Process and installation for converting plastics into pyrolytic oils

Abstract

A process for converting plastics into pyrolytic oils, in which: - the plastics are continuously fed into a preheating reactor (3) to be mixed and preheated to a preheating temperature to obtain a paste-like mixture; - the paste-like mixture is continuously transferred to a pyrolysis reactor (5) to be heated to a pyrolysis temperature, under an anaerobic or inert atmosphere, to be converted into synthesis gases and a solid reaction product; - the synthesis gases, containing condensable and non-condensable gases, are collected at a first outlet (51) located above the permeable bed, and the solid reaction product is collected at a second outlet (52) located below the permeable bed; - the condensable gases from the synthesis gases are condensed into pyrolytic oils, which are then recovered. Abstract figure: Figure 1

Description

Title of the invention: Process and installation for converting plastics into pyrolytic oils technical field

[0001] The invention relates to a conversion process implementing pyrolytic degradation of plastics for conversion into pyrolytic oils, as well as to an associated conversion installation.

[0002] It relates more particularly to a process using catalytic and / or thermal pyrolysis for the chemical recycling of plastics, making it possible to produce pyrolytic oils by condensation of the synthesis gases obtained during the catalytic and / or thermal pyrolysis reaction.

[0003] The invention thus finds a favorite, and not limiting, application for the recycling of plastic materials, and in particular of plastic waste materials, in order to produce pyrolytic oils which will make it possible to produce plastic, thus placing the invention in a sector known as "Plastic to Plastic", in other words in a circular economy of plastics. Previous technique

[0004] It is well known that various processes exist, such as gasification, pyrolysis, solvolysis, and depolymerization, for degrading plastics to obtain chemicals with lower molar masses, such as pyrolytic oils. Pyrolysis consists of the degradation, or cracking, of polymer molecules subjected to a high temperature (generally between 300 and 900°C) to obtain smaller molecules, in the absence of oxygen, with a catalyst (so-called catalytic pyrolysis) or without a catalyst (so-called thermal pyrolysis).

[0005] However, there is a need to carry out catalytic and / or thermal pyrolysis for the production of pyrolytic oils on an industrial and continuous scale, without transient regime likely to harm the quality of the pyrolytic oils. Summary of the invention

[0006] Also, an object of the invention is to propose a process and a conversion installation which allow continuous operation for the production of qualitative pyrolytic oils from a heterogeneous quality of plastic materials.

[0007] To this end, the invention proposes a conversion process implementing pyrolytic degradation of plastics for conversion into pyrolytic oils, this conversion process comprising at least the following phases: - The plastic materials are continuously fed into a preheating reactor in order to be mixed and preheated to a preheating temperature for the to thin and obtain a pasty mixture; - the pasty mixture is continuously transferred into a pyrolysis reactor to be heated to a pyrolysis temperature, higher than the preheating temperature, under an anaerobic or inert atmosphere in order to be converted into synthesis gases and a solid reaction product containing at least chars, the pasty mixture descending by gravity inside the pyrolysis reactor and through a permeable bed which is heated to the pyrolysis temperature; - the synthesis gases, containing condensable and non-condensable gases, are recovered on a first outlet of the pyrolysis reactor located above the permeable bed, and the solid reaction product is recovered on a second outlet of the pyrolysis reactor located below the permeable bed; - the condensable gases from the synthesis gases are condensed into pyrolytic oils which are recovered.

[0008] Thus, the invention proposes to preheat the plastics to the preheating temperature and then to heat and crack the liquefied plastics to the continuous pyrolysis temperature.

[0009] Preheating in the preheating reactor provides two particularly advantageous functions: the first function is to transmit a significant amount of energy to the plastics to change their physical state and become a paste-like state before the pyrolysis reactor, thus promoting the chemical cracking reaction; and the second function is to fluidize and homogenize the plastics (with the change of physical state between initially solid plastics, which will be fluidized in the preheating reactor), which will then come into contact with the permeable bed presenting a large heat exchange surface with the plastics falling (or flowing) by gravity through this permeable bed.Introducing plastics in a homogeneous manner into the pyrolysis reactor optimizes contact with the heated permeable bed, which provides the energy capacity to trigger the cracking reaction of plastics into syngas (also called "syngas").

[0010] It should be noted that the pyrolysis reaction occurs in an anaerobic atmosphere (in the absence of oxygen) or under an inert atmosphere, with a fixed and stable pyrolysis temperature. This pyrolysis reaction takes place during the simultaneous contact of the liquefied plastics, possibly mixed with a catalyst, and the heated permeable bed within the pyrolysis reactor, resulting in the chemical cracking reaction and thus the depolymerization of the plastics. The use of a pyrolysis reactor in the form of a gravity column into which the plastics fall significantly increases the contact time between the incoming plastics and the heated permeable bed.

[0011] This process allows for the separation of energy inputs for activating plastics, between the energy input in the preheating reactor and the energy input in the pyrolysis reactor, in order to optimize the cracking reaction of the plastics. Indeed, this separation of energy inputs makes it possible to segment the operating temperatures according to the reactor in question and to operate within a constant and stable temperature range in the pyrolysis reactor, thus obtaining selective cutting of the carbon chains present in the pyrolytic oils.

[0012] Thus, the process makes it possible to have: - an initial input of activation energy, in the preheating reactor, over a temperature range between 20 and 290°C, amounting to 40 to 70% of the total energy required to carry out the pyrolysis reaction; and - a second input of activation energy, in the pyrolysis reactor, over a temperature range between 300 and 900°C, amounting to 30 to 60% of the energy required to trigger the pyrolysis reaction.

[0013] Thus, a large amount of the activation energy required for the pyrolysis reaction is supplied to the preheating reactor, so the pyrolysis reactor has to supply less energy to crack the plastics.

[0014] Furthermore, the synthesis gases (also called "syngas"), produced during the thermal and / or catalytic cracking of plastics, are extracted at the first outlet, above the permeable bed, to promote the settling of the chars within the pyrolysis reactor and prevent their transfer to the syngas recovery line. This extraction of the syngases above the permeable bed is also necessary in the event of a partial cracking reaction due to the possibility of different energy inputs between the bottom and top of the pyrolysis reactor (for example, due to heterogeneity in the different types of plastics). This gas extraction also helps to limit, or even prevent, clogging of the syngas recovery line.

[0015] According to one characteristic, the plastics are in the form of granules or flakes with dimensions of a maximum of 15 to 25 millimeters.

[0016] Advantageously, a degassing step of the pasty mixture is implemented inside the preheating reactor.

[0017] This degassing step consists of degassing, in other words, extracting the gases dissolved and / or contained within the plastics being liquefied, and in particular the air contained within the plastics upstream of the preheating reactor and the air incorporated within the plastics inside the preheating reactor during their liquefaction. The aim is to avoid, or at least reduce, the introduction of air into the pyrolysis reactor.

[0018] This degassing step can be carried out by an air pump, such as a vacuum pump, in connection with the preheating reactor.

[0019] According to one possibility of the process, before being introduced into the preheating reactor, the plastics are dry-washed inside an inlet centrifuge, with air heated to a drying temperature lower than the preheating temperature.

[0020] The advantages of this dry washing process using centrifugation and hot air are to eliminate moisture present in the plastics and to extract contaminants accompanying them, such as cellulosic waste, inert waste, and metal fragments. This step thus reduces the impact of these contaminants on the quality of pyrolytic oils.

[0021] According to another possibility of the process, before being introduced into the preheating reactor, the plastics are introduced into a cyclone (for example by means of an air system) having a base provided with an exhaust outlet connected to the preheating reactor.

[0022] Such a cyclone has a dual function: the first function is to extract the air trapped in the plastics upstream of the preheating reactor, and the second function is to convey the plastics into the preheating reactor. Furthermore, a bed of plastic granules or flakes forms at the base of the cyclone, creating a plug at its outlet and thus preventing air from entering the preheating reactor.

[0023] According to another possibility, inside the preheating reactor, the plastics are mixed by means of a screw conveyor.

[0024] Such a screw is advantageous for homogenizing heated plastic materials within the paste mixture.

[0025] According to one feature, the preheating temperature is between 20 and 290 °C inside the preheating reactor.

[0026] In a particular embodiment, inside the preheating reactor, the plastics are preheated by means of a heat transfer fluid present or circulating in a double jacket of the preheating reactor.

[0027] Advantageously, the heat transfer fluid of the preheating reactor is heated by a burner supplied at least partially by the non-condensable gases of the synthesis gases recovered on the first outlet of the pyrolysis reactor.

[0028] Thus, these non-condensable gases, products of pyrolysis, are used directly in the process, thereby offering energy savings.

[0029] In a particular embodiment, between the preheating reactor and the pyrolysis reactor, the pasty mixture passes through a material diffuser heated to a diffusion temperature higher than the preheating temperature.

[0030] Where applicable, this diffusion temperature is lower than the activation temperature of the catalyst.

[0031] Such a material diffuser makes it possible to achieve a homogeneous and uniform surface distribution of the paste mixture on the permeable bed in the pyrolysis reactor, in order to take full advantage of the energy capacity of the surfaces offered by the permeable bed. This uniform diffusion of the incoming paste material prevents a preferential flow path and promotes the residence time of the plastics in contact with the heated permeable bed, thus improving heat transfer during the pyrolysis reaction.

[0032] According to one variant, the diffuser and the pyrolysis reactor are connected by a high-temperature sleeve, in order to manage expansions related to temperature differences and promote sealing between the diffuser and the pyrolysis reactor.

[0033] According to one possibility, the permeable bed is subjected to vibration.

[0034] Such vibration promotes the detachment of the tanks, and possibly of the catalyst, present on the permeable bed, and therefore their evacuation downwards by gravity descent within the pyrolysis reactor.

[0035] According to another possibility, the permeable bed is a fixed bed.

[0036] According to one feature, the permeable bed is formed of a lattice composed of meshes delimiting holes, for example made of refractory steel or ceramic.

[0037] In an advantageous embodiment, the permeable bed is heated by means of a heat transfer fluid present or circulating inside the tubular meshes.

[0038] Advantageously, the heat transfer fluid of the permeable bed is heated by a burner supplied at least partially by the non-condensable gases of the synthesis gases recovered on the first outlet of the pyrolysis reactor; which contributes to a relative or at least partial energy autonomy of the process.

[0039] Alternatively or in addition, the pyrolysis reactor is heated to the pyrolysis temperature by means of a heat transfer fluid present or circulating in a double jacket, this heat transfer fluid being heated by a burner supplied at least partially by the non-condensable gases of the synthesis gases recovered on the first outlet of the pyrolysis reactor.

[0040] According to one variant, the permeable bed consists of heat-carrying media, for example made of refractory steel or ceramic.

[0041] Advantageously, the pyrolysis reactor is a narrow and long reaction column (height at least ten times greater than its width or diameter) allowing a significant residence time of the plastics, and where applicable the catalyst, on the permeable bed in order to obtain an optimal pyrolysis reaction. The choice of a reaction column makes it possible to manage the flow of the material within the pyrolysis reactor to encounter a large exchange surface with the permeable bed and ensure a A homogeneous partition, in terms of height and linear distribution, is used to avoid an "arching effect". The use of a reaction column in which the plastics descend by gravity over a significant height considerably increases the contact time between the plastics and the permeable bed.

[0042] According to one characteristic, the pyrolysis temperature is between 300 and 900 °C.

[0043] Pyrolysis is thus presented as a continuous pyrolysis at a constant working temperature (called pyrolysis temperature) over a given range allowing the cracking of plastics while obtaining a constant quality of pyrolytic oils; the pyrolysis reactor allowing to work at a constant pyrolysis temperature in order to avoid a temperature gradient within the pyrolysis reactor and, where appropriate, to manage the working range of the catalyst.

[0044] According to one variant, pyrolysis is a "flash" pyrolysis transforming plastics into synthesis gas in a duration of less than 1 second, or even on the order of 0.01 seconds.

[0045] In a particular embodiment, the plastics are mixed with a catalyst inside the preheating reactor, the preheating temperature being lower than an activation temperature of the catalyst and the pyrolysis temperature being higher than the activation temperature of the catalyst.

[0046] Thus the pasty mixture, at the outlet of the preheating reactor, is a miscible and homogeneous mixture of plastics and catalyst, and the solid reaction product obtained in the pyrolysis reactor contains chars but also catalyst; the mixture of plastics and catalyst being made miscible thanks to preheating in the preheating reactor.

[0047] The activation temperature of the catalyst corresponds to the temperature from which the catalyst is activated and chemically promotes the pyrolysis reaction.

[0048] The catalyst, for example a zeolite, reduces the operating temperatures in the pyrolysis reactor and the activation energies required to initiate the pyrolysis or cracking reaction without altering the shape of the reaction products. Simultaneous thermal and catalytic effects occur when the catalyst, mixed with the plastics, is introduced directly into the pyrolysis reactor. The catalyst thus optimizes the overall yield to favor the valuable oil fractions. The catalyst also enables selectivity of the reaction products and the breaking of carbon chains to obtain the desired oil quality and properties.

[0049] Advantageously, the solid reaction product, recovered from the second outlet of the pyrolysis reactor, is introduced into a closed regeneration reactor for heating the solid reaction product to a regeneration temperature allowing at least partial regeneration of the catalyst it contains.

[0050] According to one feature, inside the closed regeneration reactor, the solid reaction product is heated by means of a heat transfer fluid present or circulating in a double jacket of the closed regeneration reactor.

[0051] According to another feature, the heat transfer fluid of the closed regeneration reactor is heated by a burner supplied at least partially by the non-condensable gases of the synthesis gases recovered on the first outlet of the pyrolysis reactor; which also contributes to a relative or at least partial energy autonomy of the process.

[0052] According to one possibility, the regeneration temperature is between 300 and 900 °C.

[0053] According to another possibility, at the outlet of the closed regeneration reactor, the solid reaction product is introduced into a separator to carry out a separation between regenerated catalyst and chars or a mixture containing chars and non-regenerated catalyst, the regenerated catalyst being reintroduced inside the preheating reactor.

[0054] Thus, the catalyst is at least partially regenerated in the closed regeneration reactor, and recovered at the outlet of the separator to be recycled as it is reinjected into the preheating reactor in order to be mixed with the plastics.

[0055] According to another possibility, before its introduction into the preheating reactor, the regenerated catalyst is mixed with a new catalyst.

[0056] According to another possibility, the new catalyst is mixed with the regenerated catalyst in a predefined and controlled proportion using a metering screw.

[0057] In a particular embodiment, the synthesis gases, recovered on the first outlet of the pyrolysis reactor, are introduced into a filtration unit for filtration of suspended particles contained in the synthesis gases, before condensation of the condensable gases of the synthesis gases.

[0058] This advantageous filtration unit thus forms a purification section on the synthesis gas recovery line, in order to separate any impurities from the synthesis gas in order to avoid contamination of the reaction products and also, where appropriate, disruption of the effects of the catalyst.

[0059] According to one possibility, the synthesis gases are subjected to cyclonic filtration within at least one cyclone of the filtration unit.

[0060] The cyclonic function is advantageous for separating dust and suspended char particles from synthesis gases, in order to eliminate volatile dust and chars with the aim of avoiding potential contamination of pyrolytic oils.

[0061] According to another possibility, the synthesis gases are subjected alternately to cyclonic filtration within a first cyclone of the filtration unit and to a cyclonic filtration within a second cyclone of the filtration unit, at least one cyclone of the filtration unit comprising said first cyclone and said second cyclone in parallel.

[0062] Since the plastic pyrolysis process is continuous, it is advantageous to have these two cyclones which are interchangeable and which operate alternately in order to facilitate maintenance and cleaning cycles; in other words, when one of the cyclones is being cleaned, the other is active in purification mode.

[0063] In an advantageous embodiment, after cyclonic filtration, the synthesis gases are subjected to micrometric filtration within at least one micrometric filter of the filtration unit.

[0064] Such micrometric filtration allows for finer filtration of the remaining particles and contaminants in the synthesis gas, compared to cyclone(s). In other words, this micrometric filtration aims to eliminate microparticles not purified by the previous cycloning step.

[0065] According to one possibility, the synthesis gases are subjected alternately to micrometric filtration within a first micrometric filter of the filtration unit and to micrometric filtration within a second micrometric filter of the filtration unit, at least one micrometric filter of the filtration unit comprising said first micrometric filter and said second micrometric filter in parallel.

[0066] Since the plastic pyrolysis process is continuous, it is advantageous to have these two micrometric filters which are interchangeable and which operate alternately in order to facilitate maintenance and cleaning cycles; in other words, when one of the micrometric filters is being cleaned, the other is active in filtration mode.

[0067] According to a particular embodiment, the condensable gases of the synthesis gases are condensed successively in at least one primary condenser operating at a primary condensation temperature, then in at least one secondary condenser operating at a secondary condensation temperature, said secondary condensation temperature being lower than the primary condensation temperature.

[0068] After the synthesis gas recovery line, and where applicable after filtration, these synthesis gases undergo condensation, preferably during a flash operation that allows the synthesis gases to be cooled at the outlet of the pyrolysis reactor; these synthesis gases comprise non-condensable gases (such as carbon monoxide CO, carbon dioxide CO2, methane CH4) and condensable hydrocarbon gases. These synthesis gases may also contain impurities (minor inorganic compounds, e.g., metals, alkalis, sulfur, sodium, etc.) initially present in the plastics.

[0069] In operation, the synthesis gas(s) pass through one or more of the primary condensers, which are thus conveyed and cooled in this primary condenser to provide the necessary thermal shock between the hot synthesis gas and the cold primary condenser. This results in condensation of the polymer chains present in the synthesis gas, in the form of pyrolytic oils and a water fraction, which can then be collected in a settling tank.

[0070] The proportions of condensing syngas are controlled by controlling the cooling temperature of the primary condenser, called the primary condensation temperature. Preferably, the syngas recovery line, before the primary condenser, is thermally traced to the inlet of the primary condenser(s) in order to prevent premature condensation of the syngas into pyrolytic oils.

[0071] A fraction of the condensable gases that were not condensed in the primary condenser then passes through the secondary condenser, which operates at a lower temperature, thus resulting in a greater thermal shock than that experienced by the primary condenser. This dual quenching or condensation effect reduces energy consumption for cooling the synthesis gases. The secondary condenser is advantageous because it induces the condensation of the fraction of gases that did not condense after passing through the primary condenser. The shorter chains condense into a new fraction of pyrolytic oils, obtained through condensation in the secondary condenser. If necessary, this fraction is transferred to the settling tank.

[0072] The principle of using two successive condensers at two distinct temperatures makes it possible to condense all (or at least a large part) of the condensable gases into pyrolytic oils, thanks to two different condensation temperatures, and thus makes it possible to maximize the conversion into pyrolytic oils.

[0073] In an advantageous embodiment, before condensation in at least one secondary condenser, the condensable gases of the synthesis gas are condensed alternately in a first primary condenser and in a second primary condenser, the at least one primary condenser comprising said first primary condenser and said second primary condenser in parallel.

[0074] Since the plastic pyrolysis process is continuous, it is advantageous to have these two primary condensers which are interchangeable and which operate alternately in order to facilitate maintenance and cleaning cycles; in other words, when one of the primary condensers is being cleaned, the other is active in condensation mode.

[0075] Advantageously, a vacuum pump, arranged downstream of at least one condenser secondary, provides suction of synthesis gases into at least one secondary condenser and evacuation of non-condensable gases on a non-condensable gas recovery line.

[0076] The invention also relates to a conformal conversion plant for the pyrolytic degradation of plastics for conversion into pyrolytic oils, such a conversion plant comprising at least: - a continuous supply line for plastic materials; - a preheating reactor connected to the continuous supply line for the plastics, said preheating reactor being configured to mix the plastics and preheat them to a preheating temperature in order to fluidize them and obtain a pasty mixture; - a pyrolysis reactor disposed downstream of the preheating reactor and configured to heat the pasty mixture to a pyrolysis temperature, higher than the preheating temperature, under an anaerobic or inert atmosphere in order to be converted into synthesis gases and a solid reaction product containing at least chars, the pyrolysis reactor internally incorporating a permeable bed, a first outlet located above the permeable bed and a second outlet located below the permeable bed; - a synthesis gas recovery line connected to the first outlet of the pyrolysis reactor, the synthesis gas containing condensable and non-condensable gases; - a solid reaction product recovery line connected to the second outlet of the pyrolysis reactor; - a condensation line located downstream of the synthesis gas recovery line and configured to condense the condensable gases from the synthesis gas into pyrolytic oils.

[0077] According to one feature, the continuous plastics feed line includes, upstream of the preheating reactor, an inlet centrifuge for dry washing the plastics, with air heated to a drying temperature lower than the preheating temperature.

[0078] According to another feature, the plastics supply line includes, upstream of the preheating reactor, a cyclone having a base provided with an exhaust outlet connected to the preheating reactor.

[0079] In a particular embodiment, the preheating reactor includes a screw conveyor.

[0080] According to one possibility, the preheating reactor comprises a double jacket in which a heated heat transfer fluid is present or circulates.

[0081] According to another possibility, the preheating reactor is associated with a burner for to heat the heat transfer fluid of the preheating reactor, said burner being supplied at least partially by the non-condensable gases of the synthesis gas recovered on the synthesis gas recovery line.

[0082] In an advantageous embodiment, the installation includes, between the preheating reactor and the pyrolysis reactor, a material diffuser for a substantially homogeneous and uniform surface distribution of the pasty mixture inside the pyrolysis reactor, said material diffuser being heated to a diffusion temperature greater than or equal to the preheating temperature and less than the pyrolysis temperature.

[0083] According to a particular embodiment, the pyrolysis reactor is associated with a vibrator to subject the permeable bed to vibration.

[0084] According to one characteristic, the permeable bed is a fixed bed.

[0085] According to another feature, the permeable bed is formed of a lattice composed of meshes delimiting holes, for example made of refractory steel or ceramic.

[0086] According to a particular embodiment, the meshes of the permeable bed are tubular and a heated heat transfer fluid is present or circulates inside said meshes.

[0087] According to one possibility, the pyrolysis reactor is associated with a burner to heat the heat transfer fluid of the permeable bed and / or to heat a heat transfer fluid circulating or present in a double jacket of the pyrolysis reactor, said burner being supplied at least partially by the non-condensable gases of the synthesis gas recovered on the synthesis gas recovery line.

[0088] In a particular embodiment, the installation includes a catalyst supply line connected to the preheating reactor, said preheating reactor being configured to mix the plastics with the catalyst and preheat them to the preheating temperature which is lower than a catalyst activation temperature, and in which the pyrolysis temperature is higher than the catalyst activation temperature.

[0089] In an advantageous embodiment, the installation includes a closed regeneration reactor connected to the second outlet of the pyrolysis reactor, for heating the solid reaction product to a regeneration temperature allowing at least partial regeneration of the catalyst it contains.

[0090] According to one feature, the closed regeneration reactor comprises a double jacket inside which a heated heat transfer fluid is present or circulates.

[0091] According to another feature, the closed regeneration reactor is associated with a burner to heat the heat transfer fluid of the closed regeneration reactor, said burner being supplied at least partially by the non-condensable gases of the synthesis gas recovered on the synthesis gas recovery line.

[0092] According to another feature, the installation comprises, at the outlet of the regeneration reactor closed generation, a separator for carrying out a separation between regenerated catalyst and chars or a mixture containing chars and non-regenerated catalyst, the separator comprising a first outlet for the regenerated catalyst and a second outlet for the chars or the mixture containing chars and non-regenerated catalyst.

[0093] According to a particular embodiment, the installation includes a return line connecting the first outlet of the separator to the catalyst supply line in order to reintroduce the regenerated catalyst into the preheating reactor.

[0094] In a particular embodiment, the catalyst supply line is connected to a new catalyst storage volume in order to mix the regenerated catalyst and the new catalyst before introduction into the preheating reactor.

[0095] According to one feature, the catalyst supply line includes a metering screw for mixing the new catalyst with the regenerated catalyst in a predefined and controlled proportion.

[0096] According to a particular embodiment, the syngas recovery line includes a filtration unit for filtering suspended particles contained in the syngas, before condensation of the condensable gases of the syngas in the condensation line.

[0097] According to one feature, the filtration unit includes at least one cyclone for subjecting the synthesis gas to cyclonic filtration.

[0098] According to another feature, at least one cyclone of the filtration unit comprises a first cyclone and a second cyclone in parallel to subject the synthesis gases alternately to cyclonic filtration within the first cyclone and to cyclonic filtration within the second cyclone.

[0099] According to another feature, the filtration unit includes, downstream of at least one cyclone, at least one micrometric filter for subjecting the synthesis gas to micrometric filtration.

[0100] According to another feature, the at least one micrometric filter comprises a first micrometric filter and a second micrometric filter in parallel to subject the synthesis gases alternately to micrometric filtration within the first micrometric filter and to micrometric filtration within the second micrometric filter.

[0101] According to one possibility, the condensation line comprises successively at least one primary condenser operating at a primary condensation temperature, and at least one secondary condenser operating at a secondary condensation temperature, said secondary condensation temperature being lower than the primary condensation temperature.

[0102] According to another possibility, the at least one primary condenser comprises a first primary condenser and a second primary condenser in parallel to condense the condensable gases from the synthesis gases alternately in the first primary condenser and in the second primary condenser.

[0103] In an advantageous embodiment, the installation includes a non-condensable gas recovery line on which a vacuum pump is located downstream of at least one secondary condenser, for drawing the synthesis gases into the at least one secondary condenser and for venting the non-condensable gases. Brief description of the drawings

[0104] Other features and advantages of the present invention will become apparent from the following detailed description, of two non-limiting implementation examples, made with reference to the accompanying figures in which:

[0105] [Fig-1] is a schematic view of part of a plastic pyrolysis installation according to the invention, including in particular the plastics supply line, the catalyst supply line, the preheating reactor and the pyrolysis reactor;

[0106] [Fig.2] is a schematic view of another part of the installation of [Fig.1], and in particular of the synthesis gas recovery line and the condensation line;

[0107] [Fig.3] is a schematic view of a variant of the other part of [Fig.2].

[0108] [Detailed description of one or more embodiments of the invention]

[0109] With reference to the Figures, a conversion installation 1 is provided for a pyrolysis degradation of plastics for a conversion of these plastics into pyrolytic oils.

[0110] The conversion installation 1 includes a continuous plastics feed line 2, which conveys the plastics in bulk and which successively includes an inlet centrifuge 20 and a cyclone 21.

[0111] The inlet centrifuge 20 continuously receives plastic materials at its inlet for dry washing raw plastics, which are in the form of granules or flakes with a maximum size of 15 to 25 millimeters. The inlet centrifuge 20 is designed to dry wash the plastics, for the purpose of decontaminating them, with air heated to a given drying temperature, for example, in the range of 40 to 80 °C. This inlet centrifuge 20 has a discharge 24 for the reflux generated by washing the plastics.

[0112] The cyclone 21 is connected to an outlet of the inlet centrifuge 20 to receive the washed (or purified of contaminants) plastic materials as input, and this cyclone 21 has a base (in its lower part) provided with a discharge outlet 22, as well as a The suction inlet at the top is connected to a suction channel 23 to draw air into the cyclone 21. Thus, air is extracted from this cyclone 21, and a plug of plastic material forms at the base of the cyclone 21, creating an airtight seal on the exhaust outlet 22. This cyclone 21 reduces the amount of air trapped in the plastic material.

[0113] The conversion installation 1 also includes a catalyst supply line 4 for a continuous supply of catalyst; the catalyst having a given activation temperature, from which the catalyst is activated to promote the cracking or pyrolysis reaction of the plastics. This catalyst supply line 4 is connected to a storage volume 40 in which fresh catalyst is stored.

[0114] The conversion installation 1 includes a preheating reactor 3 which is continuously supplied with plastics by the continuous feed line 2, and with catalyst by the catalyst feed line 4. The plastics are introduced through a first inlet 30 of the preheating reactor 3, and the catalyst is introduced through a second inlet 37 of the preheating reactor 3. The first inlet 30 and the second inlet 37 can be separate or joined.

[0115] The discharge outlet 22 of the cyclone 21 is connected to the first inlet 30 of the preheating reactor 3. According to an advantageous possibility, the discharge outlet 22 of the cyclone 21 is arranged above the first inlet 30 of the preheating reactor 3 for gravity-fall feeding of the plastics.

[0116] The preheating reactor 3 includes a heating means and a mixing means for preheating the plastics to a preheating temperature in order to make them fluid, and for mixing the plastics with the catalyst in order to obtain a pasty, miscible and homogeneous mixture, on an outlet 31 of the preheating reactor 3.

[0117] The preheating temperature is higher than the plastics' melting temperature in order to effect a phase transition between a solid and a viscous state. The preheating temperature is lower than the catalyst activation temperature, and also lower than the pyrolysis temperature, which corresponds to the plastics' cracking temperature. The preheating temperature is, for example, between 20 and 290 °C inside the preheating reactor 3.

[0118] Advantageously, the preheating reactor 3 includes a screw 32, and the introduction of the plastics and the catalyst takes place at a first end of this screw 32, and the discharge of the pasty mixture takes place at a second end of this screw 32, opposite its first end.

[0119] This preheating reactor 3 is connected to an air pump 33, like a A vacuum pump, which performs a degassing function, extracts air trapped in the plastics upstream of the preheating reactor 3 and during the fluidization process. The air pump 33 can be followed by one or more filters 34, such as a volatile organic compound filter, for filtration and treatment of the gases trapped within the plastics before release into the atmosphere.

[0120] This preheating reactor 3 comprises a double jacket (or sheath) in which a heat transfer fluid heated by a burner 91 is present or circulates; this burner 91 being thus set to heat the heat transfer fluid of the preheating reactor 3 to the preheating temperature.

[0121] The conversion unit 1 includes a material diffuser 35, connected to the outlet 31 of the preheating reactor 3, so that the slurry mixture (comprising, as a reminder, the liquefied plastics mixed with the catalyst) is introduced into the material diffuser 35. The function of this material diffuser 35 is to ensure a substantially homogeneous and uniform surface distribution of the slurry mixture at its outlet 36. The material diffuser 35 can be heated to a diffusion temperature higher than or equal to the preheating temperature and lower than the pyrolysis temperature, in order to maintain the slurry mixture in a viscous state. This diffusion temperature can be between 200 and 300 °C.

[0122] The conversion installation 1 comprises a pyrolysis reactor 5 connected to the outlet 36 of the material diffuser 35; this pyrolysis reactor 5 is therefore located downstream of the preheating reactor 3 and is configured to heat the paste mixture to a pyrolysis temperature, higher than the preheating temperature and the catalyst activation temperature, under an anaerobic or inert atmosphere in order to convert this paste mixture into synthesis gases and a solid reaction product containing at least chars and catalyst. Inside the pyrolysis reactor 5, a continuous anaerobic pyrolysis or cracking reaction of the plastics occurs, promoted by the catalyst.

[0123] The pyrolysis reactor 5 incorporates internally a permeable bed 50, which is a fixed bed. This permeable bed 50 can, for example, be formed of a lattice composed of meshes delimiting holes, or alternatively, be formed of heat transfer media. The meshes of the lattice or the heat transfer media are, for example, made of refractory steel or ceramic.

[0124] The pyrolysis or cracking reaction therefore takes place between the plastics and the catalyst upon contact with the heated permeable bed 50 within the pyrolysis reactor 5, in an anaerobic or inert atmosphere and with a fixed and stable pyrolysis temperature, for example between 300 and 900 °C. This reaction leads to cracking and therefore depolymerization of the plastics.

[0125] The pyrolysis reactor 5 has a first outlet 51 located above the bed A permeable bed 50 is used for the evacuation and recovery of synthesis gases, and a second outlet 52 is located below the permeable bed 50 for the evacuation and recovery of the solid reaction product. The second outlet 52 is, for example, located at the base of the pyrolysis reactor 5, in the lower part of the pyrolysis reactor 5.

[0126] The synthesis gas outlet is therefore made on the first outlet 51 which is above the permeable bed 50 in order to promote the settling of chars within the pyrolysis reactor 5, with the aim of avoiding the transfer of chars towards the first outlet 51 and thus not contaminating the synthesis gas.

[0127] The outlet 36 of the material diffuser 35 is connected to the top of the pyrolysis reactor 5 (in other words, to the upper part of the pyrolysis reactor 5) and this material diffuser 35 provides a substantially homogeneous and uniform surface distribution of the paste mixture inside the pyrolysis reactor 5 and on its permeable bed 50. Advantageously, the connection between the material diffuser 35 and the pyrolysis reactor 5 is made using a high-temperature sleeve, in order to manage the expansions related to the temperature differences between the material diffuser 35 and the pyrolysis reactor 5, and thus preserve the seal.

[0128] The pyrolysis reactor 5 is associated with a burner 92 which is set to heat a heat transfer fluid to the pyrolysis temperature, in order to heat the pyrolysis reactor 5 and its permeable bed 50 to the pyrolysis temperature.

[0129] According to a first possibility, the heat transfer fluid is present or circulates inside a double jacket of the pyrolysis reactor 5.

[0130] According to a second possibility (in addition to or as a variant of the first possibility mentioned above), the heat transfer fluid is present or circulates inside the permeable bed 50, and for example inside the meshes of the permeable bed 50 which are tubular.

[0131] Optionally, this pyrolysis reactor 5 integrates or includes a vibrator to subject the permeable bed 50 to vibration, in order to promote the detachment of the chars and the catalyst from the permeable bed 50, and thus their gravity descent into the pyrolysis reactor 5.

[0132] The conversion installation 1 includes a solid reaction product recovery line 6 connected to the second outlet 52 of the pyrolysis reactor 5 to recover and treat the solid reaction product which, as a reminder, includes at least the chars and the catalyst; the catalyst, having participated in the pyrolysis reaction, is at least partially in a used state, in other words it includes catalyst to be regenerated and, in a smaller proportion, new or unused catalyst.

[0133] This solid reaction product recovery line 6 includes a regeneration reactor 60 connected to the second outlet 52 of the pyrolysis reactor 5, where this regeneration reactor 60 recovers the solid reaction product to heat it to a temperature The regeneration temperature allows for at least partial regeneration of the catalyst it contains. This regeneration reactor 60 therefore functions to regenerate the spent catalyst contained in the solid reaction product exiting the pyrolysis reactor 5, so that it can be reused.

[0134] This regeneration reactor 60 is a closed reactor, also called a "batch" reactor. The regeneration temperature is, for example, between 300 and 900°C to regenerate the catalyst and separate the regenerated catalyst and the chars.

[0135] Since this regeneration reactor 60 is a closed reactor, and the solid reaction product exits continuously from the pyrolysis reactor 5, it is advantageous to employ a buffer device between the second outlet 52 of the pyrolysis reactor 5 and the regeneration reactor 60, such as for example a guillotine bimetallic valve to isolate the continuous work of the pyrolysis reactor 5 and the work cycles of the regeneration reactor 60.

[0136] This regeneration reactor 60 comprises a double jacket in which a heat transfer fluid heated by a burner 93 is present or circulates; this burner 93 being thus set to heat the heat transfer fluid of the regeneration reactor 60 to the regeneration temperature.

[0137] This solid reaction product recovery line 6 comprises, at the outlet of the regeneration reactor 60, a separator 61 for separating the regenerated catalyst from the chars or a mixture containing the chars and the non-regenerated catalyst. This separator 61 comprises a first outlet 62 for recovering the regenerated catalyst, and a second outlet 63 for recovering the chars or the mixture containing the chars and the non-regenerated catalyst.

[0138] It is advantageous to employ another buffer device, this time between the regeneration reactor 60 and the separator 61, such as for example a guillotine bimetallic valve, to isolate the work cycles of the regeneration reactor 60 and the continuous work of the separator 61.

[0139] The conversion installation 1 includes a return line 41 connecting the first outlet 62 of the separator 61 to the catalyst supply line 4 in order to reintroduce the regenerated catalyst into the preheating reactor 3. More specifically, the return line 41 is part of the catalyst supply line 4, and this return line 41 connects the first outlet 62 of the separator 61 to the second inlet 37 of the preheating reactor 3, in order to introduce the regenerated catalyst into the preheating reactor 3.

[0140] Insofar as the catalyst is not fully regenerated in the regeneration reactor 60 and / or is not fully separated and recovered at the outlet of the separator 61, the return line 41 is connected to the storage volume 40 containing new catalyst in order to mix the regenerated catalyst and the new catalyst before introduction into the preheating reactor 3. The catalyst supply line 4 thus includes a metering screw 42 for metering and mixing the new catalyst with the regenerated catalyst in a predefined and controlled proportion.

[0141] The solid reaction product recovery line 6 includes a collector 64, connected to the second outlet 63 of the separator 61 to collect the chars and the unregenerated catalyst, this collector 64 being followed by a conveyor 65, such as an extraction screw 65, to convey the chars and the unregenerated catalyst to a storage space 66. The chars thus collected may possibly be subject to treatment for recovery.

[0142] The conversion installation 1 includes a synthesis gas recovery line 7 connected to the first outlet 51 of the pyrolysis reactor 5, the synthesis gas containing condensable and non-condensable gases. This synthesis gas recovery line 7 is thermally traced to the same temperature as that of the pyrolysis reactor 5, in order to prevent premature condensation of the condensable gases into pyrolytic oils.

[0143] The syngas recovery line includes a filtration unit 70 for filtering suspended particles contained in the syngas, such as char particles or other types of dust.

[0144] In the example of [Fig.2], this filtration unit 70 includes a cyclone 71 for subjecting the synthesis gas to cyclonic filtration, and a micrometric filter, disposed downstream of the cyclone 71, for subjecting the synthesis gas to micrometric filtration; micrometric filtration being a finer filtration of the particles and contaminants remaining in the synthesis gas, compared to cyclonic filtration.

[0145] Furthermore, the cyclone 71 has at its base a particle evacuation outlet, which is connected to a sealing device 74 to prevent air from entering the cyclone 71, and thus prevent the synthesis gases from mixing with air.

[0146] This sealing device 74 can, for example, be in the form of a drawer incorporating two successive valves for operation as a sealing airlock. Such a two-valve drawer comprises an upper valve upstream of the cyclone 71 discharge outlet and a lower valve connected to a particle collection point. The two-valve drawer operates cyclically as follows: - in a first phase, the upper valve is open and the lower valve is closed, to allow the evacuation of particles from the cyclone to the drawer; - in a second phase, the upper valve is closed and the lower valve is opened, to allow the spool to be purged.

[0147] The opening and closing of the drawer valves are controlled by the level of particles present inside the cyclone 71; the drawer purging being carried out in a cyclical manner.

[0148] In the example of [Fig. 3], this filtration unit 70 comprises a first cyclone 71a and a second cyclone 71b in parallel to subject the synthesis gases alternately to cyclonic filtration within the first cyclone 71a and to cyclonic filtration within the second cyclone 71b. A three-way valve 73 is disposed between the first outlet 51 of the pyrolysis reactor 5 and the two cyclones 71a, 71b, in order to direct the synthesis gases alternately towards the first cyclone 71a and towards the second cyclone 71b.

[0149] Furthermore, each of the two cyclones 71a, 71b has at its base a particle evacuation outlet, which is connected to a sealing device 74a, 74b to prevent air from entering, such as for example a two-valve drawer as described above.

[0150] In the example of [Fig. 3], the filtration unit 70 further comprises a first micrometric filter 72a, downstream of the first cyclone 71a, and a second micrometric filter 72b, downstream of the second cyclone 71b, to subject the synthesis gases alternately to micrometric filtration within the first micrometric filter 72a and to micrometric filtration within the second micrometric filter 72b. Another three-way valve 75 is provided downstream of the first micrometric filter 72a and the second micrometric filter 72b.

[0151] The example in [Fig.3] is advantageous in terms of maintenance. Indeed, since the process is continuous, the two cyclones 71a, 71b are interchangeable and operate alternately in order to facilitate maintenance and cleaning cycles; when one of the two cyclones 71a, 71b is being cleaned, the other is active in purification mode.

[0152] Similarly, the two micrometric filters 72a, 72b are interchangeable and operate alternately in order to also facilitate maintenance and cleaning cycles: when one of the two micrometric filters 72a, 72b is being cleaned, the other is active and in filtration mode.

[0153] The conversion installation 1 includes a condensation line 8 disposed downstream of the synthesis gas recovery line 7 and configured to condense the condensable gases from the synthesis gas into pyrolytic oils.

[0154] The condensation line 8 comprises successively at least one primary condenser 81, 81a, 81b operating at a primary condensation temperature, and at least one secondary condenser 82 operating at a secondary condensation temperature, where this secondary condensation temperature is lower than the primary condensation temperature.

[0155] A thermal shock is necessary between the hot synthesis gases and the primary condenser(s) 81, 81a, 81b for the condensation phenomenon to take place. This step of the process results in the condensation of the polymer chains present in the synthesis gas, in the form of pyrolytic oil and a fraction of water. The proportions of condensing gas are controlled by regulating the cooling temperature of the primary condenser(s) 81, 81a, 81b. The condensation line 8 is thermally traced to the inlet of the primary condenser(s) 81, 81a, 81b, in order to prevent premature condensation of the synthesis gas into pyrolytic oil before reaching the primary condenser(s) 81, 81a, 81b.

[0156] In the example of [Fig.2], this condensation line 8 comprises a single primary condenser 81.

[0157] In the example of [Fig.3], this condensation line 8 comprises a first A primary condenser 81a and a second primary condenser 81b are arranged in parallel to condense the condensable gases from the synthesis gases alternately in the first primary condenser 81a and in the second primary condenser 81b. A three-way inlet valve 83 is located upstream of the two primary condensers 81a and 81b to direct the synthesis gases alternately to the first primary condenser 81a and to the second primary condenser 81b. A three-way outlet valve 84 is located downstream of the two primary condensers 81a and 81b.

[0158] Since the process is continuous, the two primary condensers 81a, 81b are interchangeable and operate alternately to facilitate maintenance and cleaning cycles: when one of the two primary condensers 81a, 81b is being cleaned, the other is active and in condensation mode.

[0159] The condensation line 8 includes, between the primary condenser 81 or the primary condensers 81a, 81b and the secondary condenser 82, a settling tank 85 containing the pyrolytic oils and possibly the condensed water, resulting from the condensation in the primary condenser(s) 81, 81a, 81b.

[0160] The secondary condenser 82 is subjected to a lower temperature than the primary condenser(s) 81, 81a, 81b, and therefore this secondary condenser 82 induces a greater thermal shock than that used for the primary condenser(s) 81, 81a, 81b. Thus, this secondary condenser 82 allows condensation of the fraction of gases not condensed after passing through the primary condenser(s) 81, 81a, 81b. The shorter chains therefore condense in the secondary condenser 82 in the form of a new fraction of pyrolytic oil, obtained through the second condensation, and this new fraction of pyrolytic oil also enters the settling tank 85.

[0161] The condensation line 8 includes a vacuum pump 80, located downstream of the secondary condenser 82, to create a vacuum enabling the suction into the secondary condenser 82 of the fraction of synthesis gas not condensed in the primary condenser(s) 81, 81a, 81b. Thus, this fraction undergoes a new Condensation occurs within the secondary condenser 82, as described previously. The vacuum pump 80 therefore ensures a vacuum in the circuit and facilitates the flow of synthesis gases to the secondary condenser 82.

[0162] The condensation line 8 includes, following the settling tank 85, a separator 86 for separating the pyrolytic oil fractions and potentially the condensed water fraction, in order to direct the pyrolytic oils into a homogenization tank 87 and the condensed water fraction to a water recovery tank 88. This separator 86 potentially allows the water fraction contained in the plastics to be isolated during the introduction of the plastics onto the continuous feed line 2.

[0163] The homogenization tank 87 thus gathers the different fractions of pyrolytic oils, arriving from the decantation tank 85, to carry out homogenization of the pyrolytic oils before their storage.

[0164] Advantageously, the vacuum pump 80 is arranged on a non-condensable gas recovery line 9 on which a vacuum pump is arranged downstream of at least one secondary condenser, for evacuation of non-condensable gases.

[0165] As shown in [Fig. 1], this non-condensable gas recovery line 9 is connected to burners 91, 92, 93 to supply the non-condensable gases to these burners 91, 92, 93 and thus supply these burners 91, 92, 93 at least partially with the non-condensable gases from the synthesis gas. In this way, the non-condensable gases from the pyrolysis reaction serve as an energy source to thermally supply the preheating in the preheating reactor 3, the pyrolysis in the pyrolysis reactor 5, and the regeneration in the regeneration reactor 60. It is possible to supplement this gas supply to burners 91, 92, 93 with another gas, such as natural gas or propane.

[0166] It is possible to provide a boiler 90 equipped with a burner 94 also supplied by the non-condensable gases from this non-condensable gas recovery line 9; such a boiler 90 thus allows the combustion of the non-condensable gases and the production of energy for applications external to the conversion installation 1.

[0167] In addition, the burners 91, 92, 93, 94 can be connected to a flue gas recovery line 95, which recovers the flue gases obtained during the combustion of non-condensable gases by the burners 91, 92, 93, 94. This flue gas recovery line 95 is connected to a flue gas treatment unit 96 to treat these flue gases, thereby purifying them of various sources of contaminants before they are released into the atmosphere through a chimney 97. This flue gas treatment thus makes it possible to comply with environmental regulations for flue gas emissions into the atmosphere while also contributing to a circular economy.

[0168] It should be noted that all stages of the conversion process are carried out in an anaerobic atmosphere (in the absence of oxygen). Inerting cycles (with nitrogen or other inert gases) can advantageously be carried out in the various elements of the conversion installation 1, in order to expel all the oxygen present in the plastics and in the catalyst, and to remove the remaining synthesis gases from the conversion installation 1.

Claims

Demands

1. A conversion process implementing pyrolytic degradation of plastics for conversion into pyrolytic oils, said conversion process comprising at least the following steps: - the plastics are continuously fed into a preheating reactor (3) in order to be mixed and preheated to a preheating temperature to make them fluid and the plastics are mixed with a catalyst inside the preheating reactor (3) in order to obtain a paste-like mixture, the preheating temperature being lower than an activation temperature of the catalyst, and a degassing step of the paste-like mixture is carried out inside the preheating reactor (3);- The pasty mixture is continuously transferred into a pyrolysis reactor (5) to be heated to a pyrolysis temperature, higher than the preheating temperature and the activation temperature of the catalyst, under an anaerobic or inert atmosphere in order to be converted into synthesis gases and a solid reaction product containing at least chars, the pasty mixture descending by gravity inside the pyrolysis reactor (5) and through a permeable bed (50) which is heated to the pyrolysis temperature; - the synthesis gases, containing condensable and non-condensable gases, are recovered on a first outlet (51) of the pyrolysis reactor (5) located above the permeable bed (50), and the solid reaction product is recovered on a second outlet (52) of the pyrolysis reactor (5) located below the permeable bed (50); - the condensable gases from the synthesis gases are condensed into pyrolytic oils which are recovered.

2. A conversion method according to claim 1, wherein, before being introduced into the preheating reactor (3), the plastics are dry-washed inside an inlet centrifuge (20), with air heated to a drying temperature lower than the preheating temperature.

3. Conversion method according to claim 1 or 2, wherein, inside the preheating reactor (3), the plastics and the catalyst are mixed by means of a screw (32).

4. A conversion method according to any one of the preceding claims, wherein the preheating temperature is between 20 and 290 °C inside the preheating reactor.

5. A conversion method according to any one of the preceding claims, wherein, between the preheating reactor (3) and the pyrolysis reactor (5), the pasty mixture passes through a material diffuser (35) for a substantially homogeneous and uniform surface distribution of the pasty mixture inside the pyrolysis reactor (5), said material diffuser (35) being heated to a diffusion temperature greater than or equal to the preheating temperature and less than the pyrolysis temperature.

6. A conversion method according to any one of the preceding claims, wherein the permeable bed (50) is subjected to vibration.

7. A conversion method according to any one of the preceding claims, wherein the permeable bed (50) is a fixed bed.

8. A conversion method according to any one of the preceding claims, wherein the permeable bed (50) is formed of a lattice composed of meshes delimiting holes, for example made of refractory steel or ceramic.

9. A conversion method according to any one of the preceding claims, wherein the pyrolysis temperature is stable and between 300 and 900 °C.

10. A conversion process according to any one of the preceding claims, wherein the solid reaction product, recovered on the second outlet (52) of the pyrolysis reactor (5), is introduced into a closed regeneration reactor (60) for heating the solid reaction product to a regeneration temperature allowing at least partial regeneration of the catalyst it contains.

11. A conversion method according to claim 10, wherein, at the outlet of the closed regeneration reactor (60), the solid reaction product is introduced into a separator (61) to effect a separation between regenerated catalyst and chars or a mixture containing chars and non-regenerated catalyst, the regenerated catalyst being reintroduced into the preheating reactor (3).

12. Conversion method according to claim 11, wherein, before its introduction into the preheating reactor (3), the regenerated catalyst is mixed with a new catalyst.

13. A conversion method according to any one of the preceding claims, wherein the synthesis gases, recovered from the first outlet (51) of the pyrolysis reactor (5), are introduced into a unit of filtration (70) for filtration of suspended particles contained in synthesis gas, before condensation of the condensable gases of the synthesis gas.

14. Conversion method according to claim 13, wherein the synthesis gases are subjected to cyclonic filtration within at least one cyclone (71; 71a, 71b) of the filtration unit (70).

15. A conversion method according to claim 14, wherein the synthesis gases are subjected alternately to cyclonic filtration within a first cyclone (71a) of the filtration unit (70) and to cyclonic filtration within a second cyclone (71b) of the filtration unit (70), at least one cyclone of the filtration unit (70) comprising said first cyclone (71a) and said second cyclone (71b) in parallel.

16. A conversion method according to claim 14 or 15, wherein, after cyclonic filtration, the synthesis gases are subjected to micrometric filtration within at least one micrometric filter (72; 72a, 72b) of the filtration unit (70).

17. A conversion method according to claim 16, wherein the synthesis gases are subjected alternately to micrometric filtration within a first micrometric filter (72a) of the filtration unit (70) and to micrometric filtration within a second micrometric filter (72b) of the filtration unit (70), at least one micrometric filter of the filtration unit (70) comprising said first micrometric filter (72a) and said second micrometric filter (72b) in parallel.

18. A conversion process according to any one of the preceding claims, wherein the condensable gases of the synthesis gases are successively condensed in at least one primary condenser (81; 81a, 81b) operating at a primary condensation temperature, and then in at least one secondary condenser (82) operating at a secondary condensation temperature, said secondary condensation temperature being lower than the primary condensation temperature.

19. A conversion method according to claim 18, wherein, prior to condensation in at least one secondary condenser (82), the condensable gases of the synthesis gases are condensed alternately in a first primary condenser (81a) and in a second primary condenser (81b), the at least one primary condenser comprising said first primary condenser (81a) and said second primary condenser (81b) in parallel.

20. A plastic pyrolysis process according to claim 18 or 19, in in which a vacuum pump (80), disposed downstream of at least one secondary condenser (82), provides suction of the synthesis gases into at least one secondary condenser (82) and evacuation of the non-condensable gases onto a non-condensable gas recovery line (9).

21. Conversion plant (1) for the pyrolytic degradation of plastics for conversion into pyrolytic oils, said conversion plant (1) comprising at least: - a continuous supply line for plastics (2); - a catalyst supply line (4); - a preheating reactor (3) connected to the continuous plastics feed line (2) and to the catalyst feed line (4), said preheating reactor (3) being configured to mix the plastics and preheat them to a preheating temperature in order to make them more fluid, and to mix the plastics with the catalyst in order to obtain a paste-like mixture, the preheating temperature being lower than a catalyst activation temperature, degassing of the paste-like mixture being carried out inside the preheating reactor (3); - a pyrolysis reactor (5) disposed downstream of the preheating reactor (3) and shaped to heat the pasty mixture to a pyrolysis temperature, higher than the preheating temperature and the activation temperature of the catalyst, under an anaerobic or inert atmosphere in order to be converted into synthesis gases and a solid reaction product containing at least chars, the pyrolysis reactor internally incorporating a permeable bed (50), a first outlet (51) located above the permeable bed (50) and a second outlet (52) located below the permeable bed (50); - a synthesis gas recovery line (7) connected to the first outlet (51) of the pyrolysis reactor (5), the synthesis gas containing condensable and non-condensable gases; - a solid reaction product recovery line (6) connected to the second outlet (52) of the pyrolysis reactor (5); - a condensation line (8) arranged downstream of the synthesis gas recovery line (7) and shaped to condense the condensable gases of the synthesis gas into pyrolytic oils.

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