A method for low-temperature electromagnetic induction pyrolysis of organic solid waste

Abstract

The application discloses a method for low-temperature electromagnetic induction pyrolysis of organic solid waste, which comprises the following steps: feeding the organic solid waste into a reactor, applying an electromagnetic field to the reactor, and realizing synergistic heating of the inner cavity of the reactor by the electromagnetic wave; heating to the preset temperature of the reactor, starting the stirring assembly arranged on the reactor, and stirring the organic solid waste in the reactor; discharging the pyrolysis solid carbon residue from the bottom of the reactor, feeding the cooled carbon residue into a screening device, conveying the screened fine carbon powder back to the reactor, discharging the coarse carbon powder, and collecting the bio-oil and combustible gas generated by pyrolysis. The application is a process integrating electromagnetic synergistic heating, distributed internal heat source of magnetic metal ball chain, self-produced carbon powder closed loop wave absorption catalysis and synergistic pyrolysis, and is suitable for harmless treatment and resourceful disposal of various agricultural and forestry organic solid waste such as white spirit waste, straw and kitchen sludge.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste treatment technology, and in particular relates to a method for low-temperature electromagnetic induced pyrolysis of organic solid waste. Background Technology

[0002] Conventional treatment of organic solid waste is divided into four categories: landfill, composting, incineration, and thermochemical pyrolysis. Landfilling occupies land and leachate pollutes groundwater; composting has a long treatment cycle and poor volume reduction effect; high-temperature incineration easily produces hazardous wastes such as dioxins and fly ash; pyrolysis technology can simultaneously produce combustible gas, bio-oil, and biochar, with significant resource utilization advantages, and is the mainstream development direction of the industry.

[0003] Existing vertical pyrolysis reactors typically employ the following heating pyrolysis methods: 1. External heating pyrolysis: Reaction temperature 500~800℃, high energy consumption; heat is conducted from the outer wall of the reactor inward, resulting in a long heat transfer path and internal temperature differences of ±50~100℃; coking is highly likely under high-temperature conditions, with a coking removal cycle of only 7~15 days, leading to high operation and maintenance costs. 2. Microwave pyrolysis: Utilizes GHz high-frequency electromagnetic waves, but material penetration depth is limited, resulting in uneven heating within large-scale vertical continuous reactors, making it unsuitable for large-capacity continuous production. 3. Conventional induction heating: Only heats the reactor wall, without an internal distributed heat source, resulting in slow internal material heating and a thermal efficiency of only 40%~60%. 4. External carbon catalytic pyrolysis: Requires the purchase of commercial carbon-based catalysts, leading to high procurement costs and complex catalyst separation and recovery processes, making industrial-scale continuous operation difficult.

[0004] Therefore, it is necessary to develop a low-temperature pyrolysis method that features uniform heating, high thermal efficiency, low production cost, and adaptability to continuous production, in order to solve the technical problems of uneven heating, high energy consumption, easy coking, and high operating costs in the existing organic solid waste pyrolysis treatment. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for low-temperature electromagnetic induced pyrolysis of organic solid waste.

[0006] The present invention is achieved through the following technical solutions.

[0007] This invention provides a method for low-temperature electromagnetic induced pyrolysis of organic solid waste, comprising the following steps: S1: Feed organic solid waste into the reactor, apply an electromagnetic field to the reactor, and heat the inner cavity of the reactor to a preset temperature through electromagnetic waves. S2: Start the stirring components installed on the reactor to stir the organic solid waste in the reactor for pyrolysis; S3: After the pyrolysis solid carbon slag is generated at the bottom of the reactor, it is discharged, cooled and sent to the screening device. The screened fine carbon powder is transported back into the reactor, while the coarse carbon powder is discharged. The bio-oil and combustible gas produced by pyrolysis are collected.

[0008] Preferably, an induction coil is wound around the outer wall of the reactor to apply an electromagnetic field of 1 to 10 kHz to heat the reactor.

[0009] Preferably, the reactor is divided into a preheating zone, a main pyrolysis zone, and an upgrading zone along the axial direction from top to bottom; the temperature of the preheating zone is controlled at 200~250℃, the temperature of the main pyrolysis zone is controlled at 315~350℃, and the temperature of the upgrading zone is controlled at 350~420℃, and the organic solid waste moves from the preheating zone to the main pyrolysis zone and the upgrading zone in sequence.

[0010] Preferably, in step S1, inert carrier gas is continuously introduced into the reactor cavity to maintain the overall operating pressure of the reactor cavity <8000Pa.

[0011] Preferably, the stirring assembly includes a rotating shaft rotatably installed inside the reactor cavity, a motor driving the rotating shaft to rotate, and several ball chains hinged to the side wall of the rotating shaft.

[0012] Preferably, the ball chain is arranged in several groups at vertical height along the axis of rotation.

[0013] Preferably, a neodymium iron boron magnetic core is embedded inside each ball of the ball chain, and the surface is covered with an outer layer of ferritic stainless steel or nickel-based alloy with a thickness of 5 mm or more.

[0014] Preferably, the ball chain rotates at a speed of 10-60 rpm in S2, and the length of the ball chain is greater than the distance between the rotating shaft and the inner wall of the reactor.

[0015] Preferably, in step S3, fine carbon powder with a mesh size of ≤100 is screened out and recycled back to the reactor at a recycling ratio of 10% to 30%.

[0016] Preferably, the organic solid waste in S1 is extruded granules with a moisture content of 20% to 30% that have been pretreated by a pretreatment device; in S3, the charcoal powder is first cooled to below 80°C by a cooling conveyor and then sent to a screening device.

[0017] The beneficial effects of this invention are as follows: This invention achieves a synergistic effect through electromagnetic fields, vertically layered magnetically conductive metal ball chains, and self-generated circulating carbon powder: the electromagnetic field synchronously excites eddy current heating of the metal balls, and the circulating carbon powder absorbs heat through dielectric loss, forming a dual complementary synergistic heating mechanism; the continuous stirring motion of the magnetically conductive ball chains ensures that the circulating carbon powder is evenly dispersed throughout the reactor cavity, guaranteeing no local blind spots in catalytic active sites and heating effect; the low-temperature reaction conditions of 315~350℃, combined with a dynamic and continuous wall scraping structure, inhibit coking on the reactor wall and the formation of dioxin precursors; by adjusting three parameters—electromagnetic frequency, stirring speed, and carbon powder circulation ratio—the production ratio of combustible gas, bio-oil, and biochar can be flexibly controlled to adapt to the resource utilization needs of different scenarios. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; In the diagram: 1-reactor, 11-preheating zone, 12-main pyrolysis zone, 13-upgrading zone, 2-screening device, 3-rotating shaft, 4-motor, 5-ball chain, 6-pretreatment equipment, 7-cooling conveyor. Detailed Implementation

[0019] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0020] Example 1: like Figure 1 As shown, a method for low-temperature electromagnetic induced pyrolysis of organic solid waste includes the following steps: S1: Feed organic solid waste into reactor 1, apply an electromagnetic field to reactor 1, and heat the inner cavity of reactor 1 to a preset temperature through electromagnetic waves. S2: Start the stirring assembly installed on reactor 1 to stir the organic solid waste in reactor 1 for pyrolysis; S3: After the pyrolysis solid carbon slag is generated at the bottom of reactor 1, it is discharged, cooled and sent to screening device 2. The screened fine carbon powder is transported back to reactor 1, while the coarse carbon powder is discharged. The bio-oil and combustible gas generated by pyrolysis are collected.

[0021] An induction coil is wound around the outer wall of the reactor 1 to apply an electromagnetic field of 1 kHz to the reactor 1 for heating.

[0022] like Figure 1As shown by the dashed lines, reactor 1 is divided into three zones along the axial direction from top to bottom: a preheating zone 11, a main pyrolysis zone 12, and a upgrading zone 13. The temperature of the preheating zone 11 is controlled at 200~250℃, the temperature of the main pyrolysis zone 12 is controlled at 315~350℃, and the temperature of the upgrading zone 13 is controlled at 350~420℃. Organic solid waste moves sequentially from the preheating zone 11 to the main pyrolysis zone 12 and then to the upgrading zone 13. The temperature control deviation of the three independent temperature-controlled zones is ≤±5℃, and the temperature difference throughout the chamber is ±20~30℃. The main pyrolysis zone 12 in the middle section accounts for more than 60% of the total effective volume of reactor 1, ensuring that the residence time of organic solid waste in the core reaction zone is not less than 30 minutes, achieving sufficient and deep pyrolysis.

[0023] In step S1, inert carrier gas is continuously introduced into the inner cavity of reactor 1 to maintain the overall operating pressure of reactor 1 within <8000Pa, completely isolating external air from entering the cavity and fundamentally preventing oxidation side reactions. Reactor 1 is equipped with a pressure locking protection device of existing technology. When the pressure inside the cavity exceeds 8000Pa, the tail gas pressure relief valve is automatically opened for linkage adjustment. When the pressure is below 500Pa, a trace amount of inert carrier gas is automatically replenished, completely avoiding the safety risks and oxidation side reactions caused by backflow of external air.

[0024] The stirring assembly includes a rotating shaft 3 rotatably installed in the inner cavity of the reactor 1, a motor 4 that drives the rotating shaft 3 to rotate at an adjustable speed, and several ball chains 5 hinged to the side wall of the rotating shaft 3. The rotating shaft 3 is located in the middle of the inner cavity of the reactor 1, and the motor 4 is installed on the outer wall of the reactor 1.

[0025] The ball chain 5 is arranged in several groups along the vertical height of the rotating shaft 3.

[0026] A high-temperature resistant neodymium iron boron magnetic core is embedded inside each ball of the ball chain 5, and the surface is covered with a wear-resistant outer layer of ferritic stainless steel with a thickness of 5 mm or more. It can still stably provide a constant bias magnetic field and mechanical wear resistance under long-term high-temperature conditions of 350℃, with a continuous service life of 2 years or more. Each ball chain can be composed of 3 to 5 ball chains connected in series. The diameter of a single ball is set to Φ20 to 40 mm as needed. The surface of the ball is treated with hard wear-resistant polishing. The ball chain made of metal material stably generates eddy current Joule effect in a 1 to 10 kHz medium-frequency alternating electromagnetic field, forming dozens of uniformly distributed dispersed built-in heat sources in the inner cavity of reactor 1. This significantly shortens the heat transfer distance from the outer wall to the center, which is usually hundreds of centimeters, to less than 100 millimeters, eliminating the problem of heat transfer hysteresis.

[0027] The ball chain 5 rotates at 10 rpm in S2, and its length is greater than the distance between the rotating shaft 3 and the inner wall of the reactor 1. The layered suspended ball chain 5 naturally extends during rotation, continuously rubbing and scraping along the entire circumference of the vertical inner wall of the reactor 1, physically peeling off the uncured coking precursors on the wall surface. Through the vertical disturbance of the ball chain 5, the turbulent mass transfer effect of the solid and gas phases in the inner cavity of the reactor 1 is enhanced, and the axial and radial temperature difference in the inner cavity of the reactor 1 is controlled within ±20~30℃.

[0028] In step S3, fine carbon powder with a particle size of ≤100 mesh is screened out and recycled back to reactor 1 at a 10% recycling ratio. Coarse carbon powder with a particle size >100 mesh is directly sent out for high-value-added resource utilization such as soil improvement and activated carbon preparation, and does not participate in recycling.

[0029] The organic solid waste in S1 is extruded granules with a moisture content of 20% that have been pretreated by the pretreatment equipment 6; in S3, the carbon powder is first cooled to below 80°C by the cooling conveyor 7 (water-cooled screw conveyor) and then sent to the screening device 2.

[0030] The screening device 2, motor 4, pretreatment equipment 6, and cooling conveyor 7 are all existing technologies.

[0031] Example 2: like Figure 1 As shown, a method for low-temperature electromagnetic induced pyrolysis of organic solid waste, based on Example 1, includes the following steps: S1: Feed organic solid waste into reactor 1, apply an electromagnetic field to reactor 1, and heat the inner cavity of reactor 1 to a preset temperature through electromagnetic waves. S2: Start the stirring assembly installed on reactor 1 to stir the organic solid waste in reactor 1 for pyrolysis; S3: After the pyrolysis solid carbon slag is generated at the bottom of reactor 1, it is discharged, cooled and sent to screening device 2. The screened fine carbon powder is transported back to reactor 1, while the coarse carbon powder is discharged. The bio-oil and combustible gas generated by pyrolysis are collected.

[0032] An induction coil is wound around the outer wall of the reactor 1 to apply a 10kHz electromagnetic field to heat the reactor 1.

[0033] The reactor 1 is divided into three zones along the axial direction from top to bottom: a preheating zone 11, a main pyrolysis zone 12, and a upgrading zone 13. The temperature of the preheating zone 1 is controlled at 200~250℃, the temperature of the main pyrolysis zone 12 is controlled at 315~350℃, and the temperature of the upgrading zone 13 is controlled at 350~420℃. Organic solid waste moves from the preheating zone 11 to the main pyrolysis zone 12 and the upgrading zone 13 in sequence.

[0034] In step S1, inert carrier gas is continuously introduced into the inner cavity of reactor 1 to maintain the overall operating pressure of the inner cavity of reactor 1 <8000Pa, completely isolating external air from entering the cavity and preventing oxidation side reactions from occurring at the source.

[0035] The stirring assembly includes a rotating shaft 3 rotatably installed in the inner cavity of the reactor 1, a motor 4 that drives the rotating shaft 3 to rotate, and several ball chains 5 hinged to the side wall of the rotating shaft 3. The rotating shaft 3 is located in the middle of the inner cavity of the reactor 1, and the motor 4 is installed on the outer wall of the reactor 1.

[0036] The ball chain 5 is arranged in several groups along the vertical height of the rotating shaft 3.

[0037] A high-temperature resistant neodymium iron boron magnetic core is embedded inside the single ball of the ball chain 5, and the surface is covered with a wear-resistant outer layer of ferritic stainless steel with a thickness of 5 mm or more. It can still stably provide a constant bias magnetic field and mechanical wear resistance under long-term high-temperature conditions of 350℃, and the continuous service life is greater than or equal to 2 years.

[0038] The ball chain 5 rotates at 60 rpm in S2, and the length of the ball chain 5 is greater than the distance between the rotating shaft 3 and the inner wall of the reactor 1.

[0039] In S3, fine carbon powder with a particle size of ≤100 mesh is screened out and recycled back to reactor 1 at a 30% recycling ratio. Coarse carbon powder with a particle size >100 mesh is directly sent out for high-value-added resource utilization such as soil improvement and activated carbon preparation, and does not participate in recycling.

[0040] The organic solid waste in S1 is extruded granules with a moisture content of 30% that have been pretreated by the pretreatment equipment 6; in S3, the carbon powder is first cooled to below 80°C by the cooling conveyor 7, and then the carbon powder is sent to the screening device 2.

[0041] Example 3: like Figure 1 As shown, a method for low-temperature electromagnetic induced pyrolysis of organic solid waste, based on Example 1, includes the following steps: S1: Feed organic solid waste into reactor 1, apply an electromagnetic field to reactor 1, and heat the inner cavity of reactor 1 to a preset temperature through electromagnetic waves. S2: Heat to the preset temperature of reactor 1, start the stirring component on reactor 1 to stir the organic solid waste in reactor 1 for pyrolysis; S3: After the pyrolysis solid carbon slag is generated at the bottom of reactor 1, it is discharged, cooled and sent to screening device 2. The screened fine carbon powder is transported back to reactor 1, while the coarse carbon powder is discharged. The bio-oil and combustible gas generated by pyrolysis are collected.

[0042] An induction coil is wound around the outer wall of the reactor 1 to apply a 6 kHz electromagnetic field to the reactor 1 for heating.

[0043] The reactor 1 is divided into three zones along the axial direction from top to bottom: a preheating zone 11, a main pyrolysis zone 12, and a upgrading zone 13. The temperature of the preheating zone 1 is controlled at 200~250℃, the temperature of the main pyrolysis zone 12 is controlled at 315~350℃, and the temperature of the upgrading zone 13 is controlled at 350~420℃. Organic solid waste moves from the preheating zone 11 to the main pyrolysis zone 12 and the upgrading zone 13 in sequence.

[0044] In step S1, inert carrier gas is continuously introduced into the inner cavity of reactor 1 to maintain the overall operating pressure of the inner cavity of reactor 1 <8000Pa, completely isolating external air from entering the cavity and preventing oxidation side reactions from occurring at the source.

[0045] The stirring assembly includes a rotating shaft 3 rotatably installed in the inner cavity of the reactor 1, a motor 4 that drives the rotating shaft 3 to rotate, and several ball chains 5 hinged to the side wall of the rotating shaft 3. The rotating shaft 3 is located in the middle of the inner cavity of the reactor 1, and the motor 4 is installed on the outer wall of the reactor 1.

[0046] The ball chain 5 is arranged in several groups along the vertical height of the rotating shaft 3.

[0047] A high-temperature resistant neodymium iron boron magnetic core is embedded inside the single ball of the ball chain 5, and the surface is covered with a wear-resistant outer layer of nickel-based alloy with a thickness of 5 mm or more. It can still stably provide a constant bias magnetic field and mechanical wear resistance under long-term high-temperature conditions of 350°C, and the continuous service life is ≥2 years.

[0048] The ball chain 5 rotates at 40 rpm in S2, and the length of the ball chain 5 is greater than the distance between the rotating shaft 3 and the inner wall of the reactor 1.

[0049] In step S3, fine carbon powder with a particle size of ≤100 mesh is screened out and recycled back to reactor 1 at a 20% recycling ratio. Coarse carbon powder with a particle size >100 mesh is directly sent out for high-value-added resource utilization such as soil improvement and activated carbon preparation, and does not participate in recycling.

[0050] The organic solid waste in S1 is extruded granules with a moisture content of 25% that have been pretreated by the pretreatment equipment 6; in S3, the carbon powder is first cooled to below 80°C by the cooling conveyor 7, and then the carbon powder is sent to the screening device 2.

[0051] The organic solid waste from discarded liquor lees was treated using the methods in Examples 1-3, and the collected data on coarse charcoal powder, bio-oil, and combustible gas are shown in the table below.

[0052] Example 3 was compared with an existing vertical pyrolysis reactor, and 100 tons of organic solid waste from liquor lees were treated respectively. The data obtained are shown in the table below.

[0053] In Examples 1-3, when the goal is to increase the yield of combustible gas, the circulation ratio is increased to 20%-30% to enhance the catalytic bond-breaking effect of charcoal powder and produce more small-molecule gaseous products; when the goal is to increase the output of charcoal powder, the circulation ratio is reduced to 10%-20% to reduce the proportion of internal circulation of charcoal powder and increase the output of external charcoal products.

[0054] For organic solid waste with different characteristics, the corresponding rotation speed can be matched: when processing highly viscous slag-type materials, the rotation speed can be increased to 40~60rpm to enhance the scraping and anti-coking effect; when processing loose straw-type materials, the rotation speed can be reduced to 10~30rpm to reduce operating energy consumption.

[0055] The specific surface area of ​​the ≤100 mesh recycled fine carbon powder obtained by sieving is greater than or equal to 30 m². 2 / g, with a large number of alkali metal active sites generated during the cracking process naturally loaded on the surface, can simultaneously perform dual functions without additional activation treatment: relying on the medium loss effect of carbon to improve the electromagnetic energy utilization rate by more than 15%, and at the same time, as an in-situ catalyst, it reduces the activation energy of bond breaking of organic macromolecules by 20% and improves the yield of light oil and gas products by more than 12%.

[0056] During the rotation of the ball chain 5, the trajectory of all the balls can cover the entire inner wall surface of the reactor 1 in the vertical direction, with no dead corners for scraping. The descaling and maintenance cycle of the equipment in steady-state continuous operation can stably reach 30 to 90 days, which is 3 to 12 times longer than the descaling cycle of the traditional high-temperature pyrolysis process.

[0057] The scope of application of the organic solid waste covers four major categories of agricultural and forestry organic solid waste: liquor lees, agricultural straw, municipal dehydrated kitchen sludge, and garden waste. The overall heating efficiency of the treatment process can reach 75%~85%, which is higher than the 40%~60% thermal efficiency level of traditional external heating pyrolysis. No external carbon-based catalysts are used throughout the process.

Claims

1. A method for low-temperature electromagnetic induction pyrolysis of organic solid waste, characterized in that, Includes the following steps: S1: Feed organic solid waste into reactor (1), apply an electromagnetic field to reactor (1), heat the inner cavity of reactor (1) through electromagnetic waves, and heat the inner cavity of reactor (1) to a preset temperature; S2: Start the stirring assembly on the reactor (1) to stir the organic solid waste in the reactor (1) for cracking; S3: After the pyrolysis solid carbon slag is generated at the bottom of the reactor (1), it is discharged, cooled and sent to the screening device (2). The screened fine carbon powder is transported back to the reactor (1), the coarse carbon powder is discharged, and the bio-oil and combustible gas generated by pyrolysis are collected.

2. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 1, characterized in that: An induction coil is wound around the outer wall of the reactor (1) to apply an electromagnetic field of 1~10kHz to the reactor (1) for heating.

3. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 1, characterized in that: The reactor (1) is divided into three zones along the axial direction from top to bottom: a preheating zone (11), a main pyrolysis zone (12), and a upgrading zone (13). The temperature of the preheating zone (11) is controlled at 200~250℃, the temperature of the main pyrolysis zone (12) is controlled at 315~350℃, and the temperature of the upgrading zone (13) is controlled at 350~420℃. Organic solid waste moves from the preheating zone (11) to the main pyrolysis zone (12) and the upgrading zone (13) in sequence.

4. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 3, characterized in that: In the process of S1, inert carrier gas is introduced into the inner cavity of reactor (1) throughout the process to maintain the overall operating pressure of the inner cavity of reactor (1) <8000Pa.

5. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 1, characterized in that: The stirring assembly includes a rotating shaft (3) rotatably installed in the inner cavity of the reactor (1), a motor (4) that drives the rotating shaft (3) to rotate, and several ball chains (5) hinged to the side wall of the rotating shaft (3).

6. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 5, characterized in that: The ball chain (5) is arranged in several groups at a vertical height along the axis of rotation (3).

7. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 5, characterized in that: Neodymium iron boron magnetic cores are embedded inside the single spheres of the ball chain (5), and the surface is covered with an outer layer of ferritic stainless steel or nickel-based alloy with a thickness of 5 mm or more.

8. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 5, characterized in that: The ball chain (5) rotates at a speed of 10~60 rpm in S2, and the length of the ball chain (5) is greater than the distance between the rotating shaft (3) and the inner wall of the reactor (1).

9. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 1, characterized in that: Fine carbon powder with a mesh size of ≤100 selected from S3 is recycled back to reactor (1) at a recycling ratio of 10%~30%.

10. The method for low-temperature electromagnetic induced pyrolysis of organic solid waste as described in claim 1, characterized in that: The organic solid waste in S1 is extruded granules with a moisture content of 20%~30% that have been pretreated by the pretreatment equipment (6); in S3, the carbon powder is first cooled to below 80°C by the cooling conveyor (7), and then the carbon powder is sent to the screening device (2).

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