Automatic negative pressure control system and implementation method thereof

Abstract

The invention belongs to the technical field of printing and packaging, and provides an automatic negative pressure control system and an implementation method thereof.The automatic negative pressure control system comprises a main air pipe exhaust isolating valve, a main air pipe exhaust fan, a main exhaust pipe negative pressure sensor, a main exhaust pipe VOC exhaust concentration sensor, a plurality of color cell modules and a PLC negative pressure automatic control subsystem; each color cell module comprises a printing machine equipment drying oven, a fresh air valve, an electric heating box, a drying oven fan, a color cell VOC return air concentration sensor, a self-circulation return air valve, a color cell exhaust valve and a color cell negative pressure sensor; according to the invention, through the arrangement of the pressure sensor, the VOC concentration sensor and the PLC negative pressure automatic control subsystem, VOC concentration detection and VOC concentration automatic closed-loop control are realized, and each control point can be independently and automatically controlled.

Description

Technical Field

[0001] This invention relates to the field of printing and packaging technology, and in particular to an automatic negative pressure control system and its implementation method. Background Technology

[0002] Under the regulations of environmental improvement policies, the requirements for VOC emissions in the printing and packaging industry are constantly being improved and raised. In promoting VOC treatment solutions for printing and packaging enterprises, the current common method for printing press equipment to meet VOC emission standards is to use Regenerative Thermal Oxidizer (RTO) for regenerative combustion. RTO requires low air volume and a high concentration of approximately 2 grams per cubic meter or higher to ensure low energy consumption during RTO operation. Furthermore, after RTO regenerative combustion, heat energy can be recovered and utilized to achieve energy conservation, emission reduction, and other goals. The higher the air volume of the RTO equipment, the higher its price; more importantly, the lower the concentration, the higher the energy consumption during RTO operation. Currently, the printing and packaging industry faces the problem that traditional printing and packaging equipment involves high air volume, low concentration, and high energy consumption. After each color group is inked and printed, it enters an oven for drying with hot air. During the drying process, solvents evaporate and are carried away by the hot air, resulting in direct heat loss and significant energy consumption during production. Furthermore, most printing press ovens operate under positive pressure, resulting in a large amount of volatile gases remaining in the workshop environment, causing a strong odor. Therefore, it is necessary to install a large amount of unorganized exhaust ventilation to improve the workshop environment, which significantly increases operating energy consumption. In this situation, it is essential to reduce exhaust volume and increase concentration to improve exhaust air concentration, thereby reducing production energy consumption and lowering the initial investment cost of purchasing RTO equipment. Implementing reduced exhaust volume and increased concentration in printing press equipment, through new construction or optimization, involves recycling the hot air energy from the printing oven. The recycling volume is adjusted manually or automatically according to the size of the printing plate, with varying amounts. Recycling reduces emissions and increases VOC concentration, achieving energy conservation and reduced RTO operating costs without affecting equipment production quality. Currently, printing press equipment uses the following methods to reduce airflow and increase density: manual adjustment of circulating return air, self-circulation, series, parallel, large circulation, self-circulation + parallel, and independent inlet and outlet fan return air. All of the above methods combined with a PLC control system can achieve the purpose of reducing airflow and increasing density, and each method has its own advantages and disadvantages.

[0003] Currently, printing press airflow adjustment is typically controlled by manual or electric valves, but valve opening adjustment relies heavily on human experience. Adjustments are usually made by the equipment manufacturer or user, and once adjusted, the valves typically remain in a fixed state, unable to adjust automatically. However, printing press airflow is affected by many external factors, such as the number of colors used and the number of printing presses. Since printing press fans consist of multiple color group fans, and the number of colors is not fixed, and each company has a varying number of printing presses and other equipment, the airflow from these fans is collected and discharged centrally. Furthermore, factors such as the distance between fan intakes, airflow volume, and air pressure affect airflow and energy consumption, and the number of external printing presses also affects airflow discharge. Therefore, the energy consumption of each color group or the total exhaust volume varies considerably. Thus, current airflow adjustment methods cannot meet the requirements for stable and precise airflow discharge. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide an automatic negative pressure control system and its implementation method, which solves the problem that the existing system relies on subjective adjustment and cannot achieve reliable, stable and accurate air volume emission.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] An automatic negative pressure control system includes: a main duct exhaust isolation valve, a main duct exhaust fan, a main exhaust duct negative pressure sensor, a main exhaust duct VOC exhaust concentration sensor, several color group modules, and a PLC negative pressure automatic control subsystem; each color group module includes: a printing press equipment oven, a fresh air valve, an electric heating box, an oven fan, a color group VOC return air concentration sensor, a self-circulating return air valve, a color group exhaust valve, and a color group negative pressure sensor;

[0007] The PLC negative pressure automatic control subsystem is connected to the main duct exhaust isolation valve, the main duct exhaust fan, the main exhaust duct negative pressure sensor, the main exhaust duct VOC exhaust concentration sensor, and the color group module, respectively. The main duct exhaust isolation valve, the main duct exhaust fan, the main exhaust duct negative pressure sensor, and the main exhaust duct VOC exhaust concentration sensor are connected in sequence. The main exhaust duct VOC exhaust concentration sensor is connected to each color group module. The fresh air valve, the electric heating box, the oven fan, the color group VOC return air concentration sensor, the printing machine equipment oven, the color group negative pressure sensor, and the color group exhaust valve are connected in sequence. The two ends of the self-circulating return air valve are connected to the outlet of the fresh air valve and the inlet of the color group exhaust valve, respectively.

[0008] The color group negative pressure sensor is used to detect the exhaust negative pressure of the printing press equipment oven, obtain color group negative pressure information, and automatically control the constant pressure exhaust volume of each color group based on the color group negative pressure information; the color group VOC return air concentration sensor is used to detect the VOC return air concentration input to the printing press equipment oven, and obtain the color group VOC concentration; the main exhaust duct VOC exhaust air concentration sensor is used to detect the VOC exhaust air concentration of the main exhaust duct, and obtain the exhaust duct VOC concentration; the main exhaust duct negative pressure sensor is used to detect the exhaust negative pressure of the main exhaust duct, obtain exhaust duct negative pressure information, and automatically control the constant pressure main exhaust volume of the main exhaust duct based on the exhaust duct negative pressure information; the PLC negative pressure automatic control subsystem is used to control the constant pressure exhaust volume of the main exhaust duct according to the set target negative pressure value. The system detects the negative pressure information of the exhaust duct and the VOC concentration in the exhaust duct, and when the negative pressure information of the exhaust duct or the color group negative pressure information does not meet the target negative pressure value, the system uses fuzzy PID control to adjust the fresh air valve, the self-circulating return air valve, and the color group exhaust valve until the negative pressure information of the exhaust duct and the color group negative pressure information meet the target negative pressure value. Similarly, when the VOC concentration of the color group or the VOC concentration of the exhaust duct does not meet the target VOC concentration, the system uses fuzzy PID control to adjust the fresh air valve, the self-circulating return air valve, and the color group exhaust valve until the VOC concentration of the color group or the VOC concentration of the exhaust duct is adjusted to meet the target VOC concentration.

[0009] Preferably, the PLC negative pressure automatic control subsystem includes: an input module, an automatic control module, and an output module connected in sequence; the input module includes: a negative pressure sensor unit, a target negative pressure value unit, a valve manual setting unit, and an output valve feedback unit; the automatic control module includes: a sampling and filtering unit, an input upper limit unit, an input lower limit unit, a sensor type unit, a sensor range unit, a data processing unit, a feedback comparison unit, a manual / automatic switching unit, a comparison calculation unit, a non-action area unit, a regulation intensity setting unit, a regulation time setting unit, a regulation cycle setting unit, a fuzzy control calculation unit, an alarm setting prompt unit, a data conversion unit, a data upper limit unit, a data lower limit unit, a proportional gain unit, and a fault judgment unit; the output module includes: an output actuator;

[0010] The negative pressure sensor unit is connected to the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit, respectively; the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit are connected to the data processing unit, respectively; the target negative pressure value unit is connected to the data processing unit and the manual / automatic switching unit, respectively; the data processing unit is connected to the comparison processing unit; the comparison processing unit is connected to the inactive area unit, the adjustment intensity setting unit, the adjustment time setting unit, the adjustment cycle setting unit, the fuzzy control processing unit, and the alarm setting prompt unit, respectively; the inactive area unit, the adjustment intensity setting ... The given unit, the adjustment time given unit, the adjustment cycle given unit, the fuzzy control calculation unit, and the alarm setting prompt unit are all connected to the data conversion unit; the feedback comparison unit is connected to the data calculation unit and the data conversion unit; the valve manual given unit is connected to the manual / automatic switching unit; the manual / automatic switching unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the data conversion unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the output valve feedback unit is connected to the fault judgment unit; the upper data limit unit, the lower data limit unit, the proportional gain unit, and the fault judgment unit are all connected to the output actuator.

[0011] Preferably, a method for implementing an automatic negative pressure control system includes:

[0012] The input information of the negative pressure sensor in the target system is collected, the input information is sampled and filtered, and the filtered input information is limited according to the preset upper and lower limits to obtain visualized data.

[0013] Receive the target negative pressure value input from the host computer touch screen, calculate the difference between the target negative pressure value and the visualized data, and obtain the operating deviation;

[0014] The operating deviation is calculated using fuzzy logic PID based on the preset non-action range, cycle, adjustment time, and adjustment range to obtain variable output;

[0015] The variable output is subjected to upper and lower limit processing, and the limited variable output is sent to the valve actuator of the target system for negative pressure regulation. Then, the process returns to the step "collect input information from the negative pressure sensor in the target system, sample and filter the input information, and limit the filtered input information according to the preset upper and lower limits to obtain visualized data".

[0016] The present invention discloses the following technical effects:

[0017] This invention provides an automatic negative pressure control system and its implementation method, which solves the problem that existing systems rely on subjective adjustment and cannot achieve reliable, stable and accurate air volume emission, and realizes VOC concentration detection and automatic closed-loop control of VOC concentration. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the automatic negative pressure control system provided in an embodiment of the present invention;

[0020] Figure 2 This is a structural diagram of the PLC negative pressure automatic control subsystem provided in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1-Fresh air valve, 2-Electric heating box, 3-Oven fan, 4-Color group VOC return air concentration sensor, 5-Self-circulating return air valve, 6-Color group exhaust valve, 7-Color group negative pressure sensor, 8-Main exhaust duct VOC exhaust concentration sensor, 9-Main exhaust duct negative pressure sensor, 10-Main duct exhaust fan, 11-Main duct exhaust isolation valve. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide an automatic negative pressure control system and its implementation method, which solves the problem that existing systems rely on subjective adjustment and cannot achieve reliable, stable and accurate air volume emission.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1This is a schematic diagram of the automatic negative pressure control system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the present invention provides an automatic negative pressure control system, including: a main duct exhaust isolation valve 11, a main duct exhaust fan 10, a main exhaust duct negative pressure sensor 9, a main exhaust duct VOC exhaust concentration sensor 8, several color group modules, and a PLC negative pressure automatic control subsystem; each color group module includes: a printing machine equipment oven, a fresh air valve 1, an electric heating box 2, an oven fan 3, a color group VOC return air concentration sensor 4, a self-circulating return air valve 5, a color group exhaust valve 6, and a color group negative pressure sensor 7;

[0027] The PLC negative pressure automatic control subsystem is connected to the main duct exhaust isolation valve 11, the main duct exhaust fan 10, the main exhaust duct negative pressure sensor 9, the main exhaust duct VOC exhaust concentration sensor 8, and the color group module, respectively. The main duct exhaust isolation valve 11, the main duct exhaust fan 10, the main exhaust duct negative pressure sensor 9, and the main exhaust duct VOC exhaust concentration sensor 8 are connected in sequence. The main exhaust duct VOC exhaust concentration sensor 8 is connected to each color group module. The fresh air valve 1, the electric heating box 2, the oven fan 3, the color group VOC return air concentration sensor 4, the printing machine equipment oven, the color group negative pressure sensor 7, and the color group exhaust valve 6 are connected in sequence. The two ends of the self-circulating return air valve 5 are connected to the outlet of the fresh air valve 1 and the inlet of the color group exhaust valve 6, respectively.

[0028] The color group negative pressure sensor 7 is used to detect the exhaust negative pressure of the printing press equipment oven, obtain color group negative pressure information, and automatically control the constant pressure exhaust volume of each color group based on the color group negative pressure information; the color group VOC return air concentration sensor 4 is used to detect the VOC return air concentration input to the printing press equipment oven, and obtain the color group VOC concentration; the main exhaust duct VOC exhaust air concentration sensor 8 is used to detect the VOC exhaust air concentration of the main exhaust duct, and obtain the exhaust duct VOC concentration; the main exhaust duct negative pressure sensor 9 is used to detect the exhaust negative pressure of the main exhaust duct, obtain exhaust duct negative pressure information, and automatically control the constant pressure main exhaust volume of the main exhaust duct based on the exhaust duct negative pressure information; the PLC negative pressure automatic control subsystem is used to control the constant pressure exhaust volume of the main exhaust duct based on the set target negative pressure value and... The target VOC concentration is detected by monitoring the negative pressure information of the exhaust duct and the VOC concentration of the exhaust duct. When the negative pressure information of the exhaust duct or the negative pressure information of the color group does not meet the target negative pressure value, fuzzy PID control is used to adjust the fresh air valve 1, the self-circulating return air valve 5, and the color group exhaust valve 6 until the negative pressure information of the exhaust duct and the negative pressure information of the color group meet the target negative pressure value. When the VOC concentration of the color group or the VOC concentration of the exhaust duct does not meet the target VOC concentration, fuzzy PID control is used to adjust the fresh air valve 1, the self-circulating return air valve 5, and the color group exhaust valve 6 until the VOC concentration of the color group or the VOC concentration of the exhaust duct is adjusted to meet the target VOC concentration.

[0029] Preferably, the PLC negative pressure automatic control subsystem includes: an input module, an automatic control module, and an output module connected in sequence; the input module includes: a negative pressure sensor unit, a target negative pressure value unit, a valve manual setting unit, and an output valve feedback unit; the automatic control module includes: a sampling and filtering unit, an input upper limit unit, an input lower limit unit, a sensor type unit, a sensor range unit, a data processing unit, a feedback comparison unit, a manual / automatic switching unit, a comparison calculation unit, a non-action area unit, a regulation intensity setting unit, a regulation time setting unit, a regulation cycle setting unit, a fuzzy control calculation unit, an alarm setting prompt unit, a data conversion unit, a data upper limit unit, a data lower limit unit, a proportional gain unit, and a fault judgment unit; the output module includes: an output actuator;

[0030] The negative pressure sensor unit is connected to the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit, respectively; the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit are connected to the data processing unit, respectively; the target negative pressure value unit is connected to the data processing unit and the manual / automatic switching unit, respectively; the data processing unit is connected to the comparison processing unit; the comparison processing unit is connected to the inactive area unit, the adjustment intensity setting unit, the adjustment time setting unit, the adjustment cycle setting unit, the fuzzy control processing unit, and the alarm setting prompt unit, respectively; the inactive area unit, the adjustment intensity setting ... The given unit, the adjustment time given unit, the adjustment cycle given unit, the fuzzy control calculation unit, and the alarm setting prompt unit are all connected to the data conversion unit; the feedback comparison unit is connected to the data calculation unit and the data conversion unit; the valve manual given unit is connected to the manual / automatic switching unit; the manual / automatic switching unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the data conversion unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the output valve feedback unit is connected to the fault judgment unit; the upper data limit unit, the lower data limit unit, the proportional gain unit, and the fault judgment unit are all connected to the output actuator.

[0031] Furthermore, a method for implementing an automatic negative pressure control system includes:

[0032] The input information of the negative pressure sensor in the target system is collected, the input information is sampled and filtered, and the filtered input information is limited according to the preset upper and lower limits to obtain visualized data.

[0033] Receive the target negative pressure value input from the host computer touch screen, calculate the difference between the target negative pressure value and the visualized data, and obtain the operating deviation;

[0034] The operating deviation is calculated using fuzzy logic PID based on the preset non-action range, cycle, adjustment time, and adjustment range to obtain variable output;

[0035] The variable output is subjected to upper and lower limit processing, and the limited variable output is sent to the valve actuator of the target system for negative pressure regulation. Then, the process returns to the step "collect input information from the negative pressure sensor in the target system, sample and filter the input information, and limit the filtered input information according to the preset upper and lower limits to obtain visualized data".

[0036] Specifically, the relevant components are as follows: each color group of the printing press equipment is equipped with a negative pressure sensor 4-20MA-1500PA (air pressure transmitter or air pressure sensor 4-20MA-1500PA) at the exhaust port of the oven. The exhaust valve, fresh air valve 1, and return air valve are all high-sealing air valves. The 25N actuator analog quantity 4-20MA adjustable type controls the exhaust volume of each color group. Each color group is equipped with an infrared LEL concentration detection and control device or a detection port is controlled by a set of LEL concentration control loop detection. In addition, it is coordinated with the self-developed PLC automatic control system for closed-loop detection and control.

[0037] refer to Figure 2 Description of the automatic control system's operation process:

[0038] S1: First, the PLC collects the input information of the negative pressure sensor through the analog input module. After selecting the sensor input type inside the PLC, the value is obtained by sampling and filtering. Then, the range, upper limit and lower limit parameters of the sensor are set to obtain a real and visualized data.

[0039] S2: The target negative pressure value input through the host computer touch screen is compared with the PLC sampling value. The deviation is processed by calculation (setting the non-action range, setting the cycle and adjustment time, and the adjustment amplitude and using fuzzy PID calculation to calculate and control, so as to achieve the effect of fast system response without overshoot and lag) and outputs a value.

[0040] S3: Set the upper and lower limit outputs for the obtained value and provide various alarm outputs (to facilitate later fault confirmation and maintenance). The output value is supplied to the valve actuator through the PLC's analog output module. The valve's movement drives the change of the negative pressure sensor on the valve pipeline.

[0041] S4: During the operation of the PLC, the sampling operations from S1 to S3 are repeatedly performed on the target value and the sampled value. The obtained values ​​are used to control the valve actuator to achieve a closed-loop system with constant negative pressure.

[0042] S5: The valve actuator provides a manual setting window and real-time valve position feedback, making it easy to detect and handle problems in a timely manner.

[0043] Preferably, VOC concentration detection and automatic control: VOC concentration cyclic detection for each color group and main exhaust can be set independently. The concentration value can be set according to the actual situation. When the concentration exceeds the set value, the VOC concentration is reduced by unorganized exhaust. The concentration is automatically controlled by PLC to ensure that the concentration is within the set value. 1) Automatic control of oven negative pressure: Each color group is equipped with a negative pressure sensor for independent detection and control. According to the set negative pressure value of the oven, the PLC automatically controls the detection to ensure that each oven group is under negative pressure at the set value; 2) Volatile gases of solvents and water: Each color group circulates independently and does not affect each other. Different volatile gases are discharged separately. The PLC automatically controls the switching to ensure that different types of volatile gases do not mix; 3) Automatic control of main exhaust volume: A negative pressure sensor is added to the main pipeline. The exhaust volume is automatically adjusted according to the number of color groups used to ensure that the exhaust volume of each color group is consistent and the oven is under negative pressure; 4) The heating box has multiple heating methods and can be used in one machine. The system can operate in multiple heating modes: pure electric heating, heating element heating, heat exchanger heating (the heat source for the heat exchanger can be steam, thermal oil, or hot water), and hot air duct heating. External equipment heats the air, which is then piped into the system as hot air. A PLC controls the temperature and hot air volume of each color group. A negative pressure sensor is installed in each group to automatically control the amount of hot air, balancing the negative pressure in each color group's oven, thus achieving energy saving, emission reduction, and concentration enhancement. These three heating methods can be used simultaneously, in combination, or separately to ensure energy saving, emission reduction, and concentration enhancement.

[0044] Furthermore, after the air is heated by the heating device, it is then sent into the drying chamber by a blower. The waste heat from the drying chamber is partially recycled through a pipeline (saving some energy) and partially discharged through the exhaust duct. The PLC controls the opening of the electric valve through feedback from the negative pressure sensor, and controls the amount of exhaust through the exhaust fan to achieve precise discharge and reduce energy waste.

[0045] Furthermore, each printing press is calculated based on 10 color groups. The principle of the automatic negative pressure control system and its interconnected points, including negative pressure sensors, air valves, LEL concentration sensors, etc., is as follows: The main pipe negative pressure sensor detects and controls → the frequency converter controls the main exhaust fan to maintain a constant exhaust volume → VOC detection controls the main exhaust concentration to control the required waste gas concentration → color group exhaust negative pressure detection and control → exhaust valve controls the required airflow → energy-saving return air valve adjusts the switch → VOC detection controls the color group return air concentration to control the required concentration → fresh air valve 1 replenishes the required airflow to reduce VOC concentration. Conversely: fresh air valve 1 replenishes airflow → VOC concentration decreases → return airflow decreases → negative pressure detection is low → exhaust volume increases → VOC concentration detection → main pipe negative pressure detection is low → main exhaust fan (frequency converter controlled) increases main exhaust volume.

[0046] Specifically, the following case analysis and comparison demonstrate the actual situation: The function of the color group exhaust valve 6 is to save energy and reduce emissions by adjusting the exhaust volume of each group and increasing the return air circulation to achieve the purpose of energy saving and emission reduction. Traditionally, the valve in this part is a manual or electric valve. The best adjustment method is to adjust it under the premise of no external factors. Manual adjustment or electric manual setting display of valve angle %. Exhaust adjustment can only be based on feeling and experience. When adjusting the exhaust volume, start all color groups and main exhaust fans. Open 10 color groups or 1 color group to adjust the exhaust volume. After adjustment, the exhaust volume is fixed. Assuming the current main exhaust volume is 10,000 cubic meters, with each group consisting of 1,000 cubic meters x 10 groups, the following problems may arise: A. External factors affecting the operation of color groups: Assuming all equipment operates at 10 colors x 1,000 cubic meters with a properly adjusted main exhaust volume of 10,000 cubic meters, the main exhaust volume will change due to the combined resistance of the main duct caused by the start / stop of other printing equipment. This will alter the previously adjusted exhaust volume, energy consumption, and environmental conditions, and the numerous external factors making adjustment and control impossible. B. If previously operating with 10 color groups, and then switching to operating with 5 color groups at 5,000 cubic meters, while maintaining the same 10,000 cubic meter main exhaust volume, the increased exhaust volume will lead to higher energy consumption, potentially impacting the environment and product quality. Adjusting the main exhaust volume based on experience after encountering this problem will result in inaccurate exhaust volume due to changes in the distance and location of the color group exhausts, and it will be impossible to restore it to its previous state.

[0047] Furthermore, key points of this embodiment: A negative pressure sensor is installed at each exhaust volume control point to ensure independent closed-loop automatic control of each air valve control point. VOC concentration is detected by an infrared LEL concentration sensor or automatically controlled. Currently, all are 25N electric analog volume control valves. Adjustment method: When adjusting via the touchscreen, start all color group fans and main exhaust fans. Set color group exhaust valve 6 to 0, and color group return air valve to 100% open (the color group return air valve is a patented design for separately discharging water-based or ester-soluble inks for backup control). Set color group fresh air valve 1 to 0. After starting each oven fan 3 and main exhaust fan of the printing press, the current pipeline self-circulation negative pressure value is displayed on the touchscreen (the negative pressure value displayed varies depending on the structure and installation location of each printing press manufacturer). The main exhaust fan inverter control is set in the touchscreen. The main exhaust duct negative pressure sensor 9 is set to a constant negative pressure of -600 PA. After the main exhaust duct automatic control touch screen displays a constant negative pressure of -600 PA, the PLC automatic negative pressure control system touch screen sets the negative pressure value required for each color group oven to reach the negative pressure state. After the negative pressure stabilizes, assuming the current main exhaust air volume is 10,000 cubic meters and the printing press equipment is configured with 10 groups, each group having an air volume of 1,000 cubic meters x 10 groups, at this point, it is only necessary to set the required replenishment amount for each color group fresh air valve 1. The color group negative pressure sensor detects the negative pressure change, and the system will automatically control each color group exhaust valve 6 to adjust to the oven negative pressure state. At this time, the main exhaust air volume will also automatically balance the duct pressure according to the amount of fresh air replenished. After checking the oven status and balancing the negative pressure control, the debugging is completed.

[0048] Specifically, external factors affect whether the equipment is turned on, off, or running: Assuming all equipment is operated at 1000 cubic meters x 10 groups, with each group's simulated air volume valve opening at 20%, and the main exhaust frequency at 35 Hz and air volume at 10,000 cubic meters, the main exhaust air volume will also change due to variations in the resistance of the main duct as other printing equipment starts and stops. For example, if the resistance at the collection point is high, the negative pressure detection pressure will decrease, and the main exhaust fan frequency will increase, keeping the negative pressure detection automatic control at -600 Pa and the total exhaust volume unchanged. If the resistance at the collection point is low, the negative pressure detection pressure will increase, and the main exhaust fan frequency will decrease, keeping the negative pressure detection automatic control at -600 Pa and the total exhaust volume unchanged. Energy consumption and environmental conditions will not change; regardless of changes in external factors, the main exhaust fan negative pressure detection will remain at -600 Pa.

[0049] Furthermore, the previous operation was based on 10 color groups. Assuming that the operation changes to 5 color groups, 5000 cubic meters are discharged, and all other air valves are closed, the main exhaust air volume is still 10000 cubic meters. At this time, the negative pressure detection pressure of the main exhaust air will increase, and the frequency converter of the main exhaust fan will decrease to maintain the negative pressure detection at -600PA. The air volume, energy consumption, and environment of each group will not change. No matter how the color groups change, the opening of the analog air valve of each group is 20%, and the negative pressure detection of the main exhaust fan will be maintained at -600PA.

[0050] Specifically, under normal use, regardless of whether multiple color groups of the printing press are on or off, the exhaust volume of each color group will be automatically adjusted and controlled by the PLC automatic control system through the air valve to maintain a negative pressure balance. The exhaust volume of the color group will not change. When a color group is not on, it is closed. When more color groups are on, the main exhaust volume is increased. When fewer color groups are on, the main exhaust volume is decreased. Regardless of how many units are on, the negative pressure value of the main exhaust air volume is kept in a constant pressure control state (closed-loop control). For example, when other N printing presses are on or off, the resistance generated by external factors will keep the negative pressure value in a constant pressure control state. When the resistance is high, the main exhaust fan frequency will be high. When the resistance is low, the main exhaust fan frequency will be low. The negative pressure control will always remain in an automatic constant pressure state. All the set negative pressure control air volume, energy consumption, environment and negative pressure value remain unchanged. This achieves independent segmented control of each point without interference, achieving the purpose of energy saving and emission reduction through automatic negative pressure control.

[0051] The beneficial effects of this invention are as follows:

[0052] This invention achieves VOC concentration detection and automatic closed-loop control of VOC concentration by setting up a pressure sensor, a VOC concentration sensor, and a PLC negative pressure automatic control subsystem, and can independently and automatically control each control point.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0054] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An automatic negative pressure control system, characterized in that, include: The system includes a main duct exhaust isolation valve, a main duct exhaust fan, a main exhaust duct negative pressure sensor, a main exhaust duct VOC exhaust concentration sensor, several color group modules, and a PLC negative pressure automatic control subsystem; each color group module includes: a printing press equipment oven, a fresh air valve, an electric heating box, an oven fan, a color group VOC return air concentration sensor, a self-circulating return air valve, a color group exhaust valve, and a color group negative pressure sensor; The PLC negative pressure automatic control subsystem is connected to the main duct exhaust isolation valve, the main duct exhaust fan, the main exhaust duct negative pressure sensor, the main exhaust duct VOC exhaust concentration sensor, and the color group module, respectively. The main duct exhaust isolation valve, the main duct exhaust fan, the main exhaust duct negative pressure sensor, and the main exhaust duct VOC exhaust concentration sensor are connected in sequence. The main exhaust duct VOC exhaust concentration sensor is connected to each color group module. The fresh air valve, the electric heating box, the oven fan, the color group VOC return air concentration sensor, the printing machine equipment oven, the color group negative pressure sensor, and the color group exhaust valve are connected in sequence. The two ends of the self-circulating return air valve are connected to the outlet of the fresh air valve and the inlet of the color group exhaust valve, respectively. The color group negative pressure sensor is used to detect the exhaust negative pressure of the printing press equipment oven, obtain color group negative pressure information, and automatically control the constant pressure exhaust volume of each color group based on the color group negative pressure information; the color group VOC return air concentration sensor is used to detect the VOC return air concentration input to the printing press equipment oven, and obtain the color group VOC concentration; the main exhaust duct VOC exhaust air concentration sensor is used to detect the VOC exhaust air concentration of the main exhaust duct, and obtain the exhaust duct VOC concentration; the main exhaust duct negative pressure sensor is used to detect the exhaust negative pressure of the main exhaust duct, obtain exhaust duct negative pressure information, and automatically control the constant pressure main exhaust volume of the main exhaust duct based on the exhaust duct negative pressure information; the PLC negative pressure automatic control subsystem is used to control the constant pressure exhaust volume of the main exhaust duct according to the set target negative pressure value. The system detects the negative pressure information of the exhaust duct and the VOC concentration in the exhaust duct, and when the negative pressure information of the exhaust duct or the color group negative pressure information does not meet the target negative pressure value, the system uses fuzzy PID control to adjust the fresh air valve, the self-circulating return air valve, and the color group exhaust valve until the negative pressure information of the exhaust duct and the color group negative pressure information meet the target negative pressure value. Similarly, when the VOC concentration of the color group or the VOC concentration of the exhaust duct does not meet the target VOC concentration, the system uses fuzzy PID control to adjust the fresh air valve, the self-circulating return air valve, and the color group exhaust valve until the VOC concentration of the color group or the VOC concentration of the exhaust duct is adjusted to meet the target VOC concentration.

2. The automatic negative pressure control system according to claim 1, characterized in that, The PLC negative pressure automatic control subsystem includes: an input module, an automatic control module, and an output module connected in sequence; the input module includes: a negative pressure sensor unit, a target negative pressure value unit, a valve manual setting unit, and an output valve feedback unit; the automatic control module includes: a sampling and filtering unit, an input upper limit unit, an input lower limit unit, a sensor type unit, a sensor range unit, a data processing unit, a feedback comparison unit, a manual / automatic switching unit, a comparison calculation unit, a non-action area unit, a regulation intensity setting unit, a regulation time setting unit, a regulation cycle setting unit, a fuzzy control calculation unit, an alarm setting prompt unit, a data conversion unit, a data upper limit unit, a data lower limit unit, a proportional gain unit, and a fault judgment unit; the output module includes: an output actuator; The negative pressure sensor unit is connected to the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit, respectively; the sampling and filtering unit, the input upper limit unit, the input lower limit unit, the sensor type unit, and the sensor range unit are connected to the data processing unit, respectively; the target negative pressure value unit is connected to the data processing unit and the manual / automatic switching unit, respectively; the data processing unit is connected to the comparison processing unit; the comparison processing unit is connected to the inactive area unit, the adjustment intensity setting unit, the adjustment time setting unit, the adjustment cycle setting unit, the fuzzy control processing unit, and the alarm setting prompt unit, respectively; the inactive area unit, the adjustment intensity setting ... The given unit, the adjustment time given unit, the adjustment cycle given unit, the fuzzy control calculation unit, and the alarm setting prompt unit are all connected to the data conversion unit; the feedback comparison unit is connected to the data calculation unit and the data conversion unit; the valve manual given unit is connected to the manual / automatic switching unit; the manual / automatic switching unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the data conversion unit is connected to the upper data limit unit, the lower data limit unit, and the proportional gain unit; the output valve feedback unit is connected to the fault judgment unit; the upper data limit unit, the lower data limit unit, the proportional gain unit, and the fault judgment unit are all connected to the output actuator.

3. A method for implementing an automatic negative pressure control system, characterized in that, The method applied to the automatic negative pressure control system of claim 1 includes: The input information of the negative pressure sensor in the target system is collected, the input information is sampled and filtered, and the filtered input information is limited according to the preset upper and lower limits to obtain visualized data. Receive the target negative pressure value input from the host computer touch screen, calculate the difference between the target negative pressure value and the visualized data, and obtain the operating deviation; The operating deviation is calculated using fuzzy logic PID based on the preset non-action range, cycle, adjustment time, and adjustment range to obtain variable output; The variable output is subjected to upper and lower limit processing, and the limited variable output is sent to the valve actuator of the target system for negative pressure regulation. Then, the process returns to the step "collect input information from the negative pressure sensor in the target system, sample and filter the input information, and limit the filtered input information according to the preset upper and lower limits to obtain visualized data".

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