A precise aeration system and control method for a sludge film composite MBBR

Abstract

The application discloses a precise aeration system and control method of sludge-membrane composite MBBR, and relates to the technical field of sewage treatment. The system comprises a sludge-membrane composite MBBR biochemical tank, a forced aeration system, an online instrument monitoring system, an upper computer and a field PLC control system. The sludge-membrane composite MBBR biochemical tank is divided into an aerobic zone I, an aerobic MBBR zone and an aerobic zone II along the water flow direction. The forced aeration system comprises a micro-porous aeration blower and a perforated pipe aeration blower. The micro-porous aeration blower is connected with a first main pipeline, the first main pipeline is connected with a first branch pipeline and a second branch pipeline, and the perforated pipe aeration blower is connected with a second main pipeline. The control method adopts a constant air volume control strategy in the aerobic zone I, adopts a constant dissolved oxygen control strategy in the aerobic zone II, and realizes dynamic dissolved oxygen control in the aerobic MBBR zone based on feedforward in the aerobic zone I and feedback in the aerobic zone II, so that the control accuracy is greatly improved, and the maintenance cost is low.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a precise aeration system and control method for a mud-film composite MBBR. Background Technology

[0002] The MBBR process was first applied in Northern Europe, solving the problems of large footprint and poor low-temperature tolerance of traditional activated sludge processes. Its microorganisms mainly attach to suspended carriers, without sludge return or enrichment of suspended sludge. Essentially, it is a continuous flow, moving bed, biofilm biochemical treatment technology, representing a further upgrade of fluidized bed biofilm technology. In 2008, a wastewater treatment plant in my country, the first to undergo a Class A upgrade, successfully enhanced biological treatment by adding suspended carriers to its activated sludge system. This system is similar to MBBR in terms of equipment, but the main biological system remains activated sludge, with the suspended carrier biofilm used to enhance nitrification; it is essentially an activated sludge-biofilm composite system. To distinguish between the two types of processes, MBBR is used as a general term for technologies employing suspended carriers. Based on the form of the microorganisms, it is divided into sludge-film composite MBBR and pure membrane MBBR processes.

[0003] The mud-film composite process is essentially still the activated sludge process, and can be seen as a biofilm modification of the activated sludge process: the biofilm carrier is held in the reaction tank to form a composite system in which activated sludge and biofilm coexist. It is widely used in the upgrading and renovation of municipal wastewater treatment plants.

[0004] Currently, regarding aeration control, there are several issues: First, most models used in activated sludge processes rely on the ASM model from the International Water Association, but there is no mature, readily available model for the sludge-film composite MBBR process. Second, the sludge-film composite MBBR involves two aeration systems: a microporous aeration system and a perforated aeration system. These systems have different functions; microporous aeration primarily supplies oxygen, while perforated aeration mainly assists in carrier fluidization. Achieving a beneficial combination of these two systems without conflict requires careful consideration. Third, current practical aeration control applications also present numerous problems, such as discrepancies between the sum of the air flow meter branch pipe values ​​and the main pipe values, and uneven water and air distribution between the two biological tanks. These issues affect the implementation effectiveness. Fourth, some current aeration control systems on the market rely on numerous instruments and expensive valves, resulting in high hardware investment and unclear economic benefits. It is necessary to reduce hardware investment.

[0005] Considering the above-mentioned problems and the unique characteristics of the mud-film composite MBBR process, it is essential to develop an intelligent aeration control system that conforms to the mud-film composite MBBR process. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the first objective of the present invention is to provide a precise aeration system of mud film composite MBBR.

[0007] The present invention adopts the following technical solution:

[0008] A precision aeration system for a mud-film composite MBBR includes a mud-film composite MBBR biological tank, a blower aeration system, an online instrument monitoring system, a host computer and a field PLC control system;

[0009] The mud-film composite MBBR biological tank is divided into three aerobic zones: aerobic zone 1, aerobic MBBR zone, and aerobic zone 2 along the water flow direction. The aerobic MBBR zone is equipped with microporous aeration devices, suspended carriers, perforated pipe aeration devices, and interception devices.

[0010] The aeration system includes a microporous aeration blower and a perforated pipe aeration blower. The microporous aeration blower is connected to a first main pipe, and a first branch pipe and a second branch pipe are connected to the first main pipe. The perforated pipe aeration blower is connected to a second main pipe. The first main pipe is connected to the microporous aeration device, the first branch pipe is connected to aerobic zone one, and the second branch pipe is connected to aerobic zone two. Electric regulating valves and thermal gas flow meters are installed on both the first branch pipe and the second branch pipe. The second main pipe is connected to the perforated pipe aeration device.

[0011] The online instrument monitoring system includes online dissolved oxygen analyzers installed in the aerobic zone 1, the aerobic MBBR zone, and the end of the aerobic zone 2; and an online ammonia nitrogen analyzer installed at the end of the aerobic zone 2.

[0012] The host computer has a built-in aeration system control module;

[0013] The host computer communicates with the field PLC control system, and the field PLC control system is electrically connected to the microporous aerator, perforated pipe aerator, thermal gas flow meter, electric regulating valve, online dissolved oxygen analyzer, and online ammonia nitrogen analyzer.

[0014] Preferably, the volume of the aerobic MBBR zone accounts for at least 50% of the volume of the mud-film composite MBBR biological treatment tank.

[0015] Preferably, in the aerobic MBBR zone, the perforated tube aeration device is positioned above the microporous aeration device.

[0016] The second objective of this invention is to provide a control method for a precise aeration system of a mud-film composite MBBR.

[0017] A control method for a precision aeration system of a mud-film composite MBBR, employing the precision aeration system of a mud-film composite MBBR as described above, includes the following steps:

[0018] Step 1: In the aeration system control module, the aerobic zone 1 adopts a constant air volume control strategy, and the target value of the constant air volume is set to Q. 1t The on-site PLC control system controls the electric regulating valve on the first pipeline to make the gas flow rate in the first pipeline Q. 1t ;

[0019] Step 2: The aerobic zone 2 in the aeration system control module adopts a constant dissolved oxygen (DO) control strategy, with the target DO value set at DO. 2t The on-site PLC control system controls the gas flow in the second branch pipeline by controlling the electric regulating valve on the second branch pipeline, thereby ensuring that the dissolved oxygen in the aerobic zone is DO. 2t ;

[0020] Step 3: In the aerobic MBBR zone of the aeration system control module, a dynamic dissolved oxygen control strategy is adopted, and the initial dynamic dissolved oxygen target value of the aerobic MBBR zone is set to DO. m Every time interval T, a new dynamic target value of dissolved oxygen (DO) is calculated. mT The calculation formula is: DO mT =DO m +K 前 +K 后 After that, DO m =DO mT Among them, K 前 K is the feedforward correction factor, calculated from the dissolved oxygen value in the aerobic zone 1. 后 This is the feedback correction factor, calculated from the ammonia nitrogen value of the effluent from the aerobic zone 2.

[0021] Preferably, the constant dissolved oxygen target value (DO) in the aerobic zone II is... 2t The initial dynamic dissolved oxygen target value DO in the aerobic MBBR zone m same.

[0022] Preferably, the feedforward correction coefficient K 前 The calculation process is as follows:

[0023] Dissolved oxygen values ​​are collected from the online dissolved oxygen analyzer in aerobic zone 1 at intervals T. The dissolved oxygen value collected in aerobic zone 1 after the previous interval T is DO. 1T The dissolved oxygen value (DO) collected after the next time interval T in the aerobic zone 1 is DO. 1(T+1) When -m≤DO 1(T+1) -DO 1T When ≤m, K 前 =0; when m < DO 1(T+1) -DO 1T When ≤2m, K 前 =-a; when DO 1(T+1) -DO 1T When K > 2m前 =-2a; when -2m≤DO 1(T+1) -DO 1T When <-m, K 前 =a; when DO 1(T+1) -DO 1T When K < -2m 前 =2a; where m is a fixed positive value and a is a fixed positive value.

[0024] Preferably, the feedback correction coefficient K 后 The calculation process is as follows:

[0025] The target value for ammonia nitrogen in the effluent from the aerobic zone II is set to NH3-N. t At each time interval T, the actual ammonia nitrogen value of the effluent from the online ammonia nitrogen analyzer in the aerobic zone II was collected as NH3-N. a When -m≤NH3-N a -NH3-N t When ≤m, K 后 =0; when m < NH3-N a -NH3-N t When ≤2m, K 后 =b; when NH3-N a -NH3-N t When K > 2m 后 =2b; when -2m≤NH3-N a -NH3-N t When <-m, K 后 =-b; when NH3-N a -NH3-N t <-2m, K 后 = -2b; where m is a fixed positive value and b is a fixed positive value.

[0026] Preferably, in step 2, the dissolved oxygen in the aerobic zone 2 is DO. 2t The specific process is as follows:

[0027] At intervals T, the dissolved oxygen value (DO) of the online dissolved oxygen analyzer in the aerobic zone 2 was collected. 2a , when |DO 2a -DO 2t When | ≤ n, the on-site PLC control system maintains the opening of the electric regulating valve on the second branch pipeline unchanged; when | DO 2a -DO 2t When |>n, if DO 2a >DO 2t Then, the on-site PLC control system controls the electric regulating valve on the second branch pipeline to reduce the gas flow in the second branch pipeline. If DO 2a <DO 2tThen, the on-site PLC control system controls the electric regulating valve on the second branch pipeline to increase the gas flow in the second branch pipeline.

[0028] The beneficial effects of this invention are:

[0029] 1. The system of the present invention is equipped with corresponding blowers and pipelines for the microporous aeration device and the perforated pipe aeration device, thereby enabling the system to automatically control aeration, improving the aeration effect and saving energy.

[0030] 2. This invention implements zoned control in a mud-film composite MBBR biological treatment tank. The aerobic zone 1 adopts a constant gas volume control strategy, while the aerobic zone 2 adopts a constant dissolved oxygen control strategy. The aerobic MBBR zone uses feedforward based on aerobic zone 1 and feedback based on aerobic zone 2 to achieve dynamic dissolved oxygen control in the aerobic MBBR zone. This invention uses data from the online dissolved oxygen analyzer in aerobic zone 1 and the online ammonia nitrogen analyzer in aerobic zone 2 as parameters, which greatly improves the control accuracy and reduces maintenance costs.

[0031] 3. The control method of this invention enables precise aeration control, resulting in a system with strong resistance to shock loads and stable water quality. This invention has significant effects on the removal of COD, NH3-N, and TN, and the system effluent consistently meets the Class A effluent standard, with TN and NH3-N reaching the Class IV surface water standard.

[0032] 4. This invention reduces hardware investment in wastewater treatment plants and improves their economic efficiency. The low investment in the intelligent aeration equipment is beneficial for the stable operation and energy conservation of the pure membrane MBBR process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the precise aeration system of mud-film composite MBBR.

[0034] Figure 2 This is a schematic diagram of the structure of the aerobic MBBR region. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and specific examples:

[0036] Example 1

[0037] Combination Figure 1 and Figure 2 A precision aeration system for a mud-film composite MBBR includes a mud-film composite MBBR biological treatment tank 1, a blower aeration system, an online instrument monitoring system, a host computer 2, and a field PLC control system 3.

[0038] The mud-film composite MBBR biological treatment tank is divided into three zones along the water flow direction: aerobic zone 1, aerobic MBBR zone, and aerobic zone 2. The aerobic MBBR zone is equipped with a microporous aeration device 4, a suspended carrier 5, a perforated pipe aeration device 6, and an interception device 7.

[0039] The specific structures of the microporous aeration device 4, the suspended carrier 5, the perforated pipe aeration device 6, and the interception device 7 are existing technologies and will not be described in detail here.

[0040] Specifically, the volume ratio of the aerobic zone 1, aerobic MBBR zone, and aerobic zone 2 is 1:2:1, and the volume of the aerobic MBBR zone accounts for at least 50% of the volume of the mud-film composite MBBR biological treatment tank. In the aerobic MBBR zone, perforated pipe aeration devices are installed above the microporous aeration devices.

[0041] The blower aeration system includes a microporous aerator 8 and a perforated pipe aerator 9. The microporous aerator 8 is connected to a first main pipe 10, and a first branch pipe 11 and a second branch pipe 12 are connected to the first main pipe 10. The perforated pipe aerator is connected to a second main pipe 13.

[0042] The first main pipe 10 is connected to the microporous aeration device 4, the first branch pipe 11 is connected to the aerobic zone 1, the second branch pipe 12 is connected to the aerobic zone 2, and both the first branch pipe 11 and the second branch pipe 12 are equipped with electric regulating valves 14 and thermal gas flow meters 15. The second main pipe 13 is connected to the perforated pipe aeration device 6.

[0043] The main function of the perforated pipe aeration device 6 and the perforated pipe aeration blower 9 is to assist in the fluidization of the carrier. The perforated pipe aeration blower 9 is controlled according to the minimum air volume that can meet the fluidization of the carrier. This air volume value needs to be obtained through field test after the system has been running for half a year.

[0044] The online instrument monitoring system includes an online dissolved oxygen analyzer 16 installed in the aerobic zone 1, the aerobic MBBR zone, and the end of the aerobic zone 2; and an online ammonia nitrogen analyzer 17 installed at the end of the aerobic zone 2.

[0045] The host computer has a built-in aeration system control module. The host computer communicates with the field PLC control system, which sends collected data to the host computer for processing. The host computer then sends control commands to the field PLC control system.

[0046] The on-site PLC control system is electrically connected to the microporous aerator, perforated pipe aerator, thermal gas flow meter, electric regulating valve, online dissolved oxygen analyzer, and online ammonia nitrogen analyzer. The on-site PLC control system can collect data from the thermal gas flow meter 15, online dissolved oxygen analyzer 16, and online ammonia nitrogen analyzer 17. It can also adjust the airflow or frequency of the microporous aerator and perforated pipe aerator, and control their start / stop. Furthermore, it can adjust the opening of the electric regulating valve 14.

[0047] Example 2

[0048] A control method for a precise aeration system of a mud-film composite MBBR, employing a precise aeration system of a mud-film composite MBBR as described in Example 1, includes the following steps:

[0049] Step 1: In the aeration system control module, the aerobic zone 1 adopts a constant air volume control strategy, and the target value of the constant air volume is set to Q. 1t The on-site PLC control system 3 controls the electric regulating valve 14 on the first branch pipe 11 to make the gas flow rate in the first branch pipe 11 Q. 1t The constant air volume target value is calculated based on the number of micropore aerators arranged in the pool and the air output capacity of a single micropore aerator; it is a parameter that is set manually.

[0050] In this embodiment, 1000 microporous aerators are arranged in the aerobic zone, with each microporous aerator having an air output capacity of 3-5 m³ / h. 3 / h can be a value within the range of air output capacity, for example, 4m. 3 / h, then the target value of constant gas volume Q 1t =1000*4m 3 / h=4000m 3 / h;

[0051] Step 2: The aerobic zone 2 in the aeration system control module adopts a constant dissolved oxygen (DO) control strategy, with the target DO value set at DO. 2t The on-site PLC control system controls the gas flow in the second branch pipeline by controlling the electric regulating valve on the second branch pipeline, thereby ensuring that the dissolved oxygen in the aerobic zone is DO. 2t The target dissolved oxygen value is a manually set parameter; in this embodiment, DO... 2t It is 2 mg / L.

[0052] Step 3: In the aerobic MBBR zone of the aeration system control module, a dynamic dissolved oxygen control strategy is adopted, and the initial dynamic dissolved oxygen target value of the aerobic MBBR zone is set to DO. m The target dissolved oxygen (DO) value for the aerobic zone 2 is set manually. 2tThe initial dynamic dissolved oxygen target value DO in the aerobic MBBR zone m Similarly, in this embodiment, DO m It is 2 mg / L.

[0053] The new dynamic dissolved oxygen target value (DO) is calculated every 10 minutes. mT The calculation formula is: DO mT =DO m +K 前 +K 后 After that, DO m =DO mT Among them, K 前 K is the feedforward correction factor, calculated from the dissolved oxygen value in the aerobic zone 1. 后 This is the feedback correction factor, calculated from the ammonia nitrogen value of the effluent from the aerobic zone 2.

[0054] The following example illustrates the feedforward correction coefficient K. 前 The calculation process is as follows:

[0055] Assuming m = 0.5 mg / L and a = 0.3, the dissolved oxygen value of the online dissolved oxygen analyzer in the aerobic zone is collected every 10 time intervals. The dissolved oxygen value collected in the aerobic zone after the previous time interval T is DO. 1T The dissolved oxygen value (DO) collected after the next time interval T in the aerobic zone 1 is DO. 1(T+1) When -0.5 ≤ DO 1(T+1) -DO 1T When K is ≤0.5 前 =0; when 0.5<DO 1(T+1) -DO 1T When K ≤ 1 前 =-0.3; when DO 1(T+1) -DO 1T When K > 1, 前 = -0.6; when -1 ≤ DO 1(T+1) -DO 1T When K < -0.5, 前 =0.3; when DO 1(T+1) -DO 1T When K < -1 前 =0.6.

[0056] The following example illustrates the feedback correction coefficient K. 后 The calculation process is as follows:

[0057] Assuming m = 0.5 mg / L and b = 0.5, the target ammonia nitrogen value for the effluent from the aerobic zone II is set to NH3-N. t The concentration was 1.5 mg / L. The actual ammonia nitrogen value of the effluent from the online ammonia nitrogen analyzer in the aerobic zone 2 was collected every 10 minutes.a When -0.5 ≤ NH3-N a When -1.5 ≤ 0.5, K 后 =0; when 0.5 < NH3-N a When -1.5≤1, K 后 =0.5; when NH3-N a When -1.5 > 1, K 后 =1; when -1≤NH3-N a When -1.5 < -0.5, K 后 = -0.5; when NH3-N a -1.5 < -1, K 后 =-1.

[0058] In step 2, the dissolved oxygen in the aerobic zone 2 is set to DO. 2t The specific process is as follows:

[0059] Set DO 2t =2mg / L, n=0.5, every 10 minutes, the dissolved oxygen value (DO) of the online dissolved oxygen analyzer in the aerobic zone 2 was collected. 2a DO 2a =2.2mg / l, then |DO 2a -DO 2t If |≤0.5, the on-site PLC control system maintains the opening of the electric regulating valve on the second branch pipeline unchanged.

[0060] When DO 2a =2.6 mg / L, |DO 2a -DO 2t |>0.5, and DO 2a >DO 2t The on-site PLC control system then controls the electric regulating valve on the second branch pipeline to reduce the opening of the electric regulating valve, thereby reducing the gas flow in the second branch pipeline. The specific reduction in flow rate is set according to the actual situation.

[0061] When DO2a = 1.3 mg / L, |DO 2a -DO 2t |>0.5, and DO 2a <DO 2t The on-site PLC control system then controls the electric regulating valve on the second branch pipeline to increase the opening of the electric regulating valve, thereby increasing the gas flow rate in the second branch pipeline. The specific increase in flow rate is set according to the actual situation.

[0062] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A control method for a precise aeration system of a mud-film composite MBBR, characterized in that, The system includes a precision aeration system for a mud-film composite MBBR, comprising a mud-film composite MBBR biological tank, a blower aeration system, an online instrument monitoring system, a host computer, and a field PLC control system. The mud-film composite MBBR biological tank is divided into three aerobic zones: aerobic zone 1, aerobic MBBR zone, and aerobic zone 2 along the water flow direction. The aerobic MBBR zone is equipped with microporous aeration devices, suspended carriers, perforated pipe aeration devices, and interception devices. The aeration system includes a microporous aeration blower and a perforated pipe aeration blower. The microporous aeration blower is connected to a first main pipe, and a first branch pipe and a second branch pipe are connected to the first main pipe. The perforated pipe aeration blower is connected to a second main pipe. The first main pipe is connected to the microporous aeration device, the first branch pipe is connected to aerobic zone one, and the second branch pipe is connected to aerobic zone two. Electric regulating valves and thermal gas flow meters are installed on both the first branch pipe and the second branch pipe. The second main pipe is connected to the perforated pipe aeration device. The online instrument monitoring system includes online dissolved oxygen analyzers installed in the aerobic zone 1, the aerobic MBBR zone, and the end of the aerobic zone 2; and an online ammonia nitrogen analyzer installed at the end of the aerobic zone 2. The host computer has a built-in aeration system control module; The host computer communicates with the field PLC control system, and the field PLC control system is electrically connected to the microporous aerator, perforated pipe aerator, thermal gas flow meter, electric regulating valve, online dissolved oxygen analyzer and online ammonia nitrogen analyzer. The control method includes the following steps: Step 1: In the aeration system control module, the aerobic zone 1 adopts a constant air volume control strategy, and the target value of the constant air volume is set to Q. 1t The on-site PLC control system controls the electric regulating valve on the first pipeline to make the gas flow rate in the first pipeline Q. 1t ; Step 2: The aerobic zone 2 in the aeration system control module adopts a constant dissolved oxygen (DO) control strategy, with the target DO value set at DO. 2t The on-site PLC control system controls the gas flow in the second branch pipeline by controlling the electric regulating valve on the second branch pipeline, thereby ensuring that the dissolved oxygen in the aerobic zone is DO. 2t ; Step 3: In the aerobic MBBR zone of the aeration system control module, a dynamic dissolved oxygen control strategy is adopted, and the initial dynamic dissolved oxygen target value of the aerobic MBBR zone is set to DO. m Every time interval T, a new dynamic target value of dissolved oxygen (DO) is calculated. mT The calculation formula is: DO mT =DO m +K 前 +K 后 After that, DO m =DO mT Among them, K 前 K is the feedforward correction factor, calculated from the dissolved oxygen value in the aerobic zone 1. 后 This is the feedforward correction factor, calculated from the ammonia nitrogen value of the effluent from the aerobic zone II. Feedforward correction coefficient K 前 The calculation process is as follows: Dissolved oxygen values ​​are collected from the online dissolved oxygen analyzer in aerobic zone 1 at intervals T. The dissolved oxygen value collected in aerobic zone 1 after the previous interval T is DO. 1T The dissolved oxygen value (DO) collected after the next time interval T in the aerobic zone 1 is DO. 1（T+1） When -m≤DO 1（T+1） -DO 1T When ≤m, K 前 =0; when m < DO 1（T+1） -DO 1T When ≤2m, K 前 =-a; when DO 1（T+1） -DO 1T When K > 2m 前 =-2a; when -2m≤DO 1（T+1） -DO 1T When <-m, K 前 =a; when DO 1（T+1） -DO 1T When K < -2m 前 =2a; where m is a fixed positive value and a is a fixed positive value; Feedback correction coefficient K 后 The calculation process is as follows: The target value for ammonia nitrogen in the effluent from the aerobic zone II is set to NH3-N. t At each time interval T, the actual ammonia nitrogen value of the effluent from the online ammonia nitrogen analyzer in the aerobic zone II was collected as NH3-N. a When -m≤NH3-N a -NH3-N t When ≤m, K 后 =0; when m < NH3-N a -NH3-N t When ≤2m, K 后 =b;When NH3-N a -NH3-N t When K > 2m 后 =2b; when -2m≤NH3-N a -NH3-N t When <-m, K 后 =-b;when NH3-N a -NH3-N t <-2m, K 后 =-2b; where m is a fixed positive value and b is a fixed positive value.

2. The control method for a precise aeration system of a mud-film composite MBBR according to claim 1, characterized in that, The volume of the aerobic MBBR zone shall be at least 50% of the volume of the mud-film composite MBBR biological treatment tank.

3. The control method for a precise aeration system of a mud-film composite MBBR according to claim 1, characterized in that, In the aerobic MBBR zone, the perforated tube aeration device is positioned above the microporous aeration device.

4. The control method for a precise aeration system of a mud-film composite MBBR according to claim 1, characterized in that, The target dissolved oxygen (DO) value for constant dissolved oxygen in the aerobic zone 2 2t The initial dynamic dissolved oxygen target value DO in the aerobic MBBR zone m same.

5. The control method for a precise aeration system of a mud-film composite MBBR according to claim 1, characterized in that, In step 2, the dissolved oxygen in the aerobic zone 2 is set to DO. 2t The specific process is as follows: At intervals T, the dissolved oxygen value (DO) of the online dissolved oxygen analyzer in the aerobic zone 2 was collected. 2a , when |DO 2a -DO 2t When | ≤ n, the on-site PLC control system maintains the opening of the electric regulating valve on the second branch pipeline unchanged; when | DO 2a -DO 2t When |>n, if DO 2a >DO 2t Then, the on-site PLC control system controls the electric regulating valve on the second branch pipeline to reduce the gas flow in the second branch pipeline. If DO 2a <DO 2t Then, the on-site PLC control system controls the electric regulating valve on the second branch pipeline to increase the gas flow in the second branch pipeline.

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