JP2003335710A - Method for recovering styrene monomer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently recovering high-purity styrene monomer from waste polystyrene at a low cost. <P>SOLUTION: This method comprises installing several recovery systems for oil components, transferring the oil components recovered at each recovery system to a common fractionator and distilling the oil component therein to recover the styrene monomer, wherein the recovery systems are installed at several places each apart from others and each recovery system comprises a pyrolizer for recovering oil components from waste polystyrene and a condenser. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering styrene monomer by thermally decomposing waste polystyrene, condensing the produced decomposition gas and distilling an oil component obtained.

[0002]

2. Description of the Related Art There are various types of plastics discharged from factories and households, and polystyrene is used in many fields such as cases for home electric appliances and information equipment, food packaging trays, heat insulating materials, and cushioning materials. It is used, and as a result, it accounts for a large proportion of waste plastic. Material recycling is a method for recycling these waste polystyrenes. This is a waste polystyrene with a thermal decomposition temperature of 200
This is a method of heating and melting at a temperature of ℃ or below, and recycling as a recycled product. However, there is a problem in that recycled recycled products cannot avoid contamination and contamination, and only low-quality products can be obtained.

On the other hand, there is a method of recovering high-purity styrene monomer by thermally decomposing waste polystyrene, condensing the generated decomposition gas in a condenser, and distilling an oil component obtained by a distillation apparatus (for example, a special method). Kaihei 10-29834). Such high-purity styrene monomers can be recycled as high-quality plastic raw materials and other chemical raw materials, and therefore have extremely high added value.

[0004]

When recovering styrene monomer from waste polystyrene, the processing facility is equipped with a pyrolysis device, a condenser, a distillation device, etc. Among them, the distillation device includes a plurality of distillation columns. Since many peripheral equipments are required, installation cost and operation cost are high. Therefore, in many cases it is not profitable unless it is a large-scale processing facility that can take advantage of the scale of the distillation apparatus.

Further, since it is difficult to install a treatment facility at each place where waste polystyrene is produced or at a unit of a plurality of places where waste polystyrene is produced, a method of installing a large-scale central treatment facility and transporting the waste polystyrene from the place where waste polystyrene is produced is proposed. It is possible to adopt it.

However, another problem is that it takes a lot of time and cost to transport the bulky waste polystyrene from each generation site to the central processing facility. Then, this invention makes it a subject to solve these conventional problems, and an object of this invention is to provide the novel styrene monomer recovery method for that.

[0007]

According to the present invention for achieving the above object, waste polystyrene is thermally decomposed by a thermal decomposition device, the generated decomposition gas is condensed by a condenser to recover an oil component, and the oil component is recovered. This is a method of recovering styrene monomer by distilling with a distillation apparatus. In this method, a thermal decomposition device for recovering an oil component from waste polystyrene and an oil component recovery device equipped with a condenser are installed at mutually distant locations, and the oil recovered by each oil component recovery device is installed. It is characterized in that the components are transported to a common distillation device, and the oil component is distilled by the distillation device to recover the styrene monomer. (Claim 1)

In the above styrene monomer recovery method, a distillation apparatus in a styrene monomer production facility can be used as the distillation apparatus. (Claim 2)

Further, in the above case, at least one oil component recovery device can be installed adjacent to the styrene monomer production facility. (Claim 3).

In any one of the above methods for recovering styrene monomer, the thermal decomposition apparatus can be operated under reduced pressure. (Claim 4)

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual explanatory view of a method for recovering styrene monomer according to the present invention. A plurality of oil component recovery devices 1 including a thermal decomposition device and a condenser, and peripheral equipment for each waste plastic generation place or accumulation place, or for each of a plurality of waste plastic generation places or accumulation places close to each other ( In this embodiment, it is installed at 5 places).

On the other hand, a common distillation apparatus 2 is installed separately from each oil component recovery apparatus 1. The distillation apparatus 2 has at least a first distillation column for separating oil into a low boiling point component and a high boiling point component, and a second distillation column for separating styrene monomer and heavy oil from the high boiling point component separated by the first distillation column. Equipped with a distillation column. Note that only one of the oil component recovery devices 1 may be installed adjacent to the distillation device 2.

As described above, since the oil component recovery device 1 is composed of the thermal decomposition device, the condenser, and its peripheral equipment, the installation area of the device is smaller than that of the distillation device, and the installation cost and operating cost are low. Therefore, even if it is installed at each place where waste polystyrene is generated or where it is collected, commercial implementation is sufficiently possible. Then, the oil component whose volume is reduced to about several percent of the waste polystyrene from each oil recovery device 1
By transporting to the common distillation apparatus 2 as shown in FIG. 1, the labor and cost of transportation can be remarkably suppressed.

On the other hand, the distillation apparatus 2 having a large installation area and a large installation cost and a large operating cost is commonly used.
Since it is installed in only one place, the installation cost and operating cost of the entire system can be significantly reduced, and it has become possible to recover high-purity styrene monomer on a commercial basis.

FIG. 2 is a process flow diagram of the oil component recovery apparatus 1 shown in FIG. In the figure, 3 is a thermal decomposition device, 4 is a reactor, 5 is a heating part, 6 is a combustion part, 7 is a duct, 8 is an introduction part, 9 is a discharge part, 10 is a closing plate, 11 is a supply part, and 12 is a part. Hopper, 13 is a drive unit, 14 is a melting / extruding unit, 15 is an opening / closing means, 16, 17 and 18 are pipes, 19 is a condenser, 20
Is a cooling pipe, 21 is an oil component recovery tank, and 22 is a decompression device such as a vacuum pump.

The thermal decomposition apparatus 3 has a reactor 4 and a heating section 5 for heating the surroundings. The reactor 4 is of a tubular type, and the molten polystyrene introduced from the introduction part 8 provided at one end is thermally decomposed while passing through the inside thereof to generate a decomposed gas,
The decomposed gas is taken out from the discharge part 9 provided at the other end. The diameter of the reactor 4 is about several tens of millimeters to several hundreds of millimeters, and the length thereof is about 1 to several tens of meters. Is appropriately increased.

Residues accumulate in the reaction tube 4 due to long-term thermal decomposition. In order to take out the residue to the outside, a closing plate 10 which is removable by a bolt or the like is provided near the discharge part 9. A tank-type pyrolyzer can be used for the pyrolysis. The heating unit 5 has a combustion chamber whose periphery is formed of a heat resistant wall, and high temperature combustion gas is supplied from the combustion unit 6 such as an oil burner into the combustion chamber, and the combustion gas that has exchanged heat with the reactor 4 is discharged from the duct 7. Discharge to the outside. However, when the oil component recovery device 1 is small-scale, an electric heater heating type heating unit may be used.

The supply section 11 melts waste polystyrene by heating to generate molten polystyrene and supplies it to the thermal decomposition apparatus 3, and an extruder or the like generally used for plastic molding can be used. The supply unit 11 includes a hopper 12 for receiving waste polystyrene and a hopper 12
The melting / extruding unit 14 is provided for heating the waste polystyrene supplied from the drive unit 13 by the electric heater and extruding the molten polystyrene into the pipe 16. The melting / extruding unit 14 has a rotating screw arranged inside a cylindrical body,
Molten polystyrene corresponding to the rotation speed is quantitatively discharged. Therefore, the flow rate of the molten polystyrene discharged can be changed by changing the number of rotations of the drive unit that drives the rotary screw.

The condenser 19 is a cooling pipe 20 through which cooling water flows.
Is provided, and the decomposition gas discharged from the thermal decomposition apparatus 3 is cooled by heat exchange with the cooling pipe 20 and condensed to separate the oil component. The oil component discharged from the pipe 18 connected to the condenser 19 is recovered in the oil component recovery tank 21.

A pipe from a pressure reducing device 22 composed of a vacuum pump or the like is branched to the pipe 18. Pressure reducing device 22
Is provided for lowering the pressure of the reactor 4 below atmospheric pressure and performing thermal decomposition under reduced pressure. The low boiling point component that is not condensed in the condenser 19 is recovered in a recovery tank (not shown) provided on the outlet side of the decompression device 22. The thermal decomposition apparatus 3 and the condenser 19 are used as main equipment, and the oil component recovery apparatus 1 of the present invention is configured including the supply unit 11, the oil component recovery tank 21, the decompression device 22 and the like as additional equipment for them. It

Next, a method of thermally decomposing waste polystyrene by the oil component recovery device 1 to recover the oil component will be described.
First, the temperature in the heating unit 5 is set to 500 ° C. to 80 ° C. which is a temperature suitable for thermal decomposition of polystyrene by burner combustion in the combustion unit 6.
The temperature is raised to the range of 0 ° C. Then, the decompression device 22 is operated,
While replacing the inside of the system including the reactor 4 and the condenser 19 with an inert gas such as nitrogen to make oxygen free,
20 to 500 in the system including the reactor 4 and the condenser 19.
The pressure is reduced to about Torr, preferably about 50 Torr.

On the other hand, waste polystyrene is crushed into small pieces by a crusher (not shown) or the like, and the crushed pieces are supplied to a hopper 12 of a supply device 11 by an air feeder or the like. If the waste polystyrene is a foam, reduce the volume with an appropriate volume reduction means.
It is made into granules and then fed to the hopper 12. The waste polystyrene supplied to the hopper 12 is sent to the heating drive unit,
There, it is heated to about 150 ° C to 200 ° C and melted.

After confirming that the reactor 4 is in the absence of oxygen and has a predetermined temperature and a predetermined pressure, the supply unit 1
By operating the melting / extruding section 14 of No. 1 and opening the opening / closing means 15, molten polystyrene is supplied from the supply section 11 to the pipe 1.
It is supplied to the introduction part 8 of the reactor 4 via 6. The molten polystyrene supplied is heated from the surroundings and thermally decomposed while passing through the reactor 4, and the generated decomposition gas is discharged from the discharge part 9 to the pipe 17.

By pyrolyzing the reactor 4 while maintaining the temperature and the reduced pressure level within the above ranges, 70% by weight of styrene monomer, about 10% by weight of styrene dimer, about 10% by weight of styrene trimer, toluene, ethylbenzene, α Decomposition gas of about 2% by weight of methylstyrene and other by-products is obtained. By carrying out the thermal decomposition under reduced pressure, as described above, the production rate of by-products can be suppressed and the production rate of styrene monomer can be increased.

The decomposed gas discharged to the pipe 17 is condensed by the condenser 19
And is cooled therein to condense the oil component having a relatively high boiling point including the styrene monomer. The condensed oil component is recovered from the pipe 18 in the oil component recovery tank 21, and the condenser 19
The low-boiling-point gas component that does not condense in 1. is sucked into the decompression device 22 and is recovered in a recovery tank (not shown) provided on the outlet side thereof. Then, the oil component recovered in the oil component recovery tank 21 is appropriately placed in a drum or directly mounted on a tank truck to be transported to the distillation apparatus 2.

FIG. 3 is a process flow diagram of the distillation apparatus 2. In the figure, 30 is an oil component receiving tank, 31 is a transfer pump, 3
2 is a first distillation column, 32a is a second distillation column, 33, 34
Is a reboiler, 35 and 36 are condensers, 37, 38, 39,
40 is a pump, 41 and 42 are pressure control valves, 43 is a pressure reducing device, 44 and 45 are check valves, 46 and 47 are coolers, 48 is a monomer recovery tank, 49 is a heavy oil recovery tank, and a to h are It is piping.

The oil component receiving tank 30 receives and stores the oil components transported from each oil component recovery device 1. The first and second distillation columns 32, 32a can be either tray type or lashing ring, pole ring, or other filling type filled with high performance ordered packing,
The latter filling method is suitable when the depressurizing device 43 configured by a vacuum pump or the like performs depressurizing operation.

Heating steam or heating gas can be used as a heat source for the reboiler 33 for heating the first distillation column 32 from the bottom and the reboiler 34 for heating the second distillation column 32a from the bottom. Can be used as a heat source. The condenser 35 cools and condenses the low boiling point component distilled from the top of the first distillation column 32, and the condenser 36 forms the second distillation column 32.
The low boiling point component distilled from the top of a is cooled and condensed.

Next, a method of recovering the styrene monomer from the oil component by the distillation apparatus 2 shown in FIG. 3 will be described. When the operation is started, first, while operating the decompression device 43, the inside of the system is replaced with an inert gas such as nitrogen, and the first distillation column 32
And the 2nd distillation column 32a is made into the pressure reduction state of about 20-100 Torr. The pressure of the first distillation column 32 is adjusted by adjusting the pressure control valve 41, and the pressure of the second distillation column 32a is adjusted.
The pressure is controlled by adjusting the pressure control valve 42.

Next, the transfer pump 31 is operated to supply the oil component stored in the oil component receiving tank 30 to the middle stage of the first distillation column 32 to start distillation. When the oil component is subjected to a distillation operation in the first distillation column 32, low boiling point components such as toluene, ethylbenzene and α-methylstyrene of 3 to 5% by weight of the supplied amount are separated and distilled from the top of the column to flow into the condenser 35. To do. The low boiling point component is cooled by the condenser 35 and the component having a relatively high boiling point is condensed and discharged from the pipe c as an oil component.

A part of the oil component discharged to the pipe c is pump 3
It is refluxed to the upper part of the first distillation column 32 by 7 and the rest is recovered in the heavy oil recovery tank 49 through the check valve 44. The reflux ratio of the first distillation column 32 is preferably set to about 20-100. On the other hand, the low-boiling-point gas component which is not condensed in the condenser 35 flows out from the pipe e and is recovered in the recovery tank (not shown) via the pressure reducing device 43. The high boiling point components separated by the distillation operation are collected in the lower stage of the first distillation column 32,
The high boiling point component is supplied to the middle stage of the second distillation column 32a by the pump 38.

When the high boiling point component is distilled in the second distillation column 32a, the low boiling point component containing the styrene monomer is distilled from the top of the column and flows into the condenser 36. The oil component cooled and condensed in the condenser 36 flows out from the pipe g, and the non-condensed gas component flows out to the pipe e. The oil component flowing out from the pipe g is high-purity styrene monomer of about 99.9%, part of which is refluxed to the upper part of the second distillation column 32a by the pump 39, and the rest is cooled by the cooler 46. Is recovered from the monomer recovery tank 48. The proportion of styrene monomer recovered in the monomer recovery tank 48 is about 70% by weight of the amount of waste polystyrene supplied. The second distillation column 32a
The reflux ratio is preferably set to about 2-5.

On the other hand, in the lower stage of the second distillation column 32a, the heavy oil component as a high boiling point component separated by the distillation operation is collected. The heavy oil component is provided with a cooler 47 and a check valve 45. The heavy oil recovery tank 49 is recovered from the piping h by the pump 40. The heavy oil recovered is about 20 to 30% by weight of the amount of waste polystyrene supplied. The heavy oil stored in the heavy oil recovery tank 49 is supplied as a part of fuel to the heating steam generators of the reboilers 33 and 34, for example.

The distillation apparatus 2 used in the method for recovering styrene monomer of the present invention can be installed alone as described above, but it is also possible to use the distillation apparatus of the existing or newly installed styrene monomer production facility. A process flow diagram of a general styrene monomer production facility is shown in FIG. In the styrene monomer manufacturing facility 50 of FIG. 4, first, ethylbenzene as a raw material is dehydrogenated by a dehydrogenation device 51 to generate a mixture of styrene monomer and a by-product, and then the mixture is supplied to a distillation device 52 to perform a distillation operation. Then, the by-product is separated to recover high-purity styrene monomer. For simplification of description, the distillation apparatus 52 in FIG. 4 is illustrated with the auxiliary equipment other than the distillation column omitted.

The distillation apparatus 52 comprises a first distillation column 53, a second distillation column 54 for distilling high boiling point components of styrene monomer and heavy oil discharged from the lower part of the first distillation column 53, and a first distillation column 54.
Benzene, toluene distilled from the top of the distillation column 53 of
Third, by distilling and separating low boiling point components such as ethylbenzene,
It is equipped with fourth distillation columns 55, 56 and the like. (First in FIG. 4
Ethylbenzene is recovered from the lower part of the distillation column 53. )

Therefore, an oil component receiving tank 30 for receiving the oil component transported from each oil component recovery device 1 is provided in the premises of the styrene monomer manufacturing facility 50, and the received oil component is first distilled by the transfer pump 31. By supplying to the middle stage of the column 53, a highly pure styrene monomer having a purity of about 99.9% can be recovered.

The processing capacity of the styrene monomer production facility 50 is usually on the order of several hundred thousand tons per year, but the amount of commercially available recovered styrene monomer is usually 1/10 to 1/1.
Since it is only about 00, the distillation operation of the styrene monomer can be overlapped with the distillation operation of the original styrene monomer production with a sufficient margin. Specifically, the mixture from the dehydrogenation device 51 may be quantitatively mixed with the oil component from the oil component recovery tank 30, and the mixture may be supplied to the first distillation column 53. When the original production of the styrene monomer is stopped, the distillation operation can be performed by switching to only the oil component distillation operation from the oil component receiving tank 30.

As described above, by using the distillation apparatus 52 of the styrene monomer production facility 50 as the distillation apparatus used in the method for recovering styrene monomer of the present invention, the apparatus cost and the operating cost can be further reduced. Thus, it is possible to provide a realistic method capable of consistently recovering styrene monomer from waste polystyrene on a commercial basis.

In each of the above-described embodiments, the case where the waste polystyrene is a homopolymer has been described, but the present invention is not limited to the homopolymer, but can be similarly applied to a copolymer, that is, a waste styrene copolymer. Such waste styrene copolymers include waste styrene-acrylic copolymers (waste AS
Resin), waste styrene-butadiene-acrylic copolymer (waste ABS resin), and the like. Therefore, the term "waste polystyrene" in the present invention should be construed to include these copolymers.

[0040]

As described above, according to the method for recovering styrene monomer according to the present invention, an oil component recovery device can be installed at each place where waste polystyrene is generated or accumulated, and the waste polystyrene can be installed by these devices. The styrene monomer can be efficiently recovered by producing an oil component having a remarkably smaller volume, transporting it to a common distillation apparatus, and performing a collective distillation operation there. According to this method, it is possible to use a common distillation apparatus, which has extremely high installation and operation costs, so the overall system cost is reduced due to its economies of scale, and a series of processes from collecting and collecting waste polystyrene to recovering styrene monomer is expensive. Profitability can provide a method that can be carried out on a commercial basis.

In the above method of recovering styrene monomer, a distillation apparatus in a styrene monomer production facility can be used as the distillation apparatus. This makes it possible to further reduce the device cost and the operating cost.

Further, when using the distillation apparatus in the styrene monomer production facility as described above, at least one oil component recovery device can be installed adjacent to the styrene monomer production facility. With this configuration, at least the oil component recovery device provided adjacently can be installed on the same site as the styrene monomer manufacturing facility, and therefore the oil component can be directly transferred from the oil component recovery device to the distillation device by piping.

In any of the above methods for recovering styrene monomer, the thermal decomposition apparatus can be operated under reduced pressure. By performing such a reduced pressure operation, the production of by-products due to thermal decomposition can be suppressed and the yield of styrene monomer can be increased.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of a method for recovering styrene monomer according to the present invention.

FIG. 2 is a process flow diagram of the oil component recovery device 1 shown in FIG.

3 is a process flow diagram of the distillation apparatus 2 shown in FIG.

FIG. 4 is a process flow diagram of a styrene monomer manufacturing facility.

[Explanation of symbols]

1 Oil component recovery device 2 distillation equipment 3 Pyrolysis device 4 reactor 5 heating section 6 Combustion section 7 ducts 8 Introduction 9 Discharge part 10 Closure plate 11 Supply Department 12 hoppers 13 Drive 14 Melting / extruding section 15 Opening / closing means 16-18 piping 19 condenser 20 cooling pipe 21 Oil component recovery tank 22 Pressure reducer 30 oil component receiving tank 31 Transfer pump 32 First distillation column 32a Second distillation column 33,34 Reboiler 35,36 condenser 37-40 pumps 41,42 Pressure control valve 43 Decompression device 44,45 Check valve 46,47 Cooler 48 Monomer recovery tank 49 Heavy oil recovery tank 50 Styrene monomer manufacturing facility 51 Dehydrogenator 52 Distillation device 53 First distillation column 54 Second distillation column 55 Third distillation column 56 Fourth distillation column ah piping

Claims (4)

[Claims] 1. A method for recovering styrene monomer by thermally decomposing waste polystyrene by a pyrolysis device, condensing the produced decomposition gas by a condenser to recover an oil component, and distilling the oil component by a distillation device. An oil component recovery device 1 provided with a thermal decomposition device 3 for recovering an oil component from waste polystyrene and a condenser 19 is installed at a location distant from each other, and the oil recovered by each oil component recovery device 1 is installed. A method for recovering styrene monomer, which comprises transporting components to a common distillation apparatus 2 and distilling an oil component by the distillation apparatus 2 to recover styrene monomer. 2. The method for recovering styrene monomer according to claim 1, wherein the distillation apparatus 2 is the distillation apparatus 52 in the styrene monomer production facility 50. 3. The styrene monomer recovery method according to claim 2, wherein at least one oil component recovery device 1 is installed adjacent to a styrene monomer production facility 50. 4. The method according to any one of claims 1 to 3,
A method for recovering styrene monomer, which comprises operating the thermal decomposition apparatus 3 in a reduced pressure state.