Reactor for dissolving solid raw materials based on thermoset materials, such as used tire particles

Abstract

The invention relates to a reactor for dissolving a solid-based feedstock in the form of particles, such as used tire particles, having a size, for example between 1 and 25 mm, in the presence of a reaction stream with an upward flow comprising a liquid solvent, said reactor comprising a chamber (1) of elongated shape along a vertical axis, the chamber comprises an upper portion (210) of cross section S1 and a lower portion (220) of cross section S2, the upper portion (210) having a cross section S1 larger than the lower portion (220), the reactor further comprising a circuit for recirculating the reaction stream, the circuit comprises means (6) for withdrawing at least part of the reaction stream at the level of the upper part (210) and means (5) for introducing at least part of the withdrawn reaction stream at the level of the lower part (220).

Description

Field of the Invention

[0001] The present invention relates to the field of dissolving solid raw materials based on thermosetting materials such as old tire particles. The present invention also relates to the field of dissolving and transforming old tires by pyrolysis. Background Art

[0002] Methods for transforming old tires by pyrolysis generally aim to produce gas, liquid, and solid fractions. Tires are usually initially ground to obtain ground tire material (usually fragments of 1 to 10 cm) that still contains a part of the textile fibers or metal wires contained in the tires, or particles without textile fibers or metal wires (usually less than 6 mm in size). These raw materials thus prepared can be made to react by exposing them to heat in order to decompose the old tires and recover the gas fraction, the liquid fraction, and the solid fraction. In order to successfully decompose the tires, it is generally necessary to expose the tires to a rather high temperature, usually between 300°C and 900°C, with a reaction time of 30 minutes to several hours.

[0003] There are many techniques for performing 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 a moving bed (EP 2661 475). These techniques are robust, but generally require working at rather high temperatures, typically averaging above 500 °C. In these methods, carbon black - which is usually present in the feedstock in a proportion of 25 - 40 wt% and initially consists of very fine submicron or micron particles / aggregates - tends to agglomerate in the presence of decomposed rubber, which forms coke binding these structures on various scales. The solid usually leaves the reactor in the form of chunks of several millimeters / centimeters, which then have to be finely ground in order to reuse the solid as carbon black, which requires a considerable energy consumption. In these methods, the temperature conditions are high, and there are mainly gas and solid fractions in the reactor. The liquid produced comes from the condensation of the gaseous products downstream of the reactor. In addition, these high temperature conditions tend to promote polycondensation and coking reactions in order to form polyaromatic structures (M.F. Laresgoiti, B.M. Caballero, I. deMarco, A. Torres, M.A. Cabrero and M.J. Chomón., J. Anal. Appl. Pyrolysis, 71 (2004), 917–934) via cyclization reactions involving the aromatic and olefinic structures present or to form coke. The higher the temperature, the greater the content of polyaromatic structures and coke formed. In fact, while aromatic compound molecules are first of all good solvents and secondly have a wide range of applications, especially as petrochemical feedstocks, on the other hand, polyaromatic structures are detrimental to the quality of the liquid formed and are very difficult to refine or transform. In addition, they are coke precursors. Thus, it is advantageous to seek to minimize the polycondensation reaction in order to produce the least amount of polyaromatic structures while retaining the monaromatic structures present.

[0004] To improve the quality of the solid phase and limit coke formation on carbon black, the partial pressure of hydrocarbons can be reduced by injecting steam during the cracking reaction, which however requires a high temperature above 500 °C in order to carry out the cracking under substantially gas-solid conditions (US2016 / 0083657). These gas-solid processes generally result in the production of gases that are non-condensable under atmospheric conditions, which are extremely high relative to the tire feedstock entering the reactor and are between 10 wt% and 25 wt%. In fact, the upgrading of the reaction gases is locally complex. These gases are thus generally used to generate the heat required for the reaction, but doing so impairs the amount of liquid products that are easily upgradable, and is thus limited. This is because these liquid fractions are subsequently optionally upgraded to produce new hydrocarbon fractions (naphtha, gasoline, kerosene, gas oil, vacuum gas oil, residue), which are used in refineries to produce fuels or in petrochemistry to produce the base materials subsequently used to produce plastics. However, these fractions must be refined to meet the desired specifications. The more polyaromatic the structure, the more complex the refining.

[0005] An alternative approach involves contacting the tire feedstock with a liquid, raising the temperature of the liquid, and dissolving and transforming the tire in a homogeneous liquid phase in which the tire feedstock is agitated and gradually disappears. Examples of such an implementation are given in US 3 978 199 and US3 704 108. This type of process enables the recovery of carbon black in the liquid phase after filtration, without agglomeration of these particles or coke deposition on their surface (as in the reactions operating in the gas-solid phase). In addition, implementation at temperatures below 450 °C limits the polycondensation reaction of aromatic compounds, coke formation on the surface of carbon black particles, and the formation of gases that are generally between 1 wt% and 7 wt% of the feedstock introduced. It is advantageous to use a solvent containing an aromatic fraction, preferably a monoaromatic fraction, and enables better dissolution of the feedstock in the reactor. Since tires are naturally composed of various rubbers, including a large amount of synthetic rubber composed of styrene-butadiene rubber (SBR), the liquid fraction obtained contains a major fraction of aromatic compounds, and a portion of the liquid formed during the reaction can be advantageously separated and recycled to be used as a solvent, while the non-recycled liquid fraction can be sent to a refinery for refining and subsequently upgraded as a hydrocarbon fraction to feed the product pool or the petrochemical industry.

[0006] More precisely, the method described in patent US 3 704 108 includes a fluidized bed reactor which is fed on the one hand with a raw material consisting of tyre particles and on the other hand with a solvent. The reaction takes place in the presence of hydrogen and a catalyst under more severe temperature conditions between 370 °C and 450 °C. The initial stage which is favourable to the dissolution of the tyres is not described in this method. On the other hand, the formation of a transportable slurry consisting of particles and a solvent requires the use of finely divided tyre particles of 150 to 3000 μm, the slurry being transportable and heatable upstream of the reactor.

[0007] The method described in patent US 3 978 199 includes a reactor for the contact between tyres and a solvent so that the tyres can be dissolved in the solvent and carbon black can be recovered, the reactor being characterized in that it is sufficiently stirred by means of mechanical mixing means and that it operates at a temperature between 260 °C and 370 °C. The use of a sufficiently stirred reactor requires a large amount of liquid because the rubber tends to impregnate the liquid and swell. In addition, it is necessary to fill the interparticle spaces between the tyre particles in order to stir the suspension consisting of the particles and the solvent. Thus, the examples show a solvent / tyre degree close to 5 wt / wt. In addition, this method only includes the dissolution of the rubber of the tyres at a moderate temperature below 370 °C, which makes it impossible to effectively and significantly transform the liquid resulting from the dissolution of the rubber.

[0008] Application FR 3 108 617 discloses a sequence of methods capable of transforming old tyres and plastics, in which a solid raw material of ground old tyres in the form of particles based on 5 mm or less is fed into a reaction zone in the presence of a liquid solvent containing aromatic compounds in order to at least partially dissolve the solid raw material and thermally decompose the at least partially dissolved solid raw material at a temperature below or equal to 425 °C in order to obtain carbon black and a first hydrocarbon liquid fraction. The dissolution of the old tyres can take place in a first reactor which is mechanically stirred or by upward hydraulic stirring of the liquid flow. However, the dissolution reactor does not include means for separating the undissolved particles which may be entrained by the liquid at the outlet of the dissolution reactor. This is because, since the reactor is sufficiently stirred, a part of the undissolved particles can be entrained in the liquid leaving the dissolution reactor. In order to minimize the amount of partially or slightly dissolved particles at the outlet of the dissolution reactor, it is preferable to use relatively small-sized particles (<5 mm) so that the particles dissolve very rapidly, which makes it possible to limit the entrainment of particles downstream in the liquid product.

[0009] The literature review shows that the initial dissolution stage of the old particles is important in converting old tires into liquid products and recovering carbon black. Changes in tire shredding and granulation technologies have now made it possible to produce tire particles with dimensions of approximately 15 to 25 mm, with more than 95% being free of fabric or metal fibers. The ability to upgrade large-sized particles is advantageous as it enables reducing the energy and cost required to manufacture these particles. However, the larger the particle size, the greater the transportation and dissolution problems. The object of the present invention is to provide a reactor for dissolving solid raw materials based on thermosetting materials, such as old tire particles, also referred to herein as a dissolver, which enables handling particles of any size, and thus, in the case of the current technology for obtaining particles, can have a size of up to 25 mm, for example. Summary of the Invention

[0010] A first subject according to the present invention relates to a reactor for dissolving a solid raw material based on a thermosetting material in the presence of an upward flowing reaction stream comprising a liquid solvent, said solid raw material being in the form of particles with a size between a first minimum value and a second maximum value, such as old tire particles, said solvent being capable of dissolving said solid raw material, said reactor comprising: - A chamber having an elongated shape along a vertical axis, said chamber comprising an upper part with a cross-section S1 and a lower part with a cross-section S2, said upper part being located above said lower part along the vertical axis; - Means for introducing said solid raw material into the upper part of said chamber; - Means for introducing the liquid solvent; - Means for discharging at least a portion of said reaction stream from said dissolution reactor; - Means for discharging a gas fraction located at the top of the chamber of said reactor; The reactor is characterized in that: - The cross-section S1 of the upper part of said chamber is larger than the cross-section S2 of the lower part of said chamber; and in that - The reactor further comprises a circuit for recycling said reaction stream, said circuit comprising means for withdrawing at least a portion of the reaction stream at the upper level of said chamber and means for introducing at least a portion of the withdrawn reaction stream at the lower level of said chamber.

[0011] According to one or more embodiments, the upper and lower parts have a substantially circular cross-section, and the ratio of the diameter of the cross-section S2 to the diameter of the cross-section S1 is between 0.1 and 0.8.

[0012] According to one or more embodiments, the upper part of said chamber and the lower part of said chamber are connected by a frustoconical element opening upward along said vertical axis.

[0013] According to one or more embodiments, the half-cone angle formed by the cross-section of the frustoconical element and the vertical axis is between 7° and 45°.

[0014] According to one or more embodiments, the device for discharging at least a portion of the reaction stream is located in the recirculation loop between the withdrawal device and the introduction device.

[0015] According to one or more embodiments, the device for introducing solid raw materials is located at the top of the chamber of the reactor.

[0016] According to one or more embodiments, the device for withdrawing at least a portion of the reaction stream is axially located at the center of the cross-section of the upper part where a deflector is suspended.

[0017] According to one or more embodiments, the device for introducing solid raw materials is located at the periphery of the upper part of the chamber of the reactor.

[0018] According to one or more embodiments, the reactor further includes at least one grid positioned along the vertical axis in the upper part of the chamber of the reactor, between the chamber wall of the reactor and the device for withdrawing the reaction stream, and the bottom part of the grid is located at a height lower than the inlet of the withdrawal device.

[0019] According to one or more embodiments, the device for introducing the liquid solvent is located in the lower part of the chamber or directly in the loop for recirculating the reaction stream.

[0020] Another subject of the present invention relates to a continuous method for dissolving a solid raw material based on a thermosetting material in a reactor according to the present invention, in the presence of an upwardly flowing reaction stream containing a recirculating liquid solvent, the solid raw material being in the form of particles with a size between a first minimum value and a second maximum value, the reactor operating at a temperature between 150 °C and 350 °C, the method comprising at least the following stages: - Introducing the liquid solvent into the chamber of the reactor so as to completely immerse the lower part of the chamber and partially immerse the upper part of the chamber, forming a gaseous headspace above the reaction stream; - Introducing the solid raw material into the upper part of the chamber of the reactor; - Withdrawing a portion of the reaction stream located in the upper part of the chamber; - Discharging at least a portion of the withdrawn reaction stream from the method; - Recirculating at least a portion of the withdrawn reaction stream in the lower part of the chamber; Among them, the superficial velocity of the reaction material flow in the upper part is fixed at a value lower than the free settling velocity calculated for particles with a size equal to the first minimum value, and the superficial velocity of the reaction material flow in the lower part is fixed at a value higher than the minimum fluidization velocity calculated for particles with a size equal to the first minimum value. It should be understood that the superficial velocities in the upper and lower parts are different.

[0021] According to one or more embodiments, the minimum value is equal to 1 mm and the maximum value is equal to 25 mm.

[0022] According to one or more embodiments, the superficial velocity of the reaction material flow in the upper part (210) is less than 1 cm / s.

[0023] According to one or more embodiments, the superficial velocity of the reaction material flow in the lower part (220) is between 2 and 15 cm / s.

[0024] According to one or more embodiments, the residence time of the solid raw material in the lower part of the chamber of the reactor is 15 minutes to 20 hours.

[0025] According to one or more embodiments, the solid raw material is introduced into the gaseous headspace located in the upper part of the chamber.

[0026] According to one or more embodiments, the weight ratio of the liquid solvent to the solid raw material is less than 2.5 weight / weight.

[0027] According to one or more embodiments, the solid raw material is a raw material based on old tire particles. Description of the Drawings

[0028] Figure 1 is a schematic diagram of a reactor according to the present invention.

[0029] Figure 2 is a schematic diagram of a reactor according to an embodiment of the present invention.

[0030] Figure 3 is a schematic diagram of a reactor according to another embodiment of the present invention.

[0031] Figure 4 is a schematic diagram of an implementation manner of the reactor according to the present invention in a solvent decomposition method of a raw material based on old tires. Detailed Description

[0032] Definition In this specification, the term "Cx hydrocarbon" represents a hydrocarbon compound containing x carbon atoms. The term "Cx+ hydrocarbon" represents a hydrocarbon compound having at least x carbon atoms. The term "Cx to Cy hydrocarbon" represents a hydrocarbon compound having x to y carbon atoms.

[0033] The free settling velocity (Vt) of the particles can be defined according to the following mathematical formula: where G = 9.81 m / s 2 , Vp: the volume of the particle (m 3 ), rop: the density of the particle in the fluid (kg / m 3 ), rof: the density of the fluid (kg / m 3 ), Cd: the drag coefficient calculated as a function of the Reynolds number (dimensionless), Ap: the cross-sectional area projected by the particle in a plane perpendicular to the material flow (m 2 ).

[0034] The fluidization velocity is a parameter well-known to those skilled in the art and can be calculated, for example, via the correlation shown in the work of Wen C. H. and Yu Y. H., Chemical Engineering Progress Symposium Series, 82, 100 - 111 (1966).

[0035] The size of the particle is defined by its equivalent diameter d corresponding to a spherical particle having the same surface / volume ratio SV . Detailed Description of the Invention Figure 1 There is provided a reactor for dissolving a solid raw material based on a thermosetting material in the presence of an upward flowing reaction material stream containing a liquid solvent, the solid raw material having a size, for example, between 1 and 25 mm, such as old tire particles, the solvent being capable of dissolving the solid raw material, the reactor comprising: - a chamber 1 having an elongated shape along a vertical axis, the chamber including an upper part 210 with a cross-section S1 and a lower part 220 with a cross-section S2, the upper part 210 being located above the lower part 220 along the vertical axis, and the cross-section S1 of the upper part 210 of the chamber 1 being larger than the cross-section S2 of the lower part 220 of the chamber 1; - means 2 for introducing the solid raw material located in the upper part 210 of the chamber 1; - means 4 for introducing the liquid solvent; - A circuit for recirculating the reaction stream, the circuit comprising means 6 for withdrawing at least a portion of the reaction stream at a level of the upper part 210 of the chamber 1 and means 5 for introducing at least a portion of the withdrawn reaction stream at a level of the lower part 220 of the chamber 1; - Means 7 for discharging at least a portion of the reaction stream from the dissolution reactor, preferably located in the recirculation circuit between the means 6 for withdrawing at least a portion of the reaction stream and the means 5 for introducing at least a portion of the withdrawn reaction stream; - Means 3 for discharging the gas fraction located at the top of the chamber 1 of the reactor.

[0037] According to a basic aspect of the reactor according to the invention, the cross-section S1 of the upper part 210 of the chamber 1 is larger than the cross-section S2 of the lower part 220 of the chamber 1. Preferably, the upper part 210 and the lower part 220 have a substantially circular cross-section, and the ratio of the diameter of the cross-section S2 to the diameter of the cross-section S1 is between 0.1 and 0.8, preferably between 0.3 and 0.7. The difference in cross-sectional dimensions between the upper and lower parts of the chamber of the reactor makes it possible, during the operation of the reactor, to create a difference in the apparent velocity of the upward-flowing circulating reaction stream in the chamber of the reactor depending on whether the reaction stream is present in the upper or lower part of the chamber of the reactor. When the reactor is used in a process for dissolving solid raw materials, the lower part 220 of the chamber of the reactor, which can be called the fluidized bed zone, contains particles of solid raw materials that are undissolved or partially dissolved but larger than 1 mm in size, which are kept in a fluidized state by the reaction stream. The upper part 210 of the chamber of the reactor, which can be called the disengaging zone or separation zone, includes particles smaller than 1 mm in size resulting from the dissolution of the particles and particles larger than 1 mm in size, which will settle out and flow towards the lower part of the chamber of the reactor. Thus, due to the structure of the reactor according to the invention, the reaction stream withdrawn via the withdrawal means contains only particles of solid raw materials smaller than 1 mm and thus is easy to transport or pump. The dissolution reactor can thus be connected to a reaction zone capable of converting a portion of the withdrawn reaction stream under operating conditions more severe than those used during the dissolution of the solid raw materials, making it possible to thermally decompose the particles of solid raw materials smaller than 1 mm and, when the solid raw materials used are based on old tires, to obtain carbon black and a liquid fraction containing hydrocarbon compounds, which hydrocarbon compounds can then be upgraded.

[0038] The liquid solvent enables at least partial dissolution of the solid raw material. The liquid solvent is preferably a hydrocarbon fraction which advantageously contains from 15% to 80% by weight of aromatic compounds relative to the total weight of the solvent. Preferably, the liquid solvent contains less than 10% by weight of hydrocarbon compounds having a boiling point below 250 °C and less than 10% by weight of hydrocarbon compounds having a boiling point above 520 °C relative to the total weight of the liquid solvent. Preferably, the liquid solvent contains at least 90% by weight of hydrocarbon compounds having a boiling point between 300 °C and 500 °C. The liquid solvent can consist entirely or at least in part of an external solvent. For example, the liquid solvent can at least in part come from heavy coker gas oil (HCO or heavy recycle oil).

[0039] The liquid solvent can consist at least in part of a portion of the reaction stream withdrawn from the upper part 210 of the chamber of the reactor and recycled in the lower part 220 via a recycle loop.

[0040] In Figure 1 the embodiment shown, the liquid solvent is supplied via an introduction device 4 located in the lower part 220 of the chamber 1 of the reactor. In Figure 2 and 3 the embodiment shown, the solvent is supplied via the introduction device 4 into the loop for recycling the reaction stream. The solvent is injected into the reactor via a device 5 for introducing at least a portion of the withdrawn reaction stream. In an embodiment according to Figure 3 the introduction device 4 is upstream of a heat exchanger 280 located in the recycle loop, enabling reheating of the withdrawn reaction stream and thus reheating it before introducing the liquid solvent to be supplied into the reactor.

[0041] The reactor according to the invention comprises a device 2 for introducing the solid raw material located in the upper part 210 of the chamber 1 of the reactor.

[0042] In an embodiment according to the invention, as Figure 2 shown, the device 2 for introducing the solid raw material is located at the top of the chamber 1 of the reactor. The solid raw material can thus be fed into the reactor via a valve system, enabling control of the flow rate of the solid raw material entering the reactor. In Figure 2 the embodiment, the reactor further comprises a deflector 230 located above the withdrawal device 6 for withdrawing a portion of the reaction stream, thereby enabling diversion of the stream of solid raw material entering the reactor via the introduction device 2.

[0043] In another embodiment according to the invention, as Figure 3As shown, the device 2 for introducing solid raw materials is located at the edge of the upper part 210 of the chamber 1 of the reactor. The solid raw materials are thus fed into the reactor through a screw feeding system (screw feeder), enabling the flow rate of the solid raw materials entering the reactor to be controlled. In this embodiment, the reactor may include at least one grid 250, preferably a plurality of grids, which are located in the upper part 210 of the chamber 1 of the reactor along the vertical axis, between the wall of the chamber 1 of the reactor and the device 6 for withdrawing the reaction stream. Advantageously, the bottom of the grid 250 is located at a height lower than the inlet of the withdrawal device 6. The grid 250 enables the solid raw materials entering the reactor to be accommodated and prevents them from being directly withdrawn through the device 6 for withdrawing a part of the reaction stream.

[0044] The circuit for recycling the reaction stream by the reactor according to the present invention includes a device 6 for withdrawing a part of the reaction stream located at the level of the upper part 210 of the chamber 1 and a device 5 for introducing at least a part of the withdrawn reaction stream located at the level of the lower part 220 of the chamber 1. The withdrawal device 6 enables a part of the reaction stream to be withdrawn, which contains a liquid solvent and the liquid phase from the dissolution of the solid raw materials in the reactor, as well as at least a part of the dissolved solid raw materials entrained by the upward flow of the reaction stream. During the process of using the reactor in the method for dissolving solid raw materials, the withdrawal device 6 must be located below the upper part 210 of the chamber 1 of the reactor and the gas-liquid interface 240. Preferably, the withdrawal device 6 is axially located at the center of the cross-section of the upper part 210 of the chamber 1 of the reactor. At least a part of the withdrawn reaction stream is recycled in the lower part 220 of the chamber 1 of the reactor through the introduction device 5, which enables the amount of solvent introduced into the reactor to be limited to achieve a reaction stream flow rate that can fluidize the larger particles of the solid raw materials in the lower part 220 of the reactor.

[0045] According to an embodiment of the present invention, as Figure 2 and 3 shown, the upper part 210 and the lower part 220 of the chamber 1 are connected by a frustoconical element 260 that opens upward along the vertical axis. Preferably, the half-cone angle formed by the cross-section of the frustoconical element 260 and the vertical axis is between 7° and 45°, preferably between 10° and 30°.

[0046] The reactor according to the invention can thus be used in a process for dissolving a solid feedstock based on a thermosetting material, preferably old tyre granules, in the presence of a liquid solvent, the size of the solid feedstock being between a first minimum value and a second maximum value, for example between 1 and 25 mm, and the liquid solvent being capable of dissolving the solid feedstock. If it is desired to minimize the conversion of hydrocarbon compounds present in the reaction stream during the dissolution phase, the process is advantageously carried out at a temperature between 150 °C and 350 °C. Preferably, the process is carried out at a temperature between 200 °C and 320 °C, more preferably between 250 °C and 320 °C. The process according to the invention comprises at least the following steps: - introducing the liquid solvent into chamber 1 of the reactor so as to completely immerse the lower part 220 of chamber 1 and partially immerse the upper part 210 of chamber 1, creating a gaseous headspace above the reaction stream; - introducing the solid feedstock into the upper part 210 of chamber 1 of the reactor; - removing a portion of the reaction stream located in the upper part 210 of chamber 1; - discharging at least a portion of the removed reaction stream from the process; - recycling at least a portion of the removed reaction stream in the lower part 220 of chamber 1; wherein the superficial velocity of the reaction stream in the upper part 210 is fixed at a value lower than the free settling velocity calculated for particles of size equal to the first minimum value, and the superficial velocity of the reaction stream in the lower part 220 is fixed at a value higher than the minimum fluidization velocity calculated for particles of size equal to the first minimum value, it being understood that the superficial velocities in the upper and lower parts are different.

[0047] As mentioned above, the difference in cross-sectional dimensions between the upper and lower parts of the chamber of the reactor makes it possible, during operation of the reactor, to create a difference in the superficial velocity of the circulating reaction stream flowing upwards in the chamber of the reactor, depending on whether the reaction stream is present in the upper or lower part of the chamber of the reactor.

[0048] The superficial velocity of the reaction stream in the lower part 220 must be greater than the minimum fluidization velocity of the largest old tire particles contained in said reaction stream. The minimum fluidization velocity is a characteristic well-known to those skilled in the art and depends on the size of the particles, the density of the particles in the reaction stream, the density of the liquid, and the viscosity of the liquid contained in the reaction stream. For example, for tire particles with a diameter of 20 mm, the minimum fluidization velocity generally ranges from 1 to 15 cm / s, preferably from 3 to 10 cm / s. If the size of the particles decreases, the minimum fluidization velocity decreases; thus, the velocity of the reaction stream in the lower part of the chamber of the reactor must be greater than the minimum fluidization velocity of the largest particles to ensure sufficient mixing of the particles under fluidization. Therefore, the superficial velocity of the reaction stream located in the lower part 220 is advantageously between 2 and 15 cm / s, more preferably between 5 and 10 cm / s.

[0049] The superficial velocity of the reaction stream in the upper part 210 must be less than the free settling velocity of the largest particles, which can thus be entrained in said reaction stream. The free settling velocity characterizes the minimum velocity that the particles can withstand to be entrained in a vertical flow. This characteristic is well-known to those skilled in the art and depends on the size of the particles, the density of the particles in the liquid stream, the density of the liquid, and the viscosity of the liquid contained in the reaction stream. For example, for tire particles of 1 mm, the free settling velocity in the reaction stream is generally greater than 1 cm / s. To avoid entraining particles larger than 1 mm, the upper part 210 is advantageously dimensioned such that the superficial velocity of the reaction stream in said upper part is less than 1 cm / s, preferably less than 0.5 cm / s.

[0050] Preferably, the solid raw material is introduced into the gaseous headspace located in the upper part 210 of the chamber 1 of the reactor. Thus, the solid raw material flows by gravity into the gas phase before entering the liquid phase containing the reaction stream. Advantageously, an inert gas is introduced into the chamber of the reactor together with the solid raw material to avoid any heating caused by the convection of the solid raw material supplied via the introduction device 2, and this further enables the passage of the solid raw material in the introduction device to be promoted. The discharge device 3 located at the top of the chamber of the reactor enables the discharge of an appropriate amount of the gas fraction.

[0051] In the process of implementing the method according to the present invention, a part of the reaction stream located in the upper part 210 of the chamber 1 is taken out. The taking out is carried out via a taking-out device 6, which enables at least a part of the reaction stream to be discharged. The reaction stream contains a liquid solvent, a dissolved liquid from a solid raw material, and a part of the solid raw material, the size of which is preferably less than 1 mm. At least a part of the taken-out reaction stream is discharged from the method via a discharge device 7 located in a recirculation loop, and another part of the reaction stream is recirculated in the lower part 220 of the chamber 1 of the reactor via an introduction device 5. Advantageously, the taken-out reaction stream is heated via a heat exchanger 280 before being re-introduced into the chamber of the reactor. Advantageously, an additionally contributed liquid solvent can be introduced into the circulation loop via the introduction device 4 in order to be mixed with the taken-out reaction stream before being fed into the chamber of the reactor (see Figure 2 and 3 ). Preferably, the device 4 for introducing the liquid solvent is located upstream of the heat exchanger 280.

[0052] Preferably, the residence time of the solid raw material in the lower part 220 of the chamber of the reactor is from 15 minutes to 20 hours, preferably from 15 minutes to 3 hours, in order to be able to dissolve the particles of the solid raw material.

[0053] Preferably, the volume fraction occupied by the solid raw material in the lower part 220 of the chamber 1 of the reactor is from 10% by volume to 50% by volume, preferably from 15% by volume to 30% by volume, so as to be low enough to avoid any risk of reactor blockage caused by the accumulation of particles of the solid raw material.

[0054] The void ratio can be adjusted by changing the superficial velocity of the liquid in the section S2 of the lower part 220 of the chamber 1.

[0055] Using a part of the recirculated reaction stream as a liquid solvent enables the use of a very limited amount of external solvent. This is because, relative to the amount of particles of the solid raw material to be dissolved, the minimum amount of solvent required to operate the dissolution system without recirculating the reaction stream is greater than 3 wt / wt, and in fact is even between 4 and 5 wt / wt in order to be able to dissolve the solid raw material without the risk of blocking or clogging the reactor. In the case of the method according to the present invention, the weight ratio of the liquid solvent to the solid raw material is less than 2.5 wt / wt, preferably less than 2 wt / wt.

[0056] Figure 4 An exemplary embodiment of the reactor according to the present invention in the method of solvent decomposition of solid raw materials provided in the form of used tire particles is shown.

[0057] The particles 1a to be recycled are stored in a silo 100 before being introduced into the dissolution reactor 200 according to the invention via an introduction device 2, where they come into contact with a hydrocarbon fraction as a liquid solvent via line 4a, which hydrocarbon fraction is generated in situ by the products of a separation solvent decomposition process. Depending on the operating pressure of the dissolution reactor, other available silos may be provided upstream of the silo 100, and the particles to be recycled are circulated between said silos, which makes it possible to ensure the pressurization of the last silo feeding the reactor. The dissolution stage is carried out at a temperature between 150 °C and 350 °C in order to minimize the conversion of the liquid hydrocarbon fraction present and the pressure is adjusted to minimize the evaporation of said hydrocarbon. It is also possible to use at least partially an external solvent as described above. A part of the reaction stream is withdrawn via line 6a, which reaction stream comes from the dissolution of the particles in the dissolver and contains only particles with a size smaller than 1 mm, which particles are the residue of the dissolution stage. A part of the withdrawn reaction stream is recycled in the dissolution reactor 200 according to the invention via line 5a, and another part of the withdrawn reaction stream is discharged from the dissolution reactor via line 7a and introduced into a conversion reactor 300 operating at a temperature between 350 °C and 420 °C, preferably between 380 °C and 400 °C, in order to promote the thermal cracking reaction of said hydrocarbon so that it can be converted without producing an excessive amount of very light gas fractions. The pressure in this reactor is controlled to keep most of the hydrocarbon in the reactor 300 in liquid form, usually more than 50% by weight of the input feedstock, preferably more than 80% by weight of the input feedstock. The gaseous effluent 8 obtained is then cooled in a condensation and separation zone 400 to obtain a liquid effluent 18 and an effluent 17 of non-condensable fractions. The liquid fraction 9 leaving the reactor 300 contains the carbon black initially contained in the particles of the initial solid feedstock, and it has been found that said carbon black is completely released under the action of the dissolution and thermal cracking reactions. The carbon black consists essentially of very fine individual or aggregated particles in the micron or submicron range, with a size not exceeding 50 - 100 μm. The liquid fraction 9 is sent to a filtration zone 500, which makes it possible to separate these particles and produce a particle-free filtrate 10 and a filter cake 21 still impregnated with hydrocarbon compounds, which is then sent to a washing zone 700 in the presence of light external solvents 22, 23 such as acetone, toluene or xylene. The solvent and the hydrocarbon compounds are separated in a separation zone 800, for example by distillation. After the separation stage, the solvent can be recycled via line 24 upstream of the washing zone, and the recovered hydrocarbon compounds can be sent together with the filtrate via line 11 to a distillation zone 600 to produce a hydrocarbon fraction 12, 14 with a boiling point set by the operator. The solvent used in the dissolution reactor 200 according to the invention can consist of a part 20 of the liquid fraction leaving the top of the reactor 300, or of a part of the liquid fraction recovered at the bottom of the reactor 300 after filtration 500 (i.e. fractions 13 and 16).The remaining fractions 19, 27, and 15 can be upgraded in other external methods. Example

[0058] The aim of the following examples is to show the advantages of the reactor according to the invention by comparing the size of such a reactor with an apparatus using two fully stirred reactors operating sequentially in a closed mode (batch mode).

[0059] Example 1: Reactor According to the Invention Consider a dissolution reactor that enables the processing of used tire particles at a capacity of 15 kt per year. The size of the particles is between 10 and 15 mm. The reactor according to the invention is the reactor as Figure 3 described therein.

[0060] The dissolution reactor according to the invention exhibits the following structural characteristics: - The diameter of the lower part 220 = 1.44 m - The height of the lower part 220 = 5.76 m - The diameter of the upper part 210 = 2.88 m - The height of the liquid in the upper part 210 = 3 m - The height of the deflector 230 = 1.98 m.

[0061] The total volume of the dissolution reaction zone occupied by the reaction stream is 36.4 m 3 .

[0062] For a solubility of 2.5 (defined as the ratio of the solvent flow rate to the tire particle flow rate), the input tire flow rate is 1.875 t / h (8000 h / year) and the solvent flow rate is 4.688 t / h. By recycling a part of the dissolved product, the flow rate of the recycled reaction stream supplied to the base of the lower part is approximately 200 t / h. Under these conditions, the withdrawn reaction stream consists of a liquid phase with a viscosity of approximately 13 cSt at 100 °C and a concentration of its particles (carbon black and partially dissolved tire particles with a size less than 1 mm) of approximately 10 vol%.

[0063] For a higher solubility of 5.5 (the ratio of the solvent flow rate to the tire particle flow rate), the input tire flow rate is 1.875 t / h (8000 h / year) and the solvent flow rate is 9.375 t / h. By recycling a part of the dissolved product, the flow rate of the recycled reaction stream supplied to the base of the lower part is approximately 200 t / h. Under these conditions, the withdrawn reaction stream consists of a liquid phase with a viscosity of approximately 9 cSt at 100 °C and a concentration of its particles (carbon black and partially dissolved tire particles with a size less than 1 mm) of approximately 5.8 vol%.

[0064] Thus, the dissolution reactor according to the invention enables operation at very different solubilities, and this makes it possible to regulate the quality of the reaction stream withdrawn, which contains the target product (carbon black).

[0065] Example 2: Device Not According to the Invention The same embodiment is carried out by determining the dimensions of the unit which enables the dissolution of the same amount of used tyre particles in a well-stirred reactor. Since the effluent from the well-stirred reactor has the nature of the contents in the well-stirred reactor, the particles contained in the well-stirred reactor must be exposed to a reaction time sufficient to dissolve them adequately. Thus, the well-stirred reactor must be operated in a closed mode, and in order to ensure equivalent continuous operation, two available reactors in parallel must be available: the first reactor is in unloading / loading operation while the second reactor is in dissolution operation and vice versa.

[0066] For such a device, the minimum cycle time to ensure wetting of the particles, increase in temperature and dissolution is at least 3 hours. Furthermore, taking into account the swelling of the particles and the gaps between the particles, the minimum amount of solvent for submerging all the particles and enabling their mechanical stirring is at least 5 times the volume amount of the particles.

[0067] Thus, 5.625 t of particles must be treated in each reactor, i.e. a volume of 5.625 m 3 The required solvent volume is thus 28.1 m 3 and the reaction zone contains a minimum volume of 33.75 m 3 in each reactor. Finally, with 2 reactors, the minimum total volume is 67.5 m 3 i.e. approximately twice the volume of the reaction stream in the case of the dissolution reactor according to the invention. Under these conditions, the reaction stream withdrawn consists of a liquid which has a viscosity of approximately 9 cSt at 100 °C and a concentration of its particles (carbon black and partially dissolved tyre particles with dimensions less than 1 mm) of approximately 5.8 % by volume, which is the same as the nature of the reactor according to the invention operating at a solubility of 5 wt / wt. However, unlike the reactor according to the invention, the well-stirred reactor cannot reduce said solubility. This is because, if the solubility is reduced in the well-stirred reactor, a portion of the particles will no longer be in contact with the solvent, which will significantly reduce the performance quality of the dissolution process.

Claims

1. A reactor for dissolving a solid feedstock based on a thermosetting material in the presence of an upward flowing reaction stream containing a liquid solvent, the solid feedstock being in the form of particles having a size between a first minimum value and a second maximum value, such as used tire particles, the solvent being capable of dissolving the solid feedstock, the reactor comprising: - A chamber (1) having an elongated shape along a vertical axis, the chamber (1) comprising an upper part (210) with a cross-section S1 and a lower part (220) with a cross-section S2, the upper part (210) being located above the lower part (220) along the vertical axis; - Means (2) for introducing the solid feedstock located in the upper part (210) of the chamber (1); - Means (4) for introducing the liquid solvent; - Means (7) for discharging at least a portion of the reaction stream from the dissolution reactor; - Means (3) for discharging a gas fraction located at the top of the chamber (1) of the reactor; The reactor is characterized in that: - The cross-section S1 of the upper part (210) of the chamber (1) is larger than the cross-section S2 of the lower part (220) of the chamber (1); and in that - The reactor further comprises a circuit for recirculating the reaction stream, the circuit comprising means (6) for withdrawing at least a portion of the reaction stream located at the level of the upper part (210) of the chamber (1) and means (5) for introducing at least a portion of the withdrawn reaction stream located at the level of the lower part (220) of the chamber (1).

2. The reactor according to claim 1, characterized in that The upper part (210) and the lower part (220) have a substantially circular cross-section, and the ratio of the diameter of the cross-section S2 to the diameter of the cross-section S1 is between 0.1 and 0.

8.

3. The reactor according to any one of claims 1 and 2, characterized in that The upper part (210) of the chamber (1) and the lower part (220) of the chamber (1) are connected by a frustoconical element (260) opening upwards along the vertical axis.

4. The reactor according to claim 3, characterized in that The half-cone angle formed by the cross-section of the frustoconical element (260) and the vertical axis is between 7° and 45°.

5. The reactor according to any one of the preceding claims, characterized in that The means (7) for discharging at least a portion of the reaction stream is located in the recirculation circuit between the withdrawal means (6) and the introduction means (5).

6. The reactor according to any one of the preceding claims, characterized in that The means (2) for introducing the solid feedstock is located at the top of the chamber (1) of the reactor.

7. The reactor according to claim 6, wherein The means (6) for withdrawing at least a portion of the reaction stream is axially located at the center of the cross-section of the upper part (210) where a deflector (230) is suspended.

8. The reactor according to any one of claims 1 to 5, characterized in that The means (2) for introducing the solid feedstock is located at the edge of the upper part (210) of the chamber (1) of the reactor.

9. The reactor according to claim 8, characterized in that It further comprises at least one grid (250) positioned along the vertical axis in the upper part (210) of the chamber (1) of the reactor, between the wall of the chamber (1) of the reactor and the means (6) for withdrawing the reaction stream, and is characterized in that the bottom part of the grid (250) is located at a height lower than the inlet of the withdrawal means (6).

10. The reactor according to any one of claims 1 to 9, characterized in that The device (4) for introducing the liquid solvent is located in the lower part (220) of the chamber (1) or directly in the circuit for recycling the reaction stream.

11. A continuous process for dissolving a solid starting material based on a thermosetting material in the presence of an upwardly flowing reaction stream containing a recycled liquid solvent in a reactor according to any one of claims 1 to 10, the solid starting material being in the form of particles having a size between a first minimum value and a second maximum value, the reactor being operated at a temperature between 150 °C and 350 °C, the process comprising at least the following stages: - introducing the liquid solvent into the chamber (1) of the reactor so as to completely immerse the lower part (220) of the chamber (1) and partially immerse the upper part (210) of the chamber (1), forming a gaseous headspace above the reaction stream; - introducing the solid starting material into the upper part (210) of the chamber (1) of the reactor; - withdrawing a portion of the reaction stream located in the upper part (210) of the chamber (1); - discharging at least a portion of the withdrawn reaction stream from the process; - recycling at least a portion of the withdrawn reaction stream in the lower part (220) of the chamber (1); wherein the superficial velocity of the reaction stream in the upper part (210) is fixed at a value lower than the free settling velocity calculated for particles having a size equal to the first minimum value, and the superficial velocity of the reaction stream in the lower part (220) is fixed at a value higher than the minimum fluidization velocity calculated for particles having a size equal to the first minimum value, it being understood that the superficial velocities in the upper and lower parts are different.

12. The process according to claim 11, wherein the minimum value is equal to 1 mm and the maximum value is equal to 25 mm.

13. The process according to any one of claims 11 and 12, wherein the superficial velocity of the reaction stream in the upper part (210) is less than 1 cm / s.

14. The process according to any one of claims 11 to 13, wherein the superficial velocity of the reaction stream in the lower part (220) is between 2 and 15 cm / s.

15. The process according to any one of claims 11 to 14, wherein the residence time of the solid starting material in the lower part (220) of the chamber of the reactor is between 15 minutes and 20 hours.

16. The process according to any one of claims 11 to 15, wherein the solid starting material is introduced into the gaseous headspace located in the upper part (210) of the chamber (1).

17. The process according to any one of claims 11 to 16, wherein the weight ratio of the liquid solvent to the solid starting material is less than 2.5 weight / weight.

18. The method according to any one of claims 11 to 17, characterized in that The solid starting material is a starting material based on old tyre particles.

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