System and method for producing biochar by drying and slow pyrolysis of a lignocellulosic material in a co2 atmosphere

Abstract

The invention relates to a system for producing biochar in a CO2 atmosphere from a lignocellulosic material, the system comprising at least one drying module (C1) operating in a CO2-saturated atmosphere and at least one pyrolysis module (P1), the system being characterised in that it comprises: - a CO2 source (D1); - at least one external thermal distribution device (DC), configured to supply CO2 to the drying module (C1) and the pyrolysis module (P1) from the CO2 source (D1), and to heat the CO2 injected into the system; a drying module (C1) operating in a CO2-saturated atmosphere and configured to dry a lignocellulosic material to a moisture content less than or equal to 1%; and a pyrolysis module (P1) operating in a CO2-saturated atmosphere at a maximum temperature of 390°C; the invention also relates to a method for producing biochar and to an associated pyrolysis module.

Description

Description SYSTEM AND METHOD FOR PRODUCING BIOCHAR BY DRYING AND SLOW PYROLYSIS OF A LIGNOCELLULOSIC MATERIAL UNDER CO2 ATMOSPHERE

[0001] The present invention relates to a system for producing biochar under a CC atmosphere from lignocellulosic materials, a pyrolysis module and an associated implementation method. Much progress has been made in the field of pyrolysis and in the production of biochar, and in particular slow pyrolysis. Pyrolysis of biomass consists of heating it to temperatures generally between 350 and 650 °C in the absence of oxygen, (or in the presence of a very small quantity of oxygen or air, intended to provide, by very partial combustion, the energy necessary for the pyrolysis process). This results in the production of a combustible gas also called syngas, a liquid (oil or mixture of hydrocarbons) also called tar, and a by-product called "biochar" which contains the mineral fraction of the biomass, as well as the "fixed carbon", i.e. the carbon present in the biomass which has not been transformed into gas or liquid. The proportion between gas, liquid and solid depends on many parameters such as the initial composition of the biomass, the transformation temperature and pressure, and the residence time.

[0002] There are therefore three co-products of biomass pyrolysis: biochar, syngas and a tar-type liquid.

[0003] Slow pyrolysis means pyrolysis with a maximum temperature between 300°C and 500°C with a slow rise in temperature.

[0004] A system is known presented in document EP3854861A1, which teaches an installation for producing biochar or similar from biomass, the installation comprising a station for transforming the biomass into a “pellet” type granulate comprising a grinder and a dryer, a pyrolysis furnace for transforming the granulate into a biochar granulate, positioned downstream of the transformation station, and a conditioner positioned downstream of the pyrolysis furnace for conditioning the biochar granulate, the installation comprising SUBSTITUTION SHEET (RULE 26) furthermore first means for transferring energy generated by the pyrolysis furnace to the transformation station, and also describes an associated biochar production method.

[0005] Such a system presented in document EP3854861A1 has the disadvantage of not controlling the drying of the biomass before the actual pyrolysis, and of obtaining a dried biomass whose humidity level is still too high before pyrolysis to guarantee a very limited production of tar-type co-product.

[0006] Furthermore, this system also does not allow to obtain dried biomass with adequate porosity for use in application areas such as agriculture. Indeed, uncontrolled preliminary drying crushes the ultra-structure of the dried biomass and induces limited porosity and specific surface area. However, the porosity of the dried material before pyrolysis greatly influences the specific surface area of ​​the biochar obtained and therefore its water or mineral salt retention capacity. Thus, porosity and ultra-structure are very important qualitative characteristics of the biochar material.

[0007] The main physicochemical properties to be considered when using biochar(s) as a temperate soil amendment are its porosity, specific surface area, water retention capacity, pH, electrical conductivity (EC), cation exchange capacity (CEC) as well as the type and concentration of mineral compounds (and possibly toxic compounds).

[0008] The system according to document EP3854861A1 also requires a lot of energy and a long time to dry the biomass to an acceptable moisture content for the next pyrolysis phase. The residual moisture (15% to 25% moisture) in the biomass after drying causes the generation of a liquid waste-type co-product (oil or tar).

[0009] Such a system presented in document EP3854861A1 also has the disadvantage of requiring fuels causing the emission of CO2, and being very polluting. In addition, the system has the disadvantage of controlling pyrolysis by indirect heat transfer and of requiring both an inclination of the pyrolysis furnace to allow the evacuation of the tar produced during pyrolysis but SUBSTITUTION SHEET (RULE 26) also means of rotation to ensure uniform heating of the biomass, which greatly complicates the system and makes it more expensive to set up.

[0010] The present invention overcomes these drawbacks.

[0011] The invention relates to a system for producing biochar under CO2 atmosphere from a lignocellulosic material and comprising at least one drying module C1 under CO2 atmosphere, and at least one pyrolysis module P1.

[0012] According to a first general definition of the invention, the system further comprises at least one source of CO2; - at least one thermal distribution device external to the drying module and to the pyrolysis module, configured to supply CO2 to the drying module and to the pyrolysis module from the CO2 source and to heat the CO2 injected into the system; the drying module under a CO2-saturated atmosphere is configured to dry a lignocellulosic material to a hygrometry less than or equal to 1% while retaining its ultrastructure; and the pyrolysis module is a pyrolysis module under a CO2-saturated atmosphere configured to carry out a slow pyrolysis of the lignocellulosic material thus dried with a maximum temperature of 390°C.

[0013] Advantageously, the biochar production system according to the invention makes it possible to dry the lignocellulosic material to a humidity level of less than or equal to 1% quickly and in an energy-optimized manner with lower energy consumption, while allowing faster pyrolysis, substantially eliminating any tar-type co-product during the production of biochar.

[0014] In practice, the CO2 atmosphere drying module of the system according to the invention comprises: - a drying chamber comprising at least one hollow cylindrical drying tube of diameter and length suitable for drying the lignocellulosic material in a chosen quantity; SUBSTITUTION SHEET (RULE 26) - gas circulation means for forcing the circulation of CO2 from one end to the other of the drying chamber in a closed circuit in the direction of the length of the chamber with an injection and an extraction in the cylinder positioned at the ends of the cylindrical drying chamber as well as the renewal of the atmosphere inside the drying chamber, and configured to establish a flow allowing the circulation of CO2 in said drying module and capable of uniformizing the thermal distribution in said drying chamber; - CO2 recycling means configured to allow the separation of water vapor and gaseous CO2 present in the atmosphere extracted from the chamber during drying; - metrological means for measuring variations in physical measurements of the drying module during heating; and in that the computer control system is configured to control the supply means, the circulation means, the heating means, and the recycling means, according to appropriate programs, setpoint values ​​and drying times to obtain a target hygrometry of less than 1% and to preserve the ultrastructure of the lignocellulosic material thus dried, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.

[0015] Advantageously, the Applicant has observed that the drying of the biomass implemented by the drying module under a CO2-saturated atmosphere according to the invention before the actual pyrolysis makes it possible to obtain a dried biomass with a humidity level less than or equal to 1% before pyrolysis to substantially guarantee a reduction / elimination of the production of tar-type co-product, while drastically reducing the drying and pyrolysis time.

[0016] In practice, the pyrolysis module of the system according to the invention comprises: a pyrolysis cell; - gas circulation means for forcing the circulation of CO2 from one end to the other of the pyrolysis cell in a closed circuit in the direction of the length of said pyrolysis cell with an injection and an extraction positioned at the ends of the pyrolysis cell as well as the renewal of SUBSTITUTION SHEET (RULE 26) the atmosphere inside the pyrolysis cell, and comprising a module configured to allow the circulation of CO2 capable of standardizing the thermal distribution in said pyrolysis cell; - metrological means for measuring the variations in physical measurements of the pyrolysis module during heating; and in that the computer control system is configured to control the supply means, the circulation means, the means of external to the pyrolysis cell, according to programs, setpoint values ​​and drying times appropriate according to the desired pyrolysis conditions, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.

[0017] Advantageously, the system also makes it possible to simplify the pyrolysis apparatus by eliminating any need for an inclination generally implemented on the conventional pyrolysis furnace to allow the evacuation of the tar produced during pyrolysis but also the elimination of rotation means to ensure uniform heating of the biomass, thus making the pyrolysis module less expensive to produce, simpler structurally and allowing more precise direct heat transfer via the use of CO2.

[0018] According to one embodiment of the invention, the system further comprises a conveyor configured to allow the transfer of the dried lignocellulosic material from the drying module to the pyrolysis module.

[0019] In addition, the control means are configured to: -Acquire metrological data and parameters of the lignocellulosic material to be dried by measuring metrological means; - Activate the CO2 supply means configured to saturate the drying chamber with CO2; -check that the CO2 saturation in the circulating gas mixture is sufficient to start a drying cycle by checking the CO2 / CH4 measuring means of the exhaust duct; -Activate the heating means to adjust the hygrometry of the lignocellulosic material by heating when a sufficient measured CO2 saturation is reached SUBSTITUTION SHEET (RULE 26) is reached, heat with a temperature limit according to the set temperature T1, according to a chosen temperature gradient G1 in order to extract the free water and the bound water from the lignocellulosic material to be dried and activate the circulating means; -stabilize the temperature of the CO2 circulating in the drying chamber, activate the recycling means then increase in a second phase the temperature of the CO2 circulating in the drying chamber until the measured hygrometry of the lignocellulosic material reaches a chosen intermediate target value Hi, the heating means being activated so that the reheating is carried out with a limit temperature defined by the set temperature T1 of 120°C according to a chosen temperature gradient G1, making it possible to extract the free water and the bound water from the lignocellulosic material to be dried up to a hygrometry of the lignocellulosic material close to 1% - Deactivate the recycling means and modulate the activity of the heating means to reduce the temperature of the drying chamber according to a first phase, down to a second setpoint temperature T2 for stabilization chosen according to a temperature gradient G2, when the average hygrometry measured of the lignocellulosic material via the means for measuring the hygrometry of the lignocellulosic material reaches the intermediate target value Hi chosen, unless one of the measured hygrometry values ​​of the lignocellulosic material is greater than Hi+4%, said setpoint temperature T2 being maintained for a chosen period of time until the measured hygrometry value of the lignocellulosic material greater than Hi+4% is stable and within a range of values ​​lower than Hi+4%; and - Deactivate the heating means, to reduce the temperature of the drying chamber in a second phase, when the average measured hygrometry of the lignocellulosic material reaches the final target hygrometry value of maximum 1%.

[0020] In practice, the control means are configured to: SUBSTITUTION SHEET (RULE 26) - inject the CO2 into the pyrolysis cell and activate the gas circulation means to force the circulation of the CO2 from one end of the pyrolysis cell to the other in a closed circuit; -when a CO2 saturation greater than 90% is reached, activate the heating means and heat the circulating CO2 from ambient temperature to a target temperature TP between 350°C and 390°C with a gradient of 20°C / h; -when the target temperature TP is reached, deactivate the heating means (2).

[0021] The invention further relates to a pyrolysis module under CO2 atmosphere.

[0022] According to a second definition of the invention, the pyrolysis module under CO2 atmosphere comprises: -at least one pyrolysis cell; - at least one thermal distribution device, configured to supply CO2 to the pyrolysis module from the CO2 source and heat the injected CO2; - gas circulation means allowing the renewal of the atmosphere inside the pyrolysis cell - a plurality of metrology measurement units forming metrological means, said pyrolysis module being further connected to a computer control system and configured to carry out slow pyrolysis of a lignocellulosic material having a humidity less than or equal to 1% under a saturated CO2 atmosphere with a maximum temperature of 390°C.

[0023] In practice, the gas circulation means making it possible to force the circulation of CO2 from one end to the other of the pyrolysis cell according to a closed circuit in the direction of the length of said pyrolysis cell with an injection and an extraction positioned at the ends of the pyrolysis cell as well as the renewal of the atmosphere inside the pyrolysis cell, and comprising a flow module configured to allow the circulation of CO2 capable of standardizing the thermal distribution in said pyrolysis cell; the metrological means are configured to measure the variations in physical measurements of the pyrolysis module during heating; and in that the computer control system is configured to control the means SUBSTITUTION SHEET (RULE 26) supply, circulation means, heating means, according to programs, setpoint values ​​and durations of rise in high temperature appropriate according to the desired pyrolysis conditions, and processing means to measure, compare and readjust the operating parameters to the setpoint values ​​in the event of a deviation.

[0024] The invention further relates to a method for producing biochar under CO2 atmosphere.

[0025] According to a third definition of the invention, a process for producing biochar comprising a drying step carried out in a drying module and a pyrolysis step carried out in a pyrolysis module of a lignocellulosic material, characterized in that: -the drying step comprises drying the lignocellulosic material under a saturating CO2 atmosphere by raising the temperature of the CO2 circulating in the drying module according to a gradient G1 with a limit temperature of 120°C until the measured humidity of the lignocellulosic material is less than or equal to 1%; - the method comprises a transfer step in which the dried lignocellulosic material of less than 1% is transferred into the pyrolysis module; and - the pyrolysis step, comprises the injection of CO2 into the pyrolysis module in a closed circuit and heating said CO2 circulating in the pyrolysis module from an ambient temperature to a maximum temperature between 350°C and 390°C.

[0026] For example, the G1 gradient of the drying step is 2°C / hour.

[0027] In practice, the heating of the CO2 circulating from the pyrolysis stage from room temperature to a maximum temperature between 350°C and 390°C is carried out according to a gradient of 20°C / hour.

[0028] Advantageously, the method according to the invention also makes it possible to obtain a dried biomass whose humidity is less than or equal to 1%, and whose porosity is adequate, said porosity obtained on the dried lignocellulosic material thus being preserved during pyrolysis to obtain a SUBSTITUTION SHEET (RULE 26) biochar with greatly improved surface efficiency and particularly suitable for use in application areas such as agriculture.

[0029] Furthermore, the system and method according to the invention allows the production of quality biochar for use in agriculture while limiting the production of co-products of the “oil or tar” type.

[0001] Other advantages and characteristics of the invention will appear on examining the description and the drawings in which: - [Fig 1] schematically represents the drying module of the biochar production system according to the invention; - [Fig 2] schematically represents the pyrolysis module of the biochar production system according to the invention; - [Fig 3] schematically represents a first embodiment of the biochar production system in accordance with the invention; - [Fig 4] schematically represents a second embodiment of the biochar production system according to the invention; - [Fig 5] schematically represents the process for producing biochar in accordance with the invention; and - [Fig 6] represents a microscopic view of lignocellulosic material dried under CCO2 atmosphere compared to air drying of the process according to the invention

[0030] With reference to figures 1 to 6, the biochar production system under CO2 atmosphere according to the invention comprises at least one CO2 source D1, at least one thermal distribution device DC, at least one drying module C1 under CO2 atmosphere, and at least one pyrolysis module P1 under CO2 atmosphere.

[0031] The system according to the invention comprises at least one DC thermal distribution device external to the drying module C1 and to the pyrolysis module P1, and having CO2 supply means 3 configured to control the injection of the CO2 gas mixture from the CO2 source D1, and has in SUBSTITUTION SHEET (RULE 26) in addition to heating means 2 configured to heat the CO2 injected into the system or reinjected into the system during closed circuit operation.

[0032] The CO2 supply means 3 comprise a conduit connected on the one hand to the CO2 source D1, and on the other hand to the heating means 2, said conduit being equipped with a solenoid valve 701 allowing the control of the injection of CO2 into the drying module C1 and into the pyrolysis module P1, the CO2 supply means 3 and the heating means 2 and the solenoid valve 701 form the thermal distribution device DC.

[0033] In practice, when the solenoid valve 701 is open, a command is sent to the CO2 source D1 in order to supply the biochar production system according to the invention with CO2. When the filling of the system is complete, the solenoid valve 701 is closed and the system according to the invention then operates in a closed circuit.

[0034] In practice, the CO2 supply means 3 further comprise metrological means 5 configured to measure parameters belonging to the group formed by flow rate of the injected circulating CO2 gas mixture, temperature of the injected circulating CO2 gas mixture.

[0035] According to one embodiment, the CO2 supply means 3 comprise at least one probe for measuring the temperature and the circulating flow rate 51.

[0036] Direct CO2 means CO2 from a high-flow CO2 source in the form of gas which has possibly been concentrated at its outlet from the off-gas of a methanizer or any industrial chimney and whose gas mixture, which mainly contains CO2, is directly used by the drying module C1 or the pyrolysis module P1 without phase change of the CO2.

[0037] Recycled CO2 means CO2 from a CO2 supply from a high-flow CO2 source discharged from an industrial activity and which has undergone possible purification, possible concentration, more broadly upstream treatment such as bottled and liquefied CO2, compressed gaseous CO2, CO2 off-gas SUBSTITUTION SHEET (RULE 26)

[0038] In practice, the CO2 supply means 3 consist of at least one CO2 injection system from the CO2 source D1 to the heating means 2.

[0039] In practice, the heating means 2 are of the immersion heater type and more particularly of the “in-line electric heater” type, external to the drying module C1 or the pyrolysis module P1.

[0040] For example, the immersion heater has a power of 90 kW, and comprises an inlet through which the gases to be heated enter, an open cylindrical or quasi-cylindrical steel conduit, into which an immersion heater is inserted, and finally a second outlet opening for the gases thus heated. The immersion heater also comprises a thermostat for regulating the temperature of the immersion heater.

[0041] Referring to Figures 3 and 4, each drying module C1, and each pyrolysis module P1 is individually connected to a DC thermal distribution device.

[0042] In practice, the drying module C1 is connected to a DC-C drying thermal distribution device via operating means C1 M configured to operate and control the drying in each drying module C1, and corresponding to any means arranged outside the drying chamber 1 allowing the operation thereof.

[0043] The pyrolysis module P1 is connected to a pyrolysis thermal distribution device DC-P via operating means P1 M configured to operate and control the pyrolysis in each pyrolysis module P1, and corresponding to any means arranged outside the pyrolysis cell allowing the operation thereof.

[0044] With reference to Figure 1, the system according to the invention further comprises at least one drying module C1 having several functional groups including a drying chamber 1 comprising at least one drying tube into which the lignocellulosic material to be dried is introduced, gas circulation means 4 allowing the renewal of the atmosphere inside the drying chamber 1, several metrology measurement units SUBSTITUTION SHEET (RULE 26) forming metrological means 5, connected to the control computer system 6 equipped with an application programming interface API.

[0045] The drying module C1 has a drying chamber 1 composed of one or more hollow cylindrical drying tubes allowing the introduction of the lignocellulosic material to be dried.

[0046] The drying chamber 1 is connected to the heating means 2 of the DC thermal distribution device by an inlet conduit 206a, and has an outlet conduit 206b configured to evacuate the CO2 gas mixture from said drying chamber 1.

[0047] In practice, the inlet duct 206a is arranged at a first end of the drying chamber 1 and the outlet duct 206b at a second end of the drying chamber 1 so as to allow longitudinal circulation of the CO2 gas mixture relative to the lignocellulosic material to be dried. By way of non-limiting example, the drying chamber 1 comprises a closed, heat-insulated tube with internal atmospheric recirculation.

[0048] As a non-limiting example, the drying chamber 1 includes a minimum volume of 10m3 saturable with CO2.

[0049] According to one embodiment, the drying chamber 1 according to the invention comprises metrological means 5 configured to measure parameters belonging to the group formed by hygrometry of the lignocellulosic material to be dried, hygrometry in the drying chamber 1, temperature of the lignocellulosic material to be dried, temperature in the drying chamber 1, pressure in the drying chamber 1.

[0050] According to one embodiment, the drying chamber 1 according to the invention comprises at least one probe for measuring the temperature and humidity in the drying chamber 53.

[0051] By way of non-limiting example, the drying chamber 1 comprises two probes for measuring the temperature and humidity in the drying chamber 53. SUBSTITUTION SHEET (RULE 26)

[0052] According to one embodiment, the drying chamber 1 according to the invention comprises at least one probe for measuring the hygrometry of the lignocellulosic material to be dried 54.

[0053] By way of non-limiting example, the drying chamber 1 comprises two probes for measuring the hygrometry of the lignocellulosic material to be dried 54.

[0054] In practice, the drying chamber 1 further comprises a control box 61 configured to receive and process the data recorded by the hygrometry measuring probes of the lignocellulosic material to be dried 54.

[0055] According to one embodiment, the drying chamber 1 according to the invention further comprises a pressure measuring probe 55 in said drying chamber 1, allowing the emergency evacuation of part of the atmosphere contained in the drying chamber 1 in the event of critical pressure therein.

[0056] In practice, each metrological measurement includes a set value or a group of set values ​​to be respected, specific to each species or application of the lignocellulosic material to be dried.

[0057] In practice, the critical pressure can be 1.5 bar.

[0058] The drying chamber 1 according to the invention further comprises door closing sensors 62, configured to detect the closing status of the doors for inserting the lignocellulosic material to be dried.

[0059] As a non-limiting example, the drying chamber 1 is 5.5m long with a circulation diameter of 2.4m, cylindrical or quasi-cylindrical in shape and contained in a maritime container insulated with 60mm thick lignocellulosic wool panels. This box is connected from one end to the other by a heat-insulated pipe, a heating system 2 and four centrifugal circulation fans capable of withstanding temperatures of up to 250°C.

[0060] The drying module C1 further comprises operating means C1 M configured to operate and control the drying in each drying module C1, and corresponding to any means arranged outside the drying chamber 1 allowing the operation thereof. SUBSTITUTION SHEET (RULE 26)

[0061] The inlet conduit 206a comprises a solenoid valve 702 configured to control the injection of the CO2 gas mixture into the drying chamber 1, as well as gas circulation means 4.

[0062] In practice, the gas circulation means 4 of the inlet duct 206a comprise at least one fan 41 capable of operating bilaterally in two directions of circulation of the gas mixture, either towards the drying chamber 1, and from the drying chamber 1.

[0063] Alternatively, the inlet duct 206a comprises at least two ducts connected to the drying chamber 1, each duct comprising at least one fan 41. These fans 41 are configured to each operate in one direction of circulation, i.e. at least one fan towards the drying chamber 1 and one fan from the drying chamber in the inlet duct 206a.

[0064] The heating means 2 are also connected to an outlet duct 206b connecting an outlet end of the drying chamber 1 to said heating means 2, and forming a closed-loop circulation duct of the CO2 gas mixture.

[0065] The outlet conduit 206b comprises a solenoid valve 706 configured to control the evacuation of the CO2 gas mixture into the drying chamber 1, as well as gas circulation means 4.

[0066] In practice, the gas circulation means 4 of the outlet duct 206b comprise at least one fan 42 capable of operating bilaterally in two directions of circulation of the gas mixture, either towards the drying chamber 1, and from the drying chamber 1.

[0067] Alternatively, the outlet duct 206b comprises at least two ducts connected to the drying chamber 1, each duct comprising at least one fan 42. These fans 42 are configured to each operate in one direction of circulation, i.e. at least one fan towards the drying chamber 1 and one fan from the drying chamber towards the heating means 2.

[0068] By way of non-limiting example, the circulation means 4 of the fan type 41, 42, are of the medium pressure, single-suction centrifugal fan type with a steel sheet sheath and turbine, said fan comprising a turbine SUBSTITUTION SHEET (RULE 26) forward inclined blades made of galvanized steel sheet, the fan 51 being capable of withstanding a maximum temperature of the air or CO2 to be transported from -20°C to 250°C.

[0069] The circulation means 4 of the inlet duct 206a in combination with the circulation means 4 of the outlet duct 206b form a flow inversion module capable of allowing the circulation of the CO2 gas mixture from the heating means 2 of the DC thermal distribution device to the drying chamber 1 in a first operating direction and from the drying chamber 1 to the heating means 2 of the DC thermal distribution device in a second operating direction, and thus forcing the circulation of the CO2 gas mixture in a closed circuit, through the drying chamber 1 in two circulation directions.

[0070] Advantageously, the alternating circulation of the CO2 in the inlet duct 206a and outlet duct 206b in two circulation directions makes it possible to circulate the CO2 in the direction of the length of the drying chamber 1 with an injection and an extraction advantageously positioned at the ends of the drying chamber 1 and thus maintain a uniformity of the temperature of the gas mixture in the drying chamber 1 and thus allow drying of the lignocellulosic material and uniform treatment of the CO2 in the lignocellulosic material.

[0071] The Applicant surprisingly observed that the use of the flow inversion module and more particularly the circulation of CO2 longitudinally in the drying chamber 1 in an alternative manner makes it possible to limit the presence of water in the liquid state in the drying chamber 1, and thus makes the use of an inclined drying chamber and a swan neck type elimination system optional for eliminating water in liquid form which may accumulate at the base of the drying chamber 1.

[0072] In practice, the fans 41, 42 of the inlet duct 206a and the outlet duct 206b are coupled to frequency variators which advantageously make it possible to reduce the rotation speed depending on the types of lignocellulosic material to be dried, and therefore the flow rate of the circulating gas mixture. SUBSTITUTION SHEET (RULE 26) depending on the humidity level of the lignocellulosic material and the temperature of the circulating gas mixture and thus optimize the uniformity of drying.

[0073] The outlet conduit 206b further comprises a bypass for sampling the circulating gas mixture 45 and integrating CO2 / CH4 measuring means 56, configured to measure the proportion of CO2 relative to the total volume of gas in circulation and the proportion of CH4 circulating during the drying phase of the drying module C1, in CO2, and thus verify the CO2 saturation in the entire circuit of the drying module C1.

[0074] Advantageously, monitoring the CO2 / CH4 of the gas mixture during drying makes it possible to record the evolution of the concentration of the different compounds in the circulating gas mixture and thus allow the operation of the drying module 1 to be adjusted, but also to ensure the safety of the drying module C1, in the event of a drastic increase in the quantity of CH4.

[0075] In practice, if the quantity of CH4 in the gas mixture circulating during drying is greater than 3.5%, the drying module C1 is immediately emptied.

[0076] The outlet conduit 206b further comprises metrological means 5 configured to measure parameters belonging to the group formed by flow rate of the injected circulating CO2 gas mixture, temperature of the injected circulating CO2 gas mixture, and hygrometry of the circulating gas mixture.

[0077] According to one embodiment, the outlet conduit 206b comprises at least one probe for measuring the temperature and the circulating flow rate 51.

[0078] By way of non-limiting example, the outlet conduit 206b comprises at least one probe for measuring the temperature and the circulating flow rate 51 arranged upstream and one probe for measuring the temperature and the circulating flow rate 51 arranged downstream of the CO2 recycling means 600.

[0079] According to one embodiment, the outlet duct 206b comprises at least one temperature and humidity measuring probe 53.

[0080] By way of non-limiting example, the outlet duct 206b comprises at least one temperature and humidity measuring probe 53 arranged upstream and SUBSTITUTION SHEET (RULE 26) a temperature and humidity measuring probe 53 arranged downstream of CO2 recycling means 600.

[0081] In practice, the outlet duct 206b comprises at least one temperature and humidity measuring probe 53 arranged upstream and one temperature and humidity measuring probe 53 arranged downstream of CO2 recycling means 600, and at least one temperature and circulating flow rate measuring probe 51 arranged upstream and one temperature and circulating flow rate measuring probe 51 arranged downstream of CO2 recycling means 600.

[0082] Advantageously, such an arrangement makes it possible to monitor the composition of the circulating gas mixture but also the activity of the CO2 recycling means 600 as well as their modulation.

[0083] The drying module C1, according to the invention, further comprises CO2 recycling means 600 arranged at the outlet duct 206b allowing the separation of the water vapor and the gaseous CO2 present in the atmosphere extracted from the chamber 1 during drying, in order to be able to eliminate the water while recovering the CO2 in order to be stored, or to be directly reused in the biochar production system according to the invention.

[0084] By way of non-limiting example, condensation recycling means 600 are used, reducing the temperature of the binary water vapor / CO2 gas mixture extracted from the drying chamber 1 to a chosen temperature, allowing the condensation of the water in the mixture, which is then recovered by gravity in liquid form and eliminated. In practice, the recycling means 600 allow the drying of the internal atmosphere extracted from the drying chamber 1 via thermal condensation of the water vapor by cooling, on at least one heat exchanger equipped with at least one cold battery, it will be possible to advantageously place several cold batteries configured in series to increase the dehumidification capacity of each drying module C1. The system therefore allows the reinjection of the dehydrated atmosphere into the drying chamber 1.

[0085] In practice, each heat exchanger includes at least one EV evaporator and at least one CO condenser. SUBSTITUTION SHEET (RULE 26)

[0086] According to one embodiment of the invention, the heat exchanger of the recycling means 600 is only active when the hygrometry of the circulating gas mixture is between two threshold values.

[0087] In practice, the heat exchanger of the CO2 recycling means 600 is only active during the drying phase, and when the measured hygrometry of the circulating gas mixture is between a maximum threshold value and a minimum threshold value.

[0088] For example, the humidity threshold values ​​in drying chamber 1 are 20% for the minimum threshold and 100% for the maximum threshold.

[0089] According to one embodiment of the invention, the recycling means 600 comprise a heat exchanger type system comprising at least two cold batteries, configured in series to gradually extract the water from the gas mixture, each cold battery being capable of extracting a chosen percentage of the water from said gas mixture.

[0090] Advantageously, a series of cold batteries makes it possible to limit the humidity in the drying chamber 1, and thus make it possible to limit the duration of the drying cycle, making it possible to resolve the performance problem of a conventional heat exchanger when the humidity is higher than the critical operating value, and thus to reduce the duration of each cycle, causing the operation of each drying module C1, over a shorter period and limiting the associated energy expenditure.

[0091] According to one embodiment, the recycling means 600 further comprise a discharge outlet configured to discharge the condensed water or condensates, said discharge outlet incorporating a water flow meter 57.

[0092] The water flow meter 57 is configured to record the discharge rate of the water to be removed, and thus makes it possible to correlate the quantity of water removed with the difference between the initial and final humidity level of the lignocellulosic material for a drying cycle.

[0093] For example, maintaining the humidity in the drying chamber 1 below a chosen value makes it possible to shorten the drying cycle. SUBSTITUTION SHEET (RULE 26) for which the means of circulation 213a, 213b of CO2 in the drying module(s) C1, can represent 5 to 20% of the energy expenditure.

[0094] Advantageously, the recycling means 600 make it possible to control the hygrometry of the gas mixture and thus control the quality of the drying of the lignocellulosic material, thus optimizing the drying process and the quality of the material obtained, while limiting the energy expenditure and maintaining a low temperature difference between the CO2 leaving the heating means 2 and coming from the recirculation module 206c.

[0095] In practice, the CO2 gas recovered by the recycling means 600 can be stored in the storage means of the distribution system D1, or directly reinjected into the drying chamber 1.

[0096] According to a particular embodiment of the invention, the drying chamber 1 comprises at least one evacuation circuit, which is followed by a so-called "breathing" conduit comprising at least one breathing solenoid valve 704, 705 of the drying chamber 1, which allows the injection of air coming from outside the system into the drying chamber 1 and the evacuation of the gas mixture contained in said drying chamber 1.

[0097] The evacuation circuit further comprises circulation means 4 of the fan 43 type, as well as CO2 / CH4 measuring means 56, configured to measure the proportion of CO2 relative to the total volume of gas in circulation and the proportion of CH4 circulating during the filling phase of the drying module C1, with CO2, and thus verify the CO2 saturation in the entire circuit of the drying module C1, and configured to allow the emptying of the drying chamber 1.

[0098] According to one embodiment, the drying module C1, according to the invention, further comprises an additional evacuation outlet connected to the drying chamber 1 and comprising at least one fan 44 followed by an outlet solenoid valve 703 as well as a flow rate and temperature measurement sensor 51, and configured to allow the measurement of the flow rate and temperature of the gas mixture during the emptying of the drying chamber 1. SUBSTITUTION SHEET (RULE 26)

[0099] By way of non-limiting example, the circulation means 4 of the fan type 43, 44, of the additional evacuation outlet and of the evacuation circuit are of the medium pressure and single suction centrifugal fan type with duct and turbine made of sheet steel, said fan comprising a turbine with forward inclined blades made of galvanized sheet steel, the fan 51 being capable of withstanding a maximum temperature of the air or CO2 to be transported from -20°C to 250°C.

[0100] The drying module C1 is connected to the computer control system 6 comprising an application programming interface API. The application programming interface allows, on the one hand, the management of the sending of instructions to each of the components of the drying module C1, and on the other hand to integrate the data received by the various metrological means 5, in order to adjust the instructions sent to the components of said drying module C1.

[0101] The computer control system 6 is configured to control the supply 3, circulation 4, heating 2, and recycling 600 means according to appropriate programs, setpoint values ​​and drying times depending on the quality of the desired dried lignocellulosic material, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.

[0102] The drying module C1 according to the invention makes it possible to preserve the ultrastructure of the lignocellulosic material and to limit as much as possible the crushing of the microscopic structure of said lignocellulosic material during drying, this maintenance of the porosity of the lignocellulosic material during drying in combination with obtaining a humidity level less than or equal to 1% makes it possible to obtain a dried intermediate material product particularly optimized for the pyrolysis phase and the production of a quality biochar.

[0103] With reference to Figure 2, the biochar production system according to the invention further comprises at least one pyrolysis module P1.

[0104] The pyrolysis module P1 of the system according to the invention comprises several functional groups among which at least one pyrolysis cell P11 configured to accommodate the lignocellulosic material dried by the heating module C1, connected to the thermal distribution device DC, means of SUBSTITUTION SHEET (RULE 26) gas circulation P 4 allowing the renewal of the atmosphere inside the pyrolysis cell P11, several metrology measurement units forming metrological means P5, said pyrolysis module P1 being further connected to the control computer system 6.

[0105] The pyrolysis module P1 has a pyrolysis cell P11 composed of one or more hollow cylindrical tubes allowing the introduction of dried lignocellulosic material for pyrolysis.

[0106] The pyrolysis cell P11 is connected to the heating means 2 of the thermal distribution device DC by an inlet conduit P206a, and has an outlet conduit P206b configured to evacuate the CO2 gas mixture from said pyrolysis cell P11.

[0107] In practice, the inlet duct P206a is arranged at a first end of the pyrolysis cell P11 and the outlet duct 206b at a second end of the pyrolysis cell P11 so as to allow longitudinal circulation of the CO2 gas mixture relative to the dried lignocellulosic material to be pyrolyzed. As a non-limiting example, the pyrolysis cell P11 comprises a closed, heat-insulated tube with internal atmospheric recirculation.

[0108] Internal atmospheric recirculation means a closed loop circulation of CO2 injected and heated during slow pyrolysis.

[0109] According to one embodiment, the pyrolysis cell P11 according to the invention comprises metrological means 5 configured to measure parameters belonging to the group formed by temperature in the pyrolysis cell P11, pressure in the pyrolysis cell P11.

[0110] According to one embodiment, the pyrolysis cell P11 according to the invention comprises a non-return pressure relief valve on the roof of P11 for evacuating the syngas generated by the pyrolysis of the lignocellulosic biomass.

[0111] In addition, a pressure measuring probe P55 is arranged in said pyrolysis cell P11, allowing the emergency evacuation of part of the atmosphere contained in the pyrolysis cell P11 in the event of critical pressure in the latter. The syngas can be ideally converted into useful products such as SUBSTITUTION SHEET (RULE 26) fuels, chemicals or electricity, several industrial equipment are available on the market such as gas turbines.

[0112] In practice, each metrological measurement includes a set value or a group of set values ​​to be respected.

[0113] In practice, the critical pressure can be 1.5 bar.

[0114] The pyrolysis cell P11 according to the invention further comprises door closing sensors P62, configured to detect the closing status of the insertion doors of the dried lignocellulosic material to be pyrolyzed.

[0115] The pyrolysis module P1 further comprises operating means P1 M configured to operate and control the drying in each pyrolysis module P1, and corresponding to any means arranged outside the pyrolysis cell P11 allowing the operation thereof such as the circulation of CO2, the control and control of the circulation parameters of said circulation of CO2 and of the pyrolysis.

[0116] The inlet conduit P206a comprises a solenoid valve P702 configured to control the injection of the CO2 gas mixture into the pyrolysis cell P11, as well as gas circulation means P4.

[0117] In practice, the gas circulation means P4 of the inlet duct P206a comprise at least one centrifugal fan P41 capable of operating at high temperature, either towards the pyrolysis cell P11, and from the pyrolysis cell P11.

[0118] High temperature means a temperature above 450°C.

[0119] The heating means 2 of the DC thermal distribution device are also connected to an outlet duct P206b connecting an outlet end of the pyrolysis cell P11 to said heating means 2, and forming a closed-loop circulation duct of the CO2 gas mixture.

[0120] The outlet conduit 206b comprises a solenoid valve P706 configured to control the evacuation of the CO2 gas mixture into the pyrolysis cell P11, as well as gas circulation means P4. SUBSTITUTION SHEET (RULE 26)

[0121] In practice, the gas circulation means P 4 of the outlet duct P206b comprise at least one centrifugal fan P42 capable of operating at high temperature from the pyrolysis cell P11.

[0122] By way of non-limiting example, the circulation means P4 of the fan type P41, P42, are of the medium pressure, single-intake centrifugal fan type with a duct and turbine made of sheet steel, said fan comprising a turbine with forward-inclined blades made of galvanized sheet steel, each fan P41, P42, P44 being capable of withstanding a maximum temperature of the air or CO2 to be transported of 450°C.

[0123] The circulation means P4 of the inlet duct P206a in combination with the circulation means P4 of the outlet duct P206b form a module capable of allowing the circulation of the CO2 gas mixture from the heating means 2 of the DC thermal distribution device to the pyrolysis cell P11 and thus forcing the circulation of the CO2 gas mixture in a closed circuit, through the pyrolysis cell P11.

[0124] Advantageously, the alternating circulation of CO2 in the inlet conduit P206a and outlet conduit P206b makes it possible to circulate the high temperature CO2 in the direction of the length of the pyrolysis cell P11 with injection and extraction advantageously positioned at the ends of the pyrolysis cell P11 and thus maintain a uniformity of the temperature of the gas mixture in the pyrolysis cell P11 and thus allow a uniform pyrolysis of the lignocellulosic material and a uniform treatment of the CO2 in the lignocellulosic material thus eliminating the need to have a pyrolysis module inclined at a given angle and rotation means to ensure the uniformity of the biochar in production.

[0125] In practice, the fans P41, P42 of the inlet duct P206a and the outlet duct P206b are coupled to frequency converters which advantageously make it possible to reduce the CO2 circulation speed.

[0126] The outlet duct P206b further comprises metrological means P5 configured to measure parameters belonging to the group formed by flow rate SUBSTITUTION SHEET (RULE 26) of the injected circulating CO2 gas mixture, temperature of the injected circulating CO2 gas mixture.

[0127] According to one embodiment, the outlet duct P206b comprises at least one probe for measuring the temperature and the circulating flow rate P52.

[0128] According to a particular embodiment of the invention, the pyrolysis cell P11 comprises at least one evacuation circuit P206c, which is followed by a so-called “breathing” conduit comprising at least one breathing solenoid valve P703 of the pyrolysis cell P11, which allows the evacuation of gases produced during the pyrolysis operation after completion of said pyrolysis step or the triggering of the safety device due to a pressure above the critical threshold in P11.

[0129] According to one embodiment, evacuation circuit P206c further comprises at least one fan P44 followed by an outlet solenoid valve P703 as well as a flow rate and temperature measurement sensor P51, and configured to allow measurement of the flow rate and temperature of the gas mixture during emptying of the pyrolysis cell P11.

[0130] The pyrolysis module P1 is connected to the computer control system 6 comprising an application programming interface API. The application programming interface allows, on the one hand, the management of the sending of instructions to each of the components of the pyrolysis module P1, and on the other hand to integrate the data received by the various metrological means P5, in order to adjust the instructions sent to the components of said pyrolysis module P1.

[0131] The computer control system 6 is configured to control the supply means 3, heating means 2 of the DC thermal distribution device as well as the circulation means P4 of the pyrolysis cell P1, according to appropriate programs, setpoint values ​​and pyrolysis durations depending on the quality of the inserted dried lignocellulosic material, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.

[0132] The pyrolysis module P1 under CO2 atmosphere according to the invention in combination with the drying module under CO2 atmosphere, makes it possible to very limit SUBSTITUTION SHEET (RULE 26) strongly in use the loss of porosity of the dried lignocellulosic material and the crushing of the microscopic structure of said lignocellulosic material during drying in C1. The porosity of the dried material before pyrolysis greatly influences the specific surface area of ​​the biochar obtained and therefore its capacity to retain water or mineral salts. The porosity and structure of the biochar is a predominant characteristic of its quality. The use of an intermediate material product dried via the drying module C1 with a moisture content of less than or equal to 1% also makes it possible to substantially eliminate any production of the oil or tar type co-product during slow pyrolysis. The limitation or even the absence of oil production as a co-product also makes it possible not to add an additional level of complexity to the structural implementation of the system and makes it possible to eliminate numerous maintenance phases of said pyrolysis module P1.

[0133] With reference to Figure 3, the system according to the invention further comprises a conveyor (or rail) V arranged between the drying module C1 and the pyrolysis module P1, configured to allow the load of lignocellulosic material to be pushed directly from the drying module C1 to the pyrolysis module P1 and to allow simple and efficient handling between the drying phase and the pyrolysis phase.

[0134] In practice, the control computer system 6 is equipped with an application programming interface API and is configured to implement a biochar production method described with reference to FIG. 5.

[0135] With reference to Figure 5, the biochar production process comprises a preliminary drying step S1, implemented in a drying module C1.

[0136] The drying step S1 comprises drying the lignocellulosic material under a CO2-saturated atmosphere by raising the temperature of the CO2 circulating in the drying module C1 according to a gradient G1 with a limit temperature of 120°C until the measured humidity of the lignocellulosic material is less than or equal to 1%.

[0137] Saturated in CO2 means a CO2 saturation of at least 60%.

[0138] Drying step S1 further comprises the following sub-steps: -insert a lignocellulosic material to be dried into the drying module C1; SUBSTITUTION SHEET (RULE 26) -Acquire metrological data and parameters of the lignocellulosic material to be dried by measuring metrological means 5; - Activate the CO2 supply means 3 configured to saturate the drying chamber 1 with CO2; -check that the CO2 saturation in the circulating gas mixture is sufficient to start a drying cycle by checking the CO2 / CH4 measuring means 56 of the exhaust duct; -Activate heating means 2 to adjust the hygrometry of the lignocellulosic material by heating when a sufficient measured CO2 saturation is reached. Sufficient measured CO2 saturation means a CO2 content in the circulating gas mixture of at least 60% CO2.

[0139] In practice, the inserted lignocellulosic material belongs to the group formed by wood chips or wood chips and any type of wood (hardwood and softwood, industrial wood, processed wood, wood from recycled material, glued laminated wood),

[0140] Physical preparation means at least one action of the grinding type and possibly sieving to obtain chips or wafers with a maximum size of 6.4 mm.

[0141] The drying step S1 further comprises the following sub-steps: Whatever the humidity of the incoming lignocellulosic material, heat with a temperature limit according to the set temperature T1 the circulating CO2, according to a chosen temperature gradient G1 in order to extract the free water and the bound water from the lignocellulosic material to be dried and activate the circulating means 203a, 203b. In practice, the chosen temperature gradient G1 is 2°C / hour. activate the recycling means 600 then increase the temperature of the CO2 circulating in the drying chamber 1 until the measured hygrometry of the lignocellulosic material reaches a chosen target value Hi, the heating means 2 being activated so that the reheating is carried out with a limit temperature defined by a set temperature T 1 of 120°C according to SUBSTITUTION SHEET (RULE 26) Tl a chosen temperature gradient G1, and depending on the specific drying profile of the lignocellulosic material to be dried allowing the extraction of free and bound water from the lignocellulosic material to be dried; - Deactivate the recycling means 600 and modulate the activity of the heating means 2 to reduce the temperature of the drying chamber 1 according to a first phase, down to a second setpoint temperature T2 for stabilization chosen according to a temperature gradient G2, when the average hygrometry measured of the lignocellulosic material via the hygrometry measuring means 54 of the lignocellulosic material reaches the target value Hi chosen, unless one of the measured hygrometry values ​​of the lignocellulosic material is greater than Hi+1%, said setpoint temperature T2 being maintained for a chosen period of time until the measured hygrometry value of the lignocellulosic material greater than Hi+1% is stable and included in a range of values ​​less than Hi+1%; - Deactivate the heating means 2, to reduce the temperature of the drying chamber 1 according to a second phase, when the average measured hygrometry of the lignocellulosic material reaches the final target hygrometry value Hc.

[0142] It should be noted that during this phase of temperature reduction of the drying module C1, the inertia of the system means that the hygrometry in the lignocellulosic material continues to decrease until the final target hygrometry value Hc.

[0143] The set temperatures T1 and T2 are temperature limits that each drying module C1 cannot exceed during these phases.

[0144] Furthermore, each passage from one stage to another stage is only dependent on the hygrometric target to which the current stage is conditioned.

[0145] In practice the chosen value range Hc is defined as a hygrometry value chosen between 0% and 1% humidity.

[0146] In practice, the set temperature T2 is less than or equal to 120°C.

[0147] According to one embodiment of the invention, the computer control system 6 is further configured to enable the control of the dehumidification of the CO2, SUBSTITUTION SHEET (RULE 26) which is carried out according to a minimum (5%) and maximum (100%) value of the humidity of the atmosphere of drying chamber 1. This dehumidification is activated as soon as necessary, i.e. when the humidity of the atmosphere of drying chamber 1 is higher than the set value, and whatever the initial humidity of the lignocellulosic material.

[0148] The computer control system 6 also allows the monitoring, measurement and recording of all metrological values ​​measured in a table (including energy consumption), as well as emergency procedures (stop without resuming drying or with resuming drying).

[0149] In practice, the G1 gradient of the drying step is 2°C / hour.

[0150] The method then comprises a transfer step T in which the dried lignocellulosic material of less than 1% is transferred into the pyrolysis module P1.

[0151] The method according to the invention further comprises a pyrolysis step S2 implemented in a pyrolysis module P1 of the dried lignocellulosic material comprising the injection of CO2 into the pyrolysis module P1 in a closed circuit and heating said CO2 circulating in the pyrolysis module P1 from an ambient temperature to a temperature between 350°C and 390°C.

[0152] Furthermore, the heating of the CO2 circulating from the pyrolysis stage from room temperature to a temperature between 350°C and 390°C is carried out according to a gradient of 20°C / hour.

[0153] The control means 6 are configured to implement the pyrolysis step S2 by: - inject the CO2 into the pyrolysis cell P11 and activate the gas circulation means (P4) allowing the CO2 to be forced to circulate from one end to the other of the pyrolysis cell P11 in a closed circuit; - when CO2 saturation greater than 90% is reached, activate the heating means 2 and heat the circulating CO2 from ambient temperature to a target temperature TP between 350°C and 390°C with a gradient of 20°C / h; - when the target temperature TP is reached, deactivate the heating means 2. SUBSTITUTION SHEET (RULE 26)

[0154] In practice, the CO2 at the end of the drying cycle and at the outlet of the drying module C1 has an outlet temperature of between 50°C and 120°C and can advantageously be reinjected into the pyrolysis module P1, which is previously closed and already has a load of lignocellulosic material to be pyrolyzed.

[0155] Advantageously, such a transfer makes it possible to limit the thermal energy required to launch the pyrolysis step S2.

[0156] With reference to Figure 6, the “green” wood column describes the structure of lignocellulosic material from undried spruce and oak with a differentiated and visible ultrastructure with a sequence of walls and lumens seen under a microscope.

[0157] The "air" column describes the structure of lignocellulosic material from spruce and oak air-dried by artificial drying in the presence of air, having a crushed ultrastructure / porosity, with wall chaining and an absence of lumens visible under the microscope.

[0158] The CO2 column describes the structure of lignocellulosic material from spruce and oak dried under a CO2-saturated atmosphere using the process according to the invention, having a preserved, porous ultrastructure with a chain of walls and lumens visible under a microscope.

[0159] Advantageously, the drying step S1 under a CO2-saturated atmosphere makes it possible to carry out pyrolysis on a material that has retained its initial porosity, allowing optimization of the specific surface area of ​​the biochar produced, while having a hygrometry less than or equal to 1%, thus allowing the formation of “tar / oil” during the pyrolysis step S2.

[0160] Furthermore, any example of means implemented is only particular examples of means that can be used to carry out the invention. Those skilled in the art will understand that these examples are not limiting and are not limited to the examples mentioned but to any example of means whose implementation provides the same technical effect. SUBSTITUTION SHEET (RULE 26)

Claims

Claims

1. System for producing biochar under CO2 atmosphere from a lignocellulosic material and comprising at least one drying module (C1) under CO2-saturated atmosphere, and at least one pyrolysis module (P1) and a computer control system (6), characterized in that it further comprises: at least one source of CO2 (D1); - at least one thermal distribution device (DC) external to the drying module (C1) and to the pyrolysis module (P1), configured to supply CO2 to the drying module (C1) and to the pyrolysis module (P1) from the CO2 source (D1) and to heat the CO2 injected into the system; and in that the drying module (C1) under a CO2-saturated atmosphere is configured to dry a lignocellulosic material to a hygrometry less than or equal to 1% while retaining its ultrastructure; and in that the pyrolysis module (P1) is a pyrolysis module (P1) under a CO2-saturated atmosphere configured to carry out a slow pyrolysis of the lignocellulosic material thus dried with a maximum temperature of 390°C.

2. System according to claim 1, characterized in that the drying module (C1) under CO2 atmosphere comprises: - a drying chamber (1) comprising at least one hollow cylindrical drying tube of diameter and length suitable for drying the lignocellulosic material in a chosen quantity, - gas circulation means (4) making it possible to force the circulation of CO2 from one end to the other of the drying chamber (1) according to a closed circuit in the direction of the length of the chamber with an injection and an extraction in the cylinder positioned at the ends of the cylindrical drying chamber as well as the renewal of the atmosphere inside the drying chamber (1), and configured to establish a flow allowing the circulation of CO2 in said drying module (C1) and capable of uniformizing the thermal distribution in said drying chamber (1); - CO2 recycling means (600) configured to allow the SUBSTITUTION SHEET (RULE 26) separation of water vapor and gaseous CO2 present in the atmosphere extracted from the chamber (1) during drying; - metrological means (5) for measuring the variations in physical measurements of the drying module during heating; and in that the computer control system (6) is configured to control the supply means (3), the circulation means (4), the heating means (2), and the recycling means (600), according to programs, setpoint values ​​and drying times appropriate for obtaining a target hygrometry of less than 1% and preserving the ultrastructure of the lignocellulosic material thus dried, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.

3. System according to claim 1 or 2, characterized in that the pyrolysis module (P1) comprises: a pyrolysis cell (P11); - gas circulation means (P4) making it possible to force the circulation of CO2 from one end to the other of the pyrolysis cell (P11) according to a closed circuit in the direction of the length of said pyrolysis cell (P11) with an injection and an extraction positioned at the ends of the pyrolysis cell (P11) as well as the renewal of the atmosphere inside the pyrolysis cell (P11), and comprising a module configured to allow the circulation of CO2 capable of standardizing the thermal distribution in said pyrolysis cell (P11); - metrological means (5) for measuring the variations in physical measurements of the pyrolysis module (P11) during heating; and in that the computer control system (6) is configured to control the supply means (3), the circulation means (P4), the means external to the pyrolysis cell (P1), according to programs, setpoint values ​​and drying times appropriate as a function of the desired pyrolysis conditions, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation. SUBSTITUTION SHEET (RULE 26)

4. System according to one of claims 1 to 3, characterized in that it further comprises a conveyor (V) configured to allow the transfer of the dried lignocellulosic material from the drying module (C1) to the pyrolysis module (P1).

5. System according to claim 2, characterized in that the control means (6) are configured to: -Acquire metrological data and parameters of the lignocellulosic material to be dried by measuring metrological means (5); - Activate the CO2 supply means (3) configured to saturate the drying chamber (1) with CO2; -check that the CO2 saturation in the circulating gas mixture is sufficient to start a drying cycle by checking the CO2 / CH4 measuring means (56) of the exhaust duct; -Activate the heating means (2) to adjust the hygrometry of the lignocellulosic material by heating when a sufficient measured CO2 saturation is reached, heat with a temperature limit according to the set temperature T1, according to a chosen temperature gradient G1 in order to extract the free water and the bound water from the lignocellulosic material to be dried and activate the circulating means (203a, 203b); -stabilize the temperature of the CO2 circulating in the drying chamber (1), activate the recycling means (600) then increase in a second phase the temperature of the CO2 circulating in the drying chamber (1) until the measured hygrometry of the lignocellulosic material reaches a chosen intermediate target value Hi, the heating means (2) being activated so that the reheating is carried out with a limit temperature defined by the set temperature T1 of 120°C according to a chosen temperature gradient G1, making it possible to extract the free water and the bound water from the lignocellulosic material to be dried up to a hygrometry of the lignocellulosic material close to 1% - Deactivate the recycling means (600) and modulate the activity of the heating means (2) to reduce the temperature of the drying chamber (1) according to SUBSTITUTION SHEET (RULE 26) a first phase, up to a second setpoint temperature T2 for stabilization chosen according to a temperature gradient G2, when the average hygrometry measured of the lignocellulosic material via the hygrometry measuring means (54) of the lignocellulosic material reaches the intermediate target value Hi chosen, unless one of the measured hygrometry values ​​of the lignocellulosic material is greater than Hi+4%, said setpoint temperature T2 being maintained for a chosen period of time until the measured hygrometry value of the lignocellulosic material greater than Hi+4% is stable and included in a range of values ​​less than Hi+4%; - Deactivate the heating means (2), to reduce the temperature of the drying chamber (1) according to a second phase, when the average measured hygrometry of the lignocellulosic material reaches the final target hygrometry value of maximum 1%.

6. System according to claim 3, characterized in that the control means (6) are configured to: - inject the CO2 into the pyrolysis cell (P11) and activate the gas circulation means (P4) allowing the CO2 to be forced to circulate from one end to the other of the pyrolysis cell (P11) in a closed circuit; - when a CO2 saturation greater than 90% is reached, activate the heating means (2) and heat the circulating CO2 from ambient temperature to a target temperature TP between 350°C and 390°C with a gradient of 20°C / h; - when the target temperature TP is reached, deactivate the heating means (2).

7. Pyrolysis module under CO2 atmosphere comprising: - at least one thermal distribution device (DC), configured to supply CO2 to the pyrolysis module (P1) from the CO2 source (D1) and heat the injected CO2; a pyrolysis cell (P11); - gas circulation means (P4) allowing the renewal of the atmosphere inside the pyrolysis cell (P11) - a plurality of metrology measurement units forming metrological means (P5), said pyrolysis module (P1) being further connected to a system SUBSTITUTION SHEET (RULE 26) control computer (6) and configured to carry out slow pyrolysis of a lignocellulosic material having a humidity less than or equal to 1% under a saturated CO2 atmosphere with a maximum temperature of 390°C.

8. Pyrolysis module under CO2 atmosphere according to claim 7, characterized in that the gas circulation means (P4) for forcing the circulation of CO2 from one end to the other of the pyrolysis cell (P11) according to a closed circuit in the direction of the length of said pyrolysis cell (P11) with an injection and an extraction positioned at the ends of the pyrolysis cell (P11) as well as the renewal of the atmosphere inside the pyrolysis cell (P11), and comprising a flow module configured to allow the circulation of CO2 capable of uniformizing the thermal distribution in said pyrolysis cell (P11); and in that the metrological means (5) for measuring the variations of physical measurements of the pyrolysis module (P11) during heating;and in that the computer control system (6) is configured to control the supply means (3), the circulation means (P4), the heating means (2), according to programs, setpoint values ​​and durations of rise in high temperature appropriate according to the desired pyrolysis conditions, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation.;

9. A method for producing biochar implemented by a system according to one of claims 1 to 6, comprising a drying step (S1) implemented in a drying module (C1) and a pyrolysis step (P1) implemented in a pyrolysis module (P1) of a lignocellulosic material, characterized in that: - the drying step (S1) comprises drying the lignocellulosic material under a saturating atmosphere of CO2 by raising the temperature of the CO2 circulating in the drying module (C1) according to a gradient G1 with a limit temperature of 120°C until the measured humidity of the lignocellulosic material is less than or equal to 1%; - the method comprises a transfer step (T) in which the material SUBSTITUTION SHEET (RULE 26) Dried ignocellulosic less than 1% is transferred to the pyrolysis module (P1); and - the pyrolysis step (S2) comprises injecting CO2 into the pyrolysis module (P1) in a closed circuit and heating said CO2 circulating in the pyrolysis module (P1) from ambient temperature to a maximum temperature of between 350°C and 390°C.

10. Method according to claim 9, characterized in that the gradient G1 of the drying step (S1) is 2°C / hour.

11. A method according to claim 9 or 10, characterized in that the heating of the CO2 circulating from the pyrolysis step from ambient temperature to a maximum temperature between 350°C and 390°C is carried out according to a gradient of 20°C / hour. i SUBSTITUTION SHEET (RULE 26)