by the rotation of 30-40 rpm of b) and the movement of the gel-like mixed substances by stirring while shearing each other.
The solvent vaporized and vaporized by heating the solution is rapidly transferred to the free surface of the vapor phase part of the surface of the gel-like mixed substance while forming bubbles inside the gel-like mixture, so that the recovery of the solvent becomes extremely fast. The gelled mixture from which the vaporized components have been removed and whose bulk density has increased is collected in the liquid pool 40 at the bottom of the evaporator tank, discharged from the gel outlet 21 by the pump 112, and proceeds to the next stage. Reference numeral 30 denotes the heat medium inlet of the liquid pool portion, and 31 denotes the heat medium outlet.

The liquid reservoir 40 is for continuously separating and recovering the polystyrene resin and the solvent, and therefore the liquid reservoir 40 is used.
Is provided in the lower part of the tank of the evaporator so that the vaporized component is separated and the gel mixture having an increased density is retained so that the pressure of the gel mixture can be measured.

In the liquid reservoir 40, the solvent vaporized in the gel mixture is double helical ribbon blades 13a and 13b.
Since the mixture is agitated by the rotation of No. 1 and scattered from the free surface, and the movement of the gel-like mixture is calmed down, the pressure can be measured by, for example, a diaphragm method by providing a pressure gauge 41 in the liquid reservoir 40. The measured pressure is transmitted to the gel supply pump 112 by the flow of an electric signal as shown in FIG. 3, and the gel mixture is discharged from the gel supply pump so that the amount of the gel mixture in the evaporator tank becomes constant. You can That is, by comparing the pressure Pg303 in the vapor phase portion in the evaporator tank with the pressure Pp302 in the liquid reservoir, the pressure (ΔP = Pp−Pg) of the gel-like mixture is calculated, and the height H of the gel-like mixture is (ΔP / density). Can be calculated from, and the amount can be calculated from height. In this way, since the amount of the gel mixture remaining in the evaporator tank can be calculated from the magnitude of the pressure difference, when the amount of the gel mixture is large, the discharge amount of the gel mixture from the tank 1 is increased. If the amount is small, the discharge amount is reduced, and the discharge pump is operated so that the remaining amount in the tank always exists in an appropriate and operable amount.
By such a treatment, a predetermined amount of gel-like mixture can be made to remain in the tank, and continuous operation can be performed without stopping operation due to foam expansion in the tank.

The amount of the residual solvent varies depending on the residence time of the gel mixture in the tank, but the amount of the solvent removed is short and insufficient in a short time, and the longer the residence time, the economical efficiency of the solvent removal deteriorates. . Here, as a result of various tests, an average residence time, that is, (remaining amount in evaporator tank / discharge amount of gel mixture per hour) of 30 minutes to 60 minutes was preferable.

It is possible to remove most of the solvent in the gel-like mixture by the above-mentioned method to make the residual amount of the solvent 5 to 10 wt% from the gel-like mixture containing the solvent having an initial value of about 50 wt%. However, if it is desired to further reduce the residual amount of solvent, as shown in FIG.
The evaporation device 2 is provided as the evaporating device of the stage, and the amount of the solvent can be reduced by the multiple effect. In the evaporator 2, if the pressure in the tank 2 is reduced, the solvent can be removed more quickly.

FIG. 2 shows a method of vaporizing and discharging the solvent by a droplet dropping method as the second-stage evaporator 2.
In this method, a droplet forming device including a heat exchanger, that is, a heating device 120 that introduces the heat medium 103a and 103b to heat the gel mixture to 250 ° C to 255 ° C is provided, and the gel mixture is made into a small liquid. The flash tank 2 decompressed as drops is dropped to vaporize and remove the solvent in the gel. By these treatments, the polystyrene resin having a solvent concentration of 1 to 5 wt% could be recovered.

However, also in the second-stage evaporator 2, the solvent can be vaporized and separated in the same manner by installing a double helical ribbon blade as in the first-stage evaporator. In the second-stage evaporator 2, the concentration of polystyrene resin in the gel-like mixture increases, the mixing ratio of the solvent decreases, and the viscosity of the gel-like mixture also increases. The temperature of the gel-like mixture is raised to a temperature that is easy to handle, for example, 250 ° C. to 255 ° C., and the internal pressure of the second-stage evaporator is set to about 100 Torr to 500 Torr in order to quickly vaporize and separate the solvent. It is preferable to carry out the treatment under reduced pressure.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates according to FIG.

[0020]

[Embodiment 1] FIG. 2 shows an inner diameter of 800 m using the double helical ribbon blades 13a and 13b shown in FIG.
2 shows a styrene resin recovery device provided with an evaporator 1 having a diameter of 500 mm and an evaporator 2 having an inner diameter of 500 mm for vaporizing and separating a solvent by dropping droplets under a reduced pressure of about 500 Torr. The recovered polystyrene is discharged from the second-stage evaporator 2 by the feed pump 212 and cooled water 2
It is cooled by 01 and conveyed by the conveyor 210 and accumulated in the recovery tank 231. The vaporized solvent vapor from the first-stage evaporator is introduced by the exhaust pump 200, passes through the condenser 130, is condensed, and is accumulated in the solvent tank 150. The vapor from the second-stage evaporator 2 is guided by a vacuum pump 199 that can further reduce the pressure, passes through a condenser 140, is condensed, and is accumulated in a molten material tank 160.

The gel mixture G containing about 50 wt% of the recovered polystyrene resin and a solvent such as xylene is put into a receiving tank 90. The injected gel G is heated by the heat medium circulation 101a into the jacket 96 provided on the outer circumference of the container.
It is heated to about 50 ° C. to 55 ° C. by 101b and is stirred by the paddle 93 to give almost uniform fluidity. The gel mixture was discharged from the bottom of the tank by a feed pump 92 driven by a motor 91, and the temperature was about 255 ° C to 2 ° C.
Approximately 240 ° C to 245 ° C through the heat exchanger 110 heated by the heat mediums 102a and 102b heated to 60 ° C.
It is heated to and is guided to the evaporator 1 equipped with the first stage double helical ribbon blade.

Although the first-stage evaporator 1 is operated at normal pressure, an exhaust pump 2 for recovering the vaporized and evaporated solvent is used.
The pressure is slightly reduced by 00. The double helical ribbon blade 13 has a ribbon width of about 1 of the inner diameter of the evaporator.
It is set to / 10 and is installed at an inclination angle that raises the diameter of the evaporator 1 by one rotation, rotates at about 30 to 40 rpm, and stirs so as to cut the surface of the gel mixture while lifting the gel mixture. .

The agitated gel-like mixture is lifted by the ribbon near the wall surface in the evaporator 1 so as to cut the gel-like mixture adjacent to the ribbon blade, and is high around the inner wall of the evaporator, and at the center of the evaporator. The deep concave surface 14 is formed and well mixed by stirring. At this time, the bubbles generated inside the gel-like mixture due to the evaporation of the solvent by the heating are quickly discharged onto the free surface along with the movement of the gel. The solvent vapor that has reached the gas phase region is cooled by the exhaust pump 200 through the condenser 130, condensed, and recovered as a liquid.

The gel-like mixture in which the amount of foaming is decreased and the bulk density is increased is settled, for example, the inner diameter is 200 mm and the height is 15 provided in the lower part of the evaporator 1 equipped with a double helical blade.
Collect in the 0 mm liquid reservoir 40. The liquid pool 40
A diaphragm type liquid level gauge 41 is attached to the first stage evaporator, and the liquid level height is calculated from the pressure difference between the vapor phase part and the motor 11
The feed pump 112 is controlled in rotation speed through 1 to keep the gel amount in the first evaporator tank at a predetermined amount. In this way, the flash tank 1 can be continuously operated. As a result, continuous operation was possible without causing an operation stop due to foam expansion in the evaporator tank.

The gel-like mixture discharged from the first-stage evaporator 1 was treated with a gel containing about 50 wt% of the solvent in this apparatus, and the solvent and polystyrene were recovered. When the time, that is, (remaining amount in evaporator tank / ejecting amount of gel mixture per hour) is set to 0.8 hours, 5 to 10 wt% of the solvent still remains, so that the second evaporator 2 is used. The solvent is vaporized and separated.
Here, at the entrance of the second-stage evaporator, the heat medium 103a, 1
03b is used to slightly heat it to about 250 ° C to 255 ° C to lower the viscosity coefficient so that the gel-like mixture can be easily operated. Here, a method is adopted in which droplets are formed in the upper part of the second-stage evaporator 2, the surface area is increased and dropped, and the pressure is reduced to about 500 Torr to remove the vaporized solvent.

As a method for removing the vaporized solvent from the gel-like mixture, double helical ribbon blades 13a and 13b may be employed as in the first-stage evaporator 1 in addition to the above.

In this way, the solvent of this apparatus is about 50 w.
As a result of treating the gel mixture containing t% and recovering the solvent and the polystyrene resin, for example, the gel mixture obtained by vaporizing and separating the solvent with an average residence time in the evaporators 1 and 2 being 0.8 hours is It was possible to recover the recycled polystyrene resin having a solvent amount of about 1 to 5 wt%.

The polystyrene resin is discharged from the discharge pump 212,
For example, it is discharged by a gear pump, cooled and solidified by the cooling water 201, and collected as a solid.

The solvent vaporized and evaporated is stored in the condenser 13
0,140 to cool and condense liquid 150,160
To collect and reuse.

[0030]

[Embodiment 2] FIG. 4 shows an example of a polystyrene resin recovery apparatus for recovering a solvent by a single-stage evaporator. This recovery device is provided with only one stage of evaporation device provided with the double helical ribbon blades 13, and the residual amount of the solvent in the regenerated polystyrene resin is slightly increased, but the regenerated polystyrene resin is solid fuel or It can be used as a recycled polystyrene resin. In this case as well, the pressure is measured by the liquid level gauge 41 provided in the liquid reservoir 40, and the amount of gel remaining in the evaporator is calculated from the pressure difference between the pressure in the upper vapor phase part in the evaporator tank and the evaporation is calculated. The rotation speed of the feeding motor 111 of the apparatus was controlled to keep the amount of gel remaining in the evaporator at a predetermined amount, and the average residence time in the evaporator was set to 0.8 hours to perform continuous operation. A gel-like mixture containing approximately 50 wt% of the solvent was treated by this apparatus, and the solvent and polystyrene were recovered. As a result, it was possible to recover the recycled polystyrene resin containing 5 to 10% of the solvent during normal pressure operation. .

Further, when the exhaust pump 200 was operated at an evaporator internal pressure of 500 Torr, the polystyrene resin containing 3 to 8% of solvent could be recovered.

[0032]

EFFECTS OF THE INVENTION By providing a double helical ribbon blade in the first-stage evaporator as in the present invention, it is possible to quickly separate the vaporized solvent and reduce the amount of residual solvent. We were able to establish a technology for continuous operation without causing an outage due to foam expansion in the equipment tank. In addition, 1 to 5% can be obtained by converting the evaporator into two stages.
It is possible to recover and regenerate a high-purity polystyrol resin containing the solvent, and even in the case where only a single-stage evaporator is used, a relatively high-purity polystyrol resin containing 3 to 10% of the solvent can be recovered. I was able to play it.

[Brief description of drawings]

FIG. 1 is a front view of an evaporation device having a double helical ribbon blade and a liquid pool on the bottom.

FIG. 2 shows a polystyrol resin recovery device equipped with an evaporator having a double helical ribbon blade and a liquid pool in the first stage.

FIG. 3 shows the flow of an electric signal for controlling the rotation speed of the motor of the discharge pump based on the pressure in the liquid reservoir and the pressure in the vapor phase of the evaporator tank in the evaporator having the double helical ribbon blade.

FIG. 4 shows a polystyrol resin recovery device equipped with a flash device having a double helical ribbon blade having only the first stage evaporation device and a liquid pool.

FIG. 5 shows an example of a flow of a conventional method.

FIG. 6 shows an example of the structure of a conventional thin film evaporation apparatus.

[Explanation of symbols]

1 Evaporator 10 with Double Helical Ribbon Blades Rotating Shafts and Shaft Seals 11a, 11b, 11c Connecting Rods 12a, 12b, 12c Ribbon Support Rods 13, 13a, 13b Helical Ribbon Blades 14 Liquid Level Shape 30 of Gel-like Mixture Part heat medium inlet 31 Liquid reservoir Heat medium outlet 40 Liquid reservoir 41 Liquid reservoir pressure measuring unit 111 Gel feeding motor 112 Gel feeding pump 150 First stage recovery solvent tank 160 Second stage recovery solvent tank 199 Vacuum pump 200 Exhaust Pump 211 Gel Feeding Motor 212 Gel Feeding Pumps 300, 300a, 300b Gel Feeding Controllers 301, 301a, 301b Gel Feeding Command Signals 302, 302a, 302b for Evaporator Liquid Reservoir Pressure Signals 303, 303a, 303b Evaporator Tank Gas Phase Pressure Signal 401 Evaporator 501 Thin Evaporator 511 stirring blade 512 film evaporator inner wall

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaru Nagaoka             4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture               Ryomei Giken Co., Ltd. (72) Inventor Hiroshi Sone             Kanagawa Prefecture Sagamihara City Tana 3000 M             Ichii Sagami High Tech Co., Ltd. (72) Inventor Katsumi Hashimoto             Kanagawa Prefecture Sagamihara City Tana 3000 M             Ichii Sagami High Tech Co., Ltd. F-term (reference) 4D076 AA03 AA12 AA14 AA22 AA24                       BA01 CB04 CB05 CB06 CD12                       CD50 JA01                 4F301 AA15 CA03 CA09 CA12 CA42

Claims (3)

[Claims] 1. A recovery device provided with at least one stage of an evaporator for separating a polystyrene mixture into a solvent from a gel-like mixture obtained by dissolving and mixing a foamed polystyrene resin in a solvent. An apparatus for recovering polystyrene resin and a solvent, wherein an evaporator using a double helical ribbon blade is used as a first stage evaporator. 2. The recovery device according to claim 1, wherein a liquid pool is provided at the bottom of the evaporator, and the polystyrene resin and the solvent are recovered. 3. The polystyrene resin and solvent according to claim 1 or 2, wherein the discharge amount of the discharge pump is controlled based on the liquid pressure in the bottom liquid pool of the evaporator and the pressure in the vapor phase part of the evaporator. Recovery method.