Heat supply system with standby steam header and working method of heat supply system

Abstract

The invention relates to a heat supply system with a standby steam header and a working method of the heat supply system. The system comprises a unit, a first-stage steam header group, a second-stage steam header group and a control mechanism, the unit is used for supplying steam to the first-stage steam-distributing cylinder group, the input end of the first-stage steam-distributing cylinder group is communicated with the unit, and a heat supply main door is arranged between each first-stage steam-distributing cylinder and the unit; the first-stage steam-distributing cylinder group comprises a first first-stage steam-distributing cylinder and a second first-stage steam-distributing cylinder, the first first-stage steam-distributing cylinder is communicated with the second first-stage steam-distributing cylinder through a valve, and the first first-stage steam-distributing cylinder and the second first-stage steam-distributing cylinder are respectively provided with passages communicated with the second-stage steam-distributing cylinder group, so that the first first-stage steam-distributing cylinder and the The input end of the second-stage steam-distributing cylinder group is communicated with the first-stage steam-distributing cylinder group, and the output end is communicated with an area needing heat supply; the control mechanism comprises a heat supply main door electric execution module and a PLC control module and is used for controlling opening and closing of a heat supply main door between each primary branch air cylinder and the unit according to an instruction of a worker. Compared with the prior art, the method has the advantages of high flexibility, high stability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of heating, and in particular to a heating system with a spare sub-cylinder and a working method thereof. Background Art

[0002] In the prior art, the stability and flexibility of the heating system are insufficient, especially there is no spare sub-cylinder for standby during maintenance, which to a certain extent limits the normal operation and maintenance of the heating system.

[0003] In the prior art, as shown in reference patents CN116517651A and CN106894855A, although automatic control methods and thermoelectric decoupling transformation and operation methods for the heating transformation of coal-fired power generation units have been proposed, which effectively improved the safety and efficiency of the unit operation, these technical solutions did not solve the problem of heating interruption during cylinder maintenance, nor did they provide a manually switchable spare cylinder system to ensure the continuity of heating during maintenance.

[0004] In summary, the current heating system generally has problems such as instability, easy interruption of heating during maintenance, and lack of flexibility. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a heating system with a spare cylinder and a working method thereof.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a heating system with spare sub-cylinders is provided, the system comprising a unit 1, a primary sub-cylinder group 2, a secondary sub-cylinder group 3 and a control mechanism 4;

[0008] Unit 1 is used to supply steam to the first-stage cylinder group 2. The input end of the first-stage cylinder group 2 is connected to unit 1. A main heating door is provided between each first-stage cylinder and unit 1.

[0009] The first-stage cylinder group 2 includes at least a first-stage cylinder 21 and a second-stage cylinder 22. The first-stage cylinder 21 and the second-stage cylinder 22 are connected via a valve, and the first-stage cylinder 21 and the second-stage cylinder 22 are respectively equipped with a passage connected to the second-stage cylinder group 3, thereby serving as a backup for each other.

[0010] The input end of the secondary cylinder group 3 is connected to the primary cylinder group 2, and the output end is connected to the required heating area;

[0011] The control mechanism 4 includes an electric execution module for the main heating door and a PLC control module, which are used to control the opening and closing of the main heating door between each primary cylinder and the unit 1.

[0012] As a preferred technical solution, in the first-stage sub-cylinder group 2, the output ends of the first first-stage sub-cylinder 21 and the second first-stage sub-cylinder 22 are each equipped with at least one main heating door.

[0013] As an optimal technical solution, all valves at the output end of the first-stage steam cylinder 21 are electric valves, and the electric valves integrate an opening feedback module and a pressure difference adaptive adjustment program; the opening feedback module transmits the valve opening data to the PLC control module in real time, and the pressure difference adaptive adjustment program automatically adjusts the valve opening according to the steam pressure difference before and after the valve to maintain stable steam delivery flow.

[0014] As an optimal technical solution, all valves at the output end of the second-level cylinder 22 are manual valves and are equipped with a local manual control interface and a remote electric control interface; the local manual control interface supports on-site emergency operations by operation and maintenance personnel, and the remote electric control interface is connected to the PLC control module to meet the valve opening adjustment requirements under the automatic control process, and when switching between manual / electric modes, the non-activated control channel is automatically locked to prevent command conflicts.

[0015] As a preferred technical solution, the first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 of the first-stage sub-cylinder group 2 are both equipped with steam parameter monitoring modules, including temperature sensors, pressure sensors and liquid level sensors. The monitoring data are uploaded to the PLC control module in real time for abnormal operating condition warning and adaptive adjustment of control strategies.

[0016] As a preferred technical solution, the connecting pipes between the first and second first-stage sub-cylinders 21 and 22, as well as the connecting pipes between the first-stage sub-cylinder group 2 and the second-stage sub-cylinder group 3, are all covered with a thermal insulation layer and a temperature-compensating expansion joint.

[0017] According to another aspect of the present invention, a working method of a heating system with spare sub-cylinders is provided. During normal heating, the unit 1 supplies steam to the first-level sub-cylinder group 2, and then the first-level sub-cylinder group 2 supplies steam to the second-level sub-cylinder group 3. The sub-cylinders in the second-level sub-cylinder group 3 are connected for operation, and finally the second-level sub-cylinder group 3 supplies heat to the required heating area; during maintenance, the first-level sub-cylinder 21 and the second-level sub-cylinder 22 in the first-level sub-cylinder group 2 serve as spare for each other.

[0018] As a preferred technical solution, each sub-cylinder in the first-level sub-cylinder group 2 includes two working modes during normal heating: independent operation or communication operation. In the independent operation mode, only the main heating door between the corresponding first-level sub-cylinder and the unit 1 is opened; in the communication operation mode, the main heating doors between all first-level sub-cylinders and the unit 1 are opened.

[0019] As a preferred technical solution, during maintenance, the first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 of the first-stage sub-cylinder group 2 are switched for use according to the situation. The specific control method includes:

[0020] When the first-stage sub-cylinder 21 needs to be isolated for maintenance, the main heating door from the unit 1 to the second-stage sub-cylinder 22 is opened, and the main heating door from the unit 1 to the first-stage sub-cylinder 21 is closed, thereby supplying steam to the second-stage sub-cylinder 22, and then from the second-stage sub-cylinder 22 to the second-stage sub-cylinder group 3;

[0021] When the second-level sub-cylinder 22 needs to be isolated for maintenance, the main heating door from the unit 1 to the first-level sub-cylinder 21 is opened, and the main heating door from the unit 1 to the second-level sub-cylinder 22 is closed, so that steam is supplied to the first-level sub-cylinder 21, and then from the first-level sub-cylinder 21 to the second-level sub-cylinder group 3.

[0022] As a preferred technical solution, when the first-level sub-cylinder 21 and the second-level sub-cylinder 22 are switched, the electric execution module of the heating main door and the PLC control module work together to automatically switch. After the PLC control module receives the sub-cylinder maintenance or switching instruction, it first triggers the electric execution module of the heating main door to be closed according to the preset timing to perform the closing action. After the electric execution module of the heating main door feeds back a closing signal to it, it triggers the electric execution module of the heating main door to be opened to perform the opening action.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention adopts the design of "the first and second first-stage sub-cylinders are interconnected and serve as backup for each other" in the first-stage sub-cylinder group, and cooperates with the automatic control of the control mechanism to solve the problem of interrupting heating during maintenance of the traditional single-stage sub-cylinder system, thereby achieving heating continuity; at the same time, the hierarchical sub-cylinder structure improves the flexibility of steam distribution and adapts to the differentiated needs of different heating areas.

[0025] 2. In the present invention, each first-stage steam cylinder output end is equipped with at least one main heating gate to form "multi-path redundancy", which can flexibly distribute steam according to the load changes of the second-stage steam cylinder group, avoid local heating interruption caused by single valve failure, and enhance the system's risk resistance.

[0026] 3. In the present invention, the first-stage steam cylinder is equipped with intelligent adjustment of electric valves, feedback of electric valve opening and adaptive adjustment of pressure difference, so that it can respond to steam pressure fluctuations in real time, automatically maintain flow stability, and reduce manual intervention; the real-time data interaction of the PLC control module realizes precise and intelligent control of steam transportation, reduces thermal loss, and each valve at the output end of the second-stage steam cylinder is a manual valve, and is equipped with a local manual control interface and a remote electric control interface, so that it has both local emergency operation and remote control functions; when the mode is switched, the non-activated channel is automatically locked to completely avoid command conflicts and ensure operation and maintenance safety.

[0027] 4. In the present invention, steam parameter monitoring modules are configured on both the first-stage sub-cylinder and the second-stage sub-cylinder. Real-time monitoring and uploading of parameters such as temperature, pressure, and liquid level enable the PLC control module to quickly identify abnormal operating conditions and issue early warnings. At the same time, it provides data support for control strategy adjustments, preventing equipment damage or heating accidents from the source and improving system safety.

[0028] 6. The connecting pipeline in the present invention is coated with a thermal insulation layer and a temperature-compensating expansion joint. The thermal insulation layer reduces heat loss, and the temperature-compensating expansion joint absorbs the deformation of the pipeline caused by temperature changes, thereby avoiding damage caused by stress concentration in the pipeline.

[0029] 7. In the present invention, the graded steam supply under normal working conditions realizes efficient steam distribution. During maintenance, the first-level sub-cylinders serve as backup for each other, ensuring that the heat supply is not interrupted during maintenance, and balancing the system operation efficiency and operation and maintenance convenience. By clarifying the sub-cylinder maintenance switching control method, it is ensured that the steam transmission path is seamlessly connected during maintenance, avoiding heat supply interruption or pressure fluctuation caused by operational errors, simplifying the operation and maintenance process, and improving maintenance safety; and the control mechanism automatically executes switching according to the preset timing, ensures that the action is in place through signal feedback, replaces manual operation, reduces switching time and the risk of misoperation, and realizes standardization and automation of sub-cylinder switching.

[0030] 8. In the present invention, each sub-cylinder has two working modes during normal heating: independent operation and communication operation. The independent operation mode can save energy and reduce consumption in low-load scenarios, and the communication operation mode can centrally distribute steam to meet high-load demands. The two modes can be flexibly switched, which not only improves the load adaptability of the system, but also reduces unnecessary energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of a heating system with a spare steam cylinder in the present invention;

[0032] Figure 2 This is a schematic structural diagram of a heating system with a spare steam cylinder in an embodiment;

[0033] In the figure, 1 is the unit, 2 is the first-stage sub-cylinder group, 21 is the first-stage sub-cylinder, 22 is the second-stage sub-cylinder, 3 is the second-stage sub-cylinder group, and 4 is the control mechanism. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0035] Example 1

[0036] In this embodiment, a heating system with a spare cylinder is used. Figure 1 As shown, it includes a unit 1, a first-stage cylinder group 2, a second-stage cylinder group 3 and a control mechanism 4;

[0037] Unit 1 is used to supply steam to the first-stage cylinder group 2. The input end of the first-stage cylinder group 2 is connected to unit 1. A main heating door is provided between each first-stage cylinder and unit 1.

[0038] The first-stage cylinder group 2 includes at least a first-stage cylinder 21 and a second-stage cylinder 22. The first-stage cylinder 21 and the second-stage cylinder 22 are connected via a valve, and the first-stage cylinder 21 and the second-stage cylinder 22 are respectively equipped with a passage connected to the second-stage cylinder group 3, thereby serving as a backup for each other.

[0039] The input end of the secondary cylinder group 3 is connected to the primary cylinder group 2, and the output end is connected to the required heating area;

[0040] The control mechanism 4 includes an electric execution module for the main heating door and a PLC control module, which is used to control the opening and closing of the main heating door between each first-level cylinder and the unit 1 according to the instructions of the staff.

[0041] In the primary sub-cylinder group 2, the output ends of the first primary sub-cylinder 21 and the second primary sub-cylinder 22 are each equipped with at least one main heating door.

[0042] Each valve at the output end of the first-stage steam cylinder 21 is an electric valve, and the electric valve integrates an opening feedback module and a pressure difference adaptive adjustment program; the opening feedback module transmits the valve opening data to the PLC control module in real time, and the pressure difference adaptive adjustment program automatically adjusts the valve opening according to the steam pressure difference before and after the valve to maintain stable steam delivery flow.

[0043] All valves at the output end of the second-stage sub-cylinder 22 are manual valves and are equipped with a local manual control interface and a remote electric control interface; the local manual control interface supports on-site emergency operations by operation and maintenance personnel, and the remote electric control interface is connected to the PLC control module to meet the valve opening adjustment requirements under the automatic control process, and when switching between manual / electric modes, the inactive control channel is automatically locked to prevent command conflicts.

[0044] The first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 of the first-stage sub-cylinder group 2 are both equipped with steam parameter monitoring modules, including temperature sensors, pressure sensors and liquid level sensors (if applicable). The monitoring data are uploaded to the PLC control module in real time for abnormal operating condition warning and adaptive adjustment of control strategies.

[0045] The connecting pipes between the first-stage sub-cylinder 21 and the second-stage sub-cylinder 22, as well as the connecting pipes between the first-stage sub-cylinder group 2 and the second-stage sub-cylinder group 3, are all covered with a heat insulation layer and a temperature compensation expansion joint.

[0046] A large industrial park needs to provide a stable steam heat source for multiple businesses. In this heating system, unit 1 uses a steam boiler with a rated steam supply of 200 t / h. Both the first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 have a diameter of 3 meters and a length of 8 meters, a design pressure of 2.5 MPa, and a maximum temperature tolerance of 350°C.

[0047] During normal heating, the system operates in interconnected mode. The PLC control module opens the main heating valve between all first-stage sub-cylinders and unit 1. Steam generated by unit 1 enters both the first and second-stage sub-cylinders 21 and 22, and is then distributed to various enterprises within the park via the second-stage sub-cylinder group 3. At this point, the electric valve at the output end of the first-stage sub-cylinder 21 utilizes an opening feedback module and a pressure differential adaptive regulation program to dynamically adjust its opening based on the steam demand of each enterprise, maintaining a stable steam flow rate.

[0048] When the first-level steam cylinder 21 requires maintenance, the operator issues a maintenance command through the control mechanism 4. After receiving the command, the PLC control module triggers the electric actuator module of the heating main door from unit 1 to the first-level steam cylinder 21 to execute the closing action according to the preset timing. After receiving the closing signal, the electric actuator module of the heating main door from unit 1 to the second-level steam cylinder 22 is triggered to open, switching all steam supply to the second-level steam cylinder 22 to ensure uninterrupted heating for enterprises in the park. During the maintenance period, the manual valve at the output end of the second-level steam cylinder 22 is switched to remote electric control mode, which is uniformly adjusted by the PLC control module to ensure stable heating.

[0049] Example 2

[0050] In this embodiment, a working method of a heating system with spare sub-cylinders is adopted. This method applies a heating system with spare sub-cylinders as in Example 1. During normal heating, unit 1 supplies steam to the first-level sub-cylinder group 2, and then the first-level sub-cylinder group 2 supplies steam to the second-level sub-cylinder group 3. The sub-cylinders in the second-level sub-cylinder group 3 are connected for operation, and finally the second-level sub-cylinder group 3 supplies heat to the required heating area; during maintenance, the first-level sub-cylinder 21 and the second-level sub-cylinder 22 in the first-level sub-cylinder group 2 serve as spare for each other.

[0051] In this embodiment, the system used is as follows Figure 2 shown.

[0052] When each sub-cylinder in the first-level sub-cylinder group 2 is normally supplying heat, it includes two working modes: independent operation or communication operation. In the independent operation mode, only the main heating door between the corresponding first-level sub-cylinder and unit 1 is opened; in the communication operation mode, the main heating doors between all first-level sub-cylinders and unit 1 are opened.

[0053] During maintenance, the first stage cylinder 21 and the second stage cylinder 22 of the first stage cylinder group 2 are switched for use according to the situation. The specific control method includes:

[0054] When the first-stage sub-cylinder 21 needs to be isolated for maintenance, the main heating door from the unit 1 to the second-stage sub-cylinder 22 is opened, and the main heating door from the unit 1 to the first-stage sub-cylinder 21 is closed, thereby supplying steam to the second-stage sub-cylinder 22, and then from the second-stage sub-cylinder 22 to the second-stage sub-cylinder group 3;

[0055] When the second-level sub-cylinder 22 needs to be isolated for maintenance, the main heating door from the unit 1 to the first-level sub-cylinder 21 is opened, and the main heating door from the unit 1 to the second-level sub-cylinder 22 is closed, so that steam is supplied to the first-level sub-cylinder 21, and then from the first-level sub-cylinder 21 to the second-level sub-cylinder group 3.

[0056] When the first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 are switched, the electric execution module of the heating main door and the PLC control module work together to automatically switch. After the PLC control module receives the sub-cylinder maintenance or switching instruction, it first triggers the electric execution module of the heating main door to be closed according to the preset timing to perform the closing action. After the electric execution module of the heating main door feeds back a closing position signal to it, it triggers the electric execution module of the heating main door to be opened to perform the opening action.

[0057] In this embodiment, this solution is applied to a city's centralized heating project. Unit 1 uses a back-pressure steam turbine with a rated steam supply of 150 t / h. The first-stage sub-cylinder 21 and the second-stage sub-cylinder 22 have a diameter of 2.5 meters and a length of 7 meters, a design pressure of 1.6 MPa, and a maximum temperature tolerance of 280°C.

[0058] During the initial heating period, when demand for heat in some areas is low, the system operates in standalone mode, opening only the main heating valve between the first-stage sub-cylinder 21 and unit 1. This allows steam to be supplied from the first-stage sub-cylinder 21 to the second-stage sub-cylinder group 3. The electric valve at the output of the first-stage sub-cylinder 21 automatically adjusts its opening based on heat load feedback from each heating zone through a pressure differential adaptive regulation program, ensuring precise heating.

[0059] During operation, the pressure sensor of the second-level sub-cylinder 22 detects abnormal fluctuations in internal pressure, and the PLC control module immediately issues an early warning and automatically switches the first-level sub-cylinder 21 to the main steam supply equipment. At the same time, the second-level sub-cylinder 22 and the main heating door of the unit 1 are closed, and the maintenance process is started. Since the connecting pipeline between the first-level sub-cylinder 21 and the second-level sub-cylinder 22 is covered with a thermal insulation layer and a temperature-compensating expansion joint, heat loss and pipeline stress are effectively reduced during the switching process, ensuring stable operation of the system. After the fault is eliminated, the second-level sub-cylinder 22 is reconnected to the system through the control mechanism 4 to resume normal heating.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A heating system with a spare cylinder, characterized in that: The system includes a unit (1), a first-stage cylinder group (2), a second-stage cylinder group (3) and a control mechanism (4); The unit (1) is used to supply steam to the first-stage cylinder group (2), the input end of the first-stage cylinder group (2) is connected to the unit (1), and a main heating door is provided between each first-stage cylinder and the unit (1); The first-stage cylinder group (2) comprises at least a first-stage cylinder (21) and a second-stage cylinder (22), the first-stage cylinder (21) and the second-stage cylinder (22) being connected via a valve, and the first-stage cylinder (21) and the second-stage cylinder (22) are each provided with a passage connected to the second-stage cylinder group (3), thereby serving as a backup for each other; The input end of the secondary cylinder group (3) is connected to the primary cylinder group (2), and the output end is connected to the required heating area; The control mechanism (4) comprises a heating main door electric execution module and a PLC control module, which are used to control the opening and closing of the heating main door between each primary cylinder and the unit (1).

2. A heating system with a spare cylinder according to claim 1, characterized in that: In the one-stage sub-cylinder group (2), the output ends of the first one-stage sub-cylinder (21) and the second one-stage sub-cylinder (22) are each equipped with at least one main heating door.

3. The heating system with a spare cylinder according to claim 1, characterized in that: Each valve at the output end of the first-stage steam cylinder (21) is an electric valve, and the electric valve integrates an opening feedback module and a pressure difference adaptive adjustment program; the opening feedback module transmits valve opening data to the PLC control module in real time, and the pressure difference adaptive adjustment program automatically adjusts the valve opening according to the steam pressure difference before and after the valve to maintain the stability of the steam delivery flow.

4. The heating system with a spare cylinder according to claim 1, characterized in that: Each valve at the output end of the second-stage steam cylinder (22) is a manual valve and is equipped with a local manual control interface and a remote electric control interface; the local manual control interface supports on-site emergency operations by operation and maintenance personnel, and the remote electric control interface is connected to the PLC control module to meet the valve opening adjustment requirements under the automatic control process, and when the manual / electric mode is switched, the inactive control channel is automatically locked to prevent command conflicts.

5. The heating system with a spare cylinder according to claim 1, characterized in that: The first-stage sub-cylinder (21) and the second-stage sub-cylinder (22) of the first-stage sub-cylinder group (2) are both equipped with a steam parameter monitoring module, including a temperature sensor, a pressure sensor and a liquid level sensor. The monitoring data is uploaded to the PLC control module in real time for abnormal working condition warning and adaptive adjustment of the control strategy.

6. The heating system with a spare cylinder according to claim 1, characterized in that: The connecting pipes between the first-stage sub-cylinder (21) and the second-stage sub-cylinder (22), as well as the connecting pipes between the first-stage sub-cylinder group (2) and the second-stage sub-cylinder group (3), are all covered with a heat insulation layer and a temperature compensation expansion joint.

7. A method for operating a heating system with a spare cylinder, characterized in that: The method is applied to a heating system with spare sub-cylinders as described in any one of claims 1 to 6. During normal heating, the unit (1) supplies steam to the first-level sub-cylinder group (2), and then the first-level sub-cylinder group (2) supplies steam to the second-level sub-cylinder group (3). The sub-cylinders in the second-level sub-cylinder group (3) are connected for operation, and finally the second-level sub-cylinder group (3) supplies heat to the required heating area; during maintenance, the first-level sub-cylinder (21) and the second-level sub-cylinder (22) in the first-level sub-cylinder group (2) serve as spare for each other.

8. The operating method of a heating system with a spare cylinder according to claim 1, characterized in that: Each sub-cylinder in the first-stage sub-cylinder group (2) has two working modes during normal heating: individual operation and communication operation. In the individual operation mode, only the main heating door between the corresponding first-stage sub-cylinder and the unit (1) is opened; in the communication operation mode, the main heating doors between all first-stage sub-cylinders and the unit (1) are opened.

9. The operating method of a heating system with a spare cylinder according to claim 1, characterized in that: During the maintenance, the first stage cylinder (21) and the second stage cylinder (22) of the first stage cylinder group (2) are switched for use according to the situation. The specific control method includes: When the first-stage steam cylinder (21) needs to be isolated for maintenance, the main heating door from the unit (1) to the second-stage steam cylinder (22) is opened, and the main heating door from the unit (1) to the first-stage steam cylinder (21) is closed, thereby supplying steam to the second-stage steam cylinder (22), and then the second-stage steam cylinder (22) supplies steam to the second-stage steam cylinder group (3); When the second-stage sub-cylinder (22) needs to be isolated for maintenance, the main heating door from the unit (1) to the first-stage sub-cylinder (21) is opened, and the main heating door from the unit (1) to the second-stage sub-cylinder (22) is closed, thereby supplying steam to the first-stage sub-cylinder (21), and then from the first-stage sub-cylinder (21) to the second-stage sub-cylinder group (3).

10. The operating method of a heating system with a spare cylinder according to claim 1, characterized in that: When the first-stage sub-cylinder (21) and the second-stage sub-cylinder (22) are switched, the electric execution module of the heating main door and the PLC control module work together to automatically switch. After the PLC control module receives the sub-cylinder maintenance or switching instruction, it first triggers the electric execution module of the heating main door to be closed according to a preset timing to perform the closing action. After the electric execution module of the heating main door feeds back a closing position signal to it, it triggers the electric execution module of the heating main door to be opened to perform the opening action.

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