DE4243063A1 - Pyrolytic decomposition of plastic waste - comprises thermally decomposing waste, separating pyrolysis prod. into two fractions, recycling first fraction and recovering lighter second fraction - Google Patents

Abstract

Pyrolytic decomposition of plastics comprises: (a) thermally decomposing the plastics in a pressurised atmosphere to obtain a pyrolysis prod.; (b) removing the pyrolysis prod. into a first fraction, contg. a relatively heavy component, and a second fraction, contg. a relatively light component; (c) recycling the first fraction into the decomposition step (a); and (d) recovering the second fraction. An appts. for carrying out the process is also claimed. The appts. comprises: (i) a decomposing unit (2) to thermally decomposing plastics to obtain a pyrolysis prod.; (ii) a separating unit (3) to separate the prod. into 2 fractions (iii) a recycling unit (4) for recycling the first fraction to (2); and (iv) a recovery unit (5) to recover the second fraction. USE/ADVANTAGE - Fuel oil of high quality is obtd. by pyrolysing plastic waste in an efficient process.

Description

The present invention relates to a method and a Device for the pyrolytic decomposition of Plastic waste, it relates in particular to a technology for the efficient production of high quality fuel oil through pyrolysis of plastic waste.

Plastic materials are usually on a large scale for the production of household electrical appliances and various other items because of their advantageous properties of a light weight and good strength has been used, the cycle of Manufacture and wear of plastic materials however, this resulted in a large amount of waste was produced by plastic objects, and this Plastic waste had to be incinerated or by to be deposited at the current time. More recently has, however, since the enactment of a law Recycling in 1991 in Japan, the public Interest in Japan directed to waste from Plastic products are recycled and reused.

However, the plastics come in a wide variety before, and a piece of a plastic object is in the  general by using different types of Made of plastic. Makes any kind of plastic however, a different treatment method for the purpose to facilitate recycling. In that sense it is for the waste plastic items required that they are in the various components separated according to the type of plastic contained such a procedure is complex, and it also seems pretty difficult in practice complete these measures. As a result are the quality and value of the recovered products inevitably been reduced because of this incomplete separation. In more difficult cases it is even impossible to practice repatriation perform.

In such a case the technique has a dry one Distillation of the waste plastic received a lot of attention withdrawn because of this procedure the possibility contains the waste plastic objects in relative terms return high quality products. These However, dry distillation processes require presently high cost, and it exists the need for recovery efficiency to improve even further with this type of technology. If it is a thermoplastic material, such as polystyrene, polypropylene and the like, which a has low thermal conductivity, it is above difficult, a quick and uniform heating a large volume of items from the to accomplish thermoplastic material, and that from Oil obtained from such a thermoplastic contains a large amount Variety of ingredients whose boiling points are wide are scattered. As a result, it is practical  Application of the dry distillation technique also necessary to improve the quality of the oil obtained.

As a method to improve the oil quality is in JP-OS S63-1 78 195 and H2-29 492 proposed one Vapor phase reaction catalyst such as zeolite and the like Use purpose of improving oil quality. In the It is an apparatus for performing this method however necessary the process part of the thermal Decomposition and the procedural part of the Improve the quality of the oil separately. in the As a result, such a facility requires a large one Space for the creation and high operating costs.

Furthermore, if a waste from a plastic mixture, the contains a polyvinyl chloride resin (hereinafter referred to as PVC resin), is thermally decomposed, a corrosive hydrogen chloride gas that covers the walls of the thermal decomposition furnace damaged. Some products which contained from the decomposition of a PVC resin Plasticizers come, often also cause the Gas flow in the pipe system of the decomposition plant is clogged.

As described above, the conventional methods have been for the thermal decomposition of plastic waste with Problems related to poor oil quality and Recovery yield for the fuel oil obtained, as well as the requirement related to the plant for thermal decomposition to protect against damage through the production of hydrogen chloride and Decomposition products from the plasticizer material to provide.

The object of the present invention is therefore a Process for the pyrolytic decomposition of Provide plastic materials where a High quality fuel oil Waste plastic items obtained in an efficient manner becomes.

Another object of the present invention is a device for the pyrolytic decomposition of To provide plastic materials to a High quality fuel oil Waste plastic items in an efficient manner win.

The above object is achieved in the present invention by providing a process for the pyrolytic decomposition of a plastic material which comprises steps in which:
Thermally decomposes plastic in a pressurized atmosphere to produce a pyrolysis product;
separating the pyrolysis product obtained in the thermal decomposition step into a first fraction containing a relatively heavy component and a second fraction containing a relatively light component;
recycle the first fraction separated in the separation stage to the thermal decomposition stage;
and the second fraction separated in the separation stage wins to obtain a recovered product composed of the second fraction.

The pyrolytic decomposer comprises:
Decomposing device parts for thermally decomposing plastic in a pressurized atmosphere to produce a pyrolysis product;
Separator parts for separating the pyrolysis product obtained into a first fraction containing a relatively heavy constituent and a second fraction containing a relatively light constituent;
Return device parts for returning the first fraction to the decomposing device parts;
and recovery device parts for recovering the second fraction to obtain a recovered product composed of the second fraction.

According to the present invention Performance of pyrolytic decomposition of the Waste plastic improves and the yield of the extracted oil increased significantly compared to those the conventional process. In addition, the won Oil produced in a high quality.

The features and advantages of the process and the Device for the pyrolytic decomposition of plastic according to the present invention will become even clearer understandable from the following description of the preferred embodiments of the present invention in Connection with the accompanying drawings, in which identical reference numerals the same or similar elements or designate sections throughout the figures and wherein:  

FIG. 1 shows an apparatus for performing the method according illustrates a block diagram of an exemplary arrangement of the pyrolytic decomposition of plastic materials of the present invention; and

Fig. 2 is a block diagram of another exemplary arrangement of apparatus for carrying out the method according represents the pyrolytic decomposition of plastic materials of the present invention.

First, the basic principle of the process of pyrolytic decomposition of plastic materials according to of the present invention.

If plastic materials at a temperature inside a range of 300 to 600 ° C under normal pressure without deliberate supply of oxygen decomposes pyrolytically will be different components in different Molecular weights contained in the pyrolysis gas in Competition generated. Therefore, the received one Oil, if the pyrolysis gas is condensed into oil, not so high quality so that it is not for use as Fuel material, from the point of view of air pollution viewed from, is suitable. Especially in the case of thermal decomposition of polyethylene solidifies it Condensate of the pyrolysis gas mixture very often to a Allow wax to form at room temperature as it is a contains a large amount of heavy components.

On the other hand, when the plastic materials are thermally decomposed in a closed reaction system, the pressure in the generation reaction of the pyrolysis gas from the plastic materials in the system increases spontaneously. At the same time, the molecular movements are activated and the thermal conductivity in the reaction system is increased. In addition, since the boiling points of each component are raised due to the pressure increase, the heavy or high molecular weight components tend to remain in the liquid phase, and therefore the decomposition ability can be improved under the above reaction conditions. Thus, the decomposition ability can be improved by increasing the pressure in the pyrolytic decomposition stage. However, too high a pressure causes too much volatile components to be generated which are too easy to condense at room temperature, thus causing the yield of condensed oil to decrease. In view of this, a pressure within a range of 1 to 10 kgf / cm ^{2 is} preferably applied as the valve pressure to the reaction system.

However, as stated above understandable, the effect of the pressure in it, the area the molecular weight distribution of the components of the Decomposition product to the side lower Just shift molecular weights. That's why it is not possible to prevent the extracted oil from going through heavy substances to be contaminated by the above described thermal decomposition process alone under increased pressure. In other words, the Molecular weight distribution range in the oil obtained can by the thermal described above Decomposition processes under increased pressure alone are not be restricted. Accordingly, it is impossible to do that To get high quality oil.  

On the other hand, it is possible to use the Molecular weight distribution range of the components of the extracted oil by using a thermal Narrow the decomposition process, including stages are in which one: the pyrolysis gas cools around a heavy one Condense fraction so that the heavy fraction of separated a light fraction of the pyrolysis gas can be; and the condensed heavy fraction into the Decomposition stage. The application of this The procedural measure can definitely Distribution area of the oil building up Components compared to that of the Concentrate the pyrolysis gas product. That through the thermal Decomposition of pyrolysis gas product obtained under normal pressure however, contains large amounts of various heavy ones Ingredients so that they are not adequately covered by the above described cooling level can be removed. Furthermore is the yield of oil recovered from this thermal Decomposition process also reduced.

Given the facts described above, the here occurring inventor research work on the Field of pyrolytic decomposition processes Through plastic materials and it was found that when the stage of performing the pyrolysis of Plastic materials are combined under increased pressure with the stage of fractionation of the pyrolysis gas product, to only a fraction of the desired light components to win, it becomes possible to improve the quality and yield of the Oil drastically improved, and that from the Oil obtained from plastic materials contains hardly any Components with a boiling point above 250 ° C.

The method and apparatus for pyrolytic decomposition of plastic according to the present invention is characterized in that: the plastic is pyrolytically decomposed under increased pressure to obtain a pyrolysis gas product; and that the pyrolysis gas product is fractionated into a fraction of relatively heavy constituents and a fraction of relatively light constituents, from which the fraction of the heavy constituents is returned to the decomposition stage. The light components to be condensed and obtained as an oil material that are not condensed in the fractionation stage are passed to the recovery stage. Here, the pyrolysis gas product obtained in the decomposition stage is mainly composed of the relatively light substances, but it still contains a relatively small amount of heavy components, so that in the fractionation stage the pyrolysis gas product is cooled to a predetermined temperature in order to condense the relatively heavy components, which are to be separated from the light components. As described above, since the molecular weight distribution of the constituents of the pyrolysis product is shifted to a lower range in accordance with the increase in pressure in the decomposition reaction system, the pressure applied in the pyrolytic decomposition stage of the present invention is set to a predetermined value which is appropriately adjusted to get the oil in a desired quality. If e.g. For example, if a fairly light fuel such as kerosene is to be obtained, it is preferable to apply a pressure within a range of 1 to 6 kgf / cm ² as a valve pressure on the pyrolytic decomposition system. If pressure within the preferred range described above is used, an oil product of the desired quality can be obtained in a yield of about 50 to 80% by weight. More preferably, the pressure to be applied to the pyrolytic decomposition system is selected from a range of 3 to 5 kgf / cm ² . Under the preferred printing conditions described above, the waste plastic is heated to a temperature within the range of about 300 to 600 ° C.

This is due to the pyrolytic decomposition of the plastic Pyrolysis gas product obtained is then in the Fractionation stage, in this stage it is Pyrolysis gas cooled to a predetermined temperature, those below that of pyrolytic decomposition lies. As a result, relatively heavy components of the Pyrolysis gas mixture condensed and from the relative separated light components that remain gaseous. The condensate of the heavy components is then in the pyrolytic decomposition stage recycled where it continues be cracked. On the other hand, the relatively light ones Ingredients that go through the fractionation stage in the extraction stage further cooled to a temperature close to normal temperature so that it liquefies and can be extracted as oil that from relative light components is composed.

Here, the components of the fraction that the Fractionation level, according to the level changed the cooling temperature in the fractionation stage will. Accordingly, the cooling temperature if there is it is desired to obtain an oil that can be obtained from one at 150 up to 250 ° C distilled fraction is composed, for. B. Kerosene, preferably within a range of 200 to 350 ° C or more preferably within a range of 250 to 300 ° C, a preferred pressure such as  is used as described above. In the event that the Cooling temperature is lower than the above ranges the contamination with the heavy components a boiling point above 250 ° C can be reduced. A too much cooling, however, reduces the amount of Oil product over a period of time can be won away. It is also possible to have one achieve adequate separation by using the Fractionation of the pyrolysis gas product under normal pressure carries out. However, the cooling temperature should be in this Case should preferably be set at a level that is lower than the cracked gas in the above case to separate clearly.

The above-described method of pyrolytic decomposition of waste plastic can be carried out by using an apparatus having a structure shown in FIG. 1.

According to the arrangement of FIG. 1, the device 1 for the pyrolytic decomposition of plastic contains: a decomposition container 2 for the pyrolytic decomposition of plastic; a separation column 3 for fractionating the pyrolysis gas product into a heavy fraction of relatively heavy components and a light fraction of relatively light components; a pump 4 for returning the heavy fraction from the separation column 3 into the decomposition container 2 ; and a recovery device part 5 , wherein the light fraction condenses and is obtained in the form of an oil from the relatively light components which are cooled by a cooling pipe inside the extraction device 5 .

The separation column 3 is kept at the temperature which is lower than that of the decomposition vessel 2 . The decomposition container 2 and the separation column 3 are connected by a pressure control valve 6 , which functions in such a way that when the valve pressure inside the decomposition vessel 2 rises above a first set value in response to the thermal decomposition of the plastic, the control valve 6 the gas lets flow from the decomposition vessel 2 into the separation column 3 and then the valve pressure within the decomposition vessel 2 is kept at the first fixed value. In addition, the separation column 3 and the recovery device 5 are also connected by a pressure control valve 7 which functions so that when the valve pressure in the separation column 3 exceeds a second set value, the pressure control valve 7 opens to release the gas from the separation column 3 into the Release extraction device 5 to keep the pressure in the separation column 3 at the second set level.

According to the arrangement of Fig. 1, when the wastes of broken plastic objects are heated in the decomposition vessel 2 , the plastic pieces are thermally decomposed to generate the pyrolysis gas so that the pressure in the decomposition vessel rises. Then, the pressure reaches the first set value, the pyrolysis gas is discharged into the separation column 3 to be cooled to the temperature inside the separation column 3, so that the heavy components are condensed with high boiling points. The condensate of the heavy components is returned to the decomposition vessel 2 by the pump 4 to be subjected to the thermal decomposition again. On the other hand, when the pressure inside the separation column 3 reaches the second set value set by the pressure control valve 7 , the light fraction from the light components which are not condensed in the separation column 3 is discharged into the recovery device 5 . The light fraction is then cooled to a temperature near the normal temperature enough to be condensed into an oil that is collected in the container 8 . Low-boiling constituents which cannot be liquefied in the extraction part 5 are passed into a gas treatment device 9 for the corresponding aftertreatment.

In the actual treatment of Waste plastic items close the Waste plastic items usually have a wide variety of plastic materials and it's complicated different waste items in the mixture according to the To separate types of plastic materials. Therefore it is very desirable to mix the waste of the Plastic items without separating or sorting the treat different plastic materials.

In this context it should be noted that each type of Plastic polymer is split differently, e.g. B. be the polymer molecules of polypropylene, polyethylene and the like. split anywhere, while those of Polystyrene and the like are cracked so that their Starting monomer is formed, and the polymers of Polyvinyl chloride and the like are on their side branches split. In any case, the product contains mainly unsaturated hydrocarbon compounds such as olefin compounds and aromatic compounds, so that in thermal decomposition treatment one Mix of different plastic items the above described unsaturated hydrocarbon compounds  be generated. In contrast, an as Oil fuel suitable material mainly from paraffinic components and one small amount of aromatic components such as kerosene and the like contain. Accordingly, it is desirable to use the olefin components by the pyrolytic decomposition of the Waste plastic obtained oil product in the to transfer the corresponding paraffin components. To for this purpose it is preferred to use active alumina, To use zeolites and the like because they act as a catalyst act for the hydrogenation reaction of olefin double bonds can.

This catalyst described above can be installed in the separation column 3 as a catalyst 11 , as shown in the pyrolytic decomposition device 10 of FIG. 2. Alternatively, instead of the separation column 3, an isothermal column loaded with the catalyst may be connected to the control valves 6 and 7 and the pump 4 at the preferred temperature described above. In this way, the isothermal column loaded with the catalyst can serve both as a separation column 3 and as a catalyst 11 .

The following points should now be considered in the pyrolytic Decomposition of the plastic materials according to the present invention can be noted.

If the waste plastic material to be decomposed halogen-containing polymer such as polyvinyl chloride, Polyvinylidene chloride and the like a harmful and corrosive gas such as hydrogen chloride gas generated by the thermal decomposition that the damage pyrolytic decomposition device and the  oil can contaminate. Also included Polyvinyl materials generally include a plasticizer such as Di (2-ethylhexyl) phthalate (DOP) and the like in one Percentage of approx. 30% by weight. This plasticizer DOP reacts when heat is applied and becomes Phthalic anhydride converted as by the following Reaction equation (1) given.

The phthalic anhydride sublimates easily, so that it Pipe system of the pyrolytic decomposition device gets stuck to close the passage of the gas product clog or stop. To solve this problem it has been found to be effective, an alkaline Substance the waste plastic during thermal To cause decomposition.

As an example of the alkaline substance to be added Hydroxyl compounds of an alkali and alkaline earth metal, e.g. As sodium hydroxide, etc. can be used. Alkaline Compounds like this react with hydrogen chloride gas, to generate salt and water vapor, like in the following equation (2).

As a result, most of the hydrogen chloride gas which is generated by the primary thermal decomposition, ie by the decomposition at the side sites of the polyvinyl chloride component, is converted into metal chloride, which is not sublimed and remains in the decomposition vessel 2 . Therefore, a high quality oil product that hardly contains chloride compounds can be obtained.

In addition, in the presence of the alkaline compound, the plasticizer or DOP contained in PVC resin is converted into metal salt of phthalic acid according to the alkaline saponification reaction as indicated by the following reaction equation ( 3 ).

Therefore, neither phthalic acid nor phthalic anhydride generated during thermal decomposition, and consequently it can be made possible, the pipe system through which the pyrolysis gas product flows to prevent it is closed by these connections. In case that a small amount of phthalic acid or phthalic anhydride is generated and adheres to the pipe system, the Water vapor caused by the neutralization reaction of the alkaline compound and hydrogen chloride gas is generated, the sublimed phthalic acid compounds dissolve to flow back into the decomposition vessel leave so that a blockage of the flow in Pipe system can also be prevented. On Similarly, other ester compounds that are in the Waste plastics are included as additives, hydrated so that the waste plastic easily through Heat can be decomposed, it will also be relieved Decomposition of difficult  waste plastic to be decomposed.

Further, since the metal chloride salts can be dissolved in water, the decomposition residue (carbon) stuck to the salt in the decomposition vessel 2 can be easily removed by washing the decomposition vessel 2 with water after the thermal decomposition process is completed. In addition, the alkaline agent that remains unreacted can also be washed off with water. Therefore, the cleaning of the device can be carried out easily after the operation.

The one to be used in thermal decomposition alkaline agent is not only to those described above Hydroxide compounds are restricted, and so can corresponding metal connections and Metal oxide compounds are used. The amount of added alkaline substance varies depending on the amount of PVC resin to be treated Waste plastic is included. When using a Alkali metal hydroxide compound can be used in one amount Range of about 0.2 to 2.0 parts by weight is preferred be used, based on the amount of PVC resin. Is insufficient amount of the alkaline agent can Hydrogen chloride gas are generated, which in turn the Generation of many chlorinated organic compounds can cause. The piping system of the Pyrolysis device by the sublimated Decomposition products from the plasticizers blocked. Becomes however, an excessive amount of the alkaline Connection used, consumes the mode of operation of the Device facility a huge amount of energy and that Corrosion of the decomposition container can advance  will. In addition, the oil product obtained from the Metal component of the alkaline agent contaminated. The Alkaline agent can plastic before thermal Decomposition treatment can be added directly, although the Type of delivery of the alkaline agent not on this special procedure is restricted.

The effects of the alkaline agent described above by adding a small amount of water expanded. Therefore, it is more preferable to use thermal To perform decomposition in the presence of water improve the quality of the oil product. The addition of Water also significantly reinforces the prevention of through Sublimation blocking the Pipe system. To achieve the above effects required amount of water varies depending on the Type of waste plastic to be treated, temperature thermal decomposition treatment, etc. In general can contain an amount of about 0.1 to 1 part by weight of water are preferably used, based on a part by weight Plastic. If the amount of water is insufficient, is not perform the decomposition effectively. If against the amount of water is too high becomes the energy yield during thermal decomposition operation reduced. For these purposes it is for that too using water desirable that there are some Contains impurities. The water can the plastic added directly before the thermal decomposition treatment be, although the type of water supply does not depend on this particular approach is restricted. E.g. can use water as a water solvent to dissolve it of the alkaline material explained above will. Here it applies that if the person to be treated Waste plastic water in a manner as described above  contains an appropriate amount, no additional water is needed.

The water can become a source of hydrogen Will improve the quality of the oil product however the water evaporates and during the thermal decomposition away from waste plastic dispersed, it becomes impossible to have sufficient effect to achieve the water on the plastic. In the However, the present invention is the density of the Water vapor inside the decomposition vessel is high because the atmosphere inside the decomposition vessel below Pressure is present so that the added water can effectively perform the functions described above. in the As a result, the polymer chains of the plastic become light split, and using the amount of light ingredients a small molecular weight increases in the recovered Oil product. In other words, it can High quality oil product such as gasoline can be obtained.

In addition to what has been said above, it is also found out that the alkaline agent described above also exerts a catalytic effect on performance the decomposition both in the decomposition of PVC resin as of another non-PVC plastic material too improve. This catalytic effect is both in Case of decomposition in an atmosphere under pressure as even in the event of decomposition in an atmosphere below Normal pressure exerted. Therefore, when heating the Waste plastic with water and the alkaline material such as sodium hydroxide and the like, under increased pressure Extraction yield of the oil product increased significantly both in the case of decomposition of PVC resin as well in case of decomposition further  different types of plastic. At the same time, the The quality of the oil obtained can be improved, especially since extracted oil entirely from light components Molecular weight is composed.

With regard to the suitable amount of the alkaline agent to be added to exert the catalytic effect, it is preferred in the case of using sodium hydroxide to add an amount greater than or equal to about 5% by weight, based on the amount of plastic. If the amount is less than 5% by weight, the decomposition performance deteriorates. The alkaline agent can be added directly to the plastic before the thermal decomposition treatment, although the way in which the alkaline agent is supplied is not limited to this particular procedure. In order to exert this catalytic effect, it is also preferable for the thermal decomposition treatment to be carried out in the presence of water, and the appropriate amount of water is greater than or equal to 10% by weight based on the amount of plastic. If the amount of water is less than 10% by weight, the ratio of the heavy components in the oil product obtained increases. It is also preferred to use water that contains some impurities. The water can be added directly to the plastic before the thermal decomposition treatment, although the way the water is supplied is not restricted to this particular procedure. The atmosphere inside the decomposition vessel is preferably under a valve pressure greater than or equal to 1 atm (approx. 1.03 kgf / cm ² ).

In order to actually carry out the process of pyrolytic decomposition of plastic materials according to the present invention, the device is intended to withstand the above-described harsh conditions regarding a high temperature, an atmosphere under high pressure and corrosion damage due to highly concentrated alkali. In this regard, it has been found that a corrosion-resistant alloy containing nickel and chromium is suitable as the material for the decomposition vessel 2 . More specifically, an iron alloy containing the nickel component in a ratio greater than or equal to 5% by weight and the chromium component in a ratio greater than or equal to 10% by weight has been found to be preferred. For example, a stainless steel SUS F 304 according to Japanese industry standard No. G3214 is suitable for the decomposition vessel 2 . If the ratio of the nickel component is low, the corrosion resistance of the alloy deteriorates, so that it is difficult to withstand corrosion damage by the highly concentrated alkaline agent at a high temperature under elevated pressure. If the ratio of the chromium component is low, the mechanical properties of the alloy deteriorate at high temperature, so that it is no longer suitable for use under increased pressure.

As described above, the iron alloy containing nickel and chrome, in the Corrosion resistance and mechanical strength at a high temperature, so that this alloy is Material for an apparatus for operating the method according to the pyrolytic decomposition of waste plastic of the present invention. In addition, it should be noted be that the nickel and chrome components in the above mentioned iron alloy are capable of Decomposition reaction of the waste plastic under increased  Pressure to act catalytically.

In addition to the thermoplastic compounds like Polyethylene, polystyrene, polypropylene and the like can the waste plastic objects thereof to be decomposed be assumed that they made articles from thermosetting Contain connections, e.g. B. sealing plastic for Semiconductor devices. In this regard, it was found that in the pyrolytic decomposition of a mixture of various waste plastic items without the Sorting different types of contained Materials that yield the oil obtained from the Plastic articles made of polystyrene, polyethylene and the like can be improved if these plastic items in the presence of the sealing plastic for the Semiconductor devices are treated.

The sealing plastic for semiconductor devices contains usually silicon dioxide (silicic acid), which is caused by a Raw material such as pyrogenic quartz glass powder, crystalline Silica gel powder and the like are introduced. These Silicic acid materials generally have a high Thermal conductivity, so that the silica in thermosetting sealed plastic the low Thermal conductivity of the thermoplastic materials balances and the thermal conductivity of the Overall plastic mixture improved. As a result of that can the temperature of the plastic mixture within the Decomposition vessel can be increased uniformly and quickly. Therefore, it is not necessary at all Plastic waste mixture in groups of thermoplastic Materials and thermosetting materials before to separate thermal decomposition treatment, and in the Indeed, it is more preferable to like the waste plastic mixture  it is to heat up the yield of the oil obtained to increase. Will the sealing resin for semiconductor devices, the Silicon dioxide in a ratio of approx. 70% by weight contains, introduced into the reaction system, and if 10 up to 20 wt .-% of the sealing resin, based on the amount of other waste plastic, can be mixed obtained oil with 8 to 10% increase in Extraction yield can be won.

As another method to improve Thermal conductivity can be a heat transfer medium in Form of a molten salt, inert oil such as silicone oil and the like. are added to the waste plastic material. Such a heat transfer medium is in the Decomposition temperature of the treated plastic in liquid state and serves to increase the Heat transfer effect so that it is possible to To quickly raise the temperature of the plastic. At the same time can the treated plastic because of the fluidity of the heat transfer medium are uniformly heated, so that the generation of hot spots prevented and a improved safety of operation can be achieved can.

In addition, the heat transfer medium can cause the tar generated by the decomposition reaction to be prevented from adhering to the decomposition vessel 2 .

Furthermore, the heat transfer medium can also serve to shield the treated plastic from oxygen gas. Usually the oxygen gas oxidizes especially the Plastic partially so that it as Decomposition initiator can be used. However, the oxygen gas affects the  Properties of the oil obtained strong. In particular, if the oxygen gas is above 15 Vol .-% is present, the fuel oil obtained has a high Viscosity and contains a large amount of Tar components so that the yield of the oil obtained is also low. Therefore no oxygen is allowed fed during the thermal decomposition treatment will. For this purpose, if that Heat transfer medium applied as described above the waste plastic through the fluid medium covered so that during thermal Degradation treatment should be shielded from oxygen can.

As the heat transfer medium described above, an inert oil having a boiling point higher than or equal to 400 ° C, a molten salt having a melting point lower than or equal to 200 ° C, and the like can preferably be used. As typical examples, a silicone oil and inorganic molten salts such as a ternary nitrate, e.g. B. NaNO ₃ -KNO ₃ -NaNO ₂ can be used. However, the heat transfer medium is not limited to these preferred examples, and any other medium which is liquid during the thermal decomposition treatment and which does not react undesirably with the plastic can be used.

In the present invention, it is also effective to use one Add catalyst to the waste plastic to achieve the To influence decomposition reaction. It will be one or several catalysts preferably selected from nickel oxide, Iron (III) oxide, cobalt oxide, copper oxide, manganese dioxide, Silicic acid, zirconium oxide (zirconia) and titanium dioxide (Titania), depending on the type and property of the  plastic to be treated. By adding the The amount of ingredients with a catalyst low molecular weight in the oil obtained, and the molecular weight distribution in the generated ones Components are concentrated so that the quality of the obtained oil product can be improved. The Catalyst is preferably used in an amount within the Range of 10 to 200 wt .-%, based on the amount of treating plastic used.

Even if the catalyst to accelerate the Decomposition reaction for thermal decomposition the addition of water is also used effective to improve the quality of the oil obtained. The preferred amount of water to be added fluctuates in Depending on the type of plastic to be treated and the temperature of the thermal decomposition treatment. in the however, it is generally preferred to keep the water inside in a range of 0.1 to 2 parts by weight based on the amount of plastic to be treated. Is insufficient water quantity, the deteriorates Decomposition performance. At the same time, the Range of molecular weight distribution of oil components and the production of olefin components is encouraged, so that the properties of the oil product can deteriorate. If, on the other hand, an excess Amount of water is added, you need an undesirable high amount of energy to operate the device. Also it is preferred water that has some impurities contains. The water can precede the plastic added directly to the thermal decomposition treatment be, although the type of water supply does not depend on this particular approach is restricted.  

Each component of the Heat transfer medium, decomposition reaction catalyst and water achieves the respective separately effect described above and the combined use of the components is capable of the effects achieved continue to increase.

Examples

With reference to the drawings and results of the Experiments are now the preferred embodiments of the Method and device for pyrolytic Decomposition of plastic materials according to the described the present invention.

1. Effect of the combined level of thermal Decomposition under pressure and separation / reflux keeping of heavy components.

Trial 1

In a pyrolytic decomposition device 1 , which was constructed as in FIG. 1 and had a decomposition vessel 2 made of stainless steel, 100 g of polyethylene pellets were placed in the container 2 and each of the pressure control valves 6 and 7 was at a valve pressure of 4 kgf / cm, respectively ² set. Next, the temperature of the separation column 3 was set to 300 ° C, and the decomposition container was heated to 450 ° C.

When the temperature of the polyethylene pellets rose to the decomposition temperature, the pressure in the decomposition vessel 2 began to rise, and the decomposition vessel 2 and the separation column 3 filled with pyrolysis gas. When the pressure within these device parts exceeded 4 kgf / cm ² , a part of the decomposition gas was released into the recovery device part 5 and the valve pressure in the decomposition container 2 and the separation column 3 was reduced to 4 kgf / cm ² . A pump 4 was operated while observing the gas released in the extraction device part 5 . By the above procedure, the pyrolysis gas was cooled in the separation column 3 , and heavy components thereof were liquefied, which were returned to the decomposition vessel 2 by the pump 4 and subjected to the thermal decomposition treatment again.

The thermal decomposition treatment was continued for one hour after the temperature of the polyethylene pellets reached the decomposition temperature, and 80 g of oil in a container 8 was obtained. The oil obtained was composed of 20% by weight of a light fraction (boiling point less than 150 ° C), which corresponded to gasoline, 70% by weight of a medium fraction (boiling point 150 to 250 ° C), which corresponded to kerosene, and 10% by weight a wax component (boiling point greater than 250 ° C) composed.

Try 1 through 11

In each of these cases, the procedure of Experiment 1 was repeated, except that the values of the valve pressure set by the pressure control valves 6 and 7 and the temperature of the separation column 3 were changed as shown in Table 1. The results are shown in Table I.

Trial 12

The device of FIG. 1 was modified so that the separation column 3 , the pump 4 and the pressure control valve 6 were removed and the decomposition vessel 2 was connected directly to the control valve 7 . In the device with such a modified arrangement, the thermal decomposition treatment process before 100 g of polyethylene pellets was carried out at 450 ° C similarly to the above cases.

Table 1

As shown in Table 1, 80 g of oil was obtained in Experiment 2. However, the oil obtained is composed of 20% by weight of gasoline fraction, 60% by weight of kerosene fraction and 20% by weight of wax component. From the result of this experiment, it can be concluded that the degree of separation of the pyrolysis gas decreased due to the pressure inside the separation column 3 , which had been reduced to normal pressure, compared to experiment 1.

In addition, the results of Runs 3 and 11 indicate that when the valve pressure inside the decomposition vessel 2 is low, the yield of the oil recovered decreases and the amount of heavy components contaminating the oil recovered increases. It is clear from this result that the proportion of heavy components in the pyrolysis gas increases in accordance with the decrease in the pressure applied during the thermal decomposition process. Accordingly, it takes more time to sufficiently decompose the plastic into the components of a light fraction when the pressure applied is insufficient. On the other hand, the results of Experiments 4 to 6 show that the ratio of the light components in the pyrolysis gas increases in accordance with the increase in the pressure in the pyrolysis, so that the oil obtained becomes lighter. However, if too high a pressure is applied, the amount of low-boiling gas components which are not condensed in the cooling pipe of the recovery device part 5 increases , so that the yield of the oil obtained by the recovery device decreases.

The light fraction is contained in a high ratio in the oil obtained in experiment 7, but the yield of the oil obtained is low. In addition, in this case, the thermal decomposition reaction was not completed in one hour. Therefore, when the cooling temperature of the separation column 3 is lowered, it takes a long time to stop the decomposition reaction.

In trial 11 was despite a pyrolysis gas adapted Cooling and separation treatment the extracted oil due to a large amount of heavy ingredients Fraction contaminated. It is concluded that this Result occurs because of the amount of severe Components contained in the pyrolysis gas itself, and that it also occurs because of an insufficient Separation caused by the difficulty the heavy components under low pressure too condense. On the other hand, in experiment 12, the oil in high yield can be obtained during the Decomposition reaction of applied pressure. The oil obtained however, contained a large amount of the wax component and had a high viscosity because the pyrolysis gas was not subjected to the separation treatment and the heavy Components were not returned. In both cases it is not possible to remove the heavy components from the Remove pyrolysis gas sufficiently. Against it is over the results of experiments 1 to 10 in comparison with Experiments 11 and 12 clearly understand that the Combination of thermal decomposition treatment under increased pressure and the severing treatment of heavy Components from the pyrolysis gas to the unexpected significant effect that the proportion of heavy Components in the extracted oil is reduced.

Try 13 to 17

In each of these experiments, the procedure of Experiment 1 was repeated, except that the device was further equipped with the catalyst 11 in the separation column 3 , as shown in FIG. 2. The yield and content of the oil product obtained were then determined. The results are shown in Table 2.

Table 2

In each of Runs 13 and 14, where activated alumina and zeolite were used as Catalyst 11 , 80 g of oil containing no wax component was obtained. In both cases, the proportion of olefin components in the oil was reduced and the proportions of aromatic components and paraffin compounds are relatively increased.

In experiments 15 and 16, in which diatomaceous earth or silica were used as catalyst 11 , the effect of catalyst 11 was not present. In experiment 17, the ratio of the wax component increased when nickel oxide was used as catalyst 11 , and the oil yield was reduced. In each of these three cases, the proportion of olefin components was hardly reduced.

In view of these results, it is clearly understood that it is possible to improve the quality of the pyrolysis gas by using activated alumina or zeolite as the catalyst 11 , and a high quality fuel can be obtained.

2. Effects of alkali and water Trial 18

The device 1 of experiment 1 was modified so that the separation column 3 , the pump 4 and the pressure control valve 6 were removed and the decomposition vessel 2 made of glass was connected directly to the control valve 7 . Then the control valve 7 was adjusted to regulate the valve pressure at 0 kgf / cm ² , and 18 g of non-hard polyvinyl chloride (PVC) pellets with a particle size of 1 to 2 mm were put into the decomposition vessel 2 . Then, 18 g of sodium hydroxide as an additive was added to the PVC pellets, and the decomposition vessel 2 was continuously heated to a temperature of 450 ° C for one hour to thermally decompose the PVC pellets. As a result of the thermal decomposition, 4 ml of oil were obtained in the vessel 8 , this amount corresponded to 20% by weight, based on the amount of PVC pellets used. The product obtained was a light quality oil in which the fraction of the fraction distilled at a temperature above 250 ° C. is below 30% by weight and mainly contained benzene, octene and 2-ethylhexanol.

The oil obtained was further processed using a Ion chromatography with a detection limit of 1 ppm was examined, but neither sodium nor chlorine was found proven.  

Trial 19

The procedure of Run 18 was repeated, except that the same amounts of PVC pellets and sodium hydroxide as those in Run 18 were heated in the presence of 4 g of water in the decomposition vessel 2 to obtain the oil product. Then the yield and content of the oil obtained were determined in a similar manner. The results are shown in Table 3.

Try 20 to 38

In each of these runs, the procedure of Run 19 was repeated except that the type of plastic pellets, the type and amount of additive, and the amount of water to obtain the oil product in vessel 8 were varied. The yield and content of the oil obtained were then determined. The results are shown in Table 3. In Table 3, the respective amounts of the additive, water and oil product are shown by a number in parts by weight, based on the amount of plastic treated.

Table 3

Compared to experiment 18, the yield of the obtained oil product in experiment 19 drastically to 6 ml. In addition, the proportion of 2-ethylhexanol in the oil increased drastically. From these results is can be seen that the decomposition power for the in PVC resin contained plasticizer due to the addition of the Water can be improved so that the oil yield can be increased.

It is clear from the results of experiments 18 to 28 understand that when the alkaline material is applied the contamination of the oil obtained Chlorine compounds can be prevented.

In addition, the results of Experiments 29 to 31 show that it is possible to treat the PVC resin and the other non-PVC plastic containing no chlorine as a whole by the same pyrolytic decomposition method without causing any problem. However, when the amount of the alkaline material is in excess as in the cases of Experiments 32 and 33 , the oil obtained was rather contaminated with alkali and composed of heavy components, although contamination by the chlorine element can be prevented.

During the procedure of Experiment 35, phthalic acid, phthalic anhydride and the like, which crystallize on the wall of the recovery device 5 , were observed after the start of the decomposition treatment. In addition, the same phenomenon was also observed in experiment 36, but only after all of the water in the decomposition vessel 2 had evaporated. In both cases, the oil yield was low compared to Experiment 19. From these results, it can be seen that an alkali such as sodium hydroxide and the like, and the water have the effect of promoting the decomposition of the PVC resin. In Experiment 36, where 3 g (about 0.2 part by weight) of water had been initially added, 4 ml of an aqueous liquid was recovered after the thermal decomposition treatment was completed, and this aqueous liquid was acidic. Accordingly, the liquid obtained can be assumed to contain hydrogen chloride, phthalic acid, etc. In addition, in each of the experiments 35 to 38 in which the alkaline substance was not added, the oil obtained was contaminated with a large amount of some chlorine compounds such as chloroctane and the like, so that these products are not suitable for a fuel.

As described above, if the alkaline substance and the water to the plastic containing the PVC resin be added, the production of hydrogen chloride gas and the blocking phenomenon in the pipe system of the Pyrolysis device throughout the thermal Disintegration treatment of the waste plastic prevented will. In addition, the oil obtained has a good one Quality and contains no chlorine compound, and that Decomposition performance can also be improved.

It is also apparent that the polyvinyl chloride resin and the waste plastic containing no polyvinyl chloride resin can be treated under the same pyrolysis conditions in the presence of the water and the alkaline substance without taking a long time to obtain the oil product. Following this, the decomposition residue in vessel 2 can also be easily disposed of.

3. Effects of alkali and water under increased pressure Trial 39

The apparatus 1 of Experiment 1 was modified so that the separation column 3 , the pump 4 and the pressure control valve 6 were removed, and a closed type decomposition vessel 2 made of SUS F 304 stainless steel according to Japanese Industry Standard No. G3214, which was 8% nickel and 18% chromium contained, were directly connected to the pressure control valve 7 , the extraction device 5 and the vessel 8 . Then valve 7 was set to 1 atm valve pressure.

20 g of polypropylene pellets with a particle size of 2 mm, 1 g of sodium hydroxide and 2 g of water were placed in the decomposition vessel 2 . Then the decomposition vessel 2 was heated up to 420 ° C. and the water vapor in the decomposition vessel 2 was generated with increasing temperature. The heat treatment at a temperature of 420 ° C was continued for one hour, and the pressure inside the decomposition vessel 2 was adjusted to 1 atm by the pressure control valve 7 . After the heat treatment was completed, 20 ml of oil product was recovered, and the yield was 70% by weight based on the amount of the polypropylene pellet. The oil obtained mainly contained 2-methyl-1-pentene and 2,4-dimethyl-1-heptene. This oil can be classified as gasoline according to the following standards.

(Classification standards)

If the product contains at least 80% by weight of a fraction distilled at a temperature below or equal to 200 ° C and composed of substances, each of which has less than or equal to 11 carbon atoms, it is classified as gasoline; and
If the product contains at least 20% by weight of a fraction distilled at a temperature above or equal to 300 ° C and composed of substances, each of which has more than or equal to 13 carbon atoms, it is classified as a fuel oil.

Try 40 to 52

In each of these runs, the procedure of Run 39 was repeated except that the type of plastic pellets, the type and amount of additive and the amount of water to obtain the oil product in vessel 8 were varied. The yield and content of the oil recovered were then determined and the oil quality was classified according to the classification standards described above. The results are shown in Table 4.

Trial 53

The procedure of Experiment 39 was repeated, except that the material of the decomposition vessel 2 was made of a SUS F 410 martensitic stainless steel according to Japanese Industry Standard No. G 3214, which contained 0.14% nickel and 12.95% chromium. was modified to preserve the oil product. The yield and content of the oil obtained were then determined. The results are shown in Table 4.

Trial 54

The procedure of Experiment 39 was repeated, except that the material of the decomposition vessel 2 on carbon steel S 35 A according to Japanese Industry Standard No. G 3201, which is a mechanical structural material and contains neither nickel nor chromium, would be changed to obtain the oil product . The yield and content of the oil obtained were then determined. The results are shown in Table 4.

Table 4

Table 4 shows the respective amount of sodium hydroxide, Water and oil product indicated by weight percent based on the amount of plastic used.

Experiments 40 to 43 show that if the amount of Sodium hydroxide is less than 5 wt .-%, the Decomposition performance deteriorates, so that the yield of the oil product drops. Experiments also show 44 to 47 and 51 and 52 indicate that the components of the Oil product to a heavier molecular weight range because of the lack of water and low pressure are shifted during the pyrolysis process. From the The reaction system used in these experiments can be derived from the The above results are understood to be the preferred one Range of water more than or equal to 10% by weight and that of the valve pressure to be applied more than or equal to 1 atm. be.

On the other hand, in each of the experiments, this was 48 to 50 extracted oil classified as gasoline. From these Results can be immediately understood that, regardless on the type of plastic to be treated, it is possible is a light quality oil from a variety of Waste plastics through thermal decomposition of the Waste plastics in the presence of water and Extract sodium hydroxide under increased pressure. In the practical pyrolysis of waste plastic is too  expect the pyrolysis gas to have a larger amount heavy components due to the decomposition of a mixture contains various types of plastic materials. Therefore, even in such a case, an oil can be lighter Quality can be easily obtained by using the Applies pyrolysis process, which includes the step in which the heavy component is separated and returned. This is clearly evident from the results of the tests 1 to 10, which have already been explained above.

In each experiment 53 and 54, the material of the decomposition vessel 2 was changed to the martensite stainless steel and the carbon-containing steel. In both cases, a good quality oil can be obtained. However, the decomposition vessel 2 was seriously damaged. Therefore, these materials of the decomposition vessel 2 are not suitable for practical use in industry. In addition, these experimental results, compared to experiment 39, suggest that the stainless steel containing 8% nickel and 18% chromium can produce a catalytic effect for the decomposition reaction. Accordingly, the use of this steel material for the decomposition vessel 2 can improve both the corrosion resistance of the device and the recovery yield of the oil product.

4. Pyrolysis of plastic and thermosetting resin. Trial 55

First, 100 parts by weight of broken waste propylene was mixed with 10 parts by weight of broken waste sealing resin produced during the transfer molding encapsulation of a semiconductor device with the sealing resin. Then, using the device of Experiment 18, the mixture was put into the decomposition vessel 2 . The pressure control valve 7 was set to 0 kgf / cm ² valve pressure and the decomposition vessel 2 was heated to a temperature of 500 ° C for two hours. As a result, 80 parts by weight of oil was obtained, and the yield was 78% by weight based on the total weight (100 parts by weight) of waste propylene and a calculated amount (= 3 parts by weight / 10 parts by weight of sealing resin) ) organic compounds, ie epoxy resin, etc., which are contained in the waste sealing resin for semiconductor devices.

Try 56 to 58, 61 and 62

In each of these cases, the procedure of Experiment 55 repeated, except that the type of broken Waste plastic and the amount of sealing resin used Obtaining the oil product were varied. Then the Amount of oil extracted and the Extraction yield calculated. The results are in Table 5 given.

Try 59, 60, 63 and 64

In each of these cases, the procedure was repeated for each of Runs 55, 57, 61 and 62, except that the pressure control valve 7 was set to 3 kgf / cm ² and the Run 39 device was used to obtain the oil product. The amount of oil recovered was then determined and the recovery yield calculated. The results are shown in Table 5.

Table 5

As shown in Table 5, when the sealing resin with the broken waste propylene was mixed, the amount of extracted oil larger than that without Sealing plastic. So these results clearly demonstrate that the recovery yield of the oil by the addition of the Seal plastic can be improved.

In each case from Run 55 to 60, the oil obtained was composed of a fraction at 50 to 350 ° C. distilled. Given the results of experiments 1 through 10  these results teach sufficiently that in the Presence of the thermosetting silica-containing Plastic the waste plastic is effective in oil-like High quality gasoline can be transferred, namely using the process comprising the steps in which are heavy components from the pyrolysis gas separates and returns them.

Accordingly, in the presence of silicon dioxide containing thermosetting plastic such as the Sealing plastic for semiconductor devices thermoplastic waste plastics such as propylene and Like. Without causing any problem be pyrolytically decomposed, with an increase in Extraction yield of the oil.

5. Effects of heat transfer medium, Decomposition reaction catalyst and water Trial 65

In the device of experiment 18, the pressure control valve 7 was set to 0 kgf / cm ² valve pressure and 2 l of silicone oil was added to the decomposition vessel 2 as a heat transfer medium. Next, 1 kg of waste propylene plastic was broken into pieces about 2 cm in diameter, and they were added to the silicone oil in the decomposition vessel 2 . In addition, 1 kg of water and 100 g of nickel oxide as a catalyst were added to the silicone oil and the decomposition vessel 2 was closed. Then a small amount of waste plastic was burned within the decomposition vessel 2 to reduce the oxygen concentration in the decomposition vessel 2 to 15 vol%. Thereafter, the decomposition vessel 2 was heated to a temperature of 500 ° C for 2 hours. As a result, there was obtained 1.0 liter of oil, which can be classified as "Fuel Oil A" according to Japanese industry standards. At the same time, 100 cm ^{3 of} uncondensable gas and 100 cm ^{3 of} tar were obtained.

Try 66 to 84 and 89 to 92

In each of these cases, the procedure was experiment 65 repeated, with the exception that the type of Heat transfer medium, the type of Decomposition catalyst, the amount of water added and the type of waste plastic used to obtain the Oil product were varied as indicated in Table 6. Then the yield and quality of each oil product determined, the results are in Table 6-1 and 6-2 listed.

Try 85 to 88 and 93 to 96

In each of these cases, the procedures of each of Runs 65, 82 to 84, and 89 to 92 were repeated, except that the pressure control valve 7 was set to 3 kgf / cm ² valve pressure to obtain the oil product and the device of Run 39 was used were. The yield and quality of each oil product were then determined. The results are shown in Tables 6-1 and 6-2.

Table 6-1

Table 6-2

Comparing experiments 65 to 84 with experiments 89 to 92 can be understood that the use of each Component of the heat transfer medium, catalyst or Water clear effects to increase the yield of the Oil product and production of a light oil quality having. In addition, in experiments 65 to 84 the Reduced amounts of tar and uncondensable gas. Similar effects can also be seen from the results of Experiments 85 to 88, compared to experiments 93 to 96, be found out. Therefore, the effects of the Heat transfer medium, catalyst and water also in Case of pyrolysis can be achieved under increased pressure.

Accordingly, given the results described above immediately understand that in experiments 1 to 10 used pyrolysis processes a further improvement of Quality and yield of the oil product obtained is accomplished by doing that Heat transfer medium, the catalyst and the additive used as evidenced by those in Tables 6-1 and 6-2 specified attempts.

In addition, it must be clearly understood that the Pyrolysis process of the present invention obtained Product can be successfully used as fuel and without causing more problematic Air pollution because of its excellent oil quality less importance of the small amount of in it contained tar components.

Trial 97

In the pyrolytic decomposer 1 of Experiment 1, 100 kg of broken polypropylene plastic was put into the decomposition vessel 2 , and each of the pressure control valves 6 and 7 was set to a valve pressure of 4 kgf / cm ² . Then, the decomposition vessel 2 was heated to 420 ° C using kerosene as a fuel. Approx. The oil began to be extracted 30 minutes after the onset of heat. At this time, the supply of the kerosene was stopped and the oil obtained was supplied instead for heating the decomposition vessel 2 . After heating for 2 hours, the decomposition reaction was completed and the oil was obtained in a total amount of 80 kg. The amount of the oil used to heat the decomposition vessel 2 was 30 kg, and the amount of the kerosene initially used for 30 minutes was 10 kg.

Given this result, it is clear to understand that it is possible for pyrolytic decomposition to cover the necessary energy of the plastic materials, by part of the pyrolytic decomposition Extracted oil as an energy source for heating the Decomposition vessel of the pyrolytic decomposition device used.

Finally, it must be understood that the invention in in no way limited to the above configurations is and many changes to the above configurations can be performed without departing from the scope of the invention depart as set out in the appended claims is defined.

Claims (20)

1. A process for the pyrolytic decomposition of plastic, comprising the steps in which:
Thermally decomposes plastic in a pressurized atmosphere to produce a pyrolysis product;
separating the pyrolysis product obtained in the thermal decomposition step into a first fraction containing a relatively heavy component and a second fraction containing a relatively light component;
recycle the first fraction separated in the separation stage to the thermal decomposition stage; and
the second fraction separated in the separation stage wins in order to obtain a product obtained which is composed of the second fraction. 2. A pyrolytic decomposition process according to claim 1, characterized in that in the thermal decomposition stage of the plastic in The presence of alkali is thermally decomposed  is selected from the group consisting of alkali and alkaline earth metal hydroxide compounds. 3. The pyrolytic decomposition process according to claim 2, characterized in that the plastic contains polyvinyl chloride. 4. A pyrolytic decomposition method according to claim 1, characterized in that the valve pressure of the pressurized atmosphere in the thermal decomposition stage is within a range of 1 kgf / cm ² to 10 kgf / cm ² . 5. A pyrolytic decomposition process according to claim 1, characterized in that the plastic to a temperature within one Range from 300 to 600 ° C in the thermal Decomposition stage heated and the pyrolysis product a temperature within a range of 200 to 350 ° C are cooled in the separation stage, so that the first fraction separated from the second fraction by condensing it. 6. The pyrolytic decomposition process according to claim 1, characterized in that the plastic in the presence of water in the thermal decomposition stage is decomposed. 7. The pyrolytic decomposition process according to claim 1, characterized in that the plastic decomposes in the presence of a medium is that in the thermal decomposition stage in liquid state and a low one Reactivity regarding the plastic and the  Has pyrolysis product. 8. The pyrolytic decomposition process according to claim 1. characterized in that the plastic in the thermal decomposition stage in Is decomposed in the presence of a catalyst which is selected from the group consisting of Nickel oxide, iron oxide, cobalt (III) oxide, copper oxide, Manganese dioxide, silica, zirconium oxide and titanium dioxide. 9. A pyrolytic decomposition process according to claim 1. characterized in that the plastic in the presence of silicon dioxide in the thermal decomposition stage is decomposed. 10. A pyrolytic decomposition process according to claim 1, further comprising the step of:
converts an olefin compound contained in the pyrolysis product into an aromatic compound or a saturated compound. 11. A pyrolytic decomposition process according to claim 10, characterized in that in the transfer stage the olefin bond in Is converted to the presence of a catalyst which is selected from the group consisting of active Alumina and zeolite. 12. Apparatus for pyrolytic decomposition of plastic, comprising:
a decomposer part for thermally decomposing plastic in a pressurized atmosphere to produce a pyrolysis product;
a separator part for separating the obtained pyrolysis product into a first fraction containing a relatively heavy component and a second fraction containing a relatively light component;
a return device section for returning the first fraction to the decomposing device section; and
a recovery device section for recovering the second fraction to obtain a recovered product composed of the second fraction. 13. A pyrolytic decomposition device according to claim 12, characterized in that in the decomposer part of the plastic in Presence of alkali is selected, which is selected from the group consisting of alkali and Alkaline earth metal hydroxide compounds. 14. A pyrolytic decomposition device according to claim 13. characterized in that the plastic includes polyvinyl chloride. 15. Pyrolytic decomposition device according to claim 12, characterized in that the pressurized atmosphere is placed under a valve pressure of 1 to 10 kgf / cm ² . 16. A pyrolytic decomposition device according to claim 12.  characterized in that in the decomposer part of the plastic on a Temperature within a range of 300 to 600 ° C heated and in the separator part Pyrolysis product to a temperature within one Cooled range of 200 to 350 ° C so that the first fraction separated from the second fraction by condensing it. 17. A pyrolytic decomposition device according to claim 12. characterized in that in the thermal decomposer part of the Plastic is decomposed in the presence of water. 18. A pyrolytic decomposition device according to claim 12. characterized in that the decomposer part is a decomposition vessel of an iron alloy containing more than or 5% by weight of nickel and more than or equal to 10 Wt% chromium. 19. The pyrolytic decomposer of claim 12, further comprising:
a transfer device part for converting an olefin compound contained in the pyrolysis product into an aromatic compound or a saturated compound. 20. A pyrolytic decomposition device according to claim 19. characterized in that the transfer device part a catalyst contains, which is selected from the group consisting of made of active aluminum oxide and zeolite, and in Separator part is provided.