Process and related plant for producing pyrolysis oil containing liquid hydrocarbons from plastic materials with high heat generation efficiency

Abstract

This process is for the sustainable production of pyrolysis oil containing liquid hydrocarbons from plastic materials, preferably waste materials. The process is characterized by the use of solar radiation to heat a heat transfer fluid (such as molten salt) at multiple temperature levels for use in a pyrolysis device requiring higher temperatures. The heat transfer fluid returning from the device is sent back to the respective solar radiant heater, thereby closing the loop. The process is therefore characterized by having at least two loops of heat transfer fluid. The plastic material enters a first pyrolysis reactor, heated at a moderate temperature by a first thermal fluid containing molten salt. The generated gas is then transferred to a second pyrolysis reactor, heated to a higher temperature by a second thermal fluid also containing molten salt. The unique setup of the process and associated plant, which synergistically exploits the special properties of the pyrolysis process and the solar collector, allows for high exergy efficiency. In particular, the present invention takes advantage of the fact that pyrolysis is carried out in two stages: the first stage requires a large amount of energy but at a moderate temperature. Only the second stage requires a high-temperature energy source, which requires a high concentration of solar energy; however, the pyrolysis process devised requires only a small amount of energy in this stage. This maximizes the yield of the process in terms of the resulting product (amount of pyrolysis oil per solar radiant power).

Description

[Technical Field]

[0001] The present invention relates to a sustainable process for producing pyrolysis oil containing liquid hydrocarbons from plastic materials, preferably waste materials.

[0002] It is applied in the field of pyrolysis of plastic materials to produce pyrolysis oil containing hydrocarbons, which can be further processed and then converted into monomers useful for the production of polymers, thus closing the loop.

[0003] In the chemical industry, and especially in the polymer industry, it is becoming increasingly strategically important not only to recycle polymers but also to do so sustainably. Indeed, a "closed-loop" recycling process that is "closed" from a material perspective but not from an energy perspective (i.e., using fossil fuels, or ultimately energy derived primarily from that source) is not truly closed, especially considering the very large amounts of heat energy required for the pyrolysis process. As a result, the carbon footprint can become so large that it undermines the effectiveness of the entire recycling loop and makes the process no longer useful.

[0004] An integrated solution such as the one proposed now not only enables the use of "green" energy but also maximizes its effectiveness. This efficiency gain is significant considering that low solar radiation and the high concentration factor required dictate a high land surface area per unit of pyrolysis oil produced.

[0005] However, the processes that make it possible to close the plastics loop, and are therefore highly desirable, require large amounts of thermal energy at high temperatures. Traditionally, for this purpose, the combustion of natural gas and / or electricity is used, the majority of which is obtained by burning carbonaceous materials (gases, hydrocarbons, coal). This results in a high carbon footprint for the process.

[0006] Technical solutions are known that use sunlight as an energy source for gasification processes (thus very similar to the pyrolysis of plastic materials). Typically, in these processes, the sunlight is directly concentrated on an absorber placed inside the reactor or on its outer surface. Other processes (e.g., the pyrolysis of biomass) use a heat transfer fluid containing molten salts, which of course must reach at least the maximum temperature required for pyrolysis.

[0007] Therefore, using solar radiation as an energy source could be a known solution. However, the solutions disclosed to date have significant limitations, including in particular the fact that heating the fluid (or directly heating the pyrolysis reactor) to the temperatures required in the pyrolysis process requires very high temperatures, i.e., very high concentration rates associated with very low efficiency. The latter is related, among other factors, to a dramatic increase in the emissivity of the absorber tube, from which most of the radiant energy is re-emitted towards the environment. This means that for a given pyrolysis oil production volume, very large mirror surfaces must be used.

[0008] It is therefore desirable to have a pyrolysis process that allows the use of solar energy while limiting the extent of the radiative surface required for a given production. The solution of the present invention makes it possible to achieve this goal.

[0009] Several patent applications disclose processes for the pyrolysis or catalytic pyrolysis of plastic materials, some of which address the possibility of utilizing solar energy.

[0010] Department of Energy (DOE) patent US 4,415,339 teaches a method for producing a substantially hydrocarbon-free product gas (synthesis gas) from a carbonaceous material feedstock in a solar reactor, where solar energy is supplied directly, i.e., through a window that allows sunlight to penetrate and heat the material for gasification.

[0011] US 4,582,590 (National Aeronautics and Space Administration) discloses a method for pyrolysis of shale which involves the use of concentrated solar radiation, which passes through a "solar window" onto a ceramic honeycomb receiver and is heated to 350°C.

[0012] WO2010 / 103520 discloses a photovoltaic device for converting sludge by pyrolysis, which includes a pyrolysis reactor operable by solar energy. Such solar energy is concentrated by a concentrating mirror and redirected to a receiver located within the pyrolysis reactor. When a sensor detects that the solar radiation intensity falls below a threshold, the reactor is shut down.

[0013] WO2017 / 055652 (Ministry of Energy) describes a hybrid power plant based on the use of solar energy, which includes a molten salt solar receiver configured to heat molten salt with solar energy, a low-temperature storage tank and a high-temperature salt storage tank, a steam generator, a condenser, and a reactor-salt-biomass exchanger for exchanging heat between the salt flow and biomass.

[0014] CN109207179 discloses a system for producing synthesis gas by concentrated solar molten salt pyrolysis of carbonaceous materials, such as rice husks, cotton and corn straw residues, and municipal waste, and the temperature can be higher than 800°C, for example, 1000°C.

[0015] WO / 2020 / 150244 (Sabic) discloses the use of renewable energy in olefin synthesis. In the claimed plant, at least one furnace is electrically heated and at least 90% of the heating is performed without burning fuel.

[0016] None of the cited patents disclose a process for treating plastic materials to produce pyrolysis oil using a solar energy source. Furthermore, in most cases, solar energy is utilized directly, for example by directly concentrating solar radiation onto an absorbing surface located within the reactor.

[0017] Several patent applications disclose the use of molten salt as a heat transfer medium for producing synthesis gas from biomass (municipal waste, cotton and corn straw, rice husks, etc.). Biomass is chemically completely different from plastic materials, and the resulting product (synthesis gas) is also completely different from pyrolysis oil. Therefore, the required operating conditions, such as temperature, are significantly different (sometimes even above 1000°C). This process typically fails to solve the problems of the present invention. For example, as disclosed in the cited CN109207179, the molten salt used melts at approximately 400°C. Generally, it is unsafe to use molten salt near its melting point to avoid solidification of the salt mixture within the equipment. This means that this process cannot be used for the pyrolysis of plastics, which requires temperatures of 400-520°C.

[0018] Pyrolysis of plastic materials is a highly desirable process, enabling the recycling of mixed plastic waste materials by breaking down polymer chains into small organic molecules that, after appropriate purification processes, can be used to synthesize polymers. Most other recycling processes, such as so-called mechanical recycling (i.e., extruding waste plastics with virgin plastics to produce blends), require the use of very pure waste plastics (i.e., containing only specific polymers, such as expanded polystyrene, linear low-density polyethylene, or polyethylene terephthalate). In fact, different polymers are not miscible with each other, and as a result, blending such polymer mixtures with certain virgin polymers significantly reduces their performance.

[0019] Other recycling processes, such as solvent dissolution and precipitation, can specifically dissolve certain plastic materials, resulting in the precipitation of nearly pure polymers. However, they require vast amounts of solvent, require the removal of insoluble plastics, and purify the solvent from all dissolved and dispersed contaminants (short-chain molecules, inorganic additives used as fillers, etc.). Furthermore, polyolefins, for example, are quite difficult to dissolve, so this process is only applicable to certain plastics.

[0020] Pyrolysis of plastic materials has the important advantage of being able to effectively process mixed plastic waste, even when non-plastic waste materials such as paper are present; furthermore, unlike other technologies, it has the ability to recycle mixed plastic waste indefinitely. That is, there is an infinite loop of plastic production from monomers, plastic use, post-consumer waste recovery, and then pyrolysis of the waste to produce monomers; thus, the loop is closed. For this reason, such processes are often referred to as "closed-loop recycling."

[0021] However, this is a strongly endothermic process, requiring enormous amounts of heat energy. Furthermore, the required pyrolysis temperatures are quite high (>500 °C), necessitating high-quality (i.e., high-exergy) heat. As a result, energy sources available in this range are limited. Typically, this energy source is a gas heater (burning natural gas and / or non-condensable gases produced by the pyrolysis process itself) or direct electric heating via the Joule effect. Electric energy has a very high calorific value, making it inconvenient to utilize for Joule heating. Furthermore, because the combustion of hydrocarbons produces large amounts of carbon dioxide (CO2), and electric energy in most countries is produced by burning gas, oil, or carbon dioxide, both electric energy and gas heating contribute significantly to the carbon footprint. Furthermore, the high temperatures make the use of heat pumps to pump heat from lower-energy sources (such as steam or geothermal) virtually impossible.

[0022] As a result, there is a high risk that the infinite recycling capacity of pyrolysis ("closed-loop recycling") will be limited by the fact that it requires the use of large amounts of valuable and / or environmentally unfriendly energy sources.

[0023] As previously reported, several patents disclose the direct application of sunlight, concentrated by a concentrating mirror, to a receiver placed within a reaction chamber to produce syngas. However, sunlight is an intermittent source, and syngas production quickly ceases when sunlight declines. These processes require high temperatures and long periods of time to stabilize, making the use of direct sunlight a significant limitation to practical application.

[0024] Therefore, there is a long-felt need for a process for producing pyrolysis oil from essentially plastic materials that uses a heat source that has little impact on CO2 production and allows for efficient use of energy resources. Summary of the Invention

[0025] The applicant has surprisingly discovered a process for producing at least pyrolysis oil from essential plastic materials, the process comprising the following steps: a) heating a first heat transfer fluid F1 by solar radiation to a temperature T1 between 400°C and 520°C; b) heating the second heat transfer fluid F2 by solar radiation to a temperature T2 higher than the temperature T1; c) heating the first pyrolysis reactor R1 with the heated first heat transfer fluid F1, whereby the heated first heat transfer fluid F1 is cooled in this operation; d) heating the second pyrolysis reactor R2 with the heated second heat transfer fluid F2, whereby the heated second heat transfer fluid F2 is cooled in this operation; e) supplying at least essential plastic material M1 to a first pyrolysis reactor R1; f) maintaining said essential plastic material M1 in said first pyrolysis reactor for a residence time RT1 of at least 2 minutes, which is in any case sufficient to produce a gaseous fluid M2 containing hydrocarbons; g) supplying the hydrocarbon-containing gaseous fluid M2 produced in the first pyrolysis reactor R1 to a second pyrolysis reactor R2; h) maintaining said fluid M2 in gaseous state in said second pyrolysis reactor for a residence time RT2 of at least 10 seconds; i) totally or partially condensing the gases leaving said second pyrolysis reactor R2 so as to form at least a liquid comprising hydrocarbons having a normal boiling point not lower than 25°C; Includes.

[0026] The process disclosed and claimed in this invention has the following advantages over processes known in the prior art: Closed-loop recyclability: The disclosed process can produce liquid hydrocarbons that, after further processing (e.g., by cracking and / or refining processes), can be used to make polymers. After use, articles made from such polymers can be fed back into the disclosed process. This process can be repeated indefinitely. As a result, plastic materials can be recycled virtually infinitely. ·GHG emission free: The heat required for the pyrolysis process is obtained without direct and / or indirect generation of harmful greenhouse gases (such as anhydrous carbon, CO2). Efficient use of molten salt heat transfer fluid: The heat transfer fluid, preferably molten salt, is the same for both the solar thermal system and the pyrolysis system, allowing the same fluid to flow through both systems. Therefore, no expensive heat exchangers are required. Maximum utilization of solar energy: Solar energy is a precious resource, especially when high-temperature heat is required. Indeed, in this case, a high concentration factor is required, so that a large area of ​​incident solar radiation must be reflected onto a relatively small heating area. The special synergistic process configuration disclosed in this application is able to address this very specific problem, since, as will be shown below, the solution provided actually makes it possible to reduce the required average concentration factor. Mixed Plastic Waste and Plasmix Support: Preferably, the process feeds on mixed plastic waste materials, requiring little or no pre-processing and eliminating the need for a single-material source, such as essentially pure polyethylene. Even more preferably, the process feeds on residual plastics from a sorting process that has already separated and extracted single materials, particularly polymers that can be reused if they are only lightly contaminated, such as polyethylene terephthalate (PET) and low-density polyethylene (LDPE). Such feedstocks are sometimes referred to as "Plasmix" (derived from a plastic mix). The plastic material fed to the process may contain small amounts of non-plastic materials, such as wood, paper, concrete, metal, and biomass. Plastics containing inorganic fillers and halogens, such as polyvinyl chloride, can also be fed and processed. Fouling-free: No fouling, carbon deposits or clogging occurs even when essential plastic materials such as high carbon-hydrogen ratio plastics such as polystyrene or oxygen-rich polymers such as polyethylene terephthalate are fed.

[0027] The present invention also discloses and claims a plant for producing at least pyrolysis oil from essential plastic materials, the plant comprising: A) a first pyrolysis reactor (70) having at least one inlet through which essential plastic material is fed, an outlet through which at least one gaseous effluent is removed, and a jacket and / or coil with at least one inlet and one outlet for a heat transfer fluid; B) a second pyrolysis reactor (71) having at least one inlet through which at least one gas stream from the first pyrolysis reactor (70) is fed, an outlet through which at least one gaseous effluent is removed, and a jacket and / or coil with at least one inlet and one outlet for a heat transfer fluid; C) A first solar collector assembly (61) including a first solar receiver, preferably consisting of a tube receiver, the first solar receiver including at least one inlet and one outlet for a heat transfer fluid, the solar collector assembly being capable of supplying concentrated solar radiation to the first solar receiver configured to heat the heat transfer fluid. D) a second solar collector assembly (62) consisting of a second solar receiver, preferably a tube receiver, said second solar receiver including at least one inlet and one outlet for a heat transfer fluid, said solar collector assembly being capable of supplying concentrated solar radiation to said second solar receiver configured to heat said heat transfer fluid; E) a first tank (63, "cold reservoir") in which cold heat transfer fluid is collected, the first tank (63) being fluidly connected to receive the heat transfer fluid from the first pyrolysis reactor (70) and to deliver the heat transfer fluid to the first solar collector assembly (61); F) a second tank (64, "warm reservoir") in which a medium temperature heat transfer fluid is collected, the second tank (64) being fluidly connected to receive the heat transfer fluid from the first solar collector assembly (61) and to deliver the heat transfer fluid to the first pyrolysis reactor (70); G) a third tank (65, "hot reservoir") in which hot heat transfer fluid is collected, the third tank (65) being fluidly connected to receive the heat transfer fluid from the second solar collector assembly (62) and deliver it to the second pyrolysis reactor (71); H) a condenser (72) having at least one inlet for a gaseous stream containing hydrocarbons and one outlet for a condensate capable of at least partially condensing the gaseous stream containing hydrocarbons; Including, The first solar collector (61) is fluidly connected to the first tank (63) at one end of the first solar receiver and to the second tank (64) at the other end of the first solar receiver; the second solar collector (62) is fluidly connected to the second tank (64) at one end of the second solar receiver and to the third tank (65) at the other end of the second solar receiver; the condenser (72) is fluidly connected to the second pyrolysis reactor (71) so as to partially condense pyrolysis vapors produced by the first and second pyrolysis reactors.

[0028] definition In describing the present invention, ranges of values ​​(eg, ranges of pressure, temperature, amount, etc.) are considered to include the extreme values ​​unless otherwise specified.

[0029] In the description of the present invention, percentages are by weight (i.e., by mass) unless otherwise specified. The symbol "%" means percentage unless specified by weight (mass).

[0030] In describing the present invention, the term "comprising" also includes, in particular in the limiting sense, the meanings "consisting of" and "essentially consisting of."

[0031] In describing this invention, the term "essentially consisting of" means that a composition or formulation (1) necessarily contains the recited ingredients and (2) may contain unrecited ingredients that do not materially affect the basic and innovative properties of the composition.

[0032] In the context of this invention, unless otherwise specified, the act of maintaining a parameter (e.g., pressure) within a predetermined range means that active action is taken to keep this parameter within the range, for example by ensuring that a measurement falls within the predetermined range and / or by adjusting the parameter via a feedback regulation system that sets the value of this parameter within the predetermined range.

[0033] In the description of the present invention, "essentially plastic material" means a composition of one or more plastics, optionally containing up to 30 wt. % of non-plastic materials, based on the weight of the essential plastic material.

[0034] In the description of the present invention, the term "plastic material" refers to a general polymeric material that may contain other substances to improve performance and / or reduce cost, and follows the IUPAC definition (Pure Appl. Chem. Vol. 84, No. 2, pp. 377-410, 2012).

[0035] In the description of the present invention, "hydrocarbons having a normal boiling point of not less than 25°C" means that such hydrocarbons individually have a normal boiling point as defined by IUPAC of at least 25°C (i.e., equal to or greater than 25°C).

[0036] In the description of the present invention, the act of totally or partially condensing the gases leaving said second pyrolysis reactor R2 to form at least a liquid comprising hydrocarbons having a normal boiling point not below 25°C does not exclude that such liquid may also comprise hydrocarbons and non-hydrocarbon compounds having a boiling point below 25°C.

[0037] In the context of the present invention, the term "pyrolysis vapor" refers to the gas phase produced during the pyrolysis of the essential plastic material, such as the gaseous effluent of the first pyrolysis reactor. This latter term includes not only the products of pyrolysis, but also compounds that are in a gaseous state under the pressure and temperature conditions of pyrolysis and that were already present in the essential plastic material being pyrolyzed, or that were added or already present in the first pyrolysis reactor (e.g., in an inert gas), such as nitrogen, water, low-boiling plasticizers, etc. The hydrocarbon content in the pyrolysis vapor is typically 50 wt% or more.

[0038] In the context of the present invention, pyrolysis oil means a hydrocarbon-containing liquid formed by partial or total condensation of pyrolysis vapors and having a normal boiling point not lower than 25° C. The hydrocarbon content in pyrolysis oil is typically at least 50 wt %.

[0039] In the context of this invention, pyrolysis residue (or, synonymously, char) refers to products that are in the liquid, solid, or liquid and solid state (i.e., semi-solid) in the first pyrolysis reactor, or products that are in the liquid and / or solid state under the conditions of temperature, pressure, and composition in pyrolysis.

[0040] In the description of the present invention, unless otherwise specified, the substantial absence of oxygen means that the oxygen (understood as molecular oxygen) in the pyrolysis vapor is less than 2% by weight, preferably less than 0.8% by weight, and more preferably 20 to 4000 ppm by weight, relative to the total weight of the composition of said vapor.

[0041] In describing this invention, "heat transfer fluid" means a solid, liquid, gas, or multiphase fluid used to transfer heat from one system to another, especially from a heat source to another heat duty. Preferably, a heat transfer fluid is a fluid specifically manufactured for the purpose of transferring heat and is stable (i.e., does not degrade rapidly) under the process conditions used.

[0042] In the context of the present invention, the first heat transfer fluid need not be compositionally different from the second heat transfer fluid, although preferably they have different temperatures.

[0043] In the present description, "SCA" refers to a solar collector assembly, which generally includes a reflector (a mirror, such as a Fresnel reflector, or a parabolic mirror in the case of a parabolic trough), a metal support structure, one or more receiver tubes, and, optionally, a tracking system including drives, sensors, and controls. The length of the receiver tube need not be the same as the length of the reflector; multiple receiver tubes can be connected in series to form longer receiver tubes (possibly longer than 200 m), thereby serially receiving solar radiation from multiple mirrors / reflectors. Furthermore, to optimize the mass flow rate of the heat transfer fluid in the receiver tube and maximize solar radiation, it is useful to split the flow of heated heat transfer fluid into multiple absorber tubes in parallel. Therefore, in the present description, a solar collector assembly generally includes multiple mirrors / reflectors and associated absorber tubes, preferably combined in series, parallel, and series-parallel combinations.

[0044] In the context of this invention, the term "molten salt" (or equivalent thereof) refers to a salt that is solid at standard temperature and pressure but becomes liquid at elevated temperatures. Molten salts can be composed of a single component (e.g., sodium nitrate alone) or a mixture of salts (e.g., a mixture of sodium nitrate and potassium nitrate).

[0045] In the context of this invention, the term "load device" refers to any device that is heated by a heat transfer fluid. Examples of "load devices" include the first and second pyrolysis reactors, cokers, and preheaters.

[0046] In describing this invention, the terms "fluid loop," "heat transfer fluid loop," "high temperature loop," and "warm loop" refer to a process in which the heat transfer fluid is substantially completely recirculated within the process.

[0047] By "substantially fully recirculated" it is meant that heat transfer fluid is neither produced nor consumed in the process, so there is no net inlet or outlet flow. However, spillage or slow displacement of fluid may occur for convenience, particularly since most heat transfer fluids are known to degrade over time at high temperatures. Preferably, a substantially fully recirculated fluid has a total inlet or outlet mass flow rate of less than 1%, more preferably less than 0.1%, of the recirculation mass flow rate.

[0048] In the description of the present invention, unless otherwise specified, a parameter value that is at most equal to a predetermined value X means that the parameter value is equal to or less than X, and a parameter value that is at least equal to a predetermined value X means that the parameter is equal to or greater than X.

[0049] In the description of the present invention, unless otherwise specified, the yield in the production of a product means the weight percentage of that product relative to the total amount of products obtained.

[0050] Unless otherwise specified, "part by weight" and "parts by weight" in this specification mean parts by weight and parts by weight, respectively. Weight means mass, i.e., kg in SI units.

[0051] Unless otherwise specified herein, the combination of an individual range from one list with another individual range appearing from a second range list and relating to different characteristics should be considered to be disclosed in this application, even in the absence of an explicit indication of such a combination. [Brief explanation of the drawings]

[0052] [Figure 1]FIG. 1 shows a process scheme illustrating one embodiment of the present invention, featuring three heat transfer fluid reservoirs and two pyrolysis reactors. [Figure 2] FIG. 2 shows a process scheme illustrating an embodiment of the present invention featuring the addition of a plastic preheater (such as an extruder or screw device). [Figure 3] FIG. 3 shows a process scheme illustrating an embodiment of the present invention featuring the addition of an additional device ("coker") to further treat the liquid / solid / semi-solid residue (char) effluent of the reactor. [Figure 4] FIG. 4 shows a process scheme illustrating an embodiment of the present invention featuring both the presence of the coker and a plastic preheater (such as an extruder or screw unit) to further process the liquid / solid / semi-solid residue (char) effluent of the reactor. [Figure 5] FIG. 5 shows a process scheme illustrating an embodiment of the invention characterized by the fact that the condensation of the pyrolysis gases is carried out in more than one unit, in the first of such units said pyrolysis gases being cooled by a heat transfer fluid before entering a low temperature reservoir, thereby realizing heat recovery. [Figure 6] FIG. 6 shows a process scheme illustrating an embodiment of the present invention, characterized in that heat transfer fluid from a warm reservoir is routed by a weir device 78 to a first pyrolysis reactor and a preheater device in semi-series before returning to the cold reservoir. [Figure 7] FIG. 7 shows a process scheme illustrating an embodiment of the present invention, characterized in that heat transfer fluid from a hot reservoir is routed by a weir device 79 to a coker device and a second pyrolysis reactor in semi-series before returning to the cold reservoir. [Figure 8] FIG. 8 shows a process scheme with double heat transfer fluid loops corresponding to Example 1 (invention). [Figure 9] FIG. 9 shows a process scheme with a single heat transfer fluid loop, corresponding to Example 2 (comparative example). [Figure 10]FIG. 10 shows a process scheme illustrating an embodiment of the present invention characterized in that the first heat transfer fluid and the corresponding heat transfer fluid loop are not in fluid communication with the second heat transfer fluid and the corresponding heat transfer loop. [Figure 11] FIG. 11 shows a process scheme illustrating some embodiments of the present invention, characterized by the location of the additional power supply in three different positions (66A for a parallel configuration, 66B and 66C for a series configuration). [Figure 12] FIG. 12 is a process scheme illustrating an embodiment of the present invention featuring the use of three reservoirs, with emphasis on illustrating the hot and warm loops and their distinction. [Figure 13] FIG. 13 is a process scheme illustrating an embodiment of the present invention featuring the use of four reservoirs and two completely independent loops, with an emphasis on illustrating the hot and warm loops and their distinction. [Figure 14] FIG. 14 is a process scheme illustrating an embodiment of the present invention featuring three reservoirs and two fully or partially independent loops. DETAILED DESCRIPTION OF THE INVENTION

[0053] According to one embodiment, the process for producing at least pyrolysis oil from essential plastic material is characterized in that fluids F1 and F2 are substantially completely recycled.

[0054] A first embodiment of the present invention is shown in Figure 1. This scheme includes: a first pyrolysis reactor (70) (low temperature), also called the primary pyrolysis reactor; A second pyrolysis reactor (71) (high temperature), also called the secondary pyrolysis reactor; a condenser (72) for condensing the effluent of the second pyrolysis reactor (71); · A separator (73) for separating the gas (non-condensable) and liquid phases; · Medium temperature solar collector assembly or first solar collector (61) (SCA); · High temperature solar collector assembly or secondary solar collector (62) (SCA); ·Cold reservoir of heat transfer fluid (63); · Heat transfer fluid hot water reservoir (64); · High temperature reservoir of heat transfer fluid (65); A heat transfer fluid pump 66 that delivers heat transfer fluid to the heating system (solar receiver) and duty (pyrolysis reactor); Optional bypass (B1)~(B4=)

[0055] In connection with a plant for producing at least pyrolysis oil from essential plastic materials, the following operations are preferably carried out: heating a first heat transfer fluid F1 by solar radiation to a temperature T1 between 400°C and 520°C in said first solar collector assembly (61) including a first solar receiver (process step a); heating a second heat transfer fluid F2 by solar radiation to a temperature T2 higher than the temperature T1 in said second solar collector assembly (62) comprising a second solar receiver (process step b); a jacket and / or coil, comprising at least one inlet and one outlet for the molten salt, included in said first pyrolysis reactor (70) (element "A"), for heating said first pyrolysis reactor (70) (or R1) by means of a heated first heat transfer fluid F1; a jacket and / or coil, comprising at least one inlet and one outlet for the molten salt, is included in said second pyrolysis reactor (71) (element "B") and provides heating of said second pyrolysis reactor (71) (or R2) by means of a heated second heat transfer fluid F2; - said first pyrolysis reactor (70) (element "A") is supplied with at least essential plastic material M1 (process step e), said essential plastic material M1 being held in said first pyrolysis reactor for a residence time of at least 2 minutes, in any event sufficient to produce a gaseous fluid M2 containing hydrocarbons (process step f); the second pyrolysis reactor (71) (element "B") is supplied with the gaseous fluid M2 comprising the hydrocarbons produced in the first pyrolysis reactor (70) (or R1) (process step g), and the gaseous fluid M2 is maintained in the second pyrolysis reactor (71) (or R2) for a residence time of at least 10 seconds (process step h); In the condenser (72) (element "H"), the gases leaving the second pyrolysis reactor (71) (or R2) are condensed to form a liquid comprising at least hydrocarbons with a normal boiling point not below 25°C (process step i). In the context of the present invention, a fluid connection may include an intervening or interposed device, such as a pump or a valve.

[0056] In the context of the present invention, electrical connection includes any non-mechanical and non-thermal means of transmitting information, such as by the flow of electrons (electric current), the flow of photons (optical transmission, such as via optical fiber), or electromagnetic waves (e.g., WiFi transmission).

[0057] Essential plastic material is fed at (51) to a first pyrolysis reactor (70). This first pyrolysis reactor (70) is heated by a medium temperature heat transfer fluid (33) from a warm reservoir (64). The heat transfer fluid (and therefore cold) exiting the first pyrolysis reactor (70) is transferred to a cold reservoir (63).

[0058] The pyrolysis gas generated in the reactor (70) is sent to a second pyrolysis reactor (71) which has a higher temperature than the first pyrolysis reactor (70), and the solid or semi-solid residue (such as char) is recovered in (53).

[0059] In some embodiments, a portion of the liquid contained in reactor (70) can also be recovered from (53).

[0060] In the second pyrolysis reactor (71), the pyrolysis gas from the first reactor (70) is heated to a higher temperature by the heat transfer fluid (37) from the hot reservoir (65). Thus, in the second reactor (71), the gas is further pyrolyzed. The effluent of the second reactor (71) is cooled and condensed by the condenser (72). The uncondensed gas is recovered in (55). The condensate forms pyrolysis oil, which is collected in the reservoir (73) and recovered in (56). The reservoir (73) can be integrated with the condenser (72). The heat transfer fluid leaving the second pyrolysis reactor is transferred to the hot reservoir (64).

[0061] The optional bypasses (B1)-(B4) are useful for refilling the reservoirs from each other without having to go through the heating system and duty (for maintenance and / or to decouple flow and heat duty).

[0062] The medium temperature solar collector assembly (SCA) (61) heats the heat transfer fluid (31) from the low temperature tank (63), and the high temperature solar collector assembly (62) heats the heat transfer fluid (35) from the warm tank (64). The heat transfer fluid from the medium temperature solar collector assembly (61) is transferred to the warm reservoir (64), and the heat transfer fluid from the high temperature solar collector assembly (62) is transferred to the warm reservoir (65).

[0063] According to one preferred embodiment, the heat transfer fluid in one loop is heated by at least one solar collector assembly, cooled in at least one pyrolysis reactor while releasing heat, and then returned to the solar collector assembly (possibly passing through a heat transfer fluid reservoir).

[0064] According to a preferred embodiment, in the process for producing at least pyrolysis oil from essential plastic material, fluids F1 and F2 are substantially completely recycled.

[0065] Preferably, the process of the present invention is a double loop process (alternatively, a "two-loop process").

[0066] This means that there are two substantially independent thermal loops: in the so-called "warm loop" (or more simply "warm loop"), a heat transfer fluid F1 is heated from a low temperature to a "warm" temperature by a first (lower temperature) solar collector assembly. This fluid is used in the first pyrolysis reactor and optionally other devices as taught in this disclosure.

[0067] In the so-called "high temperature thermal loop" ("high temperature loop"), a heat transfer fluid F2 is heated from a "warm" temperature to a "hot" temperature by a second solar collector assembly. This fluid is used in a second pyrolysis reactor and optionally other devices as taught in this disclosure.

[0068] According to a preferred embodiment, the recirculation of fluid F1 forms a first heat transfer fluid loop (the "warm loop"), and the recirculation of fluid F2 forms a second heat transfer fluid loop (the "hot loop").

[0069] In a double loop process, the molten salt fluids of the double loops may be mixed at some point (typically a warm reservoir). However, the essential feature that distinguishes a double loop process from a single loop process is that heat transfer fluids are at least partially drawn from at least two points (F1, F2) of the solar collector assembly at different temperatures (T1, T2) and are at least partially used separately to heat pyrolysis devices (such as reactors) at different temperatures.

[0070] By "at least partially separately used" is meant that there are at least two separate circuits ("hot loop", "warm loop") through which a heat transfer fluid flows and to which a load device (such as a pyrolysis reactor) is fluidly connected.

[0071] According to one embodiment, the first heat transfer fluid F1 and the second heat transfer fluid F2 have the same composition but different temperatures. According to one embodiment, fluid F1 and fluid F2 can mix at a certain point in time, preferably when they are at substantially the same temperature.

[0072] According to one embodiment, the first heat transfer fluid F1 and the second heat transfer fluid F2 have the same composition but different operating temperatures (T1 and T2) and are mixed at a single point, preferably in a reservoir (such as a "warm reservoir").

[0073] A simplified diagram of this embodiment is shown in Figure 12, which is provided to clearly illustrate the flow of heat transfer fluid within each loop. In Figure 12, the two loops are intermingled at the "warm" reservoir (64), but remain substantially separate because they only have one point of contact. In Figure 12, the coker (76) and preheater (74) are enclosed in dotted boxes to indicate that they are optional. The dashed lines within the reservoirs indicate the direction of flow within the reservoirs.

[0074] The cold, hot and warm reservoirs may optionally include some mixing capability such as an internal recirculation pump or an agitator, e.g., an anchor agitator, a turbine agitator, or a pitched blade impeller, etc. Such mixing means improves temperature uniformity within the reservoirs and is particularly useful, especially during start-up.

[0075] However, even without the mixing function, the flow of heat transfer fluid from inlet to outlet and natural convection contribute to some degree of internal circulation and mixing within the reservoirs. Therefore, the dashed lines, particularly in the warm reservoirs, are symbolic representations of the flow direction of the heat transfer fluid within the reservoirs and should not be intended as the only possible flow within the reservoirs.

[0076] Therefore, with reference to the steps of the process of the invention already disclosed, the subject of the invention is a process for producing at least pyrolysis oil from essential plastic materials, wherein a first loop comprises said steps a) and c) and a second loop comprises said steps b) and d).

[0077] According to another embodiment, the process for producing at least pyrolysis oil from essential plastic material further comprises the following steps: j) storing the first heat transfer fluid F1 obtained in step c) in a reservoir ("cold reservoir") before use in step a); k) storing the second heat transfer fluid F2 heated in step b) in a reservoir (the "hot reservoir") prior to use in step d).

[0078] According to another embodiment, in the process for producing at least pyrolysis oil from essential plastic material, the heat transfer fluid F1 is compositionally identical to the heat transfer fluid F2.

[0079] In the case where the fluids F1 and F2 are identical in composition, according to another embodiment, the process of the invention for producing at least a pyrolysis oil from essential plastic material further comprises the following steps: l) storing in a reservoir ("warm reservoir") the first heat transfer fluid F1 heated in step a) before use in step c) and the second heat transfer fluid F2 cooled in step d) before use in step b).

[0080] Another embodiment of the invention having a "separate loop" is shown in Figure 10. This scheme involves the same device as Figure 1, except that the warm reservoir 64 is split into two separate reservoirs 64A and 64B: A first "warm" reservoir ("warm reservoir A", 64A) collects heat transfer fluid from the first solar collector assembly (61). The first "warm" reservoir (64A) delivers heat transfer fluid to the first pyrolysis reactor (70) and optionally to a pyrolysis device requiring lower temperatures, such as a preheater or heat exchanger using an organic heat transfer fluid. A second "warm" reservoir ("warm reservoir B", 64B) collects heat transfer fluid from a device requiring higher temperatures, such as a second pyrolysis reactor or coker. · A second "warm" reservoir (64B) delivers heat transfer fluid to the second solar collector assembly (62).

[0081] A simplified diagram of the same embodiment is shown in Figure 13, which is provided to clearly show the flow of heat transfer fluid within each loop.

[0082] Thus, one embodiment of the present invention is a process for producing at least pyrolysis oil from essential plastic material, the process further comprising the steps of: m) storing the first heat transfer fluid F1 heated in step a) in a reservoir ("warm reservoir A") prior to use in step c); n) storing the second heat transfer fluid F2 cooled in step d) in a reservoir ("warm reservoir B") prior to use in step b).

[0083] The above-described embodiment having separate loops allows for complete separation of the heat transfer fluid loops, thus allowing for the use of different fluids in the hot and warm loops. For example, a molten salt with a lower melting temperature could be used in such a loop. Using a molten salt with a lower melting point is generally advantageous because it means that the plant can be safely operated at lower temperatures (it is generally desirable to operate the plant so that, at its coldest point, the temperature of the molten salt is at least 50°C above its melting point) and also reduces the time required for restarting after an extended shutdown.

[0084] However, molten salts with low melting points typically also have low thermal stability and therefore cannot be used in high temperature loops requiring very high temperatures.

[0085] Therefore, according to this embodiment, it is advantageous to use a heat transfer fluid for the warm loop that is different from the heat transfer fluid for the high temperature loop. According to this embodiment, preferably the heat transfer fluid for the warm loop has a lower melting point than the heat transfer fluid for the hot loop, more preferably the heat transfer fluid for the warm loop has a melting point of at most 180°C, even more preferably at most 150°C.

[0086] For example, the so-called Hi-Tech fused salt (7 wt% sodium nitrate, 53 wt% potassium nitrate, 40 wt% sodium nitrite) or a ternary mixture of lithium nitrate, sodium nitrate and potassium nitrate, for example a eutectoid mixture with the composition 25.9 wt% lithium nitrate + 20.6 wt% sodium nitrate + 54.1 wt% potassium nitrate, can be used as the heat transfer fluid.

[0087] For example, a quaternary mixture of sodium nitrate, potassium nitrate, lithium nitrate and calcium nitrate, e.g., a mixture containing 9.5 mol% sodium nitrate, 52.8 mol% potassium nitrate, 27.6 mol% lithium nitrate, 10.1 mol% calcium nitrate, has a melting point of only 98.3°C.

[0088] Another embodiment of the present invention having an "isolation loop" is shown in Figure 14. According to this embodiment, similar to the embodiment of Figure 13, the warm reservoir (64) is divided into two reservoirs (64A) and (64B), but the two reservoirs (64A) and (64B) are in the same container (such as a tank) and are separated by a weir (64C). This allows for fewer units to be constructed, thereby reducing installation costs. Furthermore, the weir (64C) allows one heat transfer fluid to overflow into the other reservoir if the liquid level becomes too high.

[0089] Optionally, weir (64C) includes at least one opening (64D), preferably at the bottom of the weir, to allow the fluid levels in the two reservoirs (64A) and (64B) to balance. When such at least one opening is present, the separation of the fluids in the two reservoirs (64A) and (64B) is not complete. Therefore, when the opening is large, the contact surface between the fluids in the two reservoirs is large, and the scheme of FIG. 14 corresponds to the scheme of FIG. 12. Conversely, when the opening is small, the contact surface is minimal or even zero, and the scheme of FIG. 14 corresponds to the scheme of FIG. 13.

[0090] Therefore, an embodiment of the present invention is a process for producing at least pyrolysis oil from essential plastic materials, further comprising steps m) and n), characterized in that said warm reservoir A and warm reservoir B are contained in the same container, preferably separated by a weir. According to another embodiment, in said steps, said weir comprises at least one opening that allows fluid in said warm reservoir A to flow into said warm reservoir B and vice versa.

[0091] Preferably, the essential plastic material comprises a composition of different plastics, more preferably the composition of different plastics comprises at least a polymer with a high H / C ratio, such as polyethylene, polypropylene, polyamide, polymethyl methacrylate, and a polymer with a low H / C ratio, such as polystyrene, polycarbonate, polyethylene terephthalate.

[0092] Alternatively, or in combination, the different plastic compositions include high carbon index polymers such as polyethylene (including LDPE, LLDPE, HDPE), polypropylene, polystyrene, elastomers, and low carbon index polymers such as polyamide, polymethyl methacrylate, polyethylene terephthalate, polyvinyl chloride, cellulose, etc.

[0093] Preferably, said essential plastic material is characterized by an H / C ratio (H / C index) of at least 70, preferably 80-98, more preferably 85-96.

[0094] Preferably, said essential plastic material is characterized by a carbon index of at least 55, preferably between 65 and 95, more preferably between 75 and 90.

[0095] The H / C index is proportional to the ratio of the total mass of hydrogen atoms to the total mass of carbon atoms present in the essential plastic material and is calculated by the following formula: Equation 1

[0096] TIFF2026505342000002.tif21163

[0097] The carbon index is proportional to the ratio of the total mass of carbon atoms to the total mass of all atoms present in the essential plastic material and is calculated by the following formula: Equation 2

[0098] TIFF2026505342000003.tif19157In the formula, "weight of all atoms" corresponds to the weight of the essential plastic material.

[0099] Preferably, the essentially plastic material contains at least one non-plastic material in an amount ranging from 0.01% to 10%, more preferably from 0.05% to 7.5%, and even more preferably from 0.2% to 5% by weight of the essentially plastic material, preferably including at least one of paper, cardboard, wood, compost (as defined by IUPAC in "Terminology for Bio-Related Polymers and Applications (IUPAC Recommendations 2012)," Pure Appl. Chem., Vol. 84, No. 2, pp. 377-410, 2012, DOI 10.1351 / PAC-REC-10-12-04), metal materials such as aluminum and iron, and / or inert materials.

[0100] Optionally, the essentially plastic material comprises an inorganic filler, such as silica, titanium oxide, talc, coke, graphite, carbon black, calcium carbonate, and the like.

[0101] Optionally, the essential plastic material contains brominated and chlorinated additives used to make the plastic material fire resistant or otherwise render it flame retardant, examples of which include hexabromocyclododecane, decabromodiphenyl oxide, polybrominated diphenyl ethers, and bromine-containing polymers such as brominated styrene-butadiene copolymers or brominated polystyrene.

[0102] Optionally, the essential plastic material comprises non-halogenated additives, such as compounds of phosphorus and nitrogen, used to make or in any way impart flame retardancy to the plastic material.

[0103] Preferably, the essential plastic material is a recycled material, such as a waste material or a secondary raw material.

[0104] Preferably, the essential plastic material also contains halogen (typically from polyvinyl chloride) in an amount ranging from 0.01% to 10% by weight, based on the weight of the essential plastic material.

[0105] Preferably, the essential plastic material is obtained from a sorting process of plastic material. More preferably, the essential plastic material is an essential plastic material residue, i.e., an essential plastic material fraction remaining after recovering some plastics or after selectively extracting some plastics from the essential plastic material fed to the sorting process. Selective extraction is essentially homogeneous extraction of a given plastic (i.e., extraction as a monoplastic). Typically, the sorting process makes it possible to extract a substantially pure plastic stream (i.e., monoplastic) of polyethylene, polypropylene, and polyethylene terephthalate components. Therefore, in this preferred sorting, the residual material of the essential plastic material is the material obtained after extraction of the substantially pure plastics. This fraction is known in Italy by the term "Plas Mix" or "Plasmix" and is defined as "the collection of heterogeneous plastics contained in post-consumer packaging and not recovered as individual polymers" (Senate No. 4502 of 05 / 18 / 2017).

[0106] According to another embodiment of the invention shown in Figure 2, the essential plastic material is preheated in a preheating device (74) before being fed to the first pyrolysis reactor (70). Advantageously, according to this embodiment, a heat transfer fluid (33) is fed from a warm reservoir to the heating jacket of the first pyrolysis reactor (70). The heat transfer fluid leaving the jacket of the pyrolysis reactor is sent to the jacket of said preheating device (74). The heat transfer fluid leaving the preheating device (34) is returned to the cold reservoir.

[0107] According to another embodiment of the invention shown in Figure 3, the solid, semi-solid or liquid material from the first pyrolysis reactor (70) is sent to a "coker" processing device (76). A separator (77) (which can be integrated into the coker device) recycles the gas phase (53E) to the process (e.g., the first pyrolysis reactor, as shown in Figure 3) and recovers the non-gas phase in flow (53D).

[0108] The char feed device (75) can be a pumping device that moves solid, semi-solid, or liquid material from the first pyrolysis reactor to the coker device while simultaneously providing physical separation between the two devices. An example of such a device is a gear pump. Alternatively, the char feed device (75) can be a valve, such as a rotary valve, gate valve, or butterfly valve.

[0109] Advantageously, according to this embodiment, the heat transfer fluid from the hot reservoir (37) is first sent to said coker device (76) and then to the second pyrolysis reactor (71) at (53B) before returning to the warm reservoir (38). Advantageously, said char supply device (75) can be heated by the heat transfer fluid (34A) coming from the heating jacket of the first pyrolysis reactor (70) before returning to the cold reservoir.

[0110] According to another embodiment of the invention shown in Figure 4, both embodiments shown in Figures 2 and 3 are combined, so that the essential plastic material is preheated in said preheater (74) and the solid, semi-solid or liquid material from the first pyrolysis reactor (70) is sent to the "coker" (76) by means of a char supply device (75). Advantageously, the heating of such a device is performed by means of a heat transfer fluid from a hot reservoir and a warm reservoir, as previously described in the description of the embodiment of Figures 2 and 3.

[0111] In the coker (76), the material is heated for at least 5 minutes, preferably 15-180 minutes, more preferably 30-120 minutes, to a temperature of 500°C-1200°C, preferably 600°C-1000°C, more preferably 700°C-900°C. As a result of such heat treatment, the char is purified, particularly the more volatile components are separated and collected in the gas phase, and the char is further pyrolyzed to produce a solid product with a lower H / C ratio, a higher carbon index, and a better health, safety, and environmental (HSE) profile.

[0112] The coker may be any device capable of such operation. Preferably, the coker is a device comprising a rotating screw. More preferably, the rotating screw is horizontal or has an inclination of up to 30° relative to the horizontal axis.

[0113] The coker can be heated by a heat transfer fluid, optionally a gas heater, by electrical resistance (Joule effect), or a combination thereof. When a heat transfer fluid is used, it is preferred to use a heat transfer fluid from a hot reservoir.

[0114] Therefore, according to one embodiment of the present invention, the process for producing at least pyrolysis oil from essential plastic material further comprises the following steps: o) Heating the liquid, solid or semi-solid residue (char) of the pyrolysis of step f) by a heated second heat transfer fluid F2, optionally also by a gas heater, by electrical resistance (Joule effect) or a combination thereof.

[0115] Preferably, in step o), the char is heated at a temperature of 500°C to 1200°C, preferably 600°C to 1000°C, more preferably 700°C to 900°C for at least 5 minutes, preferably 15 minutes to 180 minutes, more preferably 30 minutes to 120 minutes.

[0116] According to another embodiment of the invention shown in Figure 5, the condensation of pyrolysis gases leaving the second pyrolysis reactor is split into more than one unit (e.g., unit (72A) and unit (72B)). More specifically, pyrolysis gases (54) leaving the second pyrolysis reactor (71) are passed "hot" through a first condenser (72A) and a first separator (73A) which separates condensed liquid (56A) from non-condensable vapors (55A). The non-condensable vapors (55A) then pass "cold" through a second condenser (72B) and a second separator (73B) which separates condensed liquid (56B) from non-condensable vapors (55A).

[0117] Advantageously, according to this embodiment, the cooling of the first condenser (72A) is achieved by the heat transfer fluid (33E) already used to heat the first pyrolysis reactor (70) before entering the low temperature reservoir (63). In this way, heat recovery is achieved, reducing the overall heat duty for condensing the pyrolysis oil and, at the same time, reducing the required heat duty of the solar collector assembly (61) by heating the heat fluid.

[0118] According to one embodiment, heating of the first pyrolysis reactor (70), the char supply device (75) and the preheater (74) in the same temperature range can be achieved using heat transfer fluid (33) from a warm reservoir (64).

[0119] Other ancillary and miscellaneous devices, and components connecting such devices (eg, connecting pipes), can also be heated with the same heat transfer fluid.

[0120] Preferably, distribution of heat transfer fluid to such devices can be in series, parallel, or semi-series.

[0121] In the case of a series arrangement, preferably, the heat transfer fluid from the warm reservoir (64) is first fed to the pyrolysis reactor, and then to another device, such as a preheater (74) or a char supply device (75). More preferably, the order is the first pyrolysis reactor (70), then the preheater (74) (if present), and then the char supply device (75) (if present). According to a further embodiment, if the condensation is divided into two or more steps, and the cooling fluid in the first condenser is the heat transfer fluid, as shown in FIG. 5, such a series also includes the first condenser, and preferably, the first condenser is the last element in the sequence. Consequently, more preferably, the sequence is the first pyrolysis reactor (70), then the preheater (74) (if present), then the char supply device (75) (if present), and finally the first condenser (72A) (if present).

[0122] The semi-series configuration combines the series and parallel configurations, providing the advantages of both the series and parallel modes.

[0123] 6 and 7 show one embodiment of a semi-series configuration.

[0124] FIG. 6 illustrates a weir device (78) that receives heat transfer fluid from a warm reservoir (64), routes it to a first pyrolysis reactor (70) and a preheater (74), and finally discharges it to a cold reservoir (63). According to this embodiment, the weir device includes a first chamber into which oil from the warm reservoir is routed. A first pump (66B) is located in this first chamber, which routes the heat transfer fluid to the first pyrolysis reactor (70). The heat transfer fluid exiting the first pyrolysis reactor enters the same chamber. A weir, such as a Vasin weir, ensures sufficient head (net suction head) to avoid cavitation and gas entrainment during pumping of the heat transfer fluid to the first pyrolysis reactor (70). The weir forms an enclosure for the first chamber and recirculates the fluid within the chamber. This ensures uniformity of the fluid temperature within the chamber and high tolerance to fluctuations in the flow rate of the fluid coming from the warm reservoir.

[0125] Excess heat transfer fluid overflows the weir and flows into the subsequent chamber. Similar to the first chamber, subsequent chambers are equipped with additional pumps (66B) to pump the heat transfer fluid to the preheater (74) and collect the return. Similarly, additional weirs ensure that the pump (66B) pumping the fluid to the preheater has sufficient NPSH and does not entrain gas. Finally, the last chamber includes another pump to pump the heat transfer fluid to the cold reservoir (63). Starting and stopping of such pumps can be handled automatically by level switches, so that the pumps only start when the liquid level in the last chamber exceeds a predetermined height.

[0126] Unlike a series configuration, the weir device (78) allows for different flow rates of heat transfer fluid to each device. Unlike a parallel configuration where all devices share the same supply (warm reservoir), the weir device allows for higher temperature heat transfer fluid to be supplied to devices requiring higher temperature and higher correlation (i.e., to maintain a constant temperature of the heat transfer fluid when compared to the temperature of successive chambers).

[0127] Thus, the weir device allows for greater flexibility and effectiveness when compared to standard parallel or series configurations.

[0128] In another embodiment, such a device can be located within the warm reservoir itself, thereby eliminating the need for a pump to deliver the heat transfer fluid to the weir device. In another embodiment, the warm, cold, and hot reservoirs can be located within a solar field, with the pyrolysis plant located a predetermined distance from the solar field. In such a case, a buffer reservoir is required to avoid failure of the pyrolysis process in the event of a problem with the delivery of the heat transfer fluid.

[0129] In such cases, the weir device also acts as a buffer reservoir.

[0130] It should be understood that many other different modifications of the weir device are possible, such as allowing for more chambers to manage more devices heated by the heat transfer fluid.

[0131] Advantageously, all devices receiving heat transfer fluid are located at different height levels, resulting in a minimum number of heat transfer pumps required.

[0132] More precisely, according to this embodiment, the first device receiving the heat transfer fluid from the pump 66 is placed at the highest height level, and the device receiving the heat transfer fluid leaving the first device is placed at a lower height level, so that the fluid can flow into the device by gravity, thus eliminating the need for an additional pump.

[0133] This is advantageous because moving parts that are on hot fluids and may also exhibit high melting points may be particularly sensitive and require special measures for proper start-up and maintenance in the event of a malfunction. Furthermore, this method allows the heat transfer fluid in the device to be at atmospheric pressure, simplifying device design and reducing costs. Last but not least, the lack of pressurization makes it safer, as spills due to breakage are reduced if the heat jacket is accidentally broken.

[0134] According to a preferred embodiment, all heat transfer fluid reservoirs are located at the lowest level.

[0135] The preheater (74) can be any device capable of heating and preferably partially or totally melting the essential plastic material.

[0136] Examples of such devices include single screw extruders, twin screw extruders, or more generally screw devices having a jacket or equivalent means through which the plastic material can be delivered and through which a heat transfer fluid can flow.

[0137] Optionally, the heat transfer fluid also flows inside the screw, thereby improving the effectiveness of the device.

[0138] Preferably, such a device can be made substantially gas-tight so that gases within the first pyrolysis reactor (70) cannot exit the pyrolysis reactor (70). To achieve this result, the same plastic melt flowing between the screw and barrel can be used as a means to achieve gas-tightness.

[0139] The preheating device may be equipped with a degassing device for discharging water vapor and other gases that are produced, such as hydrogen chloride (HCl). For this purpose, it may be advantageous to supply the preheating device with additives that promote the production of hydrochloric acid or salt out hydrochloric acid, in addition to the essential plastic material. These additives are preferably compounds of elements of groups IA and IIA. More preferred are oxides, hydroxides, carbonates, silicates, and aluminosilicates of groups IA and IIA. More preferred are calcium oxide, calcium hydroxide, calcium carbonate, sodium oxide, sodium hydroxide, sodium carbonate, potassium oxide, potassium hydroxide, potassium carbonate, and sodium aluminosilicate.

[0140] The preheating temperature is 120° C. to 430° C., preferably 150° C. to 320° C., and more preferably 180° C. to 220° C. The residence time in the preheating device is preferably less than 20 minutes, more preferably less than 4 minutes, and particularly less than 1 minute.

[0141] Therefore, one embodiment of the present invention is a process for producing at least pyrolysis oil from essential plastic material, comprising the following steps: p) before step e), heating the essential plastic material with the heated first heat transfer fluid (F1); Further includes:

[0142] According to such an embodiment, preferably in step p) the essential plastic material is at a temperature of 120°C to 430°C, more preferably 150°C to 320°C, even more preferably 180°C to 220°C, and the average residence time in step p) is preferably less than 20 minutes, even more preferably less than 4 minutes, in particular less than 1 minute.

[0143] The first pyrolysis reactor (70) can be any reactor capable of receiving the essential plastic feedstock and bringing it to pyrolysis conditions (temperature and pressure).

[0144] The first pyrolysis reactor for the pyrolysis of essential plastic materials can be operated in both batch mode, continuous mode and semi-continuous mode, in which the essential plastic material is continuously fed and the generated vapors are continuously extracted while the solid residue is retained in the pyrolysis reactor.

[0145] When the amount of solid residue in the reactor exceeds a certain threshold, or at predetermined time intervals, for example, at a frequency ranging from 2 days to 10 days, the solid material contained in the reactor is removed.

[0146] Preferably, the reactor is operated in a continuous or semi-continuous mode, more preferably in a semi-continuous mode.

[0147] The pyrolysis process of the present invention is not limited to any particular type of reactor.

[0148] In particular, horizontal or vertical, stirred or unstirred reactors, kiln reactors or screw reactors can be used, fluidized bed reactors being not preferred.

[0149] Stirred reactors include continuous stirred reactors (CSTRs) and multi-zone reactors. Plug flow reactors (PFRs) can also be used, preferably stirred to facilitate heat transfer.

[0150] As a continuously stirred reactor (CSTR), it is possible to use a fully packed reactor (meaning that there is essentially no gas phase above the reaction products such as the processed plastic melt and char) or a reactor with a separated phase, i.e. a free surface, including the gas phase and other possible phases such as liquid and any solid char produced.

[0151] Preferably, the reactor is a stirred reactor with a free surface.

[0152] The residence time of the essential plastic material (M1) in the first pyrolysis reactor is at least 2 minutes, which is sufficient in any case to produce a gaseous fluid (M2) containing hydrocarbons. This means that in any case the residence time must be sufficient to produce a gaseous fluid, and this time can exceed 2 minutes. This time may vary depending on the composition of the essential plastic material fed to the reactor, but if no gas is generated, a person skilled in the art will have no difficulty in increasing the residence time so that this condition is met.

[0153] The temperature of the material in the pyrolysis reactor can be measured by any method known in the art, such as a thermocouple with opposing membranes fitted to the inner surface of the reactor to reduce fouling; a thermowell thermocouple for more precise measurements inside the reactor; a thermocouple measuring the temperature of metal near the polymer-wetted surface of the reactor; or a non-contact measurement system, such as an infrared device. Multiple systems can be used simultaneously to improve reliability.

[0154] The temperature can be controlled by acting on the heat power introduced into the reactor, the heat power being obtained by the flow of said heat transfer fluid within the reactor.

[0155] Components in contact with such heat transfer fluids are separated from components in contact with process fluids (plastic inlets, liquefied plastics, char, gases produced by pyrolysis, etc.).

[0156] Preferably, the heat transfer fluid flows within the jacket. Optionally, the heat transfer fluid also flows within the stirrer, heating the stirrer as well.

[0157] Preferably, the heat transfer fluids F1 and / or F2 are molten salts. Any molten salt can be used in the present invention.

[0158] The heat transfer fluid may be low melting point alkali metals from Groups (III)A, (IV)A, and (V)A (metal alloys containing elements from Groups (III)A through (V)A of the periodic table), and metal alloys based on Groups (III)A, (IV)A, and (V)A. Alkali metals include cesium (mp 28°C), lithium (mp 180°C), potassium (mp 63°C), rubidium (mp 39°C), and sodium (mp 98°C); low-melting metals from groups (III)A, (IV)A, and (V)A include indium (mp 157°C), gallium (mp 30°C), bismuth (mp 271°C), lead (mp 327°C), and tin (mp 232°C); (III)A, (IV)A, and (V)A-based metal alloys are metal alloys containing at least 70% by weight of elements from groups (III)A through (V)A of the periodic table, such as wood's metal (50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium, mp 70°C), field's metal (32.5% Bi, 51% In, and 16.5% Sn, mp 62°C), rose metal (50% bismuth, 25–28% lead, 22–25% tin, mp 98°C), pewter metal (tin (85–99%), antimony (approximately 5–10%), copper (2%), bismuth, mp approximately 170–240°C), cast metal (40% Bi, 60% Sn, mp 170°C), lead-antimony eutectic (12% Sb, 88% Pb, mp 252°C), lead-tin eutectic (61.9% Sn, 38.1% Pb, mp 184°C), and galinstan (68.5% Ga, 21.5% In, and 10.0% Sn, mp -19°C).

[0159] Preferred low melting alkali metals are sodium and potassium; preferred Group (III)A, (IV)A, and (V)A metals are lead, bismuth, indium, gallium, and tin; preferred Group (III)A, (IV)A, and (V)A-based metal alloys are wood metal, field metal, rose metal, pewter metal, cast metal, and galinstan.

[0160] According to one embodiment, the molten salt is a molten salt of Groups IA and IIA of the periodic table, preferably sodium nitrate, sodium nitrite, potassium nitrite, potassium nitrate, lithium nitrate, calcium nitrate, or mixtures thereof.

[0161] According to one embodiment, the molten salt that can be used is a nitrate / nitrite mixture, in particular a mixture of potassium nitrate and sodium nitrate, optionally with the addition of sodium nitrite and calcium nitrate.

[0162] According to one embodiment, such a nitrate / nitrite mixture is a eutectic mixture of 53 wt% potassium nitrate, 40 wt% sodium nitrite, and 7 wt% sodium nitrate; or according to another embodiment, such a K / Na nitrate / nitrite mixture is a eutectic mixture of 45.5 wt% potassium nitrate and 54.5 wt% sodium nitrite.

[0163] According to one embodiment, such a nitrate / nitrite mixture is the so-called "solar salt", characterized by 60 wt% sodium nitrate and 40 wt% potassium nitrate.

[0164] According to one embodiment, such a nitrate / nitrite mixture is the so-called "Hitec XL" and is characterized by 7 wt% sodium nitrate, 45 wt% potassium nitrate, and 48 wt% calcium nitrate.

[0165] According to one embodiment, the nitrate / nitrite mixture is 100 wt% lithium nitrate.

[0166] According to one embodiment, the nitrate / nitrite mixture is 25 wt% lithium nitrate, 25 wt% sodium nitrate, and 50 wt% potassium nitrate.

[0167] According to one embodiment, the molten salt is a mixture of chlorides such as sodium chloride, a mixture of sodium chloride and potassium chloride, and optionally magnesium chloride.

[0168] According to a further embodiment, the heat transfer fluid is a molten salt containing a metal fluoride of Group IA or Group IIA, preferably lithium fluoride, sodium fluoride, potassium fluoride, and calcium fluoride. Even more preferably, the heat transfer fluid is a molten salt containing sodium nitrite, sodium nitrate, and potassium nitrate. Even more preferably, the heat transfer fluid is a molten salt containing sodium nitrate and potassium nitrate.

[0169] Preferably, the heat transfer fluid has a low melting point, more preferably at most 340°C, even more preferably at most 270°C, even more preferably at most 240°C.

[0170] Preferably, the heat transfer fluid has a high decomposition temperature, more preferably at least 400°C, even more preferably at least 450°C, even more preferably at least 490°C, and most preferably at least 540°C.

[0171] According to one embodiment, the melting point of the heat transfer fluid is at least 60°C, preferably above 80°C, more preferably above 105°C.

[0172] Preferably, the heat transfer fluid has a low chloride content, preferably less than 1000 ppm by weight of chloride, more preferably less than 100 ppm by weight of chloride.

[0173] According to one embodiment, any component of the process intended to contain molten salt, such as a reactor, coker, preheater, valve, etc., can be drained by gravity. For example, the reservoirs (hot, cold, warm) can be located at the lowest point so that the heat transfer fluid will drain into the reservoir by gravity in the event of a failure (such as failure of the molten salt pump 66, sudden interruption of the electrical energy source, etc.). According to another embodiment, any component containing molten salt characterized by the presence of moving parts (such as valves) or large aspect ratios (e.g., pipes) is equipped with electrical heat tracing that can be activated before starting the plant to melt the heat transfer medium.

[0174] The solar collector assembly (SCA) can be of any type. According to one embodiment, the solar collector is "single focus," meaning that the sun's rays are essentially reflected into a focal zone of limited size. Examples of "single focus" include parabolic dishes and power towers. According to another embodiment, the solar collector is "linear," meaning that the sun's rays are essentially reflected into a focal zone that is linear. Examples of such solar collectors include parabolic troughs and linear Fresnels. There are also several specific types of parabolic troughs and linear Fresnels that can be used in the present invention, such as compact linear Fresnel reflectors (CLFRs) or "enclosed trough systems."

[0175] Preferably, the solar collector is a parabolic trough or a linear Fresnel, in the latter case especially a compact linear Fresnel.

[0176] Thus, according to one embodiment of the process of the present invention, the heating in steps a) and b) is performed by at least one solar collector assembly comprising a parabolic trough, a linear Fresnel, or a combination thereof. According to a preferred embodiment of the process of the present invention, the heating in steps a) and b) is performed by at least one solar collector assembly consisting of a parabolic trough, a linear Fresnel, or a combination thereof.

[0177] The solar radiation collected by such collectors is reflected onto a so-called solar receiver. In one embodiment, such a solar receiver consists of a heat exchanger in which a heat transfer fluid is heated. Typically, in such receivers, the fluid flows through tubes that are heated by the solar radiation.

[0178] In another embodiment, such a solar receiver consists of a tube through which sunlight is irradiated. Typically, the tube is made of metal and is called an "absorber." The tube is coated with a selective coating that maximizes absorption of sunlight while minimizing heat loss due to infrared radiation. The glass tube surrounding the absorber tube is transparent to allow sunlight to pass through. A high vacuum is created between the two tubes to limit convective heat loss. Degassing nozzles and / or getters may be added to maintain this vacuum for extended periods of time.

[0179] The end of the solar receiver is equipped with a bellows that takes into account the difference in thermal expansion between the glass and metal materials.

[0180] The solar collectors and associated receivers can be assembled in parallel, in series, or in a combination of parallel and series, with a combination of parallel and series configurations being preferred.

[0181] In some cases, particularly linear Fresnel (and compact linear Fresnel) reflectors, a single receiver can receive concentrated solar radiation from multiple reflectors.

[0182] The concentration factor (sometimes referred to as the "concentration ratio") is the ratio of the radiant power density at the receiver divided by the radiant power density of the unconcentrated sun, and is therefore the factor by which the incident energy flux is optically enhanced at the receiving surface. The concentration factor according to the present invention is 8 to 1000, more preferably 10 to 100, and even more preferably 15 to 80.

[0183] According to one embodiment of the present invention, the concentration of the solar collector assembly 62 heating the hot reservoir 65 is higher than the concentration of the solar collector assembly 61 heating the warm reservoir 64 .

[0184] Thus, according to one embodiment of the process of the present invention, the concentration of the at least one solar collector assembly in step b) is higher than the concentration of the at least one solar collector assembly in step a).

[0185] The hot, warm and cold reservoirs can be any vessel that can be filled with a heat transfer fluid, such as a vertical or horizontal tank, and are advantageously insulated to limit heat loss.

[0186] According to one embodiment, the heat transfer fluid pump 66 is located within the reservoir.

[0187] According to one embodiment, the level of the heat transfer fluid in the hot or warm reservoir is monitored to limit the pyrolysis duty if the level of the heat transfer fluid in the reservoir becomes too low.

[0188] According to one embodiment of the present invention, there is also an additional reservoir of heat transfer fluid to deliver heat transfer fluid at more than two temperatures to the pyrolysis device.

[0189] According to one embodiment, such first pyrolysis reactor is preferably an essentially cylindrical vertical vessel.

[0190] Preferably, the upper and lower ends of the first pyrolysis reactor are conical, elliptical or semi-elliptical, which allows for better recirculation and reduces fouling, which is a significant problem in pyrolysis reactors.

[0191] Preferably, the first pyrolysis reactor 70 has at least an agitator. Such an agitator should be of sufficient size to ensure that at least the entire volume of the reactor filled with liquid and solid phases is continuously or semi-continuously wiped (e.g., not necessarily gas phase). Preferably, the agitator should also be capable of periodically moving material near the reactor walls to clean surfaces and reduce fouling.

[0192] Examples of such agitators include anchor or ribbon agitators, or possibly turbine agitators.

[0193] The rotation speed of such a stirrer is typically 1 to 300 rpm, preferably 5 to 120 rpm.

[0194] According to some embodiments, more than one stirrer can be used, advantageously with different stirring speeds. One simple way to achieve this is to leave one stirrer free to rotate, so that it is entrained in the fluid at a rotation speed lower than the rotation speed of the active stirrer, but higher than zero.

[0195] "Condenser" means any device capable of receiving a fluid in a gaseous state and removing sufficient heat from said fluid to produce at least a portion of the fluid in a liquid state.

[0196] An example of this device is a condenser that includes a coil through which a heat transfer fluid flows that can remove heat from the gaseous fluid being treated.

[0197] Other methods of removing heat may also be used, for example, the condenser may alternatively or in combination be provided with a jacket through which the heat transfer fluid flows to remove heat.

[0198] Flooded condensers can also be used to advantage, in which the condenser is partially immersed (or flooded) by the liquid phase produced. The condensing power is adjusted by varying the height of said liquid phase, since only the unimmersed coils can absorb heat from the vapor being condensed. This effectively adjusts the capacity of the condenser.

[0199] Alternatively, the condenser can consist of a distillation column. In this case, condensed liquid originating from the column's condenser is counterflowed by gravity or by a pump within the column, condensing the vapor within the column. This also improves the fractionation of the incoming vapor; that is, at each stage, heavier materials are concentrated in the liquid phase and lighter materials in the vapor phase, resulting in a better separation of the high-boiling components that are condensed from the low-boiling components that remain in the vapor phase. Furthermore, the vapor scrubbing provided by the column allows any solid particles present in the incoming vapor to be separated and recombined in the liquid phase.

[0200] The pyrolysis vapor condenser can be a single condenser or multiple condensers in series or parallel. Preferably, when more than one condenser is used, two to four condensers are used in series, more preferably three condensers are used in series.

[0201] When the condensers are in series, each condenser receives non-condensable gases from the previous condenser, with the first condenser receiving pyrolysis vapors.

[0202] In this preferred mode, the condenser receiving the pyrolysis vapor (first condenser) operates at a higher temperature than the second condenser receiving the non-condensed vapor from the first condenser. If there are more condensers, the next condenser (e.g., third condenser) receives the non-condensed vapor from the previous condenser and operates at a lower temperature.

[0203] According to a preferred method, a portion of the fluid in liquid state condensed in the at least one condenser is recycled to the first pyrolysis reactor. Preferably, the fluid recycled to the reactor is taken from the first condenser.

[0204] According to one embodiment, if more than one condenser is used, heat is removed by the first condenser using a heat transfer fluid, as previously described in FIG. 5 (condenser 72A).

[0205] After passing through the at least one condenser, the uncondensed hydrocarbon-containing fluid (hereinafter defined as residual gas) advantageously contains at least 40% by weight of light hydrocarbons (C1-C5) and can be advantageously used as fuel gas. A portion of this gas can be combusted to provide additional heat energy, which can be useful in the thermal cracking process and related devices, especially those requiring high temperatures, such as the second thermal cracking reactor and the coker. For this purpose, for example, a gas heater can be used, which regulates the temperature of the heat transfer fluid circulating in the reactor jacket. Alternatively or in combination, this residual gas can be advantageously used to supply a refinery plant, such as a cracking plant.

[0206] According to the invention, the fluid in a liquid state after condensation in the at least one condenser is quantitatively at least 10% by weight, preferably 20% to 92% by weight, more preferably 30% to 85% by weight, even more preferably 40% to 75% by weight, based on the weight of the essential plastic material supplied. When multiple condensers are used, this amount is calculated by adding up the weights of the liquid produced in each condenser.

[0207] According to the present invention, after condensation in the at least one condenser, at least a fluid is formed, which is in a liquid state and comprises hydrocarbons having a normal boiling point of 25°C or higher, preferably 40°C or higher, more preferably 80°C to 220°C.

[0208] Preferably, at least the first pyrolysis reactor operates at atmospheric or superatmospheric pressure (i.e., at or above atmospheric pressure). According to one embodiment, the pressure is between 1.1 and 20 bara, more preferably between 2 and 10 bara, and even more preferably between 2.2 and 6 bara.

[0209] Preferably, the temperature reached by the essential plastic material in the first pyrolysis reactor is 330°C to 580°C, preferably 340 to 540°C, more preferably 360 to 500°C, even more preferably 380 to 480°C, and even more preferably 410 to 450°C.

[0210] Any technique known in the art can be used to maintain the pressure in the first pyrolysis reactor at a defined value. The maintained pressure may have different values ​​as a function of the pyrolysis temperature. According to a first method, the pressure can be maintained at a specified value by adjusting the heat extracted from a condenser located downstream of the reactor and in fluid communication with the reactor. In this mode, the amount of heat removed from the condenser increases, resulting in greater condensation of the vapor. This condensation causes the evaporated substance to change from a gaseous state to a liquid state with a much greater density, thereby reducing the pressure.

[0211] Alternatively, the pressure can be controlled by introducing a gas such as nitrogen, argon, or water vapor and adjusting the flow rate of the gas with a valve. According to one embodiment, such a gas is introduced into the first pyrolysis reactor and also acts as an inert gas (i.e., a gas that does not directly participate in the pyrolysis reaction and can displace oxygen present in the reactor when the reactor is open to the atmosphere, for example, during maintenance or before start-up).

[0212] According to a preferred embodiment, the pressure can be controlled by adjusting the flow rate of the non-condensed gas stream (the gas stream of the last condenser if more than one condenser is used in series).

[0213] According to one embodiment, the pyrolysis of the essential plastic material of the present invention is carried out in the substantial absence of oxygen, where "substantially free of oxygen" is defined in the sense given above.

[0214] Therefore, according to this embodiment, the process for producing at least pyrolysis oil from essential plastic material is also characterized in that steps f) and h) are carried out in the substantial absence of oxygen.

[0215] The heat output to the first and second pyrolysis reactors can be adjusted by controlling the flow rate, temperature, or both, of the heat transfer fluid.

[0216] Advantageously, the thermal cracking process of the present invention produces products that are particularly useful for use as jet fuel or virgin naphtha, which are particularly suitable for steam cracking for the production of monomers of industrial interest or for the synthesis of polymers.

[0217] Preferably, the second pyrolysis reactor operates at a temperature higher than that of the first pyrolysis reactor, and more preferably, the temperature difference between the second and first pyrolysis reactors is at least 10°C, more preferably between 30°C and 300°C, and even more preferably between 60°C and 250°C.

[0218] According to another embodiment, the second pyrolysis reactor always operates at a temperature at least 10°C higher than the temperature of the first pyrolysis reactor, and in further conditions, its temperature is between 400°C and 650°C, preferably between 440°C and 550°C, more preferably between 460°C and 530°C; if the lowest temperature in these ranges is lower than the temperature of the first pyrolysis reactor plus 10°C, the latter (T, which is the temperature of the first pyrolysis reactor + 10°C) is considered as the lower range.

[0219] The present invention therefore includes a process for producing at least a pyrolysis oil from essential plastic material, wherein the gaseous effluent of a first pyrolysis reactor before condensation is transferred to a second pyrolysis reactor, and the gaseous stream is heated to a temperature at least 10°C higher than the temperature of the essential plastic material in the first pyrolysis reactor.

[0220] Therefore, according to one embodiment of the present invention, there is provided a process for producing at least pyrolysis oil from essential plastic material, wherein the temperature difference between the temperature T2 of step b) and the temperature T1 of step a) is at least 10°C, even more preferably between 30°C and 300°C, and even more preferably between 60°C and 250°C.

[0221] The residence time of the pyrolysis vapor in the second pyrolysis reactor is calculated by dividing the volume occupied by the vapor in the reactor by the volumetric flow rate, and is at least 10 seconds, preferably 30 seconds to 6 minutes, and more preferably 1 minute to 4 minutes.

[0222] Preferably, the second pyrolysis reactor is catalytic. More preferably, the effluent in gaseous state is in relative motion with respect to the solid catalyst in contact with the effluent in gaseous state, the relative motion being at a speed of at least 0.5 m / s, more preferably 2 to 50 m / s.

[0223] Any pyrolysis catalyst known in the art may be used, including in particular zeolites.

[0224] The second pyrolysis reactor can operate at the same pressure as the first pyrolysis reactor 70 or at a lower pressure. Preferably, the second pyrolysis reactor operates at a pressure comprised between atmospheric pressure and the pressure of the first pyrolysis reactor. More preferably, the second pyrolysis reactor operates at a pressure comprised between the pressure of the first pyrolysis reactor and the same pressure reduced by 10,000 Pa.

[0225] Advantageously, the first pyrolysis reactor, as well as the second pyrolysis reactor, can be more than one unit, which allows for easy scaling up of the process.

[0226] Furthermore, if the liquid / solid / semi-solid residue (char) from the first reactor accumulates in one unit, it is possible to shut down such unit, discharge the char, clean the unit, and restart it. By programming the production schedule for each first pyrolysis reactor, it is possible to schedule periodic shutdowns of individual units for maintenance, one by one, thereby stabilizing the entire pyrolysis process over the long term.

[0227] Advantageously, the second pyrolysis reactor can be fed with outlet pyrolysis vapors from more than one first pyrolysis reactor unit. Preferably, gaseous vapors from 2 to 20 first pyrolysis reactor units are fed to a single second pyrolysis reactor. More preferably, 3 to 8 units.

[0228] Similarly, the char produced by more than one first pyrolysis reactor unit is fed to a single char processing device (such as a "coker").

[0229] For example, a heat transfer fluid stored in a hot reservoir and a warm reservoir can be used to maintain the pyrolysis process when the solar radiation power is too low to provide the necessary heat, such as after sunset or on cloudy or rainy days. Typically, the temperature of the reservoirs is not changed to ensure stable pyrolysis and not affect the quality of the resulting pyrolysis oil.

[0230] Instead, the flow rate of heat transfer fluid in the charge section (solar collector assembly) can be stopped or reduced while the flow rates of heat transfer fluid from the hot and warm reservoirs remain unchanged (or are slowly reduced). In this way, the heat transfer fluid level in the hot reservoir will drop, and possibly the warm reservoir level as well (depending on the relative mass flow rates), while the cold reservoir level will rise.

[0231] The larger the capacity of the reservoir, the longer the period during which the process can be run with an additional power source of such "release." In particular in such cases, the size of the reservoir can become so large that it is convenient to divide the reservoir into more units, which can be operated in parallel, for example.

[0232] It is also possible for the heat transfer fluid to exchange thermal energy with solid materials that can maintain the temperature of the heat transfer fluid, such as concrete, sand, stone, etc., thereby increasing the amount of energy stored and thereby increasing the operating time for full drain. A simple way to implement this embodiment is to place a large amount of such material within the reservoir, its walls, or its base.

[0233] The additional power source is an energy source different from concentrated solar power (CSP) and can be used, for example, for emergency shutdown or startup of the plant. Alternatively, or in combination, such additional power source can be used, for example, to stabilize or increase pyrolysis production. Such power source can be, for example, so-called renewable power sources (wind, solar, tidal, nuclear, hydro, biomass, etc.) or fossil fuels (carbon, oil, shale, natural gas).

[0234] Preferred such additional power sources are solar, biomass, nuclear, and natural gas, with natural gas being particularly preferred.

[0235] In the case of natural gas, gas heaters are particularly preferred. More preferably, the gases combusted in the gas heaters comprise residual gases from the pyrolysis process (i.e., non-condensable pyrolysis gases, as previously described, e.g., stream 55 in Figure 11).

[0236] Such additional power sources may be placed in series or parallel with the heat transfer fluid being heated.

[0237] FIG. 11 shows some embodiments of the invention that include such additional power sources in parallel (68A) or in series (68B) and (68C).

[0238] A parallel configuration means that the power source draws a portion of the heat transfer fluid from a cooler reservoir (cold or warm) in parallel with the solar collector assembly, heats the fluid to a target temperature (typically the temperature of the destination reservoir), and supplies the heat transfer fluid to said destination reservoir, which can be warm reservoir (64) or hot reservoir (65) if the fluid is drawn from cold reservoir (63), or hot reservoir (65) if the fluid is drawn from warm reservoir (64).

[0239] In the case of a series configuration, the inlet of such further power source is the outlet of the solar collector assembly, whose outlet is the inlet of the receiving heat transfer fluid reservoir. Referring to Figure 11, one embodiment of this solution is as follows: heat transfer fluid from the warm reservoir (64) is routed to the hot solar collector assembly (62), then to the further power source (68B), and then to the hot reservoir (65).

[0240] Alternatively, in a constant series configuration, the inlet of such additional power source is the outlet of the hot reservoir and the outlet is the discharge circuit of the hot reservoir (the circuit feeding the second pyrolysis reactor and optionally the coker). This is the most preferred option.

[0241] Referring to Figure 11, one embodiment of this solution is as follows: heat transfer fluid from a hot reservoir (65) is sent to a further power source (68C) and then to duty (second pyrolysis reactor 71).

[0242] Preferably, if such an additional power source is present, its power is between 3% and 40%, more preferably between 6% and 20%, and even more preferably between 8% and 15% of the power supplied by the warm solar collector assembly. [Example]

[0243] This example reports process simulations using a dual heat transfer fluid driven process (double loop) of the present invention compared to a conventional single fluid driven process (single loop). These are prophetic examples and the present tense is used for clarity.

[0244] Example 1 (present invention) It is a solar pyrolysis process driven by two fluids of the same composition (double heat transfer fluid loop).

[0245] The process corresponding to this example is shown in FIG.

[0246] The heat transfer fluid is a solar mixture of molten salts ("solar salt") containing 60 wt% sodium nitrate and 40 wt% potassium nitrate.

[0247] The solar collector and receiver (61), (62) comprise a Luz (SEGS) LS-2 parabolic trough collector (PTC) with a 70 mm outer diameter evacuated tube receiver. This model has a width W of 5.0 m and a length L of 7.8 m. Detailed characteristics and characterization of such a parabolic trough collector are reported in Dudley V, Kolb G, Sloan M, Kearney D., "SEGS LS2 solar collector - test results." The 958 Report of Sandia National Laboratories, SAN94-1884, 1994 is briefly reported in Tables 1 and 2 of Bellos, Evangelos & Tzivanidis, Christos, "A detailed exergetic analysis of parabolic trough collectors," Energy Conversion and Management, (149) 275-292, 2017 doi: 10.1016 / j.enconman.2017.07.035. This paper (hereafter referred to as the Bellos paper) is also used for detailed energy and exergy balances.

[0248] Code was written to replicate the model developed in Bellos' paper and tested against the validation Sandia National Laboratories test case 4 (Table 4 on page 11 of Bellos' paper). The results were in excellent agreement with those shown in Tables 4 and 5 of Bellos' paper for this test case, and were shown to be very close to the experimental values.

[0249] The flow rate of molten salt in the solar collector assembly (62) is 24.2 kg / s. The receivers in the solar collector assembly are arranged in 20 parallel rows, each receiving 24.2 / 20 = approximately 1.21 kg / s of solar salt. Each row contains 19 receivers. This is the number of receivers (each 7.8 m long) required to raise the temperature from 485°C to 565°C. Calculations were performed as follows: the ambient conditions (ambient temperature, air temperature, solar temperature, and incidence angle) were as per Table 3 in Bellos's paper, but the specific humidity (humidity ratio) was 0.01 (i.e., 10 g of water per kg of air). Furthermore, the radiative energy of approximately 900 W / m reported in Table 4 in Bellos's paper was used. 2 is quite high and is only available in certain regions of the Earth and for limited periods of time, so direct solar radiation (G b ) is 650W / m 2 The properties and optical characteristics of the PTC module are given in Tables 1 and 2 of Bellos' paper. The equations used are those given in Bellos' paper.

[0250] The physical properties of the "Solar Salt" heat transfer fluid are calculated by the following formulas taken from "Solar Salt - thermal Property Analysis" by A. Bonk et al., Scientific Report DLR-FB-2021-19 31.08.2021, German Aerospace Center:

[0251] [Table 1]

[0252] The heat capacity was considered to be independent of temperature and a constant value was used due to the large discrepancies in measurements of this parameter.

[0253] To perform the calculations, Bellos used software called "Engineering Equation Solver." However, the most difficult equation was a quartic equation (a fourth-order polynomial) for calculating the cover temperature ("Tc" in Kelvin). It had only two real solutions, only one of which was positive (hence, only this solution was important and had to be selected). It required two more iterations (outlet temperature and Tc), but in any case converged very quickly and no alternative solutions existed. Therefore, it turned out to be easily solvable with an algorithm in a programming or scripting language.

[0254] Simulations are performed for each solar receiver, starting with the first one receiving molten salt from the cold reservoir. The calculated temperature of the molten salt at the outlet of the first receiver is set as the inlet temperature of the molten salt at the inlet of the second receiver. It is then possible to calculate the temperature of the molten salt at the outlet of the second receiver, which becomes the inlet temperature of the molten salt at the third receiver, etc. In this way, the number of receivers needed to reach the target molten salt temperature can be calculated (in this case, 19 receivers per line are needed to reach 565°C).

[0255] The total energy and exergy flow is calculated by adding the contribution of each receiver.

[0256] The solar assembly (62) receives solar salt from the warm reservoir (64), heats the solar salt to a target temperature, and then delivers the hot solar salt to the hot reservoir (65). From the hot reservoir, the solar salt is delivered to the units requiring the highest operating temperatures: the coker (76) and the secondary pyrolysis reactor (71).

[0257] The molten salt is sent directly to the coker, i.e., without a weir device. The weir device allows fine control of the temperature and high flow rate (not required in the coker), but at the expense of lower values. On the other hand, the coker has the advantage of a higher temperature of the molten salt in the jacket.

[0258] The molten salt supply to the first pyrolysis reactor (70) and the second pyrolysis reactor (71) is implemented using weir devices (78) and (79). These weir devices have two chambers. The first receives the hot molten salt and sends it to the jacket of the pyrolysis reactor (e.g., using a submersible pump). Unlike the weir devices shown in Figures 6 and 7, this molten salt return from the reactor is sent to the second chamber. The flow rate of the molten salt circulated to the pyrolysis reactor is much higher than the flow rate of the hot molten salt delivered from the reservoir. This high flow rate is desirable to reduce the temperature difference within the pyrolysis reactor and maximize heat transfer. Therefore, some of the molten salt in the second chamber overflows the weir between the first and second chambers and falls into the first chamber. This allows the pump in the first chamber to deliver the required flow rate while maximizing the temperature of the solar salt sent to the pyrolysis reactor.

[0259] Molten salt from the coker is delivered to a weir device (79) that feeds the molten salt into the second pyrolysis reactor (71). The molten salt exiting the weir device (79) is sent to the warm reservoir (64), closing the "hot loop" of the heat transfer fluid.

[0260] The solar receiver (61) receives solar salt from the cold reservoir (63), heats it to the target temperature (485°C in this case), and then sends the warm solar salt to the warm reservoir (64). The solar receiver (61) has 75 parallel lines, each containing eight receiver tubes arranged in series (each 7.8m long). Thus, the flow rate in each line is 91.6 / 75 = 1.22 kg / s, which is very similar to the flow rate in the hot receiver (62).

[0261] For safe operation of the solar collector assembly, it is necessary to ensure sufficient flow rate within the receiver tubes, particularly to reduce temperature differences and associated tube bending in sections of the tube exposed to different solar irradiation intensities.

[0262] The solar salt is transferred from the warm reservoir to the first pyrolysis reactor (70) by a weir device (78).

[0263] A portion of the solar salt leaving the first pyrolysis reactor is sent to a high-temperature oil exchanger (81), which is a heat exchanger in which the "cold" molten salt from the first pyrolysis reactor heats an organic heat transfer fluid called "oil" (Eastman Merotherm SH) to approximately 320°C.

[0264] The use of low-temperature organic heat transfer fluids is advantageous in that their low melting points eliminate the risk of solid salt freezing in poorly circulated or poorly insulated zones. Furthermore, electrical tracing is not required for the oil jacket lines. Because the required duty is much less than that of the first pyrolysis reactor, only a portion of the molten salt leaving the first pyrolysis reactor is delivered to the high-temperature oil exchanger.

[0265] The solar salt exiting the first pyrolysis reactor is collected in a low temperature molten salt reservoir (63), closing the molten salt "hot loop."

[0266] The heat losses in the solar receiver (62) are calculated using the model of Bellos mentioned above. The heat losses in the so-called headers and connecting pipes of the solar collector assembly are ignored as they are considered negligible compared to the heat losses in the receiver.

[0267] The heat losses in the molten salt circuit, including the coker, the second pyrolysis reactor, and associated connecting piping, are lumped into a single heat loss (83) called "Enthalpy Loss 2." The heat losses in the molten salt circuit, including the first pyrolysis reactor, the hot oil exchanger, and associated connecting piping, are lumped into a second single heat loss (82) called "Enthalpy Loss 1."

[0268] The exergy balance is calculated by considering the inner wall through which the molten salt circulates as the control volume, with the exception of the solar collector assembly (SCA), which is calculated according to the model and formula of Bellos mentioned above. Therefore, for the SCA only (i.e., exergy input), the incident radiation from the sun is the boundary.

[0269] Since there is no mass flow at the selected boundary, the only exergy flow is: Incoming solar radiation exergy (sign "+") Exhausted exergy related to heat flow Pyrolysis reactors, cokers, high-temperature oil exchangers "Enthalpy Loss" Heat loss lumped into the device.

[0270] The temperature at the boundary can be assumed to vary linearly with the heat flow. This assumption is more realistic considering that the temperature change along the heat flow boundary is small compared to its absolute value (in Kelvin). Therefore, the exergy flow at such a boundary can be calculated as follows: Equation 3

[0271] TIFF2026505342000005.tif17157In formula, T1 and T2 are the temperatures at the beginning and end of the heat exchange boundary in Kelvin. ·T0 is the reference temperature (here 298K). ·ΔQ is the heat flow rate. ·Δχ is the exergy flow.

[0272] T1 and T2 correspond to the inlet and outlet temperatures, except when using a weir device. In fact, in this case, the recirculation pump in the weir device reduces the temperature difference between the inlet and outlet of the recirculating molten salt stream (in the limit of infinite flow, T1 is equal to T2).

[0273] The table below shows the detailed calculation results and the calculation results of the total heat flow and total exergy flow obtained by adding up the contributions of all the units.

[0274] [Table 2]

[0275] If the sum of all exergy contributions is positive, then we know that the enthalpy balance ("heat flow") is zero (meaning that all net energy received from the solar collector assembly is either sent to duty or lost in the concentrated "enthalpy loss" mentioned above).

[0276] Such exergy imbalance, in the case of SCA only, contributes to exergy destruction (related to irreversible heat quality loss, i.e., when two fluids of different temperatures are mixed, the enthalpy is the same before and after mixing, but exergy is lost instead) in addition to exergy loss (related to heat loss).

[0277] This example is applied to the pyrolysis of mixed plastic waste as follows: Essential plastic material (mixed plastic waste) is fed into a screw heater and its temperature is brought to approximately 290°C. The jacket of the screw heater is heated by an organic heat transfer fluid (Marlotherm SH) heated by a high-temperature oil exchanger. The heated essential plastic material from the extruder is fed into a first pyrolysis reactor heated with molten salt at "warm" temperature, where it is pyrolyzed to form a gas phase and a semi-solid phase (char). The reactor is a substantially vertical cylinder equipped with an anchor agitator. The gaseous effluent from the first pyrolysis reactor is fed to a second pyrolysis reactor, which is essentially a tubular heat exchanger, optionally filled with a catalyst, where the pyrolysis vapors are heated and further pyrolyzed into smaller molecules. The gaseous effluent from the second pyrolysis reactor is fed to a condensation section to obtain at least one liquid stream containing a large proportion of hydrocarbons, quantitatively exceeding 10 wt. % of the initial weight of the fed plastic material. The char from the first pyrolysis reactor is sent to a coker heated with high-temperature molten salt. This produces a solid material with a better HSE profile (health, safety, and environment) and useful as an energy source as well as a filler. The gases generated in this process are conveyed to the condensation section to increase the pyrolysis yield.

[0278] Comparative Example 2 This is a single-fluid driven solar pyrolysis process (single heat transfer fluid loop).

[0279] The process corresponding to this example is shown in FIG.

[0280] The heat transfer fluid was the same solar mixture of molten salts ("solar salt") as in Example 1, and the physical property correlations were the same.

[0281] The solar collector assembly (62) is of the same type as in the first embodiment.

[0282] The code used to calculate the performance of the solar receiver is the same as the code used in Example 1, and the values ​​of the geometric, optical, and physical constants and ambient conditions are also the same.

[0283] The duty of the molten salt, the heat flow rate (watts), and the inlet and outlet temperatures of the molten salt were all the same as in Example 1.

[0284] Under this constraint, the required mass flow rate of the molten salt through the solar receiver (63) is 42.6 kg / s. The inlet temperature of the solar salt is 418°C and the outlet temperature is 565°C.

[0285] The high-temperature receiver (64) receives the solar salt leaving the SCA (62). The hot solar salt from the high-temperature reservoir is sent in parallel to the units requiring the highest operating temperatures (e.g., the coker 76 and the secondary pyrolysis reactor 71) and the first pyrolysis reactor (70). In fact, the first pyrolysis reactor requires a larger heat flow rate at a lower temperature. Therefore, the setup shown in Figure 9 and detailed here is specifically designed to maximize the effectiveness in such a configuration: after passing through the coker and the secondary pyrolysis reactor, the solar salt is at a high enough temperature to heat the first pyrolysis reactor, but its volume is insufficient to provide the required (large) heat. Therefore, an additional flow of solar salt is fed directly from the high-temperature reservoir to the first reactor.

[0286] Heating of both the first pyrolysis reactor (70) and the second pyrolysis reactor (71) is achieved by weir devices (78) and (79), which are identical to those used in Example 1.

[0287] A portion of the solar salt leaving the first pyrolysis reactor is sent to a high-temperature oil exchanger (81), which, like in Example 1, is a heat exchanger that heats an organic heat transfer fluid with the "low-temperature" molten salt from the first pyrolysis reactor.

[0288] Since the required duty is much smaller than the duty of the first pyrolysis reactor, only a portion of the molten salt leaving the first pyrolysis reactor is sent to the high temperature oil exchanger.

[0289] The solar salt leaving the first pyrolysis reactor is collected in a low temperature molten salt reservoir (63), closing the (single) molten salt loop.

[0290] As in Example 1, the heat losses in the molten salt circuit, including the coker, second pyrolysis reactor, and associated connecting piping, are lumped into a single heat loss (83) designated "Enthalpy Loss 2." The heat losses in the molten salt circuit, including the first pyrolysis reactor, the hot oil exchanger, and associated connecting piping, are lumped into a second single heat loss (82) designated "Enthalpy Loss 1."

[0291] An exergy balance is performed as well.

[0292] The table below shows the detailed calculation results and the calculation results of the total heat flow and total exergy flow obtained by adding up the contributions of all the units.

[0293] [Table 3]

[0294] It can be seen that the enthalpy balance ("heat flow") is zero (as in Example 1), while the sum of all exergy contributions is positive.

[0295] Comparison between Example 1 and Comparative Example 2 The following table compares the duties of Example 1 and Comparative Example 2:

[0296] [Table 4]

[0297] In both cases, all duties are the same, both in terms of heat flow and exergy flow, the latter being the same to ensure the same temperature difference for the internal circulation pumps despite the different inlet temperatures at the weirs (T1 and T2 are the same in both Example 1 and Comparative Example 2).

[0298] As a result, it can be said that there is no difference in the pyrolysis process, since both Example 1 and Comparative Example 2 perform the same duty at the same temperature relative to the load. However, the exergy balance is different: in fact, Example 1 has an imbalance of 14,918 kW, while Comparative Example 2 has an imbalance of 16,570 kW, which is about 11% more.

[0299] That is, Comparative Example 2 requires the same amount of energy but at a higher quality level (more energy at higher temperatures) and is therefore less efficient.

[0300] The reason is that when two streams of different temperatures are mixed, energy is conserved but exergy is not: in fact, in such an operation, the hotter (i.e., higher quality) stream is irreversibly destroyed.

[0301] Finally, the efficiency of the process of Example 1 allows for lower land and plant installation and operating cost requirements, as shown in the table below:

[0302] [Table 5]

[0303] By splitting the solar salt charger (solar collector assembly, SCA) into two independent units, it is possible to generate a "hot energy" flow of high-temperature but low-volume molten salt, and a "warm energy" flow of low-temperature but high-volume molten salt. Solar collectors are more effective when used to heat low-temperature heat transfer fluids, where heat loss is very low, because evacuated tubes can strongly reduce thermal conductivity, but radiative emission is not limited. This does not take into account that radiative emission increases as the fourth power of temperature, and that the emissivity of the cermet material (used to limit emissivity) applied to the receiver tube increases significantly above 500°C.

[0304] The pyrolysis process of mixed plastic waste to produce a pyrolysis condensate containing hydrocarbons requires a relatively low temperature but high duty first pyrolysis reactor (and optional preheater) plus a high temperature but low duty second pyrolysis reactor (and optional coker). Thus, efficiency can be optimized by matching a high temperature, low volume molten salt stream to the second pyrolysis reactor and a low temperature, high volume molten salt stream to the first pyrolysis reactor.

[0305] As a result, the total number of solar receivers in the embodiment using the dual molten salt circuit of the present invention is 980. Conversely, the number of solar receivers with the same duty using one single loop of molten salt is 1050, which is about 7% more. This means not only higher installation and operation costs, but also (obviously) a larger footprint.

Claims

1. 1. A process for producing at least pyrolysis oil from essential plastic material, said process comprising the steps of: a) heating a first heat transfer fluid (F1) by solar radiation to a temperature (T1) between 400°C and 520°C; b) heating the second heat transfer fluid (F2) by solar radiation to a temperature (T2) higher than the temperature (T1); c) heating the first pyrolysis reactor (R1) with the heated first heat transfer fluid (F1); d) heating the second pyrolysis reactor (R2) with the heated second heat transfer fluid (F2); e) feeding at least essential plastic material (M1) into said first pyrolysis reactor (R1); f) maintaining the essential plastics material (M1) in the first pyrolysis reactor for a residence time of at least 2 minutes, in any case sufficient to produce a gaseous fluid (M2) containing hydrocarbons; g) feeding the fluid (M2) in a gaseous state containing hydrocarbons produced in the first pyrolysis reactor (R1) into a second pyrolysis reactor (R2); h) maintaining said fluid (M2) in gaseous state in said second pyrolysis reactor (R2) for a residence time of at least 10 seconds; i) condensing, in whole or in part, the gases leaving the second pyrolysis reactor (R2) so as to form at least a liquid comprising hydrocarbons having a normal boiling point not lower than 25°C; and a process including.

2. 2. The process for producing at least pyrolysis oil from essential plastic material according to claim 1, wherein the first and second heat transfer fluids (F1, F2) are substantially completely recycled.

3. 3. A process for producing at least pyrolysis oil from essential plastic materials as described in claim 2, wherein the recirculation of the first heat transfer fluid (F1) forms a first heat transfer fluid loop ("warm loop") and the recirculation of the second heat transfer fluid (F2) forms a second heat transfer fluid loop ("hot loop").

4. 4. The process for producing at least pyrolysis oil from essential plastic material as described in claim 3, wherein the first heat transfer fluid loop includes the steps a) and c), and the second heat transfer fluid loop includes the steps b) and d).

5. Additionally, the following steps: j) storing said first heat transfer fluid (F1) from step c) in a reservoir ("cold reservoir") prior to use in step a); k) storing the second heat transfer fluid (F2) heated in step b) in a reservoir ("hot reservoir") before use in step d). A process for producing at least pyrolysis oil from essential plastic material according to any one of claims 1 to 4, comprising:

6. 6. A process for producing at least pyrolysis oil from essential plastic material according to any one of claims 1 to 5, wherein the first heat transfer fluid (F1) is compositionally identical to the second heat transfer fluid (F2).

7. Additionally, the following steps: l) storing in a reservoir ("warm reservoir") the first heat transfer fluid (F1) heated in step a) before use in step c) and the second heat transfer fluid (F2) cooled in step d) before use in step b); 7. A process for producing at least pyrolysis oil from the essential plastic material of claim 6, comprising:

8. Additionally, the following steps: m) storing the first heat transfer fluid (F1) heated in step a) in a reservoir ("warm reservoir A") prior to use in step c); n) storing the second heat transfer fluid (F2) cooled in step d) in a reservoir ("warm reservoir B") prior to use in step b). A process for producing at least pyrolysis oil from the essential plastic material according to any one of claims 1 to 6, comprising:

9. Additionally, the following steps: p) heating the essential plastic material with the heated first heat transfer fluid (F1) before step e). A process for producing at least pyrolysis oil from the essential plastic material according to any one of claims 1 to 8, comprising:

10. Additionally, the following steps: o) heating the liquid, solid or semi-solid residue (char) of the pyrolysis of step f) with the heated second heat transfer fluid (F2), and optionally also with a gas heater, electrical resistance (Joule effect), and combinations thereof; A process for producing at least pyrolysis oil from the essential plastic material according to any one of claims 1 to 9, comprising:

11. 10. The process according to claim 9, wherein in step p) the essentially plastics material is brought to a temperature of 120 to 430°C, preferably 150 to 320°C, even more preferably 180 to 220°C, and the average residence time in step p) is preferably less than 20 minutes, more preferably less than 4 minutes, in particular less than 1 minute.

12. 11. The process according to claim 10, wherein in step o) the char is heated to a temperature of from 500°C to 1200°C, preferably from 600°C to 1000°C, more preferably from 700°C to 900°C, for a time of at least 5 minutes, preferably from 15 to 180 minutes, more preferably from 30 to 120 minutes.

13. 13. The process according to any one of claims 1 to 12, wherein the first and second heat transfer fluids (F1, F2) are molten salts, preferably having a melting temperature of at most 340°C, more preferably at most 270°C, even more preferably at most 240°C.

14. 14. The process of claim 13, wherein the molten salt is a molten salt of Group IA and Group IIA of the periodic table, preferably sodium nitrate, sodium nitrite, potassium nitrite, potassium nitrate, lithium nitrate, calcium nitrate, or mixtures thereof.

15. 14. The process according to claim 13, wherein the molten salt is a nitrate / nitrite mixture, in particular a mixture of potassium nitrate and sodium nitrate, preferably "solar salt", optionally with the addition of sodium nitrite and calcium nitrate.

16. 9. The process of claim 8, wherein the first heat transfer fluid (F1) is compositionally different from the second heat transfer fluid (F2).

17. 17. The process according to claim 16, wherein the first heat transfer fluid (F1) has a lower melting point than the second heat transfer fluid (F2), preferably the first heat transfer fluid (F1) has a melting point of at most 180°C, more preferably at most 150°C.

18. 18. The process according to any one of claims 1 to 17, wherein the temperature difference between the temperature T2 of step b) and the temperature T1 of step a) is at least 10°C, more preferably between 30°C and 300°C, even more preferably between 60°C and 250°C.

19. The process of any one of claims 1 to 18, wherein the heating of steps a) and b) is performed by at least one solar collector assembly comprising a parabolic trough, a linear Fresnel, or a combination thereof.

20. 20. The process of claim 19, wherein the concentration of the at least one solar collector assembly in step b) is higher than the concentration of the at least one solar collector assembly in step a).

21. 21. The process according to any one of claims 1 to 20, wherein the temperature reached by the essential plastics material in the first pyrolysis reactor (70) is between 330°C and 580°C, preferably between 340°C and 540°C, more preferably between 360°C and 500°C, even more preferably between 380°C and 480°C, even more preferably between 410°C and 450°C, and wherein the temperature difference between the second pyrolysis reactor (71) and the first pyrolysis reactor (70) is at least 10°C, preferably between 30°C and 300°C, more preferably between 60°C and 250°C, with the additional condition that the temperature is between 400°C and 650°C, preferably between 440°C and 550°C, more preferably between 460°C and 530°C.

22. 1. A plant for producing at least pyrolysis oil from essential plastic material, said plant comprising: A) a first pyrolysis reactor (70) having at least one inlet through which essential plastic material is fed, an outlet through which at least one gaseous effluent is removed, and a jacket and / or coil provided with at least one inlet and one outlet for a heat transfer fluid; B) a second pyrolysis reactor (71) having at least one inlet to which at least one gas stream from said first pyrolysis reactor (70) is fed, an outlet through which at least one gaseous effluent is removed, and a jacket and / or coil provided with at least one inlet and one outlet for a heat transfer fluid; C) a first solar collector assembly (61) including a first solar receiver, preferably a tube receiver, said first solar receiver including at least one inlet and one outlet for said heat transfer fluid, said solar collector assembly being configured to provide concentrated solar radiation to said first solar receiver, thereby heating said heat transfer fluid; and D) a second solar collector assembly (62) including a second solar receiver, preferably a tube receiver, said second solar receiver including at least one inlet and one outlet for said heat transfer fluid, said solar collector assembly being configured to provide concentrated solar radiation to said second solar receiver, thereby heating said heat transfer fluid; E) a first tank (63, "cold reservoir") in which the heat transfer fluid at low temperature is collected, the first tank (63) being fluidly connected to receive the heat transfer fluid from the first pyrolysis reactor (70) and deliver the heat transfer fluid to the first solar collector assembly (61); F) a second tank (64, "warm reservoir") in which the heat transfer fluid at a medium temperature is collected, the second tank (64) being fluidly connected to receive the heat transfer fluid from the first solar collector assembly (61) and to deliver the heat transfer fluid to the first pyrolysis reactor (70); G) a third tank (65, "hot reservoir") in which the heat transfer fluid at high temperature is collected, the third tank (65) being fluidly connected to receive the heat transfer fluid from the second solar collector assembly (62) and to deliver the heat transfer fluid to the second pyrolysis reactor (71); H) a condenser (72) comprising at least one inlet for said gas stream containing hydrocarbons and one outlet for a condensate capable of at least partially condensing said gas stream containing hydrocarbons; Including, The first solar collector (61) is fluidly connected to the first tank (63) at one end of the first solar receiver and to the second tank (64) at the other end of the first solar receiver; the second solar collector (62) is fluidly connected to the second tank (64) at one end of the second solar receiver and to the third tank (65) at the other end of the second solar receiver; and the condenser (72) is fluidly connected to the second pyrolysis reactor (71) so as to be able to partially condense pyrolysis vapors produced by the first pyrolysis reactor and the second pyrolysis reactor.

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