CO2 sequestration thermal wood drying installation

Abstract

The invention relates to a drying installation comprising: - a drying chamber (1), - means for supplying CO2 (3); - means for circulation (213a, 213b) to force the circulation of CO2 through the drying chamber (1) in a closed circuit; - means for heating (2); - means for recycling (600) CO2; - means for metrology (5); - means for control (6); - a flow reversal module (206) configured to allow the circulation of CO2 in a first direction of circulation, and in a second direction of circulation of the drying chamber (1), and capable of uniformizing the thermal distribution in the drying chamber (1).

Description

Title of the invention: [thermal wood drying installation by CO2 sequestration]

[0001] The present invention relates to a thermal wood drying installation by CO2 sequestration, in particular but not limited to the industrial drying of timber, roundwood and / or logs and similar semi-cellulosic objects.

[0002] Here, "timber, roundwood and logs" means wood intended for use in secondary wood processing sectors, particularly for industry, building, joinery, or for urban, industrial, collective and domestic exterior and interior design.

[0003] Although various solutions exist for drying timber, roundwood and / or logs, known solutions rarely allow for industrial application with a low energy balance. Indeed, known solutions are generally used on a small scale to minimize energy consumption while obtaining wood with a low moisture content, and do not allow for drying with a neutral or negative carbon balance.

[0004] Another drawback of existing solutions is the duration of use of a drying installation, which often represents a significant period of several days, or even several weeks, a limiting factor for efficient use in industrial applications.

[0005] Moreover, current installations are too often in difficulty in achieving the objective of raising the temperature so that it is homogeneous throughout the core of a mass of wood, while obtaining a precise hygrometry of the dried wood and guaranteeing the integrity of the internal structure of the wood during and after drying.

[0006] Current drying processes and installations also have the disadvantage of only allowing a very small amount of CO2 to be sequestered in the wood to be dried.

[0007] The present invention remedies these drawbacks.

[0008] It relates to a drying installation comprising: - a drying chamber comprising at least one hollow cylindrical drying tube of appropriate diameter and length for drying wood of selected dimensions, - means of supplying CO2 to inject into the drying chamber, a heat transfer fluid in gaseous form of CO2 at chosen pressure and temperature; - means of circulation to force the circulation of CO2 through the drying chamber in a closed circuit; -heating methods to warm the circulating CO2; - means of gas circulation allowing the renewal of the atmosphere inside the drying chamber, and of extracting from the drying chamber and recycling the heat transfer gaseous fluid comprising CO2 and water in the form of vapor; - means of recycling CO2 configured to allow the separation of water vapor and gaseous CO2 present in the atmosphere extracted from the chamber during drying; -Metrological means to measure variations in the physical measurements of the drying installation during heating; and - control means to operate the means of supplying, circulating, heating, and recycling, according to appropriate programs, setpoints and drying times depending on the quality of dried wood desired, and processing means to measure, compare and readjust the operating parameters to the setpoints in case of deviation.

[0009] According to a general definition of the invention, the CO2 supply means are connected to a flow reversal module configured to allow the circulation of CO2 in a first direction of circulation in the drying chamber between a first inlet of the drying chamber and a first outlet of the drying chamber, and in a second direction of circulation between a second inlet of the drying chamber and a second outlet of the drying chamber, and suitable for uniformizing the thermal distribution in the drying chamber.

[0010] Thus, the drying installation makes it possible to obtain rapid and uniform drying of the wood, with a low deformation rate, less energy-intensive, while allowing adaptability to all types of wood thanks to the monitoring, control and feedback adjustment steps.

[0011] In practice, the flow reversal module comprises: -an injection module connected to the CO2 supply means and the heating means, and comprising a first fan, a circulation duct connected to the first inlet of the drying chamber and to the second inlet of the drying chamber, each inlet comprising respectively a solenoid valve configured to alternately allow the circulation of CO2 in the drying chamber, when one solenoid valve is in the closed position, the other solenoid valve is in the open position allowing the injection of the gas mixture at each end of the drying chamber; -an exhaust module located at the outlet of the heating chamber, connected to the first and second outlets of the drying chamber, each outlet comprising a solenoid valve configured to alternately allow the circulation of CO2 towards a second fan connected to an outlet of the drying system, and configured to allow the circulation of the gas mixture at the outlet of the drying chamber, when one solenoid valve is in the closed position, the other solenoid valve is in the open position, allowing the gas mixture to circulate at each end of the drying chamber; and -a recirculation module, located between the evacuation module, the recycling means, and the heating means, comprising a solenoid valve configured to allow / prevent the recirculation of the dehumidified gas mixture to the drying chamber.

[0012] By way of non-limiting example, the solenoid valves of the injection module and the evacuation module are configured to switch from an open position to a closed position alternately, so that when a solenoid valve is in the open position in the injection module, the solenoid valve of the evacuation module in the open position is located at the other end of the drying chamber.

[0013] According to one embodiment of the invention, the metrology means further comprise means for measuring the partial pressure of CO2, disposed at the outlet of the CO2 supply means and at the outlet of the installation, and configured to record and transmit the partial pressure of CO2 measured in the installation to a computer system for controlling the drying installation.

[0014] According to a first embodiment of the invention, the CO2 recycling means comprise a heat exchanger type system configured to cool the circulating gas mixture in order to cause the condensation of the water in said mixture and to allow the extraction of said condensed water.

[0015] According to a second embodiment of the invention, the CO2 recycling means comprise a heat exchanger type system configured to cool the wet gas mixture, and to reheat the cooled gas mixture after water extraction to a temperature of 50°C for reinjection into the drying chamber.

[0016] In practice, the heat exchanger of the CO2 recycling means is only active during the drying phase, and when the measured humidity of the circulating gas mixture is within a maximum threshold value and a minimum threshold value.

[0017] The Applicant observed that the use of a heat exchanger allowed fine control of the humidity of the gas mixture reinjected into the drying chamber and optimizes the energy efficiency of the drying installation.

[0018] By way of non-limiting example, means of supplying CO2 belong to the group formed by CO2 injection system from CO2 in pressurized bottle, CO2 supply for evacuation of methanization installation, CO2 supply of industrial chimney type, and wood drying installation by ancillary CO2 sequestration, or a combination thereof.

[0019] Furthermore, the CO2 supply means include a connection system to a CO2 source comprising at least one solenoid valve configured to allow 1'injection / T stop of CO2 injection into the drying installation.

[0020] Advantageously, the installation according to the invention allows adaptability to different sources of CO2, as well as different qualities and flow rates of CO2.

[0021] According to one embodiment of the invention, the computer control system equipped with an application programming interface (API) is configured to: -Acquire metrological data and parameters of the wood to be dried by measurement using metrological means; -Activate the heating means to adjust the moisture content of the wood by heating up to a first setpoint temperature Tl according to a chosen temperature gradient G1 if the moisture content of the wood is greater than 30%, in order to extract the free water from the wood to be dried and activate the circulatory means; -If the measured wood moisture content is less than or equal to 30%, activate the CO2 supply means configured to saturate the drying chamber with CO2 even if the setpoint temperature Tl is not reached; -stabilize the temperature of the CO2 circulating in the drying chamber in a first phase up to the setpoint temperature T1, 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 wood reaches an intermediate target value Hi chosen, the heating means being activated so that the heating is carried out up to a second setpoint temperature T2 limit of 120°C according to a chosen temperature gradient G2, and according to the specific drying profile of the wood to be dried allowing the extraction of the bound water from the wood to be dried; -Deactivate the recycling means and modulate the activity of the drying means to decrease the temperature of the heating chamber in a first phase, down to a third setpoint temperature T3 of chosen stabilization, when the measured moisture content of the wood reaches the chosen intermediate target value Hi, said setpoint temperature T3 being maintained for a chosen period of time until the measured moisture content is stable and within a chosen range of values ​​HX; and -Deactivate the heating means, to decrease the temperature of the heating chamber according to a second phase, down to the setpoint temperature Tl as long as the measured moisture content of the wood is above the final target moisture content value Hc, if the measured moisture content of the wood is less than or equal to the final target moisture content value Hc, reactivate the heating means so as to maintain the measured temperature stable for a chosen stabilization period.

[0022] Advantageously, the drying installation according to the invention also makes it possible to obtain a shrinkage of less than 5% of the wood whereas the standard shrinkage with conventional drying methods is 10 to 15%.

[0023] The Applicant also observed that the drying installation according to the invention makes it possible to obtain dried wood with lower moisture reabsorption, a reduction in the colouring of the dried wood, as well as the limitation / absence of the appearance of cracks during drying.

[0024] Other advantages and features of the invention will become apparent upon examination of the description and drawings in which:

[0025] [Fig.1] schematically represents a wood drying installation according to the invention;

[0026] [Fig.2] represents in isolation two embodiments of the means for supplying CO2 from the installation conforming to the invention;

[0027] [Fig.3] represents the drying chamber of the installation according to the invention;

[0028] [Fig.4] represents an internal immersion heater module of the heating system in accordance with the invention;

[0029] [Fig.5] represents a single-suction fan of the heating system according to the invention;

[0030] [Fig.6] schematically represents the general steps of the drying process according to the invention;

[0031] [Fig.7] schematically represents the sub-steps enabling Filling of the chamber / sensor data acquisition;

[0032] [Fig.8] schematically represents the sub-steps allowing the elimination of free water from the wood to be dried according to the invention;

[0033] [Fig.9] schematically represents the sub-steps allowing the injection of CO2 the saturation of the drying chamber according to the invention;

[0034] [Fig. 10] schematically represents the sub-steps relating to the CO2 drying step according to the invention;

[0035] [Fig. 11] schematically represents the sub-steps relating to the CO2 cooling step according to the invention; and

[0036] [Fig. 12] schematically represents the sub-steps relating to the CO2 evacuation step of the drying chamber according to the invention.

[0037] With reference to Figures 1 to 5, the drying installation according to the invention comprises several functional groups, including a heating chamber 1 having at least one drying tube into which the wood to be dried is introduced, heating means 2, CO2 supply means 3, gas circulation means 4 allowing the renewal of the atmosphere inside the drying chamber 1, and the extraction from the drying chamber and recycling of the heat transfer gas comprising CO2 and water in the form of vapor, several metrology measuring units forming metrology means 5, and finally a computer control system 6 equipped with a programming interface application API.

[0038] The installation has a drying chamber 1 composed of one or more hollow cylindrical drying tubes allowing the introduction of round wood to be dried.

[0039] By way of non-limiting example, the drying chamber 1 comprises a 2,000-liter insulated closed tube with internal atmospheric recirculation. For example, the reactor consists of: - a steel tube 5.5 meters long, closed by two steel plates (not shown) 700 mm in diameter and 3 mm thick, one bolted onto flanges with 1 inspection port closed by a steel plate 220 mm in diameter bolted onto flange, and the other fitted with a hinged door bolted onto flange on hinged studs, with an inspection port, and finally closed by a tap / valve; - a roller railway (not shown) consisting of a series of ten rollers, 4 cm in diameter and 15 cm long, spaced 70 cm apart and fixed by bolted plates; and - a threaded end closed by a cap bolt, for the placement of sensors, at the ends and in the center, fixed on the axis of the upper generator of the chamber.

[0040] According to one embodiment, the drying chamber 1 according to the invention includes a safety valve 103 is disposed in a medial position of the drying chamber 1, allowing the emergency evacuation of part of the atmosphere contained in the drying chamber 1 in the event of critical pressure in the latter.

[0041] In practice, the critical pressure at the valve can be 1.5 bar.

[0042] According to a particular embodiment of the invention, the drying chamber further has an inclination of less than 1%, having a drain solenoid valve with a gooseneck, which allows the water to be evacuated in liquid form during drying.

[0043] The drying installation further includes a heating system 2, equipped with a duct comprising a gas circulation inlet from CO2 supply means 3, the duct then leading to first circulation means or recirculation fan comprising a duct 203a, a turbine 203b, as well as an inlet 203c and an outlet 203d allowing the circulation of the gas mixture towards chamber 1 in a direction F in the heating system 2, from a heater 205 or heating cell, said recirculation fan allowing the evacuation of the atmosphere thus heated towards an injection module (206a) giving into the drying chamber 1.

[0044] According to a first alternative embodiment, the drying chamber 1 consists of a plurality of drying tubes, connected to a heating system 2 common to drying tubes.

[0045] According to a second alternative embodiment, the drying chamber 1 consists of a plurality of drying tubes, connected to a plurality of heating systems 2.

[0046] In practice, the heater 205 is an immersion heater sold under the reference "237537 electric immersion tube heater" by VULCANIC©, with a power rating of 7 W. It comprises an inlet 206 through which the gases to be heated enter the heater 205, an open cylindrical steel conduit 208 into which an immersion heater 209 is inserted and fixed to one of the openings, and finally a second outlet 207 for the heated gases. Downstream of the conduit 208, before the outlet 207, are a thermostat 210 for regulating the temperature of the immersion heater 209 and a temperature probe 211.

[0047] By way of non-limiting example, the heating system 2 comprises a spiral duct circuit, made of galvanized steel sheet approximately 8 m long, supplying a heating extraction box equipped with a helical fan 203 with a remote low-pressure motor of 9.5 NmVmin, as well as a thermostatically controlled 2 x 3.5 kW heater 205, the whole insulated by a 20 cm thick glass wool envelope.

[0048] The drying chamber further includes metrology means 5, enabling the measurement of various physical characteristics. The instruments included in the drying chamber 1 are, for example:

[0049] - at least two individual load cells 503a / 503b / 503c / 503d, distributed under the chamber and allowing monitoring of the mass of the drying tube, and thus knowing the mass of the wood load being dried, indicating the progress of the drying;

[0050] - at least two individual temperature transmitters placed on the wood, positioned at the center of the log 501a / 501b / 501c as well as at its periphery 502a / 502b / 502c, thus allowing precise real-time monitoring of the temperature at several points in chamber 1, as well as in the wood load, in order to avoid damaging the log during drying and to optimize drying by fine regulation;

[0051] - three individual hygrometer / thermometer assemblies arranged upstream 504a, at center 504b, and downstream 504c in drying chamber 1;

[0052] - a pressure transmitter assembly 506a and pressure gauge 506b allowing recording the pressure inside the drying chamber 1.

[0053] Each metrological measurement includes a setpoint value or a group of setpoint values ​​to be respected, specific to each type of wood.

[0054] The heating installation according to the invention further comprises a gas mixture circulation circuit having circulation means 213a, 213b for forcing the circulation of the gas mixture according to a closed circuit, through the drying chamber 1.

[0055] By way of non-limiting example, the circulation means 213a, 213b, include a first fan 213a allowing the circulation of the gas mixture towards the drying chamber 1, and a second fan 213b allowing the circulation of the gas mixture out of the drying chamber 1 towards the gas mixture circulation circuit.

[0056] In practice, first circulation means 213a can be of the type medium pressure centrifugal fan and single suction with duct 203b and turbine 203a made of sheet steel, said fan comprising a turbine 203a with forward inclined blades made of galvanized sheet steel, the fan 203 being able to withstand a maximum temperature of the air to be transported from -20°C to 250°C.

[0057] The first fan 213a is integrated into an injection module 206a, and arranged at the outlet of the heating means 2.

[0058] The injection module 206a is configured to inject the gas mixture into the drying chamber 1, and is connected to CO2 supply means 3 and heating means 2.

[0059] Said injection module 206a includes the first fan 213a, a circulation duct 204 connected to the first inlet 201 of the drying chamber 1 and to the second inlet 202 of the drying chamber 1, each inlet 201, 202 comprising respectively a solenoid valve EV3, EV4 configured to alternately allow the circulation of CO2 in the drying chamber 1, when one solenoid valve EV3, EV4 is in the closed position, the other solenoid valve EV3, EV4 is in the open position, thus allowing the injection of the gas mixture at each end of the drying chamber 1.

[0060] The second fan 213b is integrated into an exhaust module 206a, and is located at the outlet of the heating means 2.

[0061] The exhaust module 206b is arranged at the outlet of the heating chamber 1, and connected to the first outlet 204 and the second outlet 205 of the drying chamber 1, each outlet 204, 205 comprising respectively a solenoid valve EV2,EV1 configured to alternately allow the circulation of CO2 towards the second fan 203b connected to an outlet 701 of the drying installation, and configured to allow the circulation of the gas mixture at the outlet of the drying chamber 1 so that when one solenoid valve EV2,EV1 is in the closed position, the other solenoid valve EV2,EV1 is in the open position, the circulation of the gas mixture then taking place alternately at each end of the drying chamber 1 according to a frequency chosen during the drying of the wood.

[0062] The injection module 206a and the evacuation module 206b form a module flow reversal 206 configured to allow CO2 to circulate in a first direction in the drying chamber 1 between a first inlet 201 of the drying chamber 1 and a first outlet 204 of the drying chamber 1, and in a second direction between a second inlet 202 of the drying chamber 1 and a second outlet 205 of the drying chamber 1, and suitable for uniformizing the thermal distribution in the drying chamber 1.

[0063] Indeed, the solenoid valves EV1, EV2, EV3, EV4 of the injection module 206a and the evacuation module 206b are configured to switch from an open position to a closed position alternately, so that when a solenoid valve EV3, EV4 is in the open position in the injection module 206a, the solenoid valve EV1, EV2 of the evacuation module 206b in the open position is located at the other end of the drying chamber 1.

[0064] Advantageously, the alternating circulation of CO2 in the injection module 206a and the exhaust module 206b makes it possible to maintain a uniformity of the temperature of the gas mixture in the drying chamber 1 and thus allow drying of the wood and uniform sequestration of CO2 in the wood.

[0065] The Applicant observed that the use of the flow reversal module 206 also makes it possible to limit the presence of water in liquid form in the drying chamber 1, and thus make optional the use of an inclined drying chamber and a gooseneck type disposal system to remove water in liquid form which may accumulate at the base of the drying chamber 1.

[0066] In addition, such uniformity of drying makes it possible to obtain a shrinkage of less than 5%, unlike a standard shrinkage of 10 to 15% with conventional drying methods.

[0067] According to a particular embodiment, the drying installation according to the invention further comprises a recirculation module 206c, disposed between the evacuation module 206b, the recycling means 600, and the heating means 2, and comprising a solenoid valve EV5 configured to allow / prevent the recirculation of the dehumidified gas mixture to the drying chamber 1.

[0068] The recirculation module 206c is configured to allow the reinjection of a gas mixture into the injection module 206a, or the sending of the gas mixture to an outlet 701 of the drying installation.

[0069] In addition, the CO2 recycling means 600 allow the separation of water vapor and gaseous CO2 present in the atmosphere extracted from chamber 1 during drying, in order to be able to remove the water while recovering the CO2 for storage, or to be directly reused in the installation.

[0070] By way of non-limiting example, condensing recycling means 600 are used, reducing the temperature of the binary gas mixture water vapor / CO2 extracted from drying chamber 1 to a chosen temperature, allowing the water in the mixture to condense, which is then recovered by gravity in liquid form and disposed of.

[0071] For example, the recycling means 600 allow the internal atmosphere extracted from the drying chamber 1 to be dried via a thermal condensation system of water vapor by cooling, on a cold wall equipped with a heat exchanger. The system thus allows the dehydrated atmosphere to be reinjected into the drying chamber 3.

[0072] According to one embodiment of the invention, the heat exchanger of the recycling means 600 is only active when the humidity of the circulating gas mixture is between two threshold values.

[0073] In practice, the heat exchanger of the CO2 recycling means 600 is only active during the drying phase, and when the measured humidity of the circulating gas mixture is within a maximum threshold value and a minimum threshold value.

[0074] In practice, the heat exchanger of the recycling means 600 also allows the dehydrated gas mixture to be heated before reinjection via the injection module 206a.

[0075] According to a particular embodiment of the invention, the heat exchanger is configured to reheat the cooled gas mixture after water extraction to a temperature of 50°C for reinjection into the drying chamber 1.

[0076] Advantageously, the recycling means 600 make it possible to control the hygrometry of the gas mixture and thus minimize the environmental variations of the wood to be dried, thereby optimizing the drying of the wood and the sequestration of CO2, while limiting the energy expenditure to maintain a low temperature difference between the CO2 exiting the heating means 2 and coming from the recirculation module 206c.

[0077] In practice, the CO2 gas recovered by the recycling means 600 can be stored, or directly reinjected into the drying chamber 1.

[0078] According to a particular embodiment of the invention, the drying chamber 1 has an inlet, which is followed by a so-called "breathing" duct comprising a check valve followed by a breathing solenoid valve for the drying chamber 1, which allows the injection of air from outside the installation into the drying chamber 1.

[0079] The drying installation according to the invention further includes an outlet 701 connected to the evacuation module 206b.

[0080] According to a first embodiment of the invention, outlet 701 is connected to a second drying installation and has a solenoid valve 700a configured to to allow / prevent the circulation of the gas mixture at the outlet, solenoid valve 700a being equipped with a counting device consisting of a manometer / thermometer assembly 302 and a volume / flowmeter assembly 303 configured to measure the quantity of CO2 at the outlet of the installation.

[0081] According to a second embodiment of the invention, the outlet 701 is connected to a recycled CO2 storage installation, and has a solenoid valve 700b configured to allow / prevent the circulation of the gas mixture at the outlet, solenoid valve 700b being equipped with a metering device consisting of a manometer / thermometer assembly 302 and a volume / flowmeter assembly 303 configured to measure the quantity of CO2 at the outlet of the installation.

[0082] According to a third embodiment of the invention, the outlet 701 is connected to a second drying installation, and has a solenoid valve 700a configured to allow / prevent the circulation of the gas mixture at the outlet, solenoid valve 700a being equipped with a metering device consisting of a manometer / thermometer assembly 302 and a volume / flowmeter assembly 303 configured to measure the quantity of CO2 at the outlet of the installation, and connected to a recycled CO2 storage installation, and has a solenoid valve 700b configured to allow / prevent the circulation of the gas mixture at the outlet, solenoid valve 700b being equipped with a metering device consisting of a manometer / thermometer assembly 302 and a volume / flowmeter assembly 303 configured to measure the quantity of CO2 at the outlet 701 of the installation.

[0083] In practice, the metering module further includes means for measuring the partial pressure of CO2 700b, arranged at the outlet (701) of the installation, and configured to record and transmit the partial pressure of CO2 measured in the installation to a computer control system (6) of the drying installation.

[0084] The drying installation further comprises means for supplying CO2 3, which include a CO2 source belonging to the group formed by biogenic CO2, non-biogenic CO2.

[0085] According to a first embodiment of the invention, the CO2 supply means 3 have at least one CO2 supply unit 301 comprising two slots for standard "Air-Liquide" type cylinders, each containing 34 kg of liquid CO2 compressed to 50 bar, and the corresponding pressure-reducing device(s), namely a gaseous CO2 pressure-reducing device consisting of a primary pressure reducer (not shown) allowing the pressure to decrease from 70 bar to 3 bar (0.5 m³ / h), and a secondary pressure-reducing regulator allowing the pressure to decrease from 3 bar to 0.3 bar (5 m³ / h). The supply means 3 further have a shut-off solenoid valve 304 preceded by an atmospheric CO2 metering device 302 / 303, the solenoid valve controlling the supply to a fixed atmospheric line 306.

[0086] The CO2 supply means 3 then comprise a device for putting into circulation Circulation 307 of the gas allows air to be drawn at ambient temperature to the heating system 2. The circulation device 307 includes an air compressor 308 that ejects pressurized air into a pipe that splits in two. The first branch allows the compressed air to circulate to a pressure regulator 309, which then allows the reduced-pressure air to circulate to solenoid valves 101b and 102a, located respectively at the inlet 101 and outlet 102 of the drying chamber 1. A second branch of the pipe allows the compressed air to circulate to a pressure regulator 310, which reduces the pressure of the injected air to a solenoid valve 311. This valve controls the quantity of air introduced into the circuit and includes a non-return valve 312. The valve then opens into the atmospheric circulation pipe 306, which joins the duct 204 of the heating system 2 upstream of the means traffic 213a.

[0087] According to an alternative embodiment of the invention, the atmospheric circulation pipe 306 directly joins at least one injection module 206a connected to the drying chamber 1.

[0088] According to another alternative embodiment, the CO2 supply means 3 comprise at least one CO2 supply module referred to as "new", and one CO2 supply module referred to as "recycled", connected to the drying installation by a connection system (30,31) to a CO2 source comprising at least one solenoid valve (EVC1, EVC2) configured to allow the injection / stopping of the injection of CO2 into the drying installation.

[0089] New CO2 means CO2 in a pressurized bottle (301).

[0090] Recycled CO2 means CO2 originating from a CO2 feedstock, the exhaust of a methanization plant, an industrial chimney-type CO2 feedstock, and a wood drying plant using CO2 sequestration (annex).

[0091] According to a non-limiting example, the CO2 supply means (3) belong to the group formed by CO2 injection system from pressurized bottle CO2 (301), CO2 supply for evacuation of methanization plant, CO2 supply of industrial chimney type, and wood drying plant by CO2 sequestration annex, or a combination thereof.

[0092] The CO2 supply means 3 include a metering device consisting of a manometer / thermometer assembly 302 and a volume / flowmeter assembly 303. The injected and decompressed CO2 supply line then includes a non-return valve and finally joins an atmospheric circulation line 306 to the heating means 3.

[0093] The metering module further includes means for measuring the partial pressure of CO2 700a, arranged at the outlet of the CO2 supply means (3) and at the outlet (701) of the installation, and configured to record and transmit the partial pressure of CO2 measured in the installation to a computer control system (6) of the drying installation.

[0094] By way of example, the means for measuring the partial pressure of CO2 700a,700b include a gas chromatograph type device 700a, disposed at the outlet of the CO2 supply means, and configured to analyze the composition of the gas mixture at the outlet of said CO2 supply means and thus measure the quantity of CO2 at the inlet of the installation.

[0095] Advantageously, by comparing the quantity of CO2 at the inlet of the installation and at the outlet 701, it is possible to measure the saturation rate of CO2 circulating in said installation and thus guarantee a minimum saturation rate to optimize the drying environment in the drying chamber 1.

[0096] The drying installation also incorporates a computer control system 6 including an application programming interface (API). The application programming interface allows, on the one hand, the management of sending instructions to each of the components of the installation, and on the other hand, the integration of data received by the various metrology means 5, in order to adjust the instructions sent to the components of the installation.

[0097] The computer control system 6 is configured to control the feeding means 3, circulation 213a, 213b, heating 2, and recycling 600 according to appropriate programs, setpoint values ​​and drying times depending on the quality of the dried wood desired, and the processing means to measure, compare and readjust the operating parameters to the setpoint values ​​in case of deviation.

[0098] In practice, the computer control system 6, equipped with an application programming interface (API), is configured to: -Acquire metrological data and parameters of the wood to be dried by measurement using metrological means 5; -Activate the heating means 2 to adjust the moisture content of the wood by heating up to a first setpoint temperature Tl according to a temperature gradient chosen G1 if the moisture content of the wood is greater than 30%, in order to extract the free water from the wood to be dried and activate the circulator means 203a, 203b; -If the measured wood moisture content is less than or equal to 30%, activate the CO2 supply means 3 configured to saturate the drying chamber 1 with CO2 even if the setpoint temperature Tl is not reached; -stabilize the temperature of the CO2 circulating in drying chamber 1 in a first phase up to the setpoint temperature T1, activate the recycling means 600 then increase in a second phase the temperature of the CO2 circulating in drying chamber 1 until the measured moisture content of the wood reaches a intermediate target value Hi chosen, heating means 2 being activated so that heating is carried out up to a second setpoint temperature T2 limit of 120°C according to a chosen temperature gradient G2, and according to the specific drying profile of the wood to be dried allowing the extraction of bound water from the wood to be dried; -Deactivate the recycling means 600 and modulate the activity of the drying means 2 to decrease the temperature of the heating chamber 1 in a first phase, down to a third setpoint temperature T3 of selected stabilization, when the measured moisture content of the wood reaches the selected intermediate target value Hi, said setpoint temperature T3 being maintained for a selected period of time until the measured moisture content is stable and within a selected range of values ​​HX; and -Deactivate heating means 2, to decrease the temperature of heating chamber 1 according to a second phase, down to the setpoint temperature Tl as long as the measured moisture content of the wood is above the final target moisture content Hc, if the measured moisture content of the wood is less than or equal to the final target moisture content Hc, reactivate heating means 2 so as to maintain the measured temperature stable for a chosen stabilization period.

[0099] With reference to Figures 6 to 12, the CO2 drying and sequestration installation described with reference to Figures 1 to 5 implements a process for drying and sequestration of CO2 in wood comprising a succession of steps according to the following sequence:

[0100] According to a first step of acquiring metrological data and parameters of the wood to be dried SI, measure the different parametric data to calibrate the setpoint values ​​to be applied, via metrology means 5.

[0101] In practice, the step of acquiring metrological data and parameters of the wood to be dried SI comprises the following sub-steps: -Fill the drying chamber with the object to be dried SI 1; -Measure the surface and core temperature of the wood S12; -Measure the moisture content of the wood to be dried S13; -Measure the temperature of the drying chamber S14; -Measure the humidity level in drying chamber S15; and -Measure the weight of the wood to be dried S16.

[0102] By way of example, the wood to be dried is inserted into the drying chamber 1, then the drying chamber is hermetically sealed.

[0103] In practice, the difference between the surface and core temperature of the wood must be less than or equal to 20°C.

[0104] Furthermore, the substep for measuring the weight of the wood to be dried S16 allows the calculation of the mass loss associated with the implementation of the drying process and thus quantify the amount of water extracted, taking into account the amount of CO2 sequestered.

[0105] By way of non-limiting example, the maximum amount of CO2 sequestered is 250kg / m3 of wood.

[0106] According to a second step of adjusting the hygrometry of the wood S2, suitable for removing free water from the wood, if the hygrometry of the wood is greater than 30%, the drying chamber 1 is heated up to a first setpoint temperature Tl according to a chosen temperature gradient Gl.

[0107] In practice, if the moisture content of the wood is less than or equal to 30%, a third CO2 saturation stage S3 is implemented, even if the setpoint temperature Tl has not yet been reached.

[0108] The step of adjusting the moisture content of wood S2 comprises the following sub-steps: -Measure the moisture content of the wood in real time S21;

[0109] - If the measured humidity is greater than 30%, increase the temperature of the tube drying from ambient temperature S22 until the measured humidity is less than or equal to 30%, the temperature increase being carried out according to a chosen temperature gradient Gl, and limited to a first setpoint temperature Tl; and

[0110] -If the measured humidity is less than or equal to 30%, saturate the drying chamber 1 with CO2 S3.

[0111] By way of non-limiting example, the first setpoint temperature Tl is between 50°C and 60°C.

[0112] By way of non-limiting example, the chosen temperature gradient Gl is 2°C / hour.

[0113] According to a third CO2 saturation stage S3 of the drying chamber, the CO2 supply means 3 inject CO2 into the drying chamber 1 until the CO2 saturation reaches a chosen value.

[0114] The CO2 saturation step S3 comprises the following substeps: -Check that the setpoint temperature Tl is reached in the drying chamber S31; -Inject S32 CO2 from CO2 supply means 3; -Measure using measuring means 700a,700b, arranged at the outlet of the CO2 supply means 3 and at the outlet 701 of the installation the partial pressure of CO2 S33; -Compare the partial pressure of CO2 at the inlet and outlet of S34; and - Stop CO2 injection and activate CO2 recycling means when the CO2 partial pressure ratio at the inlet / outlet is greater than or equal to a target R value chosen S35.

[0115] In practice, the injection is implemented via an injection module 206a.

[0116] By way of example, the CO2 saturation in the drying chamber 1 is measured by gas chromatography, by sampling carried out via metrology means 5 arranged at the inlet and outlet of the drying chamber 1.

[0117] By way of non-limiting example, when the ratio R= P[CO2] input / P[CO2] output is between 0.8 and 1, CO2 saturation is sufficient, CO2 injection is stopped.

[0118] According to a fourth drying step S4, the CO2 circulating in the drying chamber 1 is heated S4 to the setpoint temperature T1 in the drying chamber 1 in a first phase, then the CO2 circulating in the drying chamber 1 is heated in a second phase until the measured moisture content of the wood reaches a chosen intermediate target value Hi, the heating being carried out up to a second setpoint temperature T2 limit of 120°C according to a temperature gradient G2 chosen according to the specific drying profile of the wood to be dried, allowing the extraction of the specific bound water of the wood to be dried

[0119] The heating step S4 comprises the following substeps: -Increase the temperature of drying chamber 1 according to a chosen temperature gradient G2, with a setpoint temperature T2 S41 as the limit temperature - Engage the activation / deactivation of CO2 flow reversal means according to a chosen frequency Fl S42 configured to reverse the direction of the CO2 flow in the drying chamber 1; -Activate dehumidification means S43 of drying chamber 1; -Measure the moisture content of S44 wood in real time; and -if the measured hygrometry of the wood is less than or equal to an intermediate hygrometry value Hi of the wood, stabilize S45 the temperature of the drying chamber 1 even if the setpoint temperature T2 is not reached.

[0120] In addition, the temperature increase S41 is carried out in two phases.

[0121] A first phase consists of heating the CO2 circulating in the drying chamber 1 up to the setpoint temperature Tl in the drying chamber 1.

[0122] A second phase consists of heating the CO2 circulating in the drying chamber 1 until the measured hygrometry of the wood reaches a chosen intermediate target value Hi, the heating being carried out up to a second limit setpoint temperature T2 according to a temperature gradient chosen G2 according to the specific drying profile of the wood to be dried allowing the extraction of the specific bound water of the wood to be dried.

[0123] By way of non-limiting example, the second setpoint temperature T2 is included between 100 and 120°C.

[0124] By way of non-limiting example, the chosen temperature gradient G2 is between 1 and 7°C / hour.

[0125] In practice, the chosen intermediate target value Hi of the measured wood moisture content is equal to the desired final target moisture content Hc + 1.5 to 2.5%.

[0126] In practice, the temperature gradient G2 is chosen according to the specific drying profile of the wood to be dried, allowing the extraction of bound water from the wood to be dried, and dynamic, so as to be adjusted when approaching the intermediate target value Hi of the chosen wood moisture content.

[0127] By way of non-limiting example, the pressure measured in the drying chamber is between 0.8 and 1 bar.

[0128] According to a fifth temperature reduction step according to a first phase S5 of the drying chamber 1, the temperature of the heating chamber (1) is reduced until the wood to be dried reaches a measured moisture content within a range of selected target moisture content values ​​HX, the temperature reduction having a minimum limit value defined as a third stabilization setpoint temperature T3.

[0129] In practice, the temperature reduction step according to a first phase S5 comprises the following sub-steps: - when the measured moisture content of the wood reaches the chosen intermediate target value Hi, decrease the temperature in the drying chamber 1 to a chosen stabilization setpoint temperature T3 S51; - Stabilize the measured moisture content of the wood to be dried within a range of target moisture values ​​HX S52; and - when the target humidity range HX is reached, stabilize the wood temperature reached for a chosen duration D, even if the setpoint temperature T3 is not reached S53.

[0130] By way of non-limiting example, the third setpoint temperature T3 is between 60 and 100°C.

[0131] By way of non-limiting example, the range of target humidity values ​​HX is between a final target humidity value Hc, and a final target humidity value of 1.1 Hc (i.e. 110% of Hc).

[0132] During this temperature reduction step according to a first phase S5, when the measured hygrometry of the wood reaches the chosen intermediate target value Hi, said temperature of the drying chamber is reduced to a limit setpoint temperature T3.

[0133] In practice, when the measured humidity is stable and within a chosen range of HX values, the temperature of the drying chamber is stabilized, and maintained for a chosen duration D, even if the setpoint temperature T3 is not reached.

[0134] By way of non-limiting example, duration D is 2 hours.

[0135] Advantageously, stabilizing the temperature for a chosen duration D when the measured humidity reaches a value within a range of chosen target humidity values ​​HX allows for hygroscopic rebalancing of the wood to be dried.

[0136] According to a sixth step, the temperature reduction step according to a second phase S6, the temperature of the heating chamber 1 is reduced to the setpoint temperature Tl (Tl less than T3) as long as the measured moisture content of the wood is greater than the final target moisture content Hc, if the measured moisture content of the wood is less than or equal to the final target moisture content Hc, maintain the measured temperature constant for a chosen stabilization period.

[0137] In practice, the temperature reduction step according to a second phase S6 comprises the following sub-steps: -Deactivate the CO2 flow reversal means and the CO2 recycling means S61 -if the measured moisture content of the wood is higher than the final target value Hc, decrease the temperature S62 of the drying chamber 1 to the setpoint temperature Tl according to a gradient chosen G3 by progressively deactivating heating means 2; -if the measured moisture content of the wood is less than or equal to the final target value Hc, stabilize the measured temperature in the drying chamber 1 for a chosen duration, even if the setpoint temperature Tl is not reached S63.

[0138] By way of non-limiting example, the chosen temperature gradient G3 is 2°C / hour.

[0139] In practice, the temperature gradient G3 is chosen to be identical, regardless of the specific drying profile of the wood to be dried, and dynamic, so as to be adjusted when approaching the final target value Hc of the chosen wood moisture content.

[0140] By way of non-limiting example, the final target value Hc is between 0% and 18%.

[0141] The process according to the invention further includes a CO2 removal step S7, configured to desaturate the drying chamber with CO2 to extract the dried wood when the measured moisture content of the wood is less than or equal to the final target value Hc, and after temperature stabilization for the chosen duration.

[0142] All steps of the process are controlled and carried out via a series of commands fully automated by the computer control system 6, which includes an application programming interface (API). The API, executing a control program, sends different instructions to each of the components. control and receives recording data from the metrology instruments 5 of the drying installation, which allows the control components to be adjusted in order to optimize drying in case of deviation from the setpoint values.

[0143] The drying profile is specific for each type of wood, each type of wood therefore having a hygrometric evolution curve in the heart of the wood as a function of its own drying time and specific associated temperature increase sequences, which dictate the temperature increase profile to be applied during the heating phases, and serves as a basis for comparison with the recorded metrological measurements so that the control system 6 can readjust these same measurements to setpoint values, in order to obtain optimal and industrial drying of the wood load.During each of the temperature increase phases S2, S4 and decrease phases S5, S6, the thermostat 210 of the heater 205, as well as the real-time metrology measurement recording systems, allow the power of the heater 205 to be adjusted by feedback effect of the thermostat 210 on the heater 205, as well as the modulation of the CO2 circulation systems.

[0144] In practice, temperature gradients Gl, G2, G3 of the first phase 901 and of the second phase 902 of drying are modulated by the control means 6, so as to control the evolution of the hygrometry in the heartwood of the piece of wood during drying.

[0145] In practice, since the humidity is variable in the wood to be dried, the following are monitored by metrological measurements: ambient humidity, average humidity, minimum humidity, and maximum humidity, for example.

[0146] Recording the control of the sequences of setpoint values ​​associated with the observed measurements makes it possible to establish a specific drying hygrometric profile of the wood species to be treated, and thus define the feedback adjustments by the control system 6 for woods of the same species during subsequent drying operations, and thus industrialize the drying while maintaining the conservation of the macromolecular structure of the dried wood with a substitution of bound water by CO2.

[0147] By way of non-limiting example, the feedback adjustments made by the control means 6 are obtained by modifying the operation of the heater 205 and the gas mixture circulation means 213a, 213b. These adjustments allow, on the one hand, the maintenance of a maximum temperature difference of 20°C between the temperature recorded at the core of the wood and the temperature of the atmosphere in the drying chamber 1, and on the other hand, the adaptation of the drying of a wood species to a specific profile.

[0148] The second heating phase optimizes the substitution of CO2 for H2O linked to the cellulose in the wood being dried. This CO2 / H2O substitution ensures the "structural" molecular integrity of the "cellulose lamination", and thus of the dried wood. Therefore, precise, multi-parameter control of the drying environment, the humidity of the wood being dried, and the temperature in the drying chamber 1 is necessary.

[0149] Instrumentation and control based on metrological measurements of the internal environment of the drying chamber 1 and of the wood make it possible to prevent damage to the wood during drying, as all drying induces unavoidable material shrinkage, although this is mitigated by the substituted CO2. In the event of poor control, the structural quality of the resulting dried wood can be significantly affected.

[0150] Cracks and sagging of the wood may appear as a result of poor piloting and thus compromise the structural integrity of the dried wood obtained by the process according to the invention, thereby generating a product not in accordance with the invention.

[0151] The process according to the invention therefore makes it possible, through fine regulation of the hygrometry of the wood, to obtain a dried wood of precise hygrometry, with a shrinkage less than or equal to 5%, a negligible deformation rate, and with a limitation, or even elimination, of the appearance of cracks in the wood.

Claims

Claims

1. Installation for thermal drying of wood by CO2 sequestration comprising: - a drying chamber (1) comprising at least one hollow cylindrical drying tube of diameter and length suitable for drying wood of chosen dimensions, - CO2 supply means (3) for injecting into the drying chamber (1) a heat transfer fluid in the gaseous form of CO2 at a chosen pressure and temperature; - circulation means (213a, 213b) for forcing the circulation of CO2 through the drying chamber (1) in a closed circuit; - heating means (2) for heating the circulating CO2; - gas circulation means (4) allowing the renewal of the atmosphere inside the drying chamber (1), and for extracting from the drying chamber and recycling the heat transfer gaseous fluid comprising CO2 and water in the form of steam; - CO2 recycling means (600) configured to allow the separation of water vapor and gaseous CO2 present in the atmosphere extracted from chamber 1 during drying; - metrology means (5) for measuring variations in physical measurements of the drying installation during heating; and - a computer control system (6) for controlling the supply means (3), circulation means (213a, 213b), reheating means (2), and recycling means (600), according to appropriate programs, setpoint values ​​and drying times depending on the quality of the desired dried wood, and processing means for measuring, comparing and readjusting the operating parameters to the setpoint values ​​in the event of a deviation;characterized in that the CO2 supply means (3) are connected to a flow inversion module (206) configured to allow the circulation of CO2 in a first direction of circulation in the drying chamber (1) between a first inlet (201) of the drying chamber (1) and a first outlet (204) of the drying chamber (1), and in a second direction of circulation between a second inlet (202) of the drying chamber (1) and a second outlet (205) of the drying chamber (1), and capable of uniformizing the thermal distribution in the drying chamber (1).;

2. Drying installation according to claim 1, characterized in that the

3. flow reversal module (206) comprises: -an injection module (206a) connected to the CO2 supply means (3) and to the heating means (2), and comprising a first fan (213a), a circulation duct (204) connected to the first inlet (201) of the drying chamber (1) and to the second inlet (202) of the drying chamber (1), each inlet (201, 202) respectively comprising a solenoid valve (EV3, EV4) configured to alternately allow the circulation of CO2 in the drying chamber (1), when one solenoid valve (EV3, EV4) is in the closed position, the other solenoid valve (EV3, EV4) is in the open position allowing the injection of the gas mixture at each end of the drying chamber (1); - an evacuation module (206b) arranged at the outlet of the heating chamber (1), connected to the first outlet (204) and to the second outlet (205) of the drying chamber (1), each outlet (204, 205) respectively comprising a solenoid valve (EV2, EV1) configured to alternately allow the circulation of CO2 towards a second fan (203b) connected to an outlet (701) of the drying installation, and configured to allow the circulation of the gas mixture at the outlet of the drying chamber when one solenoid valve (EV2, EV1) is in the closed position, the other solenoid valve (EV2, EV1) is in the open position allowing the circulation of the gas mixture at each end of the drying chamber (1); and - a recirculation module (206c), arranged between the evacuation module (206b), the recycling means (600), and the heating means (2), comprising a solenoid valve (EV5) configured to allow / prevent the recirculation of the dehumidified gas mixture towards the drying chamber (1). Drying installation according to claim 2, characterized in that the solenoid valves (EV1, EV2, EV3, EV4) of the injection module (206a) and of the evacuation module (206b) are configured to move from an open position to a closed position alternately, so that when a solenoid valve (EV3, EV4) is in the open position in the injection module (206a), the solenoid valve (EV1, EV2) of the evacuation module (206b) in the open position is arranged at the other end of the drying chamber (1). Drying installation according to one of claims 1 to 3, characterized in that the metrology means (5) further comprise means for measuring the partial pressure of CO2 (700a, 700b), arranged at the outlet of the CO2 supply means (3) and at the outlet (701) of the installation, and configured to record and transmit the partial pressure of CO2 measured in the installation to a computer system (6) for controlling the drying installation.

5. Drying installation according to one of claims 1 to 4, characterized in that the CO2 recycling means (600) comprise a heat exchanger type system configured to cool the circulating gas mixture in order to cause condensation of the water in said mixture and allow extraction of said condensed water.

6. Drying installation according to claim 5, characterized in that the CO2 recycling means (600) comprise a heat exchanger type system configured to reheat the cooled gas mixture after extraction of the water to a temperature of 50°C for reinjection into the drying chamber (1).

7. Drying installation according to claim 5 or 6, characterized in that 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.

8. Drying installation according to one of claims 1 to 7, characterized in that the CO2 supply means (3) belong to the group formed by CO2 injection system from CO2 in pressurized bottle (301), CO2 supply from evacuation of methanization installation, CO2 supply of industrial chimney type, and wood drying installation by CO2 sequestration annex, or a combination of them.

9. Drying installation according to one of claims 1 to 8, characterized in that the CO2 supply means (3) comprise a connection system (30, 31) to a CO2 source comprising at least one solenoid valve (EVC1, EVC2) configured to allow the injection / stopping of the injection of CO2 into the drying installation.

10. Drying installation according to one of claims 1 to 9, characterized in that the computer control system (6) equipped with an API application programming interface is configured to: -Acquire metrological data and parameters of the wood to be dried by measuring the metrological means (5); -Activate the heating means (2) to adjust the hygrometry of the wood by heating to a first set temperature Tl according to a chosen temperature gradient G1 if the hygrometry of the wood is greater than 30%, in order to extract the free water from the wood to be dried and activate the circulating means (203a, 203b); -If the measured wood humidity is less than or equal to 30%, activate the CO2 supply means (3) configured to saturate the drying chamber (1) with CO2 even if the set temperature Tl is not reached; - stabilize the temperature of the CO2 circulating in the drying chamber (1) according to a first phase up to the set temperature T1, activate the recycling means (600) then increase according to a second phase the temperature of the CO2 circulating in the drying chamber (1) until the measured hygrometry of the wood reaches a chosen intermediate target value Hi, the heating means (2) being activated so that the reheating is carried out up to a second set temperature T2 limit of 120°C according to a chosen temperature gradient G2, and according to the specific drying profile of the wood to be dried making it possible to extract the bound water from the wood to be dried; - Deactivate the recycling means (600) and modulate the activity of the drying means (2) to reduce the temperature of the heating chamber (1) according to a first phase, down to a third chosen stabilization setpoint temperature T3, when the measured hygrometry of the wood reaches the chosen intermediate target value Hi, said setpoint temperature T3 being maintained for a chosen period of time until the measured hygrometry is stable and included in a chosen range of values ​​HX; and - Deactivate the heating means (2), to reduce the temperature of the heating chamber (1) according to a second phase, down to the set temperature Tl as long as the measured hygrometry of the wood is higher than the final target hygrometry value Hc, if the measured hygrometry of the wood is lower than or equal to the final target hygrometry value Hc, reactivate the heating means (2) so as to keep the measured temperature stable for a chosen stabilization period.

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