Solvolysis process for tires with recycling of aromatic hydrocarbon fractions

Abstract

The present invention relates to a process for converting worn tires to obtain carbon black, the process comprising the following steps: a) passing a solid filling of worn tires in the presence of a liquid solvent to a reaction zone to obtain a vapor effluent and a first liquid effluent comprising carbon black; b) passing the liquid effluent to a filtration and washing unit to obtain a filtered and washed carbon black cake and a second liquid effluent; c) passing the vapor effluent and the second liquid effluent to a fractionation zone to obtain at least one hydrocarbon fraction; d) passing the hydrocarbon fraction obtained at the end of step c) to the reaction zone as liquid solvent for use in step a); and e) drying the carbon black cake.

Description

[Technical Field]

[0001] The present invention relates to a method for converting used tires by pyrolysis. [Background technology]

[0002] Methods for converting used tires by pyrolysis generally aim to produce gaseous, liquid, and solid fractions. The tires are typically first comminuted, resulting in either comminuted tire material (typically 1-10 cm pieces) that still contains portions of the textile fibers or metal wires contained within the tire, or granules (typically less than 6 mm in size) that do not contain the textile fibers or metal wires. By exposing these prepared feedstocks to heat, it is possible to cause a reaction in the feedstock that decomposes the used tires and recover the gaseous, liquid, and solid fractions. Successful tire decomposition typically requires exposing the tires to fairly high temperatures, typically between 300°C and 900°C, for reaction times ranging from 30 minutes to several hours.

[0003] Numerous techniques exist for carrying out these reactions. For example, tires may be subjected to high temperatures in rotary kilns (Non-Patent Document 1) or in moving bed furnaces (Patent Document 1). These techniques are robust, but generally require operation at very high temperatures, typically above 500°C on average. In these processes, carbon black, which is typically present in the feedstock at a rate of 25-40% by weight and is essentially composed of very fine submicrometer or micrometer particles / agglomerates, tends to agglomerate in the presence of degraded rubber, which forms coke that bonds these structures at various scales. The solids often exit the reactor in the form of blocks of several millimeters / centimeters. They then need to be finely ground to be recycled as carbon black, which requires considerable energy expenditure. In these processes, the temperature conditions are high, and essentially gaseous and solid fractions are found in the reactor. The liquid produced then comes from the condensation of gaseous products downstream of the reactor. These high temperature conditions tend to further promote polycondensation and coking reactions, leading to the formation of polyaromatic structures (Non-Patent Document 2), or coke, through cyclization reactions involving the aromatic and olefinic structures present. The higher the temperature, the higher the content of polyaromatic structures and coke formed. While aromatic molecules are, first, good solvents and, second, find numerous uses, particularly as petrochemical base stocks, polyaromatic structures impair the quality of the liquids formed and are very difficult to purify or convert. Furthermore, they are coke precursors. Therefore, there is considerable interest in minimizing polycondensation reactions to produce minimal polyaromatic structures while preserving the monoaromatic structures present.

[0004] To improve the quality of the solid phase and limit the formation of coke on the carbon black, it is possible to reduce the hydrocarbon partial pressure by injecting steam during the cracking reaction. Nevertheless, cracking under essentially gas-solid conditions requires high temperatures exceeding 500°C (Patent Document 2). These gas-solid methods generally lead to the production of gases that are non-condensable under atmospheric conditions, and their production rate is very high, ranging from 10% to 25% by weight relative to the tire feedstock entering the reactor. However, upgrading of the reaction gases is locally complicated. These gases are therefore typically used to generate the heat required to carry out the reaction, but this is done at the expense of the amount of easily upgradeable liquid products, which is then limited. These liquid fractions, in particular, are subsequently upgraded to produce new hydrocarbon fractions (naphtha, gasoline, kerosene, gas oil, vacuum distillate, and residual oil). These hydrocarbon fractions are used in refineries to produce fuels or in petrochemicals to produce base materials that are subsequently used for the production of plastics. Nevertheless, these fractions need to be purified to the desired specifications, and the higher the number of polyaromatic structures, the more complex the purification becomes.

[0005] One alternative route consists of contacting the tire feedstock with a liquid and raising the temperature of this liquid to dissolve and convert the tires into a homogeneous liquid phase. In this homogeneous liquid phase, the tire feedstock is stirred and gradually disappears. Examples of this implementation are described in U.S. Patent Nos. 5,629,999 and 5,729,999. This type of process allows the recovery of the carbon black in the liquid phase after filtration, without agglomeration of the carbon black particles or the deposition of coke on the surface of these particles, as occurs in reactions operated in the gas-solid phase. Operating at temperatures below 450°C further limits the polycondensation reaction of aromatics, the formation of coke on the surface of the carbon black particles, and the formation of gases (typically 1% to 7% by weight of the incoming feedstock). The use of a solvent containing an aromatics fraction, preferentially a monoaromatic fraction, is advantageous, allowing for better dissolution of the feedstock in the reactor. Since tires originally consist of various rubbers, including a large amount of synthetic rubber consisting of styrene-butadiene rubber (SBR), the resulting liquid fraction contains a large amount of aromatic compounds. It may be advantageous to separate and recycle part of the liquid formed during the reaction and use it as a solvent, while the non-recycled liquid fraction may be sent to a refinery for purification and then upgraded as a hydrocarbon fraction and sent to a product pool or petrochemicals. For example, in Patent Document 3, the heavy fraction of the filtrate obtained after distillation, which contains aromatic compounds, is heated and then recycled to the reactor as a liquid solvent. However, depending on the composition of the heavy fraction used to dissolve the solid feedstock and also on the recycle ratio of the heavy fraction relative to the solid feedstock, the filtration time of carbon black can vary considerably. The applicant has developed a new method for converting used tires, which makes it possible to avoid the above-mentioned drawbacks by optimizing the existing method as described in Patent Document 3. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 2661475 [Patent Document 2] US Patent Application Publication No. 2016 / 0083657 [Patent Document 3] U.S. Patent No. 3,978,199 [Patent Document 4] U.S. Patent No. 3,704,108 [Non-patent literature]

[0007] [Non-Patent Document 1] Lewandowski et al., Journal of Analytical and Applied Pyrolysis, 2019, Vol. 140, pp. 25-53 [Non-patent document 2] MF Laresgoiti, BM Caballero, I. de Marco, A. Torres, MA Cabrero, MJ Chomon, "J. Anal. Appl. Pyrolysis", 2004, Vol. 71, p.917-934 Summary of the Invention [Means for solving the problem]

[0008] (Subject of the Invention) One subject of the present invention is a method for converting used tires to obtain carbon black, which method comprises at least the following steps: a) passing a solid feedstock based on used tires to a reaction zone in the presence of a liquid solvent containing aromatic compounds, wherein the solid feedstock is at least partially dissolved, and pyrolyzing the at least partially dissolved solid feedstock at a temperature of not more than 425°C and a pressure of less than 1.5 MPa to obtain a gaseous effluent and a first liquid effluent containing carbon black, wherein the weight ratio between the liquid solvent and the solid feedstock is greater than 3 wt / wt; b) passing the first liquid effluent obtained in step a) to a filtration and washing zone in the presence of a washing solvent to obtain a filtered and washed carbon black case and a second liquid effluent; c) sending at least a portion of the gaseous effluent obtained at the end of step a) and at least a portion of the second liquid effluent obtained at the end of step b) to a fractionation zone to obtain at least one hydrocarbon fraction, the at least one hydrocarbon fraction having an aromatics content of more than 30% by weight relative to the total weight of the hydrocarbon fraction, and further comprising: - the content of C5-C10 hydrocarbon compounds is less than 20% by weight, relative to the total weight of the hydrocarbon fraction; and - the content of C40+ hydrocarbon compounds is less than 5% by weight, relative to the total weight of said hydrocarbon fraction; process; d) passing at least a portion of said hydrocarbon fraction obtained at the end of step c) into the reaction zone as liquid solvent for step a); e) Drying the filtered and washed carbon black cake obtained at the end of step b) at a temperature between 50°C and 200°C to recover the carbon black.

[0009] Surprisingly, applicant has discovered that the use of a recycled hydrocarbon fraction as a liquid solvent in the used tire conversion zone, which is rich in aromatic compounds, low in C40+ compounds (vacuum resid), not too high in C5-C10 hydrocarbon compounds (gasoline), and has a specific solvent / solid feed weight ratio, synergistically allows for better dissolution and cracking of the solid feed, thus maximizing carbon black production.

[0010] In one embodiment according to the invention, before step a) of the method, the solid feedstock is sent to a pre-treatment unit to at least partially remove textile fibers and metal wires contained in the solid feedstock.

[0011] In one embodiment according to the present invention, step a) comprises the following substeps: a1) passing the solid feedstock and the liquid solvent into a first stirred reactor to at least partially dissolve the solid feedstock; and a2) passing the at least partially dissolved solid feedstock obtained at the end of sub-step a1) into a second stirred reactor whereby the solid feedstock is pyrolyzed at a temperature of not more than 425°C to obtain a first liquid effluent containing carbon black particles in suspension.

[0012] In one embodiment according to the invention, the content of aromatic compounds in the hydrocarbon fraction is more than 40% by weight relative to the total weight of said fraction.

[0013] In one embodiment according to the invention, the content of C5-C10 hydrocarbon compounds in the hydrocarbon fraction is less than 10% by weight relative to the total weight of said fraction.

[0014] In one embodiment according to the invention, the content of C40+ hydrocarbon compounds in the hydrocarbon fraction is less than 3% by weight relative to the total weight of said fraction.

[0015] In one embodiment according to the invention, the weight ratio between the liquid solvent and the solid feedstock is greater than 3 wt / wt.

[0016] In one embodiment according to the invention, the viscosity of the second liquid effluent at 100° C. is less than 10 cP, measured according to standard ASTM D3236.

[0017] In one embodiment according to the invention, in step c) of the process, a light fraction is also obtained, the end point of which is preferentially between 250°C and 325°C.

[0018] In one embodiment according to the invention, the light ends are at least partially sent upstream to a distillation column to obtain at least one light end, the end point of which is below 200°C.

[0019] In one embodiment according to the invention, the light fraction having an end point of 200° C. or less is sent at least in part to a filtration / washing zone as wash solvent according to step b) of the process.

[0020] In one embodiment according to the present invention, step b) comprises the following substeps: b1) filtering the liquid effluent in a washing and filtering device to obtain a filtered carbon black cake and a liquid fraction; b2) washing the filtered carbon black cake obtained at the end of sub-step b1) in the presence of a wash solvent to obtain a filtered and washed carbon black cake and a wash stream.

[0021] Preferably, the wash stream is sent to an intermediate fractionation unit to obtain a fraction that is at least partially recycled as wash solvent upstream of the washing and filtering device.

[0022] Advantageously, the hydrocarbon fraction has a content of C10-C20 hydrocarbon compounds ranging from 20% to 65% by weight relative to the total weight of the hydrocarbon fraction.

[0023] Advantageously, the hydrocarbon fraction has a content of C20-C40 hydrocarbon compounds ranging from 30% to 80% by weight relative to the total weight of the hydrocarbon fraction.

[0024] Advantageously, the hydrocarbon fraction has an initial boiling point of 50°C to 325°C and an end point of 350°C to 520°C. DETAILED DESCRIPTION OF THE INVENTION

[0025] (List of drawings) FIG. 1 is a schematic diagram of the method according to the invention.

[0026] FIG. 2 is a schematic representation of the process shown in FIG. 1, showing the reaction zone and filtration and washing zone of the process in more detail.

[0027] (Detailed explanation) A Cn hydrocarbon fraction is understood to mean a fraction containing hydrocarbons with n carbon atoms.

[0028] Cn+ fraction is understood to mean the fraction containing hydrocarbons with at least n carbon atoms.

[0029] Referring to FIG. 1 , which illustrates an embodiment according to the present invention, a method for converting used tires includes at least the following steps: a) passing a solid feedstock (100) based on used tires into a reaction zone (80) in the presence of a liquid solvent (760) comprising aromatic compounds, to at least partially dissolve said solid feedstock, and pyrolyzing said at least partially dissolved solid feedstock at a temperature of up to 425°C, preferably between 375°C and 425°C, and at a pressure of less than 1.5 MPa, preferably between 0.5 and 1.2 MPa, to obtain a gaseous effluent (310) and a first liquid effluent (320) comprising carbon black, wherein the weight ratio between the liquid solvent (760) and the solid feedstock (100) is greater than 3 wt / wt; b) passing the liquid effluent (320) obtained in step a) to a filtration and washing zone (40) in the presence of a washing solvent to obtain a filtered and washed carbon black cake (430) and a second liquid effluent (410); c) sending at least partly, preferably entirely, said gaseous effluent (310) obtained at the end of step a) and at least partly, preferably entirely, the second liquid effluent (410) obtained at the end of step b) to a fractionation zone (70) to obtain at least one hydrocarbon fraction (730), the at least one hydrocarbon fraction (730) having a content of aromatic compounds of more than 30% by weight, preferably more than 40% by weight, relative to the total weight of said hydrocarbon fraction; - the content of C5-C10 hydrocarbon compounds is less than 20% by weight, preferably less than 10% by weight, and more preferentially between 1% and 8% by weight, relative to the total weight of the hydrocarbon fraction (730); and - the content of C40+ hydrocarbon compounds is less than 5% by weight, preferably less than 3% by weight, more preferentially less than 1% by weight, and even more preferentially less than 0.5% by weight, relative to the total weight of said hydrocarbon fraction (730); d) sending, at least in part, the hydrocarbon fraction (730) obtained at the end of step c) to the reaction zone (80) as liquid solvent (760) of step a); e) drying the filtered and washed carbon black cake (430) obtained at the end of step b) at a temperature between 50°C and 200°C, preferably for a time sufficient to achieve a content of washing solvent in the dried cake of less than 0.5% by weight relative to the total weight of said dried cake; advantageously, the drying time is between 10 minutes and 36 hours, more preferentially between 1 hour and 15 hours, to recover the carbon black (520).

[0030] The solid feedstock (100) used in the context of the present invention is advantageously based on tires obtained from the processing of used tires. Used tires may come from any source, for example, from light vehicles (LV) or heavy goods vehicles (HGV). The solid feedstock may advantageously be in the form of tire granules, i.e., particles with a size of less than 6 mm. Preferably, the solid feedstock (100) is substantially free of textile fibers and metal wires and / or comminuted tire material, i.e., comminuted tire fragments, with a characteristic size generally between 1 cm and 20 cm. Therefore, according to a preferred embodiment of the present invention, the solid feedstock (100) is sent to a pre-treatment unit (10), which removes the textile fibers and metal wires (110) from the solid feedstock (100). Such pre-treatment units are well known to those skilled in the art and may consist of various types of crushers (ie rotary shears, shredders, granulators, re-chippers), magnetic separators or else vibrating screens, separation tables.

[0031] According to step a) of the conversion process, the rubber contained in the solid feedstock (100) is brought into contact with a liquid solvent (760), whereby it dissolves and is then pyrolyzed. The source and composition of the liquid solvent (760) will be described in detail below. Step a) is preferably carried out at a temperature of up to 425°C, preferably between 375°C and 425°C, and at a pressure of less than 1.5 MPa, preferably between 0.8 MPa and 1.2 MPa. At the end of step a), at least one gaseous effluent (310) is obtained, as well as a first liquid effluent (320) containing carbon black and, optionally, solids (210) contained in the 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.

[0032] The first liquid effluent (320) containing carbon black is then sent to a filtration and washing zone (40) (i.e., step b) of the preparation method according to the invention) to recover a filtered and washed carbon black cake (430) and a second liquid effluent (410). In one embodiment according to the invention, the viscosity of the second liquid effluent (410), measured at 100°C, is less than 10 cP, preferentially less than 5 cP, more preferentially less than 3 cP, measured according to standard ASTM D3236.

[0033] The filtration and washing unit may comprise any device allowing the filtration of the carbon black particles contained in the first liquid effluent (320). Such a device may, for example, be in the form of a rotary filter, preferentially operating at a temperature between 50°C and 200°C. During step b), the carbon black cake is washed with a washing solvent.

[0034] In one embodiment according to the present invention, the washing solvent used during step b) is a solvent (800) external to the process, as shown in Figure 1. Such a solvent may be, for example, toluene.

[0035] In another embodiment according to the invention, the wash solvent used during step b) consists at least in part of the light fraction (720) obtained at the end of step c). More specifically, referring to FIG. 2, a portion of the light fraction (720) can be sent to the distillation column (90) through line (725). A complementary portion (735) of the light fraction is sent out of the process according to the invention as an upgradeable product. At the outlet of the distillation column (90), a light fraction (910) containing aromatic compounds is obtained, the end point of which is below 200° C., preferably below 150° C., and which can be used at least in part as a wash solvent for the filtration / washing zone (40). The heavier fraction (920) can be sent out of the process as an upgradeable product (920).

[0036] The filtered and washed carbon black cake (430) is sent to a drying unit (50) operating at a temperature between 50°C and 200°C, preferably between 50°C and 150°C, to recover the carbon black (520) (i.e., step e) of the process according to the invention). Advantageously, the vapor effluent (510) from the drying unit (50) containing the wash solvent is recycled to the washing / filtration unit (40).

[0037] According to an essential feature of the conversion process according to the invention, the gaseous effluent (310) obtained at the end of step a) and the second liquid effluent (410) obtained at the end of step b) are sent to a fractionation unit (70) (i.e. step c) of the process according to the invention) to give at least one hydrocarbon fraction (730), which has a content of aromatic compounds greater than 30% by weight relative to the total weight of said hydrocarbon fraction (730) and which further comprises at least: - a content of C5-C10 hydrocarbon compounds of less than 20% by weight, preferably less than 10% by weight, and more preferentially between 1% and 8% by weight, relative to the total weight of the hydrocarbon fraction (730); and a content of C40+ hydrocarbon compounds of less than 5% by weight, preferably less than 3% by weight, more preferentially less than 1% by weight, and even more preferentially less than 0.5% by weight, relative to the total weight of said hydrocarbon fraction (730).

[0038] Advantageously, the hydrocarbon fraction (730) also has a content of C10-C20 hydrocarbon compounds of between 20% and 65% by weight, preferably between 30% and 65% by weight, and even more preferentially between 45% and 65% by weight, relative to the total weight of the hydrocarbon fraction.

[0039] Advantageously, the hydrocarbon fraction (730) also has a content of C20-C40 hydrocarbon compounds of between 30% and 80% by weight, preferably between 30% and 70% by weight, and even more preferentially between 30% and 55% by weight, relative to the total weight of the hydrocarbon fraction.

[0040] Advantageously, the hydrocarbon fraction (730) has an initial boiling point of 50°C to 325°C, preferably 50°C to 250°C, and an end point of 350°C to 520°C, preferably 350°C to 450°C.

[0041] In particular, the Applicant has observed that the use of a recycled hydrocarbon fraction as liquid solvent (760) in the reaction zone (80) (i.e., step d) of the process according to the invention), which has a rich content of aromatic compounds, a low content of C40+ compounds (vacuum residue), and a not too high content of C5-C10 hydrocarbon compounds (gasoline), with a solvent / solid feed weight ratio of more than 3 wt / wt, preferably between 3 and 10 wt / wt, and more preferentially between 4 and 7 wt / wt, synergistically allows a better dissolution and decomposition of the solid feed (100), thus maximizing the production of carbon black, which, among other things, leads to a shorter filtration time of the carbon black in the washing / filtration zone (40).

[0042] Advantageously, the fractionation zone (70) also makes it possible to obtain non-condensable gases (710), a light fraction (720) and a heavy fraction (740). The end point of the light fraction (720) is preferentially between 250°C and 325°C, while the initial boiling point of the heavy fraction (740) is preferentially between 350°C and 450°C. Advantageously, the light fraction (720) can be sent, at least in part, as a wash solvent to the washing and filtration zone (40) to obtain a filtered and washed carbon black cake (430).

[0043] Advantageously, the light fraction (720) has a content of C10-hydrocarbon compounds of more than 60% by weight relative to the total weight of the light fraction (720).

[0044] Advantageously, the heavy fraction (740) has a content of C40+ hydrocarbon compounds of more than 60% by weight relative to the total weight of the heavy fraction (740).

[0045] According to the invention, a portion of the hydrocarbon fraction (730) is sent, at least in part, as liquid solvent (760) to the reaction zone (80) of step a), while the other portion (750) is advantageously sent externally to the process according to the invention as an upgradeable product. The weight ratio between the liquid solvent (760) and the solid feed stream (100) injected into the reaction zone (80) is greater than 3 weight / weight (w / w), preferably between 3 and 10 weight / weight, and more preferentially between 4 and 7 weight / weight. In particular, one of the characteristics of the liquid solvent (760) is that it contains aromatic compounds in a content of more than 30% by weight relative to the total weight of said liquid solvent (760), which makes it possible to effectively dissolve the solid feedstock (100) and to effectively 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 the solvent to remain in liquid form, while limiting the pressure in the reactor to a level below 1.5 MPa. This is true considering the limited production of gas and light hydrocarbons in the reaction zone (80) and the low content of C10-hydrocarbon compounds in the hydrocarbon fraction (730).

[0046] To better understand the invention, the following application example is described, which describes a method for converting used tires, which allows maximizing the recovery of carbon black. Referring to FIG. 2, a solid feedstock (100) is sent to a pre-treatment unit (10), which removes textile fibers and metal wires (110) from the solid feedstock (100). The solid feedstock, substantially free of textile fibers and metal wires, is then sent to a reaction zone (80). The reaction zone (80) allows the pyrolysis of used tires and includes a first stirred reactor (20) fed with a liquid solvent (760). The first stirred reactor (20) is intended to promote the dissolution of tire granules or crushed material contained in the solid feedstock (100). The liquid solvent / solid feedstock weight ratio is greater than 3 wt / wt, preferably between 3 and 10 wt / wt, and more preferentially between 4 and 7 wt / wt. The temperature in the reactor (20) is preferentially between 200°C and 300°C, preferentially between 250°C and 290°C. In the first stirred reactor (20), the crushed material or granules dissolve. The time required for this dissolution is preferentially between 30 minutes and 2 hours. The rubber debris and the carbon black gradually released from the rubber remain in suspension by mechanical or hydrodynamic agitation, for example, induced by the upward flow of liquid resulting from forced convection recirculation, or by any other means for keeping the medium agitated. Any undissolved metal wires that may still be present in the solid feedstock settle and exit the first stirred reactor (20) at its bottom via line (210). Under these conditions, the temperature is too low for significant carbon-carbon decomposition reactions to occur, so that only the cross-links between polymers, for example, the SS bonds associated with rubber vulcanization, can be substantially decomposed. The resulting liquid fraction (220), containing the remaining suspended solids, is sent to the second stirred reactor (30). In the second stirred reactor (30), the pyrolysis reaction is carried out under moderate temperature conditions, i.e. at a temperature of up to 425°C, preferably between 375°C and 425°C, for a limited time (corresponding to the residence time of the liquid fraction in the reactor (30)), preferentially between 30 minutes and 2 hours, preferentially between 45 minutes and 90 minutes.The amount of heat required to carry out the pyrolysis reaction may be supplied by a heat exchanger located on a pumparound (not shown) around the second stirred reactor (30) or by any other means, such as an exchanger on the wall of the reactor or an exchanger or furnace on the feedstock upstream of the reactor. Agitation is maintained in the second stirred reactor (30) by a mechanical stirring system or a pumparound system or by any other means known to those skilled in the art. Preferentially, the pressure in the reactor is maintained at a level below 1.5 MPa by a control valve (not shown).

[0047] At the end of the reaction in the second stirred reactor (30), a first liquid effluent (320) containing carbon black particles in suspension and a gaseous effluent (310) are obtained. The first liquid effluent (320) is then sent to a filtration and washing zone (40), which includes a rotary filter (41) and an intermediate fractionation unit (42) (see FIG. 2). The rotary filter (41) is preferably operated at a temperature between 50°C and 200°C, allowing for the production of a carbon black cake and a liquid fraction (425). The carbon black cake is then washed with a washing solvent (800), such as toluene, preferably at a temperature between 50°C and 100°C, allowing for the recovery of filtered and washed carbon black (430). After the filtration / washing step, the wash stream (405) is sent to the intermediate fractionation unit (42) to obtain a fraction (610) and a fraction (415). The distillate (610) can be at least partially recycled via a line upstream of the rotary filter (41) as additional wash solvent, and the distillate (415) can be sent together with the liquid fraction (425) as a second liquid effluent (410) to the fractionation zone (70). The filtered and washed carbon black (430) is then sent to a drying unit (50), which is advantageously operated at a temperature between 50°C and 200°C for a time sufficient to ensure that the content of wash solvent in the dried carbon black is less than 0.5% by weight, relative to the total weight of the dried cake. The filtered, washed, and dried carbon black (520) is then advantageously pelletized with water to form pellets of a few millimeters, for example, to facilitate the transportation and upgrading of the carbon black. The carbon black thus produced can be reused as a reinforcing agent in the elastomer industry or for other applications, for example as a pigment in inks, plastics or paints, after subsequent material processing and packaging steps depending on its use and application. The residual washing solvent can be recovered at the outlet of the drying unit (50) and at least partially recovered via line (510).

[0048] The gaseous effluent (310) leaving the reaction zone (80) via the second reactor (30) and the second liquid effluent (410) from the washing / filtration zone (40) are then sent to a fractionation zone (70), which may consist of a heat exchanger, a gas-liquid separator drum, a distillation column containing a top take-off, a bottom take-off and a side take-off, or an arrangement of several distillation columns, for example an atmospherically operated distillation column with a top take-off and a bottom take-off, followed by a distillation column operated under low vacuum. This fractionation zone (70) makes it possible in particular to obtain a hydrocarbon fraction (730) comprising a content of aromatics of more than 30% by weight, preferentially more than 40% by weight, relative to the total weight of said hydrocarbon fraction (730), and further comprising: - the content of C5-C10 hydrocarbon compounds is less than 20% by weight, preferably less than 10% by weight, and more preferentially between 1% and 8% by weight, relative to the total weight of the hydrocarbon fraction (730); and - the content of C40+ hydrocarbon compounds is less than 5% by weight, preferably less than 3% by weight, more preferentially less than 1% by weight, and even more preferentially less than 0.5% by weight, relative to the total weight of said hydrocarbon fraction (730); At least a portion of the hydrocarbon fraction (730) can be recycled to the reaction zone (80) as liquid solvent (760), and another portion (750) can be upgraded as a product. Preferably, the hydrocarbon fraction is sent to the first reactor (20) of the reaction zone (80) as liquid solvent.

[0049] This fractionation zone (70) also makes it possible to obtain non-condensable gases (710), a light fraction (720) having an end point preferentially between 250° C. and 325° C., and a heavy fraction (740) having an initial boiling point preferentially between 350° C. and 450° C. Advantageously, the light fraction (720) is sent, at least in part, as washing solvent to the washing and filtering device (41) of the washing and filtering zone (40) to obtain a filtered and washed carbon black cake (430).

[0050] During the start-up of the plant, it is possible to temporarily use the imported solvent without producing a stable middle distillate, i.e., hydrocarbon fraction (730), which will be predominantly composed of aromatic molecules with a content of more than 40% by weight relative to the total weight of the fraction; this fraction may thus be composed, for example, of the conversion effluent from a fluid catalytic cracking (FCC) process of middle distillates (light cycle oil (LCO)) or heavy distillates (heavy cycle oil (HCO)).

[0051] (Example) The following examples illustrate preferred embodiments of the method according to the present invention, but do not limit the scope of the invention. The method used to illustrate the present invention corresponds to that shown in FIG.

[0052] In a first example, according to the present invention, used tire granules (solid feedstock) are used, produced by a granulator using a grinder, originating from tires of heavy-duty vehicles. The coarse particles obtained from the grinding have a size close to 2 millimeters. The tire granules originate from the pre-treatment unit (10) and are free of textile and metal fibers. The granules are then continuously sent to a dissolution reactor, where they are mixed with a liquid solvent resulting from the recycling of the hydrocarbon fraction (730) from the fractionation zone (70). A portion of the hydrocarbon fraction (730) is used as liquid solvent (760), the composition of which is shown in Table 1 below. The amount of solid feedstock treated is 100 kg / h. The amount of solvent recycled to the reactor (20) is 500 kg / h, which corresponds to a solvent / granule weight ratio equal to 5 w / w. In the reactor (20), the temperature is maintained equal to 290°C, which allows the granules to dissolve. The liquid fraction and the carbon black in suspension are then sent to a reactor (30), where the temperature is maintained equal to 400°C for 1 hour. At the outlet of the reactor (30), a first liquid effluent (320) and a gaseous effluent (310) are recovered, the gaseous effluent (310) being sent in its entirety to a fractionation zone (70). The first liquid effluent (320) is sent to a rotary filter (41) operated at 140°C. The filtered carbon black is washed with toluene. The second liquid effluent (410) collected at the outlet of the washing and filtering zone (40) is sent in its entirety to the fractionation zone (70). The filtered and washed carbon black (430) is sent to a drying unit (50), which is operated at 150°C for 24 hours, and the filtered, washed and dried carbon black (520) is recovered.

[0053] In Examples 2 to 5 not in accordance with the present invention, the steps and operating conditions of the conversion process are the same as those of Example 1, except for the following features: Examples 2 and 3: the content of C40+ hydrocarbon compounds (vacuum residues (VR)) in the liquid solvent (760) is outside the range according to the invention; Example 4: the content of C5-C10 hydrocarbon compounds (gasoline) in the hydrocarbon fraction (760) is outside the range according to the invention; Example 5: The solvent / solid feed weight ratio is outside the range according to the invention.

[0054] [Table 1]

[0055] Comparing the results for the carbon black filtration time with those for Example 1 according to the invention, it is found that when the content of C40+ hydrocarbon compounds (vacuum residuum) in the hydrocarbon fraction (730) is 8% by weight relative to the total weight of said fraction (Example 2), the carbon black filtration time is more than four times longer, and even more than eight times longer when the content of C40+ hydrocarbon compounds is 20% by weight (Example 3). Furthermore, when the content of C5-C10 hydrocarbon compounds (gasoline) in the hydrocarbon fraction (730) is 26% by weight, the carbon black filtration time is more than four times longer (Example 4). Finally, a non-optimized liquid solvent (760) / solid feedstock (100) weight ratio leads to a significantly longer carbon black filtration time (Example 5). [Brief explanation of the drawings]

[0056] [Figure 1] 1 is a schematic diagram of a method according to the present invention; [Figure 2] 2 is a diagrammatic representation of the process shown in FIG. 1, showing the reaction zone and filtration and washing zone of the process in more detail.

Claims

1. 1. A method for converting used tires to obtain carbon black, comprising at least the following steps: a) passing a solid feedstock (100) based on used tires to a reaction zone (80) in the presence of a liquid solvent (760) comprising aromatic compounds, to at least partially dissolve said solid feedstock, and pyrolyzing said at least partially dissolved solid feedstock at a temperature of less than or equal to 425°C and a pressure of less than 1.5 MPa to obtain a gaseous effluent (310) and a first liquid effluent (320) comprising carbon black, wherein the weight ratio between the liquid solvent (760) and the solid feedstock (100) is greater than 3 wt / wt; b) passing the first liquid effluent (320) obtained in step a) to a filtration and washing zone (40) in the presence of a washing solvent to obtain a filtered and washed carbon black cake (430) and a second liquid effluent (410); c) sending at least a portion of said gaseous effluent (310) obtained at the end of step a) and at least a portion of the second liquid effluent (410) obtained at the end of step b) to a fractionation zone (70) to obtain at least one hydrocarbon fraction (730), the at least one hydrocarbon fraction (730) having a content of aromatic compounds greater than 30% by weight relative to the total weight of said hydrocarbon fraction, and further comprising: the content of C5-C10 hydrocarbon compounds is less than 20% by weight, relative to the total weight of the hydrocarbon fraction; and - the content of C40+ hydrocarbon compounds is less than 5% by weight relative to the total weight of said hydrocarbon fraction; d) sending at least a portion of said hydrocarbon fraction (730) obtained at the end of step c) to the reaction zone (80) as liquid solvent (760) of step a); and e) drying the filtered and washed carbon black cake (430) obtained at the end of step b) at a temperature between 50°C and 200°C to recover the carbon black.

2. 2. The method of claim 1, wherein, prior to step a), the solid feedstock (100) is sent to a pre-treatment unit (10) to at least partially remove textile fibers and metal wires contained in the solid feedstock (100).

3. Step a) comprises the following substeps: a1) passing said solid feedstock (100) and said liquid solvent (760) into a first stirred reactor (20) to at least partially dissolve said solid feedstock (100); and a2) feeding the at least partially dissolved solid feedstock obtained at the end of substep a1) into a second stirred reactor (30) in which the solid feedstock is pyrolyzed at a temperature of up to 425°C and a liquid effluent containing suspended carbon black particles is obtained.

3. The method of claim 1 or 2, comprising:

4. 4. The method according to claim 1, wherein the content of aromatic compounds in the hydrocarbon fraction (730) is greater than 40% by weight relative to the total weight of said fraction.

5. 5. The process according to claim 1, wherein the content of C5-C10 hydrocarbon compounds in the hydrocarbon fraction (730) is less than 10% by weight relative to the total weight of said fraction.

6. 6. The method according to any one of claims 1 to 5, wherein the content of C40+ hydrocarbon compounds in the hydrocarbon fraction (730) is less than 3 wt. % relative to the total weight of said fraction.

7. The method according to any one of claims 1 to 6, wherein the viscosity of the second liquid effluent (410) at 100°C is less than 10 cP, measured according to standard ASTM D3236.

8. 8. The process according to any one of claims 1 to 7, wherein in step c) a light fraction (720) is also obtained, the end point of which is preferentially between 250°C and 325°C.

9. 9. The process of claim 8, wherein the light ends (720) are at least partially passed upstream to a distillation column (90) to obtain at least one light end (910), the end point of which is 200° C. or less.

10. 10. The process according to claim 9, wherein the light fraction (910) having an end point of 200°C or less is sent to a filtration / washing zone (40) at least in part as a wash solvent according to step b) of the process.

11. Step b) comprises the following substeps: b1) filtering the liquid effluent (320) in a washing and filtering device (41) to obtain a filtered carbon black cake and liquid fraction (425); and b2) washing the filtered carbon black cake obtained at the end of sub-step b1) in the presence of a wash solvent to obtain a filtered and washed carbon black cake (430) and a wash stream (405). The method according to any one of claims 1 to 10, comprising:

12. 12. The method according to claim 11, wherein the wash stream (405) is sent to an intermediate fractionation unit (42) to obtain a fraction (610) which is at least partially recycled as wash solvent upstream of the washing and filtering device (41).

13. 13. The method according to any one of claims 1 to 12, wherein the hydrocarbon fraction (730) has a content of C10-C20 hydrocarbon compounds of from 20% to 65% by weight relative to the total weight of the hydrocarbon fraction.

14. 14. The method according to any one of claims 1 to 13, wherein the hydrocarbon fraction (730) has a content of C20-C40 hydrocarbon compounds of from 30% to 80% by weight relative to the total weight of the hydrocarbon fraction.

15. The method according to any one of claims 1 to 14, wherein the hydrocarbon fraction (730) has an initial boiling point of 50°C to 325°C and an end boiling point of 350°C to 520°C.

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