Measures for efficient and stable operation of the

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Measures for efficient and stable operation of electrostatic precipitator

electrostatic precipitator is a kind of efficient precipitator, which has been adopted by more and more thermal power plants. In order to maintain the long-term, efficient and stable operation of the electrostatic precipitator, the factors affecting the efficiency of the electrostatic precipitator should be analyzed, and the management of the operation, maintenance and overhaul of the electrostatic precipitator should be strengthened

1 factors affecting the dust removal efficiency of electrostatic precipitator

1.1 the design and operation of high and low voltage power supply control device is poor

reasonable corona power of electrostatic precipitator is one of the important factors to ensure the safe and stable operation of electrostatic precipitator. The DC high voltage of the electrostatic precipitator is supplied by 380 V AC current through the silicon controlled high voltage rectifier equipment. The electric field impedance of the precipitator is a variable load for the high voltage power supply device. When the electric field impedance increases and the current becomes small, the equipment is required to automatically boost voltage; When the electric field impedance decreases and the current increases, the equipment is required to automatically reduce the voltage to maintain the set current. The voltage and current sampling resistors inside the rectifier transformer introduce negative feedback signals, which are intelligently processed by the microcomputer to control the conduction angle of the thyristor, change the load output voltage, achieve the purpose of stable output, and make the electric field obtain the most effective corona power. However, the controllers produced by some power supply and control equipment manufacturers are not perfect in terms of equipment control characteristics, control methods, protection functions, etc. in addition, there is a certain blind area in the understanding of equipment principles by the power plant operation and maintenance personnel, resulting in poor operation of power supply control devices

1.2 the operation mode of rapping ash removal device is unreasonable

at present, all electric eliminators used in thermal power plants use rapping for ash removal. Under the condition that the rapping force and uniformity meet the requirements, whether the rapping system (cycle, time and mode) is reasonable has a great impact on the dust removal efficiency of the electrostatic precipitator

the impact of rapping cycle on dust removal efficiency lies in whether the falling dust blocks can directly fall into the ash hopper during ash removal. If the rapping cycle is too long and the dust accumulation on the electrode plate is too thick, the conductivity of charged dust on the electrode plate will be reduced and the dust removal efficiency will be reduced; If the rapping cycle is too short, the dust will disperse into fragments and fall, causing large secondary dust, that is, the dust deposited on the dust collector of the electrostatic precipitator will be carried out of the precipitator again by the air flow, especially the secondary dust of the terminal electric field will greatly reduce the efficiency of the electrostatic precipitator

there are many factors that cause secondary dust, such as high specific resistance of dust, uneven distribution of flue gas velocity that generates the anti corona dust collection electric field, or turbulence and eddy current caused by high velocity. Therefore, it is required that the flue gas flow rate in the electric field should not exceed 3 m/s. Generally, the flue gas flow rate in the electric field is about 1.5 m/s, and the flue gas flow should be evenly distributed as far as possible. The over frequency of rapping and dust removal is the main factor causing the secondary dust of the dust collector. Following certain procedures, adopting appropriate test methods, establishing a correct rapping system, and strengthening the maintenance of the ash discharge equipment of the ash hopper to prevent the blockage of the ash outlet of the ash hopper can prevent the occurrence of secondary dust

1.3 the operating parameters of the boiler deviate from the normal value

under normal load, the parameter values of the boiler's flue gas flow, flue gas temperature, flue gas dust concentration and other parameters have little difference with the design parameters of the electrostatic precipitator, and the electrostatic precipitator can operate normally. If the boiler flue gas flow increases, the flue gas temperature increases and the dust concentration in the flue gas increases, the operating condition of the electrostatic precipitator will deteriorate and the dust removal efficiency will be reduced. When the boiler operates at low load for a long time, in order to stabilize combustion, heavy oil or diesel oil must be used for combustion support, resulting in an increase in flue gas temperature and viscosity in flue gas. These viscous substances cause hypertrophy of cathode line and ash deposition on anode plate, resulting in reduction of dust removal efficiency of electric field. If the water vapor in the boiler leaks, it will increase the humidity of the flue gas. Although the specific resistance of the coal ash will be reduced due to the conditioning of the flue gas in a very short time, and the dust removal efficiency will be increased, if the time is a little longer, the electrostatic precipitator will seriously accumulate ash. Especially when the leakage is large, the electrode plate will even scale, which will reduce the service life of the precipitator foam granulator

1.4 change of coal type

if the boiler combustion coal type changes, its calorific value is lower than the design coal type, and its ash content is higher than the design coal type, it will increase the wear of coal handling, pulverizing, dedusting and ash conveying equipment, and shorten the equipment maintenance cycle. Using low calorific value coal will increase the actual coal consumption of the boiler and the ash content of the flue gas. This will cause the dust concentration of the flue gas treated by the electrostatic precipitator to exceed the design value, and the dust removal efficiency will be seriously affected. In order to eliminate the influence of coal type on the dust removal efficiency of the electrostatic precipitator, under the normal operation of the dust removal equipment system, each set of electrostatic precipitator shall conduct at least one characteristic test for typical coal type to determine the comprehensive impact of coal type, power supply and rapping on the efficiency of the electrostatic precipitator and find out the best operation mode of the electrostatic precipitator

2 strengthen the maintenance and overhaul of electrostatic precipitator

(1) DJ series microcomputer automatic control high and low voltage power supply device produced by Guodian environmental protection institute adopts advanced 8098 single-chip microcomputer and peripheral chips for its high-voltage control part, which has the characteristics of perfect control and protection functions, simple structure and convenient use, and provides a variety of power supply operation modes for the change of dust (fly ash) specific resistance emitted by boiler combustion in thermal power plant, Meet the requirements of various working conditions. By using this power supply device to transform the original equipment, the closed-loop control of the electrostatic precipitator can be realized by means of the feedback signal from the central machine and the dust turbidity detector, and the research results of the International Energy Agency (IEA) for efficient and energy-saving operation can be achieved. Its protection and alarm functions involve input overcurrent, output open circuit, output short circuit, undervoltage protection, partial excitation, thyristor open circuit and critical dangerous oil temperature, and almost cover all fault types in the operation of electrostatic precipitators in thermal power plants. We have launched monprene in ⑵ 3000 series SBC composite materials

(2) we strive to improve the operation status of electrostatic precipitators, strictly implement the guidelines for operation and maintenance of electrostatic precipitators, timely deal with faults and defects existing in equipment operation, and formulate perfect and reasonable maintenance cycles and projects

(3) locomotive maintenance. During overhaul, adjust the distance between cathode and anode in the electrostatic precipitator, and record the measurement results before and after adjustment. Check and deal with the wear of the equipment of the cathode and anode rapping devices (mainly rapping motors, reducers, shafts, bearings, flexible arm hammers, insulated connecting rods, etc.) which account for 65% of the enterprise's revenue from new material products at present; Inspect and commission the ash discharge system, insulation, heating system, ash hopper level meter, air lock and other devices

(4) electrical aspects. During the overhaul, the written regulations on the test items and cycles of high-voltage silicon rectifier transformer, low-voltage reactor, insulation support and connecting elements, high-voltage DC cable and other equipment in the chapter of electrostatic precipitator in the pre

protective test procedures for power equipment shall be strictly implemented. The performance test of the trigger device of the power supply device, the setting test of various protections, and the calibration of the electrical high-voltage and low-voltage circuits and instrument switches shall be carried out, Conduct core lifting inspection for rectifier transformer

(5) overall commissioning of electrostatic precipitator after overhaul. After overhaul, no-load boost test shall be conducted for rectifier transformer and electric field, and U-I characteristic test under rated working condition shall be conducted during operation; Test the temperature and pressure indication of inlet and outlet flue gas; Test turbidity meter and lighting equipment. If possible, the dust removal efficiency before and after the overhaul of the electrostatic precipitator shall also be compared to test the effect of the overhaul

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