Method for preparing pyrolytic carbon black through two-step pyrolysis of waste tires in vertical microwave pyrolysis reactor

Abstract

The invention discloses a method for preparing pyrolytic carbon black through two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor, and belongs to the field of waste tire resource utilization. Carbon black and inorganic metal oxide in waste tire rubber powder are used as wave-absorbing media, uniform volume heating is initiated through microwave molecule dipole rotation, and the uniformity of particle size distribution of the carbon black is improved. The ratio of the microwave power to the mass of the rubber powder is adopted as a new criterion of the microwave radiation intensity, and it is ensured that the microwave radiation intensity borne by each gram of the rubber powder is larger than 100 W. The waste tires are subjected to low-power one-time pyrolysis decomposition, and a stable three-phase product is obtained; hydrocarbon residues on the surface of the carbon black are removed through high-power secondary pyrolysis, and the amorphous structure of the carbon black is stabilized by shortening the high-temperature retention time. The pyrolytic carbon black prepared by the method is more uniform in particle size distribution, lower in graphitization degree and enhanced in chemical activity, and the reinforcing performance of the pyrolytic carbon black on rubber is obviously superior to that of the pyrolytic carbon black prepared by a conventional method.

Description

Technical Field

[0001] The invention relates to the technical field of waste tire resource utilization, in particular to a method for preparing pyrolytic carbon black by pyrolyzing waste tires in two steps in a vertical microwave pyrolysis reactor. Background Art

[0002] Tires are made of materials that are highly resistant to chemical and physical changes and are not easily degraded under normal atmospheric conditions. Traditional methods of disposing of waste tires, such as landfilling, not only occupy a large amount of land resources, but also have a serious impact on the environment. Existing treatment technologies include retreading, recycled rubber, production of waste tire rubber powder, incineration, and gasification, but most of these methods have problems such as high energy consumption, low product utilization, and secondary pollution. Therefore, it is urgent to develop an efficient and environmentally friendly method for the treatment of waste tires.

[0003] Pyrolysis technology has become an important development direction for waste tire treatment because of its high efficiency, environmental friendliness and recyclable products (such as pyrolysis oil, pyrolysis gas and pyrolysis carbon black). Compared with traditional pyrolysis, microwave pyrolysis has attracted much attention due to its unique advantages. For example, microwave pyrolysis has better heating uniformity, higher energy efficiency and more precise temperature control capabilities, which can significantly shorten the reaction time and increase the chemical reaction rate. In addition, unlike the "external heating" mode of traditional pyrolysis, microwaves achieve volumetric heating through molecular dipole rotation, thereby reducing the temperature gradient inside and outside the material, reducing the possibility of secondary reactions of primary pyrolysis gases, and improving product quality.

[0004] It is worth noting that carbon black is an important component of tires, and it has a good ability to absorb microwaves during microwave pyrolysis, and can act as a "microwave receptor" to accelerate the pyrolysis reaction. However, the carbon black prepared by traditional fixed-bed one-step pyrolysis has the problem of being covered with an organic colloid layer on the surface, which leads to a reduction in surface active sites and a poor reinforcement effect when used as a tire reinforcing filler. In addition, conventional pyrolysis carbon black has an uneven particle size distribution and poor dispersion, and is prone to graphitization at high temperatures above 1000°C, with enlarged microstructure grains, reduced chemical activity, and a decrease in bonding performance with rubber. Therefore, it is urgent to develop a simple and efficient pyrolysis method that can stabilize the amorphous structure of carbon black, remove the surface organic colloid layer, and obtain carbon black with uniform particle size distribution and excellent reinforcement performance.

[0005] Therefore, the present invention proposes a method for preparing pyrolytic carbon black by pyrolyzing waste tires in two steps using a vertical microwave pyrolysis reactor to solve the deficiencies of the prior art. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor. The method uses low-power microwaves for primary pyrolysis, and then uses high-power microwaves for secondary pyrolysis, and combines ball mill grinding technology to achieve stabilization of the amorphous structure of carbon. This process significantly improves the uniform distribution of carbon black particle size, and effectively solves the problems of poor dispersion and microstructure graphitization of carbon black produced by traditional tire pyrolysis methods.

[0007] To achieve the above object, the present invention is implemented by the following technical scheme: A method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor comprises the following steps: (1) crushing waste automobile tires, performing magnetic separation, separation and cleaning, removing silk fabrics and metal wires, and obtaining waste tire rubber powder; Waste tires contain a large amount of non-degradable rubber and its reinforcing fillers (such as carbon black, sulfides, metal oxides, etc.). Impurities are separated and removed through physical and chemical methods to ensure the purity of the pyrolysis process and the high quality of the product.

[0008] This step can effectively improve the microwave absorption capacity of the rubber powder, making the subsequent microwave pyrolysis reaction more efficient, while reducing the reaction interference caused by impurities, ensuring the purity and performance stability of the product; (2) placing waste tire rubber powder in a vertical microwave pyrolysis reactor and introducing inert gas; (3) Primary pyrolysis: at a frequency of 2.45 GHz and a power of 800 W, waste tire rubber powder is heated from room temperature to 300°C-500°C and kept at this temperature for 20 minutes; (4) Secondary pyrolysis: At a frequency of 2.45 GHz and a power of 1300 W, the primary pyrolysis product is heated to 700°C-900°C, and then cooled naturally after reaching the target temperature; (5) Grind the pyrolytic carbon black at room temperature in a ball mill and dry it in an oven.

[0009] Preferably, the vertical microwave pyrolysis reactor in step (2) is equipped with a K-type thermocouple, which is connected to the vertical microwave pyrolysis reactor through a high-temperature resistant fixing device, and a probe is placed inside the top of the silicon nitride crucible to detect the temperature change inside the crucible; the thermocouple is electrically connected to the temperature control system of the reactor, and the temperature control system achieves real-time and precise control of the heating process by adjusting the microwave power to ensure that the pyrolysis reaction is carried out within a set temperature range.

[0010] The high temperature corrosion resistant fixture is made of stainless steel, nickel-based alloy or ceramic materials to ensure that the K-type thermocouple can work stably and long-term in high temperature and corrosive environment. At the same time, the mechanical fixation or spring loading structure is used to ensure the precise positioning of the probe. The thermocouple monitors the internal temperature of the crucible in real time and transmits the data to the external temperature control system. The crucible is the core container in the reaction chamber. It is made of silicon nitride or aluminum oxide. It has high temperature tolerance and good microwave penetration performance. It matches the internal design of the reactor to ensure uniform heating during the pyrolysis process.

[0011] As an external control unit, the temperature control system is connected to the thermocouple and microwave generator. By collecting the temperature feedback of the reaction chamber, the microwave power output is adjusted in real time to ensure accurate temperature control during the pyrolysis process and meet the target temperature requirements of primary and secondary pyrolysis. The system as a whole realizes closed-loop control from temperature collection, feedback to dynamic adjustment, effectively avoiding overheating or temperature fluctuations.

[0012] Preferably, the inert gas introduced in step (2) is nitrogen, argon or helium, and the inert gas is introduced into the reaction chamber through a conduit at the top or bottom of the reactor, and a porous gas distribution device is provided at the end of the conduit to ensure that the gas is evenly distributed in the reaction chamber; the flow rate of the inert gas is not less than 50 mL / min, and the gas conduit is connected to an exhaust device, and the exhaust device is provided with a condenser and a filter device for recovering gaseous or liquid by-products generated by pyrolysis and discharging waste gas.

[0013] Preferably, the mass of the waste tire rubber powder pyrolyzed each time in step (3) does not exceed 8 g, and is fed into the reactor in batches through a feeding device; the microwave radiation intensity in the reaction chamber is controlled by the ratio of microwave power to rubber powder mass, and the ratio is greater than 100 W / g, so as to ensure that the waste tire rubber powder fully absorbs microwave energy during the pyrolysis process to achieve uniform heating.

[0014] The inert gas environment prevents oxidation reactions from occurring, preventing carbon black from coming into contact with oxygen, which can lead to combustion or degradation. The porous gas distribution device ensures uniform gas flow, optimizing the overall efficiency of the pyrolysis reaction.

[0015] Avoid oxygen from participating in the reaction and improve the purity of the pyrolysis carbon black product; at the same time, recycle by-products such as pyrolysis oil and gas to achieve resource utilization and reduce processing costs.

[0016] Preferably, in step (5), the rotation speed of the ball mill is set to 400 r / min, and the cylinder of the ball mill is filled with steel balls or ceramic balls, and the filling amount is 30%-50% of the cylinder volume; during the operation of the ball mill, the forward and reverse rotation time are set to the same, and the total grinding time is 0.5h-1h.

[0017] Preferably, the temperature range of the drying treatment in step (5) is 80°C-120°C, and a circulating air device is provided in the oven to maintain a uniform temperature in the drying chamber; a timed stirring device is provided during the drying process to prevent agglomeration of carbon black particles; after drying, the carbon black is sealed in a closed storage device to prevent the external environment from affecting its properties.

[0018] The ball mill disperses the carbon black particles through mechanical force to make their particle size more uniform; the drying process improves its storage stability and application performance by removing residual moisture in the carbon black.

[0019] Ball milling and drying treatment not only significantly improves the uniformity of carbon black particle size distribution, but also reduces particle agglomeration, thereby improving the processing performance and industrial application adaptability of carbon black.

[0020] Preferably, the primary pyrolysis temperature in step (3) is in the range of 300°C to 500°C, and microwaves are directly applied to the waste tire rubber powder at a frequency of 2.45 GHz to achieve a gradual temperature increase from room temperature to the target temperature; the gaseous products generated during the pyrolysis process are discharged through an exhaust pipe, and a condenser provided on the exhaust pipe is used to condense and recover volatile oil substances, and the residual solid products are retained in the crucible for secondary pyrolysis.

[0021] Primary pyrolysis uses low-power microwaves to act on waste tire rubber powder to decompose volatile organic matter (such as light hydrocarbons) and separate solids (carbon black) from liquids (pyrolysis oil). Microwaves directly act on the carbon black and metal oxide absorbing components of the rubber powder, uniformly heating them to the target temperature, thereby achieving phase stability of the pyrolysis products.

[0022] Through moderate low temperature control, the complex chemical reaction between impurities in the rubber powder and carbon black at high temperature can be effectively avoided, and three-phase products (carbon black, pyrolysis oil and pyrolysis gas) can be stably generated, providing high-quality initial materials for subsequent processing.

[0023] Preferably, the secondary pyrolysis temperature in step (4) is in the range of 700°C-900°C, and the heating rate is achieved by adjusting the microwave power through a temperature control system. After the product reaches the target temperature, the reactor is in a closed state to prevent oxygen from entering the reaction chamber. After the secondary pyrolysis reaction is completed, the reaction chamber is naturally cooled to room temperature, and the product is transferred or stored in a sealed environment and can be directly used for subsequent processing.

[0024] High-power microwave heating can further remove hydrocarbon residues on the surface of carbon black and improve the surface chemical activity of carbon black. At the same time, by shortening the residence time of carbon black in a high-temperature environment, it inhibits its transformation from an amorphous structure to a graphite structure.

[0025] Secondary pyrolysis significantly improves the surface hydrophilicity and active sites of carbon black, improves its bonding performance with rubber, and enhances its role in rubber reinforcement. In addition, it reduces the graphitization tendency and improves the chemical activity and industrial application value of carbon black.

[0026] The present invention provides a method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor. The method has the following beneficial effects: 1. The present invention adopts a vertical microwave pyrolysis reactor, and uses the ratio of microwave power to the mass of waste tire rubber powder as a new criterion for microwave radiation intensity. The microwave radiation intensity per gram of waste tire rubber powder is set to be greater than 100W. This innovative control parameter significantly optimizes energy utilization efficiency while ensuring the efficient pyrolysis reaction. Compared with traditional external heating methods, microwave pyrolysis can achieve a more uniform heat transfer profile by inducing uniform volume heating through molecular dipole rotation, avoid local overheating, and improve the uniformity of the pyrolysis reaction. This process not only shortens the reaction time and reduces energy consumption, but also effectively improves the particle size distribution of pyrolytic carbon black, making its particle size more uniform and improving product quality.

[0027] 2. The present invention uses the carbon black and metal oxide components in the waste tire rubber powder as the wave absorbing medium, and directly acts on the material through microwaves to achieve rapid heating. Compared with the traditional pyrolysis method, the heating rate of microwave pyrolysis is significantly improved, the heat transfer is more direct and efficient, and the residence time of carbon black in the high temperature environment is reduced. The amorphous structure of carbon black is stabilized, effectively reducing the possibility of its transformation into a graphite structure. This structural stability not only prolongs the service life of carbon black, but also makes its performance in rubber reinforcement more outstanding.

[0028] 3. The present invention uses a two-step pyrolysis process to first complete a pyrolysis at a lower power to remove volatile organic compounds in waste tires, and then complete a secondary pyrolysis at a higher power to remove hydrocarbon residues on the surface of carbon black. This process significantly improves the surface properties of carbon black, effectively improves the hydrophilicity of carbon black, and enhances its surface active sites. At the same time, the reduction in the residual impurity content in carbon black significantly improves its ability to bind to rubber, showing a better effect in terms of rubber reinforcement performance. In addition, the two-step pyrolysis process rationally processes the pyrolysis products in stages, which helps to improve the stability and controllability of the entire process.

[0029] 4. Compared with traditional incineration and gasification treatment technologies, the microwave pyrolysis process of the present invention is a more environmentally friendly way to treat waste tires. The pyrolysis gas and pyrolysis oil produced in the process can be recycled, reducing pollution to the environment. Carbon black, as an important product, has a wide range of industrial application value, achieving the goal of resource utilization of waste tires.

[0030] 5. The microwave pyrolysis process parameters provided by the present invention are highly adjustable and can adapt to the processing requirements of different waste tire materials. By controlling the microwave power, the temperature range and duration of the primary pyrolysis and secondary pyrolysis, the process can be optimized for different product requirements (such as particle size, distribution, surface properties, etc.). This flexibility makes the present invention have a wide range of industrial application potentials and can meet a variety of carbon black production needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the peak fitting result of the Raman test of the pyrolytic carbon black prepared in Example 1; Figure 2 This is the particle size distribution test result of the pyrolytic carbon black prepared in Example 1. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Please see attached Figure 1 -Attached Figure 2 : Embodiment 1: (1) Weigh 6 g of waste tire rubber powder that has been crushed, magnetically separated, separated and cleaned to remove silk fabrics and metal wires, and place it in a vertical microwave pyrolysis reactor. Nitrogen is introduced at a flow rate of 50 mL / min to ensure an oxygen-free environment inside the reaction chamber; after ventilating for 10 minutes, start the microwave heating system, set the microwave power to 800 W, gradually increase the temperature to 400 °C, and maintain the constant temperature for 20 minutes to complete a pyrolysis.

[0034] (2) After the first pyrolysis is completed, the product is further heated to 800 °C at a microwave power of 1300 W for secondary pyrolysis. After the target temperature is reached, the product is naturally cooled to room temperature and the pyrolytic carbon black is taken out.

[0035] (3) The obtained pyrolytic carbon black was placed in a ball mill, the speed of the ball mill was set to 400 r / min, the forward and reverse rotations were run for 15 minutes each, and the total ball milling time was 0.5 hours. The ground product was placed in an oven at 80°C and dried for 10 hours to finally obtain pyrolytic carbon black.

[0036] Test results: Raman spectroscopy and laser particle size tests were performed on the obtained pyrolytic carbon black. The results showed that the Raman analysis D1 peak to G peak area ratio of the pyrolytic carbon black was 2.141, the average particle size was 85.601μm, the particle size distribution was concentrated between 83.17μm and 120.22μm, and the carbon black had a high particle size uniformity and a low degree of graphitization.

[0037] Summary of embodiments: In this embodiment, a primary pyrolysis at 400°C and a secondary pyrolysis at 800°C were adopted, and microwave heating achieved a sufficient pyrolysis reaction, with a uniform particle size distribution of carbon black and a low degree of graphitization, indicating that the two-step pyrolysis process under this temperature condition can significantly improve the quality of carbon black.

[0038] Example 2 (1) Weigh 6 g of waste tire rubber powder, and place it in a vertical microwave pyrolysis reactor after pretreatment. Introduce nitrogen at a flow rate of 50 mL / min for 10 minutes, then start microwave heating, set the microwave power to 800 W, raise the temperature to 300 °C, and keep the temperature constant for 20 minutes to complete the pyrolysis.

[0039] (2) The primary pyrolysis product is further heated to 800°C at a microwave power of 1300 W to complete the secondary pyrolysis. After the target temperature is reached, the product is naturally cooled to room temperature and the pyrolysis carbon black is taken out.

[0040] (3) The obtained pyrolytic carbon black was placed in a ball mill with a speed of 400 r / min. The forward and reverse rotations were run for 15 minutes each, and the total ball milling time was 0.5 hours. The product was then placed in an oven at 80°C and dried for 10 hours to obtain the final pyrolytic carbon black.

[0041] Test results: The Raman analysis D1 peak and G peak area ratio of the pyrolytic carbon black prepared in this way is 2.182, the average particle size is 114.01μm, and the particle size is concentrated between 75.85μm and 173.18μm.

[0042] Summary of embodiments: Compared with Example 1, the primary pyrolysis temperature in Example 2 is lower (300°C), resulting in the incomplete decomposition of some volatile organic compounds, which affects the subsequent microstructure and particle size distribution of carbon black. Although the average particle size increases, the distribution range is relatively wide, indicating that low-temperature primary pyrolysis has some limitations on the uniformity of the product.

[0043] Example 3 (1) Weigh 6 g of waste tire rubber powder, crush it, magnetically separate it, and wash it before placing it in a vertical microwave pyrolysis reactor. Pass nitrogen at a flow rate of 50 mL / min to ensure an oxygen-free environment. After 10 minutes of ventilation, start microwave heating, set the microwave power to 800 W, gradually increase the temperature to 300 °C, and maintain it for 20 minutes to complete a pyrolysis.

[0044] (2) The primary pyrolysis product is further heated to 900°C at a microwave power of 1300 W to complete the secondary pyrolysis. After the target temperature is reached, it is naturally cooled to room temperature and the pyrolytic carbon black is taken out.

[0045] (3) The pyrolytic carbon black was placed in a ball mill with a speed of 400 r / min. The forward and reverse rotations were run for 15 minutes each, and the total ball milling time was 0.5 hours. The ground product was placed in an oven at 80°C and dried for 10 hours to finally obtain pyrolytic carbon black.

[0046] Test results: Raman spectroscopy analysis showed that the D1 peak to G peak area ratio of the pyrolytic carbon black was 2.136, the average particle size was 88.946 μm, and the particle size was concentrated between 69.18 μm and 158.48 μm.

[0047] Summary of embodiments: Compared with Example 2, the secondary pyrolysis temperature in Example 3 is higher (900°C), which further promotes the decomposition of residual organic matter and the activation of the carbon black surface. Although the particle size decreases slightly, its distribution is more uniform, indicating that high-temperature secondary pyrolysis has a positive effect on improving the quality of carbon black. However, too high a temperature may cause some carbon black grains to grow, resulting in a slight graphitization trend.

[0048] Example 4 (1) Weigh 6 g of waste tire rubber powder, crush it, magnetically separate it, and wash it before placing it in a vertical microwave pyrolysis reactor. Pass nitrogen at a flow rate of 50 mL / min to ensure an oxygen-free environment in the reaction chamber. After ventilating for 10 minutes, set the microwave power to 800 W, gradually heat it to 400 °C, and keep the temperature constant for 20 minutes to complete a pyrolysis.

[0049] (2) The primary pyrolysis product is further heated to 700°C at a microwave power of 1300 W to complete the secondary pyrolysis. After the target temperature is reached, it is naturally cooled to room temperature and the pyrolysis carbon black is taken out.

[0050] (3) The pyrolytic carbon black was placed in a ball mill with a speed of 400 r / min, a forward rotation time of 15 minutes and a reverse rotation time of 15 minutes respectively, and a total ball milling time of 0.5 hours. After the ball milling was completed, the pyrolytic carbon black was placed in an oven at 80°C for 10 hours to finally obtain the pyrolytic carbon black.

[0051] Test results: Raman analysis shows that the D1 peak to G peak area ratio of pyrolytic carbon black is 2.024, the average particle size is 141.744μm, and the particle size is concentrated between 100μm and 158.48μm.

[0052] Summary of embodiments: Compared with other examples, the secondary pyrolysis temperature in Example 4 is lower (700°C), and the organic residue on the surface of carbon black cannot be completely removed, resulting in larger carbon black particle size and decreased distribution uniformity. At the same time, the lower temperature limits the activation effect, and the ratio of the D1 peak to the G peak of carbon black is reduced, indicating that the degree of graphitization is relatively high.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor, characterized in that: The following steps are involved: (1) crushing waste automobile tires, performing magnetic separation, separation and cleaning, removing silk fabrics and metal wires, and obtaining waste tire rubber powder; (2) placing waste tire rubber powder in a vertical microwave pyrolysis reactor and introducing inert gas; (3) Primary pyrolysis: at a frequency of 2.45 GHz and a power of 800 W, waste tire rubber powder is heated from room temperature to 300°C-500°C and kept at this temperature for 20 minutes; (4) Secondary pyrolysis: At a frequency of 2.45 GHz and a power of 1300 W, the primary pyrolysis product is heated to 700°C-900°C, and then cooled naturally after reaching the target temperature; (5) Grind the pyrolytic carbon black at room temperature in a ball mill and dry it in an oven.

2. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: The vertical microwave pyrolysis reactor in step (2) is equipped with a K-type thermocouple, which is connected to the vertical microwave pyrolysis reactor via a high-temperature resistant fixing device, and a probe is placed inside the top of the silicon nitride crucible to detect temperature changes inside the crucible; the thermocouple is electrically connected to the temperature control system of the reactor, and the temperature control system achieves real-time and precise control of the heating process by adjusting the microwave power to ensure that the pyrolysis reaction is carried out within a set temperature range.

3. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: The inert gas introduced in step (2) is nitrogen, argon or helium. The inert gas is introduced into the reaction chamber through a conduit at the top or bottom of the reactor. A porous gas distribution device is provided at the end of the conduit to ensure that the gas is evenly distributed in the reaction chamber. The flow rate of the inert gas is not less than 50 mL / min, and the gas conduit is connected to an exhaust device. The exhaust device is provided with a condenser and a filter device for recovering gaseous or liquid by-products generated by pyrolysis and discharging waste gas.

4. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: In the step (3), the mass of the waste tire rubber powder to be pyrolyzed each time does not exceed 8 g, and is fed into the reactor in batches through a feeding device; the microwave radiation intensity in the reaction chamber is controlled by the ratio of microwave power to rubber powder mass, and the ratio is greater than 100 W / g to ensure that the waste tire rubber powder fully absorbs microwave energy during the pyrolysis process to achieve uniform heating.

5. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: In step (5), the rotation speed of the ball mill is set to 400 r / min, and the cylinder of the ball mill is filled with steel balls or ceramic balls, and the filling amount is 30%-50% of the cylinder volume; during the operation of the ball mill, the forward and reverse rotation time are set to the same, and the total grinding time is 0.5h-1h.

6. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: The temperature range of the drying treatment in step (5) is 80°C-120°C, and a circulating air device is provided in the oven to maintain a uniform temperature in the drying chamber; a timed stirring device is provided during the drying process to prevent agglomeration of carbon black particles; after drying, the carbon black is sealed in a sealed storage device to prevent the external environment from affecting its properties.

7. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: The primary pyrolysis temperature in step (3) is in the range of 300°C to 500°C, and microwaves are directly applied to the waste tire rubber powder at a frequency of 2.45 GHz to achieve a gradual increase in temperature from room temperature to the target temperature. The gaseous products generated during the pyrolysis process are discharged through an exhaust pipe, and a condenser provided on the exhaust pipe is used to condense and recover volatile oil substances, and the residual solid products are retained in the crucible for secondary pyrolysis.

8. The method for preparing pyrolytic carbon black by two-step pyrolysis of waste tires in a vertical microwave pyrolysis reactor according to claim 1, characterized in that: The secondary pyrolysis temperature in step (4) is in the range of 700°C to 900°C, and the heating rate is achieved by adjusting the microwave power through the temperature control system. After the product reaches the target temperature, the reactor is in a closed state to prevent oxygen from entering the reaction chamber. After the secondary pyrolysis reaction is completed, the reaction chamber is naturally cooled to room temperature, and the product is transferred or stored in a sealed environment and can be directly used for subsequent processing.

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