External heating type oxygen limiting pyrolysis device

Abstract

The invention discloses an external heating type oxygen-limited pyrolysis device, and belongs to the technical field of biomass pyrolysis equipment. Aiming at the technical bottleneck of strong coupling of oxygen concentration regulation and heat supply in the traditional process, the device innovatively constructs an internal and external double-heat-source synergistic thermodynamic architecture, and is characterized in that: 1) an annular radiation type combustion hearth (11) is coaxially arranged outside a pyrolysis reactor (16), and external source radiant heat energy is provided by combusting pyrolysis gas; 2) the pyrolysis reactor (16) is integrated with an oxygen-limited combustion unit, and the oxygen concentration is controlled through an air regulating valve (13) to realize local combustion heat supply; and (3) a simplified fuel gas recycling mechanism is arranged, pyrolysis gas is directly guided into a combustor (6) through a gas conveying fan (5), and an energy closed loop is formed. The external heating unit and the internal oxygen-limited combustion unit are cooperatively controlled, the temperature fluctuation limitation of a single heat source is broken through, and the biochar yield and the pyrolysis gas quality are remarkably improved. The device solves the strong coupling contradiction of oxygen concentration-combustion intensity-pyrolysis efficiency in a traditional process, has the advantages of being compact in structure, high in heat efficiency and stable in operation, and is suitable for efficient thermochemical conversion of biomass and organic solid waste.

Description

Technical Field

[0001] The invention relates to the technical field of biomass pyrolysis, and in particular to an externally heated oxygen-limited pyrolysis device. Background Art

[0002] Biomass oxygen-limited pyrolysis technology achieves partial combustion heat supply by adjusting the oxygen supply. Its core contradiction lies in the dynamic balance between combustion heat release and pyrolysis heat absorption. Traditional processes rely on air flow regulation to control combustion intensity: when there is excessive oxygen supply, the oxidation reaction intensifies, the biomass carbon skeleton is over-decomposed, and the charcoal yield is significantly reduced; when there is insufficient oxygen supply, the heat released by combustion cannot meet the pyrolysis demand, resulting in pyrolysis stagnation and raw material residue. The root cause of this contradiction lies in the unidirectionality of the energy supply mechanism - the pyrolysis heat is completely dependent on internal combustion self-heating, and the combustion intensity is strongly coupled with the oxygen concentration.

[0003] Existing technologies focus on improving the gas supply method to optimize oxygen distribution, such as using stepped air distribution or multi-stage air distribution systems. However, such improvements are limited by the gas-solid mass transfer efficiency: the accumulation of biomass particles leads to uneven airflow distribution, large deviations in local oxygen concentration, and regional differences in combustion intensity. What is more serious is that changes in the porosity of the material during the dynamic feeding process further aggravate the inaccuracy of oxygen concentration control, resulting in pyrolysis temperature fluctuations above 50°C, significant differences in the fixed carbon content of charcoal products, and poor stability of pyrolysis gas components. The above defects show that it is difficult to break through the strong coupling limitations of oxygen concentration-combustion intensity-pyrolysis efficiency simply by optimizing the gas supply, and it is urgent to achieve a technological breakthrough through innovation in the energy supply mechanism. Summary of the invention

[0004] The present invention discloses an externally heated oxygen-limited pyrolysis device, which innovatively constructs a thermodynamic system with coordinated internal and external dual heat sources, and realizes efficient biomass conversion through structural design and energy closed-loop control mechanism. The core of the device is composed of four major functional systems: the material conveying system adopts the coordinated operation of the feed motor and the feed valve to realize the continuous sealed conveying of biomass raw materials; the pyrolysis reaction system adopts a vertical composite cavity structure, the inner cavity performs the main reaction of oxygen-limited pyrolysis, and the outer cavity is equipped with a combustion furnace to provide an auxiliary heat source; the energy circulation system abandons the traditional lengthy gas processing link, constructs a pyrolysis gas direct-connected combustion channel, and directly introduces the combustible gas into the external burner, and the combustion heat energy evenly penetrates into the outer wall of the pyrolysis reactor through the radiation heat transfer interface; the control system dynamically adjusts the gas supply through the frequency conversion of the gas transmission fan, and controls the oxygen intake by adjusting the opening of the air intake valve, so as to realize the precise coordinated operation of the pyrolysis temperature field and oxygen concentration.

[0005] Technical principle of the present invention: This patent reconstructs the pyrolysis energy supply structure and establishes a dynamic synergistic mechanism of endogenous combustion and exogenous heat supply, fundamentally resolving the strong coupling contradiction between oxygen concentration and pyrolysis efficiency in traditional oxygen-limited pyrolysis. Its technical principle is based on three core innovations: 1. Heat-mass transfer decoupling mechanism A gas circulation heating system is built outside the pyrolysis reactor to introduce the combustible gas generated by pyrolysis into the combustion device, and the heat released by combustion is efficiently introduced into the outer wall of the reactor. The external heating system complements the internal oxygen-limited combustion, significantly reducing the pyrolysis process's dependence on internal oxygen concentration, and transforming oxygen concentration control from passively adapting to combustion needs to actively optimizing product distribution.

[0006] 2. Energy closed-loop control system Internal combustion provides the basic heat source to maintain the start-up of pyrolysis, and external gas heating dynamically compensates for the heat demand of the main reaction zone. By adjusting the gas supply and the opening of the air intake valve, a feedback regulation loop with two-way heat source coupling is formed. This design breaks through the temperature fluctuation limit of a single heat source and realizes the steady-state thermal field distribution of the pyrolysis reactor.

[0007] 3. Directed regulation of reaction pathways By reducing the internal oxygen concentration to inhibit the oxidative decomposition path, external heat input accelerates the dehydrogenation polycondensation reaction and promotes the directional development of the microporous structure of biochar. The gas-solid contact mode is simultaneously optimized to quickly export the volatile matter from the reaction zone, reduce secondary cracking side reactions, and effectively inhibit tar formation while increasing the biochar yield.

[0008] This patent innovates the energy supply model, transforming the mutually constrained combustion oxygen supply and pyrolysis heat demand in the traditional process into a synergistic and effective relationship, providing a new methodology for biomass pyrolysis technology.

[0009] The technical solution of the present invention: The invention relates to an externally heated oxygen-limited pyrolysis device, comprising a material conveying system, a pyrolysis reaction system, an energy circulation system and a control system.

[0010] The material conveying system is composed of a hopper (1), a feed motor (17) and a feed valve (18). The hopper (1) is connected to the upper end of the pyrolysis reactor (16) to achieve sealed conveyance of the biomass raw material (2).

[0011] The pyrolysis reaction system comprises a vertical composite cavity structure, wherein the inner cavity is a pyrolysis reactor (16), and the outer cavity is provided with an annular radiation combustion furnace (11), and the outer layer of the furnace (11) is provided with a heat insulation layer (10). The pyrolysis reactor (16) is provided with a charcoal outlet (7) and a charcoal outlet valve (8) at the bottom, and a pyrolysis gas outlet (4) is provided at the top.

[0012] Energy circulation system: The pyrolysis gas outlet (4) is connected to a gas delivery fan (5) and a burner (6) in sequence, wherein the burner (6) is located at the bottom of the furnace (11), and a furnace tail gas outlet (3) is provided at the top of the furnace (11). The gas delivery fan (5) delivers the combustible gas discharged from the pyrolysis gas outlet (4) to the burner (6), and the heat generated by the combustion is conducted to the outer wall of the pyrolysis reactor (16) through the annular radiation furnace (11).

[0013] The control system comprises an air delivery fan (5), a charcoal discharge motor (9), a charcoal discharge valve (8), an air regulating valve (13), an air inlet (12), an igniter (14), a feed motor (17), and a feed valve (18). The pyrolysis reactor (16) inputs restricted air through the air inlet (12) and the igniter (14), controls the opening of the air regulating valve (13) to adjust the air intake, and controls the internal oxygen concentration at 3-5 vol%. The fuel gas supply is controlled by adjusting the speed of the air delivery fan (5), and the opening of the air regulating valve (13) is linked to stabilize the pyrolysis temperature at a range of 550-650°C. The feed valve (18) is driven by the feed motor (17) and performs intermittent feeding according to the pyrolysis reaction time. The charcoal discharge valve (8) is driven by the charcoal discharge motor (9) and discharges the biochar (15) intermittently according to the pyrolysis reaction time.

[0014] The beneficial effects of the present invention are: The present invention breaks through the strong coupling limitation of oxygen concentration and heat supply in traditional processes by dynamically matching internal and external heat sources: internal oxygen-limited combustion maintains basic pyrolysis conditions, and external gas heating provides the energy requirements of the main reaction zone. The two form an energy closed loop through feedback control. This design frees the pyrolysis process from dependence on high oxygen concentrations, significantly inhibits excessive oxidation of biomass, and shortens the pyrolysis time and reduces the occurrence of side reactions through external heat compensation. Ultimately, the comprehensive benefits of increased biochar yield, optimized pore structure, and stable pyrolysis gas quality are achieved, providing efficient and reliable technical equipment for the industrial application of biomass pyrolysis technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an externally heated oxygen-limited pyrolysis device.

[0016] In the figure: 1. Hopper 2. Raw materials 3. Furnace exhaust gas outlet 4. Pyrolysis gas outlet 5. Gas delivery fan 6. Burner 7. Charcoal outlet 8. Charcoal outlet valve 9. Charcoal outlet motor 10. Insulation layer 11. Furnace 12. Air inlet 13. Air regulating valve 14. Ignitor 15. Biochar 16. Pyrolysis reactor 17. Feed motor 18. Feed valve. DETAILED DESCRIPTION

[0017] The present invention is described in further detail below in conjunction with the accompanying drawings. Example

[0018] The present invention provides an externally heated oxygen-limited pyrolysis device. The implementation of the device mainly includes the following steps: 1. Feeding and startup (1) loading a biomass raw material (2) into a hopper (1), starting a charcoal discharge motor (9) to drive a charcoal discharge valve (8) to close, starting a feed motor (17) to drive a feed valve (18) to open, and conveying the raw material (2) into a pyrolysis reactor (16) through a sealed channel; (2) introducing limited air into the pyrolysis reactor (16) through the air inlet (12), starting the igniter (14) so ​​that the incoming air is high-temperature hot gas to ignite the raw materials, adjusting the opening of the air regulating valve (13) to control the initial oxygen concentration, and closing the igniter (14) after the internal oxygen-limited pyrolysis begins; (3) The burner (6) is started, and the combustible gas is burned in the furnace (11). Heat is radiated through the furnace (11) to the outer wall of the pyrolysis reactor (16), and the heat insulation layer (10) reduces heat loss.

[0019] 2. Pyrolysis reaction (1) The raw material (2) in the pyrolysis reactor (16) is thermally decomposed under oxygen-limited conditions, and the generated combustible gas is discharged from the pyrolysis gas outlet (4); (2) The gas delivery fan (5) delivers the pyrolysis gas to the burner (6) for continuous combustion, thereby maintaining heat supply to the furnace (11); (3) The combustion exhaust gas in the furnace (11) is discharged from the system through the furnace exhaust gas outlet (3).

[0020] 3. Product discharge (1) The generated biochar (15) is accumulated at the bottom of the pyrolysis reactor (16) and discharged through the charcoal outlet (7); (2) The charcoal discharge motor (9) drives the charcoal discharge valve (8) to open according to a set cycle, thereby controlling the discharge of the biochar (15); (3) The feed motor (17) and the charcoal discharge motor (9) operate in conjunction with each other to maintain a dynamic balance of materials in the pyrolysis reactor (16).

[0021] 4. System Control (1) controlling the oxygen concentration in the pyrolysis reactor (16) by adjusting the opening of the air regulating valve (13); (2) adjusting the speed of the gas delivery fan (5) based on the pyrolysis gas output to balance the heating intensity of the burner (6); (3) The feed valve (18) and the charcoal discharge valve (8) work in coordination to ensure that the timing of the supply of the raw material (2) and the discharge of the biochar (15) is matched.

[0022] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An externally heated oxygen-limited pyrolysis device, mainly composed of a hopper, a furnace tail gas outlet, a pyrolysis gas outlet, a gas delivery fan, a burner, a charcoal outlet, a charcoal outlet valve, a charcoal outlet motor, an insulation layer, a furnace, an air inlet, an air regulating valve, an igniter, a pyrolysis reactor, a feed motor and a feed valve.

2. The externally heated oxygen-limited pyrolysis device according to claim 1, characterized in that: An external heating unit is added to the outside of the pyrolysis reactor (16), and an annular radiation combustion furnace (11) is coaxially arranged outside the pyrolysis reactor (16). The furnace (11) generates external heat by burning pyrolysis gas through a burner (6), and directly radiates and conducts to the outer wall of the pyrolysis reactor (16).

3. The externally heated oxygen-limited pyrolysis device according to claim 1, characterized in that: The device comprises an external heating unit and an oxygen-limited pyrolysis unit; the external heating unit is composed of a furnace (11), a burner (6) and an air delivery fan (5), and is used to provide external radiant heat energy through the combustion of pyrolysis gas; the oxygen-limited pyrolysis unit comprises an air inlet (12), an air regulating valve (13), an igniter (14) and a pyrolysis reactor (16), and controls the internal oxygen concentration by adjusting the air supply amount, thereby achieving internal oxygen-limited combustion of biomass.

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