In this project, some charged characteristics, and analysis of precipitated PM2.5 in high electrostatic field were calculated based on theories and experiments. The connection between the charge amount and the additional electric field intensity caused by the wet flexible collectors was studied to reveal the mechanism of charging enhancement of PM2.5 on flexible collectors. Some explanation about the wet ability of collectors and the current density enhancing the precipitation process was proposed in this project. Simultaneously, the results shows that both gas treatment time and applied voltage have an important influence on particle collection, and the minor factor was initial concentration.
Particle matter (PM) in air can lead to secondary aerosols absorbing various harmful compounds [
In this project, a new wet electrostatic precipitator had been evaluated for its effectiveness as an alternative control of particulate emissions. Particles collection consisted of three stages; charging the particles; collecting the charged particles on the collector; and cleaning. The connection between the charge amount and the additional electric field intensity caused by the wet flexible collectors was studied to reveal the mechanism of charging enhancement of PM2.5. The use of fabrics collection electrodes would offer the following advantages: Minor water addition rate, excellent corrosion resistant, low maintenance requirements, simplicity in operation, and uninterruptible power flushing.
The experimental setup for this study was shown in
The industrial smoke dust was screened to obtain test particles by electromagnetic high frequency vibrating screen. A real-time detection system (ELPI) was used to measure the variety of the number concentration under several conditions.
The overall current density curve of polypropylene fibrous collector was carried out to obtain electric behavior using negative high-voltage DC power as shown in
tage panel. The maximum working voltage was ensured under above-mentioned conditions.
The concentration of particles entering the ESP, Cin, and the concentration of particles leaving the ESP, Cout, were monitored by Electrical Low Pressure Impactor (ELPI). Thus, the collection efficiency could be derived as:
where η is the collection efficiency, Cin is the initial number concentration of fine particles, and Cout is the final number concentration at the outlet of the improved wet ESP.
As illustrated in
Applied voltage (kV) | Rigid (mA∙m−2) | Flexible (mA∙m−2) | IF/IR |
---|---|---|---|
10 | 0 | 0 | / |
20 | 0.05 | 0.10 | 2.00 |
30 | 0.14 | 0.26 | 1.86 |
40 | 0.28 | 0.50 | 1.79 |
50 | 0.45 | 1.14 | 2.53 |
60 | 0.75 | 1.31 | 1.75 |
overall efficiency curves had similar curvilinear trend under various working conditions. As illustrated in
The effects of water film on particle agglomeration in gas were investigated. Agglomeration is a process in which smaller particles adhere to a larger one, or in which smaller particles come together to form a larger one. As shown in
significance to particles agglomeration. Meanwhile, the number concentration of fine particles (<0.5 µm) declined substantially, and all repeated test indicated that there was significant effect on the particle agglomeration for wet collectors in gas. Furthermore, the maximum water evaporation addition rate was 25 L/(h∙m2) when the gas velocity was 3 m/s, respectively. It could be calculated that the decrease of the number concentration was not less than 40% for ultrafine particles (<0.5 µm) depend on the water film adsorption. In other words, the effect of water film adsorption on the temperature drop was more sensible. Meanwhile, it could be observed that as long as there was any water on the surface, any particle would exhibit similar agglomeration, whether at higher or smaller water addition rate. It could be concluded that the flexible collectors could maintain uniform wetting property and excellent adsorption via capillary penetration consuming smaller water, thus would allow lower water consumption in the applications.
The experiment was designed to investigate the mechanism on PM2.5 charging, precipitation in high electrostatic field. The connection between the charge amount and the additional electric field intensity caused by the wet flexible collectors was studied. The results show that the current density by flexible collector was 20 ~ 100 percent higher than that by rigid collector. The current density by flexible collectors were increased which would help to precipitate PM2.5 more easily than conventional steel materials. There was not obvious link between initial concentration and collection efficiencies, and the efficiencies at higher inlet concentration or lower concentration by flexible collectors were almost the same. The average number collection efficiencies by flexible collector amounted to 88.3% for PM2.5 when the gas residence time was 4 s at 60 kV. The number concentration of fine particles (<0.5 µm) declined substantially, and all repeated test indicated that there was significant effect for wet flexible collectors on the particle agglomeration in gas. The decrease of the number concentration was not less than 40% for ultrafine particles (<0.5 µm) depend on the water film adsorption.