Pyrolysis process and installation including automatic char aspiration

Abstract

Pyrolysis process comprising a preheating phase of a reactor vessel (5), followed by a heating phase of the reactor vessel to a set temperature, during which the material to be pyrolyzed is fed into the vessel, followed by a pyrolysis phase. The process includes, after the pyrolysis phase, a final heating phase and then a cooling phase of the vessel to a predetermined temperature above ambient temperature, followed by a phase of removing the char contained in the vessel by suction. Installation for implementing the process. Figure for the abstract: Figure 1

Description

Title of the invention: Pyrolysis method and installation comprising automatic char aspiration technical field

[0001] The invention relates to pyrolysis, in particular but not exclusively for the production of fuel.

[0002] The invention relates in particular to the chemical recycling of polymer materials or biomass by pyrolysis, in particular but not exclusively for the production of fuels. State of the art

[0003] Global plastics production has been steadily increasing, rising from 1.5 million tonnes in 1950 to approximately 390.7 million tonnes in 2021. By 2050, production is expected to quadruple.

[0004] At the end of their life, polymer materials constitute resources that can be transformed into raw materials (reuse, recycling) or into energy (incineration).

[0005] Chemical recycling of polymer materials can be carried out by depolymerization (glycolysis, methanolysis, hydrolysis and aminolysis) or by thermochemical processes such as hydrocracking, gasification, or pyrolysis.

[0006] Pyrolysis refers to the thermal degradation of a long polymer chain into smaller compounds with a lower molar weight, this process occurring in the absence of oxygen and under the effect of heat, and resulting in the formation of three main products: gas, liquid oils and solid residue (chars).

[0007] For a presentation of the general state of conventional pyrolysis techniques, one can refer for example to the document Donohue, Pyrolysis, types, processes, and industrial sources and products, ISBN 978-1-60741-669-2, 2009.

[0008] Pyrolysis treatments can be classified into different categories (Khodier, Automotive shredder residue for clean energy Systems to produce sustainable green energy, March 2019), including:

[0009] - slow pyrolysis treatments, for which the treatment temperature is between 300°C and 700°C, the heating rate being between 0.1 and 1°C per second, and the treatment time being between 600 and 6000 seconds. The mass proportion of the products obtained by conventional pyrolysis in the context of biomass-type input is typically as follows: char 35%, gas 35%, oil 30%;

[0010] - treatments by rapid pyrolysis, the treatment temperature being between between 450°C and 550°C, the heating rate being between 10 and 200°C per second, and the treatment time being between 0.5 and 5 seconds. The mass proportion of the products obtained by rapid pyrolysis, in the context of biomass-type input, is typically as follows: char 20%, gas 30%, oil 50%;

[0011] - flash pyrolysis treatments, the treatment temperature being between 800°C and 1000°C, with a heating rate exceeding 1000°C per second and a processing time of less than 0.5 seconds. The mass proportions of products obtained by flash pyrolysis, using biomass as input, are typically as follows: char 12%, gas 13%, oil 75%. Flash pyrolysis processes commonly employ circulating fluidized bed reactors, rotating cone reactors, entrained flow reactors, or cyclone reactors.

[0012] For a presentation of the state of the art of biomass pyrolysis reactors, one can refer for example to the document Jerzak et al. Comprehensive review of biomass pyrolysis: conventional and advanced technologies, reactor designs, product compositions and yields, and techno-economic analysis, Energies 2024, 17, 5082.

[0013] For a presentation of the state of the art of pyrolysis of polymer materials, one can refer for example to the document Hassibi, study of the pyrolysis of plastic waste: tests and modelling, University of Lorraine, 2023.

[0014] For synthetic polymers composed mainly of carbon and hydrogen, the pyrolysis process is generally carried out at temperatures between 350 °C and 900 °C and results in the formation of a char (solid residues) and a volatile fraction that can be separated into a condensable hydrocarbon oil—composed of paraffins, isoparaffins, olefins, naphthenes, and aromatics—and a non-condensable gas with a high calorific value. Pyrolysis can be purely thermal or thermocatalytic.

[0015] The one-step pyrolytic conversion process of polymer materials uses a high temperature to crack the polymers into their constituent monomers as well as other light hydrocarbons, then the monomers are separated from the other by-products by fractional distillation.

[0016] Two-step processes can also be used to transform plastic waste into monomers. In the first step, various pyrolytic techniques are used to produce a pyrolytic liquid, called naphtha. The next step consists of cracking the pyrolytic liquid, using catalytic cracking or steam cracking.

[0017] The invention relates more particularly to batch-type pyrolysis installations, comprising a closed reactor, or semi-batch, of such installations operating in batches (batch).

[0018] Batch reactors form a closed system, with no product entering or leaving the reactor during pyrolysis. Such reactors offer the advantage of high conversion rates, thanks to the maintenance and control of a perfectly constant pyrolysis temperature during the steady-state (plateau) phase. The main drawback of this type of reactor is the difficulty of large-scale production.

[0019] Semi-batch type reactors allow the addition of reactants and the removal of products (oils, gases). Such reactors allow small-scale production.

[0020] In batch or semi-batch pyrolysis installations, one of the technical problems is the removal of chars at the end of the cycle.

[0021] It is common for tanks to adhere to the bottom of the tank, requiring the use of mechanical tools such as a grinder or a pneumatic needle cleaner to remove them. During tank cleaning, tanks often remain stuck in hard-to-reach corners of the tank.

[0022] To try to overcome this problem, it is known to place brushes or a blade to sweep or scrape the pyrolysis tank. See, for example, documents CN216574715 (Henan, 2022), WO2006092306 (Clyvia, 2006), and JPH08165478 (Hitachi, 1996). However, such arrangements have drawbacks. First, the brushes frequently become clogged. Second, the friction of the brushes or the scraping of the blade against the reactor wall causes rapid wear of these brushes or blades, progressively reducing the effectiveness of tank cleaning. Replacing the brushes or blades is costly and time-consuming, and requires a complete shutdown of the installation.

[0023] Document EP0636674 (HITACHI, 1995) describes a device for producing fuel by pyrolyzing plastic waste containing foreign materials, such as glass or metals. The reactor is located in a furnace equipped with a burner. The plastics to be pyrolyzed are introduced into the furnace through a conduit, and the pyrolysis gases are vented from the furnace for subsequent condensation. Stirring blades are mounted to rotate on a shaft driven by a motor. Inside the drive shaft of the stirring blades, a suction pipe connects the bottom of the tank to a conduit connected to a vacuum pump. Periodic suction of the solid materials contained in the tank is ensured, thus removing the materials by suction without shutting down the apparatus at ambient temperature. Charcoal is removed by suction in the same manner.

[0024] The installation described in document EP0636674 has several disadvantages.

[0025] Firstly, the bottom wall of the reactor is concave, and the suction of tanks and foreign particles is only effective in the lowest part of the vessel.

[0026] Secondly, activating the suction results in the removal of a mixture containing molten plastics, char, and foreign particles such as glass or metals. This mixture must be further processed to separate the char, glass, and metals from the mass of molten plastics.

[0027] Thirdly, the molten plastics that are sucked up cool down in the suction ducts, and can be deposited on the walls of the suction circuit, leading to a reduction in suction cross-section, or even clogging.

[0028] General presentation of the invention

[0029] The invention aims to overcome the drawbacks of the prior art.

[0030] A first object of the invention is to provide a batch or semi-batch pyrolysis process, allowing continuous operation, with periodic removal of chars, without manual cleaning intervention.

[0031] A second object of the invention is to provide a pyrolysis device, of batch or semi-batch type, whose operation can be continuous, the device being provided with means for periodic elimination of chars, without manual cleaning intervention.

[0032] To this end, a pyrolysis process is proposed, according to a first aspect, comprising a preheating phase of a reactor vessel, followed by a heating phase of the reactor vessel to a set temperature, during which the feeding of materials to be pyrolyzed into the vessel begins, advantageously at a perfectly controlled flow rate correlated to the evaporation rate of the pyrolyzable phase, followed by a pyrolysis phase, the so-called "plateau" phase, advantageously at a constant and controlled temperature and during which the constant flow rate of material to be pyrolyzed is maintained, the process comprising, after the pyrolysis phase, a so-called end-of-cycle phase, a temperature ramp-up phase, allowing the chars to dry, then a cooling phase of the vessel to a predetermined temperature, higher than the ambient temperature, followed by a phase of removing the chars contained in the vessel by suction, the process comprising,Between the pyrolysis phase and the end-of-cycle phase, the supply of materials to the tank to be pyrolyzed is stopped.

[0033] The dry chars are thus evacuated very quickly from the pyrolysis tank, while hot, by suction, without it being necessary to cool the tank to ambient temperature before starting a new production cycle.

[0034] Advantageously, the tanks are sucked in without opening the tank.

[0035] The pyrolysis installation operates in batch or semi-batch, continuously, with the production time, for example of fuels, being increased.

[0036] Advantageously, the process comprises, between the pyrolysis phase and the cooling phase, a cessation of the supply of materials to be pyrolyzed to the tank, and a phase of maintaining the tank at a temperature at least equal to the pyrolysis temperature, for a predetermined time.

[0037] At the end of this maintenance phase, the pyrolysis reactor tank contains only char, the other pyrolysis products (oil, gas) having been produced and extracted from the tank in the gaseous phase.

[0038] Advantageously, the process includes, during the pyrolysis phase, stirring the contents of the tank using a mixer, the process including, during the tank evacuation phase, a first step of reversing the direction of rotation of the mixer, and an increase in the rotation speed of the mixer.

[0039] Advantageously, the process includes, during the tank evacuation phase, a second stage of tank suction with maintenance of the mixer rotation speed.

[0040] The tanks contained in the tank are thus stirred and brought partly to the vicinity of the side wall of the tank, to be sucked up.

[0041] Advantageously, the pyrolysis temperature during the maintenance phase is greater than or equal to the setpoint temperature.

[0042] Advantageously, the pyrolysis temperature during the end-of-cycle phase is between 450°C and 650°C and is advantageously around 550°C.

[0043] In some implementations, the process includes, between the cooling phase and the tank evacuation phase, a phase of purging the tank with a neutral gas, for example nitrogen.

[0044] According to various implementations, the materials to be pyrolyzed are polymer materials chosen from the group including polyethylenes (PE), polyethylene terephthalates (PET), polypropylenes (PP), polystyrenes (PS), or biomass (for example wood, straw, agricultural by-products), for the production of fuels, in particular diesel.

[0045] In some implementations, the cooling temperature is between 150°C and 450°C, and is advantageously around 350°C.

[0046] A pyrolysis installation is proposed, according to a second aspect, for the implementation of a process as presented above, the installation comprising a pyrolysis reactor tank, means for preheating and heating the reactor tank, means for supplying the tank with materials to be pyrolyzed, means for evacuating by suction the chars contained in the tank, and means for mixing the contents of the pyrolysis reactor tank.

[0047] Advantageously, the reactor vessel has a flat bottom, and a tank suction duct, connected to a suction unit, opens into the vessel near the bottom of the vessel. These arrangements facilitate the rapid suction of most of the tanks contained in the pyrolysis reactor vessel.

[0048] Advantageously, the mixing means comprise a scraping blade provided with at least one arm for scraping the bottom wall of the reactor vessel. This prevents the chars from adhering to the vessel wall and keeps them in continuous mixing during pyrolysis, facilitating their removal in a hot, dry, and powdery form.

[0049] Description of embodiments

[0050] Other objects and advantages of the invention will become apparent from the description of embodiments given below with reference to the accompanying drawings in which:

[0051] [Fig-1] is a diagram of a pyrolysis installation, according to one embodiment;

[0052] [Fig.2] is a top view and a cross-sectional view of a pyrolysis tank, in a implementation;

[0053] [Fig.3] is a curve showing the evolution of the temperature in degrees Celsius, following two consecutive operating cycles of a pyrolysis installation, according to an implementation, the time on the abscissa being in hours;

[0054] [Fig.4] is an external perspective view of a pyrolysis installation, according to an implementation;

[0055] [Fig.5] is a perspective view of a scraping blade of a pyrolysis tank bottom, according to one embodiment.

[0056] The pyrolysis installation according to the invention advantageously allows the production of fuel, for example diesel, in particular from plastic materials, for example plastic waste.

[0057] In the embodiment shown, the installation includes a reactor vessel 5, heated from the outside using a heat transfer fluid.

[0058] In other embodiments, not shown, the tank is heated by infrared radiant burners, or atmospheric burners (for example, a pressurized gas burner), or by induction.

[0059] The tank 5 is advantageously made of steel, for example of austenitic stainless steel 316L or 304L, or an austenitic stainless steel marketed under reference 253MA (EN 1.4835) or under reference 353MA (EN 1.4854), these steels having high resistance to heat.

[0060] The installation is advantageously designed for the production of fuel from polymeric waste, with the carbonaceous residues (chars) being present in small quantities and thus being waste destined for recovery as carbon black, or for disposal, for example in a final waste landfill. The risk of the presence of metals (e.g., nickel, chromium) in the chars, resulting from tank erosion during pyrolysis, does not pose any difficulties in this case.

[0061] In certain embodiments, the installation is intended for the production of biochars. Biochar here refers to soil amendments produced by biomass pyrolysis.

[0062] In other implementations, the installation is intended for the production of carbon products intended for the chemical industry, these carbon products being intended to be activated for example by plasma, to carry out adsorptions, to be used for pollution control, gas separation, or in catalysis.

[0063] In other implementations, the chars produced by the installation are at least partly combined with biopolymers to form controlled-release fertilizers, or are valorized as substitutes for carbon black.

[0064] When the carbon residue is not a waste that one wishes to dispose of, for example in a final waste landfill, but is a product intended for use, for example in agricultural amendment, or in the chemical industry, the pyrolysis tank is advantageously provided with an internal coating, reducing the risks of contamination by metals (Nickel, Chrome) when the scraping blade rubs against the wall of the tank.

[0065] In one embodiment, the pyrolysis tank 5 is parallelepiped in shape, for example with sides of 700 mm.

[0066] In other embodiments, the tank 5 includes a concave bottom, in particular hemispherical or parabolic, and where appropriate a cylindrical upper part.

[0067] Advantageously, the tank 5 is cylindrical with a flat bottom wall. This arrangement eliminates dead angles and facilitates the complete suction of carbonaceous residues. The diameter of the tank is, for example, 800 mm.

[0068] In the embodiment shown in [Fig. 1], the tank 5 is provided with a double jacket 4 in which a heat transfer fluid circulates, namely combustion fumes from a burner or a burner bank 18.

[0069] The double envelope is advantageously formed of two stainless steel walls.

[0070] In other embodiments, the tank is provided with a double jacket of refractory bricks.

[0071] In the embodiment of [Fig.1], the burner 18 is placed in a furnace 8, arranged under the tank 5.

[0072] The materials to be pyrolyzed, such as for example polymer materials, are introduced into the tank 5 through a conduit 19.

[0073] In certain embodiments, not shown, a gravity feed hopper or a screw conveyor feeds the pyrolysis reactor vessel with the materials to be treated. Where applicable, these materials are subjected to pretreatment (washing, drying, grinding) before entering the vessel.

[0074] The pyrolysis gases are extracted from the tank 5 by a conduit 20, to then be condensed.

[0075] The tank 5 is equipped with a mixer 9, comprising a motor-reducer assembly, rotating a shaft carrying blades 7 equipped with scrapers 21 which rub the surface of the tank 5, and prevent the adhesion of carbonaceous residues (chars) to the wall of the tank 5.

[0076] In one embodiment, the bottom 22 of the tank 5 is flat, and a scraper blade with two arms is rotatably mounted on the axis of the mixer 9.

[0077] In some embodiments, in addition to a bottom scraper blade, the mixer is provided with at least one arm or blade above the scraper blade.

[0078] In some embodiments, a metal brush is arranged on the scraper blade.

[0079] Means ensure the sealing of the mixer's rotation shaft as it passes through the reactor vessel roof. These sealing means include, for example, a housing with packing, a stuffing box, and a temperature-resistant bearing. The term "housing" here refers to a guide bearing for the vertical drive shaft of the mixer blades.

[0080] Outside air can be introduced into the tank 5 by opening an inlet valve 1 and opening a valve 3, arranged on an air suction line 2.

[0081] For the sake of indication, the air intake pipe 2 has an inner diameter of 66 mm, and an outer diameter of 76 mm (DN65).

[0082] The pyrolysis installation includes means for suctioning carbonaceous residues 6 contained in the tank 5.

[0083] The suction means include a suction unit 17, a storage drum 15, and a separator 14.

[0084] The suction means include a conduit 16 connecting the suction unit 17 to the storage drum 15, and a conduit 13 connecting the separator 14 to the pyrolysis tank 5.

[0085] In one embodiment, the separator 14 is cyclonic.

[0086] The air drawn in by the suction unit 17 is advantageously filtered before being rejected outwards.

[0087] The aspiration of the carbonaceous residues 6 contained in the pyrolysis tank 5 is advantageously carried out as follows.

[0088] In a first step, for a predetermined internal temperature of the tank, and for a predetermined time corresponding to a desired end of pyrolysis cycle, the direction of rotation of the blades 7 of the mixer 3 is reversed and the rotation speed of the blades 7 is increased.

[0089] In a second step, and after complete inerting of the reactor, a suction valve 12 disposed on the conduit 13 is opened, and the valve 12 and the check valve 3 are placed in the open position, with the suction unit 17 also being switched on. This results in the aspiration of outside air, which enters the pyrolysis tank 5 through the duct 2. This also results in the aspiration of the carbonaceous residues 6 contained in the pyrolysis tank 5; these carbonaceous residues 6 exit the pyrolysis tank 5 to be sent to the separator 14, before falling into the storage drum 15.

[0090] Advantageously, during this second stage, the rotation of the blades 7, which was increased during the first stage, is maintained.

[0091] After a predetermined suction time, in a third step, the rotation of the blades 7 is reversed again, and the rotational speed of the blades 7 is reduced. The suction valve 12, the supply valve 1, and the check valve 3 are placed in the closed position, and the suction unit 17 is shut down.

[0092] Advantageously, the conduit 13 carrying the suction valve 12 is connected to the pyrolysis tank 5, beyond the suction valve 12, by a conduit 11 opening tangentially or at a small angle with respect to the bottom 22 of the pyrolysis tank 5.

[0093] Pyrolysis cycles with programmed aspiration of the chars 6 take place, for example, as follows, for a production unit such as represented in [Fig. 1]: - a) a preparation phase of the production unit (inerting, leak test), this phase lasting, for example, approximately 15 minutes, - b) a preheating phase of the production unit, for start-up with the reactor vessel 5 empty, this phase lasting, for example, approximately 30 minutes, the preheating temperature being, for example, 250°C, - c) a heating phase of the production unit, with introduction into the vessel 5 of the materials to be pyrolyzed, this phase lasting, for example, approximately 60 minutes, the heating bringing the reactor vessel 5 up to its set temperature, for example, 530°C, - d) a pyrolysis phase, lasting for example from 6 to 9 hours, the internal temperature of reactor vessel 5 being maintained constant throughout this phase, known as the plateau phase, - e) after stopping the supply of materials to be pyrolyzed to tank 5, a short final pyrolysis phase of the materials in tank 5 of the reactor, a maximum quantity of char 6 then being contained in tank 5, this final pyrolysis phase taking place at a temperature greater than or equal to the previously chosen pyrolysis temperature, and lasting for example 30 minutes, - f) a cooling phase for unloading tanks 6 from the production unit, the temperature drop being, for example, from approximately 500°C to

[0094]

[0095]

[0096]

[0097]

[0098] Approximately 200°C in reactor vessel 5, this phase lasting for example approximately 60 minutes, vessel 5 containing only tanks 6, - g) a phase of sweeping the production unit, using a neutral gas, advantageously nitrogen, for degassing the installation (evacuation of flammable gases), this phase lasting for example approximately 10 minutes, - h) a phase of evacuation of tanks 6 by suction, this phase lasting for example 15 minutes, - and again the ah phases for a new cycle (batch). Figure 3 shows an example of variation in internal temperatures of tank 5 of the pyrolysis reactor, during two consecutive cycles. Example of implementation In an example of the implementation of a pyrolysis installation of the type shown in the figures, the suction unit 17 is a pneumatic vacuum cleaner marketed by the company Pharaon, under the name DG70 EXP, this vacuum cleaner having the following properties: - Voltage: 400V-50Hz - power: 5.5 kW, - Motor protection: IP55 - Maximum pressure drop: 3600 mm H2O - Maximum flow rate: 530 m³ / h, - Air inlet: 0.80 mm, - Capacity: 100 liters, - Noise level: 75 dB, - Primary filtration: three antistatic polyester cartridges catM, - total filtering surface: 80,000 cm2, - load on filter: 66 m3 / m2 / h, - H14 absolute cartridge filter - automatic pneumatic counter-current unclogging system. The 15 storage drum is a reinforced separator drum with a cyclone lid, exhibiting the following properties: - 200-litre capacity with a 600 mm diameter opening, - Separator lid with cyclone, 615 mm diameter, - 80mm diameter inlet / outlet Tank 5 of the pyrolysis reactor has the following properties: - inner diameter: 800 mm, - Blades 7 of mixer 9: • straight lines, • blade height: 70mm, • reverse direction of rotation during the suction phase, • geared motor frequency: 80Hz, • rotation speed: 23 revolutions per minute (2.408 rad.s').

[0099] The aspiration of carbonaceous residues 6 (chars) was carried out under the following conditions: - Suction duct 13: DN50 (54.79mm internal), with an angle of incidence of 27° relative to the flat bottom 22 of the tank 5, the suction area being 50 cm2, - air intake pipe 2: DN65 (66.93mm internal diameter), with an angle of incidence of 45° relative to the flat cover of tank 5, - turbine of the suction power plant 17: • flow rate: 600m3 / h, • depression: 3500 mmH2O, • filtering surface: 30,000cm2 / Imicron.

[0100] The carbonaceous residues 6 contained in the tank 5 of the pyrolysis reactor exhibited the following properties: - Tank load in reactor vessel 5: 19.5 kg, - density: 791kg / m3, - Thickness of the perfect char layer in tank 5 of the pyrolysis reactor (charge / density ratio): 50 mm - Thickness of the measured char layer in tank 5 of the pyrolysis reactor: approximately 70mm.

[0101] Two tests were carried out, under the conditions presented above.

[0102] For the first test, the suction of 18.77 kg of tanks 6 was carried out in approximately After 90 seconds, the amount of unvacuumed tanks after 90 seconds was limited to 0.73kg (3.74%).

[0103] For the second test, the suction of 18.95kg of tanks 6 was carried out in about 120 seconds, the quantity of tanks not suctioned after 120 seconds was limited to 0.55kg (2.82%).

[0104] The invention has many advantages.

[0105] The dry chars are evacuated very quickly from the pyrolysis tank, while hot, by suction, without it being necessary to cool the tank to ambient temperature before starting a new production cycle.

[0106] The pyrolysis installation thus operates in batch or semi-batch, continuously, with the production time, for example of fuels, being increased.

[0107] The masses extracted from the tank by suction are solids, and not mixtures comprising solids, oils, and gases. The risk of clogging of the suction lines is thus avoided, and the products extracted by suction (solids) can be stored directly in drums.

[0108] The tanks are removed without opening the pyrolysis chamber, without any manual contact with the tanks, and without any release of pyrolysis gas into the atmosphere; the tanks are removed only after complete pyrolysis of the materials in the chamber. Personnel safety is thus ensured.

[0109] The evacuation of the tanks can be programmed, for example using an APL. The pyrolysis unit can thus operate continuously, without operator intervention, other than, for example, remote monitoring or maintenance. The unit can therefore be placed as close as possible to a source of material to be pyrolyzed, for example, a temporary biomass deposit during agricultural work, or a site polluted by polymer waste. The unit is advantageously containerized, facilitating its transport to the site of use.

[0110] The adhesion of the tanks to the bottom wall of the tank is avoided by scraping this bottom wall, and the tanks to be evacuated are dry and kept in a powdery state.

[0111] Increasing the rotation speed of the mixer blades and reversing the direction of rotation of the blades promotes the movement of carbon residues towards the periphery of the pyrolysis reactor vessel, and the aspiration of these residues through a conduit entering tangentially or at a small angle to the bottom wall of the vessel.

Claims

Demands

1. A pyrolysis process comprising a preheating phase of a reactor vessel (5), followed by a heating phase of the reactor vessel (5) to a setpoint temperature, during which the feeding of materials to be pyrolyzed into the vessel (5) begins, followed by a pyrolysis phase, the process being characterized in that it comprises, after the pyrolysis phase, a so-called end-of-cycle phase, of temperature rise, allowing the chars to dry, then a cooling phase of the vessel (5) to a predetermined temperature, higher than the ambient temperature, followed by a phase of evacuation of the chars contained in the vessel (5), by aspiration, the process comprising, between the pyrolysis phase and the end-of-cycle phase, a stopping of the feeding of materials to be pyrolyzed into the vessel (5).

2. Pyrolysis process according to claim 1, characterized in that it comprises, during the pyrolysis phase, agitation of the contents of the tank (5) using a mixer (9), the process comprising, during the tank evacuation phase, a first step of reversing the direction of rotation of the mixer (9), and an increase in the rotation speed of the mixer (9).

3. Pyrolysis process according to claim 2, characterized in that it comprises, during the char evacuation phase, a second char aspiration stage, with maintenance of the rotation speed of the mixer (9).

4. Pyrolysis process according to any one of claims 2 to 3, characterized in that the pyrolysis temperature during the end-of-cycle phase is between 450°C and 650°C and is advantageously in the order of 550°C.

5. Pyrolysis process according to any one of claims 1 to 4, characterized in that it comprises, between the cooling phase and the tank evacuation phase, a phase of cleaning the tank (5) with a neutral gas.

6. A pyrolysis process according to any one of 1 to 5, characterized in that the materials to be pyrolyzed are polymer materials selected from the group including polyethylenes, polyethylene terephthalates, polypropylenes, polystyrenes, or biomass, for the production of fuels.

7. Pyrolysis process according to any one of claims 1 to 6, characterized in that the cooling temperature is between 150°C and 450°C, and is advantageously in the order of 350°C.

8. Pyrolysis installation for carrying out a process as presented in any one of claims 1 to 7, the installation comprising a pyrolysis reactor vessel (5), means for preheating and heating the reactor vessel (5), means for supplying the vessel (5) with materials to be pyrolyzed, means for removing chars (6) contained in the vessel (5) by suction, and means for mixing the contents of the pyrolysis reactor vessel (5).

9. Pyrolysis installation according to claim 8, characterized in that the reactor vessel (5) has a flat bottom (22), a suction duct (11) for the tanks (6), connected to a suction unit (17), opening into the vessel (5) near the bottom (22) of the vessel.

10. Pyrolysis installation according to claim 8 or 9, characterized in that the mixing means comprise a scraping blade (21) provided with at least one arm for scraping the bottom wall (22) of the reactor vessel.

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