Method for solvolysis of tires by recycling the hydrocarbon fraction containing aromatic compounds

Abstract

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

Description

Field of the Invention

[0001] The present invention relates to a method for converting used tires by thermal decomposition. Existing technology

[0002] The process for converting used tires by thermal decomposition generally involves the production of gaseous, liquid, and solid fractions. The tires are typically initially ground to obtain a ground tire material that still contains a portion of the textile fibers or metal wires contained in the tire (typically in fragments of 1 to 10 cm), or particles (typically less than 6 mm in size) that are free of textile fibers or metal wires. These raw materials, thus prepared by exposing them to heat, can be reacted to decompose the used tires and recover the gaseous, liquid, and solid fractions. For successful tire decomposition, it is generally necessary to expose the tires to relatively high temperatures, typically 300°C to 900°C, for reaction times ranging from 30 minutes to several hours.

[0003] There are many technologies for carrying out these reactions. For example, tires can be subjected to high temperatures in a rotary furnace (Lewandowski et al., Journal of Analytical and Applied Pyrolysis, 140, 2019, 25-53), or in a moving bed (EP2661475). These technologies are robust, but generally need to work at quite high temperatures, typically with an average temperature above 500 ° C. In these methods, carbon black is generally present in the raw material in a ratio of 25% by weight to 40% by weight, and is initially composed of very fine submicron or micron particles / agglomerates. In the presence of decomposed rubber, carbon black tends to agglomerate, thereby forming coke with these structures under various scales, and solids generally leave the reactor in the form of blocks of several millimeters / cm, and then need to be finely ground so that this solid is reused as carbon black, which requires a large amount of energy consumption. In these methods, temperature conditions are high, and basic gaseous and solid fractions are found in the reactor. The liquid prepared is then produced by the condensation of gaseous products downstream of the reactor. Furthermore, these high temperatures tend to promote polycondensation and coking reactions, with the formation of polycyclic aromatic structures or coke, through cyclization reactions involving the existing aromatic and olefinic structures (MF Laresgoiti, BM Caballero, I. de Marco, A. Torres, M.A. Cabrero, M.J. Chomón. J. Anal. Appl. Pyrolysis 71 (2004) 917-934). The higher the temperature, the higher the content of polycyclic aromatic structures and coke formed. Although aromatic molecules are firstly good solvents and secondly have a large number of applications, especially as petrochemical bases, polycyclic aromatic structures are, on the other hand, detrimental to the quality of the liquids formed and are difficult to purify or convert. Furthermore, they are coke precursors. Therefore, there is great interest in minimizing polycondensation reactions in order to produce a minimum of polycyclic aromatic structures while retaining the existing monoaromatic structures.

[0004] In order to improve the quality of the solid phase and limit the formation of coke on the carbon black, the partial pressure of the hydrocarbons can be reduced by injecting steam during the cracking reaction, but the cracking reaction requires a high temperature of more than 500 ° C to crack under basic gas-solid conditions (US2016 / 0083657). These gas-solid methods generally result in the production of non-condensable gases under atmospheric conditions, and their yield is very high and is 10% to 25% by weight relative to the tire raw material entering the reactor. However, the upgrading of the reaction gases is locally complicated. Therefore, these gases are generally used to generate the heat required for the reaction, but the cost of doing so is that the amount of liquid products that can be easily upgraded is thereby limited. Specifically, these liquid fractions are then optionally upgraded to produce new hydrocarbon fractions (naphtha, gasoline, kerosene, gas oil, vacuum distillates, residues) for refineries to produce fuels or for petrochemicals to produce basic components for subsequent plastic production. However, it is necessary to refine these fractions to bring them to the required specifications. The more polycyclic aromatic structures there are, the more complex the refining.

[0005] An alternative method involves contacting the tire feedstock with a liquid, raising the temperature of the liquid, and dissolving and converting the tire into a homogeneous liquid phase in which the tire feedstock is stirred and gradually disappears. Examples of such embodiments are given in US3978199 and US3704108. This type of process makes it possible to recover the carbon black in the liquid phase after filtration, without the particles undergoing agglomeration or deposition of coke at their surfaces, as is the case in reactions operating in the gas-solid phase. In addition, embodiments at temperatures below 450°C limit the polycondensation of aromatic compounds, the formation of coke at the surface of the carbon black particles, and the formation of gas, which is typically 1% to 7% by weight of the entering feedstock. The use of a solvent containing an aromatic fraction, preferably a monoaromatic fraction, is advantageous and enables the raw materials to be better dissolved in the reactor. Since tires naturally contain various rubbers, including a large amount of synthetic rubber consisting of styrene-butadiene rubber (SBR), the liquid fraction produced contains a large amount of aromatic compounds, and it is advantageous to separate and recycle a portion of the liquid formed during the reaction to use it as a solvent, and the liquid fraction that is not recycled can be sent to an oil refinery for refining, and thus upgraded to a hydrocarbon fraction for feeding product pools and petrochemicals. For example, in document US 3,978,199, the heavy fraction of the filtrate containing aromatic compounds obtained after distillation is heated and then recycled to the reactor as a liquid solvent. However, depending on the composition of the heavy fraction for dissolving the solid raw material, and the recycle ratio of the heavy fraction relative to the solid raw material, the filtration time of carbon black can be significantly different. Applicants have developed a new method for converting old tires that makes it possible to prevent the above-mentioned defects by optimizing the existing method described in document US 3,978,199.

[0006] Subject matter of the invention

[0007] A subject of the present invention is a process for converting used tires to obtain carbon black, comprising at least the following steps:

[0008] a) feeding a solid feedstock based on used tires to a reaction zone in the presence of a liquid solvent comprising an aromatic compound to at least partially dissolve the solid feedstock and thermally decomposing the at least partially dissolved solid feedstock at a temperature lower than or equal to 425° C. and a pressure lower than 1.5 MPa to obtain a gaseous effluent and a first liquid effluent comprising carbon black, wherein the weight ratio between the liquid solvent and the solid feedstock is greater than 3 weight / weight;

[0009] 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 cake and a second liquid effluent;

[0010] c) sending at least part of said gaseous effluent obtained at the end of step a) and at least part of the second liquid effluent obtained at the end of step b) to a fractionation zone in order to obtain at least one hydrocarbon fraction having an aromatics content greater than 30% by weight relative to the total weight of said hydrocarbon fraction and further having:

[0011] a content of C5-C10 hydrocarbon compounds of less than 20% by weight relative to the total weight of said hydrocarbon fraction; and

[0012] a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon fraction;

[0013] d) sending at least part of the hydrocarbon fraction obtained at the end of step c) to the reaction zone as liquid solvent for step a);

[0014] e) drying the filtered and washed carbon black cake obtained at the end of step b) at a temperature of 50° C. to 200° C. to recover the carbon black.

[0015] Surprisingly, the Applicant has found that the use of such a recycled hydrocarbon fraction, which contains a high content of aromatic compounds, a low content of C40+ compounds (vacuum residue) and a less high content of C5-C10 hydrocarbon compounds (gasoline), as a liquid solvent in the used tire conversion zone synergistically allows for a better solubilization and decomposition of the solid feedstock at a specific solvent / solid feedstock weight ratio, thereby maximizing the production of carbon black.

[0016] In one embodiment according to the present invention, prior to step a) of the method, the solid raw material is sent to a pre-treatment unit in order to at least partially remove textile fibers and metal filaments contained in the solid raw material.

[0017] In one embodiment according to the present invention, step a) comprises the following sub-steps:

[0018] a1) sending the solid feedstock and the liquid solvent to a first stirred reactor to at least partially dissolve the solid feedstock;

[0019] a2) sending the at least partially dissolved solid feedstock obtained at the end of step a1) to a second stirred reactor for thermal decomposition of the solid feedstock at a temperature lower than or equal to 425° C. and obtaining a first liquid effluent containing suspended carbon black particles.

[0020] In one embodiment according to the present invention, the content of aromatic compounds in the hydrocarbon fraction is greater than 40% by weight relative to the total weight of the fraction.

[0021] In one embodiment according to the present invention, the content of C5-C10 hydrocarbon compounds in the hydrocarbon fraction is less than 10% by weight relative to the total weight of the fraction.

[0022] In one embodiment according to the present invention, the content of C40+ hydrocarbon compounds in the hydrocarbon fraction is less than 3% by weight relative to the total weight of the fraction.

[0023] In one embodiment according to the present invention, the weight ratio between the liquid solvent and the solid raw material is greater than 3 weight / weight.

[0024] In one embodiment according to the present invention, the viscosity of the second liquid effluent at 100° C. is less than 10 cP, measured according to standard ASTM D3236.

[0025] In one embodiment of the present invention, in step c) of the method, a light fraction is also obtained, and the final boiling point of the light fraction is preferably 250°C to 325°C.

[0026] In one embodiment according to the present invention, the light fraction is at least partially sent to an upstream distillation column to obtain at least one light fraction, the final boiling point of the at least one light fraction being lower than or equal to 200°C.

[0027] In one embodiment according to the invention, the light fraction having a final boiling point lower than or equal to 200° C. is at least partially sent to the filtration / washing zone as washing solvent according to step b) of the process.

[0028] In one embodiment according to the present invention, step b) comprises the following sub-steps:

[0029] b1) filtering the liquid effluent in a washing and filtering unit to obtain a filtered carbon black cake and a liquid fraction;

[0030] b2) washing the filtered carbon black filter cake obtained at the end of step b1) in the presence of a washing solvent to obtain a filtered and washed carbon black filter cake and a washing stream.

[0031] Preferably, the wash stream is sent to an intermediate fractionation unit to obtain a fraction which is at least partly recycled upstream of the washing and filtration device as wash solvent.

[0032] Advantageously, said hydrocarbon fraction has a content of C10-C20 hydrocarbon compounds ranging from 20% to 65% by weight relative to the total weight of said hydrocarbon fraction.

[0033] Advantageously, said hydrocarbon fraction has a content of C20-C40 hydrocarbon compounds ranging from 30% to 80% by weight relative to the total weight of said hydrocarbon fraction.

[0034] Advantageously, the hydrocarbon fraction has an initial boiling point of 50°C to 325°C and an end boiling point of 350°C to 520°C.

[0035] List of Figures

[0036] Figure 1 is a schematic diagram of the method according to the present invention.

[0037] Figure 2 yes Figure 1 Schematic diagram of the process shown in , showing the reaction zone as well as the filtration and washing zones of the process in more detail.

[0038] Detailed description

[0039] A Cn hydrocarbon fraction is understood to mean a fraction which comprises hydrocarbons having n carbon atoms.

[0040] A Cn+ fraction is understood to mean a fraction comprising hydrocarbons having at least n carbon atoms.

[0041] refer to Figure 1 , indicating that according to an embodiment of the present invention, the method for converting old tires comprises at least the following steps:

[0042] a) sending a solid feedstock 100 based on used tires to a reaction zone 80 in the presence of a liquid solvent 760 comprising an aromatic compound to at least partially dissolve the solid feedstock and thermally decompose the at least partially dissolved solid feedstock at a temperature lower than or equal to 425° C., preferably from 375° C. to 425° C., and at a pressure lower than 1.5 MPa, preferably from 0.5 MPa to 1.2 MPa, to obtain a gaseous effluent 310 and a first liquid effluent 320 comprising carbon black, the weight ratio between the liquid solvent 760 and the solid feedstock 100 being greater than 3 weight / weight;

[0043] b) sending 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;

[0044] c) sending at least part, preferably all, of said gaseous effluent 310 obtained at the end of step a) and at least part, preferably all, of the second liquid effluent 410 obtained at the end of step b) to a fractionation zone 70 in order to obtain at least one hydrocarbon fraction 730 having an aromatics content greater than 30% by weight, preferably greater than 40% by weight, relative to the total weight of said hydrocarbon fraction, and having:

[0045] - a content of C5-C10 hydrocarbon compounds of less than 20% by weight, preferably less than 20% by weight, more preferably from 1% to 8% by weight, relative to the total weight of the hydrocarbon fraction 730; and

[0046] a content of C40+ hydrocarbon compounds of less than 5% by weight, preferably less than 3% by weight, more preferably less than 1% by weight and even more preferably less than 0.5% by weight relative to the total weight of said hydrocarbon fraction 730;

[0047] d) sending at least part of the hydrocarbon fraction 730 obtained at the end of step c) to the reaction zone 80 as liquid solvent 760 for step a);

[0048] e) drying the filtered and washed carbon black cake 430 obtained at the end of step b) at a temperature of 50° C. to 200° C., preferably for a time sufficient to obtain a washing solvent content in the dried cake of less than 0.5% by weight relative to the weight of the dried cake. Advantageously, the drying time is from 10 minutes to 36 hours, more preferably from 1 hour to 15 hours, in order to recover the carbon black 520.

[0049] The solid raw material 100 used in the context of the present invention is advantageously based on the tire produced by the processing of old tires, and this old tire can be derived from any source, for example light vehicle (LV) or heavy goods vehicle (HGV).Described solid raw material can advantageously be in the form of tire particles, i.e. the form of particles having a size less than 6mm.Preferably, described solid raw material 100 is substantially free of textile fibers and wires, and / or grinding tire materials, i.e. grinding tire pieces, whose characteristic size is generally 1cm to 20cm.Therefore, according to a preferred embodiment of the present invention, solid raw material 100 is delivered to pre-treatment unit 10 so that from solid raw material 100, remove textile fibers and wires 110.This pre-treatment unit is well known to those skilled in the art and can include various types of grinders (i.e. rotary shears, pulverizers, granulators, re-grinding machines), magnetic separators or vibrating screens, separating tables.

[0050] According to step a) of the conversion process, the rubber contained in the solid raw material 100 is dissolved by contact with a liquid solvent 760 and then thermally decomposed. The source and composition of the liquid solvent 760 will be described in detail below. Step a) is preferably carried out at a temperature lower than or equal 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 and a first liquid effluent 320 containing carbon black are obtained, as well as solids 210, such as metal filaments or textile fibers, optionally contained in the used tires, which are released and separated from the liquid effluent 320 obtained at the end of this step.

[0051] 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 process according to the present invention) to recover a filtered and washed carbon black cake 430 and a second liquid effluent 410. In one embodiment according to the present invention, the viscosity of the second liquid effluent 410 measured at 100° C. is less than 10 cP, preferably less than 5 cP, more preferably less than 3 cP, as measured according to standard ASTM D3236.

[0052] The filtering and washing unit may comprise any device allowing filtering 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 preferably operated at a temperature of 50° C. to 200° C. During step b), the carbon black filter cake is washed with a washing solvent.

[0053] In one embodiment according to the invention, the washing solvent used during step b) is a solvent 800 external to the process, such as Figure 1 Such a solvent may be, for example, toluene.

[0054] In another embodiment according to the invention, the washing solvent used during step b) consists at least partly of the light fraction 720 obtained at the end of step c). More specifically, with reference to Figure 2 A portion of the light fraction 720 can be sent to a distillation column 90 via line 725. A sub-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, having an end boiling point of less than or equal to 200° C., preferably less than 150° C., which can be used at least in part as a washing solvent in the filtration / washing zone 40. The heavier fraction 920 can be sent out of the process as an upgradeable product 920.

[0055] The filtered and washed carbon black cake 430 is sent to a drying unit 50 operated at a temperature of 50° C. to 200° C., preferably 50° C. to 150° C., to recover the carbon black 520 (i.e., according to step e) of the process of the present invention). Advantageously, the vapor effluent 510 from the drying unit 50, which contains the washing solvent, is recycled to the washing / filtration unit 40.

[0056] 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. according to step c) of the process according to the invention) to prepare at least one hydrocarbon fraction 730 comprising an aromatics content greater than 30% by weight relative to the total weight of said hydrocarbon fraction 730 and further comprising at least:

[0057] - a content of C5-C10 hydrocarbon compounds of less than 20% by weight, preferably less than 10% by weight, more preferably from 1% to 8% by weight relative to the total weight of the hydrocarbon fraction 730; and

[0058] a content of C40+ hydrocarbon compounds of less than 5% by weight, preferably less than 3% by weight, more preferably less than 1% by weight and even more preferably less than 0.5% by weight relative to the total weight of said hydrocarbon fraction 730 .

[0059] Advantageously, the hydrocarbon fraction 730 also has a content of C10-C20 hydrocarbon compounds of 20% to 65% by weight, preferably of 30% to 65% by weight and even more preferably of 45% to 65% by weight relative to the total weight of the hydrocarbon fraction.

[0060] Advantageously, the hydrocarbon fraction 730 also has a content of C20-C40 hydrocarbon compounds of 30% to 80% by weight, preferably of 30% to 70% by weight and even more preferably of 30% to 55% by weight relative to the total weight of the hydrocarbon fraction.

[0061] Advantageously, the hydrocarbon fraction 730 has an initial boiling point of 50 to 325°C, preferably 50 to 250°C, and a final boiling point of 350 to 520°C, preferably 350 to 450°C.

[0062] In particular, the applicant has observed that the use of such a recycled hydrocarbon fraction (which has a high content of aromatic compounds, a low content of C40+ compounds (vacuum residue) and a less high content of C5-C10 hydrocarbon compounds (gasoline)) as the liquid solvent 760 for the reaction zone 80 (i.e., step d) of the process of the present invention) and the use of a solvent / solid feedstock weight ratio of greater than 3 w / w, preferably 3 w / w to 10 w / w, more preferably 4 w / w to 7 w / w, synergistically allows for better dissolution and decomposition of the solid feedstock 100, thereby maximizing the production of carbon black. This significantly results in shorter filtration times for the carbon black in the washing / filtration zone 40.

[0063] Advantageously, the fractionation zone 70 also makes it possible to obtain a non-condensable gas 710, a light fraction 720, and a heavy fraction 740. The final boiling point of the light fraction 720 is preferably between 250° C. and 325° C., and the initial boiling point of the heavy fraction 740 is preferably between 350° C. and 450° C. Advantageously, the light fraction 720 can be sent at least in part as a washing solvent to the washing and filtration zone 40 to obtain a filtered and washed carbon black filter cake 430.

[0064] Advantageously, the light fraction 720 has a content of C10-hydrocarbon compounds greater than 60% by weight relative to the total weight of the light fraction 720 .

[0065] Advantageously, the heavy fraction 740 has a content of C40+ hydrocarbon compounds greater than 60% by weight relative to the total weight of the heavy fraction 740 .

[0066] According to the present invention, a portion of hydrocarbon fraction 730 is at least partially fed to reaction zone 80 in step a) as liquid solvent 760, while another portion 750 is advantageously passed out of the process according to the present invention as an upgraded product. The weight ratio between the flow rate of liquid solvent 760 and the solid feedstock 100 injected into reaction zone 80 is greater than 3 weight / weight (w / w), preferably 3 w / w to 10 w / w, and more preferably 4 w / w to 7 w / w. Specifically, one of the characteristics of liquid solvent 760 is that it contains an aromatic compound content of greater than 30 wt.%, relative to the total weight of liquid solvent 760, which effectively dissolves solid feedstock 100 and effectively reduces the viscosity of the reaction medium in reaction zone 80. Another advantage of the process according to the present invention is that, given the limited production of gas and light hydrocarbons in reaction zone 80 and the low content of C10-hydrocarbon compounds in hydrocarbon fraction 730, the use of this solvent makes it possible to maintain the liquid form while limiting the pressure in the reactor to a level below 1.5 MPa.

[0067] For a better understanding of the present invention, the following description, given as an application example, relates to a method for converting old tires which makes it possible to maximize the recovery of carbon black. Figure 2 The solid feedstock 100 is fed to a pretreatment unit 10 to remove textile fibers and metal filaments 110 from the solid feedstock 100. The solid feedstock, substantially free of textile fibers and metal filaments, is then fed to a reaction zone 80 capable of thermally degrading used tires and comprising a first stirred reactor 20 fed with a liquid solvent 760 for the purpose of promoting the dissolution of the tire particles or abrasive material contained in the solid feedstock 100. The weight ratio of liquid solvent to solid feedstock is greater than 3 weight / weight, preferably from 3 weight / weight to 10 weight / weight, and more preferably from 4 weight / weight to 7 weight / weight. The temperature in reactor 20 is preferably from 200°C to 300°C, preferably from 250°C to 290°C. In the first stirred reactor 20, the abrasive material or particles are dissolved. The time required for this dissolution is preferably from 30 minutes to 2 hours. The rubber flakes and the carbon black gradually released from the rubber are kept in suspension by mechanical or hydrodynamic agitation, such as by upward flow of liquid caused by forced convection, or by any other means for maintaining agitation of the medium. The metal wire that may still be present in the solid raw material and has not yet dissolved settles and leaves the first stirred reactor 20 at its bottom via pipeline 210. Under these conditions, the temperature is too low for the carbon-carbon cracking reaction to start significantly, and only the crosslinking bonds between the polymers, such as the SS bonds associated with rubber vulcanization, can be significantly cracked. The liquid fraction 220 obtained, which contains the suspended residual solids, is sent to the second stirred reactor 30, where the thermal degradation reaction is carried out under moderate temperature conditions, i.e., at a temperature lower than or equal to 425°C, preferably at a temperature of 375°C to 425°C, and for a limited time (corresponding to the residence time of the liquid fraction in the reactor 30), preferably 30 minutes to 2 hours, preferably 45 minutes to 90 minutes. The heat required for the thermal degradation reaction can be provided by, for example, an exchanger on a pump circulation (not shown) located around the second stirred reactor 30, or by any other device, such as an exchanger on the reactor wall or an exchanger on the raw material upstream of the reactor or a heating furnace. Stirring is maintained in the second stirred reactor 30 by a mechanical stirring system, a pump circulation system, or any other means known to those skilled in the art. Preferably, the pressure of the reactor is maintained at a level lower than 1.5 MPa by a control valve (not shown in the figure).

[0068] At the end of the reaction in the second stirred reactor 30, a first liquid effluent 320 containing suspended carbon black particles and a gaseous effluent 310 are obtained. The first liquid effluent 320 is then sent to a filtration and washing section 40 comprising a rotary filter 41 and an intermediate fractionation unit 42 (see Figure 2 ). The rotary filter 41 is preferably operated at a temperature of 50° C. to 200° C. and makes it possible to obtain a carbon black filter cake and a liquid fraction 425. The carbon black filter cake is then washed with a washing solvent 800, such as toluene, preferably at a temperature of 50° C. to 100° C., making it possible to recover the filtered and washed carbon black 430. After the filtering / washing step, the washing stream 405 can be sent to an intermediate fractionation unit 42 to obtain a fraction 610, which can be at least partially recycled upstream of the rotary filter 41 as additional washing solvent via a pipeline, and a fraction 415, which 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 operated at a temperature of 50° C. to 200° C., advantageously for a time sufficient to achieve a washing solvent content in the dried cake of less than 0.5% by weight relative to the total weight of the dried cake. The filtered, washed, and dried carbon black 520 can then be granulated (pelletized) advantageously with water to form pellets, for example, of a few millimeters in size, to facilitate its transportation and quality improvement. The carbon black thus prepared can be reused as a reinforcing agent in the elastomer industry, or as a pigment for other applications, such as inks, plastics, or paints, after subsequent processing and packaging of the material depending on its use and application. Residual washing solvent can be recovered at the outlet of the drying unit 50 and can be at least partially recovered via line 510.

[0069] 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. The fractionation zone 70 may comprise a heat exchanger, a gas-liquid separator drum, a distillation column with a top take-off, a bottom take-off and a side take-off, or a series of several distillation columns, for example a series of distillation columns operated at atmospheric pressure with top take-off and bottom take-off, followed by a distillation column operated under low vacuum. This fractionation zone 70 makes it possible in particular to prepare a hydrocarbon fraction 730 comprising an aromatics content greater than 30% by weight, preferably greater than 40% by weight, relative to the total weight of said hydrocarbon fraction 730, and further comprising:

[0070] - a content of C5-C10 hydrocarbon compounds of less than 20% by weight, preferably less than 10% by weight, more preferably from 1% to 8% by weight relative to the total weight of the hydrocarbon fraction 730; and

[0071] a content of C40+ hydrocarbon compounds of less than 5% by weight, preferably less than 3% by weight, more preferably less than 1% by weight and even more preferably less than 0.5% by weight relative to the total weight of said hydrocarbon fraction 730;

[0072] At least a portion thereof can be recycled to the reaction zone 80 as liquid solvent 760, while another portion 750 can be upgraded to product. Preferably, the hydrocarbon fraction is fed to the first reactor 20 of the reaction zone 80 as liquid solvent.

[0073] The fractionation zone 70 also makes it possible to obtain a non-condensable gas 710, a light fraction 720, and a heavy fraction 740. The light fraction 720 preferably has a final boiling point of 250° C. to 325° C., and the heavy fraction 740 preferably has an initial boiling point of 350° C. to 450° C. Advantageously, the light fraction 720 can be sent at least in part as a washing solvent to the washing and filtering device 41 of the washing and filtering zone 40 to obtain a filtered and washed carbon black filter cake 430.

[0074] During the plant startup process, in the absence of a stable middle distillate, i.e., hydrocarbon fraction 730, an input solvent preferably consisting of an aromatic molecule content of greater than 40% by weight, relative to the total weight of the fraction, can be temporarily used. Thus, this fraction can consist, for example, of a conversion effluent from a fluid catalytic cracking (FCC) process, such as a middle distillate (light cycle oil (LCO)) or a heavy distillate (heavy cycle oil (HCO)). Example

[0075] The following examples illustrate preferred embodiments of the method according to the present invention, but do not limit its scope. Figure 2 The method described in is consistent.

[0076] In a first embodiment, according to the present invention, used tire particles (solid raw material) are used, which are derived from heavy truck tires and are prepared by a granulator using a grinder, and the particles produced by grinding have a size of approximately 2 mm. The tire particles are produced by the pretreatment unit 10 and do not contain textile fibers and metal fibers. The particles are then continuously sent to a dissolution reactor, where they are mixed with a liquid solvent produced by recycling 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 raw material processed is 100 kg / h. The amount of solvent recycled to the reactor 20 is 500 kg / h, corresponding to a solvent / particle weight ratio of 5 w / w. In the reactor 20, the temperature is maintained at 290°C, which allows the particles to dissolve. The liquid fraction and the suspended carbon black are then sent to the reactor 30, where a temperature of 400°C is maintained for one hour. At the outlet of the reactor 30, a first liquid effluent 320 and a gaseous effluent 310 are recovered, the latter being sent in their entirety to the 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 filtration 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 operated at 150°C for 24 hours to recover filtered, washed, and dried carbon black 520.

[0077] In Examples 2 to 5, which are not in accordance with the present invention, the steps and operating conditions of the conversion method are the same as those of Example 1, except for the following features:

[0078] - Examples 2 and 3: the content of C40+ hydrocarbon compounds (vacuum residue (VR)) in the liquid solvent 760 is outside the range according to the invention;

[0079] - Example 4: The content of C5-C10 hydrocarbon compounds (gasoline) in the hydrocarbon fraction 760 is outside the range according to the invention;

[0080] - Example 5: The solvent / solid starting material weight ratio is outside the range according to the invention.

[0081] Table 1

[0082]

[0083] Comparing the results of carbon black filtration time with those of Example 1 according to the present invention, it was found that when the content of C40+ hydrocarbon compounds (vacuum residue) in hydrocarbon fraction 730 was 8% by weight relative to the total weight of the fraction (Example 2), the carbon black filtration time was extended by a factor of four, and when the content of C40+ hydrocarbon compounds was 20% by weight, the carbon black filtration time was even extended by a factor of eight (Example 3). Furthermore, when the content of C5-C10 hydrocarbon compounds (gasoline) in hydrocarbon fraction 730 was 26% by weight, the carbon black filtration time was extended by a factor of four (Example 4). Finally, a non-optimized liquid solvent 760 / solid feedstock 100 weight ratio significantly extended the carbon black filtration time (Example 5).

Claims

1. A method for converting old tires to obtain carbon black, comprising at least the following steps: a) feeding a used tire based solid feedstock (100) to a reaction zone (80) in the presence of a liquid solvent (760) comprising an aromatic compound to at least partially dissolve the solid feedstock and thermally decompose the at least partially dissolved solid feedstock at a temperature lower than or equal to 425° C. and a pressure lower 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 weight / weight; b) sending 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 filter cake (430) and a second liquid effluent (410); c) sending at least part of said gaseous effluent (310) obtained at the end of step a) and at least part of said second liquid effluent (410) obtained at the end of step b) to a fractionation zone (70) in order to obtain at least one hydrocarbon fraction (730), said at least one hydrocarbon fraction (730) having an aromatics content greater than 30% by weight relative to the total weight of said hydrocarbon fraction and further having: a content of C5-C10 hydrocarbon compounds of less than 20% by weight relative to the total weight of said hydrocarbon fraction; and a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon fraction; d) sending at least part of the hydrocarbon fraction (730) obtained at the end of step c) to the reaction zone (80) as liquid solvent (760) for step a); e) drying the filtered and washed carbon black cake (430) obtained at the end of step b) at a temperature of 50°C to 200°C to recover the carbon black.

2. The method according to claim 1, wherein before step a), the solid raw material (100) is sent to a pretreatment unit (10) to at least partially remove textile fibers and metal wires contained in the solid raw material (100).

3. The method according to any one of claims 1 and 2, wherein step a) comprises the following sub-steps: a1) sending the solid raw material (100) and the liquid solvent (760) to a first stirred reactor (20) to at least partially dissolve the solid raw material (100); a2) sending the at least partially dissolved solid feedstock obtained at the end of step a1) to a second stirred reactor (30) to thermally decompose the solid feedstock at a temperature lower than or equal to 425°C and obtain a liquid effluent containing suspended carbon black particles.

4. The method according to any one of claims 1 and 2, wherein the content of aromatic compounds in the hydrocarbon fraction (730) is greater than 40% by weight relative to the total weight of the fraction.

5. The method according to any one of claims 1 and 2, 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 the fraction.

6. The method according to any one of claims 1 and 2, wherein the content of C40+ hydrocarbon compounds in the hydrocarbon fraction (730) is less than 3% by weight relative to the total weight of the fraction.

7. The method according to any one of claims 1 and 2, wherein the viscosity of the second liquid effluent (410) at 100°C is less than 10 cP, measured according to standard ASTM D3236.

8. The method according to any one of claims 1 and 2, wherein in step c), a light fraction (720) is further obtained, and the final boiling point of the light fraction (720) is 250°C to 325°C.

9. The method according to claim 8, wherein the light fraction (720) is at least partially sent upstream of a distillation column (90) to obtain at least one light fraction (910), the final boiling point of the light fraction (910) being lower than or equal to 200°C.

10. The method according to claim 9, wherein the light fraction (910) is at least partially sent to the filtration / washing zone (40) as a washing solvent according to step b) of the method, the final boiling point of the light fraction (910) being lower than or equal to 200°C.

11. The method according to any one of claims 1 and 2, wherein step b) comprises the following sub-steps: b1) filtering the liquid effluent (320) in a washing and filtering device (41) to obtain a filtered carbon black cake and a liquid fraction (425); b2) washing the filtered carbon black filter cake obtained at the end of step b1) in the presence of a washing solvent to obtain a filtered and washed carbon black filter cake (430) and a washing stream (405).

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

13. The method according to any one of claims 1 and 2, wherein the hydrocarbon fraction (730) has a content of C10-C20 hydrocarbon compounds of 20% to 65% by weight relative to the total weight of the hydrocarbon fraction.

14. The method according to any one of claims 1 and 2, wherein the hydrocarbon fraction (730) has a C20-C40 hydrocarbon compound content of 30% to 80% by weight relative to the total weight of the hydrocarbon fraction.

15. The method according to any one of claims 1 and 2, wherein the hydrocarbon fraction (730) has an initial boiling point of 50 to 325°C and a final boiling point of 350 to 520°C.

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