Negative pressure type pneumatic conveying system and conveying method

Abstract

The invention discloses a negative pressure type pneumatic conveying system and a conveying method. In the system, an air inlet is connected with a cyclone separator through a conveying pipeline, and a first air speed sensor, a pressure sensor, a first temperature sensor, an access port of an air powder mixer, a second air speed sensor and a second temperature sensor are sequentially arranged on the conveying pipeline; the stock bin, the weightlessness type feeder and the wind powder mixer are sequentially communicated into the conveying pipeline; an air outlet of the cyclone separator is connected with a negative pressure fan of the filter cartridge dust remover through a filter element of the filter cartridge dust remover, a dust collection barrel is arranged below a dust outlet of the cyclone separator, and a dust collection drawer is arranged below the filter element. The conveying pipeline is provided with at least one bending part, an auxiliary temperature sensor and an auxiliary wind speed sensor are arranged behind each bending part, and the auxiliary temperature sensors and the auxiliary wind speed sensors are both connected with the control unit. According to the pulverized coal conveying system, high-precision pulverized coal conveying can be achieved, the stability of the production process and the product quality can be improved, and the adaptability of the system is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mixed gas delivery, and particularly relates to a negative pressure pneumatic conveying system. BACKGROUND

[0002] In industrial production, the delivery of bulk or granular materials is an important link in the operation of a production line. Mechanical delivery methods such as belt conveyors and screw conveyors are widely used, but they are not suitable for complex spatial layouts or long-distance delivery scenarios, and have the following limitations:

[0003] Mechanical delivery equipment is bulky and has poor installation flexibility, making it difficult to install in a factory with limited space; mechanical components directly contact the material, which can cause equipment wear, material residue, and cross-contamination problems, especially for materials such as cement and coal dust that are prone to dust, and the leakage of dust during the delivery process can also cause environmental pollution and resource waste.

[0004] To solve these problems, pneumatic conveying technology has gradually emerged, which uses airflow as a carrier to achieve closed delivery, effectively reducing dust dispersion and material loss. However, existing pneumatic conveying systems are mainly divided into positive pressure and negative pressure types. The positive pressure system relies on a high-pressure fan to push the material, which is suitable for long-distance delivery, but has high requirements for pipe sealing, severe local wear, high energy consumption, and other problems, and when conveying materials such as coal dust, there is also the risk of oxidation, heat release, combustion, and even explosion.

[0005] The existing negative pressure pneumatic conveying system faces the following core problems in actual application: the separation efficiency and filter bottleneck are prominent, the traditional cyclone separator has insufficient capture efficiency for fine particles, and residual dust can easily penetrate the filter bag into the vacuum pump, causing abnormal wear of the pump body and secondary pollution, increasing operation and maintenance costs; lack of intelligent control, lacking real-time monitoring and feedback control of gas-solid two-phase flow parameters (such as concentration and flow rate), unable to dynamically optimize airflow parameters according to material characteristics, relying on manual experience adjustment, which can easily lead to material breakage or overload; these problems seriously restrict the reliability, economy, and scale application of the system, and need to be overcome through technological innovation. SUMMARY

[0006] In view of the problems in the background art, the present application provides a negative pressure pneumatic conveying system, which realizes quantitative, safe and stable conveying of dangerous materials such as coal powder, has high automation degree, can give early warning or alarm for air leakage, powder blocking and other problems, and can automatically take certain measures according to the actual situation to improve the safety of the system. The technical scheme comprises an air inlet, a wind speed sensor, a temperature sensor, a pressure sensor, a stock bin, a loss-in-weight feeder, a wind-powder mixer, a conveying pipeline, a cyclone separator, a dust collecting barrel, a filter cartridge dust collector, a negative pressure fan, a filter element, a dust collecting drawer and a control unit. The air inlet is connected with the cyclone separator through the conveying pipeline, and the first wind speed sensor, the pressure sensor, the first temperature sensor, the inlet of the wind-powder mixer, the second wind speed sensor and the second temperature sensor are sequentially arranged on the conveying pipeline. The stock bin, the loss-in-weight feeder and the wind-powder mixer are sequentially connected and communicated into the conveying pipeline. The air outlet of the cyclone separator is connected with the filter element of the filter cartridge dust collector and the negative pressure fan of the filter cartridge dust collector, and the dust collecting barrel is arranged below the dust outlet of the cyclone separator, and the dust collecting drawer is arranged below the filter element.

[0007] The first wind speed sensor, the second wind speed sensor, the pressure sensor, the loss-in-weight feeder and the filter cartridge dust collector are connected with the control unit.

[0008] At least one bending part is arranged on the conveying pipeline, and a secondary temperature sensor and a secondary wind speed sensor are arranged after each bending part. The secondary temperature sensor and the secondary wind speed sensor are connected with the control unit.

[0009] The air inlet is a section of reduced diameter pipeline, and a metal wire mesh is welded in the middle of the air inlet.

[0010] A conveying method of the negative pressure pneumatic conveying system is also provided, and the technical scheme comprises the following steps.

[0011] Step 1, initialization

[0012] After the system is started, the parameter initialization is performed, the target conveying amount Q0 is set, the measurement data of the wind speed sensor, the temperature sensor and the pressure sensor are initialized, the pipeline wind speed safety high and low threshold values are set, the fan speed is increased when the wind speed is lower than the lower limit value, and the fan speed is decreased when the wind speed is higher than the upper limit value. A reasonable gas-solid ratio range is set, the control unit automatically selects the middle value of the range, and the initial speed and air volume of the negative pressure fan 12 are calculated according to the target conveying amount.

[0013] Step 2, material quantification and start of conveying

[0014] After the initialization is completed, the feeder starts to run, the spiral conveyor is rotated at a certain speed according to the set target feeding amount, the coal powder is sent into the conveying pipeline through the discharge port, mixed with air in the wind-powder mixer, and then conveyed, and enters the conventional conveying stage.

[0015] Step 3, running and monitoring:

[0016] In the regular conveying stage, the system monitors the actual feeding amount in real time through the feeder, and automatically adjusts the speed of the conveyor when there is a deviation, so as to realize quantitative conveying.

[0017] In the regular conveying stage, the system continuously conducts safety monitoring and early warning, and the system enters step 3.1.

[0018] In the regular conveying stage, if the target conveying amount needs to be adjusted due to changes in production plans or other reasons, the target conveying amount is adjusted manually, and the system sends the target speed of the negative pressure fan to the target conveying amount to enter step 3.2.

[0019] The step 3.1, safety monitoring and early warning, comprises:

[0020] The control unit monitors the temperature and air speed changes in the coal powder conveying process in real time, and conducts:

[0021] Temperature monitoring and early warning: in the regular conveying stage, and after conveying for a period of time, if any temperature sensor shows a temperature rise of more than 5℃, it is determined that the temperature of the coal powder conveying section is abnormal, the control unit gives an early warning, and then increases the speed of the negative pressure fan to reduce the temperature. Continue for five minutes, if the effect is not obvious, continue to increase the speed, the range of wind speed increase is to ensure that the gas-solid ratio is within the set range, the single speed adjustment amplitude is 5%, when it increases to close to or reaches the upper limit value of the gas-solid ratio, the control unit sends an instruction to the feeder to reduce the conveying amount by 20%, if the effect is still not obvious, a temperature abnormality alarm is given to remind the operator or the patrol personnel to analyze and handle;

[0022] Air speed monitoring and early warning: in the regular conveying stage, if the speed of the negative pressure fan and the target feeding amount do not change, the air speed of any place changes by more than 10% compared with the regular conveying stage, which triggers an air speed abnormality early warning, the control unit sends an instruction to adjust the speed of the negative pressure fan in the opposite direction, the single speed adjustment amplitude is 3%, until the difference between the current air speed and the previous air speed is within 5%; after 5 minutes of adjustment, if the air speed at this place has not returned to within 5% of the regular conveying stage, an alarm is triggered to remind the operator or the patrol personnel to handle; if the air speed at a certain place changes by more than 20% compared with the regular conveying stage, the control unit first reduces the feeding amount, and then adjusts the speed of the negative pressure fan 12 in the opposite direction while triggering an air speed abnormality alarm, the single speed adjustment amplitude is also 3%; the purpose of triggering the air speed abnormality alarm is to remind the operator or the patrol personnel to analyze and handle the abnormal situation.

[0023] The step 3.2, fan air volume self-adaptive adjustment after adjusting the target conveying amount:

[0024] In the process of adjusting the target conveying amount, the control unit monitors the wind speed changes at each key node of the pipeline. If the wind speed change at a certain point exceeds 10% of the wind speed during the conventional conveying stage before reaching the target conveying amount, it is judged as an abnormal change. The system reverses the fan speed, and the single speed adjustment amplitude is 5%. The speed adjustment stops until the wind speed and the target feed amount before adjustment differ by less than 3%.

[0025] The beneficial effects of the present application are:

[0026] 1. Precise quantitative conveying, which can realize high-precision coal powder conveying, help improve the stability of production process and product quality, reduce the increase of production cost caused by conveying amount changes, and the conveying range is adjustable, which can be flexibly adjusted according to different production needs, suitable for various production scales and process requirements, and improves the adaptability of the system.

[0027] 2. Wide material adaptability, not only suitable for conveying dangerous materials such as coal powder and aluminum powder, but also suitable for conveying ordinary powdery and granular materials such as cement, graphite, catalyst particles and plastic particles, and can be applied in food, pharmaceutical, chemical and metallurgical industries.

[0028] 3. Air volume self-adaptive adjustment: can automatically follow the change of the feed amount, adjust the air volume of the fan, match the air volume and the coal powder amount in the conveying process, and maintain the gas-solid ratio within a reasonable range, which can not only ensure the conveying demand of coal powder, but also avoid the waste of energy caused by excessive air volume.

[0029] 4. Good safety and environmental protection: with temperature and wind speed warning function, real-time monitoring of the conveying state of the system, timely alarm when temperature or wind speed is abnormal, and automatic preliminary processing of abnormal problems, which can avoid equipment failure and safety accidents caused by problems such as excessive temperature and low wind speed, and ensure the safe and stable operation of the system. At the same time, the conveying system adopts a two-stage separation device of cyclone and filter cartridge, which can maximize the reduction of particulate matter content in the end exhaust gas, fully meet the environmental protection requirements, and is suitable for application in occasions with high environmental protection requirements. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a structure schematic diagram of an embodiment of the negative pressure type pneumatic conveying system of the present application.

[0031] Figure 2 It is a schematic diagram of the filter element in the embodiment of the present application.

[0032] Figure 3 It is a schematic diagram of the air-powder mixer in the embodiment of the present application.

[0033] Wherein, 1, air inlet, 5, silo, 6, loss type feeder, 7, air powder mixer, 8, conveying pipeline, 9, cyclone separator, 10, dust collecting barrel, 11, filter cartridge dust collector, 12, negative pressure fan, 13, filter core, 14, dust collecting drawer, 15, control unit, 2-1, first air speed sensor, 2-2, second air speed sensor, 2-3, first auxiliary air speed sensor, 2-4, second auxiliary air speed sensor, 3-1, first temperature sensor, 3-2, second temperature sensor, 3-3, first auxiliary temperature sensor, 3-4, second auxiliary temperature sensor. DETAILED DESCRIPTION

[0034] The application will be further described in detail below with reference to the accompanying drawings.

[0035] As Figure 1 shown in the embodiment of the application, comprising: air inlet 1, air speed sensor 2, temperature sensor 3, pressure sensor 4, silo 5, loss type feeder 6, air powder mixer 7, conveying pipeline 8, cyclone separator 9, dust collecting barrel 10, filter cartridge dust collector 11, negative pressure fan 12, filter core 13, dust collecting drawer 14 and control unit 15, wherein, the air inlet 1 is a section of diameter reducing pipeline, a metal wire mesh is welded in the middle, which can prevent larger volume of foreign matters from being sucked into the conveying pipeline to cause damage to other equipment components in the system, a butterfly valve is installed on the pipeline connected with the air inlet, and the opening degree of the butterfly valve can be adjusted to control the air volume entering the pipeline;

[0036] The air inlet 1 is connected with the cyclone separator 9 through the conveying pipeline 8, and the first air speed sensor 2-1, the pressure sensor 4, the first temperature sensor 3-1, the inlet of the air powder mixer 7, the second air speed sensor 2-2 and the second temperature sensor 3-2 are sequentially arranged on the conveying pipeline 8; the silo 5, the loss type feeder 6 and the air powder mixer 7 are sequentially connected and communicated into the conveying pipeline 8; the air outlet of the cyclone separator 9 is connected with the filter core 13 of the filter cartridge dust collector 11 and the negative pressure fan 12 of the filter cartridge dust collector 11, the dust collecting barrel 10 is arranged below the dust outlet of the cyclone separator 9, and the dust collecting drawer 14 is arranged below the filter core 13; the pressure sensor 4, the loss type feeder 6 and the filter cartridge dust collector 11 are connected with the control unit 15;

[0037] If the conveying pipeline 8 is provided with a bend, a secondary temperature sensor and a secondary wind speed sensor are provided after each bend; in this embodiment, a first bend, a first secondary temperature sensor 3-3, a first secondary wind speed sensor 2-3, a second bend, a second secondary temperature sensor 3-4 and a second secondary wind speed sensor 2-4 are sequentially provided on the conveying pipeline 8 between the second temperature sensor 3-2 and the cyclone separator 9; all the wind speed sensors 2 and the temperature sensors 3 are connected to the control unit 15; all the secondary temperature sensors (the first secondary temperature sensor 3-3 and the second secondary temperature sensor 3-4) and all the secondary wind speed sensors (the first secondary wind speed sensor 2-3 and the second secondary wind speed sensor 2-4) are connected to the control unit 15;

[0038] The wind speed sensors are installed at key nodes of the conveying pipeline, including intermediate positions of horizontal and vertical sections and positions away from the bends, and the wind speed in the entire conveying pipeline is monitored through the wind speed sensors, so as to facilitate early warning of various abnormal conditions and ensure the safety and stability of the conveying process. The temperature sensor 3 is installed at the air inlet section before the wind-powder mixer, and the measurement value can reflect the conveying capacity of the system and its change in real time.

[0039] The pressure sensors are also installed at multiple positions, one at each of the air inlet section, the wind-powder mixer and the position three times the pipe diameter downstream of the bend. The temperature sensor at the air inlet section can provide a temperature reference, and the temperature sensor after the wind-powder mixer can monitor the temperature at the initial mixing stage and provide early warning of friction overheating and spontaneous combustion. The temperature sensor downstream of the bend has the following functions:

[0040] (1) Monitoring the heat generated by particle collision and friction. After passing through the bend, the coal powder will impact the outer pipe wall under the action of centrifugal force, and the kinetic energy will be converted into heat energy, causing the temperature at this position to differ from that of the air inlet section by 2-5°C, which is related to the pipe diameter and conveying capacity. If the temperature difference is greater than 10°C, it indicates that the friction is relatively severe, and long-term conveying may cause serious wear to the pipe wall.

[0041] (2) Early warning of blockage. Before blockage, there will be obvious signs. The accumulation of coal powder after the bend will narrow the airflow passage, increase the local flow rate, intensify the turbulent friction, and eventually cause the temperature at this position to rise sharply. The coal powder in the particle stagnation zone will also cause the temperature to rise due to continuous sliding friction, and the heat will gradually accumulate. Preventing blockage can reduce the risk of spontaneous combustion. When coal powder accumulates at a certain position, it will undergo slow oxidation, which continuously releases heat. If not discovered in time, it may cause the coal powder to spontaneously combust.

[0042] In the embodiment, the weighing feeder mainly comprises a hopper, a scale body, a horizontal screw conveyor and electrical control components. The hopper is a weighing container, which can be connected with a coal powder storage bin. A discharge valve capable of automatic opening and closing is arranged on a connecting pipeline. When the weight of the coal powder in the hopper is lower than a lower limit value, the discharge valve is opened to automatically add the coal powder, so as to realize continuous feeding. The scale body is installed on the hopper to measure the weight of the coal powder in the hopper in real time and calculate the actual feeding amount. The control components adjust the rotating speed of the conveyor according to the difference between the actual feeding amount and a target feeding amount, so that high-precision continuous feeding can be realized. The target feeding amount can be adjusted according to actual production requirements. After the target feeding amount is changed, the rotating speed of the screw conveyor is automatically adjusted to make the actual feeding amount close to the target value. The conveying process is flexible and adjustable.

[0043] The discharge outlet of the weighing feeder is connected with a wind-powder mixer. The coal powder conveyed by the screw conveyor enters the wind-powder mixer through the discharge outlet, is mixed with air in the horizontal pipe section of the mixer and the conveying pipeline, and is conveyed under the negative pressure generated by the end fan.

[0044] In the embodiment, the cyclone separator is a primary separation device, and the separation efficiency can reach about 80%. The gas-solid mixture enters the cyclone cylinder along the tangential direction of the inlet of the separator. The coal powder is thrown to the inner wall of the cyclone cylinder under the action of centrifugal force, loses kinetic energy, and then falls into the dust collection container under the action of gravity. The unseparated coal powder is conveyed to the filter cartridge dust collector through the top outlet.

[0045] The filter cartridge dust collector is a secondary separation device, which can separate very fine coal powder particles with a particle size of several microns. In theory, almost all coal powder particles can be separated, so that the discharged gas does not contain coal powder, which fully meets the requirements of environmental protection. The filter cartridge dust collector is a vertical cabinet. The upper half is a negative pressure fan, and the lower half is a filter core. The number of filter cores can be selected according to requirements, and the minimum number is two. During the working process, at least one filter core can be ensured to be in a normal working state when one filter core is pulsed cleaned and blown. The negative pressure fan is provided with a frequency converter, which can be self-adaptively adjusted according to the conveying amount and speed under the action of the control unit, so that the speed in the conveying pipeline is in the range of 15-25 m / s. The speed range can be set by itself.

[0046] In this embodiment, the control unit is the core component of the negative pressure pneumatic conveying system, mainly including a programmable logic controller (PLC) and an input / output card, which can receive measurement signals of all sensors, actual conveying capacity of the weighing feeder, frequency of the negative pressure fan and other data, monitor the state during the entire conveying process, and can give early warning and automatically process abnormal wind speed and temperature changes, adjust the wind speed, the feeding amount or directly stop according to different situations, effectively improve the safety and stability of the system operation, automatically adjust the wind speed according to the change of the target feeding amount, so that the gas-solid ratio is within a suitable range, and the system energy consumption is reduced on the premise of ensuring the conveying capacity.

[0047] The negative pressure pneumatic conveying method used in this embodiment includes the following steps:

[0048] Step 1, initialization:

[0049] After the system is started, the parameters are initialized, the target conveying capacity Q0 is set, the measurement data of the wind speed sensor, the temperature sensor and the pressure sensor are initialized, the high and low threshold values of the pipeline wind speed are set (to avoid that the material is deposited due to too low wind speed, which cannot meet the normal conveying requirements, and the material will cause excessive wear or other problems to the conveying pipeline when the wind speed is too high), the fan speed is increased when the wind speed is lower than the lower limit value, and the fan speed is reduced when the wind speed is higher than the upper limit value. Set a reasonable gas-solid ratio range, and the control unit automatically selects the middle value of the range to calculate the initial speed and air volume of the negative pressure fan 12 according to the target conveying capacity.

[0050] Step 2, material quantification and start conveying:

[0051] After initialization, the feeder starts to run, and the screw conveyor rotates at a certain speed according to the set target feeding amount, so that the pulverized coal is sent into the conveying pipeline through the discharge port, mixed with air in the air-powder mixer, and then conveyed into the conventional conveying stage.

[0052] Step 3, running and monitoring:

[0053] In the conventional conveying stage, the system monitors the actual feeding amount in real time through the feeder, and automatically adjusts the speed of the conveyor when deviation occurs to realize quantitative conveying.

[0054] In the conventional conveying stage, the system continuously monitors and gives early warning, and the system enters step 3.1.

[0055] In the conventional conveying stage, if the target conveying capacity needs to be adjusted due to changes in production plans or other reasons, the target conveying capacity is adjusted by manual operation, the system sends the target speed required to adjust the target conveying capacity to the negative pressure fan, and then enters step 3.2.

[0056] Step 3.1, safety monitoring and early warning includes:

[0057] The control unit monitors the state parameters in real time during the coal powder conveying process, mainly the temperature and wind speed changes of each key node of the conveying pipeline;

[0058] Temperature monitoring and early warning: in the conventional conveying stage, and after conveying for a period of time, if any temperature sensor shows significant temperature rise (5°C or more than the conventional conveying stage), it is determined that the temperature of the coal powder conveying section is abnormal, the control unit gives a warning, then increases the speed of the negative pressure fan 12 to reduce the temperature, and continues for five minutes. If the effect is not obvious, continue to increase the speed, the range of wind speed increase is to ensure that the gas-solid ratio is within the set range, the single speed adjustment amplitude is 5%, when it approaches or reaches the upper limit of the gas-solid ratio, the control unit sends a command to the feeder to reduce the conveying capacity by 20%, if the effect is still not obvious, a temperature abnormality alarm is triggered to remind the operator or the patrol personnel to analyze and handle.

[0059] Wind speed monitoring and early warning: in the conventional conveying stage, if the speed of the negative pressure fan 12 and the target feed amount do not change, the wind speed change at a certain place exceeds 10% compared with the conventional conveying stage, triggering a wind speed abnormality early warning, the control unit sends a command to adjust the speed of the negative pressure fan 12 in the opposite direction, that is, if the wind speed at a certain place increases by more than 10% compared with the conventional conveying stage, the fan speed is reduced, otherwise the fan speed is increased, the single speed adjustment amplitude is 3%, until the difference between the current wind speed and the previous wind speed at this place is within 5%; if the wind speed at this place has not returned to within 5% of the conventional conveying stage after 5 minutes of adjustment, an alarm is triggered to remind the operator or the patrol personnel to handle; if the wind speed change at a certain place exceeds 20%, the control unit first reduces the feed amount, then adjusts the speed of the negative pressure fan 12 in the opposite direction while triggering a wind speed abnormality alarm, the single speed adjustment amplitude is also 3%; the purpose of triggering a wind speed abnormality alarm is to remind the operator or the patrol personnel to analyze and handle the abnormal situation.

[0060] In this embodiment, wind speed monitoring and warning are performed during the normal conveying phase: if the speed of the negative pressure fan 12 and the target feed rate remain unchanged, and the wind speed at a certain location fluctuates by 10% or more, the wind speed abnormality warning is triggered. The control unit sends a command to automatically adjust the speed of the negative pressure fan 12 in increments of 3% until the difference between the wind speed and the previous value is within 5%. For example, if the wind speed at a certain location in the pipeline is originally 20 m / s and suddenly fluctuates to 22 m / s, the wind speed abnormality warning is triggered. The control unit sends a command to automatically adjust the speed of the negative pressure fan 12 in increments of 3%. If the fan speed is currently 1000 r / min, it is reduced to 970 r / min. If the wind speed at that location does not return to the range of 19-21 m / s after 1 minute of speed adjustment, the speed is further reduced until the wind speed difference is within 5%. If the wind speed does not reach this range after 5 minutes of adjustment, an alarm is triggered, alerting the operator or patrol personnel to take action. If the wind speed changes by 20%, the control unit first reduces the feed rate, then adjusts the wind speed, and simultaneously triggers an abnormal wind speed alarm, alerting operators or inspectors to analyze and address the abnormality. The specific air volume change required to trigger the wind speed warning, the single speed adjustment range, and the adjustment effect can be adjusted appropriately according to different application scenarios to achieve better warning effects, while also avoiding frequent wind speed adjustments and reducing the frequency of fan speed adjustments.

[0061] Step 3.2: Adaptive adjustment of fan air volume after adjusting target delivery volume:

[0062] During the process of wind speed changes after adjusting the target delivery volume, the control unit monitors the wind speed changes at each key node of the pipeline. If the wind speed change at a certain point exceeds 10% of the wind speed in the normal delivery stage before reaching the target delivery volume, it is judged as an abnormal change, and the system changes the fan speed in the opposite direction. For example, when it is found that the wind speed decreases by 10.1%, the fan speed is increased. The single speed adjustment range is 5% until the wind speed and the target feed rate are within 3% before adjustment. The speed adjustment is stopped. Otherwise, the fan speed is reduced until the wind speed reaches the corresponding range.

Claims

1. A negative pressure pneumatic conveying system, characterized in that: include: An air inlet (1), a wind speed sensor (2), a temperature sensor (3), a pressure sensor (4), a silo (5), a loss-in-weight feeder (6), an air-powder mixer (7), a conveying pipeline (8), a cyclone separator (9), a dust collecting bucket (10), a cartridge dust collector (11), a negative pressure fan (12), a filter element (13), a dust collecting drawer (14) and a control unit (15), wherein the air inlet (1) is connected to the cyclone separator (9) via the conveying pipeline (8), and a first wind speed sensor (2-1), a pressure sensor ( 4), a first temperature sensor (3-1), an access port of an air-powder mixer (7), a second wind speed sensor (2-2) and a second temperature sensor (3-2); a hopper (5), a loss-in-weight feeder (6) and an air-powder mixer (7) are sequentially connected and passed into a conveying pipeline (8); an air outlet of a cyclone separator (9) is connected to a negative pressure fan (12) of a cartridge dust collector (11) through a filter element (13) of a cartridge dust collector (11); a dust collecting bucket (10) is provided below the dust outlet of the cyclone separator (9), and a dust collecting drawer (14) is provided below the filter element (13); The first wind speed sensor (2-1), the second wind speed sensor (2-2), the pressure sensor (4), the loss-in-weight feeder (6) and the cartridge dust collector (11) are all connected to the control unit (15).

2. A negative pressure pneumatic conveying system according to claim 1, characterized in that: At least one bending portion is provided on the conveying pipeline (8), and an auxiliary temperature sensor and an auxiliary wind speed sensor are provided after each bending portion. The auxiliary temperature sensor and the auxiliary wind speed sensor are both connected to the control unit (15).

3. A negative pressure pneumatic conveying system according to claim 1, characterized in that: The air inlet (1) is a section of reduced diameter pipe, and a metal wire mesh is welded in the middle of the air inlet (1).

4. A conveying method of the negative pressure pneumatic conveying system according to claim 1, characterized in that: include: Step 1. Initialization: After the system starts, it initializes its parameters, sets the target delivery volume Q0, initializes the measurement data of the wind speed sensor, temperature sensor, and pressure sensor, and sets the upper and lower safety thresholds for duct wind speed. When the wind speed falls below the lower limit, the fan speed is increased, and when it exceeds the upper limit, the fan speed is reduced. A reasonable air-to-solid ratio range is set, and the control unit automatically selects the middle value within this range and calculates the initial speed and air volume of the negative pressure fan based on the target delivery volume. Step 2: Quantify the material and start conveying: After initialization is completed, the feeder starts to run. According to the set target feeding amount, the screw conveyor rotates at a certain speed, and the pulverized coal is sent into the conveying pipeline through the discharge port. After being mixed with air in the air-powder mixer, it is conveyed and enters the normal conveying stage. Step 3: Run and monitor: During the regular conveying phase, the system monitors the actual feeding amount in real time through the feeder, and automatically adjusts the conveyor speed when deviation occurs to achieve quantitative conveying. During the regular delivery phase, the system continues to perform safety monitoring and early warning, and then proceeds to step 3.1; During the normal conveying phase, if the production plan changes or the target conveying volume needs to be adjusted due to other reasons, the target conveying volume is adjusted manually. The system sends the target speed for the target conveying volume to the negative pressure fan and then proceeds to step 3.

2.

5. The method for conveying a negative pressure pneumatic conveying system according to claim 4, characterized in that: The step 3.1, safety monitoring and early warning, includes: The control unit monitors the temperature and wind speed changes during the pulverized coal transportation process in real time and performs: Temperature monitoring and early warning: During the normal conveying phase and after a period of conveying, if any temperature sensor shows a temperature rise of more than 5°C, it is determined that the temperature of the pulverized coal conveying section is abnormal. The control unit will issue an early warning and then increase the speed of the negative pressure fan to cool down the temperature for five minutes. If the effect is not obvious, the speed will be increased again. The range of wind speed increase is to ensure that the gas-solid ratio is within the set range. The single speed adjustment range is 5%. When it is increased to approach or reach the upper limit of the gas-solid ratio, the control unit will send a command to the feeder to reduce the conveying volume by 20%. If the effect is still not obvious, a temperature abnormality alarm will be issued to remind the operator or patrol personnel to analyze and deal with it; Wind speed monitoring and early warning: When entering the normal conveying stage, if the speed of the negative pressure fan and the target feed rate remain unchanged, the wind speed at any point changes by more than 10% compared with the normal conveying stage, triggering a wind speed abnormality early warning, and the control unit sends an instruction to reversely adjust the speed of the negative pressure fan, with a single speed adjustment range of 3%, until the difference between the current wind speed here and the previous wind speed is within 5%; after 5 minutes of adjustment, if the wind speed here has not returned to the 5% range of the normal conveying stage, an alarm is triggered to remind the operator or patrol personnel to deal with it; if the wind speed at a certain point changes by more than 20% compared with the normal conveying stage, the control unit first reduces the feed rate, and then adjusts the speed of the negative pressure fan in the opposite direction while triggering the wind speed abnormality alarm, with a single speed adjustment range of 3%; the purpose of triggering the wind speed abnormality alarm is to remind the operator or patrol personnel to analyze and deal with the abnormal situation.

6. The method for conveying a negative pressure pneumatic conveying system according to claim 4, characterized in that: In step 3.2, the fan air volume is adaptively adjusted after adjusting the target delivery volume: During the process of wind speed changes after adjusting the target delivery rate, the control unit monitors the wind speed changes at each key node of the pipeline. If the wind speed change at a certain point exceeds 10% of the wind speed in the normal delivery stage before reaching the target delivery rate, it is judged as an abnormal change. The system changes the fan speed in the opposite direction, with a single speed adjustment range of 5%. The speed adjustment is stopped until the wind speed and the target feed rate are within 3% of each other before adjustment.

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