Plant for the thermal depolymerization of plastic waste

Abstract

Plant (1) for the thermal depolymerization of plastic waste, comprising a primary reactor (2) equipped with a heating device, an inlet (3) for feeding with plastic waste, an outlet (27) for discharge of an aerosol mixture of gaseous and liquid molecules and an outlet (5) for discharge of the solid residue, and the first condensation unit (4), which is equipped with the first primary vessel (10) and connected to the outlet (27) for discharge of the aerosol mixture of gaseous and liquid molecules from the primary reactor (2) and is equipped with the outlet (6) for the liquid fraction and the outlet (7) for the gaseous fraction, characterized in that it further includes a secondary reactor (8) which is equipped with a heating device and a catalyst and is connected to the first condensation unit (4) via the outlet (6) of the liquid fraction,and further includes the second condensation assembly (9) which is connected to the secondary reactor (8), wherein a siphon-like pressure barrier (26) placed in the first primary vessel (10) is arranged between the primary reactor (2) and the secondary reactor (8).

Description

Field of the ArtThe technical solution relates to the recycling sector, specifically to the plant for the thermal depolymerization of plastics wastes.The prior art to date has been knownThermal, or thermal, depolymerization is a process which serves to convert or decompose complex synthetic organic materials, usually from various hydrocarbon polymer-based waste materials, by the influence of the temperature effect on a mixture of simple short chain hydrocarbons having a maximum length of up to twenty hydrocarbons, or C20. Heating the materials in the anaerobic environment of the primary reactor produces a mixture of these simple liquid and gaseous hydrocarbons. The hot mixture is further cooled to precipitate and separate the low molecular weight gaseous and liquid hydrocarbons contained therein. In addition to the condensate, the thermal depolymerization also gives rise to a solid residue which can be used further. In known processes, however, the liquid fraction contains a heterogeneous mixture of low molecular weight hydrocarbons of nondefinable composition, which must subsequently be further modified in another external plant.In the single-stage thermal depolymerization, the starting raw material is heated to higher temperatures, namely up to 1000° C., which leads to the splitting of the macromolecular substances present in waste products into more stable low molecular weight liquid and gaseous fractions and to the release of volatile compounds. High reaction temperatures require significantly higher heating costs, so that the entire process is expensive. In the course of the depolymerization, a catalyst can be used which lowers the required reaction temperature. The catalyst is generally added continuously to the depolymerization process, which ensures its continuous and stable activity and thus uniform temperature conditions, which has a favourable effect on the uniform quality of the product. The catalyst lowers the reaction temperature of the conversion to temperatures in the range of 400 to 500°C depending on the starting material.The quality of the starting products, in particular of the gaseous and liquid fractions, is fundamentally influenced by some factors. One of the most important factors is the temperature and pressure in the depolymerization process. Typically, natural gas is mainly used for heating the reactor, but in most cases, generated process gases are used for heating the reactor. The use of flame heating complicates or completely eliminates the possibility of controlling the temperature and its accuracy. As a result, the material in the reactor therefore gradually "cakes" on its walls, as a result of which the heat transfer rate falls and frequent interruptions in operation occur, in which condensate deposits in the reactor have to be removed in a complicated manner. This phenomenon occurs just due to the large temperature difference in various parts of the reactor upon heating by the flame. At the location of the gas burner, the temperature of the reactor wall differs from other locations, usually on the order of tens of °C.The resulting liquid fraction, which can subsequently be used, for example, as liquid fuel, is a valuable raw material intended for further use in petrochemical, energy management, as a component in the production of fuels, in the production of new plastics, etc., but contains undesirable admixtures of waste products because the composition of the supplied waste raw material, which determines the quality of the starting product, cannot be completely controlled. This has the result that liquid products from known thermal depolymerization plants cannot be used universally, as are other clean fuels, since they are dependent on the own composition of the waste plastics material fed in.The gaseous fraction formed can be used as fuel in the process of heating the starting raw material or, if required, for power generation. After the waste material has been heated, the gaseous fraction, the so-called process vapours, is subjected to condensation in the first condensation plant, which results in its rapid cooling and liquefaction of the gaseous fraction collected in the container. Condensation frequently gives rise to problems associated with the so-called "intergrowth" of condensation pathways in coolers. This is because the above-described facts are related to the temperature and the pressure environment of the thermal decomposition process. Together with the inaccurate and unstable temperature and also the non-compliance with the correct pressure environment, known solutions in the reactor lead to an accidental evacuation of process vapors which contain a considerable proportion of heavier hydrocarbons, for example paraffins, waxes, the solidification point of which is close to 20° C.The object of the technical solution is therefore to provide such a plant for the thermal depolymerization of waste plastics which would eliminate the above-mentioned disadvantages, in which it would not meshing with any intergrowth of the reactor walls by caking waste plastics and with no intergrowth of the condensation paths in coolers which would effectively decompose the waste plastics in any desired starting composition in the formation of a mixture of liquid hydrocarbons having the required length range of the hydrocarbon chains, which is stable and independent of the composition of the fed mixture of plastics.Nature of the Technical SolutionThe object set is achieved by a plant for the thermal depolymerization of waste plastics material according to this technical solution. The plant includes a primary reactor equipped with a heating device, an inlet for the charging of the waste plastics material, an outlet for the discharge of an aerosol mixture of gaseous and liquid molecules, an outlet for the removal of solid residues, and the plant further includes a first condensation assembly equipped with a first primary container and connected to an outlet for the discharge of an aerosol mixture of gaseous and liquid molecules from the primary reactor and equipped with an outlet for the liquid fraction and an outlet for the gaseous fraction.The essence of the technical solution is that the plant further includes a secondary reactor equipped with a heating device and a catalyst and connected to the first condensation assembly via the outlet of the liquid fraction, and the plant further includes a second condensation assembly connected to the secondary reactor. Between the primary reactor and the secondary reactor in the first primary container, a siphon-like pressure barrier is arranged, where different pressure conditions prevail slightly. The plant is thus equipped with a two-stage condensation, wherein the liquid crude fraction from the first condensation unit enters the first primary container and the liquid end product is collected in the second primary container.In the primary reactor, the polymer chains of the waste plastics material are chemically cleaved to form simple free radicals. The effect of the thermal energy supplied reaches the limit of the thermal stability of individual chemical bonds of synthetic and fossil organic materials. This results in a short-term decomposition or in the cleavage / dissociation of all covalent chemical bonds up to the individual atoms of the elements present. These are therefore primarily organogenic elements, but also heterogeneous elements in the form of free radicals. The effect of the thermal energy of the individual temperature zones of the primary reactor, in which the process temperature preset in a nonlinear manner is strictly maintained and the pressure environment is also controlled, results in subsequent chemical association reactions of free radicals, in which new molecules are formed in the gaseous and liquid state in the aerosol mixture of gaseous and liquid molecules.The starting raw material, i.e. a mixture of different types of waste plastics, contains chemically, in addition to organic elements, also other heterogeneous elements. These heterogeneous elements are contained in the chemical additives used, which refine the physical properties of the final product made of plastic. Heterogeneous elements may also be present as an admixture in the waste plastics material. These are mainly dyes. These additives and admixtures are various elements or chemical compounds of organic or inorganic origin. These are, for example, metal oxides, e.g., oxides of iron Fe and copper Cu in the case of dyes, and further, for example, aluminum Al, bromine Br as a component of a combustion retarder, silicon Si for crosslinking a chemical bond to increase the strength of the polymer, etc.During the dissociation process, these heterogeneous inorganic compounds are cleaved in the primary reactor to form free radicals and thus affect subsequent chemical association reactions. Metal radicals act in particular as catalysts in this phase. Considering their molar mass, these metal radicals do not leave the primary reactor as a constituent of an aerosol mixture of gaseous and liquid molecules through the evacuation fitting, but associate to a solid state and become the constituent of a solid carbon residue and are continuously discharged outside the primary reactor.The process parameters chosen for the primary reactor force free radicals of halogen elements, if these elements are present in the starting material, to form oxygen-free acids in gaseous form, for example hydrochloric acid HCl, hydrofluoric acid HF, etc., and also free radicals of sulphur, for example in the form of gaseous hydrogen sulphide H 2 S. These acidic constituents are separated from the aerosol mixture by a sorption process at the outlet of the gaseous fraction.In a convenient embodiment, the first condensation assembly includes a first unit of the first condensation assembly constituted by a cooled evacuation fitting and connected to the primary reactor, and a second unit of the first condensation assembly provided with a first primary container and an outlet of the gaseous fraction. The aerosol mixture of gaseous and liquid molecules described above is fed through the evacuation fitting into the first condensation stage and the mixture is cooled here in the first cooling process abruptly to a temperature of about 80° C. This mixture is then fed to the second unit of the first condensation assembly. The condensation results in separation of the gaseous and liquid fraction and in effective precipitation of the droplets of the process liquid or liquid fraction which flows into the cooled first primary container, where the crude liquid fraction is cooled to a temperature of about 40° C. The recovered crude liquid fraction is fed from the first primary container to the secondary reactor via a siphon-like separation pressure barrier.In a favorable embodiment, the secondary reactor is equipped at its inlet with a preheating unit with a preheating chamber, in which an exchange basket for placing the catalyst is arranged. In this part of the plant, the cooled crude liquid fraction coming from the first primary vessel is heated to 300°C. The influence of heat results in a controlled physicochemical reaction under the action of the catalyst, which has a short-term effect on the properties of the liquid condensate. In the liquid fraction, there occurs a rapid chemical dissociation of chemical bonds and their subsequent rapid association in the preheating chamber.The secondary reactor consists of two series stages arranged one behind the other, the first stage of the secondary reactor being connected to the preheating chamber. This physicochemical process makes it possible to obtain the desired spectrum of liquid hydrocarbon molecules having a boiling temperature of about 250° C. and a limit value for the number of carbons in the molecule of max. C14 or tetradecane. This newly formed mixture of aerosol droplets is then fed to the series stages of the second condensation assembly and then to the cooled second primary container.In a convenient embodiment, the second condensation assembly includes a first unit of the second condensation assembly connected to the secondary reactor and a second unit of the second condensation assembly provided with a second primary vessel and with an outlet of the liquid recycle.Inside the preheating unit in the preheating chamber is an exchange basket with a catalyst immersed in a hot bath of crude liquid fraction. The catalyst is a mesoporous material for heterogeneous catalytic reactions, with the advantage of zeolite, through which the liquid fraction passes through the capillaries of the catalyst, thereby affecting its properties.Zeolites are crystalline inorganic microporous materials based on aluminosilicate having an exactly defined rigid three-dimensional structure whose basic building block SiO 4- and AlO 4- are tetrahedrons. Individual tetrahedrons are linked to one another via common bridge oxygens. The amount of AlO 4- tetrahedrons is determined by the negative charge of the lattice, which is balanced by protons outside the lattice or inorganic / organic cations. The Si / Al value determines, for example, azidobasic properties and ion exchange capacity.The main advantage of zeolites is the well-defined structure of microporous channels, wherein the cavitation size of the "entrance window" of the channel structure of zeolites in individual types of zeolites is usually in the range between 0.3 and 1.2 nm and is determined by the number of Si and Al atoms in the ring of the channel structure and the geometry of the channel structures. An important property of zeolites is the possibility of targeted modification of active sites, which can be achieved by changing the chemical composition or by post-treatment of the synthesis. Zeolites are thermally stable materials with high adsorption capacity, which are moreover harmless to the environment.For plant use, an important property of this catalyst is that it does not allow the effective course of reactions of molecules larger than the dimension of the channel structure of the zeolite. Larger molecules cannot penetrate the channel structure and therefore cannot react at most active sites located within the pores.Zeolites in the secondary reactor therefore act as catalyst and not as sorbent, i.e. they do not sorb chemical material on their surface, do not enter into a chemical reaction and are therefore not consumed. Zeolites act because of their physicochemical properties, namely because of the size of their capillaries and because of their electronegativity. Electronegativity is a property of an atom and expresses its ability to attract binding electrons. The electronegativity of an atom is influenced by its atomic number and the distance of the valence electrons from the charged nucleus. The electronegativity of each element or compound is given by its atomic arrangement.The crude liquid pyrolysis fraction will normally contain a substantial amount of alkenes and cycloalkenes, i.e., double-bonded hydrocarbon compounds, or other chemical bonds with heterogeneous elements. A higher occurrence of these bonds is undesirable for purposes of chemical recycling and for the later use of liquid recycle. Therefore, the liquid is subjected to the action of a catalyst or the action of its electronegativity, which, upon reaching an appropriate temperature, cleaves these C=H double bonds into the "sigma"-Σ bond and the "pi"-π bond, and generates simple C-H alkane bonds and a short chain. Electronegativity acts on the weaker "pi"-π bond which breaks down as short hydrocarbon chains are formed.The secondary reactor is advantageously equipped at its outlet with a separation vessel and a closed return circuit for returning unused molecules to the primary reactor for their reprocessing. Unused molecules are understood to mean more complex molecules with a higher carbon number than the required range, polycyclic aromatic hydrocarbons and also possible molecules with a content of heterogeneous atoms which remain in the separation vessel of the secondary reactor, from where they are pumped automatically back to the primary reactor on the basis of the measurement of their fill level in a closed return circuit. These molecules are again subjected to dissociation processes in the primary reactor and the undesired heterogeneous elements are repeatedly forced to finally become part of the inert residue or solid residue or the gaseous fraction, from where they are subsequently separated.The plant for heating the primary reactor is preferably a multizone device with infrared electric heating elements controlled separately by electronic thermostats. In a favorable embodiment, the secondary reactor is additionally equipped with a heating device, which is likewise a multizone device with electrical resistance bodies and precise electronic thermostat control. The electrical resistance device is provided for a low-temperature process, generally up to 350° C., with which the temperature can be controlled with an accuracy of 0.1° C. The electrical infrared device is intended for so-called medium temperature processes, usually up to a temperature of 850° C. This method provides a fast, "hard" and stable thermal energy source with the possibility of precise temperature control and stability with an accuracy of 0.5° C. Electrical infrared heating is significantly more efficient compared to resistance heating. The inexclusive advantage of this type of heating with infrared heaters is the penetration of thermal radiation through the wall of the primary reactor, it depth-acts, and heats the material inside the reactor, including the slow speed screw mechanism installed inside the primary reactor. Heating the internal mechanism of the primary reactor increases the input power of the plant and the efficiency of the thermal decomposition process. The inner slow-running mechanism provides for the advancement of the waste plastics inside the primary reactor and ensures its self-cleaning effect.Stable pressure conditions in the plant are generated by a blower with electronically controlled rotational speed as a function of the current pressure, which is detected via a sensor on the primary reactor. The blower represents the terminal and a component of the system of a multistage alkaline scrubber of the gaseous fraction. The blower assists gas passage through the individual stages of the multistage alkaline scrubber system of the gaseous fraction depending on the set level of pressure conditions in the primary reactor. This stable printing environment is reliable and positively affects the process of thermal decomposition of long organic chains. An ideally set and maintained pressure environment in the primary reactor makes it possible for the liquid and gaseous molecules produced to leave the primary reactor space quickly through the evacuation fitting, and thus prevents secondary thermochemical reactions in which more and more and less complex organic molecules are produced, which have a negative effect on the quality of the liquid fraction. Together with these "selected" liquid hydrocarbon molecules in the form of aerosol droplets which are entrained in the gas mixture, molecules of CO, CO 2, H 2 and molecules of any undesired constituents of organic compounds, for example of chlorine, fluorine or sulfur, in the gaseous state, for example HCl, HF or H 2 S, are also evacuated from the primary reactor space.At the outlet of the gas fraction from the second unit of the first condensation assembly there is advantageously arranged a system of the multistage alkaline scrubber of the gaseous fraction, which is equipped with a clean process gas outlet, the end part of which is an electronically controlled blower, which then forces the clean process gas into the external parts of the plant, which can be, for example, a low pressure membrane gas container, a compressor station or an energy block formed by a gas turbine or a combined heat and power coupling for generating electrical and thermal energy. The recovered process gas or gaseous fraction which is effectively freed from the liquid fraction in the first condensation assembly is a mixture of gaseous hydrocarbons, hydrogen, carbon monoxide CO and carbon dioxide CO 2, normally about 1%, depending on the presence of plastics in the mixture of fed waste plastics with oxygen content in its molecules and on the strict compliance with anaerobic conditions inside the primary reactor, but also of undesired additions of sulphur compounds and some halogens, in particular chlorine and fluorine in minimal amounts, as far as these elements are present in the starting raw material. A system of the multistage alkaline scrubber of the gaseous fraction uses chemical solution fills tailored to effectively sorb these potentially hazardous gas fraction components. Here, chemical reactions take place in which the readiness of the halogen elements for chemical formation of salts is utilized. The same applies to the case of sorption of sulfur compounds. Depending on the degree of emptying, the chemical fills are exchanged approximately four times a year in the context of periodic shutdowns of the plants. The waste here is harmless and usable salt.The process gas or the gaseous fraction is then dried after the alkaline scrubber system. Pure process gas can be used safely as non-hazardous fuel for driving a turbine or a combined cycle heating and power plant for power generation, which substantially or completely covers the energy requirement for the operation of the plant. The operation of combustion gas turbines represents a higher degree of air protection safety, taking into account the high temperatures in the combustion chamber of approximately 1000° C.In a favorable embodiment, the plant further closes a cooling unit of the plant, i.e. a high-performance air-water heat pump and a bus of the cooled medium. The cooling unit of the plant is connected from the bus of the cooled medium via electronically controlled circulation pumps to the components of the plant which have to be cooled for process and safety reasons. Such components of the plant are the inlet for the feed of the waste plastics material or the continuous filling system of the primary reactor, the solid residue cooling unit, the first condensation assembly, the second condensation assembly, the first primary container and the second primary container.The advantages of the plant for the thermal depolymerization of waste plastics according to this technical solution consist in particular in the fact that this technical solution does not lead to any blockage of the reactor walls by caking waste plastics and to no intergrowth of the condensation paths, and is capable of effectively decomposing the waste plastics in any desired starting composition in the formation of a mixture of liquid hydrocarbons having the required length range of the hydrocarbon chains, which is stable and independent of the composition of the fed mixture of plastics.Explanation of the DrawingsThe technical solution mentioned is explained in more detail in the following figures, where: FIG. 1 is a schematic view of the system, FIG. 2 shows the diagram of the secondary reactor with the connection to the primary reactor.Example of realization of technical solutionThe schematic of the plant 1 for the thermal depolymerization of waste plastics material is shown in FIG. 1. The mixed waste plastics material is comminuted to the required fraction prior to entering the plant 1 and the waste plastics material is pneumatically conveyed to the large capacity hopper 22, which automatically continuously meters the waste plastics material into the large capacity container and from there via a cooled continuous screw conveyor to the inlet 3 for charging the primary reactor 2 with the waste plastics material. The primary reactor 2 is filled by a continuously cooled screw extruder into the filler neck 3 for the charging with plastic waste. The specific geometry of the screw and the structural elements of the connection of the extruder to the primary reactor 2 ensure an effective compression of the input material and the air discharge against the flow direction of the waste material. The filling process is self-cleaning and maintenance-free and thus creates a natural and reliable barrier against the penetration of air into the space of the primary reactor 2. the supply of waste material from the large-capacity hopper 22 and the filling with the screw extruder take place fully automatically by an PLC system which reacts in real time to information about the amount of material in the primary reactor 2.The primary reactor 2 has a volume of 1700 l and is made of stable titanium-alloyed steel which resists high operating temperatures and chemically aggressive environments. The primary reactor 2 is capable of processing up to 700 kg of dry comminuted plastics mixture per hour. For tyres having a higher so-called bulk density, a performance of up to 1000 kg per hour can be achieved.After heating the waste plastics in the anaerobic environment (without access to oxidants) of the primary reactor 2, the polymer chains are chemically cleaved when free radicals of the elements present are formed, whereby simpler molecules are formed in the association phase of the process. These molecules, in the form of an aerosol mixture of gaseous and liquid molecules, leave the primary reactor 2 through the outlet 27 for discharge of the aerosol mixture of gaseous and liquid molecules through the evacuation fitting into the first condensation assembly 4, which forms the first cooled stage of the first condensation, namely the first unit 4A of the first condensation assembly 4, and then enter the second cooled stage of the first condensation, namely the second unit 4B of the first condensation assembly 4. The solid carbon residue is discharged through the outlet 5 for discharging the solid residue, which contains, in addition to the inorganic form of the carbon, which is largely contained in this solid mixture, also nondegradable mechanical impurities, which may be present in the waste plastic mixture from the beginning, and metals or other binders and fillers, such as glass fibers, talc, quartz sand, etc., which form a layer or composite unit with the plastic, and other chemical compounds and substances which have already been used as additives in the production of original plastics, such as dyes, retarders, filters, etc. This solid residue constitutes about 5 percent by weight of the input power of the plant 1. Considering the fact that the mixture of waste plastics may contain different proportions of the above components, the proportion of 5% is only a guideline but yet expresses the average value of the initial balance in the case where one of the additives does not exceed the normal limit.A screw conveyor press is furthermore connected to the cooling unit 23 of the solid residue to the outlet 5 for discharging the solid residue from the primary reactor 2, from which the cooled solid residue is continuously discharged via the outlet 24 of the cooled residue to the outlet 15 of the solid residue outside the plant 1.The aerosol mixture of gaseous and liquid molecules leaves the primary reactor 2 through the evacuation fitting, which is at the same time the first unit 4A of the first condensation assembly 1 and is cooled abruptly here to 80° C. It then passes to the second unit 4B of the first condensation assembly 4, in which liquid condensate is separated from the gaseous fraction at a temperature of 40° C. with high efficiency. The gaseous fraction is fed through the pipe of the gaseous fraction outlet Z to the system 12 of the multistage alkaline scrubber of the gaseous fraction, the end part of which is an electronically controlled fan, which then forces the pure process gas through the pipe of the pure process gas outlet 13 into the external components of the plant, which may be, for example, a low pressure membrane gas vessel, a compressor station or an energy block formed by a gas turbine or a combined heat and power coupling for generating electrical and thermal energy. The liquid fraction is fed into the cooled first primary container 10, the constituent of which is a siphon-like pressure barrier 26. This pressure barrier 26 separates the surroundings of the primary reactor 2 and the secondary reactor 8, where different pressure conditions prevail slightly. From the first primary container 10, the cooled crude liquid condensate is fed to the secondary reactor 8 through the pipe line of the outlet 6 of the liquid fraction by means of a gear pump.The pressure in the primary reactor 2 varies in the range between -0.02 bar and +0.15 bar. Compliance with this ideal pressure range is ensured in real time by the electronic control of the blower on the basis of the pressure sensor in the primary reactor 2. In this printing environment, undesirable secondary association reactions do not occur, in which an amorphous mixture of higher saturated aliphatic hydrocarbons in the form of paraffins or esters of higher fatty acids can form. The formation of these undesirable higher hydrocarbons can lead to a gradual intergrowth of the evacuation fitting, or further traps, up to the first primary container 10. The primary reactor 2 with the accessory of the screw mechanism and all the seals in the plant 1 are designed for a safe pressure in the range of -1 bar to +1 bar. Safety elements are also set to this limit value, which, when exceeded, result in the activation of the shutdown sequence of the installation 1 and its safe shutdown.The natural atmospheric pressure is maintained in the secondary reactor 8 and in its associated parts by means of a membrane bag which separates the interior of the secondary reactor 8 from the external environment and prevents possible fugitive emissions into the atmosphere.The secondary reactor 8 with the accessory is shown in Fig. 2 and it includes a preheating unit 19, a preheating chamber 20, the secondary reactor 8 itself, a second condensation assembly 9, a second primary tank 11 and a separation tank 25 and may collectively be called a secondary circuit of the plant 1. In the secondary circuit of the plant 1, the cooled crude liquid fraction from the first primary container 10 is heated again, wherein a controlled physicochemical reaction, i.e. accelerated controlled chemical dissociation of the chemical bonds of liquid molecules and subsequent rapid association, takes place again. At its inlet, the secondary reactor 8 is equipped with a preheating unit 19 with a preheating chamber 20 in which is placed an exchange basket 21 with a catalyst immersed in a hot bath of crude liquid condensate. In the preheating unit 19, the liquid crude condensate coming from the primary reactor 2 is heated again to a temperature of 300° C. The catalyst is a mesoporous material for heterogeneous catalytic reactions, zeolite, through which the liquid fraction passes through the capillaries of the catalyst, thereby affecting its properties.From the preheating chamber 20, hot condensate vapors are fed to the secondary reactor 8, which consists of two stages in which the reaction temperature is held thermostatically at 250° C. In this environment, a physicochemical process takes place which allows the formation and development of the required spectrum of liquid hydrocarbon molecules with a boiling point of about 250°C and a reduction to the maximum carbon number in the molecule max. C14 (tetradecane). This newly formed mixture of aerosol droplets is then fed to the series stages of the second condensation assembly 9, namely the first unit 9A of the second condensation assembly 9 and the second unit 9B of the second condensation assembly 9, the pure condensate then flows into the cooled second primary container 11, the final product being conveyed through the pipe of the outlet 14 of the liquid recycle to the external secondary container for shipment.More complex and heavier molecules with a higher carbon number than the required range, polycyclic aromatic hydrocarbons and possible molecules with heterogeneous atoms are collected by gravity in the separation vessel 25, which is a constituent of the secondary reactor 8. This heavy separated fraction is pumped automatically from the separation container 25 by the gear pump through the pipeline of the closed return circuit 18 back into the primary reactor 2 on the basis of the fill level measurement. This heavy liquid fraction is again subjected to dissociation processes in the primary reactor 2 and the undesired heterogeneous elements are repeatedly forced to finally become part of the solid residue of the inert residue or of the gaseous fraction, from where they are subsequently separated.In the gas mixture, CO, CO 2- and H 2- molecules, but also molecules of any undesirable compounds, for example chlorine, fluorine in the gaseous state, for example HCl, HF or, possibly also in the form of chlorine or fluorine derivatives of hydrocarbons, are evacuated from the space of the primary reactor 2a, provided these elements are present in the starting mixture of the waste plastic. These possible acidic process gas components are reliably removed by a system 12 of the multistage alkaline scrubber of the gaseous fraction. Here, chemical reactions take place in which the readiness of the halogen elements for the formation of salts is utilized.By means of liquid and dry sorbents, any unwanted impurities are removed from the process gas mixture with high efficiency. An alkaline wet scrubber removes with high efficiency any organic compounds of the halogen elements, in particular of chlorine, bromine and fluorine, and any organic sulfur compounds present.In the described I-stage of the alkaline scrubber, a salt mixture is thus formed according to the following chemical equations: H 2 S+2NaOH→Na 2 S+2H 2 O HCl+NaOH→NaCl+H 2 OThis mixture of harmless sodium sulfide and sodium chloride (edible salt) is periodically changed after three months, or after the pH of the alkaline washing solution has decreased below pH 8, within the framework of maintenance work on the technique to be carried out, and is transported away through an authorized location for disposal.The next stage of the system 12 of the multistage alkaline scrubber of the gaseous fraction is a closed reaction vessel with a solution of KOH in demineralized water in a volume of 25 litres and serves as a protective preventive barrier in the case of an unpredictable higher presence of sulphur or compounds of halogen elements in the input material. The contents of the reaction vessel are also changed within the scope of maintenance work to be carried out on the industry after twelve months, or after the pH of the alkaline washing solution has dropped to ≤8, and are transported away through an authorized location for disposal.The III and IV stages of the system 12 of the multistage alkaline scrubber of the gaseous fraction contain a dry sorption filling of crystalline sulphur dioxide, which is usually used for the purification of drinking water, respectively of zeolite-based crystalline sorbent and a sorption filling of activated carbon, both fillings in a volume of about 50 litres, where the periodic change after 6 months in operation of the technology is presumed in a similar manner to the fillings of the I and II stages.In the plant 1, the standard equipment of the multistage alkaline scrubber system 12 includes the gaseous fraction which preventively effectively prevents possible leakage of organic compounds of sulfur, chlorine or organic compounds of other halogen elements. The installed system 12 of the multistage alkaline scrubber of the gaseous fraction, after the description of the above chemical processes, effectively traps these possible corrosive constituents of the process gas.The possible presence of halogen elements and sulphur in the input mixture of waste materials does not represent a potential risk for the environment. Due to the strict compliance with all process conditions, these pollutants always pass into the gaseous state, for example in the form of gaseous HCl, HF or H 2 S, in the thermochemical recycling process, and from there they are reliably removed in the system of multistage cleaning and processing of the process gas by the chemical reaction into the form of harmless salts.The cooling of the plant 1, or of its necessary parts, is ensured by the cooling unit 16, which is a powerful air-water heat pump, which supplies the bus 17 with the cooled medium. The cooled medium is connected from the cooled medium bus 17 via electronically controlled circulation pumps to the components of the plant 1, which must be cooled for process and safety reasons. Such components of the plant 1 are the system of continuous filling of the reactor as part of the large capacity hopper 22, the cooling unit 23 of the solid residue, the first condensation assembly 4, the second condensation assembly 9 and the first primary container 10, the second primary container 11.The modules of the plant 1 where the primary reactor 2, the secondary reactor 8 and the first condensation assembly 4 and the second condensation assembly 9 are installed are equipped with an automatic extinguishing device and with a system for detecting combustible and hazardous gases.In the electronic control system of the plant 1 developed by the author, the conditions of the safety shutdown sequence are permanently programmed, which is automatically activated when an operating anomaly is detected, which the control system cannot self-remedy, e.g.: shutdown of the electrical protection of one of the consumers of the plant 1, the inability to reach the operating temperature of the primary reactor 2 or of the secondary reactor 12 due to a heating failure, when CH 4 or CO is detected in the module of the primary reactor 2, or when condensation is above the set safe concentration limit, the detection of CH 4 or CO, even at a minimum concentration, is reported to the operator and a warning acoustic and light signal is triggered, when the overpressure is generated and when the set pressure limit value is exceeded in the interior of the primary reactor 2 or the secondary reactor 12, the condensation assembly 6 or the first primary container 13, when the temperature in the interior of the primary reactor 2 or the first condensation assembly 4 is increased above the set limit value, when the cooling unit 16 malfunctions.The installation 1 is equipped with an electronic backup battery source which completely covers the energy requirement of all installed safety systems and the energy requirement during the activation and execution of the safety shutdown sequence with sufficient reserve. The operation of the plant 1 is fully automatic.Application Options in the IndustryThe thermal depolymerization equipment of waste plastics according to this technical solution can be used for recycling all waste plastics, including, among others, tyres, the disposal of which is costly and complicated.Overview of the Reference Numerals1 Plant 2 Primary reactor 3 Filler neck for charging with plastic waste 4 First condensation assembly 4A First unit of the first condensation assembly 4B Second unit of the first condensation assembly 5 Outlet for discharging the solid residue 6 Outlet of the liquid fraction 7 Outlet of the gaseous fraction 8 Secondary reactor 9 Second condensation assembly 9A First unit of the first condensation assembly 9B Second unit of the second condensation assembly 10 First primary container 11 Second primary container 12 System of the multistage alkaline scrubber of the gaseous fraction 13 Outlet of the pure process gas 14 Outlet of the liquid recycle 15 Outlet of the solid residue 16 Cooling unit of the plant 17 Bus of the cooled medium 18 Return circuit 19 Preheating unit 20 Preheating chamber 21 Exchange basket 22 Large-capacity hopper 23 Cooling unit of the solid residue 24 Removal of the cooled residue 25 Separation container 26 Pressure barrier 27 Outlet for removing an aerosol mixture of gaseous and liquid molecules

Claims

Plant (1) for the thermal depolymerization of waste plastics, comprising a primary reactor (2) equipped with a heating device, an inlet (3) for charging waste plastics, an outlet (27) for discharging an aerosol mixture of gaseous and liquid molecules and an outlet (5) for discharging the solid residue, and the first condensation assembly (4) equipped with the first primary container (10) and connected to the outlet (27) for discharging the aerosol mixture of gaseous and liquid molecules from the primary reactor (2) and equipped with the outlet (6) of the liquid fraction and the outlet (7) of the gaseous fraction, characterized in that it further includes a secondary reactor (8) equipped with a heating device and a catalyst and connected to the first condensation assembly (4) via the outlet (6) of the liquid fraction, and further including the second condensation assembly (9) connected to the secondary reactor (8), wherein between the primary reactor (2) and the secondary reactor (8) a siphon-like pressure barrier (26) placed in the first primary container (10) is arranged.The plant (1) according to claim 1, characterized in that the secondary reactor (8) is equipped at its inlet with a preheating unit (19) with a preheating chamber (20), in which an exchange basket (21) for placing the catalyst is arranged.The plant (1) according to claim 1 or 2, characterized in that the catalyst is a zeolite.The plant (1) according to any one of claims 1 to 3, characterized in that the secondary reactor (8) is equipped at its outlet with a separation tank (25) to which a return circuit (18) for returning unused molecules to the primary reactor (2) for its reprocessing is connected.The plant (1) according to any one of claims 1 to 4, characterized in that the first condensation assembly (4) includes the first unit (4A) of the first condensation assembly (4) consisting of an evacuation fitting connected to the primary reactor (2) and of the second unit (4B) of the first condensation assembly (4) equipped with the first primary container (10) and the gaseous fraction outlet (7).The plant (1) according to any one of claims 1 to 5, characterized in that the second condensation assembly (9) includes the first unit (9A) of the second condensation assembly (9) connected to the secondary reactor (8) and the second unit (9B) of the second condensation assembly (9) equipped with the second primary tank (11) and the outlet (14) of the liquid recycle.The plant (1) according to any one of claims 1 to 6, characterized in that the secondary reactor (8) consists of two series stages arranged one behind the other, wherein the first stage of the secondary reactor (8) is connected to the preheating chamber (20).The plant (1) according to one of claims 1 to 7, characterized in that the plant for heating the primary reactor (2) is an electrical plant with infrared temperature elements.The plant (1) according to any one of claims 1 to 8, characterized in that the plant for heating the secondary reactor (8) is an electrical plant with resistance temperature elements.The plant (1) according to any one of claims 1 to 9, characterized in that at the gaseous fraction outlet (7) a system (12) of the multistage alkaline scrubber of the gaseous fraction is arranged, which is equipped with an outlet (13) of the pure process gas.The plant (1) according to any one of claims 1 to 10, characterized in that it further includes the cooling unit (16) of the plant (1) and the cooled medium bus (17), to which cooled medium bus (17), by means of electronically controlled circulation pumps, the inlet (3) for supplying waste plastics, the solid residue cooling unit (23), the first condensation assembly (4), the second condensation assembly (9), the first primary container (10) and the second primary container (11) are connected.

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