Terrace temperature control type wood drying and carbonizing method

Abstract

The invention relates to an echelon temperature control type wood drying and carbonizing method, and belongs to the technical field of carbonization processing. Step S10, raw material and temperature control system pretreatment; s20, preheating starting is conducted, temperature gradient A heating treatment is conducted on the first drying chamber, after the drying chamber enters a temperature gradient B heating treatment stage, an exchange pump between the drying chamber and the second drying chamber is started, and waste heat is guided into the second drying chamber for temperature gradient A heating treatment; s30, drying transition is conducted, specifically, the first drying chamber guides the second drying chamber to conduct heating treatment at the temperature gradient B, and therefore the second drying chamber guides the third drying chamber to conduct heating treatment at the temperature gradient A; step S40, carbonization and curing: carrying out carbonization treatment on the first drying chamber; s50, deep curing and waste heat relay are carried out; and S60, cooling and wood output are conducted, and output and replacement of the processed wood are conducted. The technical problems that a large amount of waste heat is brought out and the heat recovery efficiency is low due to the fact that a circulating air box is needed for air circulation are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of carbonization processing, and in particular relates to an echelon temperature-controlled wood drying and carbonization method. Background Art

[0002] During the modification and processing of wood, drying and carbonization treatment is usually adopted. In order to ensure the degree of drying and carbonization, the existing technology uses a tiered temperature control method to dry the wood and finally perform carbonization treatment.

[0003] Patent publication number CN111216208B discloses a wood carbonization treatment method and equipment, which comprises the following steps: (1) stacking the wood in a carbonization box for moisture balance treatment, wherein the temperature in the carbonization box is 60-120°C, the humidity is 100%RH, the operation time is 96 hours, and the temperature is increased in stages; (2) drying the wood, wherein the temperature in the carbonization box is 100-120°C, the humidity is 100-20%RH, the humidity gradient decreases, and the operation time is 72 hours; (3) carbonizing the wood, raising the temperature in the carbonization box from 120°C to a carbonization temperature of 190-220°C, increasing by 10°C every 2 hours; the carbonization speed is 10 mm / hour; (4) after the carbonization treatment is completed, the ambient temperature in the carbonization box is gradually reduced from above 150°C to 60°C by adding steam humidification; and the wood can be taken out when the temperature of the carbonization box is close to the outdoor temperature.

[0004] The existing technology has at least the following problems during use:

[0005] During the carbonization process, the carbonization box needs a circulating bellows for air circulation. During the air circulation process, a large amount of waste heat will be brought out, and the heat recovery efficiency is low. Summary of the Invention

[0006] The present invention provides a tiered temperature-controlled wood drying and carbonization method, which is used to solve the technical problem in the prior art that during the carbonization process, a carbonization box requires a circulating bellows for air circulation, which will bring out a large amount of waste heat during the air circulation process and has low heat recovery efficiency.

[0007] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0008] A method for drying and carbonizing wood in an echelon temperature-controlled manner comprises the following steps: step S10, pre-treatment of raw materials and a temperature control system, putting the wood into a plurality of drying chambers in batches, the plurality of drying chambers being connected by a first temperature-controlled pipe, an exchange pump being provided in the first temperature-controlled pipe for circulating air between the plurality of drying chambers, a heating device being connected to the plurality of drying chambers by a second temperature-controlled pipe, and setting temperature gradients A, B, and C; step S20, preheating start, performing a temperature gradient A heating treatment on the first drying chamber, and when the drying chamber enters the temperature gradient B heating treatment stage, starting the exchange pump between the drying chamber and the adjacent second drying chamber, The waste heat is guided to the second drying chamber for temperature gradient A heating treatment; step S30, drying transition, when the first drying chamber is subjected to the temperature gradient C heating treatment stage, it is ready for carbonization treatment, at this time, the first drying chamber guides the second drying chamber to perform temperature gradient B heating treatment, and starts the exchange pump between the second drying chamber and the third drying chamber, so that the second drying chamber guides the third drying chamber to perform temperature gradient A heating treatment; step S40, carbonization curing, carbonization treatment of the first drying chamber; step S50, deep curing and waste heat relay; step S60, cooling and wood output, output and replacement of processed wood, and access to the heat circulation loop.

[0009] Furthermore, in step S10, the temperature gradient A is the preheating drying and deep dehydration stage, with a temperature range of 50-110°C; the temperature gradient B is the pre-carbonization stage, with a temperature range of 110-140°C; and the temperature gradient C is the main carbonization stage, with a temperature range of 140-220°C.

[0010] Furthermore, it also includes a thermal compensation system, which includes: an auxiliary heater installed on the second temperature control pipe, which is linked to the temperature sensor of each drying chamber; when the waste heat introduced by the first temperature control pipe is lower than the target gradient temperature after temperature adjustment, the auxiliary heater automatically starts to supplement heat to maintain the temperature in the drying chamber stable within the set range of temperature gradients A, B, and C; a mixing temperature control device, installed on the exchange pump, for introducing and mixing ambient air.

[0011] Furthermore, it also includes a humidity control system, which includes: a humidity sensor, a steam regulating valve and a steam pipe installed in each drying chamber, and maintains the humidity of temperature gradient A ≥ 95%, the humidity of temperature gradient B ≥ 95%, and the humidity of temperature gradient C ≥ 95% by adjusting the steam input.

[0012] Furthermore, the step S20 includes the following steps: step S21, performing a temperature gradient A heating treatment on the first drying chamber, controlling the temperature and humidity, and raising the temperature in stages according to 0-24 hours 30℃→70℃, humidity 60%→99%; 24-48 hours 70℃→90℃, humidity ≥95%; 48-72 hours 90℃→110℃, humidity ≥95%, so as to balance the moisture content of the wood; step S22, when the temperature of the first drying chamber reaches 110℃ and the duration meets the temperature gradient A requirement, switching to the temperature gradient A. Gradient B heating treatment, controlling the temperature to 110°C → 140°C, and the humidity to ≥ 95%; step S23, starting the exchange pump between the first drying chamber and the second drying chamber, introducing the escaped hot air generated in the temperature gradient B stage of the first drying chamber into the mixing temperature control device, and lowering the temperature to 50-110°C by mixing with ambient air, and then passing it into the second drying chamber as the temperature gradient A heat source. If the temperature is insufficient, start the heating device to perform thermal compensation through the second temperature control pipe to maintain the temperature gradient A temperature and humidity parameters of the second drying chamber.

[0013] Furthermore, the step S30 includes the following steps: step S31, the first drying chamber enters the temperature gradient C heating treatment, and the end temperature of the temperature gradient B is increased to 140-220°C at a rate of ≤2°C / h in the range of 140-160°C and 3-5°C / h in the range of 160-220°C; step S32, the first drying chamber guides the second drying chamber to enter the temperature gradient B heating treatment, and part of the escaping heat air in its own temperature gradient C stage is mixed with the ambient air through the first temperature control pipe and cooled to 110-140°C, and then introduced into the second drying chamber to assist it in maintaining the temperature and humidity of the temperature gradient B; step S33, start the exchange pump between the second drying chamber and the third drying chamber, and the escaping heat air generated in the second drying chamber in the temperature gradient B stage is cooled to 50-110°C and then introduced into the third drying chamber, and the temperature gradient A heating treatment of the third drying chamber is started, and thermal compensation is performed by the heating equipment when necessary.

[0014] Furthermore, the step S40 includes the following steps: step S41, the first drying chamber is maintained at 140-220°C in the temperature gradient C stage, and the carbonization process is controlled according to the heating rate of ≤2°C / h in the 140-160°C range and 3-5°C / h in the 160-220°C range; step S42, during the carbonization process, the dissipated hot air is continuously collected through the first temperature control pipe, and after treatment, it is used to supplement the temperature and humidity of itself and other drying chambers, and the humidity of the temperature gradient C is maintained at ≥95% through the humidity control system.

[0015] Furthermore, the step S50 includes the following steps: step S51, when the first drying chamber completes the temperature gradient C carbonization treatment, the second drying chamber continues to enter the temperature gradient C heating treatment, and adopts the same temperature and heating rate control as step S41; step S52, after the temperature gradient C ends, the heat escaping air of the first drying chamber is adjusted to 110-140°C and then passed into the third drying chamber, assisting the third drying chamber to switch from temperature gradient B to temperature gradient C, reducing additional heating energy consumption; step S53, the heat escaping air generated by the second drying chamber in the temperature gradient C stage is used to supplement the temperature and humidity of the temperature gradient C of the third drying chamber after treatment, thereby realizing waste heat relay.

[0016] Furthermore, the step S60 includes the following steps: step S61, the first drying chamber starts to cool down gradually, from 220°C to 80°C at a rate of ≤5°C / h, and the humidity is maintained at ≥95%. After the circulating fan is turned off, it is naturally cooled to a temperature close to the outdoor temperature; step S62, the first drying chamber is opened, the carbonized wood is output, and a new batch of wood is loaded; step S63, at this time, the third drying chamber has completed the temperature gradient C treatment, and the escaping hot air is cooled to 50-110°C after temperature adjustment, and is passed into the first drying chamber, and the temperature gradient A heating treatment of the first drying chamber is started, and the heat circulation loop is connected.

[0017] The present invention provides an echelon temperature-controlled wood drying and carbonization method, which has the following beneficial effects:

[0018] By relaying waste heat from multiple drying chambers and using gradient temperature control, the heat utilization rate is improved, reducing energy consumption by more than 70% compared to traditional processes.

[0019] A steam environment with a full-stage humidity of ≥95% is used instead of inert gas. Combined with precise temperature rise rate control from ≤2°C / h to 3-5°C / h, the combustion risk is reduced to below 0.0001%, significantly improving safety.

[0020] The drying and carbonization are completed simultaneously, which shortens the processing cycle and reduces the use of chemical additives, thus greatly improving environmental protection.

[0021] Through echelon-type cycle processing, batch intervals are reduced and output efficiency is improved, while ensuring that the moisture content of wood is ≤6%, the bending strength is increased by more than 30%, and the dimensional stability and weather resistance are significantly optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic flow chart of a method for drying and carbonizing wood using echelon temperature control according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0025] In the description of this application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installation," "connection," and "connection" should be understood in a broad sense. For example, they can refer to welding, bolting, or riveting; fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0028] Example:

[0029] The present embodiment provides a tiered temperature-controlled wood drying and carbonization method, comprising the following steps: step S10, pre-treatment of raw materials and temperature control system, putting wood into multiple drying chambers in batches, multiple drying chambers are connected by a first temperature-controlled pipe, the first temperature-controlled pipe is provided with an exchange pump for circulating air between the multiple drying chambers, the heating equipment and the multiple drying chambers are connected by a second temperature-controlled pipe, and temperature gradients A, B, and C are set; step S20, preheating start, performing temperature gradient A heating treatment on the first drying chamber, and when the drying chamber enters the temperature gradient B heating treatment stage, starting the exchange between the drying chamber and the adjacent second drying chamber. Change the pump and guide the waste heat to the second drying chamber for temperature gradient A heating treatment; step S30, drying transition, when the first drying chamber has completed the temperature gradient C heating treatment stage, it is ready for carbonization treatment. At this time, the first drying chamber guides the second drying chamber to perform temperature gradient B heating treatment, and starts the exchange pump between the second drying chamber and the third drying chamber, so that the second drying chamber guides the third drying chamber to perform temperature gradient A heating treatment; step S40, carbonization curing, carbonize the first drying chamber; step S50, deep curing and waste heat relay; step S60, cooling and wood output, output and replacement of processed wood, and connect to the heat circulation loop.

[0030] In this example, mature rubberwood with a growth cycle of 8-40 years and a diameter of 15 cm or greater is used as raw material. Immediately after felling, the ends are coated with a polyurethane waterproof coating to prevent cracking, and the bark is retained until transportation to minimize moisture loss. Multiple drying chambers utilize all-stainless steel construction (304 or 316L). During pretreatment, the steam vents, temperature and humidity sensors (accuracy ±1°C / 3%RH), electromagnetic hot air furnaces (power ≥50kW), and circulating fans (air volume ≥5000 m³ / h) must be inspected to ensure sealing and equipment stability. Both the primary and secondary temperature-control pipes must be suitable for high-temperature and high-humidity environments, and the exchange pump must be corrosion-resistant.

[0031] Furthermore, in step S10, temperature gradient A is the preheating drying and deep dehydration stage, with a temperature range of 50-110°C; temperature gradient B is the pre-carbonization stage, with a temperature range of 110-140°C; temperature gradient C is the main carbonization stage, with a temperature range of 140-220°C.

[0032] In this embodiment, the temperature gradient division matches the characteristics of the wood: temperature gradient A corresponds to the process of initial dehydration of rubber wood from a high moisture content (60%-80%) to about 25%, and cracking is avoided by gradually increasing the temperature; temperature gradient B initially stabilizes the wood cell wall through pre-carbonization at 110-140°C, preparing for subsequent deep carbonization; temperature gradient C in the range of 140-220°C can achieve pyrolysis modification of wood cellulose and hemicellulose, forming a stable carbonized layer, among which 140-160°C mainly removes volatile organic compounds, and 160-220°C enhances the carbonization effect to improve weather resistance.

[0033] Furthermore, it also includes a thermal compensation system, which includes: an auxiliary heater installed on the second temperature control pipe, which is linked to the temperature sensor of each drying chamber; when the waste heat introduced by the first temperature control pipe is lower than the target gradient temperature after temperature adjustment, the auxiliary heater automatically starts to supplement heat to maintain the temperature in the drying chamber stable within the set range of temperature gradients A, B, and C; a mixing temperature control device, installed on the exchange pump, for introducing and mixing ambient air.

[0034] In this embodiment, the auxiliary heater utilizes a high-temperature-resistant electromagnetic coil, linked in real time to a temperature sensor within the drying chamber with an accuracy of ±1°C. When the residual heat, after mixing and temperature control, falls below the target value (for example, temperature gradient A requires a maintenance of 50-110°C), supplemental heating is immediately initiated. The mixing and temperature control device controls the amount of ambient air introduced via a proportional valve. For example, 120°C residual heat generated by temperature gradient B is mixed with ambient air, precisely cooling the temperature to 50-110°C to match the requirements of temperature gradient A. This prevents waste heat or excessive temperatures from causing wood cracking.

[0035] Furthermore, it also includes a humidity control system, which includes: humidity sensors, steam regulating valves and steam pipes installed in each drying chamber, which maintain the humidity of temperature gradient A ≥ 95%, the humidity of temperature gradient B ≥ 95%, and the humidity of temperature gradient C ≥ 95% by adjusting the steam input.

[0036] In this embodiment, the humidity sensor has an accuracy of ±3%RH. The steam pipe is connected to a high-pressure steam tank (pressure 1.0MPa), and the humidity is detected and adjusted every 30 minutes via a steam regulating valve. When the humidity falls below 95%, a rotating nozzle (air circulation coverage ≥ 90%) is immediately opened to spray 0.3-0.5MPa steam. The high humidity environment replaces the inert gas, reducing the oxygen concentration in the drying chamber to ≤8%. The oxygen concentration is calculated using the following formula:

[0037]

[0038] When RH=95%, the theoretical O2≈1.3%, and the actual O2 may be slightly higher due to steam flow, thus suppressing the risk of wood combustion from the root.

[0039] Furthermore, step S20 includes the following steps: step S21, performing temperature gradient A heating treatment on the first drying chamber, controlling the temperature and humidity, and raising the temperature in stages: 30°C → 70°C, humidity 60% → 99% for 0-24 hours; 70°C → 90°C, humidity ≥95% for 24-48 hours; 90°C → 110°C, humidity ≥95% for 48-72 hours, so as to balance the moisture content of the wood; step S22, when the temperature of the first drying chamber reaches 110°C and the duration meets the requirements of temperature gradient A, switching to temperature gradient B heating treatment, controlling the temperature to 110°C → 140°C, and humidity ≥95%; step S23, starting the exchange pump between the first drying chamber and the second drying chamber, introducing the escaped hot air generated in the temperature gradient B stage of the first drying chamber into the mixing temperature control device, reducing the temperature to 50-110°C by mixing with ambient air, and passing it into the second drying chamber as a heat source for temperature gradient A. If the temperature is insufficient, starting the heating device to perform heat compensation through the second temperature control pipe to maintain the temperature and humidity parameters of temperature gradient A in the second drying chamber.

[0040] In this embodiment, the temperature gradient A treatment in step S21 is coordinated with the wood squaring and stacking operations: within 36 hours, the wood is cut into standard 50mm×100mm×2000mm squares, planed to a flatness of ≤0.5mm, sprayed with water to maintain moisture (surface humidity ≥80%), and then stacked in a "well" pattern. Stainless steel spacers (≤50cm apart) are placed between layers to ensure uniform airflow. A steam sprayer is used to raise the temperature from 30°C to 70°C and the humidity from 60% to 99% over 0-24 hours to achieve initial moisture balance in the wood. Continuous high-saturation steam spraying is then applied for 24-72 hours to reduce the moisture content from 60% to approximately 25%. Humidity sensors are used every three days to prevent localized mold and mildew. In step S22, after a two-hour period at 110°C, the wood is transitioned to temperature gradient B, where continuous steam spraying maintains a humidity of ≥95%, at which point the wood begins initial thermal stabilization. The flow rate of the exchange pump in step S23 is set according to the volume of the drying chamber. For example, a 500m³ drying chamber needs to pass the waste hot air at 110-140°C into the second drying chamber at a rate of 1000m³ per hour after temperature adjustment. If the temperature drops to 45°C after mixing, the auxiliary heater is started to heat it to above 50°C.

[0041] Furthermore, step S30 includes the following steps: step S31, the first drying chamber enters the temperature gradient C heating treatment, and the terminal temperature of the temperature gradient B is increased to 140-220°C at a rate of ≤2°C / h in the range of 140-160°C and 3-5°C / h in the range of 160-220°C; step S32, the first drying chamber guides the second drying chamber to enter the temperature gradient B heating treatment, and part of the escaping heat air in its own temperature gradient C stage is mixed with the ambient air through the first temperature control pipe and cooled to 110-140°C, and then introduced into the second drying chamber to assist it in maintaining the temperature and humidity of the temperature gradient B; step S33, start the exchange pump between the second drying chamber and the third drying chamber, and the escaping heat air generated in the second drying chamber in the temperature gradient B stage is cooled to 50-110°C and then introduced into the third drying chamber, and the temperature gradient A heating treatment of the third drying chamber is started, and thermal compensation is performed by the heating equipment when necessary.

[0042] In this embodiment, the heating rate in step S31 is strictly controlled by an electromagnetic hot air furnace. The temperature in the 140-160°C range can be increased by no more than 2°C per hour (e.g., 140°C to 142°C requires 1 hour). The temperature in the 160-220°C range can be increased at a rate of 3-5°C / hour (e.g., 160°C to 165°C requires 1 hour). Simultaneously, an infrared thermal imager (with an accuracy of ±2°C) monitors the temperature difference within the wood pile to maintain a 10°C internal temperature difference to prevent local overheating. In step S32, the 160°C escaped air from the first drying chamber is mixed and temperature-controlled, then cooled to 120°C and passed into the second drying chamber to help maintain a temperature gradient B of 110-140°C. At this time, the steam regulating valve in the second drying chamber is simultaneously opened to ensure a humidity level of ≥95%. When the exchange pump in step S33 is running, it must filter out wood chips and impurities from the waste heat air through a filter to prevent pipe blockage. If the adjusted temperature is 48°C, the heating equipment is activated to increase the temperature to 50°C to meet the temperature gradient A required for the third drying chamber.

[0043] Furthermore, step S40 includes the following steps: step S41, the first drying chamber is maintained at 140-220°C in the temperature gradient C stage, and the carbonization process is controlled according to the heating rate of ≤2°C / h in the 140-160°C range and 3-5°C / h in the 160-220°C range; step S42, during the carbonization process, the dissipated hot air is continuously collected through the first temperature control pipe, and after treatment, it is used to supplement the temperature and humidity of itself and other drying chambers, and the humidity of the temperature gradient C is maintained at ≥95% through the humidity control system.

[0044] In this embodiment, the carbonization process in step S41 requires monitoring of the carbonization effect. For example, sampling is performed every 24 hours to test carbonization uniformity (color difference ΔE ≤ 3.0, using a spectrophotometer to measure ≥5 points / m³) and volatile matter content (≤ 12%, using a muffle furnace according to GB / T17664). In step S42, the escaping hot air is processed by a condensation recovery system. A condensate recovery rate of ≥ 85% can be recycled for steam generation. The uncondensed hot air is temperature-controlled and then transported to other drying chambers. Simultaneously, a humidity control system replenishes steam via a steam regulating valve to ensure a stable humidity of 95% ± 2% in the 140-220°C range, preventing cracking of the wood due to uneven drying.

[0045] Furthermore, step S50 includes the following steps: step S51, when the first drying chamber completes the temperature gradient C carbonization treatment, the second drying chamber enters the temperature gradient C heating treatment, and adopts the same temperature and heating rate control as step S41; step S52, after the temperature gradient C ends, the heat escaping air in the first drying chamber is adjusted to 110-140°C and then passed into the third drying chamber, assisting the third drying chamber to switch from temperature gradient B to temperature gradient C, reducing additional heating energy consumption; step S53, the heat escaping air generated in the second drying chamber in the temperature gradient C stage is used to supplement the temperature and humidity of the temperature gradient C of the third drying chamber after treatment, thereby realizing waste heat relay.

[0046] In this embodiment, before the second drying chamber enters temperature gradient C in step S51, the wood's bending strength is tested using a universal material testing machine (ASTM D143 standard). After ensuring a retention rate of ≥75%, the temperature is then raised at a rate of ≤2°C / h between 140°C and 160°C, and 3-5°C / h between 160°C and 220°C. In step S52, the 220°C waste heat from the first drying chamber is mixed and temperature-controlled, then cooled to 130°C and passed to the third drying chamber to support its transition from 140°C (the end point of temperature gradient B) to 160°C (temperature gradient C). This process reduces heating equipment energy consumption by 50%. The waste heat relay in step S53 is automated via a PLC control system. The 180°C hot air from the second drying chamber is processed and steadily replenishes the heat demand in the 160-220°C range of the third drying chamber, forming a closed-loop thermal cycle.

[0047] Furthermore, step S60 includes the following steps: step S61, the first drying chamber starts gradient cooling, gradually decreasing from 220°C to 80°C at a rate of ≤5°C / h, maintaining humidity ≥95%, and naturally cooling to a temperature close to the outdoor temperature after turning off the circulating fan; step S62, opening the first drying chamber, outputting the carbonized wood, and loading a new batch of wood; step S63, at this time, the third drying chamber has completed the temperature gradient C treatment, and its escaping heat air is temperature-adjusted to 50-110°C, and is passed into the first drying chamber, starting the temperature gradient A heating treatment of the first drying chamber, and connecting to the heat circulation loop.

[0048] In this embodiment, the cooling process in step S61 requires strict rate control, with the temperature decreasing no more than 5°C per hour from 220°C to 80°C (e.g., 220°C → 215°C → ... → 80°C). Steam injection is maintained during this period to maintain a humidity level ≥ 95% to prevent sudden shrinkage and cracking of the wood. After reaching 80°C, the circulating fan is turned off, and the kiln door is left half-open for forced ventilation, allowing natural cooling to approximately 25°C (close to the outdoor temperature). The wood discharged in step S62 is tested for moisture content (≤6% using a resistance moisture meter) and surface carbonization depth (≥3mm, analyzed by microscopic sectioning). If qualified, it is transferred to a cool warehouse (temperature 20-40°C, humidity 40-70%) for seven days of curing, with accelerated equilibration using a stress release machine. In step S63, the residual heat from the third drying chamber is temperature-controlled and then passed to the first drying chamber, which has been loaded with new wood, at 50-110°C, initiating a new round of temperature gradient A treatment, achieving continuous production and shortening batch intervals.

[0049] In summary, through tiered precise control of temperature and humidity and closed-loop utilization of waste heat, the wood drying and carbonization cycle was shortened from 45-60 days to 3-6 days; through zero chemical additives and high-humidity oxygen control technology, formaldehyde emission was achieved to ≤0.008mg / m³ and the combustion risk was reduced to 0.0001%; ​​through full-process automated control and thermal cycle design, energy consumption was reduced by more than 70%, while ensuring that the wood's bending strength was increased by 30% and the shrinkage rate was ≤2%, significantly optimizing environmental protection and product performance.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for drying and carbonizing wood using echelon temperature control, characterized in that: The following steps are involved: Step S10: Pre-processing the raw materials and the temperature control system. The wood is put into multiple drying chambers in batches. The multiple drying chambers are connected by a first temperature-controlled pipe. The first temperature-controlled pipe is provided with an exchange pump for circulating air between the multiple drying chambers. The heating device is connected to the multiple drying chambers by a second temperature-controlled pipe. Temperature gradients A, B, and C are set. Step S20: preheating start, performing temperature gradient A heating treatment on the first drying chamber. When the drying chamber enters the temperature gradient B heating treatment stage, starting the exchange pump between the drying chamber and the adjacent second drying chamber to guide the residual heat to the second drying chamber for temperature gradient A heating treatment. Step S30, drying transition: after the first drying chamber has completed the temperature gradient C heating treatment stage and is ready for carbonization treatment, the first drying chamber guides the second drying chamber to perform the temperature gradient B heating treatment, and the exchange pump between the second and third drying chambers is started, so that the second drying chamber guides the third drying chamber to perform the temperature gradient A heating treatment; Step S40: carbonization and curing, wherein the first drying chamber is subjected to carbonization treatment; Step S50, deep curing and residual heat relay; Step S60: Cooling and wood output, output and replacement of processed wood, and connecting to the heat circulation loop.

2. The echelon temperature-controlled wood drying and carbonization method according to claim 1, characterized in that: In step S10, the temperature gradient A is the preheating drying and deep dehydration stage, with a temperature range of 50-110°C; the temperature gradient B is the pre-carbonization stage, with a temperature range of 110-140°C; and the temperature gradient C is the main carbonization stage, with a temperature range of 140-220°C.

3. The echelon temperature-controlled wood drying and carbonization method according to claim 2, characterized in that: Also included is a thermal compensation system, the thermal compensation system comprising: An auxiliary heater installed on the second temperature control pipe is linked to the temperature sensor in each drying chamber; When the waste heat introduced into the first temperature control pipe is lower than the target gradient temperature after temperature adjustment, the auxiliary heater automatically starts to add heat to maintain the temperature in the drying chamber stable within the set range of temperature gradients A, B, and C; The mixing and temperature regulating device is installed on the exchange pump and is used for introducing and mixing ambient air.

4. The echelon temperature-controlled wood drying and carbonization method according to claim 3, characterized in that: Also included is a humidity control system, the humidity control system comprising: The humidity sensors, steam regulating valves and steam pipes installed in each drying room adjust the steam flow to maintain the humidity of temperature gradient A ≥ 95%, the humidity of temperature gradient B ≥ 95%, and the humidity of temperature gradient C ≥ 95%.

5. The echelon temperature-controlled wood drying and carbonization method according to claim 4, characterized in that: The step S20 includes the following steps: Step S21, heating the first drying chamber with a temperature gradient A, controlling the temperature and humidity, and increasing the temperature in stages: 30°C → 70°C, humidity 60% → 99% for 0-24 hours; 70°C → 90°C, humidity ≥ 95% for 24-48 hours; and 90°C → 110°C, humidity ≥ 95% for 48-72 hours, to balance the moisture content of the wood; Step S22: When the temperature of the first drying chamber reaches 110°C and the duration meets the requirements of temperature gradient A, the drying chamber enters temperature gradient B heating treatment, controlling the temperature from 110°C to 140°C and the humidity ≥ 95%; Step S23: Start the exchange pump between the first drying chamber and the second drying chamber, introduce the escaped hot air generated in the temperature gradient B stage of the first drying chamber into the mixing temperature control device, reduce the temperature to 50-110°C by mixing with ambient air, and pass it into the second drying chamber as a heat source for the temperature gradient A. If the temperature is insufficient, start the heating device to perform thermal compensation through the second temperature control pipe to maintain the temperature and humidity parameters of the temperature gradient A of the second drying chamber.

6. The echelon temperature-controlled wood drying and carbonization method according to claim 5, characterized in that: The step S30 includes the following steps: Step S31: The first drying chamber enters the temperature gradient C for heating treatment, and the end temperature of the temperature gradient B is increased to 140-220°C at a rate of ≤2°C / h in the 140-160°C range and 3-5°C / h in the 160-220°C range; Step S32: The first drying chamber guides the second drying chamber to enter the temperature gradient B heating process. Part of the heat air at the temperature gradient C stage is mixed with the ambient air through the first temperature control pipe and cooled to 110-140°C before being passed into the second drying chamber to help maintain the temperature and humidity at the temperature gradient B. Step S33: Start the exchange pump between the second drying chamber and the third drying chamber, adjust the temperature of the hot air generated in the second drying chamber at the temperature gradient B stage to 50-110° C. and then pass it into the third drying chamber, start the temperature gradient A heating treatment in the third drying chamber, and perform heat compensation through the heating equipment if necessary.

7. The echelon temperature-controlled wood drying and carbonization method according to claim 6, characterized in that: The step S40 includes the following steps: Step S41: The first drying chamber is maintained at a temperature gradient C of 140-220°C, and the carbonization process is controlled at a heating rate of ≤2°C / h in the 140-160°C range and 3-5°C / h in the 160-220°C range; Step S42: During the carbonization process, the first temperature control pipe continuously collects the dissipated hot air, and after treatment, it is used to replenish the temperature and humidity of the drying chamber itself and other drying chambers. At the same time, the humidity of the temperature gradient C is maintained at ≥95% through the humidity control system.

8. The echelon temperature-controlled wood drying and carbonization method according to claim 7, characterized in that: The step S50 includes the following steps: Step S51: After the first drying chamber completes the carbonization treatment at the temperature gradient C, the second drying chamber enters the heating treatment at the temperature gradient C, using the same temperature and heating rate control as step S41; Step S52: After the temperature gradient C ends in the first drying chamber, the hot air escaping from the first drying chamber is temperature-controlled to 110-140° C. and then passed into the third drying chamber, thereby assisting the third drying chamber in transitioning from the temperature gradient B to the temperature gradient C, thereby reducing additional heating energy consumption. Step S53: The heat air generated in the temperature gradient C stage of the second drying chamber is processed and used to supplement the temperature and humidity of the temperature gradient C of the third drying chamber to achieve waste heat relay.

9. The echelon temperature-controlled wood drying and carbonization method according to claim 8, characterized in that: The step S60 includes the following steps: Step S61: The first drying chamber begins to gradually cool down from 220°C to 80°C at a rate of ≤5°C / h, maintaining humidity at ≥95%, and then turns off the circulating fan and naturally cools down to near the outdoor temperature; Step S62: Open the first drying chamber, output the carbonized wood, and load a new batch of wood; Step S63: At this time, the third drying chamber has completed the temperature gradient C treatment, and its escaped hot air is temperature-controlled to 50°C-110°C and passed into the first drying chamber, starting the temperature gradient A heating treatment of the first drying chamber and connecting to the heat circulation loop.

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