Adding auxiliary electrode to the hottest electros

2022-07-31
  • Detail

Electrostatic precipitator (ESP) has become the main equipment for dust collection, recovery and gas purification due to its advantages of high dust removal efficiency, low resistance, large flue gas processing capacity and high heat-resistant temperature. It has been widely used in non-ferrous metal, metallurgy, electric power, building materials, petroleum, chemical industry and other industries. At present, the electrostatic precipitator mainly adopts conventional DC power supply. This power supply mode is easy to produce anti corona phenomenon for high-temperature fine and equal high specific resistance (≥ 0 ″ Ω· cm) dust. The dust removal efficiency is low, and the dust removal efficiency decreases with the increase of specific resistance. After several years of operation of electrostatic precipitator, there will inevitably be various failures. Due to the lack of maintenance for a long time, the equipment is aging, or the design, manufacturing and installation quality is poor, or the operating conditions change, the emission design indicators are not met, so there are many operating failures. In the operation of electrostatic precipitator, the occurrence frequency is high, the maintenance is difficult, and the impact on safety production is great. If it is not repaired in time, the fault will continue to expand, and even cause the shutdown of the electric field. The operation and management level of each electrostatic precipitator manufacturer is different. Except for the newly invested electrostatic precipitator, there are more or less problems, especially for the electrostatic precipitator designed as a two electric field, but with the failure of the electrostatic precipitator, it simply cannot achieve the emission design dust removal efficiency. Electrostatic precipitator is the largest environmental protection equipment of all enterprises. It is particularly important for environmental protection. Therefore, we must manage and use the electrostatic precipitator well. We must constantly analyze the causes, seek countermeasures and make improvements to make it play a greater role in environmental protection and dust removal efficiency. The dedusting mechanism of the electrostatic precipitator is to use the strong electric field strength generated by high voltage to ionize the gas, generate corona discharge, and then charge the dust, and separate the suspended particles in the gas under the action of the electric field force. Therefore, in the electrostatic precipitator, as the main body of corona discharge, it is directly related to whether the electrostatic precipitator can continue to operate efficiently and safely

during the operation of the electrostatic precipitator, because the flue gas condition is changing at any time, the applied voltage and current should be adjusted with the change of flue gas condition, otherwise the high-efficiency and stable operation of the electrostatic precipitator cannot be guaranteed. In order to make the electrostatic precipitator run efficiently, the automatic control must be realized according to the change of flue gas working condition, so that it can run at the highest voltage with certain spark discharge

the dust removal efficiency is the highest when the charging voltage is spark discharge to a certain extent. But in this case, the spark discharge is very unstable, because the degree of spark discharge is not necessarily related to its frequency. Under the control of saturated reactor, even if the spark discharge is very low, as long as a large spark discharge occurs, the current will be excessive to arc discharge. Therefore, it is not ideal to control only the spark discharge frequency. Therefore, the auxiliary electrode voltage regulating device is adopted, and the integral circuit multiplying the discharge current by the frequency is used for automatic control, so that the integral value can be kept at a certain value to control the average value of the transmission voltage. The automatic voltage regulating performance of the auxiliary electric level high-voltage power supply is relatively perfect, because its control system can automatically track the spark discharge of the electric field, control the output high voltage, and keep it near the spark discharge voltage of the electric field, Therefore, it is particularly suitable for use in those cases where the electric field conditions are relatively unstable and change frequently. Due to the high average voltage supplied to the electric field and the high dust removal efficiency of the dust collector, it has been widely used

most of the electrostatic precipitators with high-voltage automatic control failure are early products of various manufacturers. Except for simple repairable individual faults, most of them are difficult to repair. The reason is that the current control part is upgraded and the old model is not produced with spare parts. In this case, we adopted the method of replacing the new auxiliary electrode controller. For example, due to the control part of the electrostatic precipitator in a factory, the operating voltage and current are not stable enough, and the dust removal efficiency cannot meet the design requirements. The upgraded product of the new type of auxiliary electrode high-voltage power supply device of the electrostatic precipitator has been replaced, and the situation has changed greatly

theoretical research and practice at home and abroad have proved that the electrostatic precipitator using the three electrode auxiliary electrode power supply can provide a stable field strength, produce a sufficiently strong and uniform corona current density, inhibit the anti corona phenomenon formed by the high specific resistance dust in a certain range in the power plant, improve the dust removal efficiency, reduce the power consumption and the secondary dust of rapping dust, and reduce the dust collection area of the newly designed electrostatic precipitator. Therefore, the use of auxiliary electrode power supply has become one of the development directions of ESP power supply technology

I. brief introduction of equipment

1. The electrostatic precipitator body

auxiliary electrode power supply electrostatic precipitator is researched and developed by Mr. Hara Huiyi, an expert of electrostatic precipitator in Japan. It is a patented technology of Japa electrostatic precipitator D. due to the addition of auxiliary electrode (the third electrode) in the electric field, this electrostatic precipitator has formed a repeated double zone electric field, That is, the charged dust collection area and the uniform electric field dust collection area. The driving speed of the charged dust in the uniform electric field is significantly increased, and the positively charged dust can be captured, which suppresses the occurrence of anti corona and is conducive to the capture of high specific resistance dust. Compared with the ordinary plate type electrostatic precipitator, the total dust collection area is increased by 10%~20% under the same cross-sectional area, and the dust removal efficiency can be increased by 3~5 percentage points on the original basis, After the transformation of the existing electrostatic precipitator, the dust removal efficiency of 99.7%~99.9% can be achieved without increasing the electric field. The project is an innovation and a major breakthrough in the electrostatic precipitator industry. It has been widely used in petroleum, chemical industry, building materials, metallurgy, electric power and other industries at home and abroad, and won high praise from users

the horn pipe at the flue gas inlet of the electrostatic precipitator body adopts a two-layer perforated plate air flow distribution device to make the air flow distribution in the section of the electrostatic precipitator uniform and ensure the dust removal efficiency

the "floating tracking" shift fork rapping is adopted for the anode and cathode rapping, and the overall square cutting hammer head makes the rapping hammer not deviate due to the temperature change of the electrostatic precipitator, so as to ensure the transmission of the rapping force, achieve the ideal ash removal effect, and eliminate the frequent hammer falling and hammering of the traditional electrostatic precipitator

the horizontal trough plate technology is adopted at the outlet of the electrostatic precipitator, which is not only beneficial to the air flow distribution, but also can re capture the charged dust escaping from the electric field, prevent the secondary flying of dust, and strengthen the dust removal effect

the sand sealing device is adopted for the cathode hanging, the quartz sleeve and the electric porcelain pillar are adopted for the insulating parts, so that the insulation strength of the electrostatic precipitator is greatly improved. The 95 ceramic shaft, the most superior insulating ceramic shaft in China, is used as the insulating rotating shaft material for the cathode rapping. The universal joint is connected, and the funnel-shaped insulating box is used to avoid the problems of the rotating shaft fracture and the insulation damage caused by the ash accumulation in the insulating box that often occur in the cathode rapping, so as to ensure the long-term stable operation of the electrostatic precipitator

the shell and girder of the electrostatic precipitator are of integral frame structure with high strength. Ball type sliding support is adopted at the joint of end column and civil foundation to minimize the thermal thrust of electrostatic precipitator due to the change of flue gas temperature

2. High voltage power supply device

the high voltage power supply device matched with the electrostatic precipitator is the hl-iii constant current high voltage DC power supply. Its main working principle is that the AC sinusoidal voltage input is converted into AC sinusoidal current through the L-C constant current converter, and becomes a constant current high voltage DC current source after boosting and rectification to supply power to the electric field of the electrostatic precipitator. Compared with the traditional high-voltage DC power supply controlled by thyristor phase shift, it has the following characteristics:

a) stable operation, high reliability, long-term dust collection efficiency, and can withstand transient and steady-state short circuit. When spark discharge occurs in the electric field, because the output current of the power supply is "constant current", the current in the electric field will not increase, but the electric input current is greatly reduced, only 10% of the rated value, ensuring the safety of the power supply equipment. At the same time, due to the "constant current", the discharge channel disappears automatically without transition to arc discharge, protecting the corona wire, auxiliary electrode and dust collector

b) it can adapt to the change of working conditions, overcome the secondary dust caused by rapping, and has the ability to inhibit corona blocking and cathode hypertrophy. When the dust concentration in the electric field increases and the flow rate accelerates, the electric field is in a high resistance state. Since the output current is "constant", the voltage in the electric field will rise automatically, and the electric field will obtain more electric energy with good purification effect

c) the operating voltage is high, the discharge can be suppressed, and it is not sensitive to mechanical defects

d) the power supply has simple structure and adopts parallel modular design, which is convenient for maintenance and low power failure rate

e) with fast overvoltage protection, response time ≤ LMS

f) high power factor cos Ф> 0.90, and does not change with the operating power level, with obvious energy-saving effect

the outdoor high-voltage power supply device is adopted in the transformation, and the high-voltage cables and connectors are eliminated, so as to eliminate the leakage of high-voltage cables and connectors. The adopted high-voltage power supply is hl-iii-72/300-w type, with DC output voltage of 72kV and current of 300mA, AC output voltage of 380V and current of 72A. Each electric field is equipped with a set of high-voltage power supply device

3. Low voltage control device

the system is equipped with a power distribution cabinet to supply power to the high and low voltage electrical equipment of the electrostatic precipitator, cyclone, fan and ash conveying system respectively, which is convenient for management

the cathode, anode and gas flow inlet distribution plate rapping of the electrostatic precipitator have three control modes: PLC automatic program control, local manual operation control of the control cabinet and local field operation of the machine, which are convenient for operation, commissioning and maintenance. Due to the use of PLC control, the traditional hardware electromechanical control software has a high degree of automation and simple operation. It is equipped with rapping program randomly. The operator does not need to remember complex instructions, but only needs to select one of the rapping methods to realize automatic ash removal rapping. According to the actual production situation, the ash removal rapping system can be changed by programming

for the calibration of the electric heater speed of the electric precipitator incubator, the electric contact bimetal thermometer is used to realize automatic control. When the temperature is lower than a specified value, the electric heater will automatically heat up; When the temperature is higher than a specified value, the electric heater will automatically shut down, ensuring the temperature of the incubator and not wasting electric energy

low voltage startup is adopted for fan startup to reduce the impact on electricity during fan startup

the star type ash discharge valve and screw conveyor are controlled by centralized manual control in the control room, which is easy to operate and intuitive to display

in case of equipment failure, many famous Japanese chemical enterprises gather here to send out audible and visual alarm signals, so that the failure can be quickly found and repaired in time

4. Performance characteristics

the auxiliary electrode power supply of the electrostatic precipitator is a technical transformation of the original precipitator, that is, the DC power supply is changed into the auxiliary electrode power supply on the basis of the original power supply equipment. Evaluation results: under the condition that the operating conditions are basically the same, the dust removal efficiency of the electrostatic precipitator and the dust concentration at the outlet of the precipitator are compared, and the dust removal effects are between 99.6% and 99.8% respectively. The auxiliary electrode power supply has higher dust removal effect than the conventional DC power supply. The dust concentration at the outlet of the precipitator is reduced by 30%~70% on average. The auxiliary electrode power supply is used for dust with different characteristics in smelting plants, aluminum plants, cement plants, power plants, etc

an auxiliary electrode is formed at the low-voltage end of the rectifier, which can make the power supply equipment have good safety and reliability, and the frequency needs to be adjusted; The auxiliary electrode power supply can increase the electric field strength between the plates, improve the current density distribution uniformity between the plates, and improve the operation condition of the electrostatic precipitator

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