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Q&A on Flue Gas Electrostatic Precipitator Technology 1. Briefly describe the production process in thermal power plants. Answer: In a boiler, the chemical energy of fuel is converted into thermal energy through high-temperature combustion, which in turn heats water to superheated steam. This steam is then used to drive a turbine, converting the thermal energy of the steam into mechanical energy that drives the rotor’s rotation; finally, a generator converts this mechanical energy into electrical energy. 2. What components does the circuit consist of? Answer: A circuit is the path through which electric current flows; it consists of four main components: a power source, a load, control devices, and wires. 3. Briefly describe the flue gas flow? Answer: The flue gas at the furnace exit first flows through the heating surfaces of the horizontal and vertical flues, then passes through a dust collector to remove fly ash, and finally is drawn by an exhaust fan into the chimney and discharged into the atmosphere. 4. What is resistance? What factors affect the resistance of a conductor? Answer: When electric current flows through a conductor, the charges in motion collide with each other continuously, and they also constantly collide with the atoms or molecules that make up the conductor. As a result, the conductor exerts a certain resistance to the current passing through it; this phenomenon is known as the resistance of the conductor. 5. What are the main factors affecting convective heat transfer? Answer: The main factors affecting convective heat transfer include the cause of fluid flow, the state of fluid flow, geometric factors, the physical properties of the fluid, and whether there are any phase changes in the fluid. 6. What is corona discharge? Answer: Corona discharge occurs when the voltage between the electrodes rises to a certain critical value, causing the high electric field strength at the corona electrode to locally break down the gas in its vicinity. And a pale blue glow appears around the corona electrode, accompanied by a faint humming sound. 7. What is spark discharge? Answer: After corona discharge occurs, if the voltage between the electrodes is increased further, at a certain value, intermittent, instantaneous spark discharges and crackling sounds occur across the entire gap between the electrodes. 8. What is arc discharge? Answer: After a spark discharge occurs, continuing to increase the voltage between the electrodes causes the gas to break down intermittently, resulting in a continuous discharge that emits intense light and a loud popping sound. This is accompanied by high temperature and intense light that penetrates the entire gap between the cathode and the anode; this phenomenon is called arc discharge. 9. What are secondary devices? Answer: The measuring instruments, monitoring devices, signaling devices, control devices, interlocking devices, relay protection devices, and automatic devices in the secondary circuit are collectively referred to as secondary equipment. 10. What is a secondary circuit? Answer: A secondary circuit is a circuit that is used for measuring, monitoring, operating, and protecting the primary circuit and its equipment. 11. What is a chain? Answer: A interlock is a general term for devices or systems in which equipment operates in sequence according to certain conditions, turning on or off one after another. 12. What factors are related to the charge of dust? Answer: In the electric field of an electrostatic precipitator, the charge amount of the dust is related to the particle size of the dust, the intensity of the electric field, and the time of residence. 13. What are the main components inside the high-voltage control cabinet? Answer: The components inside the high-voltage control cabinet mainly include: low-voltage operating components, voltage-regulating thyristors, primary sampling elements, voltage automatic regulators, and capacity protection components. 14. Why should the anode rapping time be shorter than that of the cathode? Answer: There are two reasons why the anode requires a shorter shaking time than the cathode. First, the anode collects dust more quickly, resulting in more ash accumulation compared to the cathode. Second, the dust suppression effect on the cathode is poor, making it easier for dust to become airborne again during shaking. 15. What are the main equipment or systems that make up the electrostatic precipitator unit system? Answer: The main components of the electrostatic precipitator system include: the dust collection electrode system (anode), the corona electrode system (cathode), the smoke box system, the air flow distribution device, the piping system, the housing, the ash storage and discharge system, the trough plate device, and auxiliary facilities. 16. Briefly describe the advantages and disadvantages of electrostatic precipitators. Answer: Advantages: 1. High dust removal efficiency. 2. Low resistance. 3. Low energy consumption. 4. Large amount of flue gas to be treated. 5. High-temperature resistance. Disadvantages: 1. High consumption of steel, high initial investment. 2. Large floor area. 3. High requirements are placed on manufacturing, installation, and operation. 4. Sensitive to the characteristics of flue gas. 17. What are the characteristics of high-voltage silicon rectifier transformers? Answer: 1. Output a negative DC high voltage. 2. The output voltage is high and the output current is low, yet the output voltage needs to change in order to track the continuously varying electric field breakdown voltage. 3. The loop impedance is relatively high. 4. The temperature rise is relatively low. 18. Why can’t the vibration cycle of the plates be too long or too short? Answer: If the vibration cycle is short and the frequency is high, it is easy for dust to become airborne again; if the vibration cycle is too long, a large amount of dust has accumulated on the plates and pole wires, which can lead to reverse corona. 19. Briefly describe the working principle of an electrostatic precipitator. Answer: A electrostatic precipitator uses a direct current voltage to generate corona discharge, which ionizes the gas. As the gas passes through the electrostatic precipitator, the dust particles in it become charged in the electric field. Under the influence of the electric force, these charged dust particles move toward the electrodes of opposite polarity. When they reach the plates or electrodes, the dust is adsorbed onto them and then falls into the ash hopper via a shaking mechanism, thereby purifying the gas. 20. Briefly describe the dust charging process. Answer: Applying a sufficiently high branch voltage between the cathode and anode of the electrostatic precipitator creates a highly uniform electric field between the two poles. The electric field strength is highest near the cathode, where corona discharge occurs, causing the surrounding gas to ionize. Gas ionization produces a large number of electrons and positive ions, which move toward the opposite poles under the force of an electric field. When dust-laden air passes through an electric field, negative ions and positive ions collide with each other and adhere to the dust, thereby charging the neutral dust particles and achieving dust charging. 21. What devices are generally included in a low-voltage control cabinet? Answer: A low-voltage control cabinet system generally includes: a cathode, an anode program control device, an ash hopper level monitoring device, an automatic temperature control device for insulator heating, a safety interlock control device, a high-voltage safety grounding switch control device, a low-temperature monitoring, display, and alarm device for the insulator chamber, temperature detection devices for the inlet and outlet flue chambers, and a comprehensive alarm device. 22. What is the function of the high-voltage control device in an electrostatic precipitator? Answer: The main function of the high-voltage control device for electrostatic precipitators is to adjust the maximum voltage supplied to the precipitator as needed, depending on the properties of the dust in the gas being treated, so as to maintain an average voltage at a level where spark discharge is likely to occur. 23. How do charged dust particles move in an electric field? Answer ； Charged dust located between the collector electrode and the corona is subject to four forces, and its motion is governed by Newton’s laws. These four forces are: the gravity of the dust particles, the electrostatic force exerted on charged dust particles by an electric field, inertia, and the resistive force that opposes the movement of the dust particles. Gravity can be ignored when charged dust particles move toward the collection electrode under the influence of the electric field force. The electric field force and the medium resistance quickly reach equilibrium, causing the dust collection electrode to move at a constant speed; at this point, the inertial force can be neglected. 24. What are the functions of the green indicator light? Answer: 1. Indicate the operating and stopped status of electrical equipment. 2. Check whether the power supply of the monitoring and control circuit is normal. Use traffic lights to monitor whether the tripping circuit is functioning properly, and use traffic lights to monitor whether the closing circuit is functioning properly. 25. Why cannot the electric precipitator have its electric field activated during the oil mixing combustion phase at the beginning of boiler startup? This is because, during the initial startup phase of the boiler when oil is used in combination with fuel, the flue gas contains a large amount of sticky particles. If an electric field is applied at this time, these particles will adhere heavily to the electrodes and pole wires, making it difficult to remove them through shaking; moreover, they have a corrosive effect. 26. What are the components of the anode system? What is its function? Answer: The anode system consists of three parts: the anode plate array, the suspension mechanism for the plates, and the plate rapping device. Its function is to capture charged dust; under the action of vibration, the dust adhering to the surface of the anode plate breaks off in chunks and falls into the ash hopper, thereby achieving dust removal. 27. What are the components of the cathode system? What is its function? Answer: The cathode system consists of a corona wire, a corona frame, frame suspension rods and support sleeves, as well as a cathode rapping device. Its function is to generate corona discharge in an electric field to ionize the gas. 28. What is the function of the cathode small frame? Answer: 1. Fixed corona wire. 2. Corona discharge occurs. 3. Vibrate the corona electrode to remove dust. 29. What are the common electronic components used in the power supply devices of electrostatic precipitators? Answer: Diodes, bipolar transistors, unijunction transistors, junction field-effect transistors, thyristors, operational amplifiers, etc. 30. What conditions should a reasonable dust collection electrode plate have? Answer: 1) It has good electrical properties, with a uniform distribution of electric field strength and current density on the plate surface, as well as a high spark voltage. 2) It has excellent dust collection performance, enabling effective prevention of secondary dust dispersion. 3. It has good shaking performance, with a distinct bluish-gray effect. 4. It has high mechanical strength, good stiffness, and no deformation. 5. It is easy to manufacture, requires little metal, and no welds are allowed on each plate. 33. What are the factors that affect the dust driving speed, and what is their respective impact? Answer: 1. Dust particle size. As the particle size decreases, the dust driving velocity value decreases accordingly. 2. Number of electric fields. When the number of electric fields increases, the average dust drift velocity value is smaller. 3. Electrical power input of the electrode system. A reasonable power supply system can achieve a higher dust expulsion speed. 4. Plate spacing. As the plate spacing increases, the drift velocity also increases significantly. 5. Size of the dust collection area. When the dust collection area increases, the dust drift velocity decreases. 6. The specific resistance of dust is low. As the resistance increases, the dust propulsion speed will decrease significantly. 34. What are the steps for conducting experiments on the cold-state volt-ampere characteristics of electrostatic precipitators? Answer: Close the high-voltage isolating switch under the side electric field, activate the electric field, and set the operation selector switch to the “manual” position so that the current and voltage can rise slowly ； Whenever the secondary voltage increases by 5 KV, record the corresponding values of the secondary current, primary voltage, and primary current ； Once the secondary electric field starts to flash over or when the current and voltage reach their maximum rated values, manually reduce the voltage slowly and record the value of the secondary breakdown voltage. 35. What is the impact of the spacing between corona wires on the operation of an electrostatic precipitator? Answer: The distance between the corona wires has a certain impact on the magnitude of the current. When the spacing between the wires is too close, the corona wires cause a decrease in the current per unit length of the conductor due to electrical shielding, and this value can even drop to zero. However, the spacing between the corona wires should not be too large either; too large a spacing results in too few corona sites inside the electrostatic precipitator, which lowers the current density in that area and thus affects the dust removal efficiency. Therefore, the distance between the corona wires should be appropriate; the optimal wire spacing is generally 0.6 to 0.65 times the channel width. 36. What is the impact of the specific resistivity of dust on the performance of electrostatic precipitators? Answer: In plate electrostatic precipitators, dust with a high specific resistivity limits the corona current, which in turn affects the charge amount, charge density, and electric field strength of the dust particles. This leads to a reduced dust removal efficiency. Additionally, dust with high specific resistivity has greater adhesion properties; therefore, more force is required to remove the dust from the plates, resulting in increased secondary dust suspension and again leading to a lower dust removal efficiency. Dust with a low specific resistivity tends to acquire a positive charge due to electrostatic induction, causing the dust deposited on the plates to be repelled back into the electric field space; whereas dust with a high specific resistivity is prone to generating reverse corona, both of which hinder the improvement of dust removal efficiency. Therefore, medium-specific resistance dust is more suitable for electrostatic precipitators. 37. What is the intermittent power supply control method? Answer: It achieves intermittent changes in the high-voltage direct current output through the operation of the control system; in other words, the voltage between the electrodes within the electric field is intermittent, similar to a pulse pattern. 38. What is the pulsed power supply control method? Answer: Through effective control of the voltage setting stage, the high-voltage waveform output undergoes intermittent changes, thereby overcoming back corona. 39. What is the spark integral value control method? Answer: The spark voltage control method achieves an optimal output voltage by controlling the voltage at which a certain amount of spark discharge occurs. 40. What is the automatic spark frequency tracking control method? Answer: The automatic tracking control method for spark frequency involves setting a maximum spark discharge frequency; that is, the voltage output is adjusted based on the measured spark discharge frequency to achieve the optimal condition. 41. What does the measurement of flue gas flow rate and related parameters include? Answer: The measurement parameters include flue gas temperature, pressure, humidity, velocity, and flow rate; additionally, the flue gas density must be calculated based on the composition of the flue gas or empirical formulas. 42. Briefly describe the sequence for cold-state commissioning of an electrostatic precipitator. Answer: The sequence for cold-state commissioning is to first activate the low-pressure control devices such as heating, shaking, ash discharge, ash transport, and temperature monitoring. Once all these devices are operating properly, the high-voltage silicon rectifier equipment is turned on, and voltage elevation testing is carried out field by field. 43. What are the components of the automatic control system for a high-voltage rectifier circuit? Answer: 1. Power supply section. Low-voltage power supply required for the supply control circuit. 2. Given part. The artificially specified degree of adjustment, that is, the given adjustment value. 3. Feedback measurement section. The actual values such as current and voltage taken from the output terminal. This value is then sent to the control device for comparison and integration with the set value. 44. What are the characteristics included in the physicochemical testing of dust? Answer: The determination of the physicochemical properties of dust includes the analysis of the chemical composition of the dust, the measurement of its true density, the determination of its particle size distribution, and the measurement of its specific electrical resistance. 45. What does the grayish-blue color inside the electric field during major repairs include? Answer: 1. Before cleaning the dust, check the accumulation of dust on the plates, pole wires, trough plates, air distribution plates, and the inner walls of the dust hoppers, take notes, identify the causes, so as to address the issues in a targeted manner. 2. Before cleaning the dust, check the plate spacing and record any deviations of the plates and pole wires. 3. Flush all components inside the electric field with fire-fighting water. Proceed in the order from the inlet to the outlet, and from the top to the bottom of the ash hopper. 4. After the dust cleaning is completed, hot air drying can be used. 46. What is an air flow bypass? What impacts does it have on the operation of electrostatic precipitators? Answer: Air flow bypass refers to the situation in which the air flow within the electrostatic precipitator does not pass through the dust collection area, but instead flows through the channels formed at the top and bottom of the dust collection plates, as well as on the outermost sides of these plates, in connection with the inner wall of the housing. The air flow bypass allows a portion of the flue gas containing dust to be released into the atmosphere without being treated, which in turn leads to secondary dust dispersion and reduces the dust removal efficiency. 47. What are the effects of uneven expansion at the cathode and anode on the operation of a dust collector? Answer: When the expansion is uneven, the pole lines and pole plates bend and deform, resulting in a reduction in the local inter-pole distance ； The discharge distance between the poles decreases. The secondary voltage does not rise sufficiently or trips after rising, affecting dust removal efficiency. 48. What standards should be met after the maintenance of electrostatic dust removal equipment? Answer: 1. The quality of the maintenance work meets the specified quality standards. 2. Eliminate equipment defects. 3. The no-load voltage rise is within the acceptable range, meeting the specified values. 4. Eliminate leakage; 5. The safety protection devices and main automatic clamping functions are reliable, and the main instruments, signals, and indicators are accurate. 6. The insulation layer is intact, and the equipment area is clean. The maintenance technical records are accurate and complete. 49. What are the contents of the three principles of not letting accidents go unaddressed? Answer: The cause of the accident must be clarified; those responsible for the accident and the general public must be educated; and no preventive measures must remain in place. 50. What are the typical components of a pneumatic ash conveying system? Answer: The pneumatic ash conveying system consists of a feeding device, conveying pipes, an air power source, an air-powder separation device, an ash storage tank, and an automatic control system. 51. Briefly describe the contents and requirements for inspecting the electrostatic precipitator itself during operation. Answer: 1. All access doors are tightly sealed. 2. The housing should have no significant air leakage (no noise when under negative pressure). 3. Corridors, guardrails, and ladders should be intact, free of rust, and clean. 52. Briefly describe the contents and requirements for inspecting the high-voltage control cabinet during operation. Answer: 1. The readings displayed on the meter are consistent with those on the host computer, and all indicators are in good condition. 2. The thyristor temperature is normal and the cooling fan is operating properly. 3. There is no overheating in the main circuit. 4. The spark rate should be kept within the specified range. 53. Briefly describe the inspections and requirements for low-voltage cabinets during operation. Answer: 1. All temperature gauges and indicator lights are in good condition. 2. There are no deviations or errors in vibration control. 3. The automatic control of electric heating meets the requirements. 4. The terminal strips inside the cabinet are not loose, the fuses are in good condition, and there are no abnormalities with the thermocouple relay or the air switch. Clean all devices. 54. Briefly describe the characteristics and requirements for the temporary shutdown of electrostatic precipitators. Answer: When the boiler is shut down for a short period of time and there is no maintenance work required for the electrostatic precipitator, a temporary shutdown method can be employed, putting the electrostatic precipitator in a standby state. The operational requirements are as follows: first, reduce the output current and voltage to their minimum levels, then stop supplying power to the electrodes in each electric field in sequence, while keeping the rapping devices and heating system operational. 55. Describe the aspects of monitoring and maintenance during the operation of an electrostatic precipitator. Answer: 1. Monitor and maintain the voltage and current of the dust collector, as well as the temperature of each heating point, within normal ranges. 2. Adjust the spark frequency in a timely manner to meet the requirements. 3. Check that the temperature, oil pressure, and oil level inside the tank of the high-voltage silicon rectifier transformer should all be within the specified limits. 4. There is no abnormal discharge in the high-voltage output network. 5. Regularly check whether the rapping system and its drive devices, as well as various heating systems and ash discharge systems, are operating properly, to ensure smooth ash falling and efficient ash discharge. 6. All door openings of the dust collector are well sealed, with an air leakage rate of no more than 5%. 7. Monitor whether the smoke temperature and pressure at the inlet and outlet of the dust collector are normal; if there are abnormalities, the causes should be analyzed and appropriate actions taken. 56. Briefly describe the safety measures for the maintenance of rotating machinery. Answer: 1. A work order must be issued before maintenance; the person in charge of the work and the person granting permission must be clearly identified and qualified. 2. Before maintenance, the rotating machinery should be stopped, and the power supply should be cut off. A sign reading “Do not close – people are working” should be attached to the control handle. 3. All power or pressure sources connected to it must be cut off. 57. What are the common faults of electric motors? Answer: 1. The insulation resistance of the motor decreases. 2. The motor has difficulty starting or cannot start at all. 3. Overheating of the motor bearings. 4. Abnormal noise is heard when the motor is running. 58. What are the symptoms of poor connection or melting of the thyristor fuse? Answer: The alarm bell sounds, the trip indicator light is on, the power supply voltage is normal and the switches inside the cabinet are in proper position; however, after restarting, neither the primary nor the secondary meters give any indication. 59. What are the fault symptoms when the thyristors or other protective components of a high-voltage silicon rectifier transformer fail? Answer: When the alarm sounds and the trip indicator light comes on, upon restart, the primary and secondary voltages and currents rise rapidly and exceed normal levels, resulting in a flashover trip. When the rectifying step-up transformer is restarted, there is significant noise along with vibration during operation. 60. Why is it necessary to use a level gauge to monitor the amount of ash stored in the ash hopper? Answer: Excessive dust accumulation in the ash hopper can affect the proper operation of the electrostatic precipitator; in severe cases, it can cause a short circuit and lead to the shutdown of the electric field. Conversely, if too little dust accumulates in the ash hopper, it will result in significant air leakage, causing the dust to become airborne again and greatly reducing the dust removal efficiency. The ash inside the ash hopper cannot be observed directly due to being sealed by the casing; it can only be monitored using a level gauge. 61. What are the common faults of the vibration system? Answer: 1. Falling hammer, 2. Wear of the shaft and bearings. 3. Fuse and pin broken. 4. The punching force decreases. 5. The shaking motor has burned out. 62. What are the reasons for the breakage of the corona electrode wire? Answer: 1. Local stress concentration. 2. The installation quality is poor. 3. Discharge arcing. 4. Gas corrosion. 5. Fatigue fracture. 63. What is the function of the fuse in the shaking device? What are the general requirements? Answer: The function of the fuse in the shaking device is to ensure the safety of the shaking mechanism; once the fuse breaks, the motor and gearbox will operate under no-load conditions. The breaking torque of the fuse element is required to be lower than the maximum allowable output torque of the reducer; in the event of a failure, the fuse element breaks first. 64. What measures can be taken to control the impact of dust specific resistance on the performance of electrostatic precipitators? Answer: Quenching and tempering treatments are employed, such as adding conductive substances like SO3 and NH3 to the chimney; high-temperature electrostatic precipitators operating at temperatures above 300 degrees Celsius are used to reduce the specific resistance of the dust; wash-type electrodes or wide spacing are utilized, and the high-voltage power supply system operates in a pulsed mode. 65. What measures are mainly taken, based on the influence of flue gas properties, to improve the performance and dust removal efficiency of electrostatic precipitators? Answer: Reduce the wind speed in the electric field and keep it within a reasonable range to prevent secondary suspension of dust. Use corona wires with sharp tips to improve the charging of dust particles in high-concentration flue gas, thereby preventing back-corona and corona closure. This also helps to improve the composition of the flue gas and enables conditioning processes that facilitate the charging of dust particles. 66. How should frequent breakage of the rapping fuse be addressed? Answer: The corona electrode and the dust-collecting electrode, especially the shaking devices of the latter, often experience frequent failure of their fuses (pins) during operation due to inadequate consideration of the axial expansion of the bearing support structures; the relative expansion between these components and the reducer is not taken into account either. Solutions can be adopted such as using properly structured heavy-duty bearing supports, and selecting universal couplings to connect with the reducer. 67. What are the common reasons why fuses get cut? Answer: 1. The vibration shaft is not installed concentrically. 2. After operating for a period of time, the wear of the bearing wear sleeves becomes severe, resulting in misalignment of the shaking boat. 3. The rapping hammer head is stuck. 4. The fusible link is installed incorrectly. 5. Long shutdown time; the rotating part of the hammer gets stuck. 68. What could be the reasons for a too frequent electric field flashover, leading to a decrease in dust collection efficiency? Answer: 1. There are discharge points outside the electric field, such as at the high-voltage cables of the isolating switch and the damping resistors. 2. The spark rate of the control cabinet has not been adjusted properly. 3. The rapping time and cycle of the pre-electric field are not appropriate. 4. There are abnormal discharge points within the electric field, such as plate deformation or broken corona wires. 5. Operating conditions change, and flue gas conditions fluctuate greatly. 69. What conditions must be met for the commissioning of an electrostatic precipitator? Answer: 1. The flue gas temperature is below 160 degrees, with a maximum of no more than 200 degrees. 2. The negative pressure of the flue gas is less than or equal to 3920 Pascals. 3. The content of flammable gases in the flue gas must be below the hazardous level; the carbon monoxide content should be less than 1.8%. 4. The flue gas contains no more than 52 g/m3. 5. The specific resistance is less than at 160 degrees. 6. The ground resistance is less than 1 ohm. 7. The high-voltage power supply device should be activated after the boiler stops burning fuel. 70. What are the main contents of the commissioning of the electrostatic precipitator itself? Answer: The commissioning work for the electrostatic precipitator before it is put into operation should be carried out only after the electrical and mechanical equipment have been inspected and found to be in good condition, and after the high- and low-voltage power supply systems have been inspected and tested to meet the requirements for power supply. The following commissioning tasks can then be undertaken: 1. Commissioning of the shaking and ash discharge systems. 2. Overall sealing air leakage rate test. 3. Test on the uniformity of air flow distribution. 4. No-load voltage rise, volt-ampere characteristic testing, and tuning, including adjustments for open circuit, short circuit, and under-voltage protection. 5. Resistance test of the electrostatic precipitator body. 6. Commissioning of the electric heating system. 71. Why do diodes have unidirectional conductivity? What are the forward voltages of silicon diodes and other types of diodes? Answer: The basic structure of a diode is a PN junction. A forward voltage is applied to this PN junction by connecting the positive terminal of the power supply to the P region and the negative terminal to the N region. Since the direction of the applied electric field is opposite to that of the built-in electric field of the PN junction, the junction electric field is significantly weakened, allowing the majority carriers in the two regions to pass through the PN junction easily, resulting in a large current in the circuit and placing the PN junction in a conductive state. Conversely, when a reverse voltage is applied to the PN junction, the direction of the external electric field is the same as that of the junction electric field, thereby greatly strengthening the junction electric field. This makes it more difficult for the majority carriers in the two regions to pass through the PN junction, while facilitating the passage of minority carriers. Due to the very small number of minority carriers, a very low reverse leakage current is generated in the circuit, which is usually negligible. In summary, a forward voltage applied to the PN junction causes it to conduct current, while a reverse voltage causes it to stop conducting; thus, the PN junction endows the diode with unidirectional conductivity. The forward voltage of a silicon diode is 0.7 V, while that of a germanium diode is 0.3 V. 72. Why can a three-phase motor be powered using a three-phase three-wire system? And must the lighting power supply use a three-phase four-wire system? Answer: Since a three-phase motor represents a three-phase symmetric load, whether connected in star or delta configuration, it only requires the three phase wires of the motor to be connected to the three phase wires of the power supply; no fourth neutral wire is needed. Therefore, it can be powered by a three-phase three-wire power supply ； The load of the lighting power supply is the light bulbs, whose rated voltage is the line voltage; one end of each bulb must be connected to a phase wire and the other end to the neutral wire. This ensures that the voltage of each phase is not affected. Therefore, a three-phase four-wire system must be used, and it is strictly prohibited to use a single phase wire along with a ground wire as the lighting power supply. 73. Why must the grounding resistance of the electrostatic precipitator itself not exceed 1Ω? Answer: The outer shell of the electrostatic precipitator, the anode plates, and the positive terminal of the rectifier transformer are all grounded. During a flashover, high-frequency current causes the potential of the electrostatic precipitator’s casing to rise; the greater the grounding resistance, the higher this potential becomes, which can pose a risk to the control circuits and human safety. When the ground resistance is less than 1Ω, the shell potential will be within a safe range. 74. Why is it necessary to install a flow distribution device at the inlet flue box of an electrostatic precipitator? Answer: Typically, gas is introduced into an electrostatic precipitator by flowing from a duct with a small cross-section into a working chamber with a large cross-section. Therefore, without taking necessary measures, this can result in an uneven distribution of gas across the cross-section of the electric field. The non-uniformity of the velocity distribution across the cross-section of an electrostatic precipitator affects its dust removal efficiency; the more non-uniform the velocity distribution, the lower the purification rate. To promote a uniform airflow distribution, it is advisable to install flow guiding plates at the inlet of the intake flue box, and flow distributing plates should also be placed inside the box. 75. What is the impact of flue gas properties on the performance of electrostatic precipitators? Answer: Among the properties of flue gas, temperature, pressure, humidity, flow rate, and dust concentration have a significant impact on the volt-ampere characteristics of electrostatic precipitators, thereby affecting their performance. Flue gas temperature and pressure affect the corona initiation voltage, the electric field strength on the surface of the corona electrode at the moment of corona initiation, the space charge density near the corona electrode, as well as the effective migration rates of molecules and ions. For instance, when the temperature rises and the pressure decreases, the density of flue gas decreases, resulting in a reduction in the corona onset voltage, the surface electric field strength of the corona electrode at onset, and the spark discharge voltage. The composition of flue gas has a significant impact on the volt-ampere characteristics and spark discharge voltage of electrostatic precipitators. The concentrations of different molecular components and the affinity of these components are very important for negative corona discharge. Different flue gas components result in different effective migration rates for charge carriers in corona discharge, and in corona discharge, the effective migration rate of ion charge carriers is the most important parameter for determining electrical conditions. The effect of flue gas humidity on the operation of electrostatic precipitators is twofold. Ordinary flue gas contains a high amount of moisture, resulting in high dust removal efficiency ； However, when the moisture content in the flue gas is too high and the insulation of the electrostatic precipitator is inadequate, the flue gas temperature can reach the dew point, which may cause corrosion of the electrode system and the casing. As the dust concentration in the flue gas increases, the space charge rises, the corona current decreases, and the dust removal efficiency declines; in severe cases, this can lead to corona closure. Increasing the flue gas flow rate can reduce the cost of electrostatic precipitators and decrease their size ； However, excessively high flow velocities cause the charged dust particles to be carried away before they have time to deposit on the collection plates ； At the same time, secondary dispersion is likely to occur. This occurs more easily, especially at the dust collection electrode during vibration. Generally, as the flow velocity of the smoke stream in the electric field increases, the dust removal efficiency decreases. 76. Why should the center line of the hammer be lower than the center of the impact rod when installing the rapping device in a cold state? Answer: To prevent the impact rod from swaying left and right during impact, a guiding device for the impact rod needs to be installed inside the dust collector. Additionally, it must be noted that since the dust collection plates elongate under the effect of hot airflow during the operation of the dust eliminator, when installing it in a cold state, the centerline of the hammerhead should be lower than the centerline of the impact rod. The distance between these two centerlines is determined based on the temperature of the airflow and the temperature of the dust collection plates. 77. Why are heaters installed in the insulating porcelain components of electrostatic precipitators? Answer: To maintain insulation strength, many insulating porcelain components are installed on the body of the electrostatic precipitator. Whether these components are located within the beams or in the shaking system, if the temperature around them is too low, condensation vapor will form on their surfaces, thereby reducing the insulation properties of those porcelain components. When power is supplied to the dust collector, surface discharge can easily occur on the surface of the insulating sleeve porcelain components, preventing the operating voltage from rising and thus causing a fault that renders the electrostatic dust collector inoperable. Furthermore, during start-up and shutdown, the temperature difference inside the smoke box is large; the ceramic components cannot adjust to these temperature changes promptly, which can lead to cracking and damage. This requires heating and insulating the porcelain part. Therefore, a heater must be installed at the insulating part. 78. What are the operating factors that affect the performance of electrostatic precipitators? Answer: (1) Airflow distribution. (2) Air leakage. (3) Secondary suspension of dust. (4) Airflow bypass. (5) Coronal wire hypertrophy. (6) Uneven expansion of the cathode and anode. 79. Why is a negative corona used instead of a positive corona in electric dust collectors for industrial use? Answer: Depending on the polarity of the electrode, corona can be divided into positive corona and negative corona. When the corona electrode is connected to the negative pole of the high-voltage DC power supply, a cathodic corona (that is, negative discharge) is generated. When the corona electrode is connected to the positive pole of the high-voltage DC power supply, a positive corona (that is, positive discharge) is generated. Although both types of corona discharges with different polarities are used in dust removal technologies, with the exception of air purification (air conditioning) systems that use positive corona discharges due to the lower levels of ozone and nitrogen oxides produced by them, almost all industrial electrostatic precipitators, including those used in power plants, rely on negative corona discharges. This is because, under the same conditions, the cathodic corona can achieve a higher current than the anodic corona, and its breakdown voltage is also much higher than that of the anodic corona discharge; in other words, cathodic corona discharge can operate at a higher voltage. 80. Why are thyristor groups connected in anti-parallel in electrostatic precipitators? Answer: The anti-parallel thyristor is a contactless electronic switching device that performs the function of AC voltage regulation for equipment. It determines the degree of conduction angle based on the signals sent by the automatic voltage regulator, so that the voltage output by the thyristor meets the operational requirements. Since alternating current consists of positive and negative half-cycles to form a full wave, connecting two thyristors in anti-parallel configuration ensures that one of them is active during each half-cycle. The rectifying circuit’s step-up transformer receives alternating current signals, which enables a relatively stable direct current output and thus better dust removal effects. 81. Why is a low-pressure control system necessary? Answer: As is well known, the performance of an electrostatic precipitator depends not only on an advanced and reasonably designed precipitator unit as well as a high-voltage power supply system with excellent control characteristics, but also on a complete set of low-voltage control systems that work in close coordination with them; only in this way can the desired dust collection results be achieved. In recent decades, the electrostatic dust removal technology in our country has developed rapidly, and both theory and practice have proven that the low-voltage control system is one of the three essential components of an electrostatic dust removal system. It is a multi-functional automatic control system; the quality of its control capabilities and the completeness of its control functions have a direct impact on increasing the degree of automation in the operation of electrostatic precipitators, improving their operational performance, reducing the workload of maintenance staff, and enhancing the dust removal efficiency of these precipitators. 82. What are the effects of air leakage in an electrostatic precipitator on its operation? Answer: In an electrostatic precipitator operating under negative pressure, if there are leaks at the welds of its casing, external air will leak in, resulting in an increase in the smoke velocity and a decrease in the smoke temperature within the precipitator, which deteriorates its performance. Air leakage from the bottom of the ash hopper causes the ash accumulated inside it to become airborne again, reducing the dust removal efficiency. If tax evasion occurs through things such as flue gate mechanisms and insulation sleeves, it not only increases the amount of flue gas that needs to be treated, but also leads to the formation of condensation water due to temperature drops, which can cause the corona wires to swell, as well as issues such as \"creepage\" and corrosion in the insulation sleeves. 83. Why are tests conducted on electrostatic precipitators? Answer: The electric dust collector in coal-fired power plant boilers serves as both an environmental protection device for preventing air pollution and a production equipment that helps reduce wear on the exhaust fans and ensures the safe operation of the power generation units. Whether it is about developing and using new types of electric dust collectors or upgrading existing older models, testing these devices is an essential step. The main purposes of such testing are: 1. To check whether the dust emission level or dust removal efficiency of the electric dust collector meets environmental regulations. 2. Identify the existing problems with the current electrostatic precipitators, providing a scientific basis for eliminating defects and improving the equipment. 3. Conduct assessment and acceptance of newly installed electrostatic precipitators, understand their performance, and establish reasonable operating procedures to ensure their efficient, stable, and safe operation. To develop new types of electrostatic precipitators, accumulate data to further improve the level of electrostatic precipitation technology, and create the necessary conditions. 84. What are the effects of uneven air flow distribution on the operation of an electrostatic precipitator? Analyze the causes and methods to improve air flow distribution Answer: (1) The impacts on electrostatic precipitators are as follows: 1. The amount of dust captured varies in areas with different air flow speeds; the dust removal efficiency is higher in areas with lower speeds. Overall, the impact of high wind speeds is greater than that of low wind speeds. 2. Erosion occurs in areas with high local air flow speeds, leading to secondary suspension of particles. 3. Dust accumulation in certain parts of the dust collector further undermines the uniformity of the air flow. (2) The main reasons for this are: 1. Uneven distribution caused by the boiler. 2. Uneven distribution caused by friction in the flue. 3. Disturbances caused by the significant decrease in velocity on the inner side as the gas flows around the bends in the flue, due to the small radius of curvature of those bends. 4. Excessive dust deposition in the flue causes severe disruption of the airflow. 5. The rapid diffusion of the imported smoke box results in high central flow velocities, leading to uneven airflow distribution. 6. Air leakage from the body, etc. (3) Methods for improvement include: 1. Correctly selecting the flue cross-section and the inlet smoke box of the dust collector cross-section. 2. An air flow distribution plate is installed at the inlet side. 3. Install guide vanes in the smoke box system. 85. Why is it necessary to adhere to the principle of \"safety first\" in electricity production? Answer: (1) The characteristics of electricity production are a high degree of automation and the simultaneous completion of generation, supply, and distribution. Many power plants, transmission lines, substations, and electrical equipment work together to form an interconnected power grid. Such production requires extremely high reliability. Additionally, electricity cannot be stored in large quantities; therefore, the importance of safety in electricity production is much greater than in other industries. (2) As for the role of the power industry in the national economy, it not only provides power for various industries but is also a service sector essential to the general public. Should an accident occur, it would not only affect the personal safety of workers and the safety of equipment within the power industry itself, but could also have significant social consequences. Therefore, the principle of \"safety first\" in electricity production is not a arbitrarily decided policy, but rather one determined by the objective laws of electricity generation. (3) As for the power industry itself, if production is not safe, it is impossible to achieve full capacity operation, stable power supply, minimal losses, and civilized production, which will affect the survival and development of power enterprises; therefore, the principle of \"safety first\" must be adhered to in power production. 86. What are protective grounding and neutral grounding? Why is it not good to have no ground connection or neutral connection? Answer: Protective grounding means connecting the metal enclosures and supports of the non-electrified parts of electrical equipment to a grounding device via conductors, thereby reducing the voltage relative to the ground to a safe level. In the event that the insulation of live parts gets damaged and those parts become energized, this measure helps prevent electric shock accidents. It also helps protect the equipment from damage during lightning strikes. The so-called protective zero connection involves connecting the enclosure of electrical equipment to the neutral wire of a three-phase four-wire power supply. When the insulation of the electrical equipment is damaged, this causes a single-phase short circuit, which leads to the shutdown of the circuit or the blowing of a fuse, thereby cutting off the power supply to the faulty device and protecting human safety. 87. Why must a person stand at the axial position of the rotating machinery when starting its trial operation? Answer: The “Safety Work Regulations for the Electric Power Industry” clearly stipulates that when conducting a trial start of rotating machinery, the operator should hold the emergency stop button and stand at a position axially aligned with the rotating machine. This is because: the equipment has just undergone maintenance; the rotating machinery has not yet been dynamically balanced; and the stability of the components on the rotor has not been tested under rotation. Under high-speed rotation, there remains a possibility that certain parts may be flung off the rotor due to centrifugal forces acting upon them in the face of intense vibrations. Once the fragmented parts fly off the rotating body, the orientation perpendicular to the axis is the most dangerous area. The axial orientation is relatively safer, which prevents thermometers with objects attached from causing injury. To ensure personal safety, when starting the trial operation of rotating machinery, one must stand at the axial position of the rotating machinery. 88. What are the inspection items before putting an electrostatic precipitator into operation? Answer: (1) All work tickets must have their completion procedures finalized, all listed safety measures removed, and permanent barriers, signs, etc. restored to their normal state ； (2) All equipment components are complete, with clear and correct markings; all flange joints are tight, the insulation is intact, and the lighting is sufficient ； (3) All motors have been wired properly, with the ground connections secure; safety guards are in place and there is no friction with the rotating parts ； (4) All rotating equipment such as shaking devices and ash discharge machines operate smoothly; the oil levels in reducers are normal, and the oil quality is satisfactory ； (5) All ash hopper gates are fully open, and the level gauge indicates normal readings. (6) The high-voltage silicon rectifier transformer compartment is clean, free of debris; the insulating porcelain components are clean and undamaged. There is no oil leakage from the transformer or reactors, the oil quality is satisfactory, the oil level is normal, the silicone components are in good condition, the thermometers are functioning properly, the current-limiting resistors are intact, the connection wires are in good condition, the high-voltage isolators are properly connected, the operating mechanism is flexible and in the grounded position, and all high-voltage isolation compartments are locked ； (7) All instruments, power switches, protective devices, control devices, temperature monitoring devices, alarm signals, indicator lights, etc. are in good condition, complete, and functioning properly. 89. Discuss the main precautions for electric dust collector testing. Answer: (1) Before testing, a detailed test plan should be formulated by taking into account the characteristics of the electrostatic precipitator, as well as the boiler load and operation schedule ； (2) Organize technical training for the testers, and conduct preliminary tests once or twice based on actual conditions, in order to gain a thorough understanding of the organization of the tests, the key aspects of testing procedures, and the necessary coordination among team members, while also gaining an initial grasp of the operating characteristics of the equipment. (3) Before testing, all testing instruments and meters should be carefully inspected; any abnormalities found should be addressed and replaced promptly. (4) Before testing, fully solicit the requirements of the dispatchers, shift supervisors, and boiler operators to maintain the specified test conditions. (5) During the test, test personnel must remain at their posts and conscientiously record all raw data. (6) The test supervisor should regularly monitor the key operating parameters of the boiler and electrostatic precipitator during the testing process, conduct inspections of all areas where testing and sampling are taking place, and address any issues that arise promptly. (7) The samples collected for testing must be properly stored by a designated person using specialized equipment; it is not allowed for the samples to lose their integrity or to become contaminated with external impurities. (8) Testing work shall comply with the relevant provisions of safety work procedures. 90. Explain the reasons for the high vibration of the dust collector’s shaking reducer, abnormal noises, and oil temperature that is higher than normal, as well as the methods for addressing these issues. Answer: Cause analysis: 1. The bolts of the foot or end cover are loose. 2. Severe oil deficiency can even cause wear or damage to components such as the pin wheel. 3. Damage to the electrode or reducer bearings. Solution: 1. After centering, secure the foot bolts. 2. Disassemble and repair the reducer or motor. 91. Under what circumstances should an electrostatic precipitator be shut down urgently or the electric field stopped? Answer: 1. The high-voltage output terminal is short-circuited. 2. Flashover of insulating components ； 3. The oil temperature of the high-voltage silicon rectifier transformer exceeds the tripping temperature of 85 degrees yet no trip occurs, or phenomena such as oil spraying, oil leakage, and abnormal noises appear ； 4. Severe excitation deviation in the high-voltage power supply device ； 5. The high-voltage power supply device tripped automatically; the cause is unknown. It is permissible to attempt to restart it once. If it trips again, the cause must be identified and the fault resolved before attempting to restart it again ； 6. The high-voltage thyristor cooling fan has stopped rotating, causing the thyristor components to overheat severely ； 7. Short circuit in the electric field of the electrostatic precipitator ； 8. Changes in the operating conditions of the electrostatic precipitator, oil combustion in the boiler, or low flue gas temperature and dew point temperature ； 9. Equipment such as the anode and cathode rapping devices in electrostatic precipitators experiences severe vibration, leading to bent or damaged bearings; motors overheat and start smoking, and in some cases even catch fire ； 10. High-voltage damping resistors can experience flashover, or even catch fire. 92. Analyze the reasons for \"normal secondary voltage and significantly reduced secondary current.\" Answer: The reasons are as follows: 1. Excessive dust accumulation on the dust collection plates. 2. Or the rapping device of the corona stage is not turned on or is malfunctioning. 3. Enlargement of the corona wire leads to poor discharge. 4. The dust concentration in the flue gas is too high, resulting in corona closure. 93. What are the inspection items for the electrical part before putting an electrostatic precipitator into operation? Answer: The inspection of the electrical components before putting the electrostatic precipitator into operation must be carried out in strict accordance with the provisions of the \"Electrical Safety Work Procedures\" ； The grounding systems for electrical equipment shall comply with the provisions of the \"Technical Regulations for Grounding Design of Electrical Equipment.\" It is necessary to check whether the insulation and voltage-withstand test records of high-voltage electrical equipment components meet the required standards, whether the high-voltage isolators operate smoothly and their position indicators are accurate, whether the grounding resistance of the electrostatic precipitator itself and the insulation resistance of the high-voltage silicon rectifier transformers meet the requirements, whether the insulation oil meets the voltage-withstand test criteria, and whether the insulation resistance, DC voltage-withstand tests, and leakage current test records of high-voltage cables comply with the provisions of the \"Regulations for Preventive Testing of Electrical Equipment.\" ； Check whether the enclosure of the high-voltage silicon rectifier transformer and its various components are in good condition, whether the wiring in the control cabinet is correct, whether all motors are properly wired and secured, whether the grounding wires and protective covers are intact, and whether all instruments, power switches, protection devices, control devices, alarm signals, and indicator lights are present and functioning correctly. Also, verify whether the high-voltage isolator room and the distribution room are closed. 94. What are the symptoms of a \"complete short circuit\" fault in an electrostatic precipitator? What is the reason? Answer: The phenomena of a complete short circuit in an electrostatic precipitator include: 1. The operating current rises significantly, while the voltage reading is zero. 2. The secondary current increases sharply during operation, and the secondary voltage is zero. 3. The main circuit trips and an alarm is triggered. The reasons are: 1. The temporary grounding wire of the component was not removed in time. 2. The polar wire breaks and falls off, causing a short circuit between the anode and cathode or connection to the housing. 3. The disconnector on the high-voltage side or the switch on the field side is incorrectly switched to the “grounding” position. 4. The porcelain shaft is damaged, causing a short circuit to ground. 5. Short circuit to ground in high-voltage cables or cable terminations. 6. Rust in large patches forms on the plates or other components, causing a short circuit by creating a bridge between the anode and cathode. 7. Breakdown and short-circuit of the silicon stack, or short-circuit in the secondary winding of the transformer. 8. Enlargement of the cathode wire or severe ash accumulation on the anode plate, resulting in an inter-electrode short circuit. 9. A long-time full load of the ash hopper, together with the connection at the lower part of the cathode, causes a short circuit. 10. Short circuit on the high-voltage output side of the rectifier transformer. 95. Analyze the causes of incomplete short circuits in electrostatic precipitators. Answer: The phenomena of \"incomplete short circuit\" in electrostatic precipitators include: 1. Sudden fluctuations in the secondary voltage and current. 2. The secondary current is too high, resulting in a low secondary voltage. The reasons are as follows: 1. Excessive dust adheres locally to the cathode and anode, reducing the actual distance between the two poles and causing frequent arcing. 2. Contamination or dew on the insulating components leads to electric leakage and poor insulation. 3. The cathode wire is damaged but not yet completely detached; it swings with the flow of smoke or when the anode frame experiences significant vibration. 4. After the rust on the components has been removed, there is still no connection between them and the electrodes, but the distance between the two poles has been significantly reduced. 5. There is an incomplete short circuit from the high-voltage side to ground. 6. The cable insulation is poor, resulting in leakage current. 7. The level indicator is malfunctioning; this is caused by an excessive amount of ash in the ash hopper, resulting in an incomplete short circuit between the anode and cathode. 96. Analyze the causes of the phenomena that occur when the rectifier transformer in an electrostatic precipitator becomes open-circuited. Answer: 1. The secondary voltage rises above 30 KV, but the secondary current remains zero. 2. Cabinet pressure trip, alarm. 3. The alarm indicator light on the high-voltage cabinet panel is on. Reason: 1. The damping resistor has burned out. 2. The high-voltage isolating switch is disconnected or has poor connection. 3. The working ground wire is disconnected. 97. Analyze what are the causes of ash buildup in the ash hopper? Answer: Reasons: 1. Hammers, iron pieces, broken corona wires, or debris left over from installation fall into the ash hopper and get stuck in the valve. 2. Poor heating and insulation of the ash hopper, air leakage through the partition plates, or moisture causing the ash to become damp and stick together. 3. The ash discharge machine uses sliding bearings that are not wear-resistant, which causes the valve to stick and fail to operate. 98. What are the minor maintenance tasks for high-voltage silicon rectifier transformers under normal conditions? Answer: Under normal circumstances, there are the following steps: 1. Clean the main unit, check for any defects, and address them. 2. Clean all insulating porcelain components and check for any signs of discharge or tracking. 3. Check each joint for any signs of looseness or overheating, and take corrective action if necessary. 4. Check whether the oil level is normal and take appropriate action. 5. Check whether the gas relay and protection devices are functioning properly. 6. Check whether the silicone inside the respirator has changed color; if so, it should be replaced. 7. Take oil samples for testing in accordance with the requirements of chemical supervision. 8. Check whether the body grounding is reliable. 9. Check the throttle valve for oil leakage and address it. 10. Defects that are identified during inspections, cannot be resolved through minor repairs, and do not affect station operation can be recorded in the technical archives for resolution during major repairs. 99. What are the contents of the inspection and testing of electrical equipment in electrostatic precipitators? Answer: The inspection and testing of the electrical equipment in electrostatic precipitators include: 1. Checking whether the main insulations of the high-voltage circuit components are satisfactory. 2. Check the high-voltage isolating switch; it should operate smoothly and reach the proper position. 3. Before debugging the high-voltage silicon rectifier transformer, measure the insulation resistance between the high-voltage and low-voltage windings as well as to ground; it should be greater than 200 M ohms. Additionally, conduct an induction voltage withstand test for 1 minute. 4. Before testing high-voltage cables, cable strength tests and DC leakage tests should be conducted. 5. AC and DC relays, as well as electrical measuring instruments, shall undergo routine tests in accordance with the prescribed procedures. 6. Before tuning the reactor, the insulation resistance of the windings to ground and the DC resistance between each tap should be measured. 7. Check whether the wiring of the primary and secondary systems of the electrical equipment conforms to the design principles. 8. Power on the low-pressure operation control equipment for inspection, test the alarm system, test the shaking circuit, and disassemble the ash transfer circuit for inspection. Power-on inspection of the heater temperature detection circuit, and operational testing of the high-voltage silicon rectifier transformer control circuit. 100. Describe the test methods for airflow distribution uniformity. Answer: The test for the uniformity of airflow distribution in electrostatic precipitators consists of two parts: the test for the uniformity of air volume distribution among each electrostatic precipitator, and the test for the uniformity of airflow distribution within each electric field of each electrostatic precipitator. The test method for the uniformity of gas flow distribution in each electrostatic precipitator is as follows: first, measure the amount of flue gas processed by each electrostatic precipitator, convert it to the equivalent amount under standard conditions, calculate the average flue gas volume, and then determine the relative deviation between the flue gas volume processed by each electrostatic precipitator and this average value. Generally, it is required that the relative deviation be less than 10%; for high-efficiency electrostatic precipitators, the requirement is that the relative deviation be less than 5%. The test method for the uniformity of air flow distribution in the electric field of an electrostatic precipitator is: (1) The tester enters the electric field and first sets up measurement points. The measurement points should be placed on the cross-section on the inlet side of each electric field, near the row of dust collection plates ； The measurement section should be at a distance of at least (8–10)d from the air flow distribution plate. In the horizontal direction, a measurement point is placed every 1–2 M in the measurement section, while in the vertical direction, 8–12 measurement points are generally taken along the height axis. When several electric fields are connected in series in an electrostatic precipitator, measuring the uniformity of the airflow distribution in the first electric field is sufficient to represent the uniformity of the entire precipitator. (2) Close the manhole cover and start the induced draft fan. (3) Measure each measurement point using a hot-wire anemometer. Each measurement point is measured more than twice, and the average value is taken. If the difference between the two measurements is too large, a new measurement is required. (4) Determine the uniformity of air flow distribution.