Intelligent nitrogen purging system and method for start-up and shut-down of waste tire pyrolysis process

Abstract

This application relates to an intelligent nitrogen purging system and method for starting and stopping a waste tire pyrolysis process. It includes a nitrogen source, a main pipeline on / off valve, a pressure regulating valve, a flow meter, a pressure relief valve, a pressure gauge, an oxygen concentration analyzer, and a programmable logic controller (PLC). It has two purging modes: shutdown purging and pre-start purging. The shutdown purging mode includes two steps: high-temperature purging and low-temperature purging. The pre-start purging mode is a cyclic "pressurization-depressurization" purging mode. Purging stops when the oxygen concentration analyzer detects that the oxygen concentration at the downstream end of the condensation system is consistently below a set safety threshold within a set observation time. This invention determines the purging endpoint in real time through online oxygen concentration analysis, ensuring that the reaction system remains in a safe inert state before and after start-up and shutdown, effectively reducing the risk of deflagration accidents.

Description

Technical Field

[0001] This application relates to the field of waste tire pyrolysis technology, specifically to an intelligent nitrogen purging system and method for starting and stopping a waste tire pyrolysis process. Background Technology

[0002] Waste tire pyrolysis processes materials rich in hydrocarbons. The resulting pyrolysis oil and gas, when mixed with air, can easily form explosive gases. The waste tire pyrolysis unit includes a pyrolysis reactor and a condensation system. The condensation system typically includes a buffer tank and a condenser. During start-up and shutdown, the media and states within the system undergo drastic changes, making these periods high-risk for safety accidents. During shutdown, if heating is stopped directly and the system is allowed to cool naturally, a large amount of flammable oil and gas will remain inside. As the temperature drops, a negative pressure will form inside the system, making it highly susceptible to drawing in air through poorly sealed areas. This air mixes with the residual oil and gas, and an explosion can occur due to residual heat or during the next startup ignition. During startup, if the system is not completely purged of internal air before startup, and materials are directly introduced and heated, an explosive environment will also be created, inevitably leading to deflagration upon ignition. Summary of the Invention

[0003] The purpose of this invention is to provide an intelligent nitrogen purging system and method for starting and stopping a waste tire pyrolysis process. By analyzing the oxygen concentration online in real time to determine the purging endpoint, the system is ensured to remain in a safe inert state before and after starting and stopping, effectively reducing the risk of deflagration accidents.

[0004] The first technical solution adopted in this invention is: an intelligent nitrogen purging system for starting and stopping a waste tire pyrolysis process, including a nitrogen source, a main pipeline on / off valve, a pressure regulating valve, a flow meter, a pressure relief valve, a pressure gauge, an oxygen concentration analyzer, and a programmable logic controller. The nitrogen source and main pipeline on / off valve are located at the front end of the waste tire pyrolysis reactor. The nitrogen source is connected to the main pipeline on / off valve, which is used to adjust the connection status between the waste tire pyrolysis reactor and the nitrogen source according to the control instructions of the programmable logic controller (PLC). The pressure regulating valve is located after the nitrogen source and the main pipeline on / off valve to regulate the nitrogen pressure entering the furnace. The flow meter is located after the pressure regulating valve to measure the nitrogen flow rate entering the furnace. The pressure relief valve is located after the waste tire pyrolysis reactor to relieve pressure on the waste tire pyrolysis reactor according to the control instructions of the PLC. The pressure gauge is located between the waste tire pyrolysis reactor and the pressure relief valve to detect the pressure of the waste tire pyrolysis reactor. The oxygen concentration analyzer is located after the condensation system to detect the oxygen concentration at the condensation system and feed it back to the PLC. The PLC is electrically connected to the nitrogen source, the main pipeline on / off valve, the pressure regulating valve, the flow meter, the pressure relief valve, the pressure gauge, and the oxygen concentration analyzer, and controls the operation of the nitrogen source and the main pipeline on / off valve based on the data transmitted by the flow meter, the pressure gauge, and the oxygen concentration analyzer.

[0005] Furthermore, the programmable logic controller includes a PLC and a distributed control system (DSC).

[0006] The second technical solution adopted by the present invention is: an intelligent nitrogen purging method for starting and stopping a waste tire pyrolysis process, which uses the intelligent nitrogen purging system for starting and stopping a waste tire pyrolysis process as described in the first technical solution for purging, with two modes: shutdown purging and pre-start purging. The specific steps of the shutdown purging mode are as follows: After receiving the shutdown signal, the programmable logic controller (PLC) executes the high-temperature purging step to maintain the waste tire pyrolysis reactor at a high temperature, stops feeding into the waste tire pyrolysis reactor, and opens the main circuit on / off valve to inject a large flow of nitrogen into the waste tire pyrolysis reactor and the condensation system to purge the residual oil and gas in the waste tire pyrolysis reactor to the condensation system for collection; then, a low-temperature purging step is performed to reduce the temperature of the waste tire pyrolysis reactor and continuously purge with a small flow of nitrogen to prevent air backflow. The specific steps for the pre-start purging mode are as follows: Before starting the waste tire pyrolysis reactor, check the airtightness of the waste tire pyrolysis reactor. After the airtightness meets the standard, the programmable logic controller opens the main circuit on / off valve and the pressure regulating valve to charge nitrogen into the waste tire pyrolysis reactor at a set flow rate. After the pressure of the waste tire pyrolysis reactor rises to the set value, stop the nitrogen charging and open the pressure relief valve to discharge the gas in the waste tire pyrolysis reactor to a safe area. Repeat the "pressurization-depressurization" replacement purging cycle. When the oxygen concentration analyzer detects that the oxygen concentration at the back end of the condensation system is lower than the set safety threshold within the set observation time, the purging process stops.

[0007] Furthermore, in the high-temperature purging step, the high-temperature stage of the waste tire pyrolysis reactor is above 300°C, and the flow rate of high-flow nitrogen is 200~250 m³ / h; in the low-temperature purging step, the flow rate of low-flow nitrogen is 50~100 m³ / h.

[0008] Furthermore, the "pressurization-depressurization" replacement purging process in the pre-start purging mode is repeated at least 3 times.

[0009] Furthermore, the observation time shall be no less than 3 minutes.

[0010] Furthermore, the safe threshold for oxygen concentration is no greater than 2%.

[0011] The beneficial effects of this invention are as follows: This invention uses a nitrogen source to purge inert gas into the waste tire pyrolysis reactor and condensation system, ensuring that the reaction system remains in a safe inert state before and after start-up and shutdown, preventing residual oil and gas and air contamination, and effectively preventing deflagration accidents. This invention sets different purging modes according to different purging times during the production process. Shutdown purging is used when production stops. At this time, depending on the state of the waste tire pyrolysis reactor, it is divided into high-temperature purging and low-temperature purging. In the high-temperature stage, a large amount of oil and gas exists in the reaction system, so a large flow of nitrogen is used for back-purging to quickly discharge the oil and gas in the waste tire pyrolysis reactor to the condensation system for collection. In the low-temperature stage, a small flow of nitrogen is used for purging to prevent air contamination. Backflow; the pre-start purging process involves a cyclical "pressurization-depressurization" replacement purging. The pressurization process fills the waste tire pyrolysis reactor with nitrogen, fully replacing the combustible gases inside. The depressurization process releases the gases from the reactor. This cycle is repeated to fully replace the combustible gases in the reactor. This invention changes the purging endpoint from the vague "time control" used in existing technologies to precise "quality control," namely "oxygen concentration control," ensuring that the purging effect can effectively meet the standards. The entire purging process is fully automated by a logic controller, avoiding human error: the entire start-up and shutdown purging process is automatically executed by the program without manual intervention, avoiding misoperation and omissions. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the control structure according to an embodiment of the present invention.

[0014] Explanation of reference numerals in the attached diagram: 1-Nitrogen source, 2-Main pipeline on / off valve, 3-Pressure regulating valve, 4-Flow meter, 5-Oxygen concentration analyzer, 6-Pressure gauge, 7-Programmable logic controller, 8-Pressure relief valve, 9-Waste tire pyrolysis reactor, 10-Buffer tank, 11-Condenser. Detailed Implementation

[0015] To better understand the above-described objects, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may be practiced in other ways different from those described herein, and therefore, the invention is not limited to the specific embodiments disclosed below.

[0016] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art described herein. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” etc., are used only to indicate relative positional relationships, which change accordingly when the absolute position of the described object changes.

[0017] like Figures 1-2 As shown, an intelligent nitrogen purging system for starting and stopping a waste tire pyrolysis process includes a nitrogen source 1, a main pipeline on / off valve 2, a pressure regulating valve 3, a flow meter 4, a pressure relief valve 8, a pressure gauge 6, an oxygen concentration analyzer 5, and a programmable logic controller 7.

[0018] The nitrogen source 1 and the main pipeline on / off valve 2 are located at the front end of the waste tire pyrolysis reactor 9. The nitrogen source 1 is connected to the main pipeline on / off valve 2, which is used to adjust the connection status between the waste tire pyrolysis reactor 9 and the nitrogen source 1 according to the control instructions of the programmable logic controller 7. The pressure regulating valve 3 is located after the nitrogen source 1 and the main pipeline on / off valve 2, and is used to regulate the nitrogen pressure entering the furnace. The flow meter 4 is located at the rear end of the pressure regulating valve 3, and is used to measure the nitrogen flow rate entering the furnace. The pressure relief valve 8 is located at the rear end of the waste tire pyrolysis reactor 9, and is used to relieve pressure on the waste tire pyrolysis reactor 9 according to the control instructions of the programmable logic controller 7. The pressure gauge 6 is located at the waste tire pyrolysis reactor 9 and the pressure relief valve 8. Between valves 8, pressure is detected in the waste tire pyrolysis reactor 9; oxygen concentration analyzer 5 is installed at the rear end of the condensation system to detect the oxygen concentration at the rear end of the condensation system and feed it back to programmable logic controller 7; programmable logic controller 7 is electrically connected to nitrogen source 1, main pipeline on / off valve 2, pressure regulating valve 3, flow meter 4, pressure relief valve 8, pressure gauge 6 and oxygen concentration analyzer 5, and is used to control the operation of nitrogen source 1 and main pipeline on / off valve 2 according to the data transmitted by flow meter 4, pressure gauge 6 and oxygen concentration analyzer 5; in this embodiment of the invention, programmable logic controller 7 includes PLC and distributed control system DSC, and the condensation system includes buffer tank 10 and condenser 11.

[0019] The purging method of this invention includes two modes: shutdown purging and pre-start purging. The specific steps of the shutdown purging mode are as follows: After receiving the shutdown signal, the programmable logic controller 7 executes the high-temperature purging step to maintain the waste tire pyrolysis reactor 9 at a high temperature, i.e., above 300°C; the feed into the waste tire pyrolysis reactor 9 is stopped, the programmable logic controller 7 opens the main circuit on / off valve, and injects a large flow of nitrogen gas at a flow rate of 200~250 m³ / h into the waste tire pyrolysis reactor 9 and the condensation system to purge the residual oil and gas in the waste tire pyrolysis reactor 9 to the condensation system for collection. The buffer tank 10 is used to precipitate the heavy components in the residual oil and gas, and the condenser 11 is used to precipitate the pyrolysis oil in the residual oil and gas through the circulating water coil; then the low-temperature purging step is performed to reduce the temperature of the waste tire pyrolysis reactor 9, and a small flow of nitrogen gas at a flow rate of 50~100 m³ / h is continuously purged to prevent air backflow.

[0020] The specific steps of the pre-start purging mode are as follows: Before starting the waste tire pyrolysis reactor 9, check the airtightness of the waste tire pyrolysis reactor 9. After the airtightness meets the standard, the programmable logic controller 7 opens the main circuit on / off valve and the pressure regulating valve 3 to charge nitrogen into the waste tire pyrolysis reactor 9 at a set flow rate; after the pressure of the waste tire pyrolysis reactor 9 rises to the set value, stop the nitrogen charging and open the pressure relief valve 8 to discharge the gas in the waste tire pyrolysis reactor 9 to a safe area; repeat the "pressurization-depression" replacement purging cycle at least 3 times. In this embodiment of the invention, nitrogen is charged into the waste tire pyrolysis reactor 9 at a flow rate of 50~100 m³ / h. After the pressure of the waste tire pyrolysis reactor 9 rises to 0.05 MPa, stop the nitrogen charging.

[0021] When the oxygen concentration analyzer 5 detects that the oxygen concentration at the downstream end of the condensation system is consistently below the set safety threshold within the set observation time, the purging process stops. In this embodiment of the invention, the observation time is no less than 3 minutes, and the safety threshold for oxygen concentration is no greater than 2%, ensuring that the purging effect fully meets the standards. During the purging process, the programmable logic controller 7 can automatically record changes in oxygen concentration, flow rate, pressure, and purging time, providing data support for safety audits and accident analysis.

[0022] In this embodiment of the invention, inert gas is purged into the waste tire pyrolysis reactor 9 and the condensation system via nitrogen source 1. This ensures that the reaction system remains in a safe inert state before and after start-up and shutdown, preventing residual oil and gas and air contamination, and effectively preventing deflagration accidents. This embodiment of the invention sets different purging modes according to different purging times during the production process. Shutdown purging is used when production stops. At this time, depending on the state of the waste tire pyrolysis reactor 9, it is divided into high-temperature purging and low-temperature purging. During the high-temperature stage, a large amount of oil and gas exists in the reaction system, so a high-flow-rate nitrogen is used for back-purging to quickly discharge the oil and gas in the waste tire pyrolysis reactor 9 to the condensation system for collection. During the low-temperature stage, a small-flow-rate nitrogen is used for purging to prevent air backflow. The pre-start purging process involves a cyclical "pressurization-depressurization" replacement purging. The pressurization process fills the waste tire pyrolysis reactor 9 with nitrogen, fully replacing the combustible gas inside. The depressurization process releases the gas from the reactor 9. This cycle is repeated to fully replace the combustible gas inside the reactor 9. This embodiment of the invention changes the purging endpoint from the vague "time control" used in the prior art to precise "quality control," namely "oxygen concentration control," ensuring that the purging effect can effectively meet the standards. The entire purging process is fully automated by a logic controller, avoiding human error: the entire start-up and shutdown purging process is automatically executed by the program without manual intervention, avoiding misoperation and omissions.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An intelligent nitrogen purging system for starting and stopping a waste tire pyrolysis process, characterized in that, Includes nitrogen source, main pipeline on / off valve, pressure regulating valve, flow meter, pressure relief valve, pressure gauge, oxygen concentration analyzer and programmable logic controller; The nitrogen source and main pipeline on / off valve are located at the front end of the waste tire pyrolysis reactor. The nitrogen source is connected to the main pipeline on / off valve, which is used to adjust the connection status between the waste tire pyrolysis reactor and the nitrogen source according to the control instructions of the programmable logic controller (PLC). The pressure regulating valve is located after the nitrogen source and the main pipeline on / off valve to regulate the nitrogen pressure entering the furnace. The flow meter is located after the pressure regulating valve to measure the nitrogen flow rate entering the furnace. The pressure relief valve is located after the waste tire pyrolysis reactor to relieve pressure on the waste tire pyrolysis reactor according to the control instructions of the PLC. The pressure gauge is located between the waste tire pyrolysis reactor and the pressure relief valve to detect the pressure of the waste tire pyrolysis reactor. The oxygen concentration analyzer is located after the condensation system to detect the oxygen concentration at the condensation system and feed it back to the PLC. The PLC is electrically connected to the nitrogen source, the main pipeline on / off valve, the pressure regulating valve, the flow meter, the pressure relief valve, the pressure gauge, and the oxygen concentration analyzer, and controls the operation of the nitrogen source and the main pipeline on / off valve based on the data transmitted by the flow meter, the pressure gauge, and the oxygen concentration analyzer.

2. The intelligent nitrogen purging system for starting and stopping a waste tire pyrolysis process according to claim 1, characterized in that, The programmable logic controller includes a PLC and a distributed control system (DSC).

3. A smart nitrogen purging method for starting and stopping a waste tire pyrolysis process, characterized in that, The intelligent nitrogen purging system for starting and stopping the waste tire pyrolysis process as described in any one of claims 1 to 2 is used for purging, with two modes: purging during shutdown and purging before startup. The specific steps of the shutdown purging mode are as follows: After receiving the shutdown signal, the programmable logic controller (PLC) executes the high-temperature purging step to maintain the waste tire pyrolysis reactor at a high temperature, stops feeding into the waste tire pyrolysis reactor, and opens the main circuit on / off valve to inject a large flow of nitrogen into the waste tire pyrolysis reactor and the condensation system to purge the residual oil and gas in the waste tire pyrolysis reactor to the condensation system for collection; then, a low-temperature purging step is performed to reduce the temperature of the waste tire pyrolysis reactor and continuously purge with a small flow of nitrogen to prevent air backflow. The specific steps for the pre-start purging mode are as follows: Before starting the waste tire pyrolysis reactor, check the airtightness of the waste tire pyrolysis reactor. After the airtightness meets the standard, the programmable logic controller opens the main circuit on / off valve and the pressure regulating valve to charge nitrogen into the waste tire pyrolysis reactor at a set flow rate. After the pressure of the waste tire pyrolysis reactor rises to the set value, stop the nitrogen charging and open the pressure relief valve to discharge the gas in the waste tire pyrolysis reactor to a safe area. Repeat the "pressurization-depressurization" replacement purging cycle. When the oxygen concentration analyzer detects that the oxygen concentration at the back end of the condensation system is lower than the set safety threshold within the set observation time, the purging process stops.

4. The intelligent nitrogen purging method for starting and stopping a waste tire pyrolysis process according to claim 3, characterized in that, In the high-temperature purging step, the high-temperature stage of the waste tire pyrolysis reactor is above 300°C, and the flow rate of high-flow nitrogen is 200~250 m³ / h; in the low-temperature purging step, the flow rate of low-flow nitrogen is 50~100 m³ / h.

5. The intelligent nitrogen purging method for starting and stopping a waste tire pyrolysis process according to claim 3, characterized in that, The "pressurization-depressurization" replacement purging process in the pre-start purging mode should be repeated at least 3 times.

6. The intelligent nitrogen purging method for starting and stopping a waste tire pyrolysis process according to claim 3, characterized in that, The observation time shall not be less than 3 minutes.

7. The intelligent nitrogen purging method for starting and stopping a waste tire pyrolysis process according to claim 3, characterized in that, The safe threshold for oxygen concentration is no greater than 2%.

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