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Comparison of bag type dust collector and electric bag compound dust collector

1. Comparison of electrostatic precipitator and bag type dust collector
The coal type of coal-fired power plant is relatively stable, but it can not avoid the time when the coal or coal quality changes. The boiler system is a constant change and adjustment system. Therefore, the physical and chemical properties of the flue gas, the concentration of smoke and the dust, the temperature and other parameters from the boiler can not be guaranteed not to change. This series of changes will cause different changes for different precipitators. There are several aspects:
1. The air volume of the sending and draught fans is constant, and the concentration of smoke and dust at the outlet of the boiler is unchanged.
For cloth bag filter, the change of smoke concentration only causes the change of bag filter load, resulting in the change of dust removal frequency (automatic regulation). The dust concentration is high, the ash deposition rate on the filter bag is fast, the corresponding ash removal frequency is high, and vice versa, the frequency of ash removal is low, and the emission concentration will not change.
The electrostatic precipitator: the change of the dust concentration directly affects the charge of the dust, so it also directly affects the efficiency of the electrostatic precipitator, which is finally reflected in the change of the emission concentration. Generally, the concentration of soot increases, the efficiency of dust removal increases, the emission concentration increases correspondingly, the concentration of smoke decreases, the efficiency of dust removal decreases, and the emission concentration decreases accordingly.
2. The boiler smoke and dust volume is constant, and the air volume of the sending and draught fan changes.
For the bag filter, the change of the wind speed is caused by the change of the air volume, which causes the change of the resistance of the equipment, but has no effect on the efficiency of the dust removal. The air volume increases, the resistance of the equipment increases, and the output of the induced draft fan increases; conversely, the output of the induced draft fan decreases.
For electrostatic precipitator: the change of air volume has little effect on the equipment, but the efficiency of electrostatic precipitator is very obvious with the change of wind volume. If the wind volume increases, the electric field wind speed of the electrostatic precipitator increases and the residence time of dust in the electric field shortens. Although the electric field stroke disturbance enhances the effective drive speed of the charged dust, it is not enough to compensate the negative effects caused by the shortening of the residence time in the electric field and the aggravation of the two times of the dust in the electric field caused by the high wind speed. The efficiency of dust removal is very low; conversely, the efficiency of dust removal has increased, but the rate of increase is not great.
3. Change of temperature
The bag dust collector: the flue gas temperature is too low, and the condensation may cause the "paste bag" and the shell corrosion. The flue gas temperature is too high to be too high to allow the filter material to "burn the bag" and damage the filter bag. But if the temperature changes in the temperature range of the filter material, it will not affect the efficiency of dust removal. The temperature that causes adverse consequences is at the extreme temperature (accident / abnormal), so the bag filter must have effective protection measures for the limit temperature control.
The electrostatic precipitator: the gas temperature is too low, the condensation will cause the corrosion of the shell or the high pressure climbing, but it is good for the efficiency of dust removal; the temperature of the flue gas is higher and the increase of the dust than the resistance is not beneficial to the dust removal.  Therefore, the flue gas temperature directly affects the efficiency of dust removal, and the effect is more obvious.
4. Change in chemical composition of flue gas (or burning coal)
The bag filter: the physical and chemical composition of the flue gas has no effect on the dust removal efficiency of the bag filter. However, if the flue gas contains all components that are corrosive to all filter materials, it will directly affect the service life of the filter material.
For electrostatic precipitator, the physical and chemical composition of flue gas directly causes the change of dust resistance, which affects the efficiency of dust removal and has great influence. The most direct effect is the content of sulfur oxide in the flue gas. The higher the content of the sulphur and oxygen, the lower the dust than the resistance, the easier the dust capture, the higher the dust removal efficiency; on the contrary, the efficiency of the dust removal is low. In addition, changes in the chemical composition (such as silicon, aluminum, potassium and sodium content) will also lead to significant changes in the efficiency of dust removal.
5. Airflow distribution
There is no direct relationship between dust removal efficiency and airflow distribution, that is, airflow distribution does not affect the efficiency of dust removal. But the local air distribution in the dust collector should be as uniform as possible and can not be too large. Otherwise, the partial load of local load or jet wear will cause local breaking of the bag, which affects the normal service life of the filter bag of the dust collector.
Electrostatic precipitator: electrostatic precipitator is very sensitive to the distribution of airflow in the electric field. The distribution of airflow directly affects the efficiency of dust removal. In the performance evaluation of electrostatic precipitator, the root mean square index of air distribution is usually one of the important indicators to evaluate the quality of an electrostatic precipitator.
6, air preheater and system pipe leakage
To bag filter: the filter material with poor oxygen resistance will affect the life of the bag, for example, RYTON filter material, but the efficiency of the dust collector will not be affected. Due to the increase of air volume in the cold air system, the system resistance increases.
There is no obvious change in the resistance of the electrostatic precipitator. However, the increase of the air volume of the system increases the wind speed of the electric field and has an effect on the efficiency of the dust collector.
Two. Comprehensive comparison of electrostatic precipitator, bag filter and electric bag composite dust collector.
Taking the 300MW coal-fired unit as an example, the comparison between the split chamber positioning reverse blow bag filter and the electrostatic precipitator and the electric bag composite dust collector is as follows.

Comprehensive comparison table of bag filter, electrostatic precipitator and electric bag composite dust collector
Contrast content FMFBD - 30000
Bag type dust collector 5 electrostatic precipitator electric bag composite dust collector (1 electric field + cloth bag)
Treatment of flue gas volume 1780000m3/h 1780000m3/h 1780000m3/h
The area is 15 x 36 = 540m2 30 * 45 = 1800m2 30 * 36 = 1080m2
The initial investment is 14 million yuan, 13 million yuan and 16 million 500 thousand yuan
The design emission concentration is less than 30mg/Nm3 or less than 50mg/Nm3 30mg/Nm3.
The actual emission concentration of less than 30mg/Nm3 often exceeds the design value.