Dmc polarized electrostatic precipitator and method

Abstract

The application discloses a DMC polarized electrostatic dust removal equipment and method, and belongs to the technical field of equipment manufacturing for atmospheric pollution prevention and control. Dust-containing airflow passes through a polarized electric field composed of a cylindrical dust collection electrode, a disc-shaped corona electrode in the center of the cylinder and a coaxial shielding plate from bottom to top. According to the secondary volt-ampere characteristic, the application identifies the dust specific resistance working condition on line and adjusts the high-frequency power pulse duty cycle accordingly to suppress the back corona of high specific resistance dust. The dust accumulation load is represented by integrating the pulse conduction current with the duty cycle as the weight to realize dust removal on demand. The dust removal start-up delay is determined according to a first-order exponential decay model to make the dust removal at low airflow speed. The collected dust falls back to the coal conveying belt for recycling after being vibrated by the soft curtain of the lower buffer discharge bin. The application does not need a special specific resistance instrument, improves the adaptability to high specific resistance dust and the dust removal efficiency, reduces the operation power consumption and secondary dust raising, and takes into account energy saving and anti-spontaneous combustion safety.

Description

Technical Field

[0001] This application belongs to the field of manufacturing technology of equipment for air pollution control, and particularly relates to DMC polarized electrostatic dust removal equipment and methods. Background Technology

[0002] During the unloading, multi-stage conveyor belt transfer, screening, and plowing of raw coal into storage at thermal power plants, dust sources are formed at locations such as the coal transfer section, crushing equipment blower, conveyor belt chute outlet, and tail end due to positive pressure airflow. The fine dust in these sources remains suspended for extended periods and easily causes secondary dust pollution, posing hazards to the surrounding environment and worker health, and also creating safety risks of spontaneous combustion and deflagration. Similar dust problems exist at material crushing and transfer points in industries such as mining, cement, and casting. Therefore, effective on-site dust collection at these dust-generating locations is of great significance for both air pollution control and operational safety.

[0003] Existing dust removal methods in coal conveying systems mainly include baghouse dust collection, wet scrubbing, dry fog dust suppression, and dry electrostatic precipitators. Baghouse dust collection suffers from high equipment resistance, high operating power consumption, and frequent filter bag replacement; wet scrubbing generates dust-laden wastewater, causing secondary pollution; traditional line-plate electrostatic precipitators have bulky high-voltage power supplies, often require multiple electric fields in series, have long electric field lengths, and allow low airflow velocities within the electric field, making them difficult to install on-site in confined spaces. To address the need for miniaturization in on-site dust collection, the industry has proposed a cylindrical polarized electrostatic precipitator structure. This structure uses the inner wall of a cylinder as the grounded dust collection electrode, a disc-shaped corona electrode at the center of the cylinder, and a circular baffle plate coaxially positioned below the corona electrode. This allows the dust-laden airflow to bypass the inefficient area near the corona electrode as it enters the electric field from bottom to top, shortening the electric field length while increasing the effective dust collection area. While this structure addresses the miniaturization and electric field shielding issues to some extent, it still has shortcomings in the intelligent matching of power supply, dust collection, and dust discharge processes. Existing polarized electrostatic precipitators mostly use high-frequency, high-voltage power supplies with constant parameters, failing to adjust in real time according to fluctuations in dust resistivity caused by changes in coal quality and humidity. When handling high-resistivity dust, the dust layer on the collecting electrode surface can break down and discharge, generating a back corona. This slows down the release of charge from the charged dust, forces a decrease in corona current, and significantly reduces dust removal efficiency. Furthermore, existing solutions often require dedicated resistivity measuring instruments to identify dust resistivity, but these probes are prone to contamination and failure in dusty environments, making long-term stable online operation difficult. The dust discharge sequence of existing polarized electrostatic precipitators is also relatively crude, often using fixed, empirically determined delays that do not match the actual airflow attenuation process on-site. When the delay is too short, the residual airflow velocity inside the cylinder remains higher than the critical velocity for dust re-entrainment, causing the collected dust, after being cleared by vibration and scraping, to be re-entrained by the airflow, creating secondary dust. Conversely, when the delay is too long, it reduces the equipment's processing capacity. Existing polarized electrostatic precipitators mostly trigger dust removal according to a fixed cycle, without considering the random fluctuations in the dust load at the site. Frequent dust removal at a fixed cycle under low dust load will cause unnecessary energy consumption and wear on the dust removal motor and rapping mechanism, while a fixed cycle under high dust load may cause excessive dust accumulation on the dust collecting electrode, resulting in incomplete dust removal, or even the safety hazard of spontaneous combustion due to excessive dust accumulation.

[0004] Therefore, it is necessary to provide a polarized electrostatic precipitator and method that adapts to operating conditions, reduces energy consumption, improves operational safety, and enables on-site dust recycling and reuse. Summary of the Invention

[0005] This application provides a DMC polarized electrostatic dust removal method, in which dust-laden airflow passes through a polarized electric field from bottom to top. The polarized electric field consists of a cylinder serving as a grounded dust collection electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular baffle plate coaxial with and below the disc-shaped corona electrode. An annular inflow channel is formed between the circular baffle plate and the inner wall of the cylinder. The dust-laden airflow bypasses the central direct impact area of ​​the disc-shaped corona electrode and enters the polarized electric field through this annular inflow channel. The method includes the following steps:

[0006] S1, during the power supply and dust removal stage, the secondary voltage and secondary current of the high-frequency high-voltage power supply are collected. Based on the volt-ampere characteristic of the secondary current changing with the secondary voltage, the specific resistance related operating condition index is obtained. Based on the specific resistance related operating condition index, the duty cycle of the output pulse of the high-frequency high-voltage power supply is adjusted to supply power to the polarized electric field.

[0007] S2, During the power supply and dust removal stage, the secondary current during the pulse conduction period is collected, and the collected secondary current is integrated with the duty cycle as the weight to obtain the dust load characterization value that characterizes the dust accumulation load of the dust collecting electrode after duty cycle correction.

[0008] S3, when the dust load characterization value reaches the set threshold, a dust discharge trigger signal is generated, the high-frequency high-voltage power supply is cut off, the induced draft fan is stopped, and the airlock is switched to the state of blocking the external dust-laden airflow from entering the polarized electric field.

[0009] S4. Collect velocity data of airflow velocity decaying over time inside the cylinder, and determine the dust removal start delay required for the airflow velocity to decay to below the critical velocity for dust re-entrainment according to the first-order exponential decay model.

[0010] S5, after the disc-shaped corona electrode is discharged to a safe potential through the discharge resistor and after the dust discharge start delay from the moment of stop, the dust discharge mechanism is started to clean the disc-shaped corona electrode and the dust collection electrode, so that the cleaned dust falls back to the coal conveyor belt for recycling after the soft curtain of the lower buffer unloading hopper vibrates.

[0011] Further, step S1 includes:

[0012] S11, based on the lower limit and upper limit of the slope obtained in advance under the conditions of determined electrode spacing, wind speed and spray state, at the beginning stage of the power supply control cycle, the high frequency high voltage power supply is controlled to raise the secondary voltage from the corona initiation voltage to the rated voltage, and the corresponding secondary current is synchronously collected at the set sampling period to obtain the volt-ampere characteristic data sequence composed of multiple sets of secondary voltage and secondary current.

[0013] S12, Select a data segment from the current-voltage characteristic data sequence in which the secondary voltage is greater than the corona initiation voltage, perform least squares linear fitting on the secondary current and secondary voltage in the data segment, and use the slope of the fitted line as a characteristic quantity reflecting the polarization condition of the dust-laden airflow.

[0014] S13, normalize the slope to a specific resistance-related operating condition index using the following formula:

[0015] ,and ;

[0016] In the formula, This refers to the operating condition index related to specific resistance; The slope obtained in step S12; This is the lower limit of the slope under pre-calibrated high specific resistance conditions; This is the pre-calibrated upper limit of the slope under low specific resistance conditions; when calculated according to the above formula... When less than 0, take The value is 0 when calculated according to the above formula. Take when greater than 1 =1;

[0017] S14, determine the duty cycle of the high-frequency high-voltage power supply output pulse using the specific resistance-related operating condition index according to the following formula, and supply power to the polarization electric field with the determined duty cycle to obtain a power supply state matching the current polarization operating condition:

[0018] ,and ;

[0019] In the formula, The duty cycle of the output pulse of the high-frequency high-voltage power supply; The lower limit of the pre-set duty cycle; The upper limit of the pre-set duty cycle; The specific resistance-related operating condition index obtained in step S13.

[0020] Furthermore, the process of supplying power to the polarized electric field with a determined duty cycle in step S14 also includes: controlling the peak voltage of the high-frequency high-voltage power supply output pulse to operate below the spark initiation point; when a spark flashover is detected in the polarized electric field, first reducing the output voltage, and then raising the output voltage back to the target voltage that does not exceed the rated voltage and is lower than the current spark initiation point according to a pre-set multi-segment boost curve.

[0021] Further, step S2 includes:

[0022] S21, starting from the end of the last dust removal, collect the secondary current of the high-frequency high-voltage power supply when it is in the pulse conduction state and the duty cycle within the set integral step size.

[0023] S22, the collected secondary current is numerically integrated using the duty cycle as a weight according to the following formula to obtain the dust load characterization value corrected for the duty cycle:

[0024] ;

[0025] In the formula, This represents the dust load characterization value; For the first The secondary current collected when the high-frequency high-voltage power supply is in pulse conduction state within each integration step; For the first The duty cycle of the high-frequency high-voltage power supply output pulse within each integration step; This is the integration step size; This is the summation operator; The sequence number of the integration step;

[0026] S23, compare the dust load characterization value with the set threshold, generate the dust discharge trigger signal when the dust load characterization value reaches the set threshold, and after the dust discharge is completed, clear the dust load characterization value to zero and then re-accumulate it to obtain a dust discharge rhythm that is automatically denser or sparser depending on the dust load.

[0027] Further, step S4 includes:

[0028] S41, the wind speed sensing unit collects the velocity data sequence of the airflow velocity inside the cylinder as the velocity decays over time, and takes the average airflow velocity collected within a preset stable time period after the cylinder stops rotating and the external dust-laden airflow is blocked as the residual airflow velocity, and selects data with a velocity value greater than the residual airflow velocity from the velocity data sequence.

[0029] S42, take the natural logarithm of the difference between the velocity value at each moment in the selected data and the residual airflow velocity, and perform least squares linear fitting on the natural logarithm value and the corresponding moment; when the slope of the fitted line is less than 0 and the goodness of fit reaches a set threshold, take the negative reciprocal of the slope of the fitted line as the airflow velocity decay time constant, and the fitting characterizes the first-order exponential decay of the airflow velocity.

[0030] S43, when the initial stop speed is greater than the critical speed for dust re-entrainment, and the critical speed for dust re-entrainment is greater than the residual airflow speed, and the airflow speed decay time constant is obtained in step S42, the decay time required for the airflow speed to decay from the initial stop speed to the critical speed for dust re-entrainment is calculated according to the following formula, and the decay time is added to the set safety margin time to obtain the dust removal start delay:

[0031] ,and ;

[0032] In the formula, This refers to the decay time; The airflow velocity decay time constant obtained in step S42; The airflow velocity inside the cylinder at the initial moment of shutdown; The residual airflow velocity; The pre-calibrated critical velocity for dust re-entrainment; The natural logarithm operator;

[0033] S44, when the initial speed at which the rotation stops is not greater than the critical speed of dust re-entrainment, the dust removal start delay is set to the lower limit of the preset delay; when the critical speed of dust re-entrainment is not greater than the residual airflow speed, or the slope of the fitted straight line is not less than 0, or the goodness of fit is lower than the set threshold, the dust removal start delay is set to the upper limit of the preset delay or the dust removal is prohibited and an abnormal alarm is issued, so as to obtain the dust removal start time to avoid secondary dust generation.

[0034] Further, the dust removal mechanism activation in step S5 includes: after the high-frequency high-voltage power supply has been cut off and the disc-shaped corona electrode has been discharged to a safe potential through the discharge resistor, the dust removal motor drives the disc-shaped corona electrode to rotate through the insulated transmission assembly, so that the spikes on the disc-shaped corona electrode contact and scrape the fixed dust scraper installed through the insulated bracket to remove the dust accumulated on the spikes; at the same time, the vibrator located in the middle of the cylinder strikes the cylinder wall to remove the dust accumulated on the inner wall of the dust collecting electrode; and the soft curtain vibration mechanism drives the soft curtain at the bottom of the lower buffer unloading bin to vibrate, so that the cleared dust falls back to the coal conveyor belt.

[0035] Furthermore, before the dust-laden airflow passes through the polarized electric field from bottom to top, the airflow is first slowed down by a pre-buffer unloading device. Heavier dust particles in the airflow settle in the pre-buffer unloading device and fall back onto the coal conveyor belt. The remaining airflow containing fine dust is first filtered through a steel screen to remove impurities, and then humidified by a water mist spraying device in the air distribution box before entering the polarized electric field upwards. When the spray flow rate of the water mist spraying device is not lower than the set flow rate, the water pressure is not lower than the set water pressure, the wall temperature in the polarized electric field is higher than the preset dew point safety threshold, and the condensation sensor does not activate, step S1 supplies power to the polarized electric field. When the spray flow rate is lower than the set flow rate, the water pressure is lower than the set water pressure, the condensation sensor activates, or the wall temperature is lower than the preset dew point safety threshold, the output of the high-frequency high-voltage power supply is reduced or cut off.

[0036] The present invention also provides a DMC polarized electrostatic dust removal device for implementing the DMC polarized electrostatic dust removal method described in claim 1, characterized in that it includes a polarized electric field unit, a high-frequency high-voltage power supply module, a sampling unit, a wind speed sensing unit, an induced draft fan, a wind shut-off device, a dust removal mechanism, a lower buffer unloading hopper, and a controller.

[0037] The polarized electric field unit includes a cylinder serving as a grounded dust collection electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular shielding plate coaxial with and below the disc-shaped corona electrode. The diameter of the circular shielding plate is smaller than the inner diameter of the cylinder and forms an annular inflow channel with the inner wall of the cylinder. The disc-shaped corona electrode is connected to the high-voltage output terminal of the high-frequency high-voltage power supply module via a high-voltage connector. The disc-shaped corona electrode is also grounded via a discharge resistor.

[0038] The high-frequency high-voltage power supply module is a high-frequency switching power supply with an adjustable output pulse duty cycle, and the control terminal of the high-frequency high-voltage power supply module is connected to the controller.

[0039] The sampling unit is connected to the secondary output circuit of the high-frequency high-voltage power supply module, and the signal output terminal of the sampling unit is connected to the controller to output the sampled secondary voltage and secondary current to the controller.

[0040] The wind speed sensing unit is located inside the cylinder, and the signal output terminal of the wind speed sensing unit is connected to the controller to output the airflow speed inside the cylinder to the controller.

[0041] The induced draft fan and the airlock are located on the airflow channel of the polarized electric field unit, and the control terminals of the induced draft fan and the airlock are respectively connected to the controller.

[0042] The dust removal mechanism includes a dust removal motor, a disc-shaped corona electrode driven to rotate by the dust removal motor via an insulating transmission assembly, a fixed dust scraper mounted on an insulating bracket and scraping against the spikes on the disc-shaped corona electrode, and a vibrator that strikes the cylindrical wall. The control terminal of the dust removal motor is connected to the controller.

[0043] The lower buffer unloading bin is located below the polarized electric field unit and above the coal conveyor belt. The bottom of the lower buffer unloading bin is equipped with a soft curtain and a soft curtain vibration mechanism that drives the soft curtain to vibrate. The control terminal of the soft curtain vibration mechanism is connected to the controller.

[0044] The signal input terminals of the controller are connected to the sampling unit and the wind speed sensing unit, respectively. The control terminals of the controller are connected to the high-frequency high-voltage power supply module, the induced draft fan, the airlock, the dust removal motor, and the soft curtain vibration mechanism, respectively. The controller is configured to: determine the specific resistance related operating condition index based on the secondary voltage and secondary current output by the sampling unit and adjust the duty cycle of the output pulse of the high-frequency high-voltage power supply module accordingly; integrate the secondary current with the duty cycle as the weight to obtain the dust load characterization value; when the dust load characterization value reaches a set threshold, cut off the high-frequency high-voltage power supply module, stop the induced draft fan, and switch the airlock to the state of blocking the entry of external dust-laden airflow; determine the dust removal start delay based on the airflow speed output by the wind speed sensing unit, and control the dust removal motor and the soft curtain vibration mechanism to operate after the discharge resistor discharges the disc-shaped corona electrode to a safe potential and after the dust removal start delay.

[0045] Furthermore, the insulating transmission assembly includes a cam mechanism driven by the dust removal motor, a spring, a corona cleaning rod, and an insulating shaft. The corona cleaning rod is connected to the disc-shaped corona electrode via the insulating shaft. The cam mechanism drives the disc-shaped corona electrode to rotate via the spring and the corona cleaning rod. The high-voltage connector is a conductive slip ring or a high-voltage flexible connector that allows the disc-shaped corona electrode to rotate relative to each other. The inner wall of the dust collecting electrode is provided with a groove, and a semi-conductive polarization layer is attached to the groove. The semi-conductive polarization layer is connected to the cylinder at the same potential via a conductive connection point.

[0046] Furthermore, it also includes a pre-buffered unloading device, a steel screen, an air distribution box, a water mist spraying device, and a low-temperature condensation protection temperature switch, a condensation sensor, and an alarm connected to the controller; along the flow direction of the dust-laden airflow, the pre-buffered unloading device is installed on the upper part of the guide chute of the coal conveyor belt and located on the air inlet side of the polarized electric field unit; the steel screen is located on the air inlet side of the air distribution box; the water mist spraying device is located inside the air distribution box and is interlocked with the controller via a water flow sensor switch and a water pressure switch; the air distribution box is located between the steel screen and the polarized electric field unit; the low-temperature condensation protection temperature switch, the steel screen, the water mist spraying device ... The dew protection temperature switch and the dew sensor are located within the polarized electric field unit. The low-temperature dew protection temperature switch is used to detect that the wall temperature within the polarized electric field unit is lower than a preset dew point safety threshold. The controller is configured to reduce or cut off the output of the high-frequency high-voltage power supply module and issue an audible and visual alarm via the alarm device when the dew sensor or the low-temperature dew protection temperature switch is activated. The high-frequency high-voltage power supply module, the sampling unit, and the controller are integrated with the polarized electric field unit to form one or more independent dust removal units installed in combination on the upper part of the feed trough.

[0047] The beneficial effects of this invention are as follows:

[0048] This invention utilizes the existing secondary voltage and current sampling data of the high-frequency high-voltage power supply during the dust removal stage. Based on the volt-ampere characteristics of the secondary current changing with the secondary voltage, it extracts operating condition information related to the dust resistivity and adaptively adjusts the duty cycle of the high-frequency high-voltage power supply output pulse accordingly. This enables online identification of the dust resistivity operating condition and power supply according to the operating condition without the need for a separate dedicated resistivity measuring instrument. This eliminates the need for resistivity probes that are easily contaminated and fail in dusty environments, improves the long-term online operation reliability of the system, and reduces configuration costs. When dust is identified as operating under high resistivity conditions, this invention reduces the duty cycle and uses narrow-pulse intermittent power supply. This allows the accumulated charge on the dust collecting electrode to dissipate during the pulse intervals, thereby suppressing the formation of back corona. The equipment can maintain high dust collection efficiency even under high resistivity conditions, overcoming the adverse tendency of high resistivity dust leading to decreased corona current and reduced dust removal efficiency. When dust is identified as operating under low resistivity conditions, this invention increases the duty cycle to approach continuous power supply to maintain a strong field strength, balancing dust removal effects under different resistivity conditions. Power supply is provided according to the current operating conditions rather than being constant and continuous, thus reducing the energy consumption of the electric field. This power supply method achieves lower energy consumption while ensuring dust removal efficiency. In addition, this invention controls the pulse peak voltage below the spark initiation point and, in the event of spark flashover, first reduces the voltage and then rises it back according to a multi-segment voltage increase curve. This maximizes the utilization of the effective field strength while avoiding continuous flashover, improving the stability of the power supply.

[0049] This invention collects the secondary current during the pulse conduction phase of the power supply and dust removal process, and integrates the secondary current with the duty cycle as the weight to obtain a duty cycle-corrected dust load characterization value. During the pulse conduction phase, the secondary current reflects the corona discharge intensity, and there is a corresponding relationship between the amount of charge transported to the dust collecting electrode per unit time and the amount of dust collected. The pulse conduction time depends on the duty cycle. The integration with the duty cycle as the weight makes the dust load characterization value correspond to the actual charge transported to the dust collecting electrode. When the duty cycle is dynamically adjusted according to the specific resistance condition, the dust load characterization value can still accurately reflect the actual dust accumulation at the dust collecting electrode, overcoming the defect of characterization distortion caused by duty cycle changes when integrating directly without considering the duty cycle. This invention triggers dust removal only when the dust load reaches a set threshold. Dust removal is more frequent when the dust load is high and less frequent when the dust load is low. The dust removal rhythm automatically increases or decreases depending on the dust load. At low dust loads, unnecessary dust removal actions are reduced, thus reducing the energy consumption and wear of the dust removal mechanism. At high dust loads, excessive dust accumulation on the dust collection electrode is avoided, thus balancing energy saving and safety requirements to prevent spontaneous combustion caused by excessive dust accumulation.

[0050] This invention, upon triggering dust removal, first cuts off the high-frequency high-voltage power supply, stops the induced draft fan, and switches the airlock to block external dust-laden airflow from entering the polarized electric field. This eliminates the electric field's adsorption force on dust, prevents sparks during dust removal, and simultaneously causes the airflow inside the cylinder to gradually decay, creating conditions for dust removal at low airflow velocities. This invention collects data on the decay of airflow velocity inside the cylinder over time, determines the dust removal start-up delay required for the airflow velocity to decay below the critical velocity for dust re-entrainment using a first-order exponential decay model, and then performs dust removal only after the airflow velocity drops below this critical velocity. Whether the removed dust is re-entrained depends on the airflow velocity inside the cylinder during dust removal. Dust removed by vibration and scraping is not re-entrained by residual airflow, significantly reducing secondary dust generation. This overcomes the shortcomings of using fixed empirical delays, where excessively short delays lead to re-entrainment and excessively long delays reduce processing capacity. Before dust removal, the disc-shaped corona electrode is discharged to a safe potential via a discharge resistor, and the fixed dust scraper is installed via an insulated bracket, ensuring electrical safety during the dust removal process. This invention uses a dust removal method where the disc-shaped corona electrode rotates and scrapes against the fixed dust scraper. Compared to simple vibration, this method promptly removes accumulated dust, including sticky dust, adhering to the spikes, maintaining good discharge performance of the corona electrode. The dust removed is then vibrated by the soft curtain of the lower buffer unloading hopper and falls back to the coal conveyor belt for recycling, eliminating the need for a separate dust conveying system and avoiding secondary pollution.

[0051] This invention decelerates the dust-laden airflow before it enters the polarized electric field using a pre-buffer unloading device. This allows heavier dust particles to settle and fall back onto the coal conveyor belt. Impurities are then filtered out by a steel screen, reducing the amount of dust that needs to be captured by the electric field and preventing impurities from adhering to the electrodes and causing continuous flashover or ignition hazards. This correspondingly reduces the electric field load and energy consumption. The invention also humidifies the dust-laden airflow using a water mist spray device within the air distribution box, reducing the resistivity of high-resistivity dust particles and making them easier for the electric field to capture. Simultaneously, the water mist suppresses coal dust sparks, improving fire safety during operation. Furthermore, this invention incorporates an interlock between the water mist spray and the high-frequency, high-voltage power supply. Power is only allowed when the spray flow rate and water pressure meet requirements and there is no risk of condensation. High-voltage output is reduced or cut off when spray is insufficient, condensation occurs, or the wall temperature is too low. This balances the beneficial effects of humidification and resistance reduction with the safety requirement of preventing surface flashover due to condensation on high-voltage insulating components. This invention integrates the polarized electric field unit with a high-frequency high-voltage power supply, a sampling unit, and a controller to form an independent dust removal unit. It has a compact structure and can be installed on-site in narrow spaces at transition dust-generating areas, achieving on-site dust collection and discharge, and improving adaptability to narrow installation environments. Attached Figure Description

[0052] Figure 1The graphs show the dust removal efficiency and relative electric field power consumption of Examples 3, 1, 2 and Comparative Example 1. (a) is a comparison graph of the dust removal efficiency of Examples 3, 1, 2 and Comparative Example 1 under three resistivity conditions, and (b) is a comparison graph of the relative electric field power consumption of Examples 3, 1, 2 and Comparative Example 1 under three resistivity conditions.

[0053] Figure 2 The graphs show the comparison of dust load and dust removal frequency of Examples 1, 2, and 3 with Comparative Examples 2 and 4. (a) is a comparison of the changes in dust load characterization values ​​of Examples 1 and 4 with operating time, and (b) is a comparison of the number of dust removal frequencies of Examples 1, 2, and 3 with Comparative Example 2 under three dust load conditions.

[0054] Figure 3 The graphs show the wind speed attenuation and dust re-entrainment rate of Examples 1, 2, 3 and Comparative Example 3. (a) is a comparison graph of the airflow velocity in the cylinder attenuation after the cylinder stops and the dust removal start-up delay of each example under the three working conditions. (b) is a comparison graph of the dust re-entrainment rate of Examples 1, 2, 3 and Comparative Example 3 under the three working conditions.

[0055] Figure 4 This is a comprehensive comparison chart of four indicators—dust removal efficiency, relative electric field power consumption, relative dust removal mechanism energy consumption, and dust re-entrainment rate—between Example 1 and Comparative Examples 1, 2, and 3.

[0056] Figure 5 This is a structural diagram of the DMC polarized electrostatic precipitator of the present invention. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below. The description is intended to enable those skilled in the art to understand and implement the present invention, and is not intended to limit the scope of protection of the present invention.

[0058] In this invention, DMC polarized electrostatic dust removal refers to an on-site dust removal method that uses the inner wall of a cylinder as a grounded dust collection electrode, a disc-shaped corona electrode in the center of the cylinder in conjunction with a coaxial circular baffle plate, and uses high-frequency high-voltage pulse power supply to polarize and charge the dust. It is suitable for installation on the upper part of the conveyor belt chute of the coal conveying system in thermal power plants, as well as dust-generating parts at material crushing and transfer drop points in industries such as mining, cement, and casting.

[0059] In the DMC polarized electrostatic dust removal method of the present invention, the dust-laden airflow passes through the polarized electric field from bottom to top. The polarized electric field consists of a cylinder serving as a grounded dust collection electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular baffle plate coaxial with and below the disc-shaped corona electrode. An annular inflow channel is formed between the circular baffle plate and the inner wall of the cylinder. The dust-laden airflow bypasses the central direct-impact area of ​​the disc-shaped corona electrode and enters the polarized electric field through the annular inflow channel. The principle behind this arrangement is that the area near the disc-shaped corona electrode is an inefficient region of the electric field, where charged dust experiences a smaller driving force. Furthermore, if dust directly impacts the corona electrode, it is prone to adhere and accumulate on the corona electrode, weakening its discharge performance. The circular baffle plate guides the initial dust-laden airflow to the efficient region on one side of the inner wall of the cylinder, ensuring that the dust is in a stronger driving field upon entering the electric field. This shortens the electric field length while maintaining high dust collection efficiency and reduces the tendency for dust to accumulate on the corona electrode. This method is executed in the order of steps S1 to S5.

[0060] Step S1 is performed during the power supply and dust removal stage. In this step, the secondary voltage and secondary current of the high-frequency high-voltage power supply are collected. Based on the volt-ampere characteristic of the secondary current changing with the secondary voltage, the specific resistance-related operating condition index is obtained. The duty cycle of the high-frequency high-voltage power supply output pulse is adjusted according to the specific resistance-related operating condition index to supply power to the polarized electric field. The secondary voltage and secondary current refer to the high-voltage side voltage and its loop current applied to the corona electrode after the high-frequency high-voltage power supply is boosted. Both are collected by a sampling unit connected to the secondary output circuit of the high-frequency high-voltage power supply. The duty cycle refers to the ratio of the conduction time of the high-voltage pulse applied within one switching cycle of the high-frequency high-voltage power supply to that switching cycle. The specific resistance of dust is a key factor affecting the efficiency of electrostatic dust removal. When the specific resistance of the dust is too high, the charge carried by the charged dust reaching the collecting electrode is not easily discharged through the collecting electrode. A reverse electric field gradually builds up on both sides of the dust layer and breaks down, forming a back corona, which forces the corona current to decrease and reduces the dust collection efficiency. Traditional methods often rely on dedicated specific resistance measuring instruments, but their probes are easily contaminated and fail in dusty environments. This method does not require a separate resistance meter. Instead, it utilizes the existing secondary voltage and secondary current sampling data of the power supply to extract operating condition information related to the resistance from the volt-ampere characteristics of the electric field. Based on this information, it dynamically adjusts the duty cycle of the power supply pulse to match the power supply status with the current dust characteristics.

[0061] Step S1 further includes steps S11, S12, S13 and S14.

[0062] In step S11, based on the pre-calibrated lower and upper slope limits obtained under the conditions of determined electrode spacing, wind speed, and spray state, at the beginning of the power supply control cycle, the high-frequency high-voltage power supply is controlled to raise the secondary voltage from the corona initiation voltage to the rated voltage, and the corresponding secondary current is synchronously collected at a set sampling period to obtain a volt-ampere characteristic data sequence composed of multiple sets of secondary voltages and secondary currents. The corona initiation voltage refers to the critical voltage at which the corona electrode begins to generate corona discharge and corona current begins to appear in the circuit. The lower slope limit... and upper limit of slope These are boundary values ​​obtained by measuring and fitting the volt-ampere characteristics under fixed electrode spacing, fixed wind speed, and fixed spray conditions for both high and low resistivity conditions. Their purpose is to provide a benchmark for subsequent normalization. Therefore, step S11, when running online, does not require the site to be under the aforementioned calibration conditions; instead, it uses the pre-calibrated values. and The sampling period is preferably on the order of milliseconds to obtain a sufficient number of data points within the boost time.

[0063] In step S12, a data segment with a secondary voltage greater than the corona initiation voltage is selected from the volt-ampere characteristic data sequence. The secondary current and secondary voltage in this data segment are then fitted using a least-squares linear relationship. The slope of the fitted line is used as a characteristic quantity reflecting the polarization condition of the dust-laden airflow. The least-squares linear fitting refers to a conventional data processing method that finds a straight line in a set of data points that minimizes the sum of the squares of the longitudinal deviations of each data point from that line. The slope obtained from the fitting represents the increment of the secondary current for each unit increase in secondary voltage. The data segment with a secondary voltage greater than the corona initiation voltage is selected for fitting because the corona current only begins to build up and increases with voltage rise after the secondary voltage exceeds the corona initiation voltage. In engineering, the volt-ampere relationship in this segment can be approximated as a straight line. However, when the dust resistivity is high and the back corona is strong, the corona current built up per unit voltage increment is small, and the slope obtained from the fitting decreases accordingly. Therefore, this slope can reflect the polarization condition related to the dust resistivity. Considering that the corona voltage-current relationship is not strictly linear and is affected by a variety of factors, this method only uses the slope as a characteristic quantity related to the resistivity, and does not directly equate it to the true resistivity of the dust.

[0064] In step S13, the slope is normalized to a specific resistance-related operating condition index using the following formula.

[0065] ;

[0066] In the formula, The specific resistance-related operating condition index is dimensionless; The slope (mA / kV) obtained in step S12; The lower limit of the slope (mA / kV) under pre-calibrated high specific resistance conditions. This is the pre-calibrated upper limit of the slope (mA / kV) under low specific resistance conditions.

[0067] The above formula is a linear normalization operation, which transforms the slope of the quantity in mA / kV into a linear normalization value. Mapped to a dimensionless exponent between 0 and 1 .when equal That is, when in low resistivity condition, Take 0; when equal That is, when in a high resistivity condition, Take 1; When it is in between, It varies linearly between 0 and 1, and The smaller the value, the higher the operating conditions related to the specific resistance. The larger the value, the more important it is to ensure the monotonicity and boundedness of the normalization. Greater than When the data collected on-site is affected by fluctuations, the calculation according to the above formula will be affected. When less than 0, take If the value is 0, then the result calculated according to the above formula is... Take when greater than 1 The value is 1, thus... Limit it to between 0 and 1 to prevent the duty cycle from exceeding the set range.

[0068] In step S14, the duty cycle of the high-frequency high-voltage power supply output pulse is determined by the specific resistance-related operating condition index according to the following formula, and power is supplied to the polarization electric field with the determined duty cycle to obtain a power supply state that matches the current polarization operating condition.

[0069] ;

[0070] In the formula, The duty cycle of the output pulse of the high-frequency high-voltage power supply is dimensionless. The lower limit of the pre-set duty cycle is dimensionless. The duty cycle is a pre-set upper limit, dimensionless; The specific resistance-related operating condition index obtained in step S13 is dimensionless.

[0071] The above formula is a linear mapping operation, which is used to convert the resistance-related operating condition index between 0 and 1. Mapped to duty cycle .when When the value is 0, it indicates a low resistivity condition. Take the upper limit The power supply approaches continuous supply to maintain a high field strength; when A value of 1 indicates operation under high resistivity conditions. Take the lower limit The power supply is changed to a narrow-pulse intermittent power supply. This narrow-pulse intermittent power supply allows the dust layer on the collecting electrode to release its accumulated charge during the pulse intervals, suppressing the formation of back corona and preventing a significant drop in corona current under high resistivity conditions. Less than To ensure the monotonicity of the mapping. Upper limit of duty cycle. Preferred value is close to but not equal to 1, lower limit of duty cycle. The smaller value that can maintain corona discharge is preferred, and the specific values ​​of the two are determined by calibration based on the equipment structure and the coal quality on site. From step S11 to step S14, the high-frequency high-voltage power supply can adaptively adjust between continuous power supply and narrow pulse intermittent power supply according to the dust polarization conditions, thereby improving the equipment's adaptability to high resistivity dust and reducing unnecessary power consumption due to power supply being provided on demand.

[0072] The process of supplying power to the polarized electric field with a determined duty cycle in step S14 may further include handling spark flashover. In this process, the peak voltage of the high-frequency high-voltage power supply output pulse is controlled below the spark initiation point, so that the electric field operates as close to breakdown as possible without sparking to obtain a higher effective field strength. The spark initiation point refers to the voltage corresponding to when the electric field begins to exhibit spark discharge. When a spark flashover is detected in the polarized electric field, the output voltage is first reduced to extinguish the spark, and then the output voltage is raised back to a target voltage that does not exceed the rated voltage and is lower than the current spark initiation point according to a pre-set multi-segment boost curve. The multi-segment boost curve refers to a voltage recovery process consisting of several segments with different recovery rates connected sequentially, where the initial recovery is faster to restore power supply as quickly as possible, and the recovery slows down when approaching the original spark voltage to avoid another flashover. Limiting the recovery target to no more than the rated voltage and lower than the current spark initiation point is based on the consideration that under conditions of high humidity, high dust, or near condensation, the rated voltage itself may also trigger a re-flashover. Therefore, using the current spark initiation point as the upper limit is more prudent. The recovery rate and duration of each segment of the multi-segment voltage rise curve can be preset based on equipment experience, such as setting a fast segment, a medium-speed segment, a low-speed segment, and a transition segment before the spark voltage.

[0073] Step S2 is performed during the power supply and dust removal phase. In this step, the secondary current during the pulse conduction period is collected, and the collected secondary current is integrated with the duty cycle as a weight to obtain a dust load characterization value, which is corrected for the duty cycle and represents the dust accumulation load on the collecting electrode. The dust load characterization value refers to a measure reflecting the amount of dust accumulated on the collecting electrode since the last dust removal. The principle of setting up step S2 is that, during the electrostatic precipitator process, the secondary current mainly consists of the ion current generated by corona discharge. Ions charge the dust during migration and drive it towards the collecting electrode. Therefore, there is a corresponding relationship between the amount of charge transported to the collecting electrode per unit time and the amount of dust collected. Integrating the secondary current over time yields the amount of charge corresponding to the accumulated dust, which is used as a characterization of the dust load. Thus, dust removal can be triggered according to the actual accumulation of dust load, instead of dust removal at a fixed time period.

[0074] Since the duty cycle in this method is dynamically adjusted according to the specific resistance, if the secondary current is directly integrated based on the average of the secondary current over the entire integration step, the change in duty cycle will cause the integration result to deviate from the actual transported charge. Therefore, step S2 collects the secondary current during the pulse conduction period and corrects it using the duty cycle as the weight. Step S2 further includes steps S21, S22, and S23.

[0075] In step S21, starting from the end of the previous dust removal, the secondary current of the high-frequency high-voltage power supply when it is in pulse conduction state and the duty cycle within that integration step are collected according to the set integration step size. The integration step size refers to the time interval between two adjacent accumulations during numerical integration. Collecting the secondary current when it is in pulse conduction state means obtaining the secondary current only during the actual conduction period of the high-voltage pulse. This current reflects the corona discharge intensity during conduction and is not affected by the pulse interval.

[0076] In step S22, the collected secondary current is numerically integrated using the duty cycle as a weight according to the following formula to obtain the dust load characterization value corrected for the duty cycle.

[0077] ;

[0078] In the formula, The dust load is represented by the value (mA·s). For the first The secondary current (mA) collected when the high-frequency high-voltage power supply is in pulse conduction state within one integration step. For the first The duty cycle of the high-frequency high-voltage power supply output pulse within one integration step, dimensionless; The integration step size is (s); This is the summation operator; is the index of the integration step, which is dimensionless.

[0079] The above equation is a numerical integration of the current using the rectangular method, which accumulates the effective transport charge within each integration step. Wherein, the... Within each integration step, the actual charge transported by the pulse conduction current is approximately equal to the conduction current multiplied by the conduction time. Since the conduction time equals the duty cycle multiplied by the integration step, the charge contribution at each step is the product of the secondary current, the duty cycle, and the integration step. Summing these values ​​over each step yields the dust load characterization value. Because the duty cycle is already factored into the integration, the dust load characterization value still corresponds to the actual transported charge even when the duty cycle is dynamically adjusted. The integration step is preferably on the order of seconds or smaller to balance computational complexity and accumulation accuracy.

[0080] In step S23, the dust load characterization value is compared with a set threshold. When the dust load characterization value reaches the set threshold, a dust removal trigger signal is generated. After the dust removal is completed, the dust load characterization value is cleared to zero and then re-accumulated. The set threshold corresponds to the upper limit of the dust load allowed to accumulate on the dust collecting electrode under the premise of ensuring clean cleaning and not causing spontaneous combustion risk due to excessive dust accumulation. It can be determined by calibration tests. Therefore, when the dust load is high, the secondary current is larger, the dust load characterization value increases faster, and the dust removal trigger is more frequent. When the dust load is low, the dust removal trigger is more sparse. The dust removal rhythm automatically increases or decreases with the dust load, so that unnecessary dust removal actions are reduced at low loads and excessive dust accumulation is not caused at high loads.

[0081] In step S3, when the dust load characterization value reaches the set threshold, a dust discharge trigger signal is generated, cutting off the high-frequency high-voltage power supply, stopping the induced draft fan, and switching the airlock to block the external dust-laden airflow from entering the polarized electric field. The induced draft fan refers to the fan that drives the dust-laden airflow through the polarized electric field. The airlock is a component installed on the airflow channel to block the airflow. The principle behind step S3 is that cutting off the high-frequency high-voltage power supply before dust discharge eliminates the electric field's adsorption force on the dust and prevents sparks during the dust discharge process. Stopping the induced draft fan and switching the airlock to block the entry of external dust-laden airflow prevents new dust-laden airflow from entering the cylinder, causing the airflow inside the cylinder to gradually decrease, creating conditions for subsequent dust removal at low airflow speeds. It should be noted that the airlock blocks the dust-laden airflow channel entering the polarized electric field from the outside, not the channel through which the dust falls back to the coal conveyor belt after dust removal; therefore, it does not affect the dust's fall.

[0082] In step S4, velocity data of the airflow velocity inside the cylinder decaying over time is collected, and the dust removal start-up delay required for the airflow velocity to decay to below the dust re-entrainment critical velocity is determined according to a first-order exponential decay model. The dust re-entrainment critical velocity refers to the minimum airflow velocity at which settled or attached dust begins to be re-entrained by the airflow. The principle behind step S4 is that if dust removal is performed when the airflow velocity inside the cylinder is still higher than the dust re-entrainment critical velocity, the dust dislodged by vibration and scraping will be re-entrained by the residual airflow, forming secondary dust. Therefore, dust removal should only be performed after the airflow velocity inside the cylinder decays to below the dust re-entrainment critical velocity. Since the decay of the airflow velocity takes time, and this time varies depending on the structure of each piece of equipment and the site conditions, the dust removal start-up delay is determined based on the measured decay law, rather than using a fixed empirical delay. Step S4 further includes steps S41, S42, S43, and S44.

[0083] In step S41, the wind speed sensing unit collects a sequence of airflow velocity decays over time inside the cylinder. The average airflow velocity collected within a preset stable time period after the cylinder stops and the external dust-laden airflow is blocked is taken as the residual airflow velocity. Data with velocity values ​​greater than the residual airflow velocity are selected from the velocity data sequence. The residual airflow velocity refers to the stable airflow velocity that still exists inside the cylinder after the cylinder stops and the external dust-laden airflow is blocked, and which no longer decreases significantly over time. It can be the average airflow velocity collected within the preset stable time period after the cylinder stops, or it can be a pre-calibrated residual velocity value. Only data with velocity values ​​greater than the residual airflow velocity are selected for subsequent fitting to ensure that the difference between the velocity value and the residual airflow velocity is positive, which can be achieved by taking the natural logarithm of the difference.

[0084] In step S42, the natural logarithm of the difference between the velocity value and the residual airflow velocity at each moment in the selected data is taken. The natural logarithm value is then fitted with a least-squares straight line at the corresponding moment. When the slope of the fitted line is less than 0 and the goodness of fit reaches a set threshold, the negative reciprocal of the slope of the fitted line is taken as the airflow velocity decay time constant. The airflow velocity decay time constant is a time quantity that characterizes the rate of airflow velocity decay; a larger value indicates slower decay. The goodness of fit is a measure of how well the fitted line matches the data. This step is based on a first-order exponential decay model. After the external dust-laden airflow is stopped and blocked, the airflow velocity inside the cylinder gradually relaxes towards the residual airflow velocity. Its change over time can be described by a first-order exponential decay, i.e., it satisfies the following equation:

[0085] ;

[0086] In the formula, Time elapsed after stopping The airflow velocity inside the cylinder at that time (m / s); The time elapsed after the engine stopped (in seconds); The airflow velocity (m / s) inside the cylinder at the initial moment of stopping; The residual airflow velocity is (m / s). The airflow velocity decay time constant (s); exp is a natural constant; or written as The power of represents the natural exponentiation operation.

[0087] First subtract from both sides of the above equation Taking the natural logarithm again, we get the following formula:

[0088] ;

[0089] In the formula, ln is the natural logarithm operator.

[0090] As can be seen from the above formula, the natural logarithm of the difference between the velocity value and the residual airflow velocity is related to time. The relationship is linear, and its slope is Therefore, by performing a least-squares linear fit on the natural logarithm of the difference between the velocity value and the residual airflow velocity and the corresponding time, the slope of the resulting fitted line is... Taking the negative reciprocal of the slope yields the airflow velocity decay time constant. When sensor noise or other reasons cause the slope of the fitted line to be no less than 0 or the goodness of fit to be lower than the set threshold, it indicates that the collected data does not conform to the first-order exponential decay law. In this case, the time constant is not calculated based on this, but abnormal processing is performed according to step S44.

[0091] In step S43, when the initial stop speed is greater than the critical dust re-entrainment speed, and the critical dust re-entrainment speed is greater than the residual airflow speed, and the airflow speed decay time constant is obtained in step S42, the decay time required for the airflow speed to decay from the initial stop speed to the critical dust re-entrainment speed is calculated according to the following formula, and the decay time is added to the set safety margin time to obtain the dust removal start delay.

[0092] ;

[0093] In the formula, The decay time is in seconds. The airflow velocity decay time constant (s) obtained in step S42; The airflow velocity (m / s) inside the cylinder at the initial moment of stopping; The residual airflow velocity is (m / s). The pre-defined critical velocity for dust re-entrainment (m / s); ln is the natural logarithm operator.

[0094] The above equation is derived from the first-order exponential decay model. (The equation is then broken down into its components.) Take the critical velocity of dust re-entrainment , that is to say equal Plus and The difference is then multiplied by of The power, after rearranging, yields... of The power equals and Difference divided by and The difference, taken as the natural logarithm of both ends, yields... Equal to the natural logarithm of the ratio, multiplied by The above formula is thus obtained. For this formula to be meaningful, the argument of the logarithm must be between 0 and 1, meaning the initial stop velocity must be greater than the critical dust re-entrainment velocity, and the critical dust re-entrainment velocity must be greater than the residual airflow velocity. In this case, the resulting decay time is positive. Adding a set safety margin time to the decay time as the dust removal start-up delay provides a margin to ensure that the airflow velocity inside the cylinder has indeed dropped below the critical dust re-entrainment velocity during dust removal. The dust removal start-up delay determined in this way matches the airflow decay law measured on-site, ensuring that dust removal is carried out at low airflow velocities, preventing the fallen dust from being re-entrained, and reducing secondary dust generation.

[0095] In step S44, abnormal situations are handled for those that do not meet the above conditions. When the initial stop speed is not greater than the critical dust re-entrainment speed, it indicates that the airflow speed inside the cylinder is not higher than the critical dust re-entrainment speed at the initial stop, and dust can be removed relatively quickly. Therefore, the dust removal start delay is set to the preset lower limit. When the critical dust re-entrainment speed is not greater than the residual airflow speed, or the slope of the fitted straight line in step S42 is not less than 0, or the goodness of fit is lower than the set threshold, it indicates that the airflow speed inside the cylinder is difficult to decay to below the critical dust re-entrainment speed or the decay pattern cannot be reliably identified. If dust removal is still delayed at the lower limit in this case, it may cause secondary dust generation. Therefore, the dust removal start delay is set to the preset upper limit, or the dust removal start is prohibited and an abnormal alarm is issued. Thus, under various operating conditions, the dust removal start time is biased towards avoiding secondary dust generation.

[0096] In step S5, after the disc-shaped corona electrode is discharged to a safe potential via a discharge resistor, and after a dust removal start-up delay from the moment of shutdown, the dust removal mechanism is activated to clean the disc-shaped corona electrode and the dust collecting electrode. The cleaned dust is then vibrated by the soft curtain of the lower buffer unloading hopper and falls back onto the coal conveyor belt for recycling. The discharge resistor is a resistor connected between the disc-shaped corona electrode and ground, used to discharge residual charge on the corona electrode to ground after the high-frequency, high-voltage power supply is cut off. The safe potential is the potential at which contact with a human body or component will not result in electric shock. The principle of residual charge discharge is that residual charge may still remain on the disc-shaped corona electrode and its distributed capacitance after the high-frequency, high-voltage power supply is cut off. If mechanical cleaning is started without discharge, there is a risk of electric shock and discharge. Therefore, the corona electrode is first discharged to a safe potential via the discharge resistor before the dust removal mechanism is activated.

[0097] The specific process of starting the dust removal mechanism for dust cleaning in step S5 is as follows: the dust removal motor drives the disc-shaped corona electrode to rotate via an insulated transmission assembly, causing the spikes on the disc-shaped corona electrode to contact and scrape against the fixed dust scraper mounted on an insulated bracket to remove the accumulated dust on the spikes; simultaneously, a vibrator located in the middle of the cylinder strikes the cylinder wall to remove the accumulated dust on the inner wall of the dust collecting electrode; and the soft curtain vibration mechanism drives the soft curtain at the bottom of the lower buffer unloading hopper to vibrate, causing the cleaned dust to fall back onto the coal conveyor belt. The insulated transmission assembly refers to the transmission mechanism that transmits motion and maintains electrical insulation between the dust removal motor and the disc-shaped corona electrode on the high-voltage side. The fixed dust scraper is a component that is fixed relative to the machine body, contacts the spikes of the disc-shaped corona electrode when it rotates, and scrapes off the accumulated dust. It is mounted on an insulated bracket to maintain insulation from the machine body, avoiding short circuits due to direct electrical connection with the corona electrode, and together with the above-mentioned residual charge discharge, ensures the safety of the dust cleaning process. The method of using a rotating disc-shaped corona electrode to scrape against a fixed dust scraper, compared to simple vibration cleaning, can promptly remove accumulated dust, including sticky dust, adhering to the spikes, maintaining good discharge performance of the corona electrode. The soft curtain refers to a curtain-like component made of flexible material located at the bottom of the lower buffer unloading hopper. Driven by a soft curtain vibration mechanism, it vibrates, causing dust falling into the lower buffer unloading hopper to be shaken off and fall back onto the coal conveyor belt. The fallen dust is then transported along with the coal conveyor belt for recycling and reuse, eliminating the need for a separate ash conveying system and avoiding secondary pollution.

[0098] Before the dust-laden airflow passes through the polarized electric field from bottom to top, it can be pre-treated. Specifically, the dust-laden airflow first enters a pre-buffered unloading device to slow down. Heavier dust particles in the airflow settle in the pre-buffered unloading device and fall back onto the coal conveyor belt. The remaining airflow containing fine dust first passes through a steel screen to remove impurities, and then passes through a water mist spraying device in the air distribution box to humidify it before entering the polarized electric field. The pre-buffered unloading device is a component installed before the dust-laden airflow enters the polarized electric field to slow down the airflow and allow heavier dust particles to settle naturally. The steel screen is used to prevent debris such as cloth strips, plastic films, and waste paper from adhering to the electrodes with the dust-laden airflow and causing continuous flashover or ignition hazards. The water mist spraying device is used to spray water mist into the dust-laden airflow. Setting up a pre-buffered unloading device allows heavier dust to settle and fall back first, which can reduce the amount of dust that needs to be captured by the electric field and reduce energy consumption. Spraying water mist into the dust-laden airflow to humidify it can reduce the resistivity of high resistivity dust, making it easier for it to be captured by the electric field. At the same time, the water mist also has an inhibitory effect on coal dust sparks.

[0099] To ensure safety, an interlock is installed between the water mist spraying system and the high-frequency high-voltage power supply. Power is supplied to the polarized electric field in step S1 only when the spray flow rate and water pressure are not lower than the set flow rate and water pressure, the wall temperature within the polarized electric field is higher than the preset dew point safety threshold, and the condensation sensor is not activated. If the spray flow rate is lower than the set flow rate, water pressure is lower than the set water pressure, the condensation sensor is activated, or the wall temperature is lower than the preset dew point safety threshold, the output of the high-frequency high-voltage power supply is reduced or cut off. The preset dew point safety threshold refers to the lower limit of wall temperature preset to prevent condensation on the surface of high-voltage insulating components. The principle behind this interlock is that the humidification, resistance reduction, and fire prevention effects are only effective when the spray is normal; therefore, power should not be supplied when the spray flow rate or water pressure is insufficient. When the wall temperature is lower than the dew point safety threshold or the condensation sensor is activated, condensation may form on the surface of the high-voltage insulating components, leading to surface creep and flashover; therefore, the high-voltage output should be reduced or cut off. This balances the beneficial effects of humidification and resistance reduction with the safety requirements of preventing condensation and flashover.

[0100] This invention also designs a DMC polarized electrostatic precipitator to implement the above method, referring to... Figure 5 The system includes a polarized electric field unit, a high-frequency high-voltage power supply module, a sampling unit, a wind speed sensing unit, an induced draft fan, a wind shut-off device, a dust removal mechanism, a lower buffer unloading hopper, and a controller. This equipment is an independent dust removal unit integrating the main body, high-voltage insulation, and electrical control components. It can be installed individually or in combination on the upper part of the feed chute of the coal conveyor belt for on-site dust collection and discharge.

[0101] The polarized electric field unit includes a cylinder serving as a grounded dust collection electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular baffle plate coaxial with and below the disc-shaped corona electrode. The diameter of the circular baffle plate is smaller than the inner diameter of the cylinder, and an annular inflow channel is formed between the circular baffle plate and the inner wall of the cylinder. This allows the dust-laden airflow to bypass the central direct impact area of ​​the disc-shaped corona electrode before entering the electric field, thus guiding the airflow to the high-efficiency region of the electric field and reducing dust accumulation on the corona electrode. The disc-shaped corona electrode is connected to the high-voltage output terminal of the high-frequency high-voltage power supply module via a high-voltage connector to receive high voltage. The disc-shaped corona electrode is also grounded via a discharge resistor to discharge residual charge after the high-frequency high-voltage power supply is disconnected. The cylinder serves as the grounded dust collection electrode, and its inner wall is the working surface for collecting dust.

[0102] The high-frequency, high-voltage power supply module is a high-frequency switching power supply with an adjustable output pulse duty cycle. Its control terminal is connected to the controller, and the duty cycle of its output pulse is adjusted by the controller. The use of a high-frequency switching power supply results in a smaller power supply body, and the adjustable duty cycle provides the basis for the aforementioned adaptive power supply adjustment. The sampling unit is connected to the secondary output circuit of the high-frequency, high-voltage power supply module, and its signal output terminal is connected to the controller. It outputs the collected secondary voltage and secondary current to the controller, providing data for the identification of resistance-related operating conditions and the accumulation of dust load. The wind speed sensing unit is located inside the cylinder, and its signal output terminal is connected to the controller. It outputs the airflow velocity inside the cylinder to the controller, providing data for determining the dust removal start-up delay.

[0103] The induced draft fan and the airlock are located on the airflow channel of the polarized electric field unit. The induced draft fan is used to drive the dust-laden airflow through the polarized electric field, and the airlock is used to block the entry of external dust-laden airflow before dust discharge. The control terminals of the induced draft fan and the airlock are respectively connected to the controller, and their operation and switching are controlled by the controller.

[0104] The dust removal mechanism includes a dust removal motor, a disc-shaped corona electrode driven by the dust removal motor through an insulated transmission assembly, a fixed dust scraper mounted on an insulated bracket and scraping against the spikes on the disc-shaped corona electrode, and a vibrator that strikes the cylindrical wall. The control terminal of the dust removal motor is connected to a controller. The insulated transmission assembly transmits motion between the dust removal motor and the disc-shaped corona electrode on the high-voltage side while maintaining insulation. The fixed dust scraper is mounted on an insulated bracket to insulate it from the machine body. Together, these components ensure safe implementation of the rotary scraping dust removal process. The vibrator strikes the cylindrical wall to dislodge accumulated dust from the inner wall of the dust collection electrode. The insulated transmission assembly may further include a cam mechanism driven by the dust removal motor, a spring, a corona electrode cleaning rod, and an insulated shaft. The corona electrode cleaning rod is connected to the disc-shaped corona electrode via the insulated shaft. The cam mechanism drives the disc-shaped corona electrode to rotate via the spring and the corona electrode cleaning rod. The high-voltage connection may be a conductive slip ring or a high-voltage flexible connection that allows relative rotation of the disc-shaped corona electrode to maintain the high-voltage connection during corona electrode rotation. The inner wall of the dust collecting electrode may be provided with a groove, and a semi-conductive polarization layer is attached to the groove. The semi-conductive polarization layer is connected to the cylinder at the same potential through a conductive connection point. Its function is to improve the dust collection performance and prevent the collected dust from falling off. At the same time, because it is connected to the cylinder at the same potential, it will not form insulation accumulation on the grounded dust collecting electrode.

[0105] The lower buffer unloading bin is located below the polarized electric field unit and above the coal conveyor belt. Its bottom is equipped with a soft curtain and a soft curtain vibration mechanism that drives the soft curtain to vibrate. The control terminal of the soft curtain vibration mechanism is connected to a controller. The lower buffer unloading bin is used to collect dust falling from the ash removal system. The soft curtain vibrates under the drive of the soft curtain vibration mechanism, causing the dust to fall back onto the coal conveyor belt.

[0106] The equipment may also include a pre-buffered unloading device, a steel screen, an air distribution box, a water mist spraying device, and a low-temperature condensation protection temperature switch, a condensation sensor, and an alarm connected to the controller. Along the flow direction of the dust-laden airflow, the pre-buffered unloading device is installed above the guide chute of the coal conveyor belt and located on the air inlet side of the polarized electric field unit. The steel screen is located on the air inlet side of the air distribution box. The water mist spraying device is located inside the air distribution box and interlocked with the controller via a water flow sensor switch and a water pressure switch. The air distribution box is located between the steel screen and the polarized electric field unit. The low-temperature condensation protection temperature switch and the condensation sensor are located inside the polarized electric field unit. The low-temperature condensation protection temperature switch is used to detect when the wall temperature inside the polarized electric field unit is lower than a preset dew point safety threshold. The alarm is used to issue an audible and visual alarm. The components are arranged sequentially along the airflow direction, allowing the dust-laden airflow to first slow down and settle, then filter out impurities, then humidify, and finally enter the electric field.

[0107] The controller's signal input terminals are connected to the sampling unit and the wind speed sensing unit, respectively. The controller's control terminals are connected to the high-frequency high-voltage power supply module, the induced draft fan, the airlock, the dust removal motor, and the soft curtain vibration mechanism, respectively. The controller is the core of the equipment's control. It determines the specific resistance-related operating condition index based on the secondary voltage and secondary current output by the sampling unit and adjusts the duty cycle of the high-frequency high-voltage power supply module's output pulse accordingly. It integrates the secondary current with the duty cycle as a weight to obtain the dust load characterization value. When the dust load characterization value reaches a set threshold, it cuts off the high-frequency high-voltage power supply module, stops the induced draft fan, and switches the airlock to a state that blocks the entry of external dust-laden airflow. It determines the dust removal start delay based on the airflow velocity output by the wind speed sensing unit, discharges the air to a safe potential through the discharge resistor at the disc-shaped corona electrode, and controls the dust removal motor and soft curtain vibration mechanism to operate after the dust removal start delay. The controller also reduces or cuts off the output of the high-frequency high-voltage power supply module and issues an audible and visual alarm when the condensation sensor or the low-temperature condensation protection temperature switch is activated. Through the aforementioned connection and control relationships of the various components, the equipment can realize the aforementioned DMC polarized electrostatic dust removal method, and due to its integrated structure and on-site installation, it is suitable for dust-generating sections with narrow on-site spaces.

[0108] The following embodiments use on-site dust removal at the outlet of the conveyor belt chute in a coal conveying system of a thermal power plant as an application example. The DMC polarized electrostatic precipitator method is implemented according to steps S1 to S5 of this invention. The operating parameters of each embodiment cover different ranges of resistivity, duty cycle, dust load, and airflow velocity decay time constant. The calibration parameters for each embodiment are: a lower limit of slope of 0.022 mA / kV, an upper limit of slope of 0.085 mA / kV, a lower limit of duty cycle of 0.30, and an upper limit of duty cycle of 0.90.

[0109] To enable those skilled in the art to better understand the technical solution of the present invention, the following describes the present invention in further detail with reference to the on-site dust removal at the outlet of the conveyor belt chute in the coal conveying system of a thermal power plant as an application scenario. These embodiments are used to explain the present invention and not to limit it. Each embodiment of the present invention implements the DMC polarized electrostatic dust removal method according to steps S1 to S5 of the present invention. The operating conditions of each embodiment cover different ranges of resistivity, duty cycle, dust load, and airflow velocity decay time constant.

[0110] Example 1, in Example 1, the resistivity of the dust is approximately This is a medium resistivity, medium dust load operating condition. In step S1, the secondary voltage and secondary current during the high-frequency high-voltage power supply's boost process are collected; in step S11, the volt-ampere characteristic data sequence is collected; in step S12, the data segment with secondary voltage greater than the corona initiation voltage is fitted with a least-squares straight line to obtain a slope of approximately 0.050 mA / kV; in step S13, this slope is normalized to obtain a resistivity-related operating condition index of approximately 0.556; in step S14, the duty cycle of approximately 0.567 is determined from this index and power is supplied to the polarization electric field accordingly. In step S2, the secondary current of approximately 2.65 mA during pulse conduction is collected; in steps S21 and S22, this secondary current is integrated with the duty cycle as a weight to obtain the dust load characterization value; in step S23, a dust discharge trigger signal is generated when the dust load characterization value reaches a set threshold. In step S3, the high-frequency high-voltage power supply is cut off, the induced draft fan is stopped, and the airlock is switched to block the entry of external dust-laden airflow. The initial stop velocity under this condition is approximately 5.5 m / s, the residual airflow velocity is approximately 0.05 m / s, and the critical dust re-entrainment velocity is approximately 0.8 m / s. In step S4, the airflow velocity decay time constant obtained from fitting the wind speed decay data in steps S41 to S43 is approximately 1.6 s. The calculated decay time is approximately 3.17 s, which, when added to the safety margin, yields a dust removal start-up delay of approximately 3.57 s. In step S5, after the disc-shaped corona electrode discharges to a safe potential via a discharge resistor, the dust removal mechanism is activated to clean the dust. The cleaned dust falls back onto the coal conveyor belt after being vibrated by the soft curtain of the lower buffer unloading hopper.

[0111] Example 2, in which the resistivity of the dust is approximately This is a high resistivity, high dust load operating condition, and the similarities with Example 1 will not be repeated. In step S12, the slope is approximately 0.022 mA / kV; in step S13, the resistivity-related operating condition index is approximately 1.000; and in step S14, the duty cycle is determined to be approximately 0.300, meaning that power is supplied to the polarized electric field in a narrow pulse intermittent manner. In step S21, the secondary current during pulse conduction is approximately 7.30 mA. The initial stop velocity of this operating condition is approximately 6.5 m / s, the residual airflow velocity is approximately 0.08 m / s, and the critical dust re-entrainment velocity is approximately 0.9 m / s. In step S4, the airflow velocity decay time constant is fitted to approximately 2.0 s, the decay time is calculated to be approximately 4.12 s, and the dust removal start-up delay is approximately 4.52 s.

[0112] Example 3, in which the resistivity of the dust is approximately This is a low resistivity, low dust load operating condition, and the similarities with the aforementioned embodiments will not be repeated. In step S12, the slope is obtained to be approximately 0.085 mA / kV; in step S13, the resistivity-related operating condition index is obtained to be approximately 0.000; and in step S14, the duty cycle is determined to be approximately 0.900, meaning that power is supplied to the polarized electric field in a nearly continuous manner. In step S21, the secondary current during pulse conduction is collected to be approximately 0.95 mA. The initial stop velocity of this operating condition is approximately 4.5 m / s, the residual airflow velocity is approximately 0.04 m / s, and the critical dust re-entrainment velocity is approximately 0.7 m / s. In step S4, the airflow velocity decay time constant is fitted to be approximately 1.2 s, the decay time is calculated to be approximately 2.29 s, and the dust removal start-up delay is approximately 2.69 s.

[0113] Comparative Example 1: In Comparative Example 1, the duty cycle adaptive power supply in step S1 of the present invention is not used. Instead, a constant duty cycle is used to supply power to the polarized electric field. The duty cycle is always taken as 0.90. The rest is the same as in each embodiment. This is used to compare the effect of step S1 on dust removal efficiency and electric field power consumption under different specific resistance conditions.

[0114] Comparative Example 2: In Comparative Example 2, the charge integration-based dust removal in steps S2 and S3 of the present invention is not used. Instead, dust removal is triggered at a fixed period of 6 minutes. The rest is the same as in each embodiment. This is used to compare the effect of step S2 on the number of dust removals and the energy consumption of the dust removal mechanism under different dust load conditions.

[0115] Comparative Example 3: In Comparative Example 3, the dust discharge start delay determined by the first-order exponential decay model in step S4 of the present invention is not adopted. Instead, a fixed empirical delay is used to trigger dust discharge. The dust discharge delay is 1.0s. The rest is the same as in each embodiment. This is used to compare the effect of step S4 on the dust re-entrainment rate, i.e., secondary dust.

[0116] Comparative Example 4: In Comparative Example 4, the duty cycle-weighted correction in step S22 of the present invention is not used. Instead, the secondary current during the pulse conduction period is directly integrated without multiplying by the duty cycle. The rest is the same as in each embodiment. This is used to compare the effect of duty cycle weighting in step S22 on the accuracy of dust load characterization.

[0117] Experimental Example 1: In Experimental Example 1, the methods of Examples 3, 1, and 2, as well as the method of Comparative Example 1, were used. At a specific resistance of approximately... ,about Peace Treaty The dust removal efficiency of Examples 3, 1, 2, and 1 (Comparative Example 1) was tested under three operating conditions. The relative electric field power consumption of Examples 3, 1, and 2 was tested using the electric field power consumption of Comparative Example 1 as a benchmark. The test results showed that the dust removal efficiency of Comparative Example 1 under low, medium, and high resistivity conditions was approximately 99.5%, 98.5%, and 91.0%, respectively; the dust removal efficiency of Example 3 was approximately 99.5% under low resistivity condition; that of Example 1 was approximately 99.3% under medium resistivity condition; and that of Example 2 was approximately 98.0% under high resistivity condition. Using the electric field power consumption of Comparative Example 1 as a benchmark, the relative electric field power consumption of Examples 3, 1, and 2 were approximately 100%, 63%, and 33%, respectively.

[0118] Experimental results are as follows Figure 1 As shown, Figure 1 In (a), the horizontal axis from left to right represents the three sets of comparisons: Example 3 and Comparative Example 1, Example 1 and Comparative Example 1, and Example 2 and Comparative Example 1; the vertical axis represents the dust removal efficiency. Figure 1 In (b), the horizontal axis from left to right represents the same three sets of comparisons, and the vertical axis represents the relative electric field power consumption; Examples 3, 1, and 2 are represented by brown, dark blue, and green bars, respectively, while Comparative Example 1 is represented by red bars.

[0119] Depend on Figure 1 It can be seen that, Figure 1 In (a), under low resistivity conditions, the dust removal efficiency of Example 3 and Comparative Example 1 is approximately 99.5%, which is comparable. Under medium resistivity conditions, Example 1 achieves approximately 99.3%, slightly higher than Comparative Example 1's approximately 98.5%. Under high resistivity conditions, Example 2 achieves approximately 98.0%, significantly higher than Comparative Example 1's approximately 91.0%. This indicates that the higher the resistivity, the greater the difference in dust removal efficiency between the examples and Comparative Example 1. Figure 1 In (b), the relative electric field power consumption of Example 3 is about 100%, which is comparable to that of Comparative Example 1. Example 1 is about 63% and Example 2 is about 33%. That is, the higher the resistivity, the lower the relative electric field power consumption. This indicates that under high resistivity conditions, the dust removal efficiency of Example 2 is significantly higher than that of Comparative Example 1, and the electric field power consumption of Examples 1 and 2 is significantly lower than that of Comparative Example 1.

[0120] When the resistivity of dust is high, the charge carried by the charged dust reaching the collecting electrode is not easily discharged. A reverse electric field is established on both sides of the dust layer, and breakdown discharge is formed to form a back corona, which forces the corona current to decrease and the dust collection efficiency to decrease accordingly. In Example 2, after identifying the high resistivity-related working condition based on the volt-ampere characteristics in step S1, step S14 reduces the duty cycle and supplies power with narrow pulses intermittently, so that the dust layer can discharge charge during the pulse interval and suppress the back corona. Therefore, the dust removal efficiency of Example 2 under high resistivity conditions is higher than that of Comparative Example 1. The reduction of the duty cycle shortens the conduction time of the high voltage pulse and the electric field energy is delivered on demand. Therefore, the electric field power consumption of Examples 1 and 2 is lower than that of Comparative Example 1. Under low resistivity conditions, the duty cycle obtained by Example 3 in step S14 is the same as the constant duty cycle of Comparative Example 1. Therefore, the dust removal efficiency and electric field power consumption of the two are comparable.

[0121] Experimental Example 2: In Experimental Example 2, the methods of Examples 1, 2, and 3, as well as Comparative Examples 2 and 4, were used. The experimental results are as follows: Figure 2 .exist Figure 2 In section (a), to examine the performance of the duty cycle-weighted integral in step S22 when the duty cycle changes, the duty cycle-weighted integral method of step S22 in Example 1 and the duty cycle-ignoring integral method in Comparative Example 4 were used to process the same set of pulse conduction current data, wherein the duty cycle decreased from 0.90 to 0.30 due to the increase in specific resistance; Figure 2 In section (b), during a 60-minute runtime, the number of dust removals triggered by charge integration in step S2 for Examples 1, 2, and 3 was compared with the number of dust removals in Comparative Example 2 with a fixed-cycle dust removal. The relative dust removal mechanism energy consumption of Examples 1, 2, and 3 was calculated based on the energy consumption of the dust removal mechanism in Comparative Example 2. The test results showed that after the duty cycle decreased from 0.90 to 0.30, the integral of Comparative Example 4, ignoring the duty cycle, continued to rise rapidly and was significantly higher than the duty cycle-weighted integral of Example 1. The dust load characterization value of Example 1 matched the actual transported charge. Within 60 minutes, the number of dust removals for Examples 1, 2, and 3 were 4, 6, and 2, respectively, while that for Comparative Example 2 was 10. The relative dust removal mechanism energy consumption for Examples 1, 2, and 3 was approximately 40%, 60%, and 20%, respectively. Figure 2 In (a), the horizontal axis represents the running time and the vertical axis represents the dust load characterization value. The duty cycle weighted integral of Example 1 and the duty cycle ignoring integral of Comparative Example 4 are represented by dark blue solid lines and orange-red dashed lines, respectively, and the set threshold line and the duty cycle decrease time line are marked. Figure 2 In (b), the horizontal axis from left to right represents the three control groups: Example 1 and Comparative Example 2, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 2. The vertical axis represents the number of dust removals within 60 minutes. Example 1, Example 2, and Example 3 are represented by dark blue, green, and brown bars, respectively, while Comparative Example 2 is represented by orange-yellow bars.

[0122] Depend on Figure 2 It can be seen that, Figure 2 In example (a), after the duty cycle decreased from 0.90 to 0.30, the slope of the integral curve of Comparative Example 4, which ignores the duty cycle, remained unchanged and continued to rise at the original rate. However, the slope of the duty cycle-weighted integral curve of Example 1 decreased as the duty cycle decreased, and the two were clearly separated, indicating that ignoring the duty cycle would overestimate the dust accumulation load. Figure 2 In Example (b), the number of dust removals in Examples 1, 2, and 3 were 4, 6, and 2 times, respectively, all less than the 10 times of fixed-cycle dust removal in Comparative Example 2. Moreover, the number of dust removals increased with the increase of dust load, indicating that the duty cycle weighted integral of Example 1 made the dust load characterization value unaffected by the dynamic adjustment of the duty cycle. The number of on-demand dust removals in Examples 1, 2, and 3 increased or decreased automatically with the dust load and were all less than the fixed-cycle dust removals in Comparative Example 2.

[0123] The secondary current reflects the corona discharge intensity during pulse conduction. The actual charge transported to the dust collecting electrode within a single integration step is equal to the conduction current multiplied by the conduction time, and the conduction time is equal to the duty cycle multiplied by the integration step. Therefore, the dust load characterization value obtained by integrating with the duty cycle as the weight in step S22 of Example 1 corresponds to the actual transported charge. Comparative Example 4 does not consider the duty cycle, so it overestimates the dust load after the duty cycle decreases. In Step S23 of Examples 1, 2, and 3, dust removal is triggered only when the characterization value reaches the set threshold. Example 2, with its high dust load, has a large current and a fast characterization value growth, resulting in more frequent dust removal. Example 3, with its low dust load, has sparser dust removal. Therefore, the number of dust removals in each example automatically increases or decreases with the load and is less than the fixed-cycle dust removal in Comparative Example 2, thereby reducing the energy consumption of the dust removal mechanism.

[0124] Experimental Example 3: In Experimental Example 3, the methods of Examples 1, 2, and 3, as well as the method of Comparative Example 3, were used. After stopping the machine and blocking the external dust-laden airflow, the decay data of the airflow velocity inside the cylinder over time were collected under the operating conditions of Examples 1, 2, and 3, respectively. The dust removal start-up delay was determined according to the first-order exponential decay model, and the dust re-entrainment rate of Examples 1, 2, and 3 during dust removal at their respective dust removal start-up delays was tested, along with the dust re-entrainment rate of Comparative Example 3 during dust removal at a fixed delay of 1.0 s. The test results show that the dust removal start-up delays for Examples 1, 2, and 3 are approximately 3.57s, 4.52s, and 2.69s, respectively, with corresponding dust re-entrainment rates of approximately 1.6%, 2.4%, and 0.9%, all below 3%. In Comparative Example 3, the airflow velocity inside the cylinder during dust removal with a delay of 1.0s is still much higher than the critical velocity for dust re-entrainment, with dust re-entrainment rates of approximately 98%, 98%, and 97% under the conditions of Examples 1, 2, and 3, respectively.

[0125] Experimental results Figure 3As shown, Figure 3 In (a), the horizontal axis represents the time after the rotation stops, and the vertical axis represents the airflow velocity inside the cylinder. The wind speed decay curves of Example 1, Example 2, and Example 3 are represented by solid lines in dark blue, green, and brown, respectively. The dust removal start point of each example is marked with a pentagon of the same color, and the critical speed line of the entrainment and the fixed delay line of Comparative Example 3 are also marked. Figure 3 In (b), the horizontal axis from left to right represents the three sets of controls: Example 1 and Comparative Example 3, Example 2 and Comparative Example 3, and Example 3 and Comparative Example 3. The vertical axis represents the dust re-entrainment rate. Example 1, Example 2, and Example 3 are represented by dark blue, green, and brown bars, respectively, while Comparative Example 3 is represented by gray bars.

[0126] Depend on Figure 3 It can be seen that, Figure 3 In example (a), the wind speed decay curves of each embodiment drop to near the critical dust re-entrainment velocity at their respective dust removal start-up delays, while the wind speed decay curves of Comparative Example 3 at the fixed 1.0s delay line are still much higher than the critical dust re-entrainment velocity; Figure 3 In (b), the re-entrainment rates of Examples 1, 2, and 3 under the dust removal start-up delay were all below 3%, while the re-entrainment rate of Comparative Example 3 under the fixed 1.0s delay was above 95%. This indicates that the airflow velocity inside the cylinder during dust removal in Examples 1, 2, and 3 under their respective determined dust removal start-up delays had dropped below the critical dust re-entrainment velocity, and the dust re-entrainment rate was below 3%, which was significantly lower than the dust re-entrainment rate of Comparative Example 3 under the fixed short delay.

[0127] Whether the dust removed by rapping and scraping is re-rolled depends on the airflow velocity inside the cylinder during dust removal. When the airflow velocity is higher than the critical velocity for dust re-entrainment, the dust is easily re-rolled, forming secondary dust. In Example 1, Example 2, and Example 3, step S4 calculates the dust removal start-up delay required for the airflow velocity to decay to below the critical velocity for dust re-entrainment based on the measured wind speed decay data using a first-order exponential decay model. Dust removal is then performed after the airflow velocity drops below this critical velocity, resulting in a low dust re-entrainment rate. In Comparative Example 3, an excessively short fixed delay is used, and the airflow velocity remains high during dust removal, leading to a large amount of dust being re-rolled.

[0128] Experimental Example 4 employed the methods of Example 1 and Comparative Examples 1, 2, and 3. Using the measured parameters of Example 1 under the conditions of resistivity and medium dust load, the dust removal efficiency, relative electric field power consumption, relative dust removal mechanism energy consumption, and dust re-entrainment rate were tested. These parameters were then compared with the corresponding parameters of Comparative Examples 1, 2, and 3 under the same conditions as Example 1. The test results showed that Example 1 achieved a dust removal efficiency of approximately 99.3%, a relative electric field power consumption of approximately 63%, a relative dust removal mechanism energy consumption of approximately 40%, and a dust re-entrainment rate of approximately 1.6%. Comparative Example 1 achieved a dust removal efficiency of approximately 98.5% and a relative electric field power consumption of 100% under the conditions of Example 1. Comparative Example 2 achieved a relative dust removal mechanism energy consumption of 100%. Comparative Example 3 achieved a dust re-entrainment rate of approximately 98% under the conditions of Example 1.

[0129] Experimental results are as follows Figure 4 As shown, Figure 4 The horizontal axis represents four indicators: dust removal efficiency, relative electric field power consumption, relative dust removal mechanism energy consumption, and dust re-entrainment rate; the vertical axis represents the values ​​of each indicator. Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are represented by dark blue, red, orange-yellow, and gray bars, respectively. Figure 4 It can be seen that, in terms of dust removal efficiency, the dark blue bar of Example 1 is slightly higher than the red bar of Comparative Example 1; in terms of relative electric field power consumption, the dark blue bar of Example 1 is significantly lower than the red bar of Comparative Example 1; in terms of relative dust removal mechanism energy consumption, the dark blue bar of Example 1 is significantly lower than the orange-yellow bar of Comparative Example 2; and in terms of dust re-entrainment rate, the dark blue bar of Example 1 is significantly lower than the gray bar of Comparative Example 3. This indicates that, under the conditions of medium resistivity and medium dust load, Example 1 has a dust removal efficiency no lower than Comparative Example 1, lower electric field power consumption, lower dust removal mechanism energy consumption, and lower dust re-entrainment rate than Comparative Example 3. The lower relative electric field power consumption is due to step S1 of this invention determining the duty cycle according to the relevant operating condition index of resistivity, thus allowing power to be delivered on demand; the lower relative dust removal mechanism energy consumption is due to step S2 discharging dust on demand according to the dust load characterization value; and the lower dust re-entrainment rate is due to step S4 determining the dust removal start delay according to the airflow attenuation law. The operating condition of Example 1 is medium resistivity, and its dust removal efficiency advantage over Comparative Example 1 is relatively small.

[0130] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A DMC polarized electrostatic dust removal method, characterized in that, The dust-laden airflow passes through a polarized electric field from bottom to top. This polarized electric field consists of a cylinder serving as a grounded dust-collecting electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular baffle plate coaxial with and below the disc-shaped corona electrode. An annular inflow channel is formed between the circular baffle plate and the inner wall of the cylinder. The dust-laden airflow bypasses the central direct impact area of ​​the disc-shaped corona electrode and enters the polarized electric field through this annular inflow channel. The process includes the following steps: S1, during the power supply and dust removal stage, the secondary voltage and secondary current of the high-frequency high-voltage power supply are collected. Based on the volt-ampere characteristic of the secondary current changing with the secondary voltage, the specific resistance related operating condition index is obtained. Based on the specific resistance related operating condition index, the duty cycle of the output pulse of the high-frequency high-voltage power supply is adjusted to supply power to the polarized electric field. S2, During the power supply and dust removal stage, the secondary current during the pulse conduction period is collected, and the collected secondary current is integrated with the duty cycle as the weight to obtain the dust load characterization value that characterizes the dust accumulation load of the dust collecting electrode after duty cycle correction. S3, when the dust load characterization value reaches the set threshold, a dust discharge trigger signal is generated, the high-frequency high-voltage power supply is cut off, the induced draft fan is stopped, and the airlock is switched to the state of blocking the external dust-laden airflow from entering the polarized electric field. S4. Collect velocity data of airflow velocity decaying over time inside the cylinder, and determine the dust removal start delay required for the airflow velocity to decay to below the critical velocity for dust re-entrainment according to the first-order exponential decay model. S5, after the disc-shaped corona electrode is discharged to a safe potential through the discharge resistor and after the dust discharge start delay from the moment of stop, the dust discharge mechanism is started to clean the disc-shaped corona electrode and the dust collection electrode, so that the cleaned dust falls back to the coal conveyor belt for recycling after the soft curtain of the lower buffer unloading hopper vibrates.

2. The DMC polarized electrostatic dust removal method according to claim 1, characterized in that, Step S1 includes: S11, based on the lower limit and upper limit of the slope obtained in advance under the conditions of determined electrode spacing, wind speed and spray state, at the beginning stage of the power supply control cycle, the high frequency high voltage power supply is controlled to raise the secondary voltage from the corona initiation voltage to the rated voltage, and the corresponding secondary current is synchronously collected at the set sampling period to obtain the volt-ampere characteristic data sequence composed of multiple sets of secondary voltage and secondary current. S12, Select a data segment from the current-voltage characteristic data sequence in which the secondary voltage is greater than the corona initiation voltage, perform least squares linear fitting on the secondary current and secondary voltage in the data segment, and use the slope of the fitted line as a characteristic quantity reflecting the polarization condition of the dust-laden airflow. S13, normalize the slope to a specific resistance-related operating condition index using the following formula: ,and ; In the formula, This refers to the operating condition index related to specific resistance; The slope obtained in step S12; This is the lower limit of the slope under pre-calibrated high specific resistance conditions; This is the pre-calibrated upper limit of the slope under low specific resistance conditions; when calculated according to the above formula... When less than 0, take The value is 0 when calculated according to the above formula. Take when greater than 1 =1; S14, determine the duty cycle of the high-frequency high-voltage power supply output pulse using the specific resistance-related operating condition index according to the following formula, and supply power to the polarization electric field with the determined duty cycle to obtain a power supply state matching the current polarization operating condition: ,and ; In the formula, The duty cycle of the output pulse of the high-frequency high-voltage power supply; The lower limit of the pre-set duty cycle; The upper limit of the pre-set duty cycle; The specific resistance-related operating condition index obtained in step S13.

3. The DMC polarized electrostatic dust removal method according to claim 2, characterized in that, The process of supplying power to the polarized electric field with a determined duty cycle in step S14 further includes: controlling the peak voltage of the high-frequency high-voltage power supply output pulse to operate below the spark initiation point; when a spark flashover is detected in the polarized electric field, first reducing the output voltage, and then raising the output voltage back to the target voltage that does not exceed the rated voltage and is lower than the current spark initiation point according to a pre-set multi-segment boost curve.

4. The DMC polarized electrostatic dust removal method according to claim 1, characterized in that, Step S2 includes: S21, starting from the end of the last dust removal, collect the secondary current of the high-frequency high-voltage power supply when it is in the pulse conduction state and the duty cycle within the set integral step size. S22, the collected secondary current is numerically integrated using the duty cycle as a weight according to the following formula to obtain the dust load characterization value corrected for the duty cycle: ； In the formula, This represents the dust load characterization value; For the first The secondary current collected when the high-frequency high-voltage power supply is in pulse conduction state within each integration step; For the first The duty cycle of the high-frequency high-voltage power supply output pulse within each integration step; This is the integration step size; This is the summation operator; The sequence number of the integration step; S23, compare the dust load characterization value with the set threshold, generate the dust discharge trigger signal when the dust load characterization value reaches the set threshold, and after the dust discharge is completed, clear the dust load characterization value to zero and then re-accumulate it to obtain a dust discharge rhythm that is automatically denser or sparser depending on the dust load.

5. The DMC polarized electrostatic dust removal method according to claim 1, characterized in that, Step S4 includes: S41, the wind speed sensing unit collects the velocity data sequence of the airflow velocity inside the cylinder as the velocity decays over time, and takes the average airflow velocity collected within a preset stable time period after the cylinder stops rotating and the external dust-laden airflow is blocked as the residual airflow velocity, and selects data with a velocity value greater than the residual airflow velocity from the velocity data sequence. S42, take the natural logarithm of the difference between the velocity value at each moment in the selected data and the residual airflow velocity, and perform least squares linear fitting on the natural logarithm value and the corresponding moment; when the slope of the fitted line is less than 0 and the goodness of fit reaches a set threshold, take the negative reciprocal of the slope of the fitted line as the airflow velocity decay time constant, and the fitting characterizes the first-order exponential decay of the airflow velocity. S43, when the initial stop speed is greater than the critical speed for dust re-entrainment, and the critical speed for dust re-entrainment is greater than the residual airflow speed, and the airflow speed decay time constant is obtained in step S42, the decay time required for the airflow speed to decay from the initial stop speed to the critical speed for dust re-entrainment is calculated according to the following formula, and the decay time is added to the set safety margin time to obtain the dust removal start delay: ,and ; In the formula, This refers to the decay time; The airflow velocity decay time constant obtained in step S42; The airflow velocity inside the cylinder at the initial moment of shutdown; The residual airflow velocity; The pre-calibrated critical velocity for dust re-entrainment; The natural logarithm operator; S44, when the initial speed at which the rotation stops is not greater than the critical speed of dust re-entrainment, the dust removal start delay is set to the lower limit of the preset delay; when the critical speed of dust re-entrainment is not greater than the residual airflow speed, or the slope of the fitted straight line is not less than 0, or the goodness of fit is lower than the set threshold, the dust removal start delay is set to the upper limit of the preset delay or the dust removal is prohibited and an abnormal alarm is issued, so as to obtain the dust removal start time to avoid secondary dust generation.

6. The DMC polarized electrostatic dust removal method according to claim 1, characterized in that, Step S5, which involves starting the dust removal mechanism, includes the following steps: after the high-frequency high-voltage power supply has been cut off and the disc-shaped corona electrode has been discharged to a safe potential via a discharge resistor, the dust removal motor drives the disc-shaped corona electrode to rotate via an insulated transmission assembly, causing the spikes on the disc-shaped corona electrode to contact and scrape against the fixed dust scraper mounted on an insulated bracket to remove the accumulated dust on the spikes; simultaneously, a vibrator located in the middle of the cylinder strikes the cylinder wall to remove the accumulated dust on the inner wall of the dust collection electrode; and the soft curtain vibration mechanism drives the soft curtain at the bottom of the lower buffer unloading hopper to vibrate, causing the cleared dust to fall back onto the coal conveyor belt.

7. The DMC polarized electrostatic dust removal method according to claim 1, characterized in that, Before the dust-laden airflow passes through the polarized electric field from bottom to top, it first enters a pre-buffer unloading device to slow down. Heavier dust particles in the airflow settle in the pre-buffer unloading device and fall back onto the coal conveyor belt. The remaining airflow containing fine dust first passes through a steel screen to remove impurities, and then passes through a water mist spraying device in the air distribution box to humidify before entering the polarized electric field. When the spray flow rate of the water mist spraying device is not lower than the set flow rate, the water pressure is not lower than the set water pressure, the wall temperature in the polarized electric field is higher than the preset dew point safety threshold, and the condensation sensor does not activate, step S1 supplies power to the polarized electric field. When the spray flow rate is lower than the set flow rate, the water pressure is lower than the set water pressure, the condensation sensor activates, or the wall temperature is lower than the preset dew point safety threshold, the output of the high-frequency high-voltage power supply is reduced or cut off.

8. A DMC polarized electrostatic precipitator for implementing the method according to any one of claims 1-7, characterized in that, It includes a polarized electric field unit, a high-frequency high-voltage power supply module, a sampling unit, a wind speed sensing unit, an induced draft fan, a wind shut-off device, a dust removal mechanism, a lower buffer unloading hopper, and a controller; The polarized electric field unit includes a cylinder serving as a grounded dust collection electrode, a disc-shaped corona electrode located at the center of the cylinder, and a circular shielding plate coaxial with and below the disc-shaped corona electrode. The diameter of the circular shielding plate is smaller than the inner diameter of the cylinder and forms an annular inflow channel with the inner wall of the cylinder. The disc-shaped corona electrode is connected to the high-voltage output terminal of the high-frequency high-voltage power supply module via a high-voltage connector. The disc-shaped corona electrode is also grounded via a discharge resistor. The high-frequency high-voltage power supply module is a high-frequency switching power supply with an adjustable output pulse duty cycle. The control terminal of the high-frequency high-voltage power supply module is connected to the controller. The sampling unit is connected to the secondary output circuit of the high-frequency high-voltage power supply module. The signal output terminal of the sampling unit is connected to the controller and is used to output the sampled secondary voltage and secondary current to the controller. The wind speed sensing unit is located inside the cylinder, and the signal output terminal of the wind speed sensing unit is connected to the controller to output the airflow speed inside the cylinder to the controller. The induced draft fan and the air shut-off device are located on the airflow channel of the polarized electric field unit, and the control terminals of the induced draft fan and the air shut-off device are respectively connected to the controller. The dust removal mechanism includes a dust removal motor, a disc-shaped corona electrode driven to rotate by the dust removal motor through an insulated transmission component, a fixed dust scraper mounted on an insulated bracket and scraping against the spikes on the disc-shaped corona electrode, and a vibrator that strikes the cylinder wall. The control terminal of the dust removal motor is connected to the controller. The lower buffer unloading bin is located below the polarized electric field unit and above the coal conveyor belt. The bottom of the lower buffer unloading bin is equipped with a soft curtain and a soft curtain vibration mechanism that drives the soft curtain to vibrate. The control end of the soft curtain vibration mechanism is connected to the controller. The controller's signal input terminals are connected to the sampling unit and the wind speed sensing unit, respectively. The controller's control terminals are connected to the high-frequency high-voltage power supply module, the induced draft fan, the airlock, the dust removal motor, and the soft curtain vibration mechanism, respectively. The controller is configured to: determine the specific resistance-related operating condition index based on the secondary voltage and secondary current output by the sampling unit and adjust the duty cycle of the output pulse of the high-frequency high-voltage power supply module accordingly; integrate the secondary current with the duty cycle as the weight to obtain the dust load characterization value; when the dust load characterization value reaches the set threshold, cut off the high-frequency high-voltage power supply module, stop the induced draft fan, and switch the airlock to the state of blocking the entry of external dust-laden airflow; determine the dust removal start delay based on the airflow speed output by the wind speed sensing unit, and control the dust removal motor and the soft curtain vibration mechanism to operate after the dust is discharged to a safe potential through the discharge resistor at the disc-shaped corona electrode and after the dust removal start delay.

9. The DMC polarized electrostatic precipitator according to claim 8, characterized in that, The insulated transmission assembly includes a cam mechanism driven by a dust removal motor, a spring, a corona cleaning rod, and an insulated shaft. The corona cleaning rod is connected to the disc-shaped corona electrode via the insulated shaft. The cam mechanism drives the disc-shaped corona electrode to rotate via the spring and the corona cleaning rod. The high-voltage connector is a conductive slip ring or a high-voltage flexible connector that allows relative rotation of the disc-shaped corona electrode. The inner wall of the dust collecting electrode is provided with a groove, and a semi-conductive polarization layer is attached to the groove. The semi-conductive polarization layer is connected to the cylinder at the same potential via a conductive connection point.

10. The DMC polarized electrostatic precipitator according to claim 8, characterized in that, It also includes a pre-buffer unloading device, a steel screen, an air distribution box, a water mist spraying device, and a low-temperature condensation protection temperature switch, a condensation sensor, and an alarm connected to the controller. Along the flow direction of the dust-laden airflow, the pre-buffer unloading device is installed on the upper part of the guide chute of the coal conveyor belt and located on the air inlet side of the polarized electric field unit. The steel screen is located on the air inlet side of the air distribution box. The water mist spraying device is located inside the air distribution box and is interlocked with the controller via a water flow sensor switch and a water pressure switch. The air distribution box is located between the steel screen and the polarized electric field unit. The low-temperature condensation protection temperature switch and the condensation sensor are located inside the polarized electric field unit. The low-temperature condensation protection temperature switch is used to detect that the wall temperature inside the polarized electric field unit is lower than the preset dew point safety threshold. The controller is configured to reduce or cut off the output of the high-frequency high-voltage power supply module and issue an audible and visual alarm when the condensation sensor or the low-temperature condensation protection temperature switch is activated. The high-frequency high-voltage power supply module, the sampling unit, and the controller are integrated with the polarized electric field unit to form one or more independent dust removal units installed on the upper part of the guide chute.

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