Airflow control method and control system for biomass high-temperature carbonization

Abstract

The invention belongs to the technical field of biomass carbonization, and particularly relates to a biomass high-temperature carbonization airflow control method which comprises the following steps: loading and sealing: loading a biomass raw material into a kiln body and sealing; drying treatment is conducted, specifically, a combustion heat supply device is started, heat mass airflow is conveyed to the kiln body, other adjusting valves are closed, an adjusting valve corresponding to an induced draft fan is opened, and water vapor and carbon dioxide are discharged; carbonization treatment: after controlling the negative pressure oxygen-free environment of-10 kPa to-1 kPa in the kiln body, closing a regulating valve corresponding to the hot gas directly passing through the kiln body; in the carbonization treatment process, after pyrolysis gas is generated by biomass, an adjusting valve of a pyrolysis gas conveying pipe is opened, the pyrolysis gas is introduced into a combustion heat supply device, and the negative pressure of a combustion chamber is maintained to be lower than the air pressure in the kiln. The invention further provides a control system. By means of the method and system, efficient and stable biomass carbonization can be achieved, and pyrolysis gas can be fully utilized.

Description

Technical Field

[0001] This invention belongs to the field of biomass carbonization technology, specifically relating to an airflow control method and control system for high-temperature biomass carbonization. Background Technology

[0002] Traditional biomass burning methods, such as earthen kilns and pit kilns, typically involve igniting biomass (such as wood, straw, and rice husks) inside the kiln. Once the fire is lit, oxygen supply is restricted by covering it with soil or sand, or by closing the ventilation openings. This causes the biomass to undergo thermal decomposition at high temperatures, producing biochar and volatile decomposition gases. This traditional method leads to problems such as long product production cycles, uneven biochar quality, and the inability to utilize decomposition gases as a resource.

[0003] While some modern methods have significantly improved upon traditional biomass charring processes, they still suffer from issues such as high equipment investment, stringent requirements for inert gas addition during production, and limitations on pyrolysis in certain processes. More importantly, neither traditional nor modern biomass charring methods have addressed the control of thermal mass flow and pyrolysis gas reflux combustion. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a gas flow control method and control system for high-temperature biomass carbonization that can achieve efficient and stable biomass carbonization and make full use of pyrolysis gas.

[0005] The technical solution of this invention is: a method for controlling the airflow during high-temperature carbonization of biomass, comprising: A method for controlling airflow in high-temperature biomass carbonization, used in a negative-pressure high-temperature biomass carbonization device, is characterized in that the negative-pressure biomass high-temperature carbonization device includes a kiln body, a combustion heating device, an induced draft fan, a heat and mass gas flow transmission pipeline, and an electrical control center. The combustion heating device is connected to the bottom of the kiln body via the heat and mass gas flow transmission pipeline. A pyrolysis gas delivery pipe is provided at the top of the kiln body, and the pyrolysis gas delivery pipe is connected to the top of the combustion heating device. The branch pipes of the heat and mass gas flow transmission pipeline and the pyrolysis gas delivery pipe are equipped with regulating valves. The induced draft fan is connected to one of the branch pipes and its opening and closing are controlled by the corresponding regulating valve. Multiple temperature sensors are installed inside the kiln body, and a gas flow sensor is also installed inside the heat and mass gas flow transmission pipeline. Pressure sensors are installed inside the kiln body and the combustion heating device. The electrical control center is electrically connected to each component and is used to regulate the working status of the kiln body, the combustion heating device, and the heat and mass gas flow transmission pipeline. The airflow control method for high-temperature carbonization of biomass includes: Loading and sealing: The biomass raw materials are loaded into the kiln and then sealed. Drying process: Start the combustion heating device to deliver hot mass airflow to the kiln body, close other regulating valves, open the regulating valve corresponding to the induced draft fan, and discharge water vapor and carbon dioxide; Carbonization treatment: After controlling the kiln body to a negative pressure oxygen-free environment of -10 kPa to -1 kPa, close the regulating valve corresponding to the direct flow of hot gas into the kiln body; Pyrolysis gas utilization and treatment: During the carbonization process, when pyrolysis gas is generated from biomass, the regulating valve of the pyrolysis gas delivery pipe is opened to introduce the pyrolysis gas into the combustion heating device, maintaining the negative pressure in the combustion chamber lower than the gas pressure inside the kiln.

[0006] In one embodiment, during the drying process, the temperature of the hot mass gas flow inside the kiln is 80℃-300℃, the gas flow velocity in the hot mass gas flow transmission pipe is 10-20 m / s, and the gas pressure inside the kiln is maintained between -5 kPa and -1 kPa. The drying process results in the biomass moisture content inside the kiln being less than 5%.

[0007] In one embodiment, the temperature of the hot mass gas flow during the carbonization process is 300℃-900℃, the gas flow velocity in the hot mass gas flow transmission pipe is 20-40 m / s, and the gas pressure inside the kiln is maintained between -10 kPa and -1 kPa.

[0008] In one embodiment, when the temperature at the top of the kiln is greater than 200°C, the hot mass gas flow is heated to above 900°C, and the gas flow velocity in the hot mass gas flow transmission pipe is increased to 30 m / s to 40 m / s.

[0009] In one embodiment, when the pyrolysis gas is utilized, the gas pressure of the combustion heating device is maintained at -30 kPa to -10 kPa, and is at least 2 kPa lower than the gas pressure inside the kiln.

[0010] In one embodiment, after opening the regulating valve of the pyrolysis gas delivery pipe, the method further includes: gradually reducing the gas supply from the external gas source of the combustion heating device until the gas supply from the external gas source is shut off.

[0011] In one embodiment, when the amount of pyrolysis gas supplied to the combustion heating device is insufficient, the system switches back to an external gas source for combustion.

[0012] In one embodiment, after the carbonization process is completed, the combustion heating device is turned off, and the kiln is kept under a slight negative pressure and in an oxygen-free state, allowing it to cool down naturally.

[0013] In one embodiment, the hot mass gas flow transmission pipe is a square pipe with a cross-sectional area of ​​>100mm×100mm or a circular pipe with a diameter of >100mm.

[0014] Based on the same inventive concept, a control system for implementing the above method is also provided, comprising: Temperature sensors are placed at the top of the kiln, the hot mass inlet, the outlet, and the exhaust port. A gas flow sensor is installed in a hot mass gas transmission pipeline; Pressure sensors are installed in the kiln body and combustion chamber; The electrical control center is used to receive signals from various sensors and control the operation of regulating valves, burners, and induced draft fans.

[0015] The beneficial effects of this invention are as follows: The above-mentioned airflow control method and control system for high-temperature biomass carbonization, based on the heat and mass exchange, biomass conversion, and pyrolysis gas generation patterns in different stages of biomass carbonization production, effectively controls and utilizes the heat and mass required for staged biomass carbonization production. It fully utilizes the natural flow of pyrolysis gas from the high-temperature biomass treatment kiln back to the combustion chamber. By precisely controlling and maintaining a negative pressure oxygen-free environment of -10 kPa to -1 kPa within the kiln, oxygen is effectively isolated, preventing open flame combustion of biomass and ensuring that the pyrolysis process takes place under a controllable inert atmosphere. This effectively prevents the risk of leakage of pyrolysis combustible gas and enhances operational safety. This not only avoids raw material burn-off and improves char yield but also facilitates the formation of high-quality biochar with uniform structure, high fixed carbon content, and few impurities. The negative pressure environment also accelerates the release and discharge of volatile components, shortens the carbonization cycle, and improves overall processing efficiency. The pyrolysis gas generated during carbonization is introduced into the combustion heating device in real time for combustion, continuously providing heat to the system, forming an internal energy cycle of "gas-for-heat," significantly reducing dependence on external fuels and lowering operating costs. Meanwhile, the timely consumption of pyrolysis gas avoids its accumulation in the kiln, maintains process stability, and reduces the environmental risk of direct emissions of combustible waste gas. Relying on multiple temperature sensors within the kiln, gas flow sensors in the pipelines, and pressure sensors within the kiln and combustion device, the electrical control center can collect key parameters of the entire process in real time. Based on this data, the system can achieve precise control of the flow rate of the thermal mass gas, the pressure inside the kiln, and the temperature curve through the linkage control of regulating valves and induced draft fans. This closed-loop intelligent control overcomes the shortcomings of traditional carbonization processes, which rely on experience and experience, resulting in large fluctuations in operating conditions. This ensures that the carbonization process maintains high consistency and reproducibility across different batches of raw materials. The carbonization process is clearly divided into three stages: drying, carbonization, and pyrolysis gas utilization. Targeted airflow control is implemented for the gas composition and objectives of each stage. The segmented airflow management ensures clear objectives for each stage, efficient gas pathways, and avoids mutual interference between gases produced at different stages, improving the targeting of thermal energy utilization and the overall cleanliness of the process. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the airflow control method for high-temperature carbonization of biomass in one embodiment. Figure 2 This is a schematic diagram of the airflow path during high-temperature carbonization of biomass in one embodiment. Detailed Implementation

[0018] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0019] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0020] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0021] Please see Figure 1-2 This invention provides an embodiment of a gas flow control method for high-temperature biomass carbonization, used in a negative-pressure high-temperature biomass carbonization device. The negative-pressure biomass high-temperature carbonization device includes a kiln body, a combustion heating device, an induced draft fan, a hot and mass gas flow transmission pipeline, and an electrical control center. The combustion heating device is connected to the bottom of the kiln body via the hot and mass gas flow transmission pipeline. A pyrolysis gas delivery pipe is located at the top of the kiln body and is connected to the top of the combustion heating device. Regulating valves are installed on branch pipes of the hot and mass gas flow transmission pipeline and the pyrolysis gas delivery pipe. The induced draft fan is connected to one of the branch pipes and its opening and closing are controlled by the corresponding regulating valve. Multiple temperature sensors are installed inside the kiln body, and a gas flow sensor is also installed inside the hot and mass gas flow transmission pipeline. Pressure sensors are installed inside the kiln body and the combustion heating device. The electrical control center is electrically connected to each component and is used to regulate the working status of the kiln body, the combustion heating device, and the hot and mass gas flow transmission pipeline. Preferably, the hot and mass gas flow transmission pipeline is a square pipe with a cross-sectional area > 100mm × 100mm or a circular pipe with a diameter > 100mm.

[0022] Specifically, the airflow control method for the above-mentioned high-temperature carbonization of biomass includes: S10. Loading and sealing: Load the biomass raw materials into the kiln and seal it.

[0023] S20. Drying treatment: Start the combustion heating device to deliver hot mass airflow to the kiln body, close other regulating valves, open the regulating valve corresponding to the induced draft fan, and discharge water vapor and carbon dioxide.

[0024] Specifically, in one embodiment, see [link to embodiment]. Figure 2 Open regulator 3 and close other regulating valves. During the drying process, the temperature of the hot mass airflow in the kiln is 80℃-300℃, the airflow velocity of the hot mass airflow in the hot mass airflow transmission pipe is 10-20 m / s, and the air pressure in the kiln is maintained between -5 kPa and -1 kPa. The drying process makes the biomass moisture content in the kiln less than 5%.

[0025] S30, Carbonization treatment: After controlling the kiln body to a negative pressure oxygen-free environment of -10 kPa to -1 kPa, close the regulating valve corresponding to the direct flow of hot gas into the kiln body.

[0026] Specifically, regulating valves 1, 3, and 4 are closed, and the biomass undergoes carbonization within the kiln through a closed heat exchange system. The kiln maintains a negative pressure oxygen-free environment of -10 kPa to -1 kPa, which effectively isolates oxygen, prevents open flame combustion of biomass, ensures that the pyrolysis reaction takes place in an oxygen-free environment, and improves carbon yield and carbon fixation rate.

[0027] Specifically, during the carbonization process, the temperature of the hot mass gas flow is 300℃-900℃, the gas flow velocity in the hot mass gas flow transmission pipe is 20-40 m / s, and the gas pressure inside the kiln is maintained between -10 kPa and -1 kPa.

[0028] Furthermore, when the temperature at the top of the kiln exceeds 200°C, the hot mass gas flow is heated to over 900°C, and the gas flow velocity in the hot mass gas flow transmission pipe is increased to 30 m / s to 40 m / s.

[0029] The carbonization process is controlled in stages. When the temperature is higher, the airflow velocity is increased to maintain a stable temperature inside the kiln, ensuring a uniform temperature field distribution inside the kiln and consistent heating of the biomass. The resulting biochar has stable physicochemical properties, high fixed carbon content, and low ash content.

[0030] S40. Utilization and treatment of pyrolysis gas: During the carbonization process, when pyrolysis gas is generated from biomass, the regulating valve of the pyrolysis gas delivery pipe is opened to introduce the pyrolysis gas into the combustion heating device, maintaining the negative pressure in the combustion chamber lower than the gas pressure inside the kiln.

[0031] Specifically, by opening the regulating valve 4 on the cracked gas delivery pipe 102, the cracked gas can be directly reused as auxiliary fuel, significantly reducing external energy consumption. During the stable phase, an energy self-sufficiency rate of over 50% can be achieved.

[0032] Furthermore, after opening the regulating valve of the pyrolysis gas delivery pipe, the process also includes: gradually reducing the gas supply from the external gas source to the combustion heating device until the gas supply from the external gas source is shut off. Furthermore, when the amount of pyrolysis gas supplied to the combustion heating device is insufficient, the system switches back to supplying combustion gas from the external gas source.

[0033] During the utilization and treatment of the pyrolysis gas, the gas pressure of the combustion heating device is maintained between -30 kPa and -10 kPa, and at least 2 kPa lower than the kiln pressure. By maintaining the combustion chamber pressure lower than the kiln pressure, a stable airflow is formed, ensuring that the pyrolysis gas is smoothly introduced into the combustion device, while preventing backflow or oxygen infiltration. The negative pressure can be maintained by using an induced draft fan or a vacuum pump.

[0034] S50. After carbonization is completed, the combustion heating device is turned off, and the kiln is kept under a slight negative pressure and in an oxygen-free state for natural cooling.

[0035] Based on the same inventive concept, the present invention also provides a control system for implementing the above-mentioned airflow control method for high-temperature carbonization of biomass, comprising: a temperature sensor arranged at the top of the kiln, the heat inlet, the outlet and the exhaust port; a gas flow sensor arranged in the heat flow transmission pipeline; a pressure sensor arranged in the kiln and the combustion chamber; and an electrical control center for receiving signals from each sensor and controlling the operation of the regulating valve, the burner and the induced draft fan.

[0036] The aforementioned biomass high-temperature carbonization airflow control method and system, through negative pressure anaerobic environment control, recovery and utilization of pyrolysis gas generated during biomass carbonization, and segmented control of heat, mass, airflow and temperature, not only significantly improves biochar yield and quality, achieving energy closed-loop utilization and emission reduction goals, but also enhances process adaptability and operational safety through intelligent control. It is suitable for large-scale, continuous biomass resource utilization scenarios and has significant industrial application value and market promotion prospects.

[0037] The above are merely preferred embodiments of the present invention. It should be noted that the present invention is not limited to the above embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling airflow in high-temperature biomass carbonization, used in a negative pressure high-temperature biomass carbonization device, characterized in that, The negative pressure biomass high-temperature carbonization device includes a kiln body, a combustion and heating device, an induced draft fan, a heat and mass gas transmission pipeline, and an electrical control center. The combustion and heating device is connected to the bottom of the kiln body via the heat and mass gas transmission pipeline. A pyrolysis gas delivery pipe is located at the top of the kiln body and is connected to the top of the combustion and heating device. Regulating valves are installed in the branch pipes of the heat and mass gas transmission pipeline and the pyrolysis gas delivery pipe. The induced draft fan is connected to one of the branch pipes and its opening and closing are controlled by the corresponding regulating valve. Multiple temperature sensors are installed inside the kiln body, and a gas flow sensor is installed in the heat and mass gas transmission pipeline. Pressure sensors are installed in the kiln body and the combustion and heating device. The electrical control center is electrically connected to all components and is used to regulate the operating status of the kiln body, the combustion and heating device, and the heat and mass gas transmission pipeline. The airflow control method for high-temperature carbonization of biomass includes: Loading and sealing: The biomass raw materials are loaded into the kiln and then sealed. Drying process: Start the combustion heating device to deliver hot mass airflow to the kiln body, close other regulating valves, open the regulating valve corresponding to the induced draft fan, and discharge water vapor and carbon dioxide; Carbonization treatment: After controlling the kiln body to a negative pressure oxygen-free environment of -10 kPa to -1 kPa, close the regulating valve corresponding to the direct flow of hot gas into the kiln body; Pyrolysis gas utilization and treatment: During the carbonization process, when pyrolysis gas is generated from biomass, the regulating valve of the pyrolysis gas delivery pipe is opened to introduce the pyrolysis gas into the combustion heating device, maintaining the negative pressure in the combustion chamber lower than the gas pressure inside the kiln.

2. The method according to claim 1, characterized in that, During the drying process, the temperature of the hot mass airflow inside the kiln is 80℃-300℃, the airflow velocity in the hot mass airflow transmission pipe is 10-20 m / s, and the air pressure inside the kiln is maintained between -5kPa and -1 kPa. The drying process results in the biomass moisture content inside the kiln being less than 5%.

3. The airflow control method according to claim 1, characterized in that, During the carbonization process, the temperature of the hot mass gas flow is 300℃-900℃, the gas flow velocity in the hot mass gas flow transmission pipe is 20-40 m / s, and the gas pressure inside the kiln is maintained between -10 kPa and -1 kPa.

4. The airflow control method according to claim 3, characterized in that, When the temperature at the top of the kiln exceeds 200℃, the hot mass gas flow is heated to over 900℃, and the gas flow velocity in the hot mass gas flow transmission pipe is increased to 30m / s~40m / s.

5. The airflow control method according to claim 1, characterized in that, When the pyrolysis gas is utilized, the gas pressure of the combustion heating device is maintained at -30 kPa to -10 kPa, and is at least 2 kPa lower than the gas pressure inside the kiln.

6. The airflow control method according to claim 3, characterized in that, After opening the regulating valve of the pyrolysis gas delivery pipe, the process also includes: gradually reducing the gas supply from the external gas source of the combustion heating device until the gas supply from the external gas source is shut off.

7. The airflow control method according to claim 6, characterized in that, When the amount of pyrolysis gas supplied to the combustion heating device is insufficient, switch back to external gas source for combustion.

8. The airflow control method according to claim 1, characterized in that, After carbonization is completed, the combustion heating device is turned off, and the kiln is kept under a slight negative pressure and in an oxygen-free state for natural cooling.

9. The airflow control method according to claim 1, characterized in that, The hot mass airflow transmission pipe is a square pipe with a cross-sectional area of ​​>100mm×100mm or a circular pipe with a diameter of >100mm.

10. A control system for implementing the method according to any one of claims 1-9, characterized in that, include: Temperature sensors are located at the top of the kiln, the hot mass inlet, the outlet, and the exhaust port. A gas flow sensor is installed in a hot mass gas transmission pipeline; Pressure sensors are installed in the kiln body and combustion chamber; The electrical control center is used to receive signals from various sensors and control the operation of regulating valves, burners, and induced draft fans.

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