A method for controlling air volume of a bag filter

Abstract

The application provides a kind of air volume control method of filter bag dust collector, belongs to dust collector technical field.It solves the problem of existing dust collector ash control is not perfect, influence dust removal effect.This filter bag dust collector air volume control method includes: through control panel selects user demand air volume, controller obtains corresponding fan current reference value according to user demand air volume and controls frequency converter to drive fan operation according to user demand air volume;Real-time driving current of fan is obtained by current sampling circuit;The current difference of the two is obtained by difference calculation of real-time driving current and the obtained fan current reference value by controller;The frequency adjustment value is output to the frequency converter according to the obtained current difference by the controller, and the frequency converter adjusts the fan operating speed according to the frequency adjustment value after receiving the frequency adjustment value, so that the real-time driving current is maintained at the fan current reference value.The application can effectively reduce the ash removal frequency of dust collector and improve the efficiency.

Description

Technical Field

[0001] This invention belongs to the field of dust collector technology and relates to a method for controlling the air volume of a filter bag dust collector. Background Technology

[0002] Dust is generated in many processes during industrial production, such as grinding with abrasive wheels and polishing with abrasive belts. Dust collectors, as devices that separate dust from flue gas, are common industrial equipment in boiler manufacturing, polishing, and other industrial production processes. Dust collectors can be classified according to their working principle into bag filters, granular bed filters, electrostatic precipitators, magnetic precipitators, etc.

[0003] Baghouse dust collectors are made of woven filter cloth or non-woven felt, utilizing the filtration effect of the fibrous fabric to filter dust-laden gas. A fan or pump draws air out of the machine, creating a pressure difference—a negative pressure—better than the external pressure. When dust-laden gas enters the baghouse, larger, heavier dust particles settle due to gravity and fall into the ash hopper. Gas containing finer dust particles is purified by trapping the dust as it passes through the filter media. However, during the dust collection process, dust gradually accumulates on the surface of the filter bags due to sieving, collision, retention, diffusion, and electrostatic effects. As dust accumulates, the airflow channel narrows, increasing the resistance of the filter bags to airflow and significantly reducing the airflow volume of the dust collection system. Ultimately, this severely affects the dust collection efficiency of the filter bags. Therefore, filter bags need to be cleaned regularly. While regular cleaning is simple, it is not economical. If the time interval is too long, too much dust will accumulate on the filter bags, resulting in too large a pressure difference and failing to achieve a good dust removal effect. If the interval is too short, too many cleanings will be required, reducing the lifespan of the filter bags. Moreover, too high a cleaning frequency will also affect production efficiency. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a method for controlling the airflow of a bag filter dust collector. The actual technical problem to be solved is: how to reduce the dust collector cleaning frequency.

[0005] The objective of this invention can be achieved through the following technical solution: a method for controlling the airflow of a bag filter dust collector, wherein the bag filter dust collector includes a housing, on which a dust collector inlet and a dust collector outlet are provided, a filter bag is fixedly connected inside the housing, the dust collector inlet is directly connected to an external dust collection pipe, the dust collector outlet is connected to a fan through a duct, the fan is connected to a frequency converter, a control panel is provided on the housing, the control panel contains a controller, the controller is connected to the frequency converter, and the airflow control method includes the following steps:

[0006] Step 1: Select the user's required air volume through the control panel. The controller obtains the corresponding fan current reference value based on the user's required air volume and controls the frequency converter to drive the fan to run according to the user's required air volume.

[0007] Step 2: Obtain the real-time drive current of the fan through the current sampling circuit; calculate the difference between the real-time drive current and the obtained fan current reference value through the controller to obtain the current difference between the two.

[0008] Step 3: The controller calculates and outputs a frequency adjustment value to the frequency converter based on the current difference obtained in Step 2. After receiving the frequency adjustment value, the frequency converter adjusts the fan speed according to the frequency adjustment value.

[0009] Step four, repeat steps two and three above to keep the real-time drive current at the wind turbine current reference value.

[0010] When using this airflow control method to control a bag filter dust collector, the user first selects the required airflow volume via the control panel based on the actual airflow demand. The controller then obtains a corresponding fan current reference value based on this demand and controls the frequency converter to drive the fan accordingly. This fan current reference value is preset, or it can be obtained by recording the initial fan current value at the corresponding airflow volume during the first use of the bag filter dust collector and using it as the fan current reference value. After the fan operates according to the user's required airflow volume, the air inside the dust collector housing is drawn out, creating a negative pressure inside and outside the dust collector. This forces dust-laden air to enter the dust collector housing through the external suction pipe, where it is filtered by the filter bags before being discharged clean air from the dust collector outlet. During this dust removal process, fine dust particles gradually accumulate on the surface of the filter bags, causing the ventilation airflow to gradually decrease. This solution uses a current sampling circuit to collect the real-time drive current of the fan during the dust removal process and transmits it to the controller. After receiving the real-time drive current, the controller calculates the difference between the real-time drive current and the pre-acquired fan current reference value. Then, based on the obtained current difference, it outputs a frequency adjustment value to the frequency converter. After receiving the frequency adjustment value, the frequency converter adjusts the fan speed according to the frequency adjustment value so that the real-time drive current can be restored to the fan current reference value. This ensures that the ventilation volume of the filter bag is stable and basically maintained at the original ventilation volume, which can blow away the blockage on the filter bag, reduce the ventilation resistance of the filter bag, avoid the continuous blockage of the filter bag by dust, improve the dust removal effect of the dust collector, and also extend the dust removal time of the filter bag, extend the time of the dust collector entering the dust cleaning state, and effectively reduce the dust collector cleaning frequency.

[0011] If the current does not return to the fan current reference value, the inverter output frequency will continue to be adjusted according to the difference until the real-time drive current reaches the fan current reference value, so that the air volume of the filter bag ventilation remains basically stable, ensuring that the dust collector can maintain a good dust removal effect for a long time, thereby reducing the dust collector cleaning frequency.

[0012] In the aforementioned airflow control method for a bag filter dust collector, in step one, the control panel is equipped with multiple airflow selection buttons for users to choose different airflow volumes to meet their needs. Each airflow selection button is connected to the controller. The airflow selection buttons cater to users' requirements for the dust collector in various scenarios.

[0013] In the aforementioned airflow control method for baghouse dust collectors, in step one, the controller pre-stores a control table that corresponds one-to-one with the user's required airflow, the fan current reference value, and the inverter output frequency. Upon receiving the user's required airflow, the controller looks up the corresponding fan current reference value and inverter output frequency in the control table, thereby controlling the inverter to drive the fan according to its output frequency. The values ​​set in the control table are obtained through testing on multiple baghouse dust collectors; the precise setting of the control table provides accuracy for subsequent airflow adjustments.

[0014] In the aforementioned airflow control method for a bag filter dust collector, in step two, the current sampling circuit includes a current transformer, resistors R1 and R2, and operational amplifier U1. The primary winding of the current transformer is connected in series between the fan and the frequency converter. One end of the secondary winding of the current transformer is connected to one end of resistors R1 and R2. The other end of the secondary winding of the current transformer and the other end of resistor R1 are grounded. The other end of resistor R2 is connected to the non-inverting input of operational amplifier U1. The inverting input of operational amplifier U1 is connected to its output. The output of operational amplifier U1 is connected to the controller. The current value detected by the current transformer is processed by resistors R1 and R2 and operational amplifier U1 and then transmitted to the controller. The controller then adjusts the fan speed according to the current signal to keep the dust collector's airflow essentially constant.

[0015] In the aforementioned airflow control method for the bag filter dust collector, in step three, the frequency adjustment value is obtained by the controller through fuzzy PID control based on the current difference obtained in step two. The frequency adjustment value is obtained using fuzzy PID control calculations, which effectively improves the accuracy of the obtained frequency adjustment value, thereby ensuring that the airflow of the filter bag remains essentially constant, improving dust removal efficiency, and reducing the frequency of dust collector cleaning.

[0016] In the above-mentioned airflow control method for filter bag dust collectors, the fuzzy PID control operation in step three includes:

[0017] Obtain the current difference calculated from the real-time drive current and the fan current reference value;

[0018] The rate of change of the current difference is obtained by calculating the rate of change of the current difference compared to the current difference obtained at the previous moment;

[0019] The current difference and the rate of change of the current difference are subjected to fuzzy control. The output is found according to the fuzzy rule table to optimize and obtain the three parameters Kp, Ki and Kd in real time. Then, the current difference and the three parameters Kp, Ki and Kd are subjected to PID control to calculate and output a frequency adjustment value.

[0020] In the above-mentioned airflow control method for filter bag dust collectors, in step three, the operation of the controller calculating and outputting a frequency adjustment value to the frequency converter based on the current difference obtained in step two includes:

[0021] A frequency regulation control table that pre-stores the current difference and frequency regulation value in the controller is used to regulate the frequency regulation value.

[0022] After receiving the current difference, the controller queries the frequency regulation control table to find the corresponding frequency regulation value and outputs it to the frequency converter. The frequency regulation control table is obtained through numerous prior tests, and the data in the table effectively ensures accuracy, providing a guarantee for precise adjustment of the frequency converter's output frequency.

[0023] In the above-mentioned airflow control method for filter bag dust collectors, step three further includes the following steps:

[0024] The maximum frequency output value of the frequency converter is pre-stored in the controller;

[0025] After the controller calculates and outputs a frequency adjustment value, it compares the adjusted inverter output frequency with the inverter's maximum frequency output value. When the inverter output frequency is greater than the inverter's maximum frequency output value, it controls the inverter to stop working and sends an alarm signal to the control panel.

[0026] The control panel provides audible and / or visual alarms to remind users to perform timely dust removal. This ensures the safety of the frequency converter's operation and provides timely reminders for dust removal, guaranteeing that the dust collector remains in an effective dust removal state.

[0027] Compared with existing technologies, the airflow control method of this filter bag dust collector maintains the real-time drive current at the fan current reference value during control. This operation ensures that the airflow of the filter bag remains basically constant, avoiding the problem of reduced air intake efficiency caused by dust accumulation. Moreover, the airflow of the filter bag can be maintained at the original airflow level, which can blow away the blockage on the filter bag to a certain extent, reduce the airflow resistance of the filter bag, and prevent the continuous accumulation of dust on the surface of the filter bag, thus avoiding dust blockage. This improves the dust removal effect of the dust collector and also extends the dust removal time of the filter bag, effectively reducing the dust collector cleaning frequency. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the filter bag dust collector of the present invention.

[0029] Figure 2 This is a schematic diagram of the control structure of Embodiment 1 of the present invention.

[0030] In the diagram, 1 is the housing; 11 is the dust collector inlet; 12 is the dust collector outlet; 2 is the filter bag; 3 is the external dust collection pipe; 4 is the duct; 5 is the fan; 6 is the frequency converter; 7 is the control panel; 71 is the air volume selection button; 8 is the controller; 9 is the current sampling circuit; and 91 is the current transformer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] Example 1:

[0033] The airflow control method for this bag filter dust collector is mainly applied to bag filter dust collectors, such as... Figure 1 As shown, the bag filter dust collector includes a housing 1, on which a dust collector inlet 11 and a dust collector outlet 12 are provided. Filter bags 2 are fixedly connected inside the housing 1. The dust collector inlet 11 is directly connected to an external dust collection pipe 43. The dust collector outlet 12 is connected to a fan 5 through a duct 4. The fan 5 is connected to a frequency converter 6. A control panel 7 is provided on the housing 1. The control panel 7 contains a controller 8, which is connected to the frequency converter 6. The control panel 7 and the controller 8 are connected in... Figure 1 Not marked in the text.

[0034] This airflow control method is based on Figure 2The various components are implemented in the control panel 7, which has multiple airflow selection buttons 71 for users to choose different airflow volumes according to their needs. Each airflow selection button 71 is connected to the controller 8. The current sampling circuit 9 includes a current transformer 91, resistors R1 and R2, and an operational amplifier U1. The primary winding of the current transformer 91 is connected in series between the fan 5 and the frequency converter 6. One end of the secondary winding of the current transformer 91 is connected to one end of resistors R1 and R2. The other end of the secondary winding of the current transformer 91 and the other end of resistor R1 are grounded. The other end of resistor R2 is connected to the non-inverting input of the operational amplifier U1. The inverting input of the operational amplifier U1 is connected to the output of the operational amplifier U1. The output of the operational amplifier U1 is connected to the controller 8 to supply real-time drive current to the controller 8. The controller 8 can be a microcontroller or a PLC.

[0035] When using this airflow control method to control the filter bag dust collector, firstly, based on the user's actual demand for dust removal airflow, the user selects the required airflow through the airflow selection button 71 on the control panel 7. The controller 8 obtains the corresponding fan current reference value based on the user's required airflow and controls the frequency converter 6 to drive the fan 5 to operate according to the user's required airflow. The specific operation is as follows:

[0036] The controller 8 has a pre-stored control table that corresponds one-to-one with the user's required air volume, the fan current reference value, and the inverter output frequency. After receiving the user's required air volume, the controller 8 looks up the corresponding fan current reference value and inverter output frequency through the control table, thereby controlling the inverter 6 to drive the fan 5 to operate according to the inverter output frequency.

[0037] After the fan 5 operates according to the user's required airflow, the air inside the dust collector housing 1 is drawn out, creating a negative pressure inside and outside the dust collector. This allows the dust-laden air to enter the dust collector housing 1 through the external suction pipe 43, where it is filtered by the filter bags 2 before being output as clean air from the dust collector outlet 12. During this dust removal process, fine dust particles gradually accumulate on the surface of the filter bags 2, causing the ventilation airflow to gradually decrease and reducing the dust removal efficiency. To address this issue, the current sampling circuit 9 in this solution acquires the real-time drive current of the fan 5 and sends it to the controller 8 while the filter bag dust collector is operating. Upon receiving this real-time drive current, the controller 8 calculates the difference between the real-time drive current and the acquired fan current reference value. Then, the controller 8 uses fuzzy PID control to calculate the current difference and outputs a frequency adjustment value to the frequency converter 6. The specific calculation operation is as follows:

[0038] First, the current difference is calculated by comparing the real-time drive current with the fan current reference value. Then, the rate of change of the current difference is calculated by comparing it with the current difference obtained at the previous moment. Finally, fuzzy control is applied to the current difference and its rate of change. Based on the fuzzy rule table, the output quantity is found to optimize and derive the three parameters Kp, Ki, and Kd in real time. Then, PID control is applied to the current difference and the three parameters Kp, Ki, and Kd to calculate and output a frequency adjustment value. After receiving the frequency adjustment value, the frequency converter 6 adjusts the fan speed 5 according to this value to maintain the real-time drive current at the fan current reference value. This ensures stable ventilation of the filter bag 2, preventing dust blockage of the filter bag 2 due to reduced airflow, improving the dust collector's dust removal efficiency, and extending the dust removal time of the filter bag 2, thus extending the time the dust collector enters the cleaning state and effectively reducing the dust collector's cleaning frequency. If the current does not return to the fan current reference value after adjustment by frequency converter 6, the output frequency of frequency converter 6 will continue to be adjusted according to the difference until the real-time drive current reaches the fan current reference value, so that the ventilation volume of filter bag 2 remains basically stable, ensuring that the dust collector can maintain a good dust removal effect for a long time, thereby reducing the dust collector cleaning frequency.

[0039] To further improve the safety of the filter bag dust collector, the following operations are also included when controlling the frequency converter 6: the maximum frequency output value of the frequency converter is pre-stored in the controller 8; after the controller 8 calculates and outputs a frequency adjustment value, it compares the adjusted frequency converter output frequency with the maximum frequency output value of the frequency converter; when the frequency converter output frequency is greater than the maximum frequency output value, the frequency converter 6 is controlled to stop working and an alarm signal is sent to the control panel 7; the control panel 7 then provides an audible alarm and / or visual alarm to remind the user to perform timely dust removal or automatically enter the dust removal program.

[0040] Example 2:

[0041] The technical solution in this embodiment is basically the same as that in Embodiment 1, except that the frequency adjustment value is obtained in the following way:

[0042] A frequency regulation control table that corresponds one-to-one between current difference and frequency regulation value is pre-stored in controller 8;

[0043] After receiving the current difference, controller 8 queries the frequency adjustment control table to find the corresponding frequency adjustment value and outputs it to inverter 6. The frequency adjustment control table is obtained through numerous prior tests, and the data in the table effectively ensures accuracy, providing a guarantee for precise adjustment of the inverter's output frequency.

[0044] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for controlling the airflow of a bag filter dust collector, wherein the bag filter dust collector includes a housing (1), the housing (1) is provided with a dust collector inlet (11) and a dust collector outlet (12), a filter bag (2) is fixedly connected inside the housing (1), the dust collector inlet (11) is directly connected to an external dust collection pipe (3), the dust collector outlet (12) is connected to a fan (5) through a duct (4), the fan (5) is connected to a frequency converter (6), a control panel (7) is provided on the housing (1), the control panel (7) is provided with a controller (8), the controller (8) is connected to the frequency converter (6), characterized in that, The air volume control method includes the following steps: Step 1: Select the user's required air volume through the control panel (7). The controller (8) obtains the corresponding fan current reference value according to the user's required air volume and controls the frequency converter (6) to drive the fan (5) to run according to the user's required air volume. Step 2: Obtain the real-time drive current of the fan (5) through the current sampling circuit (9); calculate the difference between the real-time drive current and the obtained fan current reference value through the controller (8) to obtain the current difference between the two. Step 3: The controller (8) calculates and outputs a frequency adjustment value to the inverter (6) based on the current difference obtained in step 2. After receiving the frequency adjustment value, the inverter (6) adjusts the operating speed of the fan (5) according to the frequency adjustment value. Step four, repeat steps two and three above to keep the real-time drive current at the wind turbine current reference value.

2. The airflow control method for a filter bag dust collector according to claim 1, characterized in that, In step one, the control panel (7) is provided with multiple air volume selection buttons (71) for users to select different sizes of air volume according to their needs. Each air volume selection button (71) is connected to the controller (8).

3. The airflow control method for a filter bag dust collector according to claim 1 or 2, characterized in that, In step one, the controller (8) has a control table that pre-stores the user's required air volume, the fan current reference value and the inverter output frequency in a one-to-one correspondence. After receiving the user's required air volume, the controller (8) looks up the corresponding fan current reference value and inverter output frequency through the control table, thereby controlling the inverter (6) to drive the fan (5) to operate according to the inverter output frequency.

4. The airflow control method for a filter bag dust collector according to claim 1, characterized in that, In step two, the current sampling circuit (9) includes a current transformer (91), resistors R1 and R2, and an operational amplifier U1. The primary winding of the current transformer (91) is connected in series between the fan (5) and the frequency converter (6). One end of the secondary winding of the current transformer (91) is connected to one end of resistor R1 and one end of resistor R2. The other end of the secondary winding of the current transformer (91) and the other end of resistor R1 are grounded. The other end of resistor R2 is connected to the non-inverting input of the operational amplifier U1. The inverting input of the operational amplifier U1 is connected to the output of the operational amplifier U1. The output of the operational amplifier U1 is connected to the controller (8).

5. The airflow control method for a filter bag dust collector according to claim 1, characterized in that, In step three, the frequency adjustment value is obtained by the controller (8) through fuzzy PID control based on the current difference obtained in step two.

6. The airflow control method for a filter bag dust collector according to claim 5, characterized in that, In step three, the fuzzy PID control operation includes: Obtain the current difference calculated from the difference between the real-time drive current and the fan current reference value; The rate of change of the current difference is obtained by calculating the rate of change of the current difference compared to the current difference obtained at the previous moment; The current difference and the rate of change of the current difference are subjected to fuzzy control. The output is found according to the fuzzy rule table to optimize and obtain the three parameters Kp, Ki and Kd in real time. Then, the current difference and the three parameters Kp, Ki and Kd are subjected to PID control to calculate and output a frequency adjustment value.

7. The airflow control method for a filter bag dust collector according to claim 1, characterized in that, In step three, the operation of the controller (8) calculating and outputting a frequency adjustment value to the inverter (6) based on the current difference obtained in step two includes: A frequency regulation control table that corresponds one-to-one between current difference and frequency regulation value is pre-stored in the controller (8); After receiving the current difference, the controller (8) finds the frequency adjustment value corresponding to the current difference by querying the frequency adjustment control table and outputs it to the frequency converter (6).

8. The airflow control method for a filter bag dust collector according to claim 1, 5, 6, or 7, characterized in that, Step three also includes the following steps: The maximum frequency output value of the frequency converter is pre-stored in the controller (8); After the controller (8) calculates and outputs a frequency adjustment value, it compares the adjusted inverter output frequency with the inverter's maximum frequency output value. When the inverter output frequency is greater than the inverter's maximum frequency output value, it controls the inverter (6) to stop working and sends an alarm signal to the control panel (7). The control panel (7) provides sound and / or light alarms to remind the user to perform dust removal in a timely manner.

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