Method and device for co-producing high-value liquid and solid products through self-electric heating type biomass tempering pyrolysis

Abstract

The invention provides a method and a device for co-producing high-value liquid and solid products through self-supply electric heating type biomass tempering pyrolysis, and belongs to the technical field of biomass treatment. The device provided by the invention mainly comprises a feeding module, a pyrolysis module, a condensation module and a self-powered heating module. On the basis of in-situ conditioning and pyrolysis integration, a trace amount of potassium metal salt is added to regulate and control a pyrolysis path in situ, a self-powered electrothermal molten salt precise temperature control technology is utilized, the conditioning and pyrolysis process is uniform, stable and controllable, and synergistic upgrading of oil-carbon products can be realized. After the reaction, a potassium salt catalyst does not need to be separated and can be directly used as high-value returning-to-field biochar or a subsequent activation raw material, and the quality of the biochar is further improved. The device is simple in structure and accurate in temperature control, the prepared oil-carbon product is high in quality, the catalyst does not need to be separated, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass processing, relates to biomass pyrolysis high-value processing, and specifically relates to a method and device for self-powered heating and cooling biomass conditioning pyrolysis co-production of high-value liquid and solid products. Background Art

[0002] Biomass pyrolysis is a thermal conversion technology that converts biomass macromolecules into three-phase products: pyrolysis oil, pyrolysis gas, and pyrolysis char (PCH) through thermochemical decomposition under anaerobic or anoxic conditions. It features a simple process, low operating costs, and a wide range of applications, making it one of the most promising technologies for high-value biomass utilization. However, the three-phase products obtained from direct pyrolysis are often of low quality, necessitating subsequent design of separate quality improvement routes for the solid and liquid products (bio-oil and biochar), a complex and challenging process. Studies have shown that the introduction of specific catalysts into the catalytic pyrolysis process can significantly improve product quality and regulate product distribution. However, technical bottlenecks remain, such as difficulty in separating the catalyst and achieving precise temperature control.

[0003] Among these, the influence of pyrolysis temperature is particularly significant, being one of the key factors influencing the pyrolysis path and product distribution. This is especially true for catalytic pyrolysis, where temperature control is crucial. Precise temperature control at each stage has a decisive influence on the properties of the final product. Therefore, precise control of pyrolysis temperature to achieve precise regulation of pyrolysis product quality and yield distribution, while ensuring product stability and consistency, is crucial for subsequent quality improvement, value-added production, and industrial application.

[0004] Traditional heating methods, such as flue gas heating, utilize hot flue gas generated by fuel combustion to transfer heat through interlayer or direct heat conduction and convection. While these methods offer advantages such as mature technology and low heating costs, they suffer from poor temperature uniformity of the hot flue gas at the front end, high thermal inertia, and slow response speed of the heating system, making it difficult to achieve rapid and precise temperature regulation. While emerging microwave heating technology offers advantages such as fast heating speed and high uniformity, it still suffers from drawbacks such as high sensitivity to raw material properties, difficulty in regulating temperature uniformity, and low temperature measurement accuracy. This is particularly true for pyrolysis processes involving thermochemical reactions. As the degree of carbonization increases, the microwave absorption of pyrolysis intermediates changes constantly, further exacerbating the difficulty of precise temperature control. This has failed to effectively address the pyrolysis temperature control dilemma, resulting in pyrolysis products often being primarily utilized as low-value energy sources such as coke and gas, making it difficult to cover the high electricity costs.

[0005] Prior art CN116855267A discloses a sustainable self-powered biomass pyrolysis cogeneration system, which includes a biomass pyrolysis oil recovery and utilization system, a pyrolysis gas circulation energy supply system, and a biomass pyrolysis cogeneration system. This technology cannot achieve stable and precise control of the catalytic pyrolysis process. Prior art CN115505409A discloses a biomass pyrolysis self-regulating device for preparing high-quality bio-oil co-generated biochar and its process method, including a biomass pyrolysis self-regulating integrated device, a condenser 1, a condenser 2, a biomass oil collection tank, an induced draft fan 1, and a gas combustion chamber. The device uses a unique layered pyrolysis bed in the pyrolysis chamber, and generates heat through the combustion of non-condensable gas generated by pyrolysis to provide the heat required for pyrolysis, control the pyrolysis temperature, and achieve directional pyrolysis. This technology cannot overcome the drawback of difficult catalyst separation. It is urgent to meet the precise temperature control requirements of the biomass catalytic pyrolysis process through the development of new technologies and innovations in research ideas, overcome the industrial drawbacks of difficult catalyst separation, and promote the high-value utilization of biomass pyrolysis. Summary of the Invention

[0006] In response to the problems of difficulty in precise temperature control and catalyst separation in the process of biomass catalytic pyrolysis in the prior art, the present invention provides a method and device for the co-production of high-value liquid and solid products by self-powered electric heating biomass tempering pyrolysis. The device provided by the present invention mainly includes a feeding module, a pyrolysis module, a condensation module and a self-powered electric heating module. Based on the integration of in-situ tempering and pyrolysis, the pyrolysis path is in-situ regulated by adding a trace amount of potassium metal salt, and the precise temperature control technology of self-powered electric heating molten salt is utilized. The tempering pyrolysis process is uniform, stable and controllable, and the synergistic quality improvement of oil and charcoal products can be achieved. Its purpose is to overcome the inherent defects of traditional biomass catalytic pyrolysis technology such as difficulty in catalyst separation and poor precise temperature control, and to promote the high-value utilization of biomass pyrolysis.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a self-powered electric heating type biomass conditioning pyrolysis co-production of high-value liquid and solid products preparation device, including a feeding module, a pyrolysis module, a condensation module, and a self-powered electric heating module.

[0008] The feeding module is composed of an air compressor A, an air compressor B and a pneumatic feeding device, and the pneumatic feeding device includes a tank body, a fluidizing air inlet, a conveying air inlet, a feeding port and a discharging port; the pyrolysis module is composed of a pyrolysis reactor, a catalyst storage bin and a biochar storage bin, and the pyrolysis reactor includes a raw material inlet, a catalyst inlet, an air outlet, a pyrolysis oil and gas outlet, a pyrolysis charcoal outlet, an agitator, a molten salt heating layer and a reactor body; the condensing module is composed of a condenser, a bio-oil aging tank, an oil-water separator, a light bio-oil storage tank and a heavy bio-oil storage bin, and the condenser includes a pyrolysis oil and gas inlet, a liquid outlet, a gas outlet and a condenser body, the bio-oil aging tank includes a liquid inlet, a light liquid outlet, a heavy bio-oil outlet and a tank body, and the oil-water separator includes a light liquid inlet, a light bio-oil outlet, a heavy bio-oil outlet and a separator body; the self-powered heating module includes a pyrolysis gas storage tank, an internal combustion generator set and a molten salt storage tank; The fluidizing air inlet of the pneumatic feeding device is connected to the air compressor A, and the conveying air inlet is connected to the air compressor B; the pyrolysis reactor is heated with molten salt, the raw material inlet is connected to the discharge port of the pneumatic feeding device, the catalyst inlet is connected to the catalyst storage bin outlet, the pyrolysis oil and gas outlet is connected to the condenser inlet, and the pyrolysis char outlet is connected to the biochar storage bin inlet; The gas outlet of the condenser is connected to the pyrolysis gas storage tank, and the liquid outlet is connected to the liquid inlet of the bio-oil aging tank; the light liquid outlet of the bio-oil aging tank is connected to the light liquid inlet of the oil-water separator, and the heavy bio-oil outlet is connected to the heavy bio-oil storage bin; the light bio-oil outlet of the oil-water separator is connected to the light bio-oil storage tank, and the heavy bio-oil outlet is connected to the heavy bio-oil storage bin; The pyrolysis gas storage tank is connected to an internal combustion generator set to supply gas fuel thereto; the electricity generated by the internal combustion generator set heats the molten salt storage tank via an electric heater, and the remaining electricity is supplied from the external power grid; On the other hand, the present invention provides a method for preparing high-value liquid and solid products by self-powered electric heating biomass conditioning and pyrolysis co-production, based on the above-mentioned preparation device, comprising the following steps: (1) Feeding process: add biomass raw material particles into the pneumatic feeding device through the feeding port; after the feeding is completed, open the fluidizing air inlet and discharge port of the pneumatic feeding device, close the conveying air inlet and feeding port; open the raw material inlet and gas outlet of the pyrolysis reactor, close the catalyst inlet, pyrolysis oil and gas outlet, and pyrolysis carbon outlet; open the air compressor A to fluidize the raw material particles inside the pneumatic feeding device, then open the air compressor B and the conveying air inlet of the pneumatic feeding device to send the fluidized raw material particles into the pyrolysis reactor; (2) Reaction process: open the catalyst inlet of the pyrolysis reactor and input the catalyst from the catalyst storage bin (the catalyst ratio is 0.1-2 wt.% of the raw material, and the catalyst includes but is not limited to potassium phosphate, potassium carbonate, potassium acetate and other potassium salts); then, open the oil and gas outlet of the pyrolysis reactor, close the pyrolysis raw material inlet, catalyst inlet, pyrolysis carbon outlet and gas outlet; start the agitator until the reaction is completed, and temper and pyrolyze the biomass in the pyrolysis reactor in an oxygen-free or inert atmosphere by means of constant temperature molten salt heating, and the pyrolysis temperature is 400-700 o C, time 30-120 min; after the reaction is completed, open the pyrolysis charcoal outlet of the pyrolysis reactor and store the biochar generated by pyrolysis into the biochar storage bin; (3) Condensation process: The hot oil-gas mixture produced by the pyrolysis reactor is condensed and separated in the condenser, and the pyrolysis gas obtained by cooling enters the pyrolysis gas storage tank for standby use; the bio-oil obtained by condensation enters the bio-oil aging tank for natural aging and stratification, and the heavy components precipitated at the bottom enter the heavy bio-oil storage bin, and the crude light bio-oil components on the top enter the oil-water separator for secondary separation. The small amount of heavy components separated also enters the heavy bio-oil storage bin, and the refined light bio-oil obtained by separation enters the light bio-oil storage tank; (4) Heating process: The pyrolysis gas stored in the pyrolysis gas storage tank enters the internal combustion generator set. The electricity generated by combustion heats the molten salt storage tank through the electric heater to provide the heat required by the pyrolysis reactor. The insufficient electricity is provided by the external power grid.

[0009] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention innovatively proposes a new integrated in-situ conditioning approach. By adding a trace amount of potassium metal salt to in-situ regulate the pyrolysis pathway, the method has high low-temperature activity and good catalytic cracking performance. It can significantly increase the content of effective small molecular components in light bio-oil, improve the porosity and yield of pyrolysis biochar, and simultaneously improve the quality of the oil-char products. In addition, the biochar after the reaction does not need to be separated from the potassium salt catalyst and can be used directly as biochar for field return (in this case, the potassium salt serves as a nutrient element), or further activated to produce activated carbon (the in-situ loading of potassium salt can further improve the activation performance).

[0010] (2) This invention proposes for the first time a new technology for precise temperature control of self-powered electric molten salt. The generated pyrolysis gas enters the internal combustion generator set and is converted into electrical energy. The temperature of the molten salt heat transfer medium is precisely controlled by electric heating. The precise temperature control of the external heat source enables fine regulation of the quality and yield distribution of the pyrolysis products. The dynamic agitator in the reactor is coupled to ensure the stability and consistency of the pyrolysis products. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1Schematic diagram of the preparation device of the present invention; in the figure: 1, pneumatic feeding device; 2, pyrolysis reactor; 3, catalyst storage bin; 4, condenser; 5, bio-oil aging tank; 6, oil-water separator; 7, light bio-oil storage tank; 8, pyrolysis gas storage tank; 9, internal combustion generator set; 10, molten salt storage tank; 11, biochar storage bin; 12, heavy bio-oil storage bin; 13, air compressor A; 14, air compressor B.

[0012] Figure 2 This is a structural schematic diagram of the pneumatic feeding device of the present invention; in the figure: 1-1, fluidizing air inlet; 1-2, conveying air inlet; 1-3, feeding port; 1-4, discharge port; 1-5, tank body.

[0013] Figure 3 This is a structural schematic diagram of the pyrolysis reactor of the present invention; in the figure: 2-1, raw material inlet; 2-2, catalyst inlet; 2-3, gas outlet; 2-4, pyrolysis oil and gas outlet; 2-5, pyrolysis carbon outlet; 2-6, agitator; 2-7, molten salt heating layer; 2-8, reactor body.

[0014] Figure 4 Schematic diagram of the structure of the condenser of the present invention; in the figure: 4-1, pyrolysis oil and gas inlet; 4-2, liquid outlet; 4-3, gas outlet; 4-4, condenser body.

[0015] Figure 5 This is a schematic structural diagram of the bio-oil aging tank of the present invention; in the figure: 5-1, liquid inlet; 5-2, light liquid outlet; 5-3, heavy bio-oil outlet; 5-4, tank body.

[0016] Figure 6 This is a structural diagram of the oil-water separator of the present invention; in the figure: 6-1, light liquid inlet; 6-2, light bio-oil outlet; 6-3, heavy bio-oil outlet; 6-4, separator body. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.

[0018] Example 1: A self-powered, electrically heated biomass conditioning and pyrolysis device and method for co-producing high-value liquid and solid products Figure 1 A self-powered, electrically heated biomass conditioning and pyrolysis device for the co-production of high-value liquid and solid products was demonstrated. The invention comprises a feeding module, a pyrolysis module, a condensation module and a self-powered heating module. The feeding module comprises an air compressor A (13), an air compressor B (14) and a pneumatic feeding device (1). The fluidizing air inlet (1-1) of the pneumatic feeding device is connected to the air compressor A (13), and the conveying air inlet (1-2) is connected to the air compressor B (14); the feeding port (1-3) is used to add bio-oil raw material particles, and the typical biomass raw material is lignocellulose agricultural and forestry waste. The discharge port (1-4) is connected to the raw material inlet (2-1) of the pyrolysis reactor, and is used to transport the biomass raw material to the pyrolysis reactor (2).

[0019] The pyrolysis module includes a pyrolysis reactor (2), a catalyst storage bin (3), and a biochar storage bin (11). The pyrolysis reactor (2) is provided with a molten salt heating layer (2-7) on the outside and an agitator (2-6) on the inside, and is heated in the form of constant temperature molten salt heat; the catalyst inlet (2-2) is connected to the outlet of the catalyst storage bin (3), the pyrolysis oil and gas outlet (2-4) is connected to the condenser inlet (4-1), and the pyrolysis carbon outlet (2-5) is connected to the inlet of the biochar storage bin (11).

[0020] The condensation module includes a condenser (4), a bio-oil aging tank (5), an oil-water separator (6), a light bio-oil storage tank (7), and a heavy bio-oil storage bin (12). The gas outlet (4-3) of the condenser is connected to the pyrolysis gas storage tank (8), and the liquid outlet (4-2) is connected to the liquid inlet (5-1) of the bio-oil aging tank; the light liquid outlet (5-2) of the bio-oil aging tank is connected to the light liquid inlet (6-1) of the oil-water separator, and the heavy bio-oil outlet (5-3) is connected to the heavy bio-oil storage bin (12); the light bio-oil outlet (6-2) of the oil-water separator is connected to the light bio-oil storage tank (7), and the heavy bio-oil outlet (6-3) is connected to the heavy bio-oil storage bin (12).

[0021] The self-powered heating module comprises a pyrolysis gas storage tank (8), an internal combustion generator set (9), and a molten salt storage tank (10). The pyrolysis gas storage tank (8) is connected to the internal combustion generator set (9) to supply gas fuel thereto; the electric energy generated by the internal combustion generator set (9) heats the molten salt storage tank (10) through an electric heater, and the insufficient amount of electricity is input from the external power grid.

[0022] A method for producing narrow mesoporous activated carbon with controllable high specific surface area based on thermal oxidation using the above-mentioned device comprises the following specific steps: Feeding process: biomass raw material particles are added to the pneumatic feeding device (1) through the feeding port (1-3); after the feeding is completed, the fluidizing air inlet (1-1) and the discharge port (1-4) of the pneumatic feeding device are opened, and the conveying air inlet (1-2) and the feeding port (1-3) are closed; the raw material inlet, feeding port (2-1) and the air outlet (2-3) of the pyrolysis reactor are opened, and the catalyst inlet (2-2), the pyrolysis oil and gas outlet (2-4) and the pyrolysis carbon outlet (2-5) are closed; the air compressor A (13) is opened to fluidize the raw material particles inside the pneumatic feeding device, and then the air compressor B (14) and the conveying air inlet (1-2) of the pneumatic feeding device are opened to feed the fluidized raw material particles into the pyrolysis reactor (2).

[0023] Reaction process: open the catalyst inlet (2-2) of the pyrolysis reactor and input the catalyst from the catalyst storage bin (3); then, open the oil and gas outlet (2-4) of the pyrolysis reactor, close the pyrolysis feed inlet (2-1), catalyst inlet (2-2), gas outlet (2-3) and pyrolysis carbon outlet (2-5); start the agitator (2-6) until the reaction is completed, and quench and pyrolyze the biomass in the pyrolysis reactor (2) in an oxygen-free or inert atmosphere by means of constant temperature molten salt heating. The pyrolysis temperature is 400-700 o C, time 30-120 min; after the reaction is completed, open the pyrolysis charcoal outlet (2-5) of the pyrolysis reactor and store the biochar generated by pyrolysis in the biochar storage bin (11).

[0024] Condensation process: The hot oil-gas mixture generated by the pyrolysis reactor (2) is condensed and separated in the condenser (4), and the pyrolysis gas obtained by cooling enters the pyrolysis gas storage tank (8) for standby use; the bio-oil obtained by condensation enters the bio-oil aging tank (5) for natural aging and stratification, and the heavy components precipitated at the bottom enter the heavy bio-oil storage bin (12), and the crude light bio-oil components at the top enter the oil-water separator (6) for secondary separation. The small amount of heavy components separated also enters the heavy bio-oil storage bin (12), and the refined light bio-oil obtained by separation enters the light bio-oil storage tank (7).

[0025] Heating process: The pyrolysis gas stored in the pyrolysis gas storage tank (8) enters the internal combustion generator set (9), and the electricity generated by the combustion heats the molten salt storage tank (10) through the electric heater to provide the constant temperature heat required by the pyrolysis reactor (2). The insufficient electricity is provided by the external power grid.

[0026] The light bio-oil stored in the light bio-oil storage tank (7) has a significantly increased content of effective small molecule components such as carboxyl groups, and uniform and stable content of each component, compared with ordinary pyrolysis products, and can be directly used as an agricultural foliar fertilizer or green pesticide, can significantly improve crop yield, and reduce the use amount of pesticides and chemical fertilizers, and has a trade name of "wood vinegar".

[0027] Embodiment 2: A preparation method of controllable high specific surface area narrow mesoporous activated carbon based on thermal oxidation Based on the device and method of embodiment 1, if the pyrolysis raw material is a biomass raw material rich in silicon elements such as rice husk and bran: The light bio-oil stored in the light bio-oil storage tank (7) has a significantly increased content of effective small molecule components such as carboxyl groups, and uniform and stable content of each component, compared with ordinary pyrolysis products, and can be directly used as an agricultural foliar fertilizer or green pesticide, can significantly improve crop yield, and reduce the use amount of pesticides and chemical fertilizers, and has a trade name of "wood vinegar".

[0028] Embodiment 3: A preparation method of controllable high specific surface area narrow mesoporous activated carbon based on thermal oxidation Based on the device and method of embodiment 1, if the pyrolysis biochar is further used for activation to prepare activated carbon: The pyrolysis biochar stored in the biochar storage bin (11) has a significantly increased porosity and yield, compared with ordinary pyrolysis carbon, and the remaining K catalyst does not need to be separated, can further improve the activation effect, is rich in trace elements such as K and P, and the prepared biomass-based activated carbon has a higher porosity and a smaller amount of activator.

[0029] The above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A self-powered electric heating biomass conditioning pyrolysis co-production device for high-value liquid and solid products, characterized in that: include: Feeding module, pyrolysis module, condensation module, self-powered heating module; The feeding module comprises an air compressor A (13), an air compressor B (14) and a pneumatic feeding device (1); the pyrolysis module comprises a pyrolysis reactor (2), a catalyst storage bin (3) and a biochar storage bin (11); the condensation module comprises a condenser (4), a bio-oil aging tank (5), an oil-water separator (6), a light bio-oil storage tank (7) and a heavy bio-oil storage bin (12); and the self-powered heating module comprises a pyrolysis gas storage tank (8), an internal combustion generator set (9) and a molten salt storage tank (10).

2. The preparation device according to claim 1, characterized in that The pneumatic feeding device (1) is provided with a fluidizing air inlet (1-1), a conveying air inlet (1-2), a feeding port (1-3), a discharging port (1-4) and a tank body (1-5); the pyrolysis reactor (2) is provided with a raw material inlet (2-1), a catalyst inlet (2-2), an air outlet (2-3), a pyrolysis oil and gas outlet (2-4), a pyrolysis carbon outlet (2-5), an agitator (2-6), a molten salt heating layer (2-7) and a reactor body (2-8); the condenser ( 4) is provided with a pyrolysis oil and gas inlet (4-1), a liquid outlet (4-2), a gas outlet (4-3) and a condenser body (4-4); the bio-oil aging tank (5) is provided with a liquid inlet (5-1), a light liquid outlet (5-2), a heavy bio-oil outlet (5-3) and a tank body (5-4); the oil-water separator (6) is provided with a light liquid inlet (6-1), a light bio-oil outlet (6-2), a heavy bio-oil outlet (6-3) and a separator body (6-4).

3. The preparation device according to claim 2, characterized in that The fluidizing air inlet (1-1) of the pneumatic feeding device is connected to the air compressor A (13), the conveying air inlet (1-2) of the pneumatic feeding device is connected to the air compressor B (14), and the discharge port (1-4) of the pneumatic feeding device is connected to the raw material inlet (2-1) of the pyrolysis reactor, so as to transport the biomass raw material to the pyrolysis reactor (2).

4. The preparation device according to claim 1, characterized in that A molten salt heating layer (2-7) is provided outside the pyrolysis reactor (2) for heating in the form of constant-temperature molten salt heat; the catalyst inlet (2-2) is connected to the outlet of the catalyst storage bin (3), the pyrolysis oil and gas outlet (2-4) is connected to the pyrolysis oil and gas inlet (4-1), and the pyrolysis carbon outlet (2-5) is connected to the inlet of the biochar storage bin (11).

5. The preparation device according to claim 1, characterized in that The condenser gas outlet (4-3) is connected to the pyrolysis gas storage tank (8), and the liquid outlet (4-2) is connected to the liquid inlet (5-1) of the bio-oil aging tank; the light liquid outlet (5-2) of the bio-oil aging tank is connected to the light liquid inlet (6-1) of the oil-water separator, and the heavy bio-oil outlet (5-3) is connected to the heavy bio-oil storage bin (12); the light bio-oil outlet (6-2) of the oil-water separator is connected to the light bio-oil storage tank (7), and the heavy bio-oil outlet (6-3) is connected to the heavy bio-oil storage bin (12).

6. The preparation device according to claim 1, characterized in that The pyrolysis gas storage tank (8) is connected to the internal combustion generator set (9) and supplies gas fuel to the internal combustion generator set (9). The electric energy generated by the internal combustion generator set (9) heats the molten salt storage tank (10) through the electric heater, and the insufficient amount of electricity is input from the external power grid.

7. A method for preparing self-powered electric heating biomass conditioning pyrolysis co-production of high-value liquid and solid products, characterized in that: The preparation device according to any one of claims 2 to 8 comprises the following steps: S1. Feeding process: biomass raw material particles are added to the pneumatic feeding device (1) through the feeding port (1-3); after the feeding is completed, the fluidizing air inlet (1-1) and the discharge port (1-4) of the pneumatic feeding device are opened, and the conveying air inlet (1-2) and the feeding port (1-3) are closed; the raw material inlet, feeding port (2-1) and the air outlet (2-3) of the pyrolysis reactor are opened, and the catalyst inlet (2-2), the pyrolysis oil and gas outlet (2-4) and the pyrolysis carbon outlet (2-5) are closed; the air compressor A (13) is opened to fluidize the raw material particles inside the pneumatic feeding device, and then the air compressor B (14) and the conveying air inlet (1-2) of the pneumatic feeding device are opened to feed the fluidized raw material particles into the pyrolysis reactor (2); S2, reaction process: open the catalyst inlet (2-2) of the pyrolysis reactor, input the catalyst from the catalyst storage bin (3); open the oil and gas outlet (2-4) of the pyrolysis reactor, close the pyrolysis feed inlet (2-1), catalyst inlet (2-2), gas outlet (2-3) and pyrolysis carbon outlet (2-5); start the agitator (2-6) until the reaction is completed, and quench and pyrolyze the biomass in the pyrolysis reactor (2) in an oxygen-free or inert atmosphere by means of constant temperature molten salt heating. The pyrolysis temperature is 400-700 o C, time 30-120min; after the reaction is completed, open the pyrolysis charcoal outlet (2-5) of the pyrolysis reactor and store the biochar generated by pyrolysis in the biochar storage bin (11); S3, condensation process: the hot oil-gas mixture generated by the pyrolysis reactor (2) is condensed and separated in the condenser (4), and the pyrolysis gas obtained by cooling enters the pyrolysis gas storage tank (8) for standby use; the bio-oil obtained by condensation enters the bio-oil aging tank (5) for aging and stratification, and the heavy components precipitated at the bottom enter the heavy bio-oil storage bin (12), and the crude light bio-oil components at the top enter the oil-water separator (6) for secondary separation. The small amount of heavy components separated also enters the heavy bio-oil storage bin (12), and the refined light bio-oil obtained by separation enters the light bio-oil storage tank (7); S4. Heating process: The pyrolysis gas stored in the pyrolysis gas storage tank (8) enters the internal combustion generator set (9). The electricity generated by the combustion heats the molten salt storage tank (10) through the electric heater to provide the constant temperature heat required by the pyrolysis reactor (2). The insufficient electricity is provided by the external power grid.

8. The preparation method according to claim 7, characterized in that The biomass raw materials in step S1 include agricultural and forestry wastes, and the agricultural and forestry wastes include rice husks, straws and bamboo chips.

9. The preparation method according to claim 7, characterized in that The catalyst in step S2 includes a metal potassium salt, which includes K2CO3, K3PO4 or CH3COOK; the mass fraction of the catalyst in the raw material is 0.5%-2.0%.

10. The preparation method according to claim 7, characterized in that The constant temperature of the molten salt in the molten salt storage tank (10) in step S4 is 400-700 o C, the pyrolysis reaction kettle (2) is quenched and pyrolyzed for a reaction time of 30-120 min.

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