Experimental pyrolysis furnace and pyrolysis system
By designing multiple pyrolysis modes in the pyrolysis system and using valves and pipe connections, various pyrolysis modes can be achieved, solving the problem of comparing the pyrolysis products and yields of different types of plastics, simplifying the experimental process, and changing the proportion of products and three-phase yields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2023-05-26
- Publication Date
- 2026-06-12
Smart Images
Figure CN116422237B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pyrolysis equipment technology, and in particular to an experimental pyrolysis furnace and pyrolysis system. Background Technology
[0002] Plastics are high molecular weight compounds with good stability and are difficult to degrade naturally. Pyrolysis breaks down the large hydrocarbon chains in plastics into smaller molecules, making it suitable for recycling polyolefin waste plastics to produce oils and chemicals that can be reused, thus reducing fossil fuel consumption. Further purification of the pyrolysis gas, pyrolysis oil, and carbon black produced after waste plastic pyrolysis can yield high-quality chemical products, better achieving an economical and environmentally friendly circular economy for reuse. Current research on the pyrolysis of different types of plastics or mixed plastics requires comparing the products and yields in different reactors. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to overcome the problem in the prior art that it is necessary to conduct pyrolysis in different reactors to compare the products and yields of pyrolysis when studying the pyrolysis of different types of plastics or mixed plastics, and to provide an experimental pyrolysis furnace and pyrolysis system.
[0004] The technical solution adopted by the present invention to solve its technical problem is: a pyrolysis system, including a main gas tank, a pyrolysis furnace, a blower, a condenser, a gas storage tank, and a gas collection tank;
[0005] The main gas tank is connected to the storage tank via a pipeline.
[0006] The pyrolysis furnace is connected to the condenser through pipe c, the gas storage tank is connected to pipe c through pipe a, the pyrolysis furnace is connected to pipe a through pipe b, the condenser is connected to the gas collection tank through pipe d, and pipe d is connected to pipe a through pipe e.
[0007] Pipeline a has a first valve, a second valve, a blower, and a third valve arranged sequentially at intervals. The first valve is located between the gas storage tank and the second valve. The connection between pipeline a and pipeline b is located between the first valve and the second valve.
[0008] A fourth valve is installed on pipe b;
[0009] A fifth valve and a sixth valve are installed on pipe c, and the connection between pipe a and pipe c is located between the fifth valve and the sixth valve;
[0010] A seventh valve is installed on pipe d;
[0011] The eighth valve is installed on pipe e. The connection between pipe e and pipe d is located between the condenser and the seventh valve. The connection between pipe e and pipe a is located between the third valve and the fan.
[0012] Fixed-bed pyrolysis mode: Open the first and fourth valves, close the second valve, and nitrogen enters the pyrolysis furnace; open the fifth and sixth valves, close the third valve, and nitrogen enters the condenser from the pyrolysis furnace; open the seventh valve, close the eighth valve, and nitrogen exits from the condenser and enters the gas collecting tank.
[0013] Fluidized pyrolysis mode with non-condensed cracked gas circulation: First, open all valves 1 through 8 to purge nitrogen into the system until the concentration detector shows a nitrogen concentration of 100%. Then, close valves 1, 6, and 8, leaving the other valves open. At this point, nitrogen fills the entire system, ensuring the pyrolysis process is under anaerobic conditions. Next, turn on the blower and adjust its speed to keep the plastic particles in the pyrolysis furnace suspended. When the concentration in the system does not change, it indicates that pyrolysis is complete. Turn off the blower. Open valves 6 and 1, ensuring the nitrogen pressure in the storage tank is higher than the cracked gas pressure in the system.
[0014] Fluidized pyrolysis mode of cracked gas condensation cycle: Similarly, open all valves 1 through 8, and nitrogen enters the pyrolysis system from the gas storage tank. When the nitrogen concentration in the system reaches 100%, it indicates that the pipelines and equipment in the pyrolysis system are filled with nitrogen and are in an oxygen-free condition. Close valves 1, 3, and 7, and leave the other valves open. Turn on the blower, and the nitrogen, driven by the blower, propels the pyrolysis furnace. When the concentration in the system does not change, it indicates that pyrolysis is complete. Turn off the axial flow blower. Open all valves 1 through 8, and under the pressure difference of the gas storage tank, all the cracked gas in the pyrolysis system is diverted to the gas collection tank. By changing the gas flow direction through a three-way valve, it enters different equipment, thereby realizing three different pyrolysis modes. This meets the needs of multiple pyrolysis modes in the research. By changing the flow path of the cracked gas, one pyrolysis furnace can perform multiple pyrolysis modes, which greatly simplifies the experimental process and changes the proportion of products and three-phase yields.
[0015] Further, a concentration detector is installed on pipe a, and the connection between pipe e and pipe a is located between the concentration detector and the third valve.
[0016] Further, a flow meter is installed on pipe b, located between the pyrolysis furnace and the fourth valve.
[0017] Further, a thermocouple is installed on pipe c, and the thermocouple is located between the pyrolysis furnace and the fifth valve.
[0018] To address the issues of coke adhering to the furnace wall and clogging the air distribution plate after plastic pyrolysis, and the fact that the pyrolysis furnace is cooled to room temperature before cleaning, the entire furnace body is non-removable and made of high-temperature resistant quartz glass, which greatly increases the difficulty of cleaning and the risk of equipment damage, a further pyrolysis furnace is proposed. This furnace includes a furnace body with an outlet sealing end cap and an inlet sealing end cap installed at both ends. A thermocouple is installed on the outlet sealing end cap. An air distribution plate is installed inside the furnace body, and the air distribution plate is connected to the inlet sealing end cap via a support frame.
[0019] The beneficial effects of this invention are: the pyrolysis system provided by this invention can change the flow direction of gas into different devices by a three-way valve to realize three different pyrolysis modes, meet the needs of multiple pyrolysis modes in research, and realize that a pyrolysis furnace can perform multiple pyrolysis modes by changing the flow path of the cracked gas, which greatly simplifies the experimental process and changes the proportion of products and three-phase yield. Attached Figure Description
[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0021] Figure 1 This is a schematic diagram of the structure of the present invention;
[0022] Figure 2 This is a schematic diagram of the structure of the pyrolysis furnace body of the present invention.
[0023] In the diagram: 1. Main gas tank; 2. Pyrolysis furnace; 201. Furnace body; 202. Gas outlet sealing end cap; 203. Gas inlet sealing end cap; 204. Air distribution plate; 205. Support frame; 3. Fan; 4. Condenser; 5. Gas storage tank; 6. Gas collection tank; 701. Pipe a; 702. Pipe b; 703. Pipe c; 704. Pipe d; 705. Pipe e; 801. First valve; 802. Second valve; 803. Third valve; 804. Fourth valve; 805. Fifth valve; 806. Sixth valve; 807. Seventh valve; 808. Eighth valve; 9. Concentration detector; 10. Flow meter; 11. Thermocouple. Detailed Implementation
[0024] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.
[0025] like Figure 1This is a schematic diagram of the structure of the present invention. A pyrolysis system includes a main gas tank 1, a pyrolysis furnace 2, a blower 3, a condenser 4, a gas storage tank 5, and a gas collection tank 6. The blower 3 is an axial flow blower. The atmosphere gas of the pyrolysis system is nitrogen. The main gas tank 1 is an atmosphere gas tank filled with nitrogen. Before pyrolysis begins, the atmosphere gas tank valve is opened to allow nitrogen to completely fill the entire system pipeline, ensuring an oxygen-free pyrolysis environment. The atmosphere gas tank, gas storage tank 5, pyrolysis furnace inlet, and axial flow blower are connected by flexible pipes. The gas storage tank 5, pyrolysis furnace inlet, and blower 3 outlet are respectively connected to a tee. The pyrolysis furnace outlet, condenser inlet, and blower inlet are connected by flexible pipes and tee. The condenser 4 outlet, gas storage tank 5, and blower 3 inlet are connected by flexible pipes and tee. The connecting pipe between the condenser 4 inlet and the blower 3 inlet is equipped with a valve as a bypass pipe to control whether the condenser 4 can enter the circulation pipeline.
[0026] The pyrolysis furnace 2, flow meter 10, concentration detector 9, fan 3 and condenser 4 together form a circulation pipeline that allows the cracked gas to circulate from the inlet and outlet of the pyrolysis furnace;
[0027] Nitrogen gas in the atmosphere tank is depressurized by a pressure reducing valve and then enters the gas storage tank 5, which leads to the pyrolysis furnace 2. After entering the pyrolysis furnace 2, the nitrogen gas carries away the gaseous products of pyrolysis. The cracked gas then enters the condenser 4. The low temperature environment of the condenser 4 causes the low-pour-point oily substances in the cracked gas to condense and be collected in the condenser 4. The non-condensable cracked gas enters the circulation pipeline. The circulation pipeline is equipped with a concentration detection device to detect the concentration of the protective gas nitrogen in the cracked gas, and an axial flow fan to provide power for the circulation to re-enter the pyrolysis furnace. The above is the circulation pipeline of the cracking system and the circulation of the cracked gas after condensation.
[0028] Nitrogen gas in the atmosphere tank is depressurized by a pressure reducing valve. The flow rate and pressure entering the pyrolysis furnace are then measured by a flow meter and pressure gauge on the pipeline. As the nitrogen enters the pyrolysis furnace, it carries away the gas produced during the fluidized pyrolysis of the plastic, which is called pyrolysis gas. A pressure gauge on the pyrolysis furnace outlet pipeline detects the outlet pressure of the pyrolysis gas, thus indicating the pressure drop after pyrolysis in the furnace. The pyrolysis gas is transported via pipeline to a concentration detection device to measure the concentration of the protective gas nitrogen in the pyrolysis gas. A fan powers the pyrolysis gas circulation pipeline, allowing the pyrolysis gas to re-enter the pyrolysis furnace. This is the circulation pipeline of the pyrolysis system, and the pyrolysis gas does not undergo condensation during circulation.
[0029] A tee pipe connecting the gas outlet of the pyrolysis furnace and the tee pipe connecting the inlet of the blower is connected and a valve is installed as a bypass pipe so that the pyrolysis gas does not pass through the condenser 4. The oily gas products in the pyrolysis gas participate in the pyrolysis of plastics in the circulation pipe. A tee pipe connecting the outlet of the condenser 4 and the tee pipe connecting the inlet of the blower is connected and a valve is installed so that the pyrolysis gas passing through the condenser 4 enters the circulation pipe. The pyrolysis gas leaves the oily products and gaseous paraffin in the condenser 4. The remaining non-condensable gases, mainly nitrogen, methane and alkane gases, re-enter the circulation pipe as atmospheric gases.
[0030] The main gas tank 1 is connected to the gas storage tank 5 via a pipeline.
[0031] Pyrolysis furnace 2 is connected to condenser 4 through pipe c703, gas storage tank 5 is connected to pipe c703 through pipe a701, pyrolysis furnace 2 is connected to pipe a701 through pipe b702, and condenser 4 is connected to gas collection tank 6 through pipe d704. Pipe d704 is connected to pipe a701 through pipe e705.
[0032] Pipeline a701 is sequentially equipped with a first valve 801, a second valve 802, a blower 3, and a third valve 803. The first valve 801 is located between the gas storage tank 5 and the second valve 802. The connection between pipeline a701 and pipeline b702 is located between the first valve 801 and the second valve 802. A concentration detector 9 is installed on pipeline a701. The connection between pipeline e705 and pipeline a701 is located between the concentration detector 9 and the third valve 803.
[0033] A fourth valve 804 is arranged on pipe b702, and a flow meter 10 is installed on pipe b702. The flow meter 10 is located between pyrolysis furnace 2 and the fourth valve 804.
[0034] A fifth valve 805 and a sixth valve 806 are arranged on pipe c703. The connection between pipe a701 and pipe c703 is located between the fifth valve 805 and the sixth valve 806. A thermocouple 11 is installed on pipe c703. The thermocouple 11 is located between pyrolysis furnace 2 and the fifth valve 805.
[0035] The seventh valve 807 is installed on pipe d704;
[0036] The eighth valve 808 is installed on pipe E705. The connection between pipe E705 and pipe D704 is located between condenser 4 and seventh valve 807. The connection between pipe E705 and pipe A701 is located between third valve 803 and fan 3. Since the shape and size of plastic particles will affect the fluidization effect and heat transfer efficiency in the fluidized bed, thus changing the distribution and yield of pyrolysis products, the pyrolysis furnace is made of quartz material to observe the changes in the morphology of plastic during pyrolysis and find the appropriate plastic particle morphology. It has three pyrolysis modes: fixed bed pyrolysis, fluidized bed pyrolysis with uncondensed pyrolysis gas circulation, and fluidized bed pyrolysis with condensed pyrolysis gas circulation. It can analyze the differences in pyrolysis products and yields of plastic in fixed bed and fluidized bed. Uncondensed pyrolysis gas contains large-molecule oily substances. By switching whether the uncondensed pyrolysis gas passes through the condenser, it can be explored whether the uncondensed pyrolysis gas will react again or decompose into other small-molecule alkane compounds. The pyrolysis furnace has a detachable design, which facilitates cleaning of the pyrolysis furnace after pyrolysis.
[0037] like Figure 2 As shown, a pyrolysis furnace 2 includes a furnace body 201. Gas outlet sealing end caps 202 and gas inlet sealing end caps 203 are installed at both ends of the furnace body 201. A thermocouple 11 is installed on the gas outlet sealing end cap 202. An air distribution plate 204 is installed inside the furnace body 201 and is connected to the gas inlet sealing end cap 203 via a support frame 205. The pyrolysis furnace uses electric heating wire. The pyrolysis furnace body and the heating chamber base are separate. The heating device on the heating chamber base can be set according to the control panel to the final heating temperature, heating rate, and holding time. Pressure gauges are installed at the inlet and outlet of the pyrolysis furnace to measure the pressure drop and pressure environment of the pyrolysis gas in the furnace. A thermocouple is installed inside the pyrolysis furnace body to record the temperature changes inside the pyrolysis furnace during the pyrolysis process. A flow meter is installed at the inlet of the pyrolysis furnace to measure the flow rate of the atmospheric gas.
[0038] The main body of the pyrolysis furnace is cylindrical, with stainless steel end caps at the top and bottom sections serving as limiters for fixing the pyrolysis furnace. The end caps at the inlet and outlet of the pyrolysis furnace are slightly larger than the quartz cylinder. The inlet and outlet of the pyrolysis furnace are located on the top and bottom end caps. The upper part of the air inlet of the lower end cap has a support frame for supporting the air distribution plate inside the pyrolysis furnace. The sealing device of the main body of the pyrolysis furnace is a fixing sleeve, which consists of a hollow cylinder and a disc. The upper dimension of the hollow cylinder is slightly larger than the end cap and just covers the end cap. The lower dimension of the hollow cylinder is slightly larger than the quartz tube and just covers the quartz tube.
[0039] The sealing device of the pyrolysis furnace body consists of a rubber ring and a compression ring. The rubber ring is tightly fitted to the outer wall of the quartz tube, and the compression ring is located between the two rubber rings. Its size is slightly larger than the quartz tube and just covers it. The end cap and the fixing sleeve have corresponding screw holes and threads for fastening the two components. The quartz tube is divided into upper and lower parts with a quartz ring in the middle. The inner diameter of the quartz ring is slightly smaller than that of the quartz tube. The three parts are welded together to form the quartz tube. The quartz ring acts as a limiter for the air distribution plate and is fixed on the quartz tube.
[0040] By changing the gas flow direction through the first valve 801, the second valve 802, the third valve 803, the fourth valve 804, the fifth valve 805, the sixth valve 806, the seventh valve 807, and the eighth valve 808, three different pyrolysis modes can be achieved; the following study takes the pyrolysis characteristics of pyrolytic polystyrene as an example.
[0041] Fixed-bed pyrolysis mode: Nitrogen gas exits from main gas tank 1, which is an atmosphere gas tank. Since the nitrogen pressure in the atmosphere gas tank exceeds 5 MPa, a pressure reducing valve is installed at the outlet of the atmosphere gas tank to reduce the nitrogen pressure before it enters storage tank 5. The high-pressure nitrogen expands in storage tank 5, reducing its pressure and protecting the pyrolysis furnace 2 from the impact of the high-pressure nitrogen. The low-pressure nitrogen gas exiting storage tank 5 smoothly enters the pyrolysis furnace 2. The first valve 801 and the fourth valve 804 are opened, and the second valve 802 is closed, allowing nitrogen gas to enter the pyrolysis process. In furnace 2; open valves 805 and 806, and close valve 803, allowing nitrogen to enter condenser 4 from furnace 2; open valve 807 and close valve 808, allowing nitrogen to exit condenser 4 and enter gas collecting tank 6; after nitrogen circulates in the above pipelines and equipment for a short period to ensure the pyrolysis system is under oxygen-free conditions; adjust the nitrogen flow rate to 5-10 L / min to ensure the pyrolysis gas can enter condenser 4; start pyrolysis furnace 2 and set the heating rate and time. Pyrolysis furnace 2 is equipped with a heating element... Electrode 11 detects the temperature changes during the pyrolysis process and the corresponding reaction temperatures. The pyrolysis gas, along with the nitrogen flow, carries the reaction gaseous products out of the pyrolysis furnace 2 and into the condenser 4. The gaseous products of pyrolysis condense into oil compounds and organic substances such as paraffin in the low-temperature environment of the condenser 4. The pyrolysis gas after pyrolysis enters the gas collecting tank 6. The solid products of pyrolysis are in the pyrolysis furnace 2, the liquid products are in the condenser 4, and the non-condensable products of the pyrolysis gas are in the pyrolysis gas collecting tank 6. In the fixed-bed pyrolysis mode, the plastics are piled together, resulting in efficient heat transfer. The relatively low decomposition rate means that plastics cannot be completely decomposed to produce alkane compounds with 25-60 carbon molecules. These compounds have high melting points, high boiling points, high density, low volatility, and low viscosity; therefore, they are often used as raw materials for waxes and lubricants. When a large amount of solid paraffin wax needs to be pyrolyzed, a fixed-bed pyrolysis mode is used. The liquid phase products of pyrolysis are mainly styrene and triphenylcyclohexane, with a yield of 33%; the solid phase products are paraffin wax and coke, with a yield of 58%; and the gaseous phase products are toluene and ethylbenzene, with a yield of 9%.
[0042] Fluidized bed pyrolysis mode with non-condensed cracked gas circulation: First, open all valves 801 to 808 to purge nitrogen into the system until the concentration detector 9 shows a nitrogen concentration of 100%. Then, close valves 801, 806, and 808, leaving the other valves open. At this point, nitrogen fills the entire system, ensuring an oxygen-free environment for the pyrolysis process. Next, turn on fan 3 and adjust its speed to keep the plastic particles in the pyrolysis furnace 2 suspended. The nitrogen in the system circulates in the pipeline under the drive of fan 3, passing through the pyrolysis furnace 2, the concentration detector 9, and fan 3 before re-entering the pyrolysis furnace 2. Then, set the heating rate and time of the pyrolysis furnace 2, and the plastic begins to pyrolyze under the condition of cracked gas circulation. When the concentration on the concentration detector 9 does not change... When the pyrolysis is complete, the blower 3 is turned off; the sixth valve 806 and the first valve 801 are opened. The nitrogen pressure in the gas storage tank 5 is higher than the cracked gas pressure in the system, so the cracked gas in the system is carried into the condenser 4, and the condensed cracked gas enters the gas collecting tank 702. Because the cracked gas did not pass through the condenser 4 during the pyrolysis process, the alkane compounds with 10-25 carbon atoms in the cracked gas are decomposed again into alkane compounds with 4-12 carbon atoms in a high-temperature environment. These small molecule hydrocarbon compounds can be reused as fuel. Among the pyrolysis products, the liquid phase products are mainly styrene, methylstyrene, and stilbene, with a yield of 36%; the solid phase product is coke with a yield of 23%; and the gas phase products are toluene, ethylbenzene, methane, and olefin gases with a yield of 41%.
[0043] Fluidized pyrolysis mode of pyrolysis gas condensation cycle: Similarly, all valves 801 to 808 are opened, and nitrogen enters the pyrolysis system from the gas storage tank 5. When the concentration detector 9 shows a nitrogen concentration of 100%, it indicates that the pipelines and equipment in the pyrolysis system are filled with nitrogen and are in an oxygen-free condition. Close valves 801, 803, and 807, and leave the other valves open. Turn on the blower 3. Driven by the blower, the nitrogen keeps the plastic particles in the pyrolysis furnace 2 in a suspended state. The nitrogen passes through the pyrolysis furnace 2, condenser 4, concentration detector 9, and blower 3 in sequence before re-entering the pyrolysis furnace 2 to form a closed loop. Turn on the pyrolysis furnace 2, set the heating rate and time, and the plastic begins fluidized pyrolysis. The pyrolysis gas passes through the condenser 4. In the low-temperature environment, oily substances and low-pour-point compounds will remain in the condenser 4. Similarly, the concentration of nitrogen in the pipeline is detected by the concentration detector 9. Determine the reaction changes and the initial reaction temperature; when the concentration of the concentration detector 9 does not change, it indicates that the pyrolysis is complete, and the axial flow fan is turned off; open all valves 801 to 808, and under the pressure difference of the gas storage tank 5, all the cracked gas in the pyrolysis system is diverted to the gas collection tank 6; the cracked gas is condensed by the condenser 4, and the alkane compounds in the cracked gas are liquefied and remain in the condenser 4, while the small molecule gases such as methane, acetylene, and toluene in the cracked gas continue to participate in the pyrolysis reaction, adding methyl groups to the oil compounds to introduce non-polar groups, increasing the viscosity and consistency of the oil compounds, and improving the heat resistance, oxidation resistance and wear resistance of the oil compounds, so that they can be used as lubricating oil again; the liquid phase products of the pyrolysis are mainly styrene, dimethylfluorene, and dimeric p-xylene, with a yield of 56%, the solid phase product is coke with a yield of 28%, and the gas phase products are methane, toluene, and ethylbenzene with a yield of 16%.
[0044] The above describes the specific implementation methods of the three pyrolysis modes in this pyrolysis system. For the pyrolysis of polystyrene solid waste plastics, the fluidized bed pyrolysis mode with non-condensed cracked gas circulation is suitable for producing small molecule alkane compounds, while the fluidized bed pyrolysis mode with condensed cracked gas circulation is suitable for producing liquid phase oil compounds. This is mainly because the switching of pyrolysis modes affects the heat and mass transfer efficiency of plastic particles during pyrolysis, thereby changing the heat of reaction of the decomposition reaction and resulting in different proportions of pyrolysis products under different pyrolysis modes.
[0045] like Figure 2 As shown in the main body diagram of the pyrolysis furnace, the end cap is sealed with a rubber ring by bolts, and the air distribution plate is fixed at the top and bottom by the support frame and limiter. Because the air distribution plate 204 has uniformly arranged holes, the solid products after pyrolysis may block the holes. This pyrolysis furnace structure is simple to disassemble and has good sealing performance. It also facilitates the cleaning of the quartz tube and air distribution plate after pyrolysis.
[0046] The structure of the pyrolysis furnace includes an outlet sealing end cap 202 and an inlet sealing end cap 203, which together fix the furnace body 201 to the pyrolysis heating equipment. The furnace body 201 has the characteristics of high temperature resistance and transparency, which allows observation of the pyrolysis state of the plastic. A thermocouple 11 is inserted inside the furnace body 201 to monitor the temperature change during the pyrolysis process. There is a part of the furnace body 201 with an inward protruding ring in the middle, which serves as the upper limit device for the air distribution plate 204. A support frame 205 is placed on the diameter-changing section cover of the inlet sealing end cap 203. The support frame 205 serves as the lower limit device for the air distribution plate 204 and also has a supporting function.
[0047] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A pyrolysis system, characterized in that, It includes a main gas tank (1), a pyrolysis furnace (2), a blower (3), a condenser (4), a gas storage tank (5), and a gas collection tank (6); The main gas tank (1) is connected to the gas storage tank (5) via a pipeline. The pyrolysis furnace (2) is connected to the condenser (4) through pipe c (703), the gas storage tank (5) is connected to pipe c (703) through pipe a (701), the pyrolysis furnace (2) is connected to pipe a (701) through pipe b (702), the condenser (4) is connected to the gas collection tank (6) through pipe d (704), and the pipe d (704) is connected to pipe a (701) through pipe e (705). A first valve (801), a second valve (802), a blower (3), and a third valve (803) are arranged sequentially at intervals on pipe a (701). The first valve (801) is located between the gas storage tank (5) and the second valve (802). The connection between pipe a (701) and pipe b (702) is located between the first valve (801) and the second valve (802). A fourth valve (804) is arranged on the pipe b (702); A fifth valve (805) and a sixth valve (806) are arranged on the pipe c (703), and the connection between the pipe a (701) and the pipe c (703) is located between the fifth valve (805) and the sixth valve (806); A seventh valve (807) is installed on the pipe d (704); The pipe e (705) is equipped with an eighth valve (808), the connection between the pipe e (705) and the pipe d (704) is located between the condenser (4) and the seventh valve (807), and the connection between the pipe e (705) and the pipe a (701) is located between the third valve (803) and the fan (3); Fixed bed pyrolysis mode: Open the first valve (801) and the fourth valve (804), close the second valve (802), and nitrogen enters the pyrolysis furnace (2); Open the fifth valve (805) and the sixth valve (806), and close the third valve (803). Nitrogen gas enters the condenser (4) from the pyrolysis furnace (2). Open the seventh valve (807) and close the eighth valve (808). Nitrogen gas exits from the condenser (4) and enters the gas collection tank (6). Fluidized pyrolysis mode of non-condensed cracked gas circulation: Open all first valves (801) to eighth valves (808) to purge nitrogen into the system until the nitrogen concentration is 100%. Then close the first valve (801), sixth valve (806) and eighth valve (808), leaving the other valves open. At this time, nitrogen fills the entire system to ensure that the pyrolysis process is under oxygen-free conditions. Then turn on the blower (3) and adjust the blower speed to keep the plastic particles in the pyrolysis furnace (2) in a suspended state. When the concentration in the system does not change, it means that the pyrolysis is complete. Turn off the blower (3) and open the sixth valve (806) and the first valve (801). Fluidized pyrolysis mode of pyrolysis gas condensation cycle: Similarly, open all first valves (801) to eighth valves (808), and nitrogen enters the pyrolysis system from the gas storage tank (5) until the nitrogen concentration reaches 100%. Then close the first valve (801), third valve (803) and seventh valve (807), and keep the other valves open. Turn on the blower (3), and the nitrogen will drive the pyrolysis furnace (2) under the action of the blower (3). When the concentration in the system does not change, it means that the pyrolysis is completed. Turn off the blower (3). Open all first valves (801) to eighth valves (808), and under the action of the pressure difference of the gas storage tank (5), all the pyrolysis gas in the pyrolysis system is diverted to the gas collection tank (6). A concentration detector (9) is installed on pipe a (701), and the connection between pipe e (705) and pipe a (701) is located between the concentration detector (9) and the third valve (803); A flow meter (10) is installed on the pipe b (702), and the flow meter (10) is located between the pyrolysis furnace (2) and the fourth valve (804); A thermocouple (11) is installed on the pipe c (703), and the thermocouple (11) is located between the pyrolysis furnace (2) and the fifth valve (805).
2. The pyrolysis system as described in claim 1, characterized in that: The pyrolysis furnace (2) includes a furnace body (201). Gas outlet sealing end caps (202) and gas inlet sealing end caps (203) are installed at both ends of the furnace body (201). A thermocouple (11) is installed on the gas outlet sealing end cap (202). An air distribution plate (204) is installed inside the furnace body (201). The air distribution plate (204) is connected to the gas inlet sealing end cap (203) through a support frame (205).