EP4222220A1

EP4222220A1 - Method for solvolysing tyres with recycling of a hydrocarbon fraction comprising aromatic compounds

Info

Publication number: EP4222220A1
Application number: EP21773415.1A
Authority: EP
Inventors: Ann Cloupet; Romina Digne
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2020-09-29
Filing date: 2021-09-17
Publication date: 2023-08-09
Also published as: FR3114592A1; US20230331991A1; KR20230075450A; FR3114592B1; AU2021354733A1; CA3189864A1; BR112023003923A2; CN116323130A; WO2022069259A1; JP2023542420A

Abstract

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

Description

SOLVOLYSIS OF TIRES WITH RECYCLING OF A HYDROCARBON CUT COMPRISING AROMATIC COMPOUNDS

Field of invention

The present invention relates to a process for converting used tires by thermal decomposition.

State of the art

Conversion processes by thermal decomposition of used tires generally aim to produce gaseous, liquid and solid fractions. The tire is generally shredded initially to obtain either shredded tires still containing some of the textile fibers or metallic threads contained in the tire (typically pieces of 1 to 10 cm) or aggregates (of dimensions generally less than 6 mm) free of textile fibers or metal threads. It is possible to react these fillers thus prepared by exposing them to temperature to decompose the used tire and recover a gaseous fraction, a liquid fraction and a solid fraction. To succeed in decomposing the tire, it is generally necessary to expose the tire to a fairly high temperature, generally between 300° C. and 900° C. for reaction times ranging from 30 minutes to several hours.

There are many technologies for implementing these reactions. For example, tires can be subjected to high temperatures in rotating ovens (Lewandowski et al., Journal of Analytical and Applied Pyrolysis, 140, 2019, 25-53), or in moving beds (EP2661475). These technologies are robust but generally require working at fairly high temperatures, generally on average above 500°C. In these processes, the carbon black, generally present in the charge at 25-40% by weight and originally consisting of very fine particles / sub-micrometric or micrometric agglomerates, tends to agglomerate in the presence of the decomposed gum which forms a coke linking these structures at different scales, the solid often leaving the reactor in the form of blocks of several millimeters / centimeters which must then be finely ground in order to reuse this solid as carbon black, this which requires significant energy expenditure. In these processes, the temperature conditions are high and there are essentially gaseous and solid fractions in the reactor. The liquids produced then result from the condensation of the gaseous products downstream of the reactor. These high temperature conditions also tend to promote polycondensation and coking reactions to form polyaromatic structures from cyclization reactions involving the aromatic and olefinic structures present (MF Laresgoiti, BM Caballero, I. de Marco, A. Torres , MA Cabrero, MJ Chomon, J. Anal. AppL Pyrolysis 71 (2004) 917-934) or coke. The higher the temperature, the more the contents of polyaromatic structures formed and of coke formed increase. However, if the aromatic molecules are on the one hand good solvents and on the other hand find many applications, in particular as petrochemical bases, the polyaromatic structures on the other hand are detrimental to the quality of the liquid formed and very difficult to refine or convert. . They are also coke precursors. It is therefore advantageous to try to limit the polycondensation reactions as much as possible to produce a minimum of polyaromatic structures while preserving the mono-aromatic structures present.

To improve the quality of the solid phase and limit the formation of coke on the carbon black, it is possible to lower the partial pressure of hydrocarbons by injecting steam during the cracking reactions which nevertheless require a high temperature beyond of 500°C to carry out the cracking under essentially gas-solid conditions (US2016/0083657). These gas-solid processes generally induce productions of incondensable gases under atmospheric conditions which are very high and comprised between 10 and 25% by weight with respect to the load of tires entering the reactor. However, the recovery of the reaction gases is locally complex. These gases are therefore generally used to produce the heat required to carry out the reactions, but this is done to the detriment of the quantity of easily recoverable liquid products which is therefore then limited. These liquid fractions are in fact then possibly upgraded to produce new hydrocarbon cuts (naphtha, gasoline, kerosene, diesel, vacuum distillate, residues) used in refineries to produce fuels or in petrochemicals to produce bases then used to develop raw materials. plastics. However, these cuts must be refined in order to bring them to the desired specifications. The more polyaromatic structures there are, the more complex the refining.

An alternative way consists in bringing the tire loads into contact with a liquid, raising this liquid in temperature and dissolving and converting the tires into a homogeneous liquid phase in which the tire load is agitated and gradually disappears. An example of this implementation is given in US 3,978,199 and US 3,704,108. This type of process makes it possible to recover the carbon black in the liquid phase after filtration without there having been agglomeration of these particles or deposition of coke on their surface as is the case in reactions operating in the gas-solid phase. The implementation under temperature conditions below 450 ° C also limits the polycondensation reactions of the aromatics, the formation of coke on the surface of the particles of carbon black and the formation of gas which is generally between 1 and 7% weight of the incoming load. The use of a solvent containing aromatic fractions, preferably mono- aromatics, is favorable and makes it possible to better dissolve the charge in the reactor. As tires are naturally composed of different rubbers including large quantities of synthetic rubber composed of styrene-butadiene rubber (SBR or "Styrene Butadiene Rubber" according to the English terminology), the liquid fractions produced contain significant fractions of aromatics and it may be advantageous to separate and recycle part of the liquid formed during the reaction to use it as a solvent, while the non-recycled liquid fraction can be sent to a refinery to be refined and then upgraded as a hydrocarbon cut to feed the product pools or petrochemicals. By way of example, in document US Pat. No. 3,978,199, the heavy fraction of the filtrate obtained after distillation, comprising aromatic compounds, is heated and then recycled into the reactor as liquid solvent. However, depending on the composition of the heavy fraction used to dissolve the solid filler, as well as the recycle rate of the heavy fraction relative to the solid filler, the duration of carbon black filtration can vary considerably. The Applicant has developed a new process for converting used tires making it possible to prevent the drawbacks cited above by optimizing the existing process as described in document US Pat. No. 3,978,199.

Objects of the invention

The subject of the present invention is a method for converting used tires to obtain carbon black comprising at least the following steps: a) sending a solid charge based on used tires to a reaction zone in the presence of a liquid solvent comprising aromatic compounds for at least partially dissolving said solid charge and thermally decomposing said at least partially dissolved solid charge at a temperature less than or equal to 425° C. and at a pressure less than 1.5 MPa in order to obtain a gaseous effluent and a first liquid effluent comprising the carbon black, the mass ratio between the liquid solvent and the solid filler being greater than 3 weight/weight; b) the first liquid effluent obtained in step a) is sent to a filtration and washing zone in the presence of a washing solvent in order to obtain a filtered and washed carbon black cake and a second liquid effluent; c) said gaseous effluent obtained at the end of step a) and at least partly the second liquid effluent obtained at the end of step b) are sent to a fractionation zone to obtain at least at least one hydrocarbon cut whose aromatic compound content is greater than 30% by weight relative to the total weight of said hydrocarbon cut, and further comprising:

- a content of C5-C10 hydrocarbon compounds of less than 20% by weight relative to the total weight of the hydrocarbon cut; and - a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon cut; d) at least part of said hydrocarbon fraction obtained at the end of step c) is sent into the reaction zone as liquid solvent of step a); e) the filtered and washed carbon black cake obtained at the end of step b) is dried at a temperature of between 50 and 200° C. to recover the carbon black.

The Applicant has surprisingly discovered that the use of such a recycled hydrocarbon cut as a liquid solvent in the used tire conversion zone, comprising a content rich in aromatic compounds, low in C40+ compounds (vacuum residues), and a content of C5-C10 hydrocarbon compounds (gasoline) that is not too high, with a specific solvent/solid filler mass ratio, synergistically allows better dissolution and decomposition of the solid filler, thus maximizing the production of carbon black.

In one embodiment according to the invention, before step a) of said method, said solid filler is sent to a pre-treatment unit to eliminate at least part of the textile fibers and metal threads contained in said solid filler.

In one embodiment according to the invention, step a) comprises the following sub-steps: a1) said solid charge and said liquid solvent are sent to a first stirred reactor to at least partially dissolve said solid charge; a2) said solid charge, at least partially dissolved, obtained at the end of step a1) is sent to a second stirred reactor to thermally decompose at a temperature less than or equal to 425° C. said solid charge and obtain the first liquid effluent containing particles of carbon black in suspension.

In one embodiment according to the invention, the content of aromatic compounds in the hydrocarbon cut is greater than 40% by weight relative to the total weight of said cut.

In one embodiment according to the invention, the content of C5-C10 hydrocarbon compounds in the hydrocarbon cut is less than 10% by weight relative to the total weight of said cut. In one embodiment according to the invention, the content of C40+ hydrocarbon compounds in the hydrocarbon cut is less than 3% by weight relative to the total weight of said cut.

In one embodiment according to the invention, the mass ratio between said liquid solvent and the solid filler is greater than 3 weight/weight.

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

In one embodiment according to the invention, in step c) of said process, a light cut is also obtained, the final boiling temperature of which is preferably between 250°C and 325°C.

In one embodiment according to the invention, the light cut is sent at least in part upstream to a distillation column to obtain at least one light cut whose final boiling point is less than or equal to 200°C.

In one embodiment according to the invention, said light cut whose final boiling point is less than or equal to 200° C. is sent at least in part to the filtration/washing zone as washing solvent according to step b) of said method.

In one embodiment according to the invention, step b) comprises the following sub-steps: b1) the liquid effluent is filtered in a washing and filtration device to obtain a filtered carbon black cake and a fraction liquid ; b2) the filtered carbon black cake obtained at the end of step b1) is washed in the presence of a washing solvent to obtain the filtered and washed carbon black cake and a washing flow.

Preferably, the washing stream is sent to an intermediate fractionation unit to obtain a cut which is recycled at least in part upstream of the washing and filtration device as washing solvent.

Advantageously, the hydrocarbon cut comprises a content of C10-C20 hydrocarbon compounds of between 20 and 65% by weight relative to the total weight of the hydrocarbon cut. Advantageously, the hydrocarbon cut comprises a content of C20-C40 hydrocarbon compounds of between 30 and 80% by weight relative to the total weight of the hydrocarbon cut.

Advantageously, the hydrocarbon cut comprises an initial boiling temperature of between 50°C and 325°C and a final boiling temperature of between 350°C and 520°C.

List of Figures

Figure 1 is a schematic representation of the method according to the invention.

Figure 2 is a schematic representation of the process shown in Figure 1 in which the reaction zone and the filtration and washing zone of the process are further detailed.

detailed description

By Cn hydrocarbon cut is meant a cut comprising hydrocarbons with n carbon atoms.

By Cn+ cut is meant a cut comprising hydrocarbons with at least n carbon atoms.

Referring to Figure 1, representing an embodiment according to the invention, the process for converting used tires comprises at least the following steps: a) sending a solid charge 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 filler and thermally decompose said at least partially dissolved solid filler at a temperature less than or equal to 425°C, preferably between 375 and 425° C, and at a pressure below 1.5 MPa, preferably between 0.5 and 1.2 MPa, in order to obtain at least one gaseous effluent 310 and a first liquid effluent 320 comprising carbon black, the ratio mass between the liquid solvent 760 and the solid filler 100 being greater than 3 weight/weight; b) the liquid effluent 320 obtained in step a) is sent to a filtration and washing zone 40 in the presence of a washing solvent in order to obtain a filtered and washed carbon black cake 430 and a second liquid effluent 410; c) said gaseous effluent 310 obtained at the end of step a) is sent at least in part, preferably in whole, and at least in part, preferably in whole, the second liquid effluent 410 obtained at the end from step b) to a fractionation zone 70 to obtain at least one hydrocarbon cut 730 comprising a content of aromatic compounds greater than 30% by weight relative to the total weight of said hydrocarbon cut, preferably greater than 40% by weight , and comprising:

- a content of C5-C10 hydrocarbon compounds of less than 20% by weight relative to the total weight of the hydrocarbon cut 730, preferably less than 10% by weight, more preferably between 1 and 8% by weight; and

- a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon cut 730, preferably less than 3% by weight, more preferably less than 1% by weight, and even more preferably less than 0, 5% by weight; d) said hydrocarbon fraction 730 obtained at the end of step c) is sent at least in part to reaction zone 80 as liquid solvent 760 of step a); e) the filtered and washed carbon black cake 430 obtained at the end of step b) is dried at a temperature of between 50° C. and 200° C., preferably for a time sufficient for the solvent content washing in the dried cake is 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 preferably between 1 hour and 15 hours, to recover the carbon black 520.

The solid filler 100 used in the context of the present invention is advantageously based on tires resulting from the treatment of used tires which may come from any origin, such as light vehicles (LV) or heavy goods vehicles (HGV) for example. Said solid filler may advantageously be in the form of tire granulates, ie in the form of particles of size less than 6 mm. Preferably, said solid filler 100 is substantially free of textile fibers and metallic threads, and/or shredded tires, ie pieces of shredded tires, of characteristic size generally between 1 cm and 20 cm. Thus, according to a preferred embodiment according to the invention, the solid filler 100 is sent to a pretreatment unit 10 in order to remove the textile fibers and the metallic threads 110 from the solid filler 100. Such a pretreatment unit is indeed known to those skilled in the art and may consist of shredders of different types (ie a rotary shear, a shredder shredder, a granulator, a refining shredder), a magnetic separator, or even a vibrating screen, a separation table. According to step a) of the conversion process, the gum which is contained in the solid filler 100 is dissolved in contact with the liquid solvent 760 and then is thermally decomposed. The origin and composition of liquid solvent 760 will be described in detail below. Step a) is preferably carried out at a temperature less than or equal to 425° C., preferably at a temperature between 375 and 425° C., and at a pressure less than 1.5 MPa, preferably between 0. 8 and 1.2 MPa. At the end of step a), the at least one gaseous effluent 310 and the first liquid effluent 320 comprising the carbon black, and possibly solid matter 210 contained in the used tires, such as metal wires, are obtained. or the textile fibers, which are released and separated from the liquid effluent 320 obtained at the end of this step.

The first liquid effluent 320 comprising the carbon black is then sent to the filtration and washing zone 40 (i.e. step b) of the preparation process according to the invention) in order to recover the filtered and washed carbon black cake. 430 and the 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, preferably less than 5 cP, more preferably less than 3 cP, such than measured according to ASTM D3236.

The filtration and washing unit can comprise any device allowing the filtration of the carbon black particles contained in the first liquid effluent 320. Such a device can for example take the form of a rotary filter operating preferentially at a temperature between 50°C and 200°C. In step b), the carbon black cake is washed using a washing solvent.

In one embodiment according to the invention, the washing solvent used during step b) is a solvent external to process 800, as represented in FIG. Such a solvent can for example be toluene.

In another embodiment according to the invention, the washing solvent used during step b) is composed at least in part of a light cut 720 obtained at the end of step c). More particularly, referring to FIG. 2, a fraction of the light cut 720 can be sent to a distillation column 90 via line 725. The complementary fraction 735 of the light cut is sent outside the process according to the invention. as a valuable product. At the outlet of the distillation column 90, a light cut 910 is obtained comprising aromatic compounds, the final boiling point of which is less than or equal to 200° C., preferably less than 150° C., which can be used at least in part of washing solvent from the filtration/washing zone 40. The heavier cut 920 can be sent out of the process as valuable product 920. The filtered and washed carbon black cake 430 is sent to a drying unit 50 operating at a temperature of between 50 and 200° C., preferably between 50 and 150° C. in order to recover the carbon black 520 (ie the step e) of the process according to the invention). Advantageously, the vapor effluent 510 from the drying unit 50 comprising the washing solvent is recycled in the washing/filtration unit 40.

According to an essential characteristic of the conversion process according to the invention, the gaseous effluent 310 obtained at the end of stage a) and the second liquid effluent 410 obtained at the end of stage b) are sent to the fractionation unit 70 (i.e. step c) of the process according to the invention) to produce at least one hydrocarbon cut 730 comprising a content of aromatic compounds greater than 30% by weight relative to the total weight of said hydrocarbon cut 730, and further comprising at least:

- a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon cut 730, preferably less than 3% by weight, more preferably less than 1% by weight, and even more preferably less than 0, 5% by weight.

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

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

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

Indeed, it has been observed by the Applicant that the use of such a recycled hydrocarbon cut as liquid solvent 760 of the reaction zone 80 (ie step d) of the process according to the invention), with a content rich in aromatic compounds, low in C40+ compounds (vacuum residues), and a content of C5-C10 hydrocarbon compounds (gasoline) not too high, and using a solvent/solid filler mass ratio greater than 3 w/w, preferably between 3 and 10 w/w, more preferably between 4 and 7 w/w, synergistically allows better dissolution and decomposition of the solid filler 100 thus maximizing the production of carbon black . This results in particular in a shorter filtration time for the carbon black in the washing/filtration zone 40.

Advantageously, the fractionation zone 70 also makes it possible to obtain incondensable gases 710, the light cut 720 whose final boiling temperature is preferably between 250° C. and 325° C., and a heavy cut 740, the temperature of which initial boiling point is preferably between 350°C and 450°C. Advantageously, the light cut 720 can be sent at least in part as washing solvent to the washing and filtration zone 40 to obtain the filtered and washed carbon black cake 430.

Advantageously, the light cut 720 comprises a content of C10- hydrocarbon compounds greater than 60% by weight relative to the total weight of the light cut 720.

Advantageously, the heavy cut 740 comprises a content of C40+ hydrocarbon compounds greater than 60% by weight relative to the total weight of the heavy cut 740.

According to the invention, at least part of a fraction of the hydrocarbon cut 730 is sent to the reaction zone 80 of step a) as liquid solvent 760, the other part 750 being advantageously sent outside the process according to the invention as a recoverable product. The mass ratio between the liquid solvent 760 and the flow rate of the solid filler 100 injected into the reaction zone 80 is greater than 3 weight/weight (w/w), preferably between 3 and 10 weight/weight, more preferably between 4 and 7 weight/weight. Indeed, one of the characteristics of the liquid solvent 760 is that it contains an aromatic content greater than 30% by weight relative to the total weight of said liquid solvent 760, making it possible to effectively dissolve the solid filler 100 and to effectively reduce the viscosity of the medium. reaction in the reaction zone 80. Another advantage of the process according to the invention is that the use of such a solvent makes it possible to remain in liquid form while limiting the pressure in the reactors to a level below 1.5 MPa. given the limited production of gas and light hydrocarbons in the reaction zone 80 and the low content of C10- hydrocarbon compounds in the hydrocarbon cut 730.

In order to better understand the invention, the description given below by way of example of application relates to a process for converting used tires making it possible to maximize the recovery of carbon black. Referring to Figure 2, solid filler 100 is sent to the pre-treatment unit 10 in order to remove the textile fibers and metallic threads 110 from the solid charge 100. The solid filler substantially free of textile fibers and metallic threads is then sent to the reaction zone 80 allowing the thermal degradation of the used tires comprising a first stirred reactor 20 supplied with liquid solvent 760 and aimed at promoting the dissolution of the tire aggregates or shredded material contained in the solid charge 100. The liquid solvent charge/solid charge mass ratio is greater than 3 weight/weight, of preferably between 3 and 10, more preferably between 4 and 7 weight/weight. The temperature in reactor 20 is preferably between 200°C and 300°C, preferably between 250°C and 290°C. In the first stirred reactor 20, the ground materials or the aggregates are dissolved. The time necessary to carry out this dissolution is preferably between 30 minutes and 2 hours. The pieces of rubber, and the carbon black which is gradually released from the rubber, remain in suspension thanks to mechanical or hydrodynamic agitation, induced for example by an upward flow of liquid resulting from recirculation by forced convection, or by any other means of keeping the medium agitated. The metal wires, possibly still present in the solid charge and which would not have been dissolved, sediment and leave the first stirred reactor 20 at its base via line 210. Under these conditions, the temperature is too low for the reactions of carbon-carbon cracking starts significantly and only the crosslinking bonds between polymers, such as the SS bonds linked to the vulcanization of rubbers can crack significantly. The liquid fraction 220 obtained containing the residual solid matter in suspension is sent to a second stirred reactor 30 in which the thermal degradation reactions are carried out under conditions of moderate temperature, ie at a temperature less than or equal to 425° C., preferably between 375° C. and 425° C., and for a limited time (corresponding to the residence time of the liquid fraction in the reactor 30) preferably between 30 minutes and 2 hours, preferably between 45 minutes and 90 minutes. The amount of heat necessary to carry out the thermal degradation reactions can be provided by an exchanger located on a circle (“pumparound” according to English terminology, not shown in the figures) 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 a furnace on the load upstream of the reactor, for example. Stirring in the second stirred reactor 30 is maintained by means of a mechanical stirring system or by the rotating system or by any other means known to those skilled in the art. Preferably, the reactor pressure is maintained at a level below 1.5 MPa by means of a control valve (not shown in the figures). At the end of the reaction, the first liquid effluent 320 containing the particles of carbon black in suspension and the gaseous effluent 310 are obtained in the second stirred reactor 30. The first liquid effluent 320 is then sent to the filtration and washing zone 40 , comprising a rotary filter 41 and an intermediate fractionation unit 42 (cf. FIG. 2). The rotary filter 41 preferably operates at a temperature between 50° C. and 200° C., and makes it possible to obtain a carbon black cake and a liquid fraction 425. The carbon black cake is then washed with the washing solvent 800 such as toluene, at a temperature preferably between 50° C. and 100° C., making it possible to recover the filtered and washed carbon black 430. After the filtration/washing step, a washing flow 405 can be sent into the intermediate fractionation unit 42 to obtain a cut 610 which can be recycled at least in part upstream of the rotary filter 41 by means of the line as complementary washing solvent, and a cut 415 which can be sent with the fraction liquid 425, in the fractionation zone 70 as second liquid effluent 410. The filtered and washed carbon black 430 is then sent to the drying unit 50 operating at a temperature between 50 and 200° C., advantageously for a sufficient time for the content of washing solvent in the dried cake to be less than 0.5% by weight relative to the total weight of said dried cake. The filtered, washed and dried carbon black 520 can then be advantageously pelletized (granulated) with water to form pellets of a few millimeters for example to facilitate its transport and its recovery. The carbon black thus produced can again be used in the elastomer industry as a reinforcing agent, or as a pigment for other applications in inks, plastics or paints for example, after subsequent processing and conditioning steps. of the material according to the uses and applications. The residual washing solvent can be recovered at the outlet of the drying unit 50 and be at least partially recovered via line 510.

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 directed towards the fractionation zone 70. The fractionation zone 70 can be constituted heat exchangers, gas-liquid separator drums, a distillation column containing a top draw, a bottom draw and a side draw, or a sequence of several distillation columns, such as a sequence a distillation column at atmospheric pressure operating with a draw-off at the top and a draw-off at the bottom, followed by a distillation column operating under a low vacuum. This fractionation zone 70 makes it possible in particular to produce the hydrocarbon fraction 730 comprising a content of aromatic compounds greater than 30% by weight relative to the total weight of said 730 hydrocarbon cut, preferably greater than 40% by weight, and further comprising:

- a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon cut 730, preferably less than 3% by weight, more preferably less than 1% by weight, and even more preferably less than 0, 5% by weight; of which at least a part can be recycled as liquid solvent 760 in the reaction zone 80, the other part 750 being able to be upgraded as a product. Preferably, the hydrocarbon cut is sent to the first reactor 20 of the reaction zone 80 as liquid solvent.

This fractionation zone 70 also makes it possible to obtain the incondensable gas 710, the light cut 720 whose final boiling temperature is preferably between 250° C. and 325° C., and the heavy cut 740, whose temperature of the initial boiling point is preferably between 350°C and 450°C. Advantageously, the light cut 720 can be sent at least in part as washing solvent to the washing and filtration device 41 of the washing and filtration zone 40 to obtain the filtered and washed carbon black cake 430.

When starting up the installation, in the absence of production of a stabilized intermediate cut, ie the hydrocarbon cut 730, it is possible to temporarily use an imported solvent which will preferably consist of a content of aromatic molecules greater than 40% weight compared to the total weight of the cut. This cut may therefore consist, for example, of conversion effluents from the FCC catalytic cracking process (abbreviation of the Anglo-Saxon terminology “Fluid Catalytic Cracking,” which means fluidized bed catalytic cracking), middle distillate (LCO or “light cycle oil” according to the Anglo-Saxon terminology) or heavy distillate (HCO or “heavy cycle oil” according to the Anglo-Saxon terminology) for example. Examples

The following examples illustrate preferred embodiments of the method according to the present invention without however limiting its scope. The method used to illustrate the invention is in accordance with that described in Figure 2.

In a first example, in accordance with the invention, use is made of used tire granules (solid filler), produced by granulators using grinders, which come from truck tires and the grains resulting from the grinding have a size close to 2 millimeters . The tire granules come from a pre-treatment unit 10 and are free of textile and metal fibres. The aggregates are then sent continuously to a dissolution reactor where they are mixed with the liquid solvent resulting from the recycling of the hydrocarbon cut 730 from the fractionation zone 70. Part of the hydrocarbon cut 730 serves as liquid solvent 760 whose composition is shown in Table 1 below. The quantity of solid charge treated is 100 kg/h. The quantity of solvent which is recycled in the reactor 20 is 500 kg/h, corresponding to a solvent/aggregate mass ratio equal to 5 w/w. In the reactor 20, the temperature is maintained equal to 290° C., which makes it possible to dissolve the aggregates. The liquid fractions and the carbon black in suspension are then sent to reactor 30 where the temperature is maintained at 400° C. 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 entirely to the fractionation zone 70. The first liquid effluent 320 is sent to a rotary filter 41 operating at 140°C. A washing of the filtered carbon black is carried out 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 operating at 150° C. for 24 hours to recover the filtered, washed and dried carbon black 520.

In Examples 2 to 5, not in accordance with the invention, the steps of the conversion process and the operating conditions are identical to those of Example 1, with the difference of the following characteristics:

- examples 2 and 3: the content of C40+ hydrocarbon compounds (vacuum residues or RSV) of the liquid solvent 760 is outside the range according to the invention;

- example 4: the content of C5-C10 hydrocarbon compounds (petrol) of the 760 hydrocarbon cut is outside the range according to the invention;

- Example 5: the solvent/solid filler mass ratio is outside the range according to the invention. Table 1

By comparing the results in terms of carbon black filtration time with respect to Example 1 according to the invention, it is found that when the content of C40+ hydrocarbon compounds (vacuum residue) is 8% by weight in the cut hydrocarbon 730 relative to the total weight of said cut (example 2), the carbon black filtration time is multiplied by 4, or even multiplied by 8 when the content of C40+ hydrocarbon compounds is 20% by weight (example 3) . Furthermore, when the content of C5-C10 hydrocarbon compounds (gasoline) is 26% by weight in the hydrocarbon cut 730, the carbon black filtration time is multiplied by 4 (example 4). Finally, a non-optimized liquid solvent 760/solid filler 100 mass ratio significantly lengthens the carbon black filtration time (Example 5).

Claims

1. Process for converting used tires to obtain carbon black comprising at least the following steps: a) sending a solid charge (100) based on used tires into a reaction zone (80) in the presence of a liquid solvent (760) comprising aromatic compounds for at least partially dissolving said solid filler and thermally decomposing said at least partially dissolved solid filler at a temperature less than or equal to 425° C. and at a pressure less than 1.5 MPa in order to obtain a gaseous effluent (310) and a first liquid effluent (320) comprising the carbon black, the mass ratio between the liquid solvent (760) and the solid filler (100) being greater than 3 weight/weight; b) the first liquid effluent (320) obtained in step a) is sent to a filtration and washing zone (40) in the presence of a washing solvent in order to obtain a filtered and washed carbon black cake (430) and a second liquid effluent (410); c) at least partly said gaseous effluent (310) obtained at the end of step a) and at least partly the second liquid effluent (410) obtained at the end of step b) are sent to a fractionation zone (70) to obtain at least one hydrocarbon cut (730) comprising an aromatic compound content greater than 30% by weight relative to the total weight of said hydrocarbon cut, and further comprising:

- a content of C5-C10 hydrocarbon compounds of less than 20% by weight relative to the total weight of the hydrocarbon cut; and

- a content of C40+ hydrocarbon compounds of less than 5% by weight relative to the total weight of said hydrocarbon cut; d) at least part of said hydrocarbon fraction (730) obtained at the end of step c) is sent to the reaction zone (80) as liquid solvent (760) of step a); e) the filtered and washed (430) carbon black cake obtained at the end of step b) is dried at a temperature of between 50 and 200° C. to recover the carbon black.

2. Method according to claim 1, wherein before step a), said solid filler (100) is sent to a pretreatment unit (10) to remove at least in part the textile fibers and the metal threads contained in said filler solid (100).

3. Method according to one of claims 1 or 2, in which step a) comprises the following sub-steps: a1) said solid charge (100) and said liquid solvent (760) are sent to a first stirred reactor ( 20) to at least partially dissolve said solid filler (100); a2) said solid charge, at least partially dissolved, obtained at the end of step a1) is sent to a second stirred reactor (30) to thermally decompose at a temperature less than or equal to 425° C. said solid charge and obtain a liquid effluent containing carbon black particles in suspension.

4. Process according to any one of claims 1 to 3, in which the content of aromatic compounds in the hydrocarbon cut (730) is greater than 40% by weight relative to the total weight of said cut.

5. Process according to any one of claims 1 to 4, in which the content of C5-C10 hydrocarbon compounds in the hydrocarbon cut (730) is less than 10% by weight relative to the total weight of said cut.

6. Process according to any one of claims 1 to 5, in which the content of C40+ hydrocarbon compounds in the hydrocarbon cut (730) is less than 3% by weight relative to the total weight of said cut.

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

8. Process according to any one of claims 1 to 7, in which in step c), a light cut (720) is also obtained, the final boiling temperature of which is preferably between 250° C. and 325° C. .

9. Process according to claim 8, in which the light cut (720) is sent at least in part upstream to a distillation column (90) to obtain at least one light cut (910) whose final boiling point is less than or equal to 200°C.

10. Process according to claim 9, in which said light cut (910) whose final boiling point is less than or equal to 200°C is sent at least in part to the filtration/washing zone (40) as washing solvent according to step b) of said method.

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

12. Method according to claim 11, in which the washing stream (405) is sent to an intermediate fractionation unit (42) to obtain a cut (610) which is recycled at least in part upstream of the washing device and filtration (41) as washing solvent.

13. Process according to any one of claims 1 to 12, in which the hydrocarbon cut (730) comprises a content of C10-C20 hydrocarbon compounds of between 20 and 65% by weight relative to the total weight of the hydrocarbon cut.

14. Process according to any one of claims 1 to 13, in which the hydrocarbon cut (730) comprises a content of C20-C40 hydrocarbon compounds of between 30 and 80% by weight relative to the total weight of the hydrocarbon cut.

15. Process according to any one of claims 1 to 14, in which the hydrocarbon fraction (730) has an initial boiling temperature of between 50°C and 325°C and a final boiling temperature of between 350°C and 520°C.