Improved hydrothermal treatment device for organic compounds and associated process.

Abstract

TITLE: Improved hydrothermal treatment device for organic compounds and associated process. The invention relates to a process and a device (DT) for the hydrothermal treatment of organic compounds, the device being characterized in that it comprises: an oxidation reactor (RO) with inlets (ERO1, ERO2) for an oxidizing gas and a fuel gas and an inlet (ERO3) for water under supercritical conditions as well as an outlet (SRO) for water, a gasification reactor (R) configured to operate with water under supercritical conditions, the reactor comprising an inlet (ER1) connected to the outlet (SRO) of the reactor, an inlet (ER2) for bringing the mixture to be treated, containing organic compounds to be recovered, under pressure and an outlet (SR) for a treated mixture comprising dissolved gases from the organic compounds;a heat exchanger (HEI) connected to the outlet (SR) of the reactor (R), the treated mixture exiting the reactor being intended to serve as a heat source for the heat exchanger, and connected both to a pressurized water supply and to said other inlet (ERO3) of the oxidation reactor (RO), this pressurized water thus being intended to be superheated in the heat exchanger before entering the oxidation reactor. Figure for the abbreviation: Figure 1.;

Description

Title of the invention: Improved hydrothermal treatment device for organic compounds and associated process. Technical field of the invention

[0001] The present invention relates to the valorization of bio-resources and more particularly to the valorization of wet resources.

[0002] These wet resources (moisture content > 50%) represent significant energy potential that should not be overlooked compared to dry resources (moisture content < 50%: wood, dry waste, and various agricultural residues). The aim is to utilize residues from different sources: residues from the agri-food industry, agricultural residues, residues from the paper industry such as black liquor, sewage sludge and its digestate from methanization, and the organic fraction of household waste and its digestate from methanization. It may also be advantageous to utilize wet biomass, such as algae (microalgae or macroalgae).

[0003] Since these wet resources contain a significant fraction of water (commonly between 50% and 90%), the processes known for utilizing dry resources are not necessarily the best suited from an energy perspective.

[0004] That is why, for these wet resources, so-called hydrothermal processes have been proposed and are the subject of constant improvements.

[0005] Hydrothermal processes consist of converting the organic compounds contained in the wet resource (gas, oils or combustible liquids depending on the case).

[0006] In this type of process, the water present plays the role of reaction medium and reactant.

[0007] In particular, water containing the organic compounds to be recovered can be subjected to supercritical conditions (water at a temperature above 374°C and a pressure above 22.1 MPa). Under these conditions, the organic compounds are hydrolyzed and gasified (transformation of organic matter into gas). This produces energetic combustible gases (H2, CH4, C2H6, etc.) which are dissolved in the water (under high pressure).

[0008] There are different ways of bringing water into supercritical conditions.

[0009] An existing solution is to use a heat exchanger-reactor.

[0010] This generally takes the form of a shell through which a bundle of tubes passes. A boiler is used, for example, to supply heat (heat transfer fluid) to the heat exchanger-reactor, and more specifically to the shell. Water The water containing the organic compounds to be recovered (wet resource) then passes into the tubes. The heat exchange between the environment and the tubes then heats the water.

[0011] The drawback of this type of solution is related to the quality of heat transfer through the walls of the tubes used to circulate the wet resource in the heat exchanger-reactor. Indeed, the flow velocities generally observed in the tubes do not promote maximum heat transfer (laminar flow), and furthermore, the inside of the tubes can become fouled quickly depending on the nature of the wet resource being treated.

[0012] Another solution is to use a reactor (without a heat exchanger) configured to allow combustion within it. Reference may be made, for example, to document EP 3 806 995.

[0013] This bypasses the difficulties encountered with the exchanger-reactor.

[0014] More specifically, an oxidizing agent is injected to enable the combustion of some of the organic matter contained in the water or of reaction products already formed elsewhere. The oxidizing agent generally used is oxygen, which can be supplied as a stream of pure gas, a stream of air, or a stream of hydrogen peroxide. The combustion reaction thus generated provides the energy necessary to bring the water containing the organic compounds to be recovered to supercritical conditions.

[0015] The drawback of such a solution lies in the difficulty of correctly controlling the process to achieve the desired temperature conditions. Indeed, it is difficult to distinguish whether the reaction products (gases resulting from the gasification of organic compounds present in the water to be treated), or the organic compounds themselves, are consumed by the combustion reaction. It is clearly undesirable for the reaction products (gases) to be consumed predominantly, to the detriment of the organic matter injected into the reactor (to be recovered), since they are the valuable component of this type of process.

[0016] Furthermore, the combustion of the injected organic matter may not be optimal given the form in which it may be present in the process (large particles, agglomeration with inorganic matter) or due to problems of homogenization of flows or management of residence times.

[0017] Yet another solution consists of preheating a stream of pure water in a dedicated heat exchanger (which draws its heat source from combustion gases from a boiler) and then mixing this pure water stream in a gasification reactor with the stream of wet resource to be gasified. The pure water is sufficiently preheated so that the temperature of the mixture with the wet resource is compatible with optimal gasification of the organic matter present. Reference may be made to “Review of supercritical gasification with lignocellulosic real biomass as the feedstocks: process parameters, biomass composition, catalyst development, reactor design and its challenges”, Chai Siah Lee & al., Chemical Engineering Journal, vol. 415 (2021), 128837.

[0018] However, to ensure good energy efficiency, the wet resource stream to be treated is also preheated, in this case via the water stream exiting the gasification reactor and through a preheating exchanger. This preheating exchanger can be affected by significant fouling problems due to its operating conditions in terms of temperature and the nature of the wet resource being treated (presence of inorganic elements that precipitate or generation of highly viscous oil agglomerated with carbonaceous particles). This preheating exchanger can also impair the overall process efficiency if it generates organic compounds (carbonaceous particles) that are more difficult to convert into gas in the dedicated stage.

[0019] Regardless of the process considered, it should be noted that the water from the gasification process still contains, in most cases, organic species in solution. This can render the water unsuitable for discharge into the environment and also impacts the energy efficiency of the process since not all of the organic compounds have been recovered. Summary of the invention

[0020] One objective of the invention is to provide an improved hydrothermal treatment device for organic compounds.

[0021] To this end, the invention proposes a hydrothermal treatment device for organic compounds, characterized in that it comprises: - an oxidation reactor comprising: a first inlet for an oxidizing gas and a second inlet for a fuel gas, the reactor being configured to implement a combustion reaction; a third inlet for water under supercritical conditions and an outlet for this water, - a gasification reactor configured to operate with water under supercritical conditions, the reactor comprising: a first inlet connected to the outlet of the oxidation reactor, this first inlet being intended to collect the water exiting the oxidation reactor, a second inlet to supply the gasification reactor with a mixture to be treated, namely water loaded with organic compounds, under pressure, an outlet for a treated mixture, containing dissolved gases from organic compounds; - a heat exchanger connected on one side to the outlet of the gasification reactor, the treated mixture exiting the reactor being intended to serve as a hot source for the heat exchanger and on the other side, both to a pressurized water supply circuit and to the third inlet of the oxidation reactor, this pressurized water being intended to be superheated in the heat exchanger before supplying the oxidation reactor.

[0022] The device according to the invention may include at least one of the following features, taken alone or in combination: - a supply circuit for the mixture to be treated to the gasification reactor, said circuit including a booster to pressurize the mixture to be treated before its entry into the gasification reactor; - the water supply circuit for the oxidation reactor includes a booster pump to pressurize the feed water; - at least one first tank having an inlet connected to the heat exchanger so as to be able, in use, to recover the treated, pressurized and cooled mixture coming out of the heat exchanger; - the tank also includes an outlet arranged to recover gases from the treated mixture, under pressure and cooled, said outlet being connected to the second inlet of the oxidation reactor to supply said gases as fuel gas for the oxidation reactor; - a second tank connected, via a pressure regulator, to another outlet of the first tank, this other outlet being arranged to be able to recover an aqueous phase present in this first tank; - a means of withdrawal connected to an outlet of the second tank, this means of withdrawal being also connected to the pressurized water supply circuit for the oxidation reactor.

[0023] Another objective of the invention is to propose an improved hydrothermal treatment process for organic compounds.

[0024] To this end, the invention proposes a hydrothermal treatment process for organic compounds, characterized in that it comprises the following steps: A) bring water to a temperature between 550°C and 650°C and a pressure between 270 and 300 bars in an oxidation reactor; B) implement a combustion reaction in the oxidation reactor in order to bring the water to a temperature between 900°C and 1000°C; C) to transfer the heated water from the oxidation reactor to a gasification reactor, the water being maintained at a pressure between 240 and 270 bar and lower than the pressure in the oxidation reactor, and simultaneously, to supply the gasification reactor with the mixture to be treated, at to know water loaded with organic compounds, under pressure; D) recover a treated mixture exiting the gasification reactor, this mixture containing dissolved gases, to serve as a hot source for a heat exchanger which also receives water at a pressure between 270 and 300 bars to superheat it from ambient temperature to a temperature between 550°C and 650°C before it enters the oxidation reactor.

[0025] The method according to the invention may include at least one of the following features, taken alone or in combination: - during step C), the mixture to be treated is introduced at ambient temperature into the reactor at a given inlet flow rate and the water passing from the oxidation reactor to the gasification reactor is introduced at a flow rate 3 to 4 times greater than the given inlet flow rate of the mixture to be treated; - the process includes a step consisting of bringing the treated mixture exiting the heat exchanger into a first tank ensuring separation of the water and gases that were dissolved in it; - the process includes a step of supplying the oxidation reactor with some of the gases present in the first tank, said gases serving as fuel for the combustion reaction; - the process further includes a series of steps consisting successively of taking the water contained in the first tank, then reducing said water thus taken to atmospheric pressure and finally conducting the water thus obtained into a second tank ensuring separation of said water with other gases, such as carbon dioxide, which were still dissolved in it; - the process includes a step of taking the water contained in the second tank and conveying it to a pressurized water supply circuit for the heat exchanger before this water enters the oxidation reactor. Brief description of the figures

[0026] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings, and for which:

[0027] The [Fig. 1] is a representation of a hydrothermal treatment device for organic compounds according to the invention. Detailed description of the invention

[0028] Fig. 1 represents a hydrothermal treatment device for organic compounds according to the invention.

[0029] The DT device for hydrothermal treatment of organic compounds comprises an RO oxidation reactor in series with an R gasification reactor, as well as a ECH heat exchanger which allows the heat from the water flow exiting the R gasification reactor to be recovered and injected onto a feed water flow entering the RO oxidation reactor.

[0030] The oxidation RO reactor has a first inlet ERO1 for an oxidizing gas and a second inlet ERO2 for a fuel gas. It allows a combustion reaction to be carried out. The oxidation RO reactor is configured to deliver water under supercritical conditions from a third inlet ERO3 to an outlet SRO.

[0031] The gasification reactor R is configured to operate with a mixture (mainly water) under supercritical conditions. This reactor R has a first inlet ER1 connected to the outlet SRO of the oxidation reactor RO, this first inlet being intended to recover the water exiting the oxidation reactor RO.

[0032] This reactor R also includes a second inlet ER2 for supplying a mixture to be treated (wet resource) under pressure; this mixture is therefore loaded with organic compounds. To pressurize the mixture to be treated, the DT device includes a CAI feed circuit for the mixture to be treated, supplying the gasification reactor R, which includes a blower SRP1.

[0033] This reactor R further includes an outlet SR for the outgoing aqueous flow and therefore includes dissolved gases from organic compounds.

[0034] Finally, the ECH heat exchanger is connected on the one hand, to the SR outlet of the gasification reactor R, the treated aqueous flow exiting the gasification reactor R being intended to serve as a hot source for the ECH heat exchanger, and on the other hand, to both a pressurized water supply and the third ERO3 inlet of the oxidation reactor RO, this pressurized water being intended to be preheated before entering the oxidation reactor RO.

[0035] We will continue to describe the practical implementation of the device described above.

[0036] The process is started up using water, with which the entire device is initially filled and then pressurized to the target operating pressure, typically between 240 bar and 270 bar in the gasification reactor and between 270 bar and 300 bar in the RO oxidation reactor. This pressure difference allows water to circulate from the RO oxidation reactor to the gasification reactor. The initial energy input required to heat the water to the desired temperature as it passes through the RO oxidation reactor (temperature between 900°C and 1000°C) and then through the gasification reactor (temperature between 600°C and 700°C, the sum of the superheated water and cold water flows injected in place of the mixture to be treated – a wet resource – during this step) is provided by the supply of an "external" combustible gas, namely a gas necessarily not originating from The implementation of the process according to the invention (for example, natural gas) during this start-up stage. This combustible "external" gas is therefore burned by combustion when mixed with an oxidant stream also supplied to the RO oxidation reactor.

[0037] Then, once all the flows have been brought to the desired operating conditions in terms of temperature and pressure (supercritical conditions), as well as flow rate in the oxidation RO reactor and the gasification R reactor, the mixture to be treated can be introduced into the gasification R reactor. It should be noted that the water from the oxidation RO reactor and the mixture to be treated thus mix in the gasification R reactor, within a relatively large volume.

[0038] This mixture to be treated generally comprises, depending on its nature, between at least 20% and at most 50% organic matter so that the process thus fed is a net producer of valuable reaction products (high calorific value gas: H2, CH4, etc.) taking into account the commonly observed energy efficiencies of the different blocks used in this system (efficiency of the exchanger part, heat losses, etc.).

[0039] Furthermore, the flow rate of the mixture to be treated, Dm[, is mixed with the superheated aqueous stream, Dm2, so as to reach a temperature within the gasification reactor of between 600°C and 700°C. For this purpose, the flow rate of the superheated aqueous stream, Dm2, is typically 3 to 4 times greater than that of the wet resource, Dm[, and at a temperature of between 900 and 1000°C. As a reminder, the pressure in the gasification reactor is typically between 240 and 270 bar, and the pressure in the RO oxidation reactor is typically between 270 and 300 bar.

[0040] A flow rate of mixture Dmi is then continuously injected into the gasification reactor, inside which a mixture is created with a flow rate Dm2 of superheated aqueous flux. The sum of these fluxes constitutes a flow rate Dm3. The temperature and pressure conditions allow the organic compounds contained in the mixture to be gasified. The thermochemical reactions present (hydrolysis) produce primarily gases with high calorific values ​​such as hydrogen (H2), methane (CH4), or ethane (C2H6). Carbon dioxide is also produced, as well as water-soluble organic species, depending on the temperature level reached in this reactor. The gasification reactor R allows the mixture, thus heated to high temperature and pressure, to remain under these conditions typically between 5 and 10 minutes to allow the conversion of most of the organic matter into gas.The residence time depends on the flow rate of the mixture being treated and the volume of the gasification reactor. For a given gasification reactor (fixed volume), the residence time is adjusted by the flow rate circulating in the reactor R. Naturally, the larger the quantities of the mixture to be treated, the larger the reactor volume must be.

[0041] Once the mixture has passed through the gasification reactor, it is extracted. This output stream from the gasification reactor (treated mixture) is essentially aqueous, passing through at a flow rate Dm3, containing the reaction gases dissolved in the aqueous stream - and possibly organic species in solution.

[0042] The treated mixture is then cooled to a temperature close to ambient through the heat exchanger ECH. The heat thus extracted is transferred to a water stream entering the oxidation reactor. This water stream, with a flow rate Dm2 entering the oxidation reactor, is thus preheated to a temperature between 550 and 650°C. This aqueous stream has been pressurized beforehand to a pressure between 270 and 300 bar, for example by means of a booster pump SRP2 provided in a CA2 water supply circuit for the RO oxidation reactor.

[0043] Performing a preheating step downstream of the RO oxidation reactor with the treated mixture (outgoing stream from the gasification reactor) offers advantages over preheating the mixture to be treated (which is therefore loaded with organic compounds). Indeed, the heat exchanger only receives streams that are already largely purified (few or no organic or inorganic elements that have been converted or precipitated in the gasification reactor, and, moreover, a supply of water to be superheated, which is by definition free of organic compounds). The risks of fouling, and therefore performance loss, of this exchanger are thus limited. This approach therefore does not present the drawbacks that can be encountered with the devices described by Chai Siah Le et al.

[0044] Advantageously, the mixture stream to be treated is fed directly into the gasification reactor from ambient temperature to the reaction temperature present. The absence of an intermediate temperature ramp-up stage (where heat recovery is transferred to the mixture stream before injection into the gasification reactor) can thus improve the overall efficiency of the process by avoiding the creation of intermediate organic compounds (under the effect of temperature, a source of chemical reaction activation) that are difficult to gasify subsequently.

[0045] Furthermore, the RO oxidation reactor must supply an aqueous flow at a flow rate Dm2 to the gasification reactor with a temperature between 900°C and 1000°C. The energy required to reach this temperature from the outlet temperature of the RO oxidation reactor comes from a combustion reaction, the fuel (gas) of which may be external. The oxidant required for this combustion reaction is supplied to the RO oxidation reactor in the form of pure gaseous oxygen, air, or another compound such as hydrogen peroxide. The oxidant flow rate is adjusted to the fuel flow rate to generate a stoichiometric mixture to ensure full combustion reaction efficiency.

[0046] The gas flow to be injected into the RO oxidation reactor to achieve the target temperature conditions is precisely controllable, unlike existing solutions such as those described in EP 3 806 995. This allows for optimal management of the reactor's operation. Furthermore, there is no ambiguity regarding the nature of the fuel consumed by the combustion reaction, as the organic compounds of the mixture to be treated are not present in this oxidation reactor.

[0047] Advantageously, the DT device may include a PCU tank to recover, during operation, the treated, pressurized, and cooled mixture exiting the heat exchanger. For this purpose, the PCU tank includes an ECU inlet connected to the heat exchanger ECH.

[0048] This PCU tank allows the separation of high-calorific-value gases (H2, CH4, C2H6, etc.) from the aqueous phase by simple sedimentation (gravity effect). At the ambient temperature prevailing in the PCU tank, the gases (except for carbon dioxide) are no longer dissolved in the aqueous phase. The aqueous phase therefore still contains carbon dioxide produced by the gasification reactions (since this gas is predominantly in a liquid state under the pressure conditions encountered here). In particular, the high-calorific-value gases produced by the gasification process can thus be recovered. The organic compounds are thereby valorized.

[0049] Advantageously, the PCU tank also includes an outlet SCU1, arranged on one side to recover the gases present in the PCU tank and on the other side connected to the second inlet ERO2 of the RO oxidation reactor to supply said gases as fuel for the RO oxidation reactor. In this case, a portion of the gases produced by the gasification process (the recovery) is therefore drawn off to feed combustion in the RO oxidation reactor. These gases are drawn off to the RO oxidation reactor at a pressure between 240 and 270 bar and are then increased, by means of a booster SRP3, to a pressure slightly higher than that in the RO oxidation reactor so as to allow their injection into said reactor.Depending on the organic matter concentration of the wet resource, the composition of the resulting gas, and the target temperature in the gasification reactor R, between 30% and 90% of the energy-recoverable gas is consumed to power the oxidation reactor RO. This differs significantly from what is proposed in the prior art, for example, in the article by Chai Siah Lee et al.

[0050] The water (remaining aqueous phase) contained in the PCU tank can also be used to recover the carbon dioxide dissolved in it.

[0051] For this purpose, the DT device then comprises a second tank DCU connected, via a pressure regulator D, to another outlet SCU2 of the first tank PCU, this other SCU2 outlet being arranged to be able to recover the water present in this first PCU tank.

[0052] The second DCU tank then allows the carbon dioxide (CO2) to be separated from the aqueous phase. The carbon dioxide is indeed in gaseous form under the temperature and pressure conditions prevailing in this tank (for example, ambient temperature and atmospheric pressure – the lower the pressure, the more carbon dioxide can be recovered in gaseous form). The carbon dioxide can then be utilized.

[0053] Advantageously, the water (the remaining aqueous phase) present in the second DCU tank can then be recycled to serve as water supply to the RO oxidation reactor after passing through the ECH exchanger.

[0054] To this end, the DT device includes a withdrawal means MS connected to an SCU outlet of the second tank DCU, the SCU outlet being arranged to be able to recover the water present in the second tank. For the same purpose, the withdrawal means MS is also connected to the CA2 pressurized water supply circuit of the RO oxidation reactor.

[0055] In the second DCU tank, the aqueous phase, now purified of all reaction gases but which may still contain organic compounds in solution, is recycled to supply the oxidation RO reactor with a flow rate Dm2. A flow rate Dm4 must therefore be extracted from the flow that was passing through at a flow rate Dm3 (the gas flow rate extracted from the aqueous phase is neglected for the purposes of this analysis) upon exiting the second DCU tank. This flow rate Dm4 is equal to the water flow rate Dm[ that enters the gasification reactor R via the mixture to be gasified.

[0056] Recycling the aqueous phase exiting the gasification reactor is particularly interesting, since it saves water.

[0057] Indeed, once the DT device is filled with water (start-up phase), there is no longer any need to inject additional water to generate the flow of superheated water entering the RO oxidation reactor.

[0058] It should also be noted that the separation of recycled and non-recycled streams can be carried out using a suitable MS extraction method to promote the presence of organic compounds in the recycled stream. For this purpose, a separation principle by decantation can be implemented.

[0059] This limits emissions and also improves the efficiency of the gasification process. Indeed, organic compounds that might still be in solution in the recycled stream exiting the second DCU tank are recycled and thus used as an energy source in the RO oxidation reactor (in addition, where applicable, to the withdrawal of reaction gases from the first tank). The aqueous phase, thus purified of organic compounds, can be more easily released into T environment.

[0060] All the steps implemented with the DT device confirms the invention described above can be summarized as follows.

[0061] The invention also relates to a hydrothermal treatment process for organic compounds, characterized in that it comprises the following steps: A) bring water to a temperature between 550°C and 650°C and a pressure between 270 and 300 bars in an RO oxidation reactor; B) implement a combustion reaction in the RO oxidation reactor in order to bring the water to a temperature between 900°C and 1000°C; C) to pass the heated water from the RO oxidation reactor to a R gasification reactor, the water being maintained at a pressure on the one hand between 240 and 270 bars and on the other hand lower than the pressure prevailing in the oxidation reactor and concomitantly, to supply said gasification reactor with a mixture to be treated, namely water loaded with organic compounds, under pressure; D) recover a treated mixture exiting the gasification reactor, this mixture containing dissolved gases, to serve as a hot source for a heat exchanger which also receives water at a pressure between 270 and 300 bars to superheat it from ambient temperature to a temperature between 550°C and 650°C before it enters the RO oxidation reactor.

[0062] Of course, it is understood that the pressure and temperature conditions present both in the gasification reactor R and in the oxidation reactor RO allow water to be contained in supercritical conditions.

[0063] Furthermore, in step B), the water brought in step A) as well as the elements necessary for the implementation of combustion, namely an oxidizer and a fuel, are all mixed in the oxidation reactor.

[0064] Furthermore, during step C), the mixture to be treated is advantageously introduced at ambient temperature into reactor R at a given inlet flow rate, and the water passing from the oxidation reactor RO to the gasification reactor R is introduced at a flow rate 3 to 4 times greater than the given inlet flow rate of the mixture to be treated. This makes it possible to maintain an adequate operating temperature in the gasification reactor R.

[0065] Advantageously, this process may also include a step consisting of bringing the treated mixture exiting the heat exchanger into a first PCU tank ensuring separation of the water and gases that were dissolved therein.

[0066] Advantageously, it may further include a step of supplying the oxidation RO reactor with a portion of the gases present in the first PCU tank, said gases serving as fuel for the combustion reaction.

[0067] Furthermore, it may also include a series of steps consisting of successful- ivically to extract the water contained in the first PCU tank, then to depress said extracted water to atmospheric pressure and finally to conduct the water thus obtained into a second DCU tank ensuring separation of said water with other gases, such as carbon dioxide, which were still dissolved in it.

[0068] Finally, it may advantageously include a step consisting of drawing the water contained in the second DCU tank and conveying it to a pressurized water supply circuit CA2 for the ECH heat exchanger before this water enters the RO oxidation reactor. The water is thus recycled, preferably along with any organic compounds still present in the water recovered from the second DCU tank.

Claims

Demands

1. A hydrothermal treatment process for organic compounds, characterized in that it comprises the following steps: A) bringing water to a temperature between 550°C and 650°C and to a pressure between 270 and 300 bar in an oxidation reactor (RO); B) carrying out a combustion reaction in the oxidation reactor (RO) in order to bring the water to a temperature between 900°C and 1000°C; C) passing the water thus heated from the oxidation reactor (RO) to a gasification reactor (R), the water being maintained at a pressure on the one hand between 240 and 270 bar and on the other hand lower than the pressure prevailing in the oxidation reactor (RO) and concomitantly, feeding said gasification reactor with a mixture to be treated, namely water loaded with organic compounds, under pressure;and D) recover a treated mixture exiting the gasification reactor, this mixture containing dissolved gases, to serve as a hot source for a heat exchanger which also receives water at a pressure between 270 and 300 bar to superheat it from ambient temperature to a temperature between 550°C and 650°C before it enters the oxidation reactor.

2. A process according to the preceding claim, characterized in that, during step C), the mixture to be treated is introduced at ambient temperature into the reactor (R) at a given inlet flow rate and the water passing from the oxidation reactor (RO) to the gasification reactor (R) is introduced at a flow rate 3 to 4 times greater than the given inlet flow rate of the mixture to be treated.

3. The method according to the preceding claim, characterized in that it comprises a step of bringing the treated mixture exiting the heat exchanger into a first tank (PCU) ensuring separation of the water and gases that were dissolved therein.

4. The method according to the preceding claim, characterized in that it comprises a step of feeding the oxidation reactor (RO) with a portion of the gases present in the first tank (PCU), said gases serving as fuel for the combustion reaction.

5. A method according to any one of claims 3 or 4, characterized in that it further comprises a series of steps consisting successively of take the water contained in the first tank (PCU), then expand said water thus taken to atmospheric pressure and finally conduct the water thus obtained into a second tank (DCU) ensuring separation of said water with other gases, such as carbon dioxide, which were still dissolved in it.

6. A method according to the preceding claim, characterized in that it includes a step of taking the water contained in the second tank to conduct it into a pressurized water supply circuit of the heat exchanger (HEI) before this water enters the oxidation reactor (OR).

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