A waste plastic pyrolysis-catalytic system and catalytic reforming method based on electromagnetic induction heating

Abstract

The application discloses a waste plastic pyrolysis-catalysis system and a catalytic reforming method based on electromagnetic induction heating, and relates to the technical field of plastic pyrolysis.The application solves the problems of uneven heating, catalyst deactivation, difficult product separation and the like in the existing plastic pyrolysis-catalysis process, and influences the yield and quality of CNTs and H2.The system comprises an air inlet device, a waste plastic pyrolysis device, a waste plastic continuous feeding device, a waste plastic catalytic reforming device and a gas collecting device; the air inlet device is used for providing an argon gas flow to the waste plastic pyrolysis device through an air pipe; the waste plastic continuous feeding device sends waste plastics into the waste plastic pyrolysis device for heating and cracking; pyrolysis products enter the waste plastic catalytic reforming device after passing through the waste plastic pyrolysis device; the waste plastic catalytic reforming device controls the temperature through an electromagnetic induction heating module and optimizes the catalytic reforming process; and the gaseous product after catalytic reforming is collected through the gas collecting device.The application is applied to the field of plastic recycling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic pyrolysis, and particularly relates to a waste plastic pyrolysis-catalysis system based on electromagnetic induction heating. BACKGROUND

[0002] Plastics, especially polyolefins such as polyethylene (PE) and polypropylene (PP), have become a major source of global waste accumulation, with billions of tons of plastic waste being landfilled or polluting the environment every year, causing serious ecological and health threats. In recent years, in order to address this problem, plastic recycling technology has received extensive attention and development, which is mainly divided into three categories: physical recycling, chemical recycling and energy recycling.

[0003] The physical recycling method includes cleaning, shredding and reprocessing, which is economical and technically mature, but requires high purity of plastics, and plastics will gradually degrade after multiple cycles. Chemical recycling generates monomers or low molecular weight compounds by degrading waste plastics, which can be used to synthesize new plastics or chemicals, suitable for mixed or non-recyclable plastics. In contrast, energy recycling recovers heat energy by incinerating plastics, but releases harmful substances such as dioxins, posing a threat to the environment and human health.

[0004] As a new alternative, the pyrolysis-catalysis process of waste plastics is considered a promising method. This process not only alleviates environmental and health problems associated with waste plastics, but also generates products with high added value, such as carbon nanotubes (CNTs) and hydrogen (H2). Specifically, the two-step pyrolysis-catalysis process includes the first step of pyrolytic decomposition of plastics to generate hydrocarbon volatiles, which are then used as precursors for the synthesis of CNTs and H2. Compared with traditional fossil fuel replacement methods, this process can significantly reduce greenhouse gas emissions while reducing dependence on fossil fuels such as natural gas, with potential for sustainable development.

[0005] Although there have been a large number of studies exploring the pyrolysis-catalysis process of plastics, there are still many challenges in heat and mass transfer and reactor design, which affect the yield and quality of CNTs and H2. These challenges mainly include uneven heating, catalyst deactivation and product separation, and further research and optimization are needed. SUMMARY

[0006] The present application aims to address the problems of uneven heating, catalyst deactivation and product separation in the existing pyrolysis-catalysis process of plastics, which affect the yield and quality of CNTs and H2. A waste plastic pyrolysis-catalysis system based on electromagnetic induction heating is proposed, which includes:

[0007] an air inlet device, a waste plastic pyrolysis device, a waste plastic continuous feeding device, a waste plastic catalytic reforming device and a gas collection device;

[0008] The air inlet device is used to provide an argon gas flow to the waste plastic pyrolysis device through the air pipe;

[0009] The waste plastic continuous feeding device sends the waste plastic into the waste plastic pyrolysis device for heating and cracking; the pyrolysis products enter the waste plastic catalytic reforming device after passing through the waste plastic pyrolysis device; the waste plastic catalytic reforming device adjusts the temperature through the electromagnetic induction heating module to optimize the catalytic reforming process; the gaseous products after catalytic reforming are collected by the gas collection device.

[0010] Further, a preferred mode is also proposed, wherein the air inlet device comprises an argon cylinder and a PU air pipe, the PU air pipe is connected with the argon cylinder and is arranged outside the argon cylinder.

[0011] Further, a preferred mode is also proposed, wherein the waste plastic continuous feeding device comprises an extruder and a heat tracing band, the extruder is used to heat the waste plastic to make it melt and flow and push it into the waste plastic pyrolysis device through the heat tracing band; the temperature of the heat tracing band is set to 280℃.

[0012] Further, a preferred mode is also proposed, wherein the feeding rate of the waste plastic continuous feeding device is 0-0.583 g / min.

[0013] Further, a preferred mode is also proposed, wherein the waste plastic pyrolysis device comprises a tubular furnace 41, a temperature controller and a quartz glass tube; the tubular furnace and the temperature controller jointly raise the temperature in the quartz glass tube to a target temperature and maintain it at the target temperature during the pyrolysis experiment; the alumina porous medium is placed at the center position of the quartz glass tube; the waste plastic is pyrolyzed through the porous medium, and the pyrolysis products enter the waste plastic catalytic reforming device after being heated to 200℃ by the heat tracing band.

[0014] Further, a preferred mode is also proposed, wherein the waste plastic catalytic reforming device comprises a temperature controller, an electromagnetic induction coil, a T-shaped thermocouple, a quartz glass tube, a metal porous iron and an electromagnetic induction heating module;

[0015] The metal porous iron is arranged in the center position of the quartz glass tube; the electromagnetic induction coil is arranged outside the center position of the quartz glass tube; one end of the T-shaped thermocouple is inserted into the metal porous iron from the lower end of the quartz glass tube, which is used to measure the temperature of the metal porous iron, and the other end is connected with the temperature controller; when there is a difference between the temperature of the metal porous iron and the target temperature of the catalytic reforming, the temperature controller adjusts the size of the alternating current in the induction coil, thereby adjusting the temperature of the metal porous iron.

[0016] Based on the same inventive concept, the present application also proposes a waste plastic catalytic reforming method based on electromagnetic induction heating, which is realized based on the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating according to any one of the above. The method comprises:

[0017] An argon gas initial flow rate and aeration time are set, and argon gas is introduced into a quartz glass tube;

[0018] The argon gas flow rate is adjusted, and the target temperature of the tube furnace is set; when the tube furnace reaches the target temperature, the electromagnetic induction heating module is heated to the target temperature;

[0019] The extruder pushes the molten waste plastic into the tube furnace at a feeding speed of 0.5 g / min;

[0020] The molten waste plastic is preliminarily pyrolyzed into volatile matter through the porous alumina;

[0021] The argon gas carries the volatile matter out of the tube furnace into the catalytic reforming device, and the gas product generated by the catalytic reforming device is collected in a gas bag and analyzed by gas chromatography GC;

[0022] The prepared carbon nanotubes are attached to the metal porous catalyst, and are collected by mechanical vibration separation.

[0023] Further, a preferred mode is also proposed, wherein the argon gas initial flow rate is set to 300 mL / min, and the aeration time is set to 20 min.

[0024] Further, a preferred mode is also proposed, wherein the target temperature of the tube furnace is set to 500 DEG C, and the heating rate is 20 DEG C / min.

[0025] Further, a preferred mode is also proposed, wherein the target temperature of the electromagnetic induction heating module is 900 DEG C.

[0026] The present application has the advantages of:

[0027] The present application proposes a waste plastic pyrolysis-catalytic system based on electromagnetic induction heating, which is used for pyrolyzing waste plastic into carbon nanotubes and hydrogen. The novelty of the system lies in the development of a high-efficiency pyrolysis catalytic process for continuous production of carbon nanotubes (CNTs) and hydrogen (H2) from waste plastic by using electromagnetic induction heating. By using a porous metal catalyst as a catalytic site and a heating carrier, rapid heating is achieved, which greatly improves energy efficiency and product yield. This dual-function method overcomes the typical heat transfer limitations associated with catalytic reforming of plastic pyrolysis hydrocarbons, thereby ensuring uniform temperature distribution and reducing energy consumption. In addition, the use of Fe porous catalysts can selectively produce high-purity CNTs and H2, thereby maximizing the utilization value of waste plastic. At the same time, the present system introduces a continuous feeding system, which is more conducive to realizing large-scale and industrialization.

[0028] The application provides a waste plastic catalytic reforming method based on electromagnetic induction heating.

[0029] The application is applied to the field of plastic recycling. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A waste plastic pyrolysis-catalysis system based on electromagnetic induction heating according to the first embodiment, wherein 1 represents an air inlet device, 2 represents a waste plastic pyrolysis device, 3 represents a waste plastic continuous feeding device, 4 represents a waste plastic catalytic reforming device, 5 represents a gas collection device, 21 represents waste plastic, 22 represents porous alumina, 23 represents a tubular furnace, 31 represents a hot plate belt, 41 represents a temperature controller, 42 represents an electromagnetic induction coil, 43 represents a T-shaped thermocouple, 44 represents a metal porous iron, and 45 represents an electromagnetic induction heating module.

[0031] Figure 2 An example data chart according to the eleventh embodiment, Figure 2 (a) is carbon yield and gas yield, Figure 2 (b) is gas selectivity of different component gases, Figure 2 (c) is carbon nanotube programmed temperature oxidation results, Figure 2 (d) is C atom recovery rate and H atom recovery rate, Figure 2 (e) is SEM characterization of carbon nanotubes, Figure 2 (f) is TEM characterization of carbon nanotubes. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application.

[0033] In the first embodiment, the waste plastic pyrolysis-catalysis system based on electromagnetic induction heating comprises:

[0034] The air inlet device 1, the waste plastic pyrolysis device 2, the waste plastic continuous feeding device 3, the waste plastic catalytic reforming device 4 and the gas collection device 5.

[0035] The gas inlet device 1 is used to provide an argon gas stream to the waste plastic pyrolysis device 2 through the trachea;

[0036] The waste plastic continuous feeding device 3 sends waste plastic into the waste plastic pyrolysis device 2 for heating and cracking; the pyrolysis products enter the waste plastic catalytic reforming device 4 after passing through the waste plastic pyrolysis device 2; the waste plastic catalytic reforming device 4 adjusts the temperature through the electromagnetic induction heating module to optimize the catalytic reforming process; the gas products after catalytic reforming are collected by the gas collection device 5.

[0037] Traditional waste plastic pyrolysis process usually relies on external heating sources such as electric furnace or gas heating, which is prone to uneven heating, resulting in low cracking efficiency and unstable product quality.

[0038] In the system proposed in this embodiment, electromagnetic induction heating technology is adopted, which directly acts on the catalyst and waste plastic itself through high-frequency electromagnetic field, so that more uniform and rapid heating is achieved during the heating process. Electromagnetic induction heating has high energy conversion efficiency, which can improve the temperature of the whole system in a short time and ensure the uniformity of the pyrolysis region temperature, thereby improving the efficiency of the cracking reaction and the quality of the products.

[0039] The gas and liquid products generated during the waste plastic pyrolysis process need to be separated and collected in time. Traditional separation methods often require complex equipment and long operation time, and are prone to cause product loss.

[0040] In this embodiment, the electromagnetic induction heating module in the waste plastic catalytic reforming device adjusts the temperature, which can optimize the conditions of the pyrolysis reaction, so that the gasification and cracking of the reaction products are more complete, thereby improving the yield and purity of the gas products. The products after catalytic reforming are efficiently collected by the gas collection device, reducing the difficulty of separation and improving the overall yield of the system.

[0041] Embodiment two, this embodiment is a further limitation of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating described in embodiment one, the gas inlet device 1 includes an argon cylinder and a PU gas pipe, the PU gas pipe is connected with the argon cylinder and is arranged outside the argon cylinder.

[0042] Argon, as an inert gas, is not easy to react with waste plastic, which is crucial for the pyrolysis process of waste plastic. Traditional pyrolysis process often faces the problem of oxygen participating in oxidation reaction, which not only reduces the quality of products, but also may produce harmful by-products such as toxic gas and black smoke. Argon can effectively isolate oxygen, ensure that waste plastic only undergoes cracking reaction during pyrolysis, and ensure the stability and purity of product quality.

[0043] The argon cylinder is connected to the waste plastic pyrolysis device through a PU gas pipe, which can well control the flow rate and direction of the gas flow. By adjusting the pressure of the argon cylinder, the gas inlet device can accurately control the flow rate of argon entering the waste plastic pyrolysis device, ensuring stable gas flow and avoiding uneven or unstable pyrolysis results caused by gas flow fluctuations. The reasonable design of the gas inlet device and the control of the gas flow are helpful to optimize the entire cracking process, improve energy efficiency and product quality.

[0044] Embodiment three, this embodiment is a further limitation of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating according to embodiment one, the waste plastic continuous feeding device 3 includes an extruder and a heat tracing band, the extruder is used to heat the waste plastic to make it melt and flow and push it into the waste plastic pyrolysis device 2 through the heat tracing band; the temperature of the heat tracing band is set to 280℃.

[0045] The function of the extruder in this embodiment is to heat the waste plastic to a molten state through mechanical pressure and heating. The extrusion process not only efficiently heats the waste plastic, but also converts it from a solid state to a flow state, ensuring that it can participate more uniformly in the subsequent pyrolysis process. The function of the heat tracing band is to maintain a constant temperature for the waste plastic during transportation, avoiding solidification or caking of the waste plastic due to temperature reduction. The continuous heating of the heat tracing band ensures that the waste plastic remains within the appropriate temperature range during transportation, avoiding uneven heating and improving the overall heating efficiency of the system, while preventing the molten waste plastic from cooling and solidifying to block the pipeline.

[0046] The system described in this embodiment uses a continuous feeding device, making the feeding process of waste plastic more smooth, avoiding the temperature fluctuations and downtime that may occur during traditional batch feeding. Through continuous extrusion and heating, the system can realize continuous feeding and pyrolysis of waste plastic, greatly improving production efficiency, reducing downtime and maintaining the stability of the pyrolysis process.

[0047] Embodiment four, this embodiment is a further limitation of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating according to embodiment one, the feeding rate of the waste plastic continuous feeding device 3 is 0-0.583g / min.

[0048] Embodiment five, this embodiment is a further limitation of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating according to embodiment one, the waste plastic pyrolysis device 2 includes a tubular furnace 41, a temperature controller and a quartz glass tube; the tubular furnace 41 and the temperature controller together raise the temperature inside the quartz glass tube to the target temperature and maintain it during the pyrolysis experiment; the alumina porous medium is placed at the center position of the quartz glass tube; the waste plastic is pyrolyzed through the porous medium, and the pyrolysis products enter the waste plastic catalytic reforming device 4 after being heated to 200℃ by the heat tracing band.

[0049] In this embodiment, the temperature controller works in conjunction with the tube furnace to precisely control the temperature inside the quartz glass tube, ensuring that the pyrolysis reaction proceeds stably at the preset target temperature. This precise temperature control avoids the adverse effects of temperature fluctuations on the pyrolysis process, improving the efficiency of waste plastic pyrolysis and the quality of the products. During pyrolysis, the temperature controller continuously monitors and adjusts the temperature, ensuring that the system remains at the target temperature during the pyrolysis experiment, which contributes to the efficient pyrolysis of waste plastics.

[0050] Alumina porous media is placed at the center of a quartz glass tube, which promotes the pyrolysis reaction of waste plastics. Alumina has good thermal stability and catalytic activity, effectively increasing the surface area for the pyrolysis reaction, and its porous structure effectively enhances the reaction rate. This design improves the efficiency of the pyrolysis process and reduces energy consumption. Pyrolysis of waste plastics through a porous media ensures uniform heating, avoids localized overheating or undercooling, and reduces incomplete pyrolysis.

[0051] The pyrolysis products, heated to 200°C via a heating cable, enter the waste plastic catalytic reforming unit. This process helps prevent the pyrolysis products from condensing and clogging the pipes. Heating to 200°C is ideal for guiding the products into the subsequent catalytic reforming unit, further promoting product conversion. The waste plastic catalytic reforming unit further processes the pyrolysis products after pyrolysis, which can improve the conversion rate of waste plastics.

[0052] Implementation Method Six: This implementation method is a further definition of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating described in Implementation Method One. The waste plastic catalytic reforming device 4 includes a temperature controller 41, an electromagnetic induction coil 42, a T-type thermocouple 43, a quartz glass tube, a porous metal iron 44, and an electromagnetic induction heating module 45.

[0053] The porous metal iron 44 is located inside the center of the quartz glass tube; the electromagnetic induction coil 42 is wrapped around the outside of the center of the quartz glass tube; one end of the T-type thermocouple 43 is inserted into the porous metal iron from the bottom of the quartz glass tube to measure the temperature of the porous metal, and the other end is connected to a temperature controller. When there is a difference between the temperature of the porous metal and the target temperature of catalytic reforming, the temperature controller will adjust the magnitude of the alternating current inside the induction coil, thereby adjusting the temperature of the porous metal.

[0054] In this embodiment, the electromagnetic induction coil 42 provides a rapid and efficient heating method. Compared with traditional heat source heating (such as electric heating tubes, combustion, etc.), this heating method can bring the porous iron 44 to the required catalytic reforming temperature in a shorter time, thereby improving the system's operating efficiency. Since electromagnetic induction heating acts directly on the porous iron through current, it ensures uniform heating and avoids problems such as reduced catalytic efficiency or equipment damage caused by uneven temperature.

[0055] Further, the T-type thermocouple 43 cooperates with the temperature controller 41 to monitor the temperature of the metal porous iron in real time. When there is a difference between the temperature and the set catalytic reforming target temperature, the temperature controller adjusts the alternating current in the electromagnetic induction coil, thereby accurately adjusting the heating temperature and ensuring the accuracy and stability of the process temperature control.

[0056] In practical applications, when the metal porous iron needs to be heated to the target temperature, an alternating current is generated inside the electromagnetic induction coil. According to the law of electromagnetic induction, an alternating magnetic field is generated in the surrounding space when the alternating current passes through the induction coil. Due to the excellent electrical conductivity of the metal porous iron, an induced current, known as eddy current, is generated inside it. When the eddy current flows through the metal material, it generates Joule heat due to the presence of electrical resistance, i.e., the material is heated by the current. By using the metal porous catalyst as a heating carrier, rapid volumetric heating can be achieved. At the same time, the metal porous iron 44 also acts as a catalyst, which can provide catalytic action during the waste plastic pyrolysis process. Due to its special structure, the metal porous iron not only provides a large reaction surface area, but also helps to contact the reactants with the catalyst, improving the catalytic efficiency. By using the metal porous iron as a catalyst, it can be reused multiple times during the pyrolysis reaction process, reducing the consumption of catalysts and production costs. The metal porous iron has good thermal conductivity, which can quickly absorb the heat provided by electromagnetic induction heating and effectively transfer the heat to the reactants, promoting the decomposition of plastics and the conversion to carbon nanotubes.

[0057] Further, the separation of the metal porous iron and the product carbon nanotubes can be achieved by simply shaking, avoiding the traditional complicated separation steps and reducing the loss and energy consumption during the separation process. This separation method can effectively avoid the residual catalyst in the final product, improving the purity of the carbon nanotubes and other products.

[0058] Embodiment Seven, a waste plastic catalytic reforming method based on electromagnetic induction heating, the system is realized based on any one of the waste plastic pyrolysis-catalytic systems based on electromagnetic induction heating in embodiments one to six, the method comprises:

[0059] Set the initial flow rate and aeration time of argon gas, and introduce argon gas into the quartz glass tube;

[0060] Adjust the argon gas flow rate and set the target temperature of the tube furnace; when the tube furnace reaches the target temperature, turn on the electromagnetic induction heating module and heat it to the target temperature;

[0061] The extruder pushes the molten waste plastic into the tube furnace at a feed rate of 0.5 g / min;

[0062] The molten waste plastics are initially pyrolyzed into volatile substances through the porous alumina;

[0063] The volatile substances are carried out of the tube furnace by argon gas into the catalytic reforming device, and the gas products generated by the catalytic reforming device are collected in a gas bag and analyzed by gas chromatography (GC).

[0064] The prepared carbon nanotubes are attached to the metal porous catalyst and collected by mechanical vibration separation.

[0065] The method proposed in this embodiment uses electromagnetic induction heating technology, which can achieve rapid and uniform heating. This heating method does not rely on traditional heat exchange methods (such as resistance heating or combustion heating), and can directly heat the target substances (such as waste plastics) in the pipeline, thereby improving the pyrolysis efficiency and shortening the heating time. By precisely controlling the target temperature of the tube furnace, the process of waste plastic cracking can be optimized to ensure that the cracking reaction occurs within the optimal temperature range, thereby improving the quality and yield of the products.

[0066] Argon gas, as an inert gas, can effectively prevent the oxidation of waste plastics during high-temperature cracking, reducing the generation of harmful gases (such as carbon dioxide and carbon monoxide). This not only improves the purity of the cracking process, but also helps to control the emission of toxic gases. The argon gas flow and aeration time can be adjusted according to experimental needs to further optimize the environmental conditions for waste plastic pyrolysis-catalysis, avoiding interference from other gases (such as air), thereby improving the quality of waste plastic pyrolysis-catalysis and the purity of the gas products. The waste plastic cracking products enter the catalytic reforming device through the carrier gas, and the catalytic reforming can effectively convert volatile gases, change their molecular structures, and generate more valuable chemicals (such as olefins and aromatic hydrocarbons). The use of this device can significantly improve the quality of the gas products, providing high-quality raw materials for further chemical synthesis. By analyzing the collected gas products through gas chromatography (GC), the composition of the gas can be accurately monitored, further optimizing the cracking process and catalytic reforming process to ensure product consistency and high quality.

[0067] During the waste plastic pyrolysis-catalysis process, carbon nanotubes can be attached to the metal porous catalyst through the action of the catalyst. This method not only effectively extracts carbon resources from waste plastics, but also allows for the subsequent mechanical vibration separation and collection of carbon nanotubes.

[0068] Embodiment Eight, this embodiment is a further limitation of the waste plastic catalytic reforming method based on electromagnetic induction heating described in Embodiment Seven, wherein the initial argon gas flow rate is set to 300 mL / min and the aeration time is set to 20 min.

[0069] The initial flow rate of argon gas in this embodiment is set to 300 mL / min, which helps to maintain the stability of the atmosphere during the cracking reaction. The aeration time is set to 20 minutes, which can ensure that the argon gas can fully contact the waste plastics in the cracking reaction area at the initial stage of the cracking reaction. This time period helps to complete the pre-treatment of the atmosphere and ensures the smooth progress of the cracking process. Longer aeration time can also help to remove impurity gases in the system and avoid the residual of gases that may have a negative impact on the quality of the cracking products.

[0070] Embodiment Nine, this embodiment is a further limitation of the waste plastic catalytic reforming method based on electromagnetic induction heating described in Embodiment Seven, the target temperature of the tube furnace is set to 500℃, and the heating rate is 20℃ / min.

[0071] In this embodiment, by setting the target temperature of 500℃ and the heating rate of 20℃ / min, excessive cracking caused by excessively high temperature or excessively fast heating rate can be better avoided. For example, if the temperature is too high, it may cause too much light hydrocarbon component in the cracking products, and even may cause the generation of some harmful substances. Reasonable heating rate and temperature setting can ensure that the waste plastics are properly decomposed during the cracking process, and the generation of unwanted by-products is minimized.

[0072] Embodiment Ten, this embodiment is a further limitation of the waste plastic catalytic reforming method based on electromagnetic induction heating described in Embodiment Seven, the target temperature of the electromagnetic induction heating module is 900℃.

[0073] In this embodiment, the target temperature is set to 900℃, which can heat to the required temperature in a shorter time, and the temperature control is accurate, avoiding the temperature fluctuation and overheating phenomenon in the traditional heating method, ensuring the stability of the waste plastic cracking process.

[0074] Embodiment Eleven, see Figure 2 This embodiment is described. This embodiment provides a specific example of the waste plastic pyrolysis-catalytic system based on electromagnetic induction heating described in Embodiment One, and is also used to explain Embodiments Two to Six, specifically:

[0075] (I) Preliminary preparation

[0076] The waste plastics low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), recycled polyethylene (WPE), and recycled polypropylene (WPP) used in the system have a diameter of about 3 mm. They are dried in a vacuum oven at 100°C for 24 hours to remove moisture in the plastic particles, and then subjected to pyrolysis-catalytic reforming experiments. The porous alumina and porous iron catalysts used in the system are cylindrical in shape, with a diameter of 43 mm and a height of 10 mm. The porosity is 0.97, and the metal porous catalysts are divided into 10, 20, and 30 pores per inch (PPI).

[0077] (ii) System implementation process

[0078] First, argon gas is passed into the quartz glass tube of the tube furnace at a flow rate of 300 mL / min for 20 min. Since the quartz glass tube of the tube furnace is connected to the quartz glass tube in the waste plastic catalytic reforming device, it can be ensured that the entire experimental process is in an inert atmosphere. Then, adjust the argon flow to 25 mL / min, set the target temperature of the tube furnace to 500°C, and the heating rate to 20°C / min. Since the electromagnetic induction heating speed is much faster than the tube furnace heating speed, the electromagnetic induction device is heated to the target temperature (900°C) when the tube furnace is about to reach the target temperature. Then, the extruder pushes the molten waste plastic into the tube furnace at a feed rate of 0.5 g / min. The molten waste plastic is preliminarily pyrolyzed into volatile matter after passing through the porous alumina. The volatile matter is carried out of the tube furnace by the carrier gas into the catalytic reforming device, and the gas products produced by the catalytic reforming device are collected in a gas bag and further analyzed by gas chromatography (GC). The prepared carbon nanotubes are attached to the metal porous catalyst and collected by mechanical vibration separation.

[0079] (iii) Data processing

[0080] The experimental gas products are mainly composed of H2, CH4, C2H4, C2H6, and CO. The gas components H2 and CO are determined by the flame ionization detector (FID) in the gas chromatograph (SCION 8500-GC), and the gas components CH4, C2H4, and C2H6 are determined by the thermal conductivity detector (TCD), thereby obtaining the volume fraction V i of all gas products. Since no liquid oil and wax components are produced when the catalytic reforming temperature is greater than 700°C, the total mass of the gas products can be obtained according to the principle of mass conservation.

[0081] m g = m - m s - m a (1)

[0082] where m g is the mass of the gas products, m is the mass of the reactants, and m s is the mass of the solid products, ma The mass of the ash product.

[0083] Yield of each gaseous product component i (mmol / g plastic) is calculated as:

[0084]

[0085] where V i is the volume fraction of gaseous component i (H2, CH4, C2H4, C2H6, CO) as determined by gas chromatography, M i is the molar mass of gaseous component i.

[0086] Selectivity C i (mmol / g plastic) is calculated as:

[0087]

[0088] H atom recovery efficiency E H is calculated as:

[0089]

[0090] C atom recovery efficiency E C is calculated as:

[0091]

[0092] The mass difference of the porous medium before and after the reaction is the mass of the solid product (carbon), and the purity of the carbon nanotubes in the solid product carbon is identified by temperature programmed oxidation (TPO). Carbon nanotubes have a highly ordered graphitized structure, and the oxidation temperature of carbon nanotubes is usually high during TPO. Therefore, the mass loss of solid carbon below 550°C is mainly the oxidation of amorphous carbon. Therefore, the yield of carbon nanotubes can be calculated by multiplying the total mass of carbon in the sample by the proportion of carbon nanotubes in the TPO analysis.

[0093] (IV) Key indicators

[0094] For example, Figure 2As shown, the carbon yield and gas yield of the system, the gas selectivity of different component gases, the carbon nanotube temperature programmed oxidation results, the C atom recovery rate and H atom recovery rate, the SEM characterization of carbon nanotubes, and the TEM characterization of carbon nanotubes were evaluated in the present embodiment. The results show that the waste plastic pyrolysis-catalysis system based on electromagnetic induction heating constructed in the present application has the highest carbon nanotube yield among all current systems. The combination of electromagnetic induction heating and metal porous catalysts (especially iron) provides a promising way for sustainable waste plastic management. The high efficiency, stability and scalability of the system make it a viable option for large-scale applications, which helps to reduce waste and produce valuable materials such as carbon nanotubes and H2.

[0095] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present disclosure, but not to limit the scope of protection, although the present disclosure has been described in detail with reference to the above examples, those skilled in the art should understand: after reading the present disclosure, the skilled person can make various changes, modifications or equivalent replacements to the specific embodiments of the present application, but these changes, modifications or equivalent replacements are all within the protection scope of the disclosed claims.

Claims

1. A waste plastic pyrolysis system based on electromagnetic induction heating, characterized in that, The system includes: The gas intake device (1), the waste plastic pyrolysis device (2), the waste plastic continuous feeding device (3), the waste plastic catalytic reforming device (4), and the gas collection device (5); The air inlet device (1) is used to supply argon gas flow to the waste plastic pyrolysis device (2) through the air pipe; The waste plastic continuous feeding device (3) feeds the waste plastic into the waste plastic pyrolysis device (2) for heating and cracking; the pyrolysis products enter the waste plastic catalytic reforming device (4) after passing through the waste plastic pyrolysis device (2); the waste plastic catalytic reforming device (4) regulates the temperature through the electromagnetic induction heating module to optimize the catalytic reforming process; the gaseous products after catalytic reforming are collected through the gas collection device (5). The waste plastic catalytic reforming device (4) includes a temperature controller (41), an electromagnetic induction coil (42), a T-type thermocouple (43), a first quartz glass tube, a porous metal iron (44), and an electromagnetic induction heating module (45). The porous metal iron (44) is located inside the center of the first quartz glass tube; the electromagnetic induction coil (42) is surrounded outside the center of the first quartz glass tube; one end of the T-type thermocouple (43) is inserted into the porous metal iron from the bottom of the first quartz glass tube to measure the temperature of the porous metal iron, and the other end is connected to a temperature controller. When there is a difference between the temperature of the porous metal iron and the target temperature of catalytic reforming, the temperature controller will adjust the magnitude of the alternating current inside the induction coil, thereby adjusting the temperature of the porous metal iron. The waste plastic continuous feeding device (3) includes an extruder and a first heat tracing cable. The extruder is used to heat the waste plastic so that it melts and flows and is pushed into the waste plastic pyrolysis device (2) through the first heat tracing cable. The temperature of the first heat tracing cable is set to 280°C.

2. The waste plastic pyrolysis system based on electromagnetic induction heating according to claim 1, characterized in that, The air intake device (1) includes an argon cylinder and a PU pipe. The PU pipe is connected to the argon cylinder and is located outside the argon cylinder.

3. The waste plastic pyrolysis system based on electromagnetic induction heating according to claim 1, characterized in that, The feeding rate of the waste plastic continuous feeding device (3) is 0~0.583g / min.

4. The waste plastic pyrolysis system based on electromagnetic induction heating according to claim 1, characterized in that, The waste plastic pyrolysis device (2) includes a tube furnace (21), a temperature controller, and a second quartz glass tube; the tube furnace (21) and the temperature controller together raise the temperature inside the second quartz glass tube to the target temperature and maintain it at the target temperature during the pyrolysis experiment; the alumina porous medium is placed in the center of the second quartz glass tube; the waste plastic is pyrolyzed through the porous medium, and the pyrolysis products are heated to 200°C through a pipeline with a second heating tape and then enter the waste plastic catalytic reforming device (4).

5. A method for pyrolyzing waste plastics based on electromagnetic induction heating, characterized in that, The method is based on the waste plastic pyrolysis system based on electromagnetic induction heating described in claim 4, and the method includes: Set the initial argon flow rate and ventilation time, and introduce argon into the second quartz glass tube; Adjust the argon flow rate and set the target temperature for the tube furnace; when the tube furnace reaches the target temperature, turn on the electromagnetic induction heating module and heat it to the target temperature. The extruder pushes molten waste plastic into the tube furnace at a feeding rate of 0.5 g / min; Molten waste plastics are initially pyrolyzed into volatiles after passing through a porous alumina layer; Argon gas carries the volatiles out of the tubular furnace and into the catalytic reforming unit. The gaseous products generated by the catalytic reforming unit are collected in a gas bag and analyzed by gas chromatography (GC). The prepared carbon nanotubes are attached to a porous metal catalyst and collected by mechanical vibration.

6. The waste plastic pyrolysis method based on electromagnetic induction heating according to claim 5, characterized in that, The initial flow rate of argon gas was set to 300 mL / min, and the ventilation time was set to 20 min.

7. The waste plastic pyrolysis method based on electromagnetic induction heating according to claim 6, characterized in that, The target temperature of the tubular furnace is set to 500℃, and the heating rate is 20℃ / min.

8. The waste plastic pyrolysis method based on electromagnetic induction heating according to claim 7, characterized in that, The target temperature of the electromagnetic induction heating module is 900℃.

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