FR3105204A1 - Heat exchanger reactor - Google Patents

Abstract

The invention relates to a heat exchanger reactor (1) which comprises: - a reactive chamber (10) which accommodates the hot tubes (14C) of a circulation duct (14), the hot tubes (14C) comprising at their level top end (14H) a top opening (15H) facing a through passage (11P) formed in an upper section (11) of the reactive chamber (10); - an upper chamber (16) maintained at a higher pressure Ps at the pressure Pi, disposed against the upper section (11), and from which the swabs (18) held integrally to one another each pass through one of the through passages (11P), each swab (18) being associated with one of the hot tubes (14C) and is arranged to effect a movement between a high position and a low position in the hot tube with which it is associated in order to scrape the internal wall thereof. Figure for the abstract: Figure 2.

Description

Heat exchanger reactor

The invention relates to the field of supercritical water gasification devices (GESC) of organic or synthetic carbonaceous material, more specifically the supercritical water gasification of a co-digestate, for example resulting from the methanization of a mixture of FOr (Residual Organic Fraction), sewage sludge and possibly horse manure.

In particular, the present invention relates to a supercritical water gasification device provided with a system for cleaning tubes likely to be the seat of the supercritical water gasification reaction.

The supercritical water gasification of wet biomass, comprising for example more than 70% water and today well known to those skilled in the art and is extensively described in the literature.

This technique makes it possible in particular to treat, in one or more tubes of a supercritical water reactor, aqueous effluents which comprise organic matter and mineral matter. Supercritical water gasification in this respect transforms the organic matter into a gaseous mixture, called "syngas", which includes in particular the following gaseous species: CH ₄ , H ₂ , CO ₂ , CO.

The mineral matter, which is inert with regard to the gasification process, accumulates in the gasification reactor and in particular on the internal walls of the tubes of the said reactor.

These mineral deposits on the internal walls of the tubes limit heat transfer to the tubes, which are nevertheless necessary for the proper functioning of the gasification of organic matter into supercritical water. This results in a loss of yield from the treatment of the aqueous effluent. The accumulation of mineral matter can ultimately clog the tubes, and consequently render the supercritical water reactor inoperative.

In order to overcome these problems, a reactor with reverse flow has been proposed as described in document [1] cited at the end of the description. This reactor notably comprises two distinct zones in terms of temperature (600° C. and 300° C.), referred to as the hot zone and the cold zone respectively. In particular, the hot zone functions as a perfectly stirred reactor and comprises, in its upper part, an injection nozzle for the aqueous effluent as well as a means of evacuating the gaseous species. This arrangement imposes recirculation of the effluent and/or gaseous species in the volume of the reactor. During this recirculation, the mineral matter precipitates in the form of salts and falls by gravity into the cold zone of the reactor where it is dissolved.

However, this solution is not completely satisfactory.

In fact, part of the precipitated mineral matter is deposited on the internal wall of the reactor. By accumulation effect, this phenomenon leads to clogging of the reactor.

Thus, alternatively, and as described in document [1] cited at the end of the description, the reactor may comprise so-called transpiring walls. In particular, this document describes a reactor whose internal wall is covered with a transpiring layer provided with a network of 3D channels in which the effluent circulates at a temperature below the supercritical temperature of water. During this flow, the deposition of mineral matter on the wall of the reactor remains limited. However, this arrangement is not satisfactory. Indeed, the implementation of the transpiring layer complicates the supply of heat necessary for the supercritical water gasification reaction.

A reversible flow tubular reactor has also been proposed. This reactor comprises a tube provided with two distinct zones in terms of temperature. In particular, the tube comprises two reaction zones respectively in supercritical water conditions and in subcritical water conditions separated from each other by heat exchange zones. In this type of reactor, the thermal and reaction fluids always circulate against the current but their direction of flow is regularly reversed. Thus, the mineral matter which has precipitated in the hot zone redissolves when the flow is reversed. However, in this type of reactor, the thermal inertia of the system during flow reversal impacts the energy balance of the process.

It was also considered to implement in a reactor a flow of the aqueous effluent at high speed. Indeed, the increase in shear forces compared to the attractive forces makes it possible to limit the deposit of mineral matter on the wall of the reactor. The flow velocities involved depend on the sizing of the reactor and the rheological properties of the aqueous effluent. Speeds of the order of 1 m/s to 5 m/s in a horizontal reactor 6.7 mm in diameter have been reported. Under these conditions, only 10% to 15% of all the particles are deposited on the walls. However, in order to maintain the required residence time at these flow velocities, the tubular reactor must have a length of 144 m.

Rinsing solutions during maintenance periods advantageously make it possible to eliminate the mineral matter liable to precipitate on the walls of the reactor. However, these solutions involve discontinuous operation of the reactor.

It is also possible to carry out the supercritical water gasification of an aqueous effluent in the presence of non-adherent solid particles, such as sand, silica, or ceramics, whose contact surface is greater than that walls. Under these conditions, the mineral matter is preferentially deposited on the particles. Complementarily or alternatively, additional salts may be added. The latter are in particular intended to form, with the mineral material, eutectics whose melting temperature is lower than the operating temperature. The choice of salts nevertheless remains delicate and must be adapted to the composition of the effluent to be treated.

The limitation of the deposit of mineral matter can also be obtained by implementing tangential filtration. Thus, the gasification reaction of the aqueous effluent is implemented in an annular space formed between two concentric tubes called the inner tube and outer tube respectively. More particularly, the bottom of the inner tube is replaced by a filter, and in particular sintered metal.

The solutions known from the state of the art, although for certain industrial implementations, do not make it possible to avoid periodic cold rinsing of the reactor concerned.

An object of the present invention is therefore to propose a supercritical water gasification reactor associated with a scraping device making it possible to scrape the tubes effectively.

The objects of the invention are, at least in part, achieved by a heat exchanger reactor which comprises:
- a reactive chamber, maintained at a pressure Pi, which houses in its volume a main circulation conduit, said conduit comprises, a hot section of the volume of the reactive chamber, a bundle of so-called hot tubes, and parallel to each other, the tubes hot comprising at one of their ends, called the high end and opposite a low end, a high opening each opposite a through passage provided in an upper section of a wall delimiting the reactive chamber, said wall comprising besides a lower section, and a side section connecting said upper and lower sections;
- an upper chamber maintained by hydraulic means at a pressure Ps greater than the pressure Pi, arranged in the extension of the reactive chamber against the upper section, and from which swabs held integrally with each other cross each of the crossing passages , each swab being associated with one of the hot tubes and is arranged to perform a movement between a high position and a low position in the hot tube with which it is associated in order to scrape the internal wall thereof.

The swabs can be arranged to limit the leakage of liquid (water) from one of the upper and reactive chambers to the other of said chambers. However, if leaks should occur, the only consideration of a pressure Ps greater than the pressure Pi makes it possible to limit the latter to a flow of fluid from the upper chamber to the reactive chamber.

According to one mode of implementation, the swabs are sized so that during the movement from the high position to the low position of said swabs, a flow of a fluid from the upper chamber to the hot tubes is allowed.

According to one mode of implementation, each swab comprises a rod at the end of which is arranged a scraping means.

A “scraping means” is a means intended to scrape the internal wall of the hot tubes. In particular, the scraping means can comprise at least one of the elements chosen from: a brush, a smooth cylinder, a corrugated cylinder.

According to one mode of implementation, each hot tube comprises, at its upper end, a convergent shoulder limiting the upper opening to the diameter of the rod of the swab with which said tube is associated, the scraping means has a shape cylindrical with a diameter greater than the diameter of the rod, so that said scraping means bears against the converging shoulder when the swab is in the high position.

According to one mode of implementation, the swabs pass through each of the crossing passages by adjustment.

The fit is particularly slippery, and lets fluid pass from the upper chamber to the reactive chamber.

According to one mode of implementation, tubular interfaces are arranged in the extension of the hot tubes at their upper end and partly cross the through passages.

According to one mode of implementation, the integral maintenance of the swabs is ensured by a piston housed in the internal volume of the upper chamber and at the level of which the movement of the swabs from the high position to the low position, and vice versa, is induced by the hydraulic means.

According to one mode of implementation, the hydraulic means comprises two so-called tappings, respectively top tapping and bottom tapping, formed in a wall of the upper chamber, and from which water is injected or pumped so as to induce a movement of the plunger.

According to one mode of implementation, the hydraulic system comprises a water pump and a pipe system associated with a set of four valves.

According to one mode of implementation, a collection chamber is arranged bearing against the lower section, the hot tubes passing through said lower section at the level of lower openings made in the lower section so that a section of said hot tubes opens into the collection chamber.

According to one mode of implementation, the collection chamber comprises an outlet valve.

According to one mode of implementation, the collection chamber comprises a second tapping arranged to inject water into said chamber.

According to one embodiment, the main circulation conduit also comprises a so-called cold portion formed by cold tubes parallel to the hot tubes and arranged in a cold section of the reactive chamber and adjacent to the hot section.

According to one mode of implementation, the lateral section comprises a third bottom tapping and a third top tapping, respectively, for supplying aqueous effluent from the main circulation conduit and for discharging effluent from the main circulation conduit.

According to one mode of implementation, said device comprises a heating duct intended to heat the main circulation duct.

According to one mode of implementation, the heating conduit comprises hot tubular sections arranged coaxially with the hot tubes.

According to one mode of implementation, the lateral section comprises a fourth top tapping and a fourth bottom tapping, respectively, for supplying hot fluid to the heating duct and discharging said fluid from the heating duct.

Other characteristics and advantages will appear in the following description of a heat exchanger reactor according to the invention, given by way of non-limiting examples, with reference to the appended drawings in which:

is a schematic representation according to a longitudinal sectional plane of the heat exchanger reactor according to a first variant of the present invention;

is a schematic representation according to a longitudinal sectional plane of the heat exchanger reactor according to another aspect of the present invention;

is a schematic representation of the upper ends of hot tubes implementing tubular interfaces according to a second variant of the present invention;

is a schematic representation of the hydraulic means implemented in the context of the present invention;

is a schematic representation of a collection chamber attached to the reactive chamber according to the present invention.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

The same elements have been designated by the same references in the various figures and, moreover, the various figures are not drawn to scale. For the sake of clarity, only the elements which are useful for understanding the embodiments described have been represented and are detailed. In particular, the implementation of supercritical water gasification is not detailed.

In the description which follows, unless otherwise indicated, when reference is made to qualifiers of absolute position, such as the terms "high", "low" etc., or relative, such as the terms "upper", "lower ", etc., or to qualifiers of orientation, such as the terms "horizontal", "vertical", "lateral", etc., reference is made to the orientation of the corresponding figures, it being understood that, in the practice, the devices described can be oriented differently. Unless specified otherwise, the expressions “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably within 5%.

Figures 1 and 2 illustrate an example of a heat exchanger reactor 1 used for the gasification of biomass, and in particular of a co-digestate, into supercritical water.

“Co-digestate” means a mixture of digestate and sewage sludge.

By “digestate” is meant a residue from the process of methanization of natural organic materials or organic waste products.

The heat exchanger reactor 1 comprises in particular a reactive chamber 10 maintained at a pressure Pi, for example between 250 bars and 300 bars, and at a temperature T greater than 374°C.

It is understood, without it being necessary to specify it, that the maintenance of the chamber at the pressure Pi is ensured by the presence of a fluid, in particular water, at the pressure Pi in the volume delimited by the wall of said chamber.

The reactive chamber 10 comprises an envelope formed by a wall delimiting the volume V of said chamber 10. More particularly, the wall of the heat exchanger reactor 1 comprises an upper section 11 and a lower section 12 connected by a lateral section 13. The reactive chamber 10 may be essentially cylindrical in shape, and have an axis of elongation or of revolution XX'.

The reactive chamber 10 comprises a hot section 10C which houses a bundle of tubes called hot tubes 14C, of a main circulation conduit 14 bathed in the fluid at the pressure Pi. The hot tubes 14C are parallel to each other, and extend along the axis XX' between a lower end 14B and an upper end 14H. The hot tubes, which are heated to a temperature above 370°C, are intended to be the seat of a supercritical water gasification reaction of an aqueous effluent which comprises organic matter and mineral matter and circulating in the main circulation channel. The reaction of gasification in supercritical water in particular transforms organic matter into gaseous species, while mineral matter, inert with regard to this reaction, is not transformed.

It is understood that the hot tubes 14C are connected two by two, for example laterally by transverse tubes 14T, so that the main circulation duct 14 forms a continuous duct.

The hot tubes 14C also include, at their top end 14H, a top opening 15H. More specifically, each top opening 15H faces a through passage 11P provided in the upper section 11 of the wall delimiting the reactive chamber 10.

The heat exchanger reactor 1 also comprises an upper chamber 16, maintained by hydraulic means 17 (FIG. 4), at a pressure Ps, and arranged in the extension of the reactive chamber 10 against the upper section 11. The pressure Ps is greater than the pressure Pi, and advantageously so that the difference between these two pressures is less than 10 bars, even more advantageously less than 5 bars, for example less than 1 bar. The pressure Ps is in particular ensured by the presence of a fluid at said pressure. Furthermore, said fluid is also maintained at a temperature below the supercritical transition temperature of water.

In particular, the upper chamber 16 may in particular comprise a tank 16E provided with a bottom 16F surmounted by a side wall 16L. The tank 16 may in particular comprise, at its edge, a circumferential ring 16D making it possible to fix said tank to the reactive chamber 10, for example by means of nuts (FIG. 3).

The positioning of the tank 16 against the upper section 11 is carried out in such a way as to guarantee the overall tightness of the heat exchanger reactor 1.

The heat exchanger reactor 1 also comprises swabs 18 held firmly to each other.

Furthermore, according to the present invention, the swabs each pass through one of the passages passing through 11P from the volume of the upper chamber 15H. In particular, each swab 18 is associated with one of the hot tubes 14C and is arranged to perform a movement between a high position and a low position in the hot tube 14C with which it is associated in order to scrape the internal wall thereof.

In particular, the swabs 18 are arranged to, when they are in the high position, allow the circulation of an aqueous effluent in the main circulation conduit. In other words, the 18 swabs are recessed from the 14T cross tubes.

According to a first advantageous variant illustrated in FIGS. 1 and 2, the swabs pass through each of the crossing passages 11P by adjustment.

By "traverse by adjustment" is meant a sliding adjustment between the passages and the swabs.

The person skilled in the art is able to carry out this adjustment of the through passage with regard to the shape and size of the swabs with his general knowledge alone.

According to a second variant illustrated in FIG. 3, tubular interfaces 20 are arranged in the extension of the hot tubes 14C at their upper end 14H and partly pass through the through passages 11P.

In particular, the tubular interfaces 20 are fixed in a sealed manner to the hot tubes 14C, and extend from the upper end 14H and partly cross the through passages 11P. It is understood that according to this arrangement each swab 18 passes through a tubular interface 20. Furthermore, each tubular interface 20 is mounted in a sealed manner in the through passage that it passes through.

Insofar as leaks could occur in these two upper and reactive chambers, the consideration of a pressure Ps greater than the pressure Pi, makes it possible to limit said leaks to the sole passage of fluid from the upper chamber to the reactive chamber.

This last aspect makes the scraping system by swabs 18 compatible with operation in supercritical water of the reactive chamber 10.

The swabs 18 also have a sufficient length to allow scraping of the internal wall of the hot tubes 14C over their entire length.

In this regard, each swab 18 may comprise a rod at the end of which is arranged a scraping means.

The scraping means can in this respect comprise at least one of the elements chosen from: a brush, a smooth cylinder, a corrugated cylinder.

The scraping means may in particular have a cylindrical shape with a diameter greater than the diameter of the rod. In particular, each hot tube 14C may comprise, at its upper end, a convergent shoulder limiting the upper opening to the diameter of the rod of the swab with which said tube is associated, so that the scraping means is supported against the shoulder converge when the swab is in the up position.

The integral maintenance of the swabs 18 is ensured by a piston 19 housed in the internal volume of the upper chamber 10C and at the level of which the movement of the swabs from the high position to the low position, and vice versa, is induced by the hydraulic means 17.

The hydraulic means 17 (illustrated in FIG. 4) may comprise two so-called tappings, respectively first top tapping 16H and first bottom tapping 16B, provided in a wall of the upper chamber, and from which is injected or pumped water from so as to induce a movement of the piston 19.

More particularly, the hydraulic means 17 comprises a water pump PM and a pipe system C1, C2, C3, and C4 associated with a set of four valves, respectively, V1, V2, V3 and V4.

More particularly, the valves V1 to V4 are mounted on the ducts C1, C2, C3, and C4 arranged to ensure movement of the piston 18 from the high position to the low position and vice versa.

In particular, the movement from the high position to the low position of the piston 19 is induced by an injection of water, by the pump PM, at the level of the first high tapping 16H via the conduit C2 and an evacuation of water by the first tapping 16B via conduit C4. This movement implies in this respect the opening of valves V2 and V4 and the closing of valves V1 and V3.

The opposite movement of the piston is induced by an injection of water, by the PM pump, at the level of the low tapping 16B via the conduit C3 and an evacuation of water by the high tapping 16H via the conduit C1. This movement implies in this respect the opening of valves V1 and V3 and the closing of valves V2 and V4.

The hydraulic means 17 can, moreover, comprise a reservoir RE allowing the hydraulic means to operate in a closed circuit.

The heat exchanger reactor 1 can also comprise a collection chamber 22 placed in abutment against the lower section 12 (FIGS. 1, 2 and 5).

The hot tubes 14 passing through the lower section 12 at lower openings 12P formed in said lower section 12 so that a section of said hot tubes 14H opens into the collection chamber.

The collection chamber is more particularly arranged so that the mineral matter falls by gravity into said collection chamber. The collection chamber may include water at a temperature below 374°C so as to dissolve said mineral matter and thus form brine.

The collection chamber 22 may include an outlet valve 22S intended to evacuate the brine likely to settle in said chamber 22.

The collection chamber 22 may also include a second tapping 22P, provided with a valve 22SP, arranged to inject water into said chamber. More particularly, the collection chamber 22 can be equipped with a regulation system making it possible to guarantee a minimum water level in said chamber.

The main circulation duct can also comprise a so-called cold portion (FIG. 2) formed by cold tubes 14F parallel to the hot tubes 14C and arranged in a cold section 10F of the reactive chamber 10 and adjacent to the hot section 10C. By cold portion, we mean a section maintained at a temperature below the supercritical transition temperature of water. Thus, the aqueous effluent circulating in this section does not undergo any gasification reaction.

The heat exchanger reactor 1 according to the present invention comprises, at the level of the lateral section, comprises a third bottom tapping 13B and a third top tapping 13H, respectively, for supplying aqueous effluent from the main circulation conduit and for discharging effluent from the main circulation conduit. More particularly, the tapping 13B and the tapping 13H are arranged, respectively, at the level of the cold section and the hot section.

The heat exchanger reactor 1 also comprises a heating conduit 23 intended to heat the main circulation conduit. In particular, the heating conduit 23 comprises hot tubular sections 23C arranged coaxially with the hot tubes 14C, and in which a hot fluid, for example supercritical water, circulates. The circulation of the hot fluid makes it possible in particular to heat the aqueous effluent at the level of the hot section. In this respect, the lateral section comprises a fourth top tapping 23H and a fourth bottom tapping 23B, respectively, for supplying hot fluid to the heating duct and discharging said fluid from the heating duct. More particularly, the stitching 3B and the stitching 23H are arranged, respectively, at the level of the cold section and the hot section. According to this arrangement, the flows of aqueous effluent and hot fluid circulate in opposite directions.

The heat exchanger reactor 1 is thus implemented for gasification into supercritical water of an aqueous effluent injected at the level of the 13H tapping. The temperature of the effluent reaches the supercritical transition temperature of water when it passes through the hot section of the reaction chamber. At this moment, the organic matter undergoes a reaction of gasification into supercritical water, while the mineral matter solidifies and falls, in part, by gravity into the collection chamber 22. Residues of solidified mineral matter however agglomerate on the internal walls of the hot tubes. The supercritical conditions imposed on said tubes nevertheless do not allow this material to redissolve in water. Shutting down the reactor and using the swabs, and in particular their movement from the high position to the low position, makes it possible to scrape the internal walls of the hot tubes and consequently push the mineral matter into the collection chamber.

The water included in the collection chamber, maintained at a temperature below the supercritical transition temperature of water, makes it possible to dissolve the mineral matter and thus form brine. The latter can then be evacuated to open the 22S valve

The heat exchanger reactor can also be provided with a water level sensor in the collection chamber. This sensor can be associated with a water injection system at the 22P tapping so as to guarantee a water level at a predetermined level. In particular, the sensor can trigger an injection of water when the water level in the collection chamber is below the predetermined level.

During the swab withdrawal phase (movement from the low position to the high position), the water contained in the collection chamber undergoes suction, and fills the hot tubes. This water, which is in subcritical conditions, can then dissolve residual mineral matter (not scraped off by the swabs) on the internal walls of the hot tubes. The significant inertia of the collection volume combined with the temperature regulation of its wall will allow rapid heating of the clear water, limiting the impact of this cleaning phase on the restarting of the reactor. The injected water can also be preheated to a temperature below the supercritical transition temperature of water in order to limit the thermal impact of this water on the hot tubes.

The hot brine evacuated by valve 22S can also be recovered.

The heat exchanger reactor thus proposed makes it possible, without requiring a complete cold shutdown phase, to clean the hot tubes. This results in a better energy balance.

Finally, the tube scraping system, and more particularly its integration into the reactor, makes it possible to guarantee better sealing of said reactor.

[1] PA Marrone, “ Supercritical water oxidation—Current status of full-scale commercial activity for waste destruction ,” J. Supercrit. Fluids, vol. 79, p. 283–288, Jul. 2013.

Claims (17)

Reactor (1) heat exchanger which includes:
- a reactive chamber (10), maintained at a pressure Pi, which houses in its volume a main circulation conduit (14), said conduit comprises, in a hot section (10C) of the volume of the reactive chamber (10), a bundle of so-called hot tubes (14C), and parallel to one another, the hot tubes (14C) comprising at one of their ends, called high end (14H) and opposite a low end (14B), a high opening (15H) each facing a through passage (11P) provided in an upper section (11) of a wall delimiting the reactive chamber (10), said wall further comprising a lower section (12), and a lateral section (13) connecting said upper and lower sections;
- an upper chamber (16) maintained by hydraulic means (17) at a pressure Ps greater than the pressure Pi, arranged in the extension of the reactive chamber (10) against the upper section (11), and from which swabs (18) held integrally with each other each pass through one of the crossing passages (11P), each swab (18) being associated with one of the hot tubes (14C) and is arranged to perform a movement between a high position and a low position in the hot tube (14C) with which it is associated in order to scrape the internal wall. A reactor according to claim 1, wherein the swabs (18) are sized such that upon movement from the high position to the low position of said swabs (18), a flow of fluid from the upper chamber (16) to the hot tubing (14C) is permitted. Reactor according to Claim 1 or 2, in which each swab comprises a rod at the end of which is arranged a scraping means. Reactor according to Claim 3, in which each hot tube comprises, at its upper end (14H), a converging shoulder limiting the upper opening (15H) to the diameter of the rod of the swab with which said tube is associated, and the scraping means has a cylindrical shape with a diameter greater than the diameter of the rod, so that said scraping means bears against the convergent shoulder when the swab is in the high position. Reactor according to one of Claims 1 to 4, in which the swabs (18) pass through each of the through passages by adjustment. Reactor according to one of Claims 1 to 4, in which tubular interfaces (20) are arranged in the extension of the hot tubes (14C) at the level of their upper end (14H) and partially cross the through passages (11P). Reactor according to one of Claims 1 to 6, in which the integral retention of the swabs (18) is ensured by a piston (19) housed in the internal volume of the upper chamber (16) and at the level of which the movement of the swabs ( 18) from the high position to the low position, and vice versa, is induced by the hydraulic means (17). Reactor according to claim 7, in which the hydraulic means (17) comprises two so-called tappings, respectively first high tapping (16H) and first low tapping (16B), formed in a wall of the upper chamber (16), and from which is injected or pumped water so as to induce a movement of the piston (19). Reactor according to Claim 8, in which the hydraulic system comprises a water pump and a control system associated with a set of four valves. Reactor according to one of Claims 1 to 9, in which a collection chamber is arranged bearing against the lower section (12), the hot tubes (14C) passing through the said lower section (12) at the level of lower openings (12P ) provided in the lower section (12) so that a section of said hot tubes (14C) opens into the collection chamber. A reactor according to claim 10, wherein the collection chamber (22) includes an outlet valve (22S). Reactor according to Claim 10 or 11, in which the collection chamber (22) comprises a second tapping (22P) arranged to inject water into the said chamber (22). Reactor according to one of Claims 1 to 12, in which the main circulation conduit also comprises a so-called cold portion formed by cold tubes parallel to the hot tubes (14C) and arranged in a cold section (10F) of the reactive chamber ( 10) and adjacent to the hot section (10C). Reactor according to one of Claims 1 to 13, the lateral section (13) comprises a third bottom tapping (13B) and a third top tapping (13H), respectively, for supplying aqueous effluent from the main circulation duct and effluent discharge from the main circulation conduit. Reactor according to one of Claims 1 to 14, in which the said device comprises a heating conduit intended to heat the main circulation conduit. A reactor according to claim 15, wherein the heating conduit comprises hot tube sections arranged coaxially with the hot tubes (14C). Reactor according to Claim 15 or 16, in which the lateral section (13) comprises a fourth top tapping (23H) and a fourth bottom tapping (23B), respectively, for supplying hot fluid to the heating conduit and discharging said fluid.