KR20050019432A - Continuous reactor for thermal degradation of polystyrene and method for recovery of styrene using it - Google Patents

Abstract

PURPOSE: A continuous reactor used for polystyrene pyrolysis and a method for collecting styrene monomers using the same are provided to discharge residues of the pyrolysis out of the reactor continuously, thus to prevent the deposition of such residues in the reactor and the generation of side products, and, as a result, to improve the generation of oil and the production yield of styrene monomers. CONSTITUTION: The continuous reactor used for polystyrene pyrolysis in which waste polystyrene is thermally decomposed and useful components are recollected, comprises: a reactor(5) in the form of a double tube comprising, as one unit, a first cylinder(6) and a secondary cylinder(7), each of which has a different diameter; an inlet hole(10) formed on the upper part of the reactor, through which melted polystyrene particles are introduced,; an exhausting hole(11) formed on the upper part of the reactor, through which gas generated from the pyrolysis is exhausted; and a discharging hole(12) for residues formed on the bottom part of the reactor, through which residues from the pyrolysis are discharged. The method for collecting the styrene monomer using the same comprises: melting crushed waste polystyrene; feeding the melted polystyrene particles to the reactor; subjecting the melted polystyrene to pyrolysis as passing the first cylinder and flowing down along the inner wall of the secondary cylinder, wherein gas is generated during the pyrolysis; injecting nitrogen gas into the reactor by using a nitrogen gas injector(9); discharging the generated residues after the pyrolysis out of the reactor in continuous way; liquefying the gas through a heat exchanger(13) so as to generate and collect oil(14) comprising styrene monomers.

Description

Continuous reactor for thermal degradation of polystyrene and method for recovery of styrene using it}

The present invention relates to a polystyrene pyrolysis continuous reactor and a method for recovering styrene monomer using the same, and more particularly, residues generated in the reactor for continuously pyrolyzing waste polystyrene dissolved in a melter are continuously discharged out of the reactor without stagnation. A polystyrene pyrolysis continuous reactor capable of suppressing the generation of by-products such as ethyl benzene, alpha methyl styrene, benzene and toluene, and at the same time increasing the yield of decomposition oil and the yield of styrene as a monomer, and a method for recovering styrene monomer using the same will be.

Recently, environmental problems caused by the generation of waste plastics such as PE (polyethylene), PP (polypropylene), PS (polystyrene), PVC (polyvinyl chloride), and the like are increasing.

The waste plastics as described above have a low recycling rate and are mostly disposed of as waste, and thus, it takes a long time to decay in a natural state. Therefore, measures for such waste plastics are required. Development of various technologies for this is in progress.

The recycling method of waste plastics is classified into a method as it is or recycled by processing (thermal material recycling), thermal recycling such as incineration, and chemical recycling such as water support fee.

As an example, in Korea, 300,000 tons of waste polystyrene is generated every year, and this waste polystyrene is mainly recycled to recycled resin, light-weight concrete, adhesives, etc. This is a physical regeneration method, and its added value is very low. After several physical regenerations, they cannot be recycled, resulting in a large amount of waste polystyrene.

In addition, a large amount of contaminated waste expanded polystyrene discharged to the agricultural and fishery market or construction waste is not clean compared to other waste polystyrene, so it is difficult to use it as a physical regeneration method.

Moreover, contaminated large amounts of waste expanded polystyrene are about 50 times more than other waste polystyrenes, and their disposal is difficult because they are difficult to landfill or physically recycle.However, incineration causes environmental problems such as dioxin generation. There is a problem.

Therefore, the technology for recycling the polystyrene to be discarded as described above has been progressed in various ways, the technology to recover and recycle the waste polystyrene to a chemical material such as styrene (monomer) through a chemical treatment step is proposed. It became.

Nishizaki et al. First attempted a recovery technique from waste polystyrene to monomer styrene, and it was reported that about 50% of styrene can be recovered from waste polystyrene by pyrolysis at a temperature of 733K. Many researchers have tried to increase the yield of styrene. The effects of various catalysts are examined by the researchers and many catalysts are being developed.

Meanwhile, FIG. 3 is a process diagram schematically illustrating a process of recovering styrene monomer by thermally decomposing conventional waste polystyrene.

As shown in the drawing, a conventional apparatus for recovering styrene monomer from waste polystyrene is composed of an injection molding machine, a melter, a reactor, a heat exchanger, and an oil storage tank, and the waste polystyrene crushed through the injection molding machine is dissolved through a melter to be added to the reactor. Injected and pyrolyzed gas in this reactor is liquefied through a heat exchanger and collected in an oil reservoir.

In more detail, in order to pyrolyze the waste polystyrene dissolved in the melter, conventionally, a pyrolysis reaction was continuously performed in a reactor of a continuous stirred tank reactor (CSTR) method as illustrated in FIG. 4.

However, if the conventional pyrolyzed waste polystyrene is continuously pyrolyzed for a long time, the catalysts developed above show little activity and inhibit the pyrolysis of polystyrene due to the accumulation of residues as the reaction time elapses. The problem of lowering the production of ethylene, lowering the yield of styrene as a monomer, and greatly increasing by-products such as ethylbenzene, alphamethylstyrene, benzene, and toluene was generated.

In other words, the ethylbenzene and alpha methyl styrene is almost similar to the boiling point of the monomer styrene, so that the amount required for the separation of styrene increases as the amount thereof increases, which greatly affects the economics.

Therefore, there is a great need for the development of a new pyrolysis reactor for treating styrene, which is a monomer, from waste polystyrene in high yield.

Therefore, the present invention has been invented to solve the above problems, by allowing the residue generated inside the reactor for continuously pyrolyzing the waste polystyrene dissolved in the melter to be discharged out continuously without stagnation, ethylbenzene It is an object of the present invention to provide a polystyrene pyrolysis continuous reactor capable of suppressing the generation of by-products such as alpha methyl styrene, benzene and toluene, and to increase the production of decomposition oil and the yield of monomer styrene, and a method for recovering styrene monomer using the same. .

The polystyrene pyrolysis continuous reactor according to the present invention for achieving the above object is a polystyrene pyrolysis reactor in which waste polystyrene is decomposed while heating to recover useful components. The upper portion is formed with an inlet through which dissolved polystyrene particles are introduced, and an outlet through which pyrolyzed gas is discharged by a pyrolysis reaction, and a residue outlet through which pyrolyzed and remaining residues are discharged.

In addition, the primary cylinder is formed with a larger diameter than the secondary cylinder, characterized in that the injection port portion of the secondary cylinder having a small diameter is formed in a shape protruding a predetermined section into the primary cylinder.

In addition, the inner surface of the secondary cylinder is characterized in that a plurality of folds are formed to protrude so as to increase the residence time of the reactants to be pyrolysis reaction while flowing along the inner surface.

In addition, the inside of the secondary cylinder is characterized in that it is further equipped with a nitrogen gas injector for helping the discharge of the gas generated by the pyrolysis reaction.

In addition, the styrene monomer recovery method using a polystyrene pyrolysis continuous reactor according to the present invention comprises the steps of injecting the polystyrene crushed in the injection molding machine; Injecting the polystyrene particles dissolved through the melter into the reactor; The dissolved polystyrene particles flow through the primary cylinder of the reactor along the inner surface of the secondary cylinder to pyrolyze and generate gas; Injecting nitrogen gas through a nitrogen gas injector in the reactor; Continuously discharging the residue generated after the gas and pyrolysis reaction from the reactor; Liquefying the pyrolyzed gas through a heat exchanger and collecting the oil produced therein in an oil reservoir; Characterized in that consisting of.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing a process for recovering styrene monomer by thermally decomposing waste polystyrene by installing a polystyrene pyrolysis continuous reactor according to the present invention, and FIG. 2 is a structure of a polystyrene pyrolysis continuous reactor according to the present invention, and a use state thereof. Figure is a diagram.

Here, reference numeral 2 denotes an injection molding machine, 4 denotes a melter, 5 denotes a reactor, 13 denotes a heat exchanger, 14 denotes an oil reservoir, and reference numeral 3 denotes a hopper.

As shown, the apparatus for recovering the styrene monomer from the waste polystyrene is composed of an injection molding machine (2), a melter (4), a reactor (5) and a heat exchanger (13) and an oil storage tank (14). The waste polystyrene crushed through the molding machine 2 is dissolved through the melter 4 and introduced into the reactor 5, and the gas pyrolyzed in the reactor 5 is liquefied through the heat exchanger 13 to obtain an oil storage tank ( 14) to be collected.

In more detail, the waste polystyrene is crushed to within a size of about 3 cm by the injection molding machine 2, and the crushed waste polystyrene particles are continuously introduced into the melter 4 and heated to a constant temperature for a predetermined time. And dissolve.

At this time, the melting temperature of the waste polystyrene particles dissolved through the melter 4 is suitable for 200 ℃ ~ 300 ℃, which is difficult to inject because the melting temperature of the waste polystyrene particles is less than 200 ℃ and almost no melting In this case, when the melting temperature exceeds 300 ° C., the pyrolysis reaction proceeds and thus a gas is generated. Therefore, the range is limited to 200 ° C. to 300 ° C.

In addition, the melting time of the waste polystyrene particles dissolved through the melter (4) is suitable to be 30 minutes to 5 hours, which is difficult to control the molecular weight when the melting time of the waste polystyrene particles is less than 30 minutes, When the melting time exceeds 5 hours, the cleavage reaction of the waste polystyrene proceeds excessively and the molecular weight decreases significantly, thereby greatly reducing the reactivity. Therefore, the range is limited to 30 minutes to 5 hours.

Next, as described above, the waste polystyrene particles (hereinafter referred to as reactants) dissolved through the melter 4 are introduced into the reactor 5 heated to a predetermined temperature to undergo a pyrolysis reaction.

The reactor (5) has a double-cylindrical cylindrical shape formed at the top of the inlet (10) through which the reactants are introduced, and the outlet (11) through which the pyrolyzed gas is discharged by the pyrolysis reaction. The residue outlet 12 which can be discharged is formed.

That is, the reactor (5) is formed integrally with the primary cylinder (6) and the secondary cylinder (7) of different diameter, the inlet portion of the secondary cylinder (7) having a small diameter into the primary cylinder It is formed in a protruding shape for a certain period, when the reactant is introduced through the inlet 10, the reactant flows along the inner wall of the primary cylinder 6 of the reactor 5, and the primary cylinder ( The reactant that flowed through the inner wall of 6) is maintained in a manner that is accumulated through the outer wall of the secondary cylinder 7 and heated or maintained at a constant temperature.

The reactants in the above state are filled to a certain amount by the reactants continuously introduced through the inlet 10 and flow over the inlet of the secondary cylinder 7 to the inner wall surface (hereinafter referred to as “reaction section”). As a result, the reactant is pyrolyzed while flowing down the wall of the reaction section heated to a predetermined temperature.

That is, the inflow state of the reactants introduced into the reaction section can be determined by the cylindrical shape of the double tube as described above, and the reactants introduced into the reaction section by the above method form a thin film on the wall of the reaction section. You can slowly flow down.

In addition, a plurality of folds 8 are protruded on the wall surface of the reaction section, and the rate of reactants flowing down the walls through the plurality of folds 8 may be slowed down.

That is, the falling rate of the reactant flowing along the wall of the reaction zone can be set slowly through the fold (8), which in turn increases the time the reactant stays in the reaction zone, causing sufficient pyrolysis reaction to occur. .

At this time, the reaction conditions of the reaction product of the pyrolysis reaction in the reactor (5) is suitable for the pyrolysis oil production rate of 10ml / min ~ 20ml / min at 370 ℃ ~ 450 ℃ temperature, if the temperature of the reaction conditions less than 370 ℃ There is a problem in that the rate of falling of the reactants increases, so that many unreacted substances are generated, and when the temperature exceeds 450 ° C. during the reaction conditions, carbon is generated on the wall, and the carbon flows together with the pyrolysis gas. (13) attached to the cylinder to contaminate the oil generated by condensation in the heat exchanger 13, causing the problem that the color of the oil gradually changes to black, resulting in a blockade of the heat exchanger cylinder, The range was limited to 370 degreeC-450 degreeC.

In addition, when the pyrolysis oil production is less than 10ml / min of the reaction conditions there is a problem that the recovery amount of the styrene monomer is small, the energy consumption is greatly improved when the pyrolysis oil production exceeds 20ml / min during the reaction conditions. In addition, in order to match the mass balance of the oil speed, the rotational speed (rpm) of the injection molding machine 2 is increased, and thus the raw material injection speed is increased, so that the reactant is uniformly reacted in the reaction section in the primary cylinder 6 at 300 ° C. Since there is a problem of blocking the inlet without entering, the rate of pyrolysis oil production rate is limited to 10 ml / min to 20 ml / min.

As described above, the reactants are pyrolyzed through the reaction section, and the gas generated therefrom is sent to the heat exchanger 13 through the outlet 11 of the upper portion of the reactor 5, and the remaining decomposition residues are pyrolyzed. It is continuously discharged through the residue outlet (12) of.

At this time, the lower one side of the reaction section is equipped with a nitrogen gas injector 9 so that the gas generated by the pyrolysis reaction as described above can be easily discharged to the heat exchanger 13 side, the nitrogen gas injector ( In 9), nitrogen (N ₂ ) gas is injected at a flow rate of 30 ml / min and is discharged together with the gas, and consequently, serves to help discharge the gas.

At this time, when the injection amount of the nitrogen gas is less than 30ml / min, the production rate of the oil condensed in the heat exchanger 13 is lowered, and when the injection amount of nitrogen gas exceeds 30ml / min is injected pyrolysis gas Since the heat exchanger 13 is not sufficiently condensed, there is a problem that the oil yield is lowered and odor is generated.

On the other hand, the gas discharged through the reactor (5) as described above is introduced into the heat exchanger 13, the heat exchanger 13 is to cool / condense the gas to obtain a liquid oil.

Finally, the oil generated through the heat exchanger 13 as described above is collected in the oil reservoir (14).

Hereinafter, the present invention will be described in more detail by the following examples and comparative examples, but the present invention is not limited by the following examples and comparative examples.

Example 1

example Pepolystyrene used in the invention used a debris of the sweet ingot (ingot) collected in the Garak-dong agricultural and fish market.

2 kg of the waste polystyrene collected as described above was crushed to a size of about 3 cm or less by the injection molding machine 2 and introduced into the melter 4 at a constant speed.

The waste polystyrene particles introduced into the melter 4 were dissolved with a reactant at 250 ° C. for a predetermined time and then injected into the reactor 5 according to the present invention.

At this time, the reactant dissolved at 250 ° C was injected into the primary cylinder (6) site of 300 ° C in the reactor (5), when the reaction water is injected into the secondary cylinder (7) site of 390 ° C to a certain level As it flowed down, the pyrolysis reaction proceeded.

The oil obtained by liquefying the decomposed gas obtained by the above pyrolysis reaction through the heat exchanger 13 was collected in the oil storage tank 14.

The resulting oil was observed in the degree of pyrolysis by measuring the volume over time using a measuring cylinder, and analyzed by gas chromatography at regular intervals as a reaction time of the composition of the oil as shown in Table 1 .

Example 2

In the same manner as in Example 1, but the primary cylinder (6) in the reactor (5) was maintained at 300 ℃ as the secondary cylinder (7) site was proceeded to pyrolysis reaction instead of 410 ℃ .

The generated oil was observed in the degree of pyrolysis by measuring the volume over time using a measuring cylinder, and analyzed by gas chromatography at regular intervals as a reaction time of the oil component analysis as shown in Table 2 .

Comparative Example 1

2 kg of waste polystyrene collected in the same manner as in Example 1 was crushed to a size of about 3 cm or less by an injection molding machine and fed into the melter at a constant speed.

The waste polystyrene particles introduced into the melter were dissolved with a reactant at 250 ° C. for a predetermined time and then injected into a conventional CSTR reactor.

At this time, the reactant dissolved at 250 ° C. was subjected to a pyrolysis reaction while stirring at a rotational speed of 200 rpm at 390 ° C. without a catalyst.

The oil obtained by liquefying the decomposed gas obtained by the above pyrolysis reaction through a heat exchanger was collected in an oil storage tank.

The resulting oil was observed in the degree of pyrolysis by measuring the volume over time using a measuring cylinder, and analyzed by gas chromatography at regular intervals as the reaction time elapsed, and the results are shown in Table 3. .

Comparative Example 2

2 kg of waste polystyrene collected in the same manner as in Example 1 was crushed to a size of about 3 cm or less by an injection molding machine and fed into the melter at a constant speed.

The waste polystyrene particles introduced into the melter were dissolved with a reactant at 250 ° C. for a predetermined time and then injected into a conventional CSTR reactor.

At this time, the reactant dissolved at 250 ° C. was subjected to a pyrolysis reaction while stirring at a rotational speed of 200 rpm at 410 ° C. without a catalyst.

The oil obtained by liquefying the decomposed gas obtained by the above pyrolysis reaction through a heat exchanger was collected in an oil storage tank.

The resulting oil was observed in the degree of pyrolysis by measuring the volume over time using a measuring cylinder, and analyzed by gas chromatography at regular intervals as shown in Table 4 as the reaction time elapsed. .

Comparative Example 3

2 kg of waste polystyrene collected in the same manner as in Example 1 was crushed to a size of about 3 cm or less by an injection molding machine and fed into the melter at a constant speed.

The waste polystyrene particles introduced into the melter were dissolved with a reactant at 250 ° C. for a predetermined time and then injected into a conventional CSTR reactor.

At this time, 1 wt% of barium oxide (BaO) was added as a catalyst to the reactant dissolved at 250 ° C, and proceeded to pyrolysis while stirring at a rotational speed of 200 rpm at 390 ° C.

The oil obtained by liquefying the decomposed gas obtained by the above pyrolysis reaction through a heat exchanger was collected in an oil storage tank.

The resulting oil was observed in the degree of pyrolysis by measuring the volume over time using a measuring cylinder, and analyzed by gas chromatography at regular intervals in the component analysis of the oil as the reaction time is shown in Table 5 .

Tables 1 to 5 show the test results of Examples and Comparative Examples according to the present invention, corresponding to the above object, when using a polystyrene pyrolysis continuous reactor according to the present invention regardless of the reaction temperature and the presence of a catalyst It was shown that the residue can be removed continuously, so that the yield of styrene for the oil produced can be maintained at a high yield even if the pyrolysis reaction is performed continuously for a long time.

That is, the yield of styrene in the oil resulting from the continuous pyrolysis reaction under the reaction conditions of 390 ° C. and 410 ° C. using the reactor according to the present invention is 55.75% by weight and 58.04% by weight. Appeared.

On the contrary, as a result of continuously performing pyrolysis reaction with or without a catalyst under the reaction conditions of 390 ° C. and 410 ° C. using a conventional CSTR reactor, the yield of styrene for oil produced gradually decreased.

As a result, as a result of continuously performing the pyrolysis reaction using the polystyrene pyrolysis continuous reactor according to the present invention, the yield of styrene was increased by about 25% compared to the case of using the conventional CSTR reactor.

On the other hand, in the above description, the pyrolysis continuous reactor according to the present invention is described only as being used to pyrolyze the polystyrene, but by using the pyrolysis continuous reactor according to the present invention to decompose plastics such as polyethylene and polypropylene, It is also possible to create.

As described above, according to the polystyrene pyrolysis continuous reactor according to the present invention and a styrene monomer recovery method using the same, residues generated in the reactor for continuously pyrolyzing the waste polystyrene dissolved in the melter are continuously without stagnation. By allowing it to be discharged outside, it is possible to suppress the generation of by-products such as ethylbenzene, alphamethylstyrene, benzene and toluene, while increasing the production of decomposition oil and the yield of styrene as a monomer.

Therefore, the recycling rate of the polystyrene to be discarded can be increased, and thus economic and environmental effects can be expected.

1 is a schematic diagram illustrating a process of recovering styrene monomer by thermally decomposing waste polystyrene by installing a polystyrene pyrolysis continuous reactor according to the present invention.

2 is a view showing the structure of the polystyrene pyrolysis continuous reactor according to the present invention and its use state

3 is a process diagram schematically showing a process of recovering styrene monomer by pyrolyzing conventional waste polystyrene

4 is a view showing a reactor of the conventional continuous stirred tank reactor (CSTR) method

<Explanation of symbols for the main parts of the drawings>

2: injection molding machine 3: hopper

4 melter 5 reactor

6: primary cylinder 7: secondary cylinder

8: double pool 9: nitrogen gas injector

10 inlet 11 outlet

12: residue discharge port 13: heat exchanger

14: oil storage tank

Claims (5)

In a polystyrene pyrolysis reactor for recovering useful components by decomposing waste polystyrene while heating, The primary cylinder 6 and the secondary cylinder 7 having different diameters are integrally formed in a double tube shape, and an inlet 10 through which dissolved polystyrene particles are introduced, and an outlet through which pyrolyzed gas is discharged by a pyrolysis reaction. (11) is formed, the lower portion of the polystyrene pyrolysis continuous reactor, characterized in that the residue outlet (12) is formed is discharged and the remaining residue is discharged. The method according to claim 1, The primary cylinder 6 is formed of a larger diameter than the secondary cylinder 7, characterized in that the injection port portion of the secondary cylinder 7 having a small diameter is formed in a shape protruding a predetermined section into the primary cylinder. Polystyrene pyrolysis continuous reactor. The method according to claim 1 or 2, Polystyrene pyrolysis continuous reactor, characterized in that the inner surface of the secondary cylinder (7) is formed to protrude a plurality of folds (8) so as to increase the residence time of the reactants to be pyrolysis reaction flowing along the inner surface. The method according to claim 1 or 2, Polystyrene pyrolysis continuous reactor, characterized in that the secondary cylinder (7) is further equipped with a nitrogen gas injector (9) to help the discharge of the gas generated by the pyrolysis reaction. Injecting the polystyrene crushed in the injection molding machine into the melter; Injecting the polystyrene particles dissolved through the melter into the reactor; The dissolved polystyrene particles flow through the primary cylinder of the reactor along the inner surface of the secondary cylinder to pyrolyze and generate gas; Injecting nitrogen gas through a nitrogen gas injector in the reactor; Continuously discharging the residue generated after the gas and pyrolysis reaction from the reactor; Liquefying the pyrolyzed gas through a heat exchanger and collecting the oil produced therein in an oil reservoir; Styrene monomer recovery method using a polystyrene pyrolysis continuous reactor consisting of.