Method for recovering carbon black by solvolysis of used elastomers

Abstract

The present invention relates to the field of recovering carbonaceous materials of the carbon black type, in particular carbon blacks referred to as "recovered" carbon blacks (rCB) by means of a method for the solvolysis of used elastomers. It relates to a method for preparing recovered carbon black by means of a method for the solvolysis of used elastomers, which involves recycling a hydrocarbon cut comprising aromatic compounds, followed by a step of centrifuging the solvolysis effluent and carrying out conduction drying in order to obtain the recovered carbon black.

Description

[0001] PROCESS FOR RECOVERING CARBON BLACK BY SOLVOLYSIS OF USED ELASTOMERS

[0002] Scope of the invention

[0003] The present invention relates to the field of recovery of carbon materials of the carbon black type, in particular to so-called "recovered" carbon blacks (or rCB for "recovered carbon black" according to Anglo-Saxon terminology) by a solvolysis process of used elastomers.

[0004] State of the art

[0005] Elastomers are chemically cross-linked polymers of natural or synthetic rubber. Due to their chemical bonds, they do not melt but begin to decompose at high temperatures. Natural rubber is primarily composed of polyisoprene, a natural polymer found in the rubber tree (Hevea brasiliensis) and guayule. Synthetic rubbers are either general-purpose or specialty rubbers and are created by combining different polymers, monomers, and laminates.Common synthetic rubbers include (but are not limited to) styrene-butadiene copolymer (SBR), polybutadiene (BR), isobutylene-isoprene copolymer (HR, Cil R, BIIR), rethylene-propylene-diene monomer (EPDM), polychloroprene (CR), acrylonitrile-butadiene copolymer (NBR, HNBR), chlorosulfonated polyethylene (CSM), fluoroelastomer (FKM), polyacrylate rubber (ACM), epichlorohydrin rubber (ECO) and silicone rubber (VMQ).

[0006] These materials are used to manufacture various objects such as tires for light vehicles, heavy goods vehicles, two-wheelers or any type of special equipment, treads in conveyor systems, vehicle door seals, but also objects like shoe soles or rubber boots.

[0007] At the end of their life cycle, these elastomer-rich objects undergo a granulation process to facilitate their material recovery. This process isolates the elastomer-rich components and removes most of the other constituents (such as the metallic or synthetic fabrics and fibers often incorporated into elastomers to enhance their properties), resulting in granules generally smaller than 25 mm. Granulation typically involves a series of grinding and separation steps, yielding a final material composed of the elastomer and any reinforcing fillers incorporated with it, such as carbon black or silica.Carbon black (or CB, as it is known in English) is used in tire formulations to improve tire durability (in terms of strength and lifespan), to limit tire deformation during use, and to facilitate heat transfer between the tire and the road surface. It is generally obtained through the incomplete combustion of hydrocarbons or vegetable oils, and more than 35 grades are commercially available and used as fillers (primarily in tire compound formulations). Their quality varies according to their intrinsic properties.

[0008] Most carbon blacks are characterized by high elemental carbon content (>90% by weight relative to the total weight of the carbon black) and may contain other chemical elements such as hydrogen, oxygen, nitrogen, and sulfur, which are chemically bonded to the carbon. They generally appear as black powders composed of graphitic (more or less well-crystallized) and quasi-spherical (10 to 500 nm) elemental particles, forming aggregates (100 nm to 1000 nm) that can themselves clump together into agglomerates (1 µm to 100 µm), which can then be transformed into granules (0.1 to 1 mm). The size of the elemental particles and the structure of the objects (morphology, size, density / aeration of the aggregates / agglomerates) will significantly impact the ability of carbon blacks to disperse within an elastomeric matrix and, therefore, ultimately, their reinforcing properties within that matrix.The specific surface area (or SBET) parameter, determined by nitrogen physisorption, is characteristic of the size of the elementary particles and indicates the surface area of ​​the carbon black potentially interacting with the elastomeric matrix. The structure of a carbon black is characterized by its ability to develop porosity that can be filled by a paraffinic oil, and therefore ultimately by an elastomeric matrix. A structure index, equivalent to an oil adsorption index, is then determined, the associated analytical method being the OAN (Oil Adsorption Number) method. Each carbon black is then assigned a code of the type NXYZ, where X is a number characteristic of the carbon black's SBET, and Y and Z are numbers arbitrarily assigned based on the observed structure.In summary, there is a relationship between SBET and OAN structure index that allows for the classification of various carbon blacks according to their grade and whether they have a reinforcing or non-reinforcing effect. For example, N110, N120, and N234 carbon blacks, which are excellent reinforcing additives, are characterized by a high specific surface area and structure index. Depending on their intrinsic properties, carbon blacks are used to formulate different rubber compounds, which are themselves used in the various components of a tire. During recycling, elastomer-rich materials are generally initially ground to obtain either elastomer granules still containing some textile and metallic fibers (typically pieces from 1 to 10 cm), or granules (generally smaller than 6 mm) free of all fibers.It is then possible to convert them into gaseous, liquid, and solid fractions via thermal decomposition processes. The resulting solid fraction consists mainly of various grades of carbon black mixed with inorganic ash (primarily silica and zinc-based compounds). Furthermore, the thermal decomposition of the elastomer fraction generates various carbon compounds (various decomposition products, possibly recondensed) that can be deposited on the surface of the carbon black. Similarly, depending on the operating conditions of these processes, undecomposed elastomer polymer chains can be adsorbed onto the surface.For a given conversion process applied to a specific "used elastomer" feedstock, the recovered carbon black represents the entire solid fraction consisting of the initial carbon black mixed and modified on the surface by various carbon deposits (decomposition products and / or elastomer residues), as well as inorganic ash. The intrinsic properties of recovered carbon black therefore depend on its constituent elements. In particular, the chemical composition of the recovered carbon black, the agglomeration rate of the aggregates and their structure, and consequently the redispersion properties of the recovered carbon black in an elastomer matrix, can be drastically altered compared to those of the initial carbon black depending on the composition of the end-of-life tires processed (choice of feedstock) and the recycling process used.

[0009] Among the possible thermal decomposition conversion processes for treating end-of-life elastomers, particularly tires, pyrolysis processes are very frequently encountered (J. Yu et al., Frontiers of Environmental Science & Engineering, 2020, 14, 2, 7982; SQ Li et al., Ind. Eng. Chem. Res. 2004, 43, 5133; EP2661475). They usually consist of exposing the elastomers to temperatures between 350°C and 800°C in the absence of oxygen, or in the presence of a very small amount of oxygen or air intended to provide, through very partial combustion, the energy necessary for the pyrolysis process. This last step takes place at the atmospheric pressure of the gas(s) in question or sometimes under vacuum, in order to minimize the secondary post-degradation reactions of the tire rubbers which frequently lead to the formation of residual carbon deposits on the surface of the final recovered carbon black already mentioned.The yields of these processes for recovered carbon black are highly variable (between approximately 25% and 60%), as are their intrinsic properties (for example, the residual inorganic ash content can vary from 8% to 41% by weight). In contrast, recovered carbon black obtained after pyrolysis (also frequently called "pCB") is characterized by the significant presence of carbon deposits on the surface of the initial carbon black. These deposits are characterized using X-ray Photoelectron Spectroscopy (XPS), also known as ESCA ("Electron Spectroscopy for Chemical Analysis"). This surface analysis primarily allows for the determination of the elemental chemical composition of a material and thus the concentrations of C, O, N, S, Si, Al, Zn, etc.In a second step, the precise analysis of the spectrum associated with the carbon element (C1s spectrum) provides information on the chemical environment of the carbon atoms constituting the recovered carbon black (Ludovic Moulin thesis: Valorization of recovered carbon black, process-product relationship. Process Engineering. Ecole des Mines d'Albi-Carmaux, 2018). It notably allows us to distinguish the carbon associated with the initial carbon blacks (Co peak corresponding to a bond energy of approximately 284.2 / 284.8 eV, characteristic of CC / CH bonds in a graphitic structure) from that relating to carbon compounds likely to be deposited on the surface (Ci peak corresponding to a bond energy of approximately 284.8 / 285.6 eV, characteristic of CC / CH bonds in aliphatic structures or small aromatic compounds, associated here with the carbon deposits formed during the pyrolysis processes).Thus, pCBs exhibit carbon deposit contents, assessed as a percentage of area by XPS, ranging from 5% to 40% (calculation based on the total area of ​​the previously described Co and Ci peaks and the C2, C3, C4, and C5 peaks respectively attributed to CO, C=O, COOH bonds and TT-TT* transitions). These carbon deposits are largely responsible for the agglomeration phenomena linking the various structures of the recovered carbon blacks at different scales: the solid exiting the reactor is often present in the form of blocks several millimeters / centimeters in size, which must then be finely ground in order to be reused (notably as an admixture for the formulation of new gums), which requires significant energy expenditure.It should be noted that these carbon deposits seem strongly linked to the surface of the initial carbon blacks since even thermal post-treatments at higher temperatures than the pyrolysis process itself are not enough to eliminate them (change from 40% to 20% of the area of ​​the Ci peak for a post-pyrolysis thermal treatment at 600°C: H. Darmstadt et al., Carbon, 1995, 33, 10, 1449).

[0010] To limit the formation of carbon deposits on the recovered carbon black, it is possible to lower the partial pressure of hydrocarbons by injecting steam during the cracking reactions (steam-thermolysis processes). Unfortunately, the high temperature conditions generally applied (often exceeding 500°C) still lead to the formation of carbon deposits, albeit in limited proportions (5 to 6% of the peak area in Ci). Furthermore, these gas-solid processes have other drawbacks. Indeed, they generally induce high productions of non-condensable gases (under atmospheric conditions), often between 10% and 25% by weight relative to the spent elastomer feed into the reactor, which is detrimental to the quantity of potentially recoverable and easily usable liquid products.Indeed, these liquid fractions can be used to produce new hydrocarbon cuts (naphtha, gasoline, kerosene, diesel, vacuum distillate, residues), used in refineries to produce fuels or in petrochemicals to produce bases used to then develop plastics.

[0011] Another interesting alternative approach to limiting the presence of these carbon deposits on recovered carbon black involves contacting the elastomer fillers with a liquid under suitable operating conditions (particularly temperature) and dissolving and converting the elastomers in a homogeneous liquid phase in which the elastomer filler is agitated and gradually disappears. US patents 3,978,199 and 3,704,108 disclose processes for converting spent elastomers that include a step of dissolving the solid elastomer-based filler in the presence of a solvent corresponding to a recycle stream of the heavy liquid fraction of the filtrate obtained after distillation, which includes aromatic-rich compounds (preferably monoaromatic).Unfortunately, the conditions for implementing such processes, and more specifically the choice of a heavy liquid fraction as a solvent, are not favorable to preventing the formation of carbon deposits contained in the final recovered carbon black.

[0012] French patent FR2009912 discloses a process for converting elastomers from used tires to produce a so-called "recycled" carbon black (recovered carbon black) with a very low content of carbon residues (decomposition products of tire rubber and / or elastomer residues). This process also limits the agglomeration of the various structures of the recovered carbon black commonly encountered in processes described in the literature. The process involves recycling a batch of used tires at a temperature of 400°C or lower and a pressure of less than 1.5 MPa by contacting the batch with a solvent consisting of at least one hydrocarbon fraction. This fraction must be rich in aromatic compounds, low in C40+ compounds (vacuum residues), and have a moderate content of C5-C10 hydrocarbon compounds (gasoline). The solvent may be produced by the process itself (recycled).The operating conditions, the composition of the hydrocarbon fraction, and the solvent / solid feed mass ratio, as defined, maximize the production of recovered carbon black through improved dissolution / decomposition of the solid feed while minimizing the presence of carbon residues in the final recovered carbon black. The carbon black recovery step in the solvolysis effluent (recovered carbon black) is carried out by frontal filtration, solvent washing, and then drying. The washing solvent for the filtered cake is chosen from toluene or xylene to lower the viscosity of the medium and facilitate frontal filtration and drying. Solvent regeneration steps by distillation are then necessary to purify and recycle the solvent within the process, which requires significant energy consumption.

[0013] It turns out that frontal filtration of a mixture of hydrocarbon liquid and solid carbon black particles is not a suitable separation technology for the recycling process of spent elastomers when the carbon black particles are very fine, i.e., between 1 µm and 30 µm. This results in the formation of a paste rather than a cake on the filter medium. The filtration flow rate is then prohibitive for industrial implementation.

[0014] In patent FR2387763, an alternative method is to separate the carbon black from the solvent by pure heat treatment without prior liquid / solid separation (evaporation and / or Soxhlet extraction). All the solvent is thus evaporated and the carbon black dried, which requires significant energy expenditure.

[0015] US patent 3890141 discloses a process for converting solid waste from used tires into thermal energy while recovering metal oxides such as zinc oxide and titanium oxide. The densest carbon black particles contained in the used elastomers can potentially be recovered upstream of the combustion stage by sedimentation and / or centrifugation. No operating conditions are specified in the patent.

[0016] US patent 6525105 discloses a process for liquefying gum, vulcanized or unvulcanized, at ambient temperature and pressure in an organic solvent containing peroxide. The carbon black can be recovered by a centrifugation, membrane separation, or sedimentation step, but no operating conditions are specified in the patent.

[0017] The recovery of carbon black contained in the solvolysis slurry therefore appears critical from an operability and cost point of view.

[0018] The Applicant has developed a new solvolysis process for converting spent elastomers to overcome these drawbacks in order to recover carbon black. This process combines a solvolysis reaction step with optimized liquid / solid separation and carbon black drying steps to recover high-quality carbon black, with ease of operation and controlled energy costs. The process involves recycling an elastomer feedstock by contacting it with a solvent consisting of at least one hydrocarbon fraction. This fraction must be rich in aromatic compounds, low in C40+ compounds (vacuum residues), and have a moderate content of C5-C10 hydrocarbon compounds (gasoline). The solvent may be produced from the process itself (recycled). The operating conditions, the composition of the hydrocarbon fraction, and the solvent / solid feedstock mass ratio, as defined, allow for:

[0019] - minimize gas production and therefore maximize the oils of interest;

[0020] - to generate higher quality oils by limiting their total aromatic content and within the aromatics by significantly limiting the proportion of heavy aromatics;

[0021] - to maximize the production of recovered carbon black via better dissolution / decomposition of the solid feedstock while limiting the presence of carbon residues in the final recovered carbon black.

[0022] The liquid / solid separation of the suspension (slurry, according to Anglo-Saxon terminology) obtained downstream of the solvolysis reactor is then carried out by at least one centrifugation step to remove as much liquid as possible using a low-energy physical method, followed by a drying step to remove the residual liquid using a moderate thermal method. This sequence eliminates the need for liquid percolation through a compact cake and the energy-intensive washing step. Furthermore, optimizing the formulation of the internal solvent, which consists of a fraction of light and heavy oil, significantly reduces the temperature required during the drying step.

[0023] Objects of the invention

[0024] The present invention relates to a process for converting used elastomers by solvolysis to obtain recovered carbon black, said process comprising at least the following steps: a) a solid charge of used elastomers is sent into a reaction zone in the presence of a liquid solvent comprising aromatic compounds to dissolve at least part of said solid charge and thermally decompose said at least partially dissolved solid charge at a temperature below 400°C and at a pressure below 1.5 MPa in order to obtain a first gaseous effluent and a first liquid effluent comprising the carbon black, the mass ratio between the liquid solvent and the solid charge being greater than 3 weight / weight;b) the first liquid effluent obtained in step a) is sent to a centrifugation zone at a centrifugal force of between 1000 G and 16000 G for a period of between 30 seconds and 30 minutes in order to obtain a centrifuged carbon black cake and a second liquid effluent; c) at least part of said first gaseous effluent obtained at the end of step a), at least part of a second gaseous effluent obtained at the end of step e) and at least part of the second liquid effluent obtained at the end of step b) are sent to a fractionation zone to obtain at least one light hydrocarbon cut having a final boiling point of between 250°C and 325°C and at least one hydrocarbon cut comprising an aromatic compound content of more than 30% by weight relative to the total weight of said hydrocarbon cut, and further comprising:;

[0025] - a C5-C10 hydrocarbon compound content of less than 20% by weight relative to the total weight of the hydrocarbon fraction; and

[0026] - a C40+ hydrocarbon content of less than 5% by weight relative to the total weight of said hydrocarbon cut; d) at least a portion of said light hydrocarbon cut and at least a portion of said hydrocarbon cut obtained at the end of step c) are sent into the reaction zone as the liquid solvent of step a), characterized in that the mass ratio between said hydrocarbon cut and the liquid solvent is between 0.2 and 0.95 weight / weight; e) the centrifuged carbon black cake obtained at the end of step b) is dried in a conduction drying zone at a temperature between 150°C and 350°C, a vacuum pressure between 0.0001 MPa and 0.01 MPa absolute, under agitation between 2 rpm and 150 rpm for a period between 1 hour and 8 hours to obtain the recovered carbon black and said second gaseous effluent.

[0027] Advantageously, the mass ratio between said hydrocarbon cut and the liquid solvent is between 0.4 and 0.9 weight / weight.

[0028] Advantageously, the centrifugation force of step b) is between 2000 G and 8000 G.

[0029] Advantageously, the centrifugation time in step b) is between 1 minute and 20 minutes.

[0030] Advantageously, the volatile organic compound content in the recovered carbon black obtained at the end of step e), measured by thermogravimetric analysis known as TGA, is less than 10% by weight of volatile organic compounds in said recovered carbon black.

[0031] Advantageously, the second liquid effluent obtained at the end of step b) consists of at least 40% by weight of the first liquid effluent.

[0032] Advantageously, the agitation speed in the conduction drying zone of step e) is between 5 rpm and 100 rpm. Preferably, the agitation speed in the conduction drying zone of step e) is between 10 rpm and 80 rpm.

[0033] Advantageously, step e) of drying is carried out at an absolute vacuum pressure between 0.0002 MPa and 0.005 MPa.

[0034] Advantageously, step e) of drying is carried out at a temperature between 200°C and 320°C.

[0035] Advantageously, the duration of step e) of drying is between 2 hours and 7 hours.

[0036] Preferably, the duration of step e) of drying is between 3 hours and 6 hours.

[0037] Advantageously, step a) comprises the following substeps: a1) said solid feed and said liquid solvent are sent into a first stirred reactor to dissolve at least part of said solid feed; a2) said at least partially dissolved solid feed obtained at the end of step a1) is sent into a second stirred reactor to thermally decompose said solid feed at a temperature less than or equal to 400°C and obtain a liquid effluent containing suspended carbon black particles.

[0038] Advantageously, the aromatic compound content of the hydrocarbon cut is greater than 40% by weight relative to the total weight of said cut.

[0039] Advantageously, the solid charge (100) is based on used tires.

[0040] List of figures

[0041] Figure 1 is a schematic representation of an embodiment of obtaining carbon black according to the invention.

[0042] Detailed description of the invention

[0043] 1. Definitions

[0044] By hydrocarbon Cn cut, we mean a cut comprising hydrocarbons with n carbon atoms.

[0045] A Cn+ section is defined as a section containing hydrocarbons with at least n carbon atoms. The BET specific surface area is measured by nitrogen physisorption according to ASTM D3663-03 as described in Rouquerol F.; Rouquerol J.; Singh K. "Adsorption by Powders & Porous Solids: Principle, methodology and applications", Academic Press, 1999.

[0046] The CHNS-O elemental analyzer, made according to the ASTM D5291 standard, is a method well known to those skilled in the art, allowing the rapid determination of the content of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) in organic matter and other types of materials, based on the total combustion of the analytical sample at 1000°C under oxygen.

[0047] The carbon residue content is assessed by the X-Ray Photoelectron Spectroscopy (XPS) surface analysis technique, well known to those skilled in the art, and, in particular, by the precise analysis of the spectrum associated with the carbon element (C1s spectrum) which provides information on the chemical environment of the C atoms constituting the recovered carbon black. Indeed, the content of said carbon residues is determined by the % area of ​​the peak Ci corresponding to a bond energy of approximately 284.8 / 285.6 eV, characteristic of CC / CH bonds of aliphatic structures or small aromatic compounds, associated with said residues and calculated in relation to the total area of ​​the peaks Co to Cs (Co being the peak associated with CC / C-H bonds of a graphitic structure and C2, C3, C4 and C5 the peaks respectively attributed to CO, C=O, COOH bonds and TT-TT* transitions).The method for measuring the carbon residue content is described in detail in the publication by Darmstadt H., Roy C., Kaliaguine S., "Characterization of pyrolytic carbon blacks from commercial tire pyrolysis plants Carbon" (1995), Carbon, Volume 33, No. 10, pp. 1449-1455, as well as in the publication by Sahouli, Bendida; Blacher, Silvia; Brouers, François; Darmstadt, Hans; Roy, Christian; Kaliaguine, Serge: "Surface morphology and chemistry of commercial carbon black and carbon black from vacuum pyrolysis of used tyres" (1996), Fuel, Vol. 75, No. 10, pp. 1244-1250, and also in the thesis by Ludovic Moulin: Valorisation du noir de carbone retrouvée, relation processus-produit. Génie des processus. Ecole des Mines d'Albi-Carmaux, 2018.

[0048] Thermogravimetric analysis is a widely used and well-known technique for those skilled in the art, used to measure the moisture content, volatile organic compound (VOC) content, and ash content of recovered carbon black. The protocol used is derived from the ISO 9924-2 standard, primarily used for vulcanizates and unvulcanized mixtures. An initial heating from 25°C to 600°C under nitrogen allows for the measurement of water content (mass loss in % between 25°C and 150°C) and the content of VOCs and / or pyrolyzable phase (mass loss between 150°C and 600°C). Following this first step, the sample is then cooled under nitrogen to 400°C. A second heating, under air, from 400°C to 950°C allows for carbon combustion and the measurement of the amount of carbon (recovered carbon black and any carbonaceous residues). The final mass measured at the end of the protocol allows the mineral content to be determined.This method of analysis is described in detail in the publication by Norris, C.; Hale, Mike; Bennett, M. (2014) “Pyrolytic carbon: Factors controlling in-rubber performance”, Plastics, Rubber and Composites, vol. 43, p. 245-256.

[0049] Unless otherwise specified, pressure is defined as absolute pressure and expressed in MPa.

[0050] The number of Gs is defined as the ratio between the acceleration considered and the acceleration due to Earth's gravity (9.81 m / s²). 2 ).

[0051] The average size of carbon black particles in the liquid effluent is measured by laser particle size analysis (Mastersizer 3000).

[0052] 2. Description

[0053] The present invention relates to a process for converting spent elastomers by solvolysis to obtain recovered carbon black (520), said process comprising at least the following steps: a) a solid feed (100) based on spent elastomers is sent into a reaction zone (80) in the presence of a liquid solvent (760) comprising aromatic compounds to dissolve at least partially said solid feed and thermally decompose said at least partially dissolved solid feed at a temperature below 400°C and at a pressure below 1.5 MPa in order to obtain a first gaseous effluent (310) and a first liquid effluent (320) comprising the carbon black,the mass ratio between the liquid solvent (760) and the solid feed (100) being greater than 3 weight / weight b) the first liquid effluent (320) obtained in step a) is sent into a centrifugation zone (40) at a centrifugal force between 1000 G and 16000 G for a time between 30 seconds and 30 minutes in order to obtain a centrifuged carbon black cake (420) and a second liquid effluent (410); c) at least part of said first gaseous effluent (310) obtained at the end of step a) is sentat least partly a second gaseous effluent (510) obtained at the end of step e) and at least partly the second liquid effluent (410) obtained at the end of step b) to a fractionation zone (70) to obtain at least one light hydrocarbon cut (720) having a final boiling point between 250°C and 325°C and at least one hydrocarbon cut (730) comprising an aromatic compound content exceeding 30% by weight relative to the total weight of said hydrocarbon cut (730), and further comprising,

[0054] - a C5-C10 hydrocarbon compound content of less than 20% by weight relative to the total weight of the hydrocarbon fraction; and

[0055] - a C40+ hydrocarbon content of less than 5% by weight relative to the total weight of said hydrocarbon cut; d) at least a portion of said light hydrocarbon cut (720) and at least a portion of said hydrocarbon cut (730) obtained at the end of step c) are sent into the reaction zone (80) as liquid solvent (760) of step a), characterized in that the mass ratio between said hydrocarbon cut (730) and liquid solvent (760) is between 0.2 and 0.95 weight / weight; e) the centrifuged carbon black cake (420) obtained at the end of step b) is dried in a conduction drying zone (50) at a temperature between 150°C and 350°C, a vacuum pressure between 0.0001 MPa and 0.01 MPa absolute, under agitation between 2 rpm and 150 rpm for a period between 1 hour and 8 hours to obtain the recovered carbon black (520) and said second gaseous effluent (510).

[0056] The charge

[0057] The solid filler (100) used in the present invention is advantageously based on used elastomers that can come from any source, from tires of light vehicles (LV) or heavy goods vehicles (HGV), two-wheelers or any type of special equipment, vehicle door seals, but also from objects such as shoe soles or rubber boots. Preferably, the solid filler (100) is based on used tires and / or vehicle door seals, and more preferably on used tires.

[0058] The said solid filler can advantageously be in the form of elastomer granules, i.e. in the form of particles of sizes less than 25 mm containing more than 80% elastomers and reinforcing filler (carbon black, silica, ...), from the treatment of end-of-life waste containing large quantities of elastomers.

[0059] Thus, according to a preferred embodiment of the invention, the solid feed (100) is sent to a pretreatment unit (10) to remove textile fibers and metal threads (110) from the solid feed (100). Such a pretreatment unit is well known to those skilled in the art and can consist of various types of grinders (i.e., a rotary shear, a shredder, a granulator, a refiner), a magnetic separator, or even a vibrating screen or a separation table. According to step a) of the conversion process, the gum contained in the solid feed (100) is dissolved upon contact with the liquid solvent (760) and then thermally decomposed. The origin and composition of the liquid solvent (760) will be described in detail below.Step a) is preferably carried out at a temperature below 400°C, preferably between 365°C and 395°C, and even more preferably between 380°C and 395°C, and at a pressure below 1.5 MPa absolute, preferably between 0.2 MPa and 1.2 MPa absolute. At the end of step a), at least one gaseous effluent (310) and the first liquid effluent (320) are obtained, comprising carbon black and possibly solid material residues (210) contained in the used elastomers, particularly in used tires, such as metal wires or textile fibers, which are released and separated from the liquid effluent (320) obtained at the end of this step. The mass ratio between the liquid solvent (760) and the solid filler (100) is greater than 3 weights / weights, preferably between 3 weights / weights and 10 weights / weights, more preferably between 4 weights / weights and 7 weights / weights.

[0060] Advantageously, the residence time in the reaction zone (80) is between 0.5 hours and 4 hours.

[0061] According to one or more embodiments, step a) comprises the following substeps: a1) said solid feed and said liquid solvent are sent into a first stirred reactor to dissolve at least part of said solid feed; with a residence time between 30 minutes and 2 hours, at a temperature less than or equal to 300°C; a2) the liquid effluent obtained at the end of step a1) is sent into a second stirred reactor to thermally decompose said solid feed at a temperature less than or equal to 400°C (residence time between 30 minutes and 2 hours) and obtain a liquid effluent containing suspended carbon black particles.

[0062] The first liquid effluent (320), containing carbon black, is then sent to a centrifugation zone (40) to recover a centrifuged carbon black cake (420) and a second liquid effluent (410). This step is advantageously carried out at a temperature between 5°C and 350°C, preferably between 50°C and 300°C. According to a particular embodiment of the invention, a heat exchanger (not shown in Figure 1) reduces the temperature of the first liquid effluent (320) between the reaction zone (80) and the centrifugation zone (40). The centrifugal force is between 1000 G and 16000 G, preferably between 2000 G and 8000 G, and preferably between 3000 G and 6000 G. Those skilled in the art can use any type of centrifuge technology, including a plate centrifuge or a decanter centrifuge.

[0063] The centrifugation time is between 30 seconds and 30 minutes, preferably between 1 minute and 20 minutes, and more preferably between 2 minutes and 10 minutes.

[0064] Centrifugation under the conditions of the invention allows for good liquid / solid separation efficiency.

[0065] The second liquid effluent (410) is preferably made up of more than 40% by weight of the first liquid effluent (320), more preferably more than 60% by weight of the first liquid effluent (320).

[0066] The second liquid effluent (410) is then sent to the fractionation column (70).

[0067] To lower the volatile organic compound (VOC) content of the recovered carbon black (520), either because the required target content decreases or because the vacuum drying equipment cannot reach a sufficiently high temperature or low pressure, a second centrifugation step is optionally considered to dilute the concentration of the heaviest hydrocarbons resulting from the feed conversion (100) and those most difficult to remove during the drying step (50). The centrifuged carbon black cake (420) from the first centrifugation step b) will be repelled in solvent (720), (730), or (760) in a stirred tank and centrifuged again to reduce the concentration of the heaviest hydrocarbons in the second-centrifuged carbon black (the centrifuged liquid containing some of the heaviest hydrocarbons).

[0068] At least part of the first gaseous effluent (310) obtained at the end of step a), at least part of a second gaseous effluent (510) obtained at the end of step e), and at least part of the second liquid effluent (410) obtained at the end of step b) are sent to a fractionation zone (70) to obtain at least one light hydrocarbon cut (720) having a final boiling point between 250°C and 325°C and at least one hydrocarbon cut (730) comprising an aromatic compound content exceeding 30% by weight relative to the total weight of said hydrocarbon cut (730), and furthermore comprising

[0069] - a content of hydrocarbon compounds O5-O10 of less than 20% by weight in relation to the total weight of the hydrocarbon cut; and - a content of hydrocarbon compounds C40+ of less than 5% by weight in relation to the total weight of said hydrocarbon cut;

[0070] Advantageously, the hydrocarbon cut (730) also comprises a content of C10-C20 hydrocarbon compounds of between 20% by weight and 65% by weight relative to the total weight of the hydrocarbon cut, preferably between 30% by weight and 65% by weight, and even more preferably between 45% by weight and 65% by weight.

[0071] Advantageously, the hydrocarbon cut (730) also comprises a content of C20-C40 hydrocarbon compounds of between 30% by weight and 80% by weight relative to the total weight of the hydrocarbon cut, preferably between 30% by weight and 70% by weight, and even more preferably between 30% and 55% by weight.

[0072] Advantageously, the hydrocarbon cut (730) also comprises a content of C20-C40 hydrocarbon compounds of between 30% by weight and 80% by weight relative to the total weight of the hydrocarbon cut, preferably between 30% by weight and 70% by weight, and even more preferably between 30% and 55% by weight.

[0073] Advantageously, the hydrocarbon cut (730) has an initial boiling temperature between 50°C and 325°C, preferably between 50°C and 250°C, and a final boiling temperature between 350°C and 520°C, preferably between 350°C and 450°C.

[0074] Advantageously, the light cut (720) comprises at least a C10- hydrocarbon compound content greater than 60% by weight relative to the total weight of the light cut (720).

[0075] Advantageously, the fractionation zone (70) also allows the obtaining of non-condensable gases (710), and a heavy cut (740), whose initial boiling temperature is preferably between 350°C and 450°C.

[0076] Advantageously, the heavy cut (740) comprises a C40+ hydrocarbon compound content exceeding 60% by weight relative to the total weight of the heavy cut (740).

[0077] According to the invention, at least part of a fraction of the light hydrocarbon cut (720) and at least part of the hydrocarbon cut fraction (730) are sent to the reaction zone (80) of step a) as a liquid solvent (760), the other parts (750) and (770) being advantageously sent outside the process according to the invention as a valuable product. The mass ratio between the liquid solvent (760) and the flow rate of the solid feed (100) injected into the reaction zone (80) is greater than or equal to 3 wt / wt, preferably between 3 wt / wt and 10 wt / wt, more preferably between 4 wt / wt and 7 wt / wt.Indeed, one of the characteristics of the liquid solvent (760) is that it contains an aromatics content exceeding 30% by weight relative to the total weight of said liquid solvent (760), enabling it to effectively dissolve the solid feed (100) and efficiently reduce the viscosity of the reaction medium in the reaction zone (80). Another advantage of the process according to the invention is that the use of such a solvent allows it to remain in liquid form while limiting the pressure in the reactors to a level below 1.5 MPa. The precise optimization of the composition of the liquid solvent (760), the ratio of liquid solvent (760) to solid feed (100), and the reactor pressure also makes it possible to target a carbon black concentration in the reactor outlet effluent, allowing for proper management of this flow and the conditions suitable for carbon black separation.

[0078] Indeed, the proportion of said hydrocarbon cut (730) to constitute the liquid solvent (760) is also adjusted in order to optimize the steps downstream of the reaction zone (80), namely:

[0079] - a solid content at the centrifugation inlet advantageously between 5 and 20% dry solid weight, the optimal operating range for this step;

[0080] - the desired drying temperature downstream of centrifugation. It was discovered that the quantity of the hydrocarbon fraction (730) has a significant impact on the drying temperature required to achieve low residual moisture in the recovered carbon black. Indeed, the centrifuged carbon black cake (420) contains interstitial fluid that must be removed by evaporation during the drying step (e). This interstitial fluid to be evaporated consists of the hydrocarbon fraction (730) as well as the heavy fraction (740) resulting from the conversion of the solid feedstock (100). The flux of the light hydrocarbon fraction (720) present in the liquid solvent (760) is vaporized in the reaction zone (80).Since the drying process aims to remove all of the hydrocarbon fraction (730) and a large portion of the heavy fraction (740), the greater the quantity of hydrocarbon fraction (730) relative to the heavy fraction (740), the lower the drying temperature. This is due to the reduction in partial pressures, which facilitates the evaporation of the heavy fraction (740), thus limiting the vacuum drying temperature (<350°C). Limiting the drying temperature is crucial for operability and metallurgical considerations. The formulation of the liquid solvent (760) is the result of careful optimization to ensure optimal dissolution and reaction conditions, guaranteeing the maximization of valuable products and the proper operating conditions for the centrifugation and drying steps.

[0081] The mass ratio between said hydrocarbon cut (730) and liquid solvent (760) is between 0.2 and 0.95 weight / weight, preferably between 0.4 and 0.9 weight / weight, and preferably between 0.5 and 0.8 weight / weight.

[0082] During plant start-up, in the absence of production of a stabilized intermediate cut, i.e., the hydrocarbon cut (730), it is possible to temporarily use an imported solvent which will preferably consist of an aromatic molecule content greater than 40% by weight relative to the total weight of the cut. This cut could therefore consist, for example, of conversion effluents from the FCC (Fluid Catalytic Cracking) process, middle distillate (LCO or "light cycle oil" according to Anglo-Saxon terminology), or heavy distillate (HCO or "heavy cycle oil" according to Anglo-Saxon terminology), for example.

[0083] Step e)

[0084] The centrifuged carbon black cake (420) obtained at the end of step b) is sent to a conduction drying zone (50) to obtain the recovered carbon black (520) and said second gaseous effluent (510).

[0085] Drying is carried out under vacuum, which allows the heating temperature to be lowered. The drying pressure is between 0.0001 MPa and 0.01 MPa, preferably between 0.0002 MPa and 0.005 MPa, more preferably between 0.0002 MPa and 0.001 MPa.

[0086] The drying temperature is between 150°C and 350°C, preferably between 200°C and 320°C, more preferably between 220°C and 300°C.

[0087] At the end of the drying step e), the content of volatile organic compounds in the recovered carbon black (520) measured by thermogravimetric analysis known as TGA, is less than 10% by weight, preferably less than 5% by weight, and preferably less than 3% by weight relative to the total mass of recovered carbon black (520).

[0088] The residence time of the centrifuged carbon black cake is adjusted to achieve this target volatile organic compound (VOC) content. The drying time is between 1 and 8 hours, preferably between 2 and 7 hours, and more preferably between 3 and 6 hours. Drying is carried out by conduction. In conductive drying, heat is transferred to the centrifuged carbon black cake by contact with a wall heated by a fluid. Indeed, given the fineness of the particles, convective drying carries too many particles into the gas stream. Conduction drying, on the other hand, allows for efficient particle recovery. To characterize this recovery of solid particles, the diameter of the particles is generally defined. 97 such as the particle diameter below which 97% of the particles by volume are found. After drying, the diameter of 97is less than 60 pm, preferably less than 20 pm, and preferably less than 10 pm.

[0089] According to the invention, the centrifuged carbon black cake is agitated during conduction drying in order to renew the solid in contact with the heated wall.

[0090] The rotation speed of the agitator is between 2 revolutions / min and 150 revolutions / min, preferably between 5 revolutions / min and 100 revolutions / min, more preferably between 10 revolutions / min and 80 revolutions / min.

[0091] A person skilled in the art will choose the conductive dryer technology best suited to carbon black. While not exhaustive, examples include externally heated rotary tube dryers, paddle dryers, and cylinder dryers.

[0092] In order to be incorporated into an elastomer matrix for recycled elastomers, the recovered carbon black (520) can optionally be sent to a crusher, in particular a jet crusher (not shown in Figure 1).

[0093] The second gaseous effluent (510) from the drying stage is sent to the fractionation zone (70).

[0094] Step e'): (optional) additional drying step.

[0095] If the target volatile organic compound (VOC) content in the recovered carbon black (520) is not met, it can undergo a further drying step (e'). This final drying can be carried out using various dryer technologies, including an atmospheric pressure fluidized bed dryer where the solid particles are kept in suspension at high temperature. Unlike the first dryer in step e), which is fed with a more or less compact cake of wet solid, the second dryer is fed with dry-looking carbon black powder that can be easily suspended. Recovered carbon black

[0096] The recovered carbon black (520) at the end of steps a) to e), consists of carbon black (CB), inorganic ash, and carbon residues from the decomposition of tire rubbers and / or elastomeric residues associated with said tire rubbers, characterized in that said carbon residue content, determined with respect to the percentage area of ​​peak Ci measured by X-ray photoelectron spectroscopy, is less than or equal to 1% of said area of ​​peak Ci, preferably between 0.001% area and 0.08% area, more preferably between 0.001% area and 0.07% area, and even more preferably between 0.001% area and 0.05% area, said percentage area of ​​peak Ci being calculated with respect to the total area of ​​peaks Co to Cs.

[0097] More specifically, the recovered carbon black (520) comprises between 50% by weight and 98% by weight of carbon element relative to the total weight of said recovered carbon black, preferably between 60% by weight and 90% by weight, and even more preferably between 65% by weight and 85% by weight.

[0098] More specifically, the recovered carbon black (520) comprises between 0.2% by weight and 4% by weight of oxygen element relative to the total weight of the recovered carbon black, preferably between 0.4% by weight and 3% by weight, and even more preferably between 0.8% by weight and 2.7% by weight.

[0099] More specifically, the recovered carbon black (520) comprises between 0.2 wt% and 3 wt% of hydrogen element relative to the total weight of the recovered carbon black, preferably between 0.4 wt% and 2.5 wt%, and even more preferably between 0.5 wt% and 1.5 wt%.

[0100] More specifically, the recovered carbon black (520) comprises between 0.05 wt% and 1 wt% of nitrogen element relative to the total weight of the recovered carbon black, preferably between 0.1 wt% and 0.7 wt%, and even more preferably between 0.15 wt% and 0.4 wt%.

[0101] More specifically, the recovered carbon black (520) comprises between 0.5% by weight and 6% by weight of sulfur element per total weight of the recovered carbon black, preferably between 1.5% by weight and 5% by weight, and even more preferably between 2% by weight and 3.5% by weight.

[0102] The carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) contents were measured by CHNS-O elemental analysis. The recovered carbon black (520) obtained from steps a) to e) also contains inorganic ash. The inorganic ash consists of at least the atomic element Si, predominantly present in its oxidized form SiC2 (silica), and at least the element zinc, predominantly present in its oxidized form ZnO (zinc oxide) and / or its sulfide form ZnS (zinc sulfide), preferably in its sulfide form ZnS. The application of a specific heat treatment (at least 950°C in air, as determined by TGA analysis) allows the inorganic ash content present in the recovered carbon black according to the invention to be quantified.Thus, the inorganic ash content is advantageously between 4% by weight and 50% by weight relative to the total weight of the recovered carbon black, preferably between 8% by weight and 40% by weight, and even more preferably between 10% by weight and 30% by weight.

[0103] Advantageously, the recovered carbon black (520) according to the invention comprises a specific surface area, determined by nitrogen physisorption, of between 30 m 2 / g and 150 m 2 / g, preferably between 50 m 2 / g and 90 m 2 / g and even more preferably between 50 m 2 / g and 75 m 2 / g.

[0104] Advantageously, the structure index, determined by the OAN analytical method in accordance with ASTM D2414, is between 55 m 3 / kg and 110.10' 5 m 3 / kg, preferably between 55 m 3 / kg and 90.10 -5 m 3 / kg.

[0105] Examples

[0106] The method used to illustrate the invention conforms to that described in Figure 1.

[0107] In these examples, the spent elastomer feedstock consists of 100% used tires. Used tire granules (solid feedstock (100)), produced by granulators using crushers, are used. These granules come from heavy-duty tires, and the resulting granules are approximately 2 millimeters in size. The tire granules (100) originate from a pretreatment unit (10) and are free of textile and metallic fibers. The granules (100) are then continuously fed into a dissolution and conversion reactor (80) where they are mixed with the liquid solvent from the hydrocarbon fraction (730) recycled from the fractionation zone (70). A portion of the hydrocarbon fractions (720) and (730), the compositions of which are shown in Table 1 below, serves as the liquid solvent (760) described below. The mass ratio of solvent (760) / granule (100) is equal to 5 wt / wt.In reactor (80), the temperature is maintained at 385°C, which allows the aggregates (100) to dissolve. The residence time in reactor (80) is 2 hours. The pressure in the dissolution reactor is 0.9 MPa. At the outlet of reactor (30), a first liquid effluent (320) and a gaseous effluent (310) are collected, the latter being sent entirely to the fractionation zone (70).

[0108] The composition of hydrocarbon cuts (720), (730) are given in Table 1 below.

[0109] Table 1

[0110] The dry solids content in the first liquid effluent (320) is 10% by weight relative to the total weight of the liquid effluent (320). The average size of the carbon black particles in the first liquid effluent (320), measured by Mastersize 3000 laser particle size analysis in liquid-stream ultrasonics, is between 0.5 µm and 30 µm.

[0111] In Examples 1 to 6 below, laboratory tests were performed to separate the liquid / solid fraction of the first liquid effluent (320) and then to dry the carbon black obtained after the liquid / solid separation. The fraction (760) is obtained by mixing a portion of fractions (720) and (730), with a mass ratio (730) / (760) of 0.7.

[0112] In example 7, cut (760) is obtained after mixing a part of cuts (720) and (730), with a mass ratio (730) / (760) of 0.3. in accordance with the i

[0113] Without a prior liquid / solid separation step, a portion of the liquid effluent (320), composed of 10% dry solids and 90% liquid to be evaporated, is directly dried by conduction in a double-jacketed agitated tank at a speed of 33 rpm at 260°C under a vacuum of 0.0005 MPa. To achieve a volatile organic compound (VOC) content in the recovered carbon black (520), measured by thermogravimetric analysis (TGA), of less than 2% by weight of VOCs in the recovered carbon black (520), the required drying time is 9 hours. Frontal filtration, ratio

[0114] In example 2, frontal filtration tests were carried out with filter cloths on a portion of the first liquid effluent (320) recovered from the solvolysis outlet. The surface area of ​​the filter cloth is 56 cm². 2Different filter media (PEEK (polyetheretherketone) and Porostar® metal mesh) and different filtration pressures up to 0.5 MPa were tested. For all tests performed with frontal filtration, either the filtrate flow rate was almost zero or clearly too low to extrapolate to an industrial scale (the media being clogged by solids), or all the carbon black passed through the overly open media, preventing liquid / solid separation.

[0115] The samples were not dried. at 500G, ratio

[0116] A portion of the liquid effluent (320) is centrifuged at 500G in a Sorvall 6 RC Plus laboratory centrifuge (rotor F14S-6*250Y) at 20 °C for 5 min. After centrifugation, a second liquid effluent (410) and a centrifuged carbon black cake (420) are obtained.

[0117] The liquid / solid separation is not satisfactory, the liquid (410) is not free of solid, which represents a significant loss of carbon black.

[0118] The cake was not dried. Example 4: Liquid / solid separation of liquid effluent (320) by centrifugation at 2000G, mass ratio (730) / (760) of 0.7, conductive drying (according to the invention)

[0119] A portion of the liquid effluent (320) is centrifuged at 2000G in a Sorvall 6 RC Plus laboratory centrifuge (rotor F14S-6*250Y) at 20°C for 5 min. After centrifugation, a second liquid effluent (410) and a centrifuged carbon black cake (420) are obtained. 62% by weight of the total liquid of the effluent (320) is removed by centrifugation.

[0120] The centrifuged carbon black cake (420) of Example 4 consists of 23% by weight of dry solid and 77% by weight of liquid to be evaporated. This cake is then dried by conduction in a double-jacketed stirred tank at a stirring speed of 33 rpm at 260°C under a vacuum of 0.0005 MPa.

[0121] To achieve a VOC content in the recovered carbon black (520) measured by thermogravimetric analysis known as TGA of less than 2% by weight of VOC in the recovered carbon black (520), the drying time required is 6 hours.

[0122] Example 5: Liquid / solid separation of liquid effluent (320) by centrifugation at 7500G, mass ratio (730) / (760) of 0.7, conductive drying (according to the invention)

[0123] A portion of the liquid effluent (320) is centrifuged at 7500 g in a Sorvall 6 RC Plus laboratory centrifuge (rotor F14S-6*250Y) at 20 °C for 5 min. After centrifugation, a second liquid effluent (410) and a centrifuged carbon black cake (420) are obtained. 72% by weight of the total liquid in the effluent (320) is removed by centrifugation. The quality of the liquid / solid separation is therefore significantly improved compared to examples 2 and 3.

[0124] The centrifuged carbon black cake (420) in Example 5 consists of 28% dry solid by weight and 72% liquid by weight to be evaporated. This cake is then dried by conduction in a double-jacketed stirred tank at a stirring speed of 33 rpm at 260°C under a vacuum of 0.0005 MPa. To achieve a VOC content in the recovered carbon black (520), measured by thermogravimetric analysis (TGA), of less than 2% by weight of VOCs in the recovered carbon black (520), the required drying time is 5 hours.

[0125] Example 6: Liquid / solid separation of liquid effluent (320) by centrifugation at 7500G, mass ratio (730) / (760) of 0.7, convective drying (not in accordance with the invention)

[0126] A portion of the liquid effluent (320) is centrifuged at 7500G in a Sorvall 6 RC Plus laboratory centrifuge (rotor F14S-6*250Y) at 20 °C for 5 min. After centrifugation, a second liquid effluent (410) and a centrifuged carbon black cake (420) are obtained (similar to Example 5).

[0127] The centrifuged carbon black cake (420) in Example 6 consists of 28% dry solid by weight and 72% liquid by weight to be evaporated. This cake is then dried by convection in a vacuum vessel (0.0005 MPa absolute) that is neither agitated nor heated by the walls: only nitrogen heated to 260°C (10 NL^ / h / g dry solid) injected at the bottom of the vessel enables drying. Without mechanical agitation of the wet solid, agglomerates of solid form, with dry crusts around them, leaving the core moist. To make the mixture more homogeneous and improve drying, a higher gas flow rate would be necessary. Since the heat supplied by the gas is significantly less than the heat that can be supplied by conduction (heating through the walls), an excessively high gas flow rate would be required to improve drying, which would generate excessive drag, difficult to manage on an industrial scale.Nine hours of drying is insufficient to achieve the target VOC content of 2% by weight of VOCs in the recovered carbon black (520) (non-homogeneous mixture). This scenario is therefore not considered.

[0128] Only Examples 4 and 5, which combine liquid / solid separation by centrifugation under the conditions of the invention with conductive drying under the same conditions, allow for the recovery of dried carbon black with good recovery efficiency under low-energy conditions. Example 1, which does not use liquid / solid separation upstream of the drying step, yields dried carbon black but under very energy-intensive conditions, requiring more than 9 hours of drying. Example 2, which uses frontal filtration, did not allow for the recovery of a carbon black cake; therefore, drying was not possible. Example 3, which uses centrifugation but with a G-number not in accordance with the invention, did not allow for the proper separation of the carbon black particles in the suspension. Consequently, drying was not achieved.Example 6 using convective drying did not allow the cake to dry homogeneously even after a long drying time at a gas flow rate avoiding the entrainment of particles.

[0129] Example 7: Liquid / solid separation of liquid effluent (320) by centrifugation at 7500G, mass ratio (730) / (760) of 0.3, conductive drying (according to the invention)

[0130] In Example 7, section (760) is obtained by mixing a portion of sections (720) and (730), with a mass ratio (730) / (760) of 0.3 (same conditions as in Example 5 except for the mass ratio (730) / (760)). The centrifuged carbon black cake (420) from Example 7 consists of 28% by weight of dry solid and 72% by weight of liquid to be evaporated. This cake is then dried by conduction in a double-jacketed stirred tank at a stirring speed of 33 rpm under a vacuum of 0.0005 MPa. To achieve a VOC content in the recovered carbon black (520) measured by thermogravimetric analysis known as TGA of less than 2% by weight of VOC in the recovered carbon black (520), the drying time required is 5 hours but the drying temperature required is 315°C (instead of 260°C as in example 5).

[0131] The main results of liquid / solid separation and drying are summarized in Table 2.

[0132] Table 2

Claims

DEMANDS 1. A process for converting spent elastomers by solvolysis to obtain recovered carbon black (520), said process comprising at least the following steps: a) a solid feed (100) of spent elastomers is sent into a reaction zone (80) in the presence of a liquid solvent (760) comprising aromatic compounds to dissolve at least part of said solid feed and thermally decompose said at least partially dissolved solid feed at a temperature below 400°C and at a pressure below 1.5 MPa in order to obtain a first gaseous effluent (310) and a first liquid effluent (320) comprising the carbon black, the mass ratio between the liquid solvent (760) and the solid feed (100) being greater than 3 weight / weight;b) the first liquid effluent (320) obtained in step a) is sent into a centrifugation zone (40) at a centrifugal force between 1000 G and 16000 G for a period between 30 seconds and 30 minutes in order to obtain a centrifuged carbon black cake (420) and a second liquid effluent (410); (c) at least part of said first gaseous effluent (310) obtained at the end of step (a), at least part of a second gaseous effluent (510) obtained at the end of step (e) and at least part of the second liquid effluent (410) obtained at the end of step (b) are sent to a fractionation zone (70) to obtain at least one light hydrocarbon cut (720) having a final boiling point between 250°C and 325°C and at least one hydrocarbon cut (730) comprising an aromatic compound content exceeding 30% by weight relative to the total weight of said hydrocarbon cut (730), and further comprising; - a hydrocarbon compound content of less than 20% by weight relative to the total weight of the hydrocarbon fraction; and - a C40+ hydrocarbon content of less than 5% by weight relative to the total weight of said hydrocarbon cut; d) at least a portion of said light hydrocarbon cut (720) and at least a portion of said hydrocarbon cut (730) obtained at the end of step c) are sent into the reaction zone (80) as liquid solvent (760) of step a), characterized in that the mass ratio between said hydrocarbon cut (730) and liquid solvent (760) is between 0.2 and 0.95 weight / weight; e) the centrifuged carbon black cake (420) obtained at the end of step b) is dried in a conduction drying zone (50) at a temperature between 150°C and 350°C, a vacuum pressure between 0.0001 MPa and 0.01 MPa absolute, under agitation between 2 rpm and 150 rpm for a period between 1 hour and 8 hours to obtain the recovered carbon black (520) and said second gaseous effluent (510).

2. A process according to claim 1, wherein the mass ratio between said hydrocarbon cut (730) and the liquid solvent (760) is between 0.4 and 0.9 weight / weight.

3. A method according to any one of claims 1 or 2, wherein the centrifugal force of step b) is between 2000 G and 8000 G.

4. A method according to any one of the preceding claims, wherein the centrifugation time of step b) is between 1 minute and 20 minutes.

5. A process according to any one of the preceding claims, wherein the volatile organic compound content in the recovered carbon black (520) obtained at the end of step e), measured by thermogravimetric analysis known as TGA, is less than 10% by weight of volatile organic compounds in said recovered carbon black (520).

6. A process according to any one of the preceding claims, wherein the second liquid effluent (410) obtained at the end of step b) consists of at least 40% by weight of the first liquid effluent (320).

7. A method according to any one of the preceding claims, wherein the agitation speed in the conduction drying zone of step e) is between 5 rpm and 100 rpm.

8. A method according to any one of the preceding claims, wherein the agitation speed in the conduction drying zone of step e) is between 10 rpm and 80 rpm.

9. A method according to any one of the preceding claims, wherein the drying step e) is carried out at a pressure under absolute vacuum of between 0.0002 MPa and 0.005 MPa.

10. A method according to any one of the preceding claims, wherein the drying step e) is carried out at a temperature between 200°C and 320°C.

11. A method according to any one of the preceding claims, wherein the duration of step e) of drying is between 2 hours and 7 hours.

12. A method according to any one of the preceding claims, wherein the duration of step e) of drying is between 3 hours and 6 hours.

13. A method according to any one of the preceding claims, wherein step a) comprises the following substeps: a1) said solid feed (100) and said liquid solvent (760) are sent into a first stirred reactor (20) to dissolve at least part of said solid feed (100); a2) said solid feed, at least partially dissolved, obtained at the end of step a1) is sent into a second stirred reactor (30) to thermally decompose said solid feed at a temperature less than or equal to 400°C and obtain a liquid effluent containing suspended carbon black particles.

14. A process according to any one of the preceding claims, wherein the aromatic compound content of the hydrocarbon fraction (730) is greater than 40% by weight relative to the total weight of said fraction.

15. A process according to any one of the preceding claims, wherein the solid feedstock (100) is based on used tires.

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