WO2020048671A1 - Thermal hydrolysis device heated by electromagnetic induction and corresponding method - Google Patents

Abstract

Device for thermal hydrolysis of sludge to be treated containing organic matter, the device comprising: means (2) for injecting sludge to be treated containing organic matter; a tubular thermal hydrolysis reactor (1) heated by electromagnetic induction, said reactor has a corrosion-resistant, abrasion-resistant and non-stick lining; means (4) for cooling hydrolysed sludge originating from said reactor to a temperature that enables the subsequent digestion of the hydrolysed organic matter that the sludge contains.

Description

 Thermal hydrolysis device heated by electromagnetic induction and corresponding method.

 1. Field of the invention

 The present invention relates to a process and a device for thermal hydrolysis, preferably continuously, but also potentially in batches, of sludges containing organic matter, mixed or not with other wastes containing organic matter.

 This sludge or waste can, for example, come from the treatment of domestic wastewater (digested or undigested sewage sludge, grease from pretreatment). They can also come from the treatment of industrial wastewater (for example the food industry), or industrial or household waste type waste containing organic matter, or come from waste materials, grease traps. The term "mud" will be used thereafter to designate this sludge or waste in the present patent application.

 2. Prior art

 Sludge from wastewater treatment, whether of domestic or industrial origin or from agriculture, can be treated biologically, in particular by anaerobic digestion.

The objective of biological treatments is to degrade the organic matter contained in this sludge. The purpose of this degradation may be to stabilize the sludge, to allow energy production (through the production of biogas) and / or to reduce the volume of sludge. However, certain organic compounds such as hemicelluloses or proteins are more difficult to degrade biologically than others and it is known that pretreatment by thermal hydrolysis makes it possible to accelerate the process of biological degradation while reducing the size of devices used for degradation. This heat treatment is generally carried out by injecting steam upstream or into a reactor maintained under a pressure of 2.7 to 15.5 bar a (absolute bar), at a temperature between 130 ° C and 200 ° C, for a predetermined period of time, in practice generally of the order of 20 to 30 minutes. Thanks to such a thermal hydrolysis treatment, the hardly biodegradable organic matter is transformed into compounds which can then be degraded biologically. In a conventional manner, this subsequent biological degradation can be done by digestion in a closed reactor operating in anaerobic mode called digester. Such anaerobic digesters can only function properly if they operate at an adequate and constant temperature, generally requiring a heating system, and if they are properly stirred. This mixing is all the easier when the sludge entering the digester is fluid, that is to say of low viscosity.

 Various types of thermal hydrolysis processes are known in the prior art. Some are implemented by treating one by one, that is to say discontinuously, batches of sludge to be hydrolyzed (operation in “batch”) while other methods are designed to allow continuous treatment, or at least semi-continuously, sludge to be hydrolyzed.

 A particularly effective sludge hydrolysis technique has been proposed, described in FR2820735A1. This technique consists in using at least two reactors operating in parallel, in “batch”, according to staggered cycles, in each of which batches of sludge undergo a complete cycle of thermal hydrolysis.

 It has also been proposed, in EP1198424A1, a process for the continuous treatment of sludges in which sludges already preheated are pumped and then again preheated in a preheating reactor before being pumped again to a thermal hydrolysis reactor and then transferred to a depressurization tank producing flash vapor.

 Such hydrolysis processes implemented by efficient hydrolysis devices have been developed by making use of the production and use of steam throughout the lysis circuit so as to allow the sludge to be subjected to a rise and then hold for a defined time at a high temperature under high pressure.

 The vapor is mainly injected directly into the mud which generates a dilution of the mud by evapo-condensation. It can also be used as a heat transfer fluid and the heat exchange is carried out via the wall of an exchanger.

However, such hydrolysis devices and methods are very expensive and energy-consuming. Indeed, for each thermal hydrolysis project, it is necessary to provide both the hydrolysis device, but also the means for generating steam, called live steam, as well as all the networks for circulation of this steam. In the case of operation according to cycles or in “batch”, to avoid the stopping phases of the steam generators and therefore to use live steam continuously, it is preferable to have at least three reactors operating in parallel.

 In addition to these drawbacks, there are constraints in terms of human resources to manage the installations, adequacy between customer needs and energy demand, and various security problems linked to the management of installations.

 Thus such drawbacks, including for example the energy consumption which can reach 1 tonne of steam per tonne of dry matter treated, make this system unsatisfactory. This dissatisfaction is all the greater for small installations.

 Other heating systems have been devised with a view to raising the temperature of the mud beyond 130 ° C. These systems consist of transferring heat by conduction from a heat transfer fluid (thermal oil, superheated water, steam, etc.) to the mud via the wall of a steel exchanger.

 However, the low transfer coefficients observed require high speeds of mud transport and a very high heat exchange surface leading to the installation of concentric exchangers of several hundred meters, or even beyond the kilometer, thus posing congestion and maintenance problems.

 Still other solutions have been devised using energy in its electrical form. The mud can for example be heated by heating resistors in contact for example with a tube in which the mud circulates.

 However, such an arrangement poses problems of speed of transfer of heat to the mud. In addition, it poses cost problems owing to the fact that electrical energy presents a non-negligible cost in view of the needs for satisfactorily heating the necessary quantity of sludge.

3. Objectives of the present invention

 The object of the present invention is to respond at least in part to some of the drawbacks of the prior art.

More particularly, an objective of at least one embodiment of the invention is to provide such a sludge hydrolysis device which has a reduced size so that it can be adapted according to the situations in which it is used. Another objective of at least one embodiment of the invention is to provide such a device which is inexpensive in energy terms while retaining the characteristics sufficient for the treatment of the sludge to be satisfactory.

 Yet another objective of at least one embodiment of the invention is to provide such a device which is simple to use and maintain, and inexpensive to implement.

 4. Statement of the invention

 All or part of these objectives are achieved thanks to the invention which relates, first of all, to a device for the thermal hydrolysis of sludge to be treated containing organic matter, the device comprising:

 means for injecting sludge to be treated containing organic matter; a tubular thermal hydrolysis reactor heated by electromagnetic induction, said reactor having an anti-corrosion, anti-abrasion, and anti-adhesion interior coating.

 means for cooling the hydrolyzed sludge coming from said reactor to a temperature allowing the subsequent digestion of the hydrolyzed organic matter which they contain.

 Thus, the invention proposes a new and inventive approach making it possible to overcome at least some of the drawbacks of the listed prior art.

 In particular, the sludge hydrolysis device implemented by the invention has a reduced size so that it can be adapted according to the situations in which it is used, owing to the fact that it eliminates the steam production installations of the prior art which generate significant bulk. Thus, the size of such a device according to the invention turns out to be limited.

 In addition, such a device turns out to be inexpensive in terms of energy while retaining sufficient characteristics for the sludge treatment to be satisfactory.

 Furthermore, such a device comprising a reactor which has an internal anti-corrosion, anti-abrasion and anti-adhesion coating makes it possible to avoid the crusting of the sludge.

According to one aspect of at least one embodiment of the invention, said interior coating is of the fluorocarbon type. Such a characteristic makes it possible to use an interior anti-corrosion, anti-abrasion, and anti-adhesion coating which is particularly effective.

 According to another aspect of at least one embodiment of the invention, said reactor heated by electromagnetic induction is made of ferritic material, such as stainless steel or preferably carbon steel.

 According to another aspect of at least one embodiment of the invention, said reactor has an external coating of acrylic paint type having a resistance of at least 350 ° C.

 According to another aspect of at least one embodiment of the invention, said reactor has a diameter less than or equal to 300 mm.

 Such a limited size of the reactor has the advantage of limiting the costs relating to the implementation of the winding, and also of limiting the risks of heating the mud by conduction being too long and inhomogeneous.

According to another aspect of at least one embodiment of the invention, the device comprises means intended to maintain the pressure in said tubular thermal hydrolysis reactor.

 According to a characteristic of at least one embodiment of the invention, said device comprises a device for preheating the sludge to be treated.

 In this way, it allows energy to be recovered.

 Such a device for preheating the sludge to be treated is a preheating exchanger more particularly useful in the case of continuous operation.

 Said means for cooling the hydrolyzed sludge coming from said reactor comprises a cooling exchanger.

 According to another aspect of at least one embodiment of the invention, the preheating exchanger comprises a water inlet communicating with a water outlet of said hydrolysed sludge cooling exchanger so as to convey the hot water from the cooling exchanger to the preheating exchanger.

 According to another aspect of at least one embodiment of the invention, the cooling exchanger comprises a water inlet communicating with a water outlet of said preheating exchanger so as to convey the cold water coming from the '' preheating exchanger towards the cooling exchanger.

According to another aspect of at least one embodiment of the invention, the preheating device comprises a preheating tank supplied with sludge to treat and recover steam, called flash steam. Flash vapor is produced in a hydrolysed sludge depressurization tank, or flash tank, placed downstream from the hydrolysis reactor.

 In this flash tank, the pressure of the hydrolysed sludge is suddenly lowered, concomitantly causing them to cool and the emission of flash vapor.

 In this case, the operation is discontinuous.

 The invention also relates to a process for the thermal hydrolysis of sludge using the device according to one of the abovementioned embodiments, said process comprising the steps consisting in:

 injecting said sludge under pressure through a preheating exchanger so as to obtain a batch of preheated sludge;

 conveying said batch of preheated sludge to a tubular pressure reactor and heating this batch of preheated sludge by electromagnetic induction;

 maintaining said batch of sludge in said reactor for a sufficient residence time and at a temperature and pressure sufficient to allow thermal hydrolysis of the organic material present in this batch;

 cooling said batch of hydrolyzed sludge at the outlet of said reactor, through a cooling exchanger, to a temperature allowing the subsequent digestion of the hydrolyzed organic matter which it contains.

 According to a characteristic of at least one embodiment of the method, it is carried out continuously.

 According to another characteristic of at least one embodiment of the process, said batch of sludge is preheated through the preheating exchanger from a temperature of approximately 20 ° C to a temperature between 20 ° C and 135 ° C, preferably between 20 ° C and 90 ° C.

 According to another characteristic of at least one embodiment of the process, said injected sludge has a dryness of between 4% and 50%, preferably between 12% and 40% by weight of dry matter, even more preferably between 16% and 20 % by weight of dry matter.

According to another characteristic of at least one embodiment of the method, the first batch of preheated sludge is heated through the preheating exchanger by means of hot water coming from the cooling exchanger. According to another characteristic of at least one embodiment of the method, said batch of sludge leaving said reactor is cooled through the cooling exchanger by means of cold water coming from the preheating exchanger.

 The sludge preheated to 80-90 ° C is heated to 130-200 ° C, preferably to about 165 ° C, by induction by direct contact with the walls of the reactor made of ferritic material, by conduction within the sludge and to a lesser extent. measurement by the expected convection in a laminar regime.

 So as to reach such a temperature for the sludge, the electrical power developed by the reactor of the invention is between 100 and 250 kW.

 More generally, the electrical power developed by the reactor can be between 50 and 400 kW, depending on its size, or energy losses for example.

According to another characteristic of at least one embodiment of the process, the pressure in the reactor is between 2.7 and 15.5 bar a, preferably between 6 and 10 bar a.

 According to another characteristic of at least one embodiment of the method, said residence time of said batch of sludge in said reactor is between 10 minutes and 2 hours, preferably between 20 minutes and 40 minutes.

 According to another characteristic of at least one embodiment of the method, the reaction temperature obtained by said heating by electromagnetic induction and the contact time are sufficient to also allow the hygienization of the sludge contained in said reactor.

 According to an alternative to the method according to an embodiment of the invention, it is carried out batchwise, the method comprising a preliminary step in which said sludge to be treated is injected into a preheating tank supplied with flash vapor so as to obtain a batch preheated sludge.

 The hydrolyzed sludge is depressurized and cooled in a flash tank.

5. List of figures

The invention and the various advantages which it presents will be more easily understood thanks to the description of embodiments given with reference to the figures in which: FIG. 1 represents a device for thermal hydrolysis by electromagnetic induction according to a first embodiment of the invention continuously;

 FIG. 2 represents in schematic form part of a thermal hydrolysis device according to a second embodiment of the invention in batch, and

 FIG. 3 represents in schematic form a thermal hydrolysis device according to a third embodiment of the invention, in batch in which the sludge is heated in the recirculation line.

 6. Detailed description of an embodiment

 We now present, in relation to FIG. 1, a first embodiment of the device for thermal hydrolysis of sludge to be treated containing organic matter.

 In this embodiment, the device comprises:

 - a preheating exchanger 3;

 - Means 2 for injecting sludge to be treated containing organic matter through said preheating exchanger;

 - a tubular thermal hydrolysis reactor 1 heated by electromagnetic induction; and,

 - means 4 for cooling the sludge coming from the reactor to a temperature allowing the subsequent digestion of the hydrolysed organic matter which they contain.

 Heating by electromagnetic induction consists in passing a magnetic field through the material of the reactor which then behaves like an electrical resistance and rises in temperature. These inductors are placed at a precise distance from the reactor (a distance called air gap) to transfer electrical power precisely into the interior of the reactor. This same reactor will go up in temperature and radiate on the winding itself which is insulated by a high performance thermal insulator.

To transfer electrical power, coils are placed around the reactor. These turns can be shaped more or less hard. For example, a hard turn solution would be to use collars. Another, more flexible solution could be to use a flexible electrical cable. Such a solution is preferred in the context of the invention.

According to the invention, the reactor has an internal anti-corrosion, anti-abrasion, and anti-adhesion coating.

 Such an internal coating makes it possible to protect the reactor from the fact that the sludges have an abrasive character (coming from the silica which they conventionally contain), corrosive (due to the presence of chlorides which attack very particularly ferric materials), and are relatively adherent. In addition, such a coating prevents crusting of the sludge introduced.

 In this embodiment, this interior coating is more particularly of the fluorocarbon type, which makes it possible to implement a coating having all these characteristics while being relatively inexpensive.

 One could for example provide a fluorocarbon coating as proposed by the companies Saint-Gobain, Nemours or Arkema, or a reformed fluorocarbon coating and applied by companies such as Accoat.

 The reactor 1 illustrated in FIG. 1 is made of carbon steel, which is a ferritic material making it possible to use a reactor heated by electromagnetic induction.

 However, other embodiments could be provided in which this reactor would be made of another ferritic material such as 430 stainless steel or another ferritic stainless steel or even another ferritic steel having the qualities of resistance to temperature and at the necessary pressure.

 Furthermore, and so as to reinforce the resistance and therefore the lifetime of the reactor 1, in particular in the event of condensation which could cause corrosion on the reactor, the latter has an external coating of acrylic paint type having a resistance of at least 350 ° C. Such a resistance thus makes it possible to use it for the thermal hydrolysis process of sludge so that it has a satisfactory service life.

For reasons of compactness of the entire device, in this continuous embodiment, the reactor 1 has a diameter less than or equal to 300 mm. Such a reactor thus makes it possible to ensure flexibility of use, assembly and maintenance of the device because of its relatively small size. In this embodiment, the preheating exchanger for the sludge to be treated 3 comprises a water inlet communicating with a water outlet from the cooling exchanger 4 so as to convey the hot water coming from the heat exchanger. cooling of the hydrolyzed sludge 4 to the preheating exchanger 3 by means of a recirculation pump 7.

 In other words, the water which has been heated in the cooling exchanger by the passage of hot sludge is conveyed from a water outlet from the cooling exchanger 4 to a water inlet from the exchanger preheating 3, so as to preheat the sludge entering this exchanger.

 As for the cooling exchanger 4, it comprises a water inlet communicating with a water outlet from the preheating exchanger 3 so as to convey the cold water coming from the preheating exchanger 3 to the exchanger cooling 4 through the recirculation pump 7.

 In this way, the water circuit is substantially closed and the heat energy stored by the water during the cooling of the sludge is reused for the preheating of the sludge entering the device, which makes it possible to limit the additional energy costs for making operate the device and therefore makes it possible to provide a device that is substantially energy efficient.

 The thermal hydrolysis process for sludge according to the invention is explained below, implementing the device described above.

 This process comprising the steps of:

 - injecting the sludge under pressure through the preheating exchanger 3 so as to obtain a first batch of preheated sludge;

 - conveying the batch of preheated sludge to the tubular reactor 1 under pressure and heating this batch of sludge preheated by electromagnetic induction;

 maintain the batch of sludge in reactor 1 for a sufficient residence time and at a temperature and pressure sufficient to allow thermal hydrolysis of the organic material present in this batch, and

 - Cooling the batch of sludge at the outlet of the reactor 1, through a cooling exchanger 4, to a temperature allowing the subsequent digestion of the hydrolysed organic matter which it contains.

In other words, the sludge is injected into the device by means of the injection means 2, at the location of the preheating exchanger 3. According to the different embodiments, this injected sludge has a dryness of between 4% and 50%, preferably between 12% and 40%.

 In the preferred embodiment illustrated, the injected sludge has a dryness of between 16% and 20%.

 This sludge is preheated through the heat exchanger to a temperature between 80 ° C and 90 ° C.

 As described above, the batch of sludge is heated through the preheating exchanger 3 by means of hot water coming from the cooling exchanger 4.

 At the outlet of the preheating exchanger 3, a first batch of preheated sludge is obtained which is conveyed to the tubular reactor 1 under pressure, preferably between 6 and 10 bar a, to heat this batch of sludge preheated by electromagnetic induction.

 Thanks to induction, the part of the reactor in which the batch of sludge preheated directly at high temperature between 130 ° C and 200 ° C, preferably around 165 ° C, is mounted. Therefore, the sludge is heated by conduction which allows faster and more efficient heating than in the prior art.

 The first part of the reactor used to heat the batch of preheated sludge is, in this embodiment, of a length approximately equal to 12 m.

 However, it could be provided that its length is between 1 m and 40 m so that the device is adaptable according to the installations.

 Once at the temperature, the sludge is kept under pressure through the second part of the reactor 1 in order to respect a residence time necessary to ensure the hydrolysis of the sludge.

 The second part of the reactor will have a sufficient length to ensure the hydrolysis reaction at pressure and temperature for 20 to 40 minutes.

 Preferably, this heating by electromagnetic induction is carried out at a temperature of at least 130 ° C., and taking into account the residence time of the sludge contained in said reactor, the hygienization of the sludge is also obtained.

In the illustrated embodiment, the residence time of the batch of sludge in the reactor 1 is between 20 minutes and 40 minutes. However, one could provide embodiments in which the residence time of the batch of sludge in the reactor 1 is between 10 minutes and 2 hours.

 Such a residence time can for example vary according to the hydrolysis needs, the size or the power of the reactor.

 Once the residence time has been ensured, the batch of sludge is cooled at the outlet of the reactor 1, through the cooling exchanger 4, to a temperature allowing the subsequent digestion of the hydrolysed organic matter which it contains.

 As indicated above, the batch of sludge leaving the reactor 1 is cooled through the cooling exchanger 4 by means of cold water coming from the preheating exchanger 3 and brought through the recirculation pump 7 .

 It should be noted that the thermal hydrolysis process can be carried out continuously. In this case, there will be no formation of several batches of sludge, the sludge flowing continuously.

 In other words, in continuous operation, the batch of sludge formed is unique, as long as the operation continues continuously.

 The pressure in the reactor is, in this embodiment, between 2.7 and 15.5 bar a.

 However, a device could be provided in which the reactor pressure is between 6 and 10 bar a.

 This pressure is maintained within the device by means of two valves:

- A first valve 5 aimed at creating a pressure drop;

 - A second valve 6 for regulating the pressure of the reactor and lowering the pressure to the desired pressure.

 An embodiment could however be provided in which a pressure maintenance pump is implemented.

 We now present, in relation to FIG. 2, a second embodiment.

 In this embodiment, the 3 ′ reactor operates in batch.

To implement energy recovery and preheat the sludge with flash steam, thermal hydrolysis in batches of sludge is carried out using several thermal hydrolysis reactors operating in parallel and according to offset cycles. Each batch of sludge then undergoes a complete cycle of thermal hydrolysis in each of the reactors. Thanks to induction heating on each reactor, there is no constraint on the continuous production of steam.

 This embodiment includes, at the input, a preheating tank 30 making it possible to mix flash water vapor with the sludges arriving from the injection means 2, in order to preheat them.

 These preheated sludges are then pressurized and injected into the reactor operating in 3 ′ batch before being heated to a temperature of approximately 165 ° C. by direct contact with the walls of the reactor and are kept in the reactor for a time of predefined stay.

 Once this time has been reached, discharge valves 33 open in order to drain the sludge into a flash tank 31 within which the pressure and the temperature of the sludge are rapidly lowered, which makes it possible to recover flash vapor for preheating sludge to be treated arriving via the injection means 2.

 In this embodiment in batch, one or more reactors having a diameter less than or equal to 300 mm can be used. These reactors are also made of ferritic material, with an interior coating of the fluorocarbon type and an exterior coating of the acrylic paint type having a resistance of at least 350 ° C.

 Such an embodiment can, for example, be used with a view to obtaining advanced class A hygienization of the USEPA.

 The sludge then leaves via the outlet means 32 in order to reach a digester in which the hydrolyzed sludge will be treated.

 We now present, in relation to FIG. 3, a third embodiment of the invention in batch with several reactors operating in parallel according to staggered cycles.

 In the illustrated embodiment, the device comprises 3 hydrolysis loops.

Obviously, other embodiments could be provided in which the number of hydrolysis loops would be different.

 In this embodiment, the means for heating the preheated sludge are placed on the sludge recirculation loop and not directly on the reactor. In this way, there is a recirculation of the sludge for heating by induction of the sludge then maintenance within the hydrolysis reactor.

Each hydrolysis loop 301 has a thermal hydrolysis reactor 302 and a sludge recirculation loop composed of tubes and a pump. The preheated sludge is sent alternately to one of the different hydrolysis loops 301, according to the operating cycle.

 At the outlet of reactor 302, the sludge is directed to a recirculation circuit, comprising an inductor, so as to be heated by induction and is sent again to the reactor by means of a pump. After the heating time, the sludge remains in the reactor, sized to ensure the hydrolysis reaction at high pressure and temperature for 20 to 40 minutes.

 The reactor used has a diameter less than or equal to 1.5 m.

 The hydrolyzed sludge which leaves the hydrolysis reactors after a predetermined time is sent to the heat exchanger 300, in order to be cooled.

 In this embodiment, the sludge is removed periodically.

 In the illustrated embodiment, the preheating of the sludge to be treated and the cooling of the hydrolysed sludge are placed within the same heat exchanger 300.

 Such a heat exchanger can for example be a water / mud exchanger, or a preheating tank coupled with a flash tank.

Claims

 1. A device for thermal hydrolysis of sludge to be treated containing organic matter, the device comprising:  injection means (2) of sludge to be treated containing organic matter; a tubular thermal hydrolysis reactor (1) heated by electromagnetic induction, said reactor having an anti-corrosion, anti-abrasion, and anti-adhesion interior coating;  means for cooling (4) the hydrolysed sludge coming from said reactor to a temperature allowing the subsequent digestion of the hydrolysed organic matter which they contain.  2. Device according to claim 1, characterized in that said inner coating is of fluorocarbon type.  3. Device according to one of claims 1 or 2, characterized in that said reactor (1) heated by electromagnetic induction is made of ferritic material, preferably carbon steel.  4. Device according to one of claims 1 to 3, characterized in that said reactor (1) has an external coating of acrylic paint type having a resistance of at least 350 ° C.  5. Device according to one of claims 1 to 4, characterized in that said reactor (1) has a diameter less than or equal to 300 mm.  6. Device according to one of claims 1 to 5, characterized in that it comprises means intended to maintain the pressure in said tubular thermal hydrolysis reactor.  7. Device according to one of claims 1 to 6, characterized in that it comprises a preheating exchanger (3) of said sludge to be treated and a cooling exchanger (4) of hydrolyzed sludge and in that the exchanger of preheating (3) comprises a water inlet communicating with a water outlet from the cooling exchanger (4) so as to convey the hot water coming from the cooling exchanger (4) to the preheating exchanger (3). 8. Device according to one of claims 1 to 7, characterized in that the cooling exchanger of said hydrolyzed sludge (4) comprises a water inlet communicating with a water outlet of said preheating exchanger (3) so at route the cold water from the preheating exchanger to the cooling exchanger.  9. Device according to one of claims 1 to 6, characterized in that it comprises a tank for preheating said sludge to be treated (30) supplied with flash vapor and in that it comprises a flash tank.  10. Process for the thermal hydrolysis of sludge using the device according to one of claims 1 to 9, said process comprising the steps consisting in:  conveying said batch of sludge to be treated to a tubular pressure reactor and heating this batch of sludge by electromagnetic induction;  maintaining said batch of sludge in said reactor for a sufficient residence time and at a temperature and a pressure sufficient to allow thermal hydrolysis of the organic material present in this batch; and,  cooling said batch of sludge at the outlet of said reactor, through a cooling exchanger, to a temperature allowing the subsequent digestion of the hydrolysed organic matter which it contains.  11. A thermal hydrolysis method according to claim 10, characterized in that it is carried out continuously, the method comprising a preliminary step in which said sludge is injected under pressure through a preheating exchanger so as to obtain a batch of preheated sludge.  12. Method according to one of claims 10 or 11, characterized in that said batch of sludge is heated through the preheating exchanger to a temperature between 20 ° C and 130 ° C, preferably between 20 ° C and 90 ° C.  13. Method according to any one of claims 10 to 12, characterized in that the pressure in the reactor is between 2.7 and 15.5 bar a, preferably between 6 and 10 bar a.  14. Method according to any one of claims 10 to 13, characterized in that said injected sludge has a dryness of between 4% and 50%, preferably between 12% and 40%, even more preferably between 16% and 20 %. 15. Method according to any one of claims 10 to 14, characterized in that the batch of sludge is preheated through the preheating exchanger by means of hot water from the cooling exchanger. 16. Method according to any one of claims 10 to 15, characterized in that said batch of sludge leaving said reactor is cooled through the cooling exchanger by means of cold water coming from the preheating exchanger . 17. Method according to any one of claims 10 to 16, characterized in that said residence time of said batch of sludge in said reactor is between 10 minutes and 2 hours, preferably between 20 minutes and 40 minutes.  18. Method according to any one of claims 10 to 17, characterized in that said heating by electromagnetic induction is carried out at a temperature of at least 130 ° C, preferably at 165 ° C, so as to allow hydrolysis sludge and the sanitation of sludge contained in said reactor.  19. A thermal hydrolysis method according to claim 10, characterized in that it is carried out batchwise, the method comprising a preliminary step in which said sludge is injected into a preheating tank supplied with flash vapor so as to obtain a batch preheated sludge.