A waste plastic rapid pyrolysis-catalytic device and test method

Abstract

The application provides a kind of waste plastics fast pyrolysis-catalytic device and test method, belong to waste plastics utilization field.The uneven heating in the pyrolysis process, the problem of slow pyrolysis rate of traditional waste plastics pyrolysis-catalytic reaction device is solved.A kind of waste plastics fast pyrolysis-catalytic reaction device, comprising: pyrolysis device, including pyrolysis container, heat carrier medium and heating device, the heat carrier medium is filled in pyrolysis container and is liquid at high temperature, the heating device is equipped on the wall of pyrolysis container;Catalytic cracking device, including reducing pipe, electromagnetic induction heating device and catalytic reaction core, the catalytic reaction core is arranged in the upper half of reducing pipe, the coil of electromagnetic induction heating device is arranged outside the catalytic reaction core.It is mainly used for pyrolysis plastics.

Description

A rapid pyrolysis-catalytic device and test method for waste plastics Technical Field

[0001] This invention belongs to the field of waste plastic utilization, and in particular relates to a rapid pyrolysis-catalytic device and test method for waste plastics. Background Technology

[0002] The widespread use of plastic products is accompanied by the generation of a large amount of waste plastic. Globally, nearly 350 million tons of waste plastic are generated annually, accounting for about 70-85% of the annual plastic production. Currently, common waste plastic treatment and utilization technologies include landfill and incineration. Nearly 12% of waste plastic is incinerated, nearly 79% is landfilled, and the recycling rate is only 9%.

[0003] Due to the ongoing potential harm of landfilling waste plastics to the atmosphere, soil, and water, this disposal method is facing increasing restrictions. Furthermore, incinerating waste plastics often produces toxic gases such as polycyclic aromatic hydrocarbons (PAHs), which can easily cause secondary pollution. In addition, waste plastics are materials containing a large amount of energy and organic polymers. Polyolefins, such as polyethylene (PE), polypropylene (PP), and polystyrene (PS), account for more than half of all waste plastic components. These have high calorific value and can be utilized as renewable resources. Direct landfilling or disposal is a waste of resources and does not conform to the concept of sustainable development. Currently, pyrolysis catalysis of waste plastics to generate important carbon materials such as carbon nanotubes (CNTs) and clean energy such as hydrogen is an important way to utilize waste plastics for high-value purposes.

[0004] Traditional waste plastic pyrolysis-catalytic reactors are typically two-stage systems. The reactor consists of two parts: a pyrolysis section and a catalytic cracking section. Waste plastics are first pyrolyzed into volatiles in the pyrolysis section, and then the volatiles are further catalytically cracked in the catalytic cracking section to yield the desired products, carbon nanotubes and hydrogen. However, this traditional waste plastic pyrolysis-catalytic reactor has significant drawbacks: uneven heating and a large temperature gradient exist during the pyrolysis stage, leading to low pyrolysis efficiency. Furthermore, numerous studies have shown that rapid pyrolysis of waste plastics is beneficial for the generation of gaseous components, and these components are more easily catalytically cracked into carbon nanotubes and hydrogen in the catalytic cracking section. Therefore, rapid pyrolysis of waste plastics can significantly improve product yield. Thus, it is essential to improve traditional waste plastic pyrolysis-catalytic reactors to address the problems of uneven heating and slow pyrolysis rates in the pyrolysis section. Summary of the Invention

[0005] In view of this, the present invention aims to propose a rapid pyrolysis-catalysis device and experimental method for waste plastics, which links the heat transfer medium with the traditional two-stage pyrolysis-catalysis device to solve the problems of uneven heating and slow pyrolysis rate in the traditional waste plastic pyrolysis-catalysis reaction device, thereby improving pyrolysis efficiency and increasing product yield.

[0006] To achieve the above objectives, according to one aspect of the present invention, a rapid pyrolysis-catalytic reaction apparatus for waste plastics is provided, comprising:

[0007] A pyrolysis apparatus includes a pyrolysis container, a heat transfer medium, and a heating device. The heat transfer medium is filled in the pyrolysis container and is liquid at high temperature. The heating device is provided on the wall of the pyrolysis container.

[0008] A catalytic cracking device includes a variable diameter tube, an electromagnetic induction heating device, and a catalytic reaction core. The catalytic reaction core is located in the upper half of the variable diameter tube, and the coil of the electromagnetic induction heating device is located outside the catalytic reaction core.

[0009] Furthermore, the pyrolysis container is provided with a flange at the upper end to ensure the airtightness of the pyrolysis process. The flange includes: a feed channel, a first air inlet channel, an air outlet channel, and multiple first temperature monitoring components.

[0010] Furthermore, the catalytic cracking device is provided with an upper flange and a lower flange at its upper and lower ends respectively to ensure the airtightness of the catalytic cracking process. The upper flange includes a second air inlet channel and multiple second temperature monitoring components, and the lower flange is provided with a discharge channel.

[0011] Furthermore, the first air intake channel is connected to an inert gas supply assembly for supplying inert gas to the pyrolysis vessel and the reducing pipe.

[0012] Furthermore, the feeding channel is connected to a continuous feeding device for continuously conveying waste plastic particles into the pyrolysis vessel.

[0013] Furthermore, the exhaust channel is connected to the second intake channel via a pipe, which is used to introduce the volatiles obtained from the pyrolysis of waste plastics from the pyrolysis device into the catalytic cracking device.

[0014] Furthermore, the pyrolysis vessel is a silicon carbide vessel.

[0015] Furthermore, a porous metal catalyst is disposed within the catalytic reaction core.

[0016] Furthermore, the flange's multiple first temperature monitoring components can be used to monitor the temperature at different locations of the heat transfer medium; the upper flange's multiple second temperature monitoring components can be used to monitor the temperature at different locations of the catalytic reaction core, and all of the temperature monitoring components are thermocouples.

[0017] According to another aspect of the present invention, a test method using the aforementioned rapid pyrolysis-catalytic device for waste plastics is provided, comprising the following steps:

[0018] S1. Air is vented from the pyrolysis unit and catalytic cracking unit through the inert gas supply component, and a gas sampling bag is installed at the outlet end of the gas outlet channel;

[0019] S2. The temperature of the heat transfer medium and the temperature of the porous metal catalyst in the catalytic reaction core are monitored by the first temperature monitoring component and the second temperature monitoring component, respectively. When the heat transfer medium and the porous catalyst reach the target temperature and are maintained for a certain period of time, waste plastic particles are conveyed into the feeding channel.

[0020] S3. Waste plastic particles are pyrolyzed after contacting the heat transfer medium to form volatiles. The volatiles are transported from the gas outlet of the pyrolysis device to the second gas inlet of the catalytic cracking device, and then flow through the porous metal catalyst in the catalytic reaction core for further catalytic cracking. Finally, the gas is discharged from the discharge channel into the gas sampling bag.

[0021] S4. After the reaction is complete, stop conveying the waste plastic particles and wait for all the waste plastic in the reactor to react before turning off the heating device and the electromagnetic induction heating device, removing the gas sampling bag, and the test is over.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This reactor device has a simpler structure and lower cost, which increases the cost control advantage;

[0024] 2. This reactor device, by setting up a pyrolysis device and a catalytic cracking device, can form an in-situ catalytic cracking and carry out a two-step reaction, which can prevent the phenomenon of sample pyrolysis residue poisoning the porous catalyst.

[0025] 3. This reactor device effectively solves the problem of uneven heating of waste plastics during the pyrolysis stage by introducing a heat transfer medium into the pyrolysis unit, thus avoiding incomplete pyrolysis of waste plastics and improving pyrolysis efficiency.

[0026] 4. This reactor device can achieve rapid pyrolysis of waste plastics by introducing a heat transfer medium into the pyrolysis unit, which leads to a significant increase in the gaseous components in the volatiles, which is conducive to the catalytic cracking of volatiles and can significantly improve the yield of the final product. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 is a schematic diagram of the structure of a waste plastic rapid pyrolysis-catalytic cracking reaction device according to the present invention;

[0029] Figure 2 is a flowchart of the experimental method using a waste plastic rapid pyrolysis-catalytic cracking reaction device according to the present invention.

[0030] 1. Pyrolysis apparatus; 1-1. Pyrolysis vessel; 1-2. Heat transfer medium; 1-3. Heating device; 1-4. Waste plastic granules; 2. Flange; 2-1. First air inlet channel; 2-2. Feed channel; 2-3. Air outlet channel; 3. First temperature monitoring component; 3-1. First thermocouple; 3-2. Second thermocouple; 4. Pipe; 5. Upper flange; 5-1. Second air inlet channel; 6. Catalytic cracking apparatus; 6-1. Reducer; 6-2. Electromagnetic induction heating device; 6-3. Catalytic reaction core; 7. Lower flange; 7-1. Discharge channel; 8. Second temperature monitoring component; Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0032] It should be noted that the descriptions of "left," "right," "left side," "right side," "upper part," "lower part," "top," and "bottom" in this invention are defined based on the orientation or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the described structure must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Referring to the accompanying drawings, this embodiment provides a waste plastic pyrolysis-catalytic cracking reactor, comprising:

[0035] The pyrolysis apparatus 1 includes a pyrolysis container 1-1, a heat transfer medium 1-2, and a heating device 1-3. The heat transfer medium 1-2 is filled in the pyrolysis container 1-1 and is liquid at high temperature. The specific temperature is the pyrolysis temperature of the waste plastic during the experiment, such as the common 350℃, 400℃, and 500℃. The heating device 1-3 is provided on the wall of the pyrolysis container 1-1.

[0036] Specifically, the pyrolysis container 1-1 in this application is sealed at the bottom. The size of the pyrolysis container 1-1 is related to the continuous feeding rate and can be designed according to actual conditions. The heat transfer medium 1-2 in this application is molten salt because molten salt has high heat storage capacity and is in a liquid state at high temperatures, allowing it to directly contact the waste plastic particles 1-4 to achieve uniform heat transfer. The heat transfer medium 1-2 occupies approximately 2 / 3 of the volume of the pyrolysis container 1-1. The heating device 1-3 in this application is a resistance wire heating coil, which is tightly attached to the outer wall of the pyrolysis container 1-1. Simultaneously, an insulation layer is provided on the outer wall of the pyrolysis container 1-1 to prevent heat loss. The heating device 1-3 transfers heat to the pyrolysis container 1-1 through contact heat conduction, and then transfers the heat to the heat transfer medium 1-2.

[0037] The catalytic cracking device 6 includes a variable diameter tube 6-1, an electromagnetic induction heating device 6-2, and a catalytic reaction core 6-3. The catalytic reaction core 6-3 is located in the upper half of the variable diameter tube 6-1, and the coil of the electromagnetic induction heating device 6-2 is located outside the catalytic reaction core 6-3. The upper part of the variable diameter tube 6-1 has a slightly larger radius than the lower part; this design ensures that the porous catalyst in the catalytic reaction core 6-3 will not fall off. Furthermore, the height of the upper part is also much greater than that of the lower part. The upper part of the variable diameter tube 6-1 is almost entirely the catalytic reaction core 6-3, with only a small area reserved for buffering gas flow. The catalytic reaction core 6-3 contains a porous metal catalyst. The electromagnetic induction heating device 6-2 supplies high-frequency alternating current to the coil to generate a high-frequency alternating magnetic field. The porous metal catalyst placed within the alternating magnetic field generates eddy currents, thereby generating heat energy. The porous metal catalyst within the catalytic reaction core 6-3 serves as both a high-density heat source and a catalyst.

[0038] In this embodiment, a flange 2 is provided at the upper end of the pyrolysis container 1-1 to ensure the airtightness of the pyrolysis process. The flange 2 includes: a feed channel 2-2, a first air inlet channel 2-1, an air outlet channel 2-3, and multiple first temperature monitoring components 3. Specifically, the feed channel 2-2 is a threaded pipe located at the center of the flange 2. The height and inner diameter of the threaded pipe are related to the continuous feed rate and can be designed according to actual needs.

[0039] In this embodiment, the catalytic cracking device 6 is provided with an upper flange 5 and a lower flange 7 at its upper and lower ends to ensure the airtightness of the catalytic cracking process. The upper flange 5 includes a second air inlet channel 5-1 and a plurality of second temperature monitoring components 8. The lower flange 7 is provided with a discharge channel 7-1.

[0040] In this embodiment, the first air inlet channel 2-1 is connected to the inert gas supply assembly and is used to supply inert gas to the pyrolysis container 1-1 and the reducing pipe 6-1.

[0041] Specifically, the inert gas supply assembly can be a combination of a gas cylinder and a gas pump, along with a flow meter, to deliver inert gas to the pyrolysis container 1-1 and the reducer 6-1. The inert gas can be sourced from nitrogen or similar sources. For the connection method, the output of the gas pump can be connected to the first air inlet channel 2-1, allowing air to be evacuated from the pyrolysis container 1-1 and the reducer 6-1, thus creating an oxygen-free environment. It is important to emphasize that for the creation of an oxygen-free environment, all connections in this application must be airtight to prevent leaks that could compromise the oxygen-free environment.

[0042] In this embodiment, the feeding channel 2-2 is connected to a continuous feeding device for continuously conveying waste plastics 1-4 into the pyrolysis container 1-1. The purpose of this application is to obtain hydrogen, an important clean energy source, and carbon nanotubes, an important carbon material, through the pyrolysis-catalysis of waste plastics. Therefore, it is necessary to avoid using high-grade electrical energy to prevent energy waste. Thus, the feeding method for waste plastics can be a combination of a silo and a screw conveyor.

[0043] Specifically, the conveying pipeline of the screw conveyor can be connected to the discharge port of the hopper. The rotation of the screw shaft then moves the waste plastic within the conveying pipeline. The discharge port of the conveying pipeline is connected to the inlet of feed channel 2-2 via a silicone tube, allowing the material to smoothly enter feed channel 2-2. The screw conveyor is driven by a stepper motor. By applying very low-frequency pulses to the stepper motor, it can operate at approximately a constant speed, resulting in a slow rotation. This ensures that the plastic feeding rate matches the reactor size and the energy input within the reactor. In this embodiment, the stepper motor is adjusted to its lowest speed, resulting in a plastic granule feeding rate of approximately 30 g / h.

[0044] In this embodiment, the exhaust channel 2-3 is connected to the second intake channel 5-1 via a pipe 4, which is used to introduce the volatiles obtained from the pyrolysis of waste plastics from the pyrolysis device 1 into the catalytic cracking device 6. Specifically, the pipe 4 needs to be insulated to prevent the volatiles from condensing inside the pipe.

[0045] Specifically, waste plastic particles 1-4 come into contact with the heat transfer medium 1-2 and undergo a pyrolysis reaction to become volatiles. Due to the rapid pyrolysis, the volatiles are mostly gaseous components with C6 or less. The volatiles flow out from the outlet channel 2-3, flow along the pipe 4 into the second inlet channel 5-1, and then flow through the catalytic reaction core 6-3, where they are further catalytically cracked.

[0046] In this embodiment, the pyrolysis container 1-1 is a silicon carbide container. Silicon carbide has excellent thermal conductivity, which meets the operating conditions of this application.

[0047] In this embodiment, a porous metal catalyst is disposed within the catalytic reaction core 6-3. This porous catalyst is capable of catalyzing the pyrolysis of waste plastics. Existing technology is used, and will not be elaborated upon here. The catalytic reaction core 6-3 can be hollow or porous to support the porous catalyst; therefore, the structural form is not specifically limited. Any structure that can fix the porous metal catalyst, facilitate the reaction, and not impede gas passage can be used in this application.

[0048] In this embodiment, the multiple first temperature monitoring components 3 on the flange 2 can be used to monitor the temperature at different locations of the heat transfer medium 1-2; this device diagram only shows the symmetrically arranged first thermocouples 3-1 and second thermocouples 3-2. Specifically, the number and position of thermocouples can be designed according to actual needs and device size. This arrangement is to solve the problem of uneven heating of waste plastics in the pyrolysis section. Therefore, it is necessary to ensure that the temperature at different locations of the heat transfer medium 1-2 is almost the same throughout the process, so multiple thermocouples are used for measurement. The multiple second temperature monitoring components on the upper flange 5 can be used to monitor the temperature at different locations of the catalytic reaction core. This device diagram only shows the thermocouples 8. Specifically, the number and position of thermocouples can be designed according to actual needs and device size. This arrangement is for precise temperature control of the catalytic reaction core.

[0049] In this embodiment, both the first temperature monitoring component 3 and the second temperature monitoring component 8 are thermocouples, specifically type K thermocouples. The thermocouples can be connected to a data acquisition system, which can utilize existing technology and will not be elaborated upon here.

[0050] According to another aspect of the present invention, a test method using the above-described solar reactor device is provided, comprising the following steps:

[0051] S1. Air is vented from the pyrolysis unit and catalytic cracking unit through the inert gas supply component, and a gas sampling bag is installed at the outlet end of the gas outlet channel;

[0052] S2. The temperature of the heat transfer medium and the temperature of the porous metal catalyst in the catalytic reaction core are monitored by two sets of temperature monitoring components respectively. When the heat transfer medium and the porous catalyst reach the target temperature and are maintained for 5 minutes, waste plastic particles are conveyed into the feeding channel and conveyed by a screw conveyor. The stepper motor speed of the screw conveyor is set to 1 revolution / min.

[0053] S3. Waste plastic particles are pyrolyzed after contact with the heat transfer medium to form volatiles. The volatiles are transported from the gas outlet of the pyrolysis device to the gas inlet of the catalytic cracking device, and then flow through the porous metal catalyst in the catalytic reaction core for further catalytic cracking. Finally, the gas is discharged from the discharge channel into the gas sampling bag.

[0054] S4. After the reaction is complete, stop conveying the waste plastic particles and wait for all the waste plastic in the reactor to react before turning off the heating device and the electromagnetic induction heating device, removing the gas sampling bag, and the test is over.

[0055] Specifically, to ensure the pyrolysis temperature is around 500℃, the optimal temperature for plastic pyrolysis, it must not be too high or too low. Simultaneously, the temperature uniformity of the waste plastic at different points must be guaranteed. Therefore, in this embodiment, a thermocouple is connected to a temperature controller to achieve precise temperature control. Experimental measurements show that the temperature at three different points on the heat transfer medium can be stabilized at 500℃ with an error within 3℃, meeting the experimental requirements.

[0056] Specifically, the catalytic cracking temperature is determined by the center temperature of the catalytic reaction core. Experimental measurements show that the electromagnetic induction heating device can rapidly reach 900℃ within 5 minutes, and the heating rate meets the expected performance of this device.

[0057] To ensure the pyrolysis apparatus can accommodate the height of the electromagnetic induction device, it is initially placed on a scissor lift platform, which is fixed to a movable platform. During the experiment, the reactor can be moved forward, backward, left, and right directly via the movable platform; the apparatus can be moved up and down by operating the scissor lift platform.

[0058] The heating devices, controllers, sensors, and control programs mentioned above are all existing technologies and will not be elaborated upon here.

[0059] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A rapid pyrolysis-catalytic device for waste plastics, characterized in that, include: A pyrolysis device (1) includes a pyrolysis container (1-1), a heat transfer medium (1-2), and a heating device (1-3). The heat transfer medium (1-2) is filled in the pyrolysis container (1-1) and is liquid at high temperature. The heating device (1-3) is provided on the wall of the pyrolysis container (1-1). A catalytic cracking device (6) includes a variable diameter tube (6-1), an electromagnetic induction heating device (6-2), and a catalytic reaction core (6-3). The upper part of the variable diameter tube (6-1) has a larger radius than the lower part. A porous metal catalyst is placed inside the catalytic reaction core (6-3). The catalytic reaction core (6-3) is located in the upper half of the variable diameter tube (6-1). The coil of the electromagnetic induction heating device (6-2) is located outside the catalytic reaction core (6-3). When the heat transfer medium (1-2) and the porous metal catalyst both reach the target temperature and are maintained for a certain period of time, feed is introduced. Waste plastic particles (1-4) are conveyed in the channel (2-2); the upper end of the pyrolysis container (1-1) is provided with a flange (2) to ensure the airtightness of the pyrolysis process. The flange (2) includes: a feeding channel (2-2), a first air inlet channel (2-1), an air outlet channel (2-3), and multiple first temperature monitoring components (3); the upper and lower ends of the catalytic cracking device (6) are respectively provided with an upper flange (5) and a lower flange (7) to ensure the airtightness of the catalytic cracking process. The upper flange (5) includes: a second air inlet channel (5-1) and multiple second temperature monitoring components (8). The lower flange (7) is provided with a discharge channel (7-1); the air outlet channel (2-3) and the second air inlet channel (5-1) are connected by a pipe (4) to introduce the volatiles obtained from the pyrolysis of waste plastics from the pyrolysis device (1) into the catalytic cracking device (6).

2. The waste plastic rapid pyrolysis-catalytic device according to claim 1, characterized in that: The first air inlet channel (2-1) is connected to the inert gas supply assembly and is used to supply inert gas to the pyrolysis container (1-1) and the reducing pipe (6-1).

3. The waste plastic rapid pyrolysis-catalytic device according to claim 1, characterized in that: The feeding channel (2-2) is connected to a continuous feeding device and is used to continuously feed waste plastic particles (1-4) into the pyrolysis container (1-1).

4. The waste plastic rapid pyrolysis-catalytic device according to claim 1, characterized in that: The pyrolysis vessel (1-1) is a silicon carbide vessel.

5. The waste plastic rapid pyrolysis-catalytic device according to claim 1, characterized in that: The flange (2) has multiple first temperature monitoring components (3) for monitoring the temperature at different locations of the heat transfer medium (1-2); the upper flange (5) has multiple second temperature monitoring components (8) for monitoring the temperature at different locations of the catalytic reaction core (6-3), and both the first temperature monitoring components (3) and the second temperature monitoring components (8) are thermocouples.

6. A test method using a waste plastic rapid pyrolysis-catalytic device as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Air is vented from the pyrolysis unit (1) and the catalytic cracking unit (6) through the inert gas supply component, and a gas sampling bag is installed at the outlet end of the discharge channel (7-1); S2. The temperature of the heat transfer medium (1-2) and the temperature of the metal porous catalyst in the catalytic reaction core (6-3) are monitored by the first temperature monitoring component (3) and the second temperature monitoring component (8), respectively. When the heat transfer medium (1-2) and the metal porous catalyst both reach the target temperature and are maintained for a certain period of time, waste plastic particles (1-4) are conveyed into the feed channel (2-2); S3 S1. Waste plastic particles (1-4) are heated and pyrolyzed by the heat transfer medium (1-2) to form volatiles. The volatiles are transported from the gas outlet channel (2-3) to the second gas inlet channel (5-1), and then flow through the catalytic reaction core (6-3) for further catalytic cracking. Finally, the gas is discharged from the discharge channel into the gas sampling bag. S4. After the reaction is completed, the conveying of waste plastic particles (1-4) is stopped and the heating device (1-3) and the electromagnetic induction heating device (6-2) are turned off after all the waste plastics in the reactor device have reacted. The gas sampling bag is removed and the test ends.

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