An electrostatic dust removal method using discharge bipolar control

Abstract

The present application relates to the technical field of high-voltage electrostatic dust removal, and provides an electrostatic dust removal method using discharge bipolar control, which controls the polarity of the power supply of the discharge electrode and the dust collecting plate of the electrostatic dust removal equipment, sets a threshold value to control the polarity reversal of the power supply, adjusts the vibration period and intensity of the dust collecting plate to improve the dust removal efficiency, the equivalent internal electric field formed after the smoke dust is charged and adsorbed on the two poles is superimposed with the external electric field formed between the discharge electrode and the dust collecting plate, the smoke dust charging rate is increased, and the movement speed of the charged particles is improved, the dust removal efficiency is greatly improved by using the means of superimposed and enhanced field strength of the adsorbed smoke dust and the external electric field, the dust removal time is obviously shortened, and the service life of the dust collecting plate is improved by reasonably reducing the vibration frequency of the dust collecting plate.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage electrostatic dust removal, and more particularly to an electrostatic dust removal method using discharge bipolar control. Background Art

[0002] With the rapid development of my country's economy, the scale of social production is expanding. The power, metallurgy, oil refining, chemical and other industries are all sources of air pollutants. The large amount of industrial dust they emit not only pollutes the air and harms human health, but also causes the loss of a large amount of valuable materials in some cases. Currently, the common electrostatic dust removal methods are mainly the following:

[0003] 1. DC electrostatic precipitator

[0004] Electrostatic precipitator power supplies initially employed a thyristor (SCR) phase-controlled AC voltage regulation structure, a technology that has since matured into a highly mature set of technologies. Consequently, traditional industrial frequency (50Hz) high-voltage switching power supplies are currently widely used, and single-phase SCR rectifier circuits are also quite popular. While their structure is simple and controllable, their removal efficiency is relatively low for high-resistance dust. To achieve this efficiency, DC electrostatic precipitators must rely on increasing the voltage to create corona discharge between the plates. Increasing the voltage itself increases the power output, which is why DC electrostatic precipitators consume a lot of energy.

[0005] 2. AC electrostatic dust removal

[0006] The disadvantages of traditional industrial frequency high-voltage electrostatic dust removal technology include: the transformer and filter are large in size, heavy in weight, and have high material costs; the control chassis is relatively bulky and occupies a large area; the power input is industrial frequency AC, and it is phase-shifted, resulting in a low power factor and causing great electromagnetic interference to the power grid, and poor electromagnetic compatibility; the waveform is single and the output ripple is large, making it unable to adapt to high-resistance working conditions and failing to meet the new requirements of dust emission standards in the environmental protection field.

[0007] 3. Pulse electrostatic dust removal

[0008] The pulse power supply method superimposes a pulse voltage with a microsecond pulse width on the DC high voltage to generate a sufficiently strong and uniform corona current density. Its main function is to suppress the back corona phenomenon formed by high-resistance dust within a certain range in the electric field, effectively reducing power consumption; but this power supply requires the addition of a high-voltage pulse generator and control system, which undoubtedly increases the complexity of the control system and the power supply cost.

[0009] 4. High-frequency electrostatic dust removal

[0010] The successful development and application of high-frequency power supplies can effectively address the shortcomings of industrial frequency power supplies. High-frequency electrostatic precipitator power supplies operate at frequencies of approximately 10kHz-40kHz, offering high dust removal efficiency, compact size, and high energy efficiency. These outstanding advantages are gradually being recognized within the industry. However, currently, domestically developed high-frequency, high-voltage power supplies for electrostatic precipitators remain at the low- to medium-power stage, with generally low output currents. This results in a relatively low charge capacity for dust within the electric field, hindering significant improvements in dust removal efficiency.

[0011] 5. Wet electrostatic dust removal

[0012] The disadvantages of wet electrostatic dust removal are: the sediment discharged by the wet dust collector needs to be processed, and the clarified washing water should be reused, otherwise it will not only cause secondary pollution, but also waste water resources; when purifying corrosive pollution, the washing water (or liquid) will have a certain degree of corrosiveness, so the dust removal equipment should have certain anti-corrosion measures; the wet dust collector is not suitable for purifying organic waste gas containing hydrophobic and hydraulic dust; the use of wet dust collectors in cold areas is prone to freezing, so anti-freeze measures should be taken. Summary of the Invention

[0013] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide an electrostatic dust removal method using bipolar discharge control. The invention improves the dust removal efficiency by controlling the polarity of the power supply of both the discharge electrode and the dust collecting plate of the electrostatic dust removal equipment, setting a threshold to control the polarity reversal of the power supply, and adjusting the vibration cycle and intensity of the dust collecting plate. It can not only reduce the vibration frequency, but also utilize the charged smoke adsorbed by the dust collecting plate before the polarity reversal to accelerate the adsorption of the smoke after the polarity reversal.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] An electrostatic dust removal method using bipolar discharge control is designed to add several dust collection chambers to the flue gas emission duct. The discharge electrodes and dust collecting plates in the dust collection chambers are used to adjust the vibration cycle and intensity of the dust collecting plates according to a set threshold value to improve the dust removal efficiency of flue gas emission. The method specifically includes the following steps:

[0016] Step 1. Install several particle concentration sensors in the dust collecting chamber, and set a reversal threshold for electrode reversal, an emission threshold for flue gas emission, and a particle concentration decrease rate threshold for the particle concentration in the dust collecting chamber in the control system;

[0017] Step 2. The power polarity of the dust collecting plate and discharge electrode in the dust collecting chamber is opposite. After the power is turned on, the smoke is fully charged and adsorbed on the dust collecting plate. A thickness tester is installed on the dust collecting plate to measure the dust accumulation thickness. Under the initial power polarity of the dust collecting plate and discharge electrode, the particles in the smoke are charged by the external electric field formed by the dust collecting plate and discharge electrode, and adsorbed on the dust collecting plate.

[0018] Step 3. When the particle concentration sensor detects that the particle concentration in the dust collecting chamber has reached a concentration threshold, the control system sends a signal, and the polarity of the dust collecting plate and the discharge electrode power supply is reversed. The equivalent internal electric field formed by the smoke particles adsorbed on the dust collecting plate is superimposed with the external electric field formed by the discharge electrode and the dust collecting plate, forming a comprehensive superimposed electric field, which accelerates the movement of particles in the smoke in the dust collecting chamber.

[0019] Step 4. After reversing the polarity of the power supply, when the thickness tester detects that the accumulated particle thickness of the dust collecting plate reaches the thickness threshold, and the particle concentration sensor measures that the particle concentration change rate is lower than the particle concentration decrease rate threshold, the control system issues a command to vibrate the dust collecting plate to remove the particles adsorbed on the dust collecting plate, so that the dust deposited on the dust collecting plate is shaken off and enters the dust collecting hopper and is discharged through the dust discharge device to recover useful materials, and the purified gas is discharged into the atmosphere; the control system controls the vibration cycle and intensity by receiving the accumulated particle thickness of the dust collecting plate;

[0020] Step 5. The control system receives the signal of the particle concentration in the dust collecting chamber and the signal of the particle thickness on the dust collecting plate. When the smoke concentration does not reach the emission concentration threshold of the current dust collecting chamber, steps 3 and 4 are repeated until the particle concentration of the smoke in the dust collecting chamber is lower than the emission concentration threshold of the current dust collecting chamber. The control system opens the isolation valve of the next-level dust collecting chamber or the isolation valve of the exhaust duct, and the smoke enters the next dust collecting chamber for dust collection or enters the exhaust duct for discharge.

[0021] Furthermore, the dust collecting plate is provided with a plurality of through holes for the passage of smoke, and the surface of each dust collecting plate is provided with an insulating material coating applied at intervals.

[0022] Furthermore, the number of dust collection chambers is not less than one.

[0023] Furthermore, a pressure sensor, a thickness tester, and a particle concentration sensor are provided in the dust collecting chamber.

[0024] Furthermore, the control system receives the output signal of the particle concentration sensor in the dust collecting chamber, and controls the reversal instruction of the power polarity of the dust collecting plate and the discharge electrode based on the comparison between the particle concentration signal and the particle concentration threshold; the control system receives the accumulated particle thickness and particle concentration decrease rate signal of the dust collecting plate, and issues an instruction to vibrate the dust collecting plate; the control system receives the preset chamber pressure signal, and issues an isolation valve opening and closing instruction.

[0025] In summary, the invention has the following beneficial effects:

[0026] The present invention adopts an electrostatic dust removal method with discharge bipolar control, which solves the problems of high voltage level applied by traditional electrostatic dust removal methods and large floor space occupied by multi-stage dust removal chambers. The equivalent internal electric field formed after the smoke dust is charged and adsorbed on the two poles is superimposed on the external electric field formed between the discharge electrode and the dust collecting plate, thereby increasing the smoke charging rate and the movement speed of the charged particles. Within a certain power supply voltage level and dust removal space, the dust removal time is greatly reduced, the concentration of exhaust gas particles is reduced, and the method of enhancing the field strength by superimposing the adsorbed smoke dust and the external electric field is greatly improved, and the dust removal efficiency is significantly shortened. By reasonably reducing the number of vibrations on the dust collecting plate, the service life of the dust collecting plate is increased. The present invention can greatly improve the dust removal efficiency, has a low cost, is easy to use, has a better dust removal effect, and is more likely to meet the requirements of modern electrical equipment companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the present invention;

[0028] Figure 2 A schematic structural diagram of the device used in the present invention;

[0029] Figure 3 The dust removal rate per unit time in the dust removal chamber;

[0030] Figure 4 This is a comparison chart of the dust removal rate per unit time under the conditions of electrode polarity reversal (i.e., polarity switching) and electrode polarity non-reversal (i.e., unipolarity) of the present invention.

[0031] In the figure: 1-presetting chamber, 2-dust collecting chamber, 3-smoke conveying pipe, 4-smoke exhaust pipe, 5-metal dust collecting plate, 6-discharge electrode, 7-isolating valve, 8-pressure sensor, 9-insulating material. DETAILED DESCRIPTION

[0032] The present invention will be described in further detail below with reference to the accompanying drawings.

[0033] It should be noted that, for the sake of convenience, the directions described below are consistent with the directions of the drawings themselves, but do not limit the structure of the present invention.

[0034] like Figures 1-2 As shown, the present invention discloses an electrostatic dust removal method using discharge bipolar control, wherein a plurality of dust collecting chambers are added to the flue gas emission duct, and the discharge electrodes and dust collecting plates in the dust collecting chambers are used to adjust the vibration cycle and intensity of the dust collecting plates according to a set threshold value to improve the dust removal efficiency of flue gas emission. Specifically, the method includes the following steps:

[0035] Step 1. Several particle concentration sensors are installed in the dust collecting chamber, and a reversal threshold for electrode reversal, an emission threshold for flue gas emission, and a particle concentration decrease rate threshold of the particle concentration in the dust collecting chamber are set in the control system.

[0036] Step 2. The power supply polarity of the dust collection plate and the discharge electrode in the dust collection chamber is reversed, and after the power supply is turned on, the flue dust is fully charged and adsorbed on the dust collection plate, and the thickness tester installed on the dust collection plate detects the cumulative thickness; under the initial power supply polarity of the dust collection plate and the discharge electrode, the flue dust is charged under the action of the external electric field formed by the dust collection plate and the discharge electrode, and is adsorbed on the dust collection plate.

[0037] Step 3. When the particulate matter concentration sensor detects that the particulate matter concentration in the dust collection chamber reaches the concentration threshold, the control system sends a signal, the power supply polarity of the dust collection plate and the discharge electrode is reversed, the equivalent internal electric field formed by the adsorbed flue dust is superimposed on the external electric field formed by the discharge electrode and the dust collection plate, forming a comprehensive superimposed electric field, which speeds up the movement speed of the particulate matter in the flue gas in the dust collection chamber.

[0038] Step 4. After reversing the power supply polarity, when the thickness tester detects that the cumulative thickness of the dust collection plate reaches the thickness threshold, and the particulate matter concentration sensor measures that the particulate matter concentration change rate is lower than the particulate matter concentration drop rate threshold, the control system sends a command to shake the dust collection plate to remove the particulate matter adsorbed on the dust collection plate, so that the dust deposited on the dust collection plate is shaken off and aggregated into larger particles with larger radius and mass and more easily settled, which enters the ash hopper and is discharged through the ash discharge device, recovers useful materials, and the purified gas is discharged into the atmosphere; the control system controls the shaking period and intensity by receiving the cumulative particulate matter thickness of the dust collection plate.

[0039] Step 5. The control system receives the signals of the particulate matter concentration in the dust collection chamber and the particulate matter thickness on the dust collection plate, and when the flue dust concentration does not reach the current dust collection chamber emission concentration threshold, steps 3 and 4 are repeated until the particulate matter concentration of the flue gas in the dust collection chamber meets the current dust collection chamber emission concentration threshold, the control system opens the isolation valve of the next dust collection chamber or the isolation valve of the exhaust gas pipeline, and the flue gas enters the next dust collection chamber for dust collection or the exhaust gas pipeline for emission.

[0040] The dust collection plate is provided with a plurality of through holes for flue gas to pass through, and each dust collection plate surface is provided with an insulating material coating coated at intervals, which can be polyethylene terephthalate PET, polypropylene PP, and polyethylene naphthalate PEN, or other insulating materials as the insulating material coating. The number of dust collection chambers is not less than 1, and when the number of dust collection chambers exceeds 1, the plurality of dust collection chambers are connected in turn to perform multiple static dust removal on the flue gas. A pressure sensor, a thickness tester, and a particulate matter concentration sensor are arranged in the dust collection chamber.

[0041] In the implementation of the present application, the initial polarity of the dust collection plate can be positive and the initial polarity of the discharge electrode can be negative, that is, "negative inside and positive outside", the flue dust is fully charged and adsorbed on the dust collection plate with an insulating material coating, wherein the material and thickness of the insulating coating can be adjusted according to different use occasions.

[0042] The control system monitors the concentration of particulate matter in the dust collection chamber and sets a particulate matter concentration threshold, and the dust collection plate is equipped with a thickness tester to detect the thickness of the adsorbed particulate matter. Both the particulate matter concentration threshold and the adsorbed particulate matter thickness threshold can be set by the user according to actual use.

[0043] The control system receives the output signal of the particulate matter concentration sensor in the dust collection chamber, compares the particulate matter concentration signal with the particulate matter concentration threshold, and controls the reversal of the power polarity of the dust collection plate and the discharge electrode. The control system receives the accumulated particulate matter thickness and the particulate matter concentration decrease rate signal, and issues a command to shake the dust collection plate. The control system receives the pre-chamber pressure signal and issues an open / close command for the isolation valve.

[0044] When the pressure reaches the threshold, the control system sends a signal to automatically open the valve, and the smoke dust enters the dust collection chamber. When the pressure is detected to be lower than the threshold, the control system sends a signal to automatically close the valve, and the smoke dust continues to be stored in the pre-chamber, and electrostatic dust collection begins in the dust collection chamber. When the concentration in the dust collection chamber reaches the threshold, the control system sends a signal to reverse the power polarity, becoming "positive inside and negative outside". At this time, the equivalent internal electric field formed by the smoke dust adsorbed on the surface of the dust collection plate and the external electric field formed by the discharge electrode and the dust collection plate are superimposed, producing a comprehensive strong electric field acting on the charged smoke dust, accelerating the movement speed of the space dust. When the particulate matter thickness of the dust collection plate reaches the threshold, and the particulate matter concentration sensor measures that the particulate matter concentration change rate is lower than the concentration decrease rate threshold, the dust collection plate is shaken to remove the particulate matter adsorbed on the dust collection plate, causing the dust deposited on the dust collection plate to vibrate and fall, and the dust is aggregated into particles with larger radius and mass and more easily settled, entering the dust hopper and being discharged through the dust discharge device. The recovered useful materials are discharged into the atmosphere, and the purified gas is discharged into the atmosphere. Repeat the polarity reversal and dust collection plate shaking operations until the smoke dust concentration in the dust collection chamber is reduced to below the current chamber's preset concentration threshold. When the smoke dust concentration in the dust collection chamber connected to the smoke exhaust pipe is reduced to below the discharge concentration threshold, the smoke can be safely discharged.

[0045] Dual-polarity power control: In the initial state where the discharge electrode is positive and the dust collection plate is negative, when the dust collection plate adsorbs smoke dust to reach the smoke dust charging threshold, the polarity of the discharge electrode and the dust collection plate is reversed, the internal and external electric fields are superimposed to enhance the dust removal effect, and the effect lasts for a period of time until the next concentration threshold. The electrodes are again exchanged, and the cycle is repeated to achieve high-efficiency dust removal.

[0046] Shaking cycle and intensity: The shaking cycle and intensity are controlled to reduce the number of shaking times and improve the service life of the dust collection plate, while the time of the discharge electrode and the dust collection plate is coordinated, and the dust accumulation degree and the particulate matter concentration change rate are determined to meet the requirements.

[0047] In the present application, the synthetic electric field is composed of the external electric field between the discharge electrode and the dust collecting plate, the electric field of the dust collecting plate attached particles, and the dielectric polarization field of the insulating material. The specific calculation method is as follows:

[0048] The relationship between the electric field intensity E1 between the discharge electrode and the dust collecting plate and the voltage is:

[0049]

[0050] Wherein, U is the potential difference between the discharge electrode and the dust collecting plate, r a is the radius of the discharge electrode, r b is the distance between the dust collecting plate and the center of the discharge electrode, e r is the unit vector of the electric field intensity.

[0051] An electrostatic precipitation method using discharge bipolar control, the synthetic electric field is

[0052]

[0053] The first term of the molecule on the right side of formula (2) is the synthetic electric field generated by the free charge, and the second term is the dielectric polarization field generated by the insulating material. Among them, k1 is the ionization coefficient; k2 is the smoke charging coefficient, which reflects the proportion of charged smoke particles to the total particle number; k3 is the dust collecting plate adsorption rate, which refers to the proportion of adsorbed particle number to charged particle number; k4 is the correction coefficient of the number of charges distributed in space, the value range is 0.9-1.3; ρ(x) is the surface charge density.

[0054] Figure 3 The dust removal rate of the "negative rod positive plate", "positive rod negative plate" and "reversing electrode" in the unit time in the primary dust collecting chamber is shown. The unit time dust removal rate of "negative rod positive plate" and "positive rod negative plate" is significantly lower than that of the present application, i.e. "reversing electrode", and the unit time dust removal rate of "negative rod positive plate" is higher than that of "positive rod negative plate". Figure 4 The unit time dust removal rate of the "reversing polarity" and "single polarity" dust removal in the primary dust collecting chamber is shown. The unit time dust removal rate of the "reversing polarity" is higher than that of the "single polarity".

[0055] The electrostatic precipitation method using discharge bipolar control solves the problems of high voltage level applied by traditional electrostatic precipitation method and large floor area of multi-stage dust collecting chamber. The method ingeniously uses the superposition of the adsorbed smoke and the applied electric field to enhance the field strength, greatly improves the dust removal efficiency, significantly shortens the dust removal time, and prolongs the service life of the dust collecting plate by reasonably reducing the number of vibration times.

[0056] The electrostatic precipitation method using discharge bipolar control is designed ingeniously and has strong reliability. Moreover, it can greatly improve the dust removal efficiency, has low cost, is easy to use, has better dust removal effect, and is more suitable for modern electrical equipment enterprises.

[0057] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An electrostatic dust removal method using bipolar discharge control, characterized in that: Add several dust collection chambers to the flue gas emission duct, use the discharge electrodes and dust collecting plates in the dust collection chambers, adjust the vibration cycle and intensity of the dust collecting plates according to the set threshold, and improve the dust removal efficiency of flue gas emission. The specific steps include: Step 1. Install several particle concentration sensors in the dust collecting chamber, and set a reversal threshold for electrode reversal, an emission threshold for flue gas emission, and a particle concentration decrease rate threshold for the particle concentration in the dust collecting chamber in the control system; Step 2. The power polarity of the dust collecting plate and discharge electrode in the dust collecting chamber is opposite. After the power is turned on, the smoke is fully charged and adsorbed on the dust collecting plate. A thickness tester is installed on the dust collecting plate to measure the dust accumulation thickness. Under the initial power polarity of the dust collecting plate and discharge electrode, the particles in the smoke are charged by the external electric field formed by the dust collecting plate and discharge electrode, and adsorbed on the dust collecting plate. Step 3. When the particle concentration sensor detects that the particle concentration in the dust collecting chamber has reached a concentration threshold, the control system sends a signal, and the polarity of the dust collecting plate and the discharge electrode power supply is reversed. The equivalent internal electric field formed by the smoke particles adsorbed on the dust collecting plate is superimposed with the external electric field formed by the discharge electrode and the dust collecting plate, forming a comprehensive superimposed electric field, which accelerates the movement of particles in the smoke in the dust collecting chamber. Step 4. After reversing the polarity of the power supply, when the thickness tester detects that the accumulated particle thickness of the dust collecting plate reaches the thickness threshold, and the particle concentration sensor measures that the particle concentration change rate is lower than the particle concentration decrease rate threshold, the control system issues a command to vibrate the dust collecting plate to remove the particles adsorbed on the dust collecting plate, so that the dust deposited on the dust collecting plate is shaken off and enters the dust collecting hopper and is discharged through the dust discharge device to recover useful materials, and the purified gas is discharged into the atmosphere; the control system controls the vibration cycle and intensity by receiving the accumulated particle thickness of the dust collecting plate; Step 5. The control system receives the signal of the particle concentration in the dust collecting chamber and the signal of the particle thickness on the dust collecting plate. When the smoke concentration does not reach the emission concentration threshold of the current dust collecting chamber, steps 3 and 4 are repeated until the particle concentration of the smoke in the dust collecting chamber is lower than the emission concentration threshold of the current dust collecting chamber. The control system opens the isolation valve of the next-level dust collecting chamber or the isolation valve of the exhaust duct, and the smoke enters the next dust collecting chamber for dust collection or enters the exhaust duct for discharge.

2. The electrostatic dust removal method using bipolar discharge control according to claim 1, characterized in that: The dust collecting plate is provided with a plurality of through holes for smoke to pass through, and the surface of each dust collecting plate is provided with an insulating material coating which is coated at intervals.

3. The electrostatic dust removal method using bipolar discharge control according to claim 1, characterized in that: The number of the dust collecting chambers is no less than one.

4. The electrostatic dust removal method using bipolar discharge control according to claim 1, characterized in that: A pressure sensor, a thickness tester, and a particle concentration sensor are arranged in the dust collecting chamber.

5. The electrostatic dust removal method using bipolar discharge control according to claim 1, characterized in that: The control system receives an output signal of a particle concentration sensor in the dust collecting chamber, and controls the reversal of the power polarity of the dust collecting plate and the discharge electrode based on a comparison between the particle concentration signal and a particle concentration threshold value; the control system receives signals of the accumulated particle thickness and the particle concentration decreasing rate of the dust collecting plate, and issues an instruction to vibrate the dust collecting plate; the control system receives a preset chamber pressure signal, and issues an opening and closing instruction for the isolation valve.

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