Electrostatic precipitator collecting plates

Electrostatic precipitators collect particles that may subsequently be examined by microscopy. The method precipitates particles according to the charge they carry. The aerosol is passed between two plates or surfaces across which is a large potential difference. Deposition occurs as a function of the ratio of the charge to the inertia (mass and velocity) of the particles [87]. The principle on which this method is based considers the motion of particles in planes directly perpendicular to and parallel to the plane of the condenser [88]. 

A unit is available in which electrostatic precipitation is combined with a dry-air filter of the type shown in Fig. 17-64Z . In another unit an electrostatic field is superimposed on an automatic filter. In this case the ionizer wires are located on the leading face of the unit, and the collecting electrodes consist of alternate stationary and rotating parallel plates. Cleaning in this case is automatic and continuous. 

Fig. 29-10. Wet ESP with plate collection electrodes. Source Oglesby, S., ]r., and Nichols, G. B., Electrostatic precipitators in "Air Pollution," 3rd ed., Vol. IV (A. C. Stem, ed.), p. 239, Academic Press, New York, 1977.

The two-stage electrostatic precipitators used in light-industry applications are compact devices which can be fitted into the ventilation system. These air cleaners are normally used to clean air from dusts, smokes, and fumes in industrial workplaces. The basic features of these devices are the separate sections for particle charging and collection. The charging section consists of thin metal wires installed between grounded metal plates. The distance... 

Electrostatic precipitators are generally used to separate particulate matter that is easily ionized from a gas stream3,8,10. This is accomplished by an electrostatic field produced between wires or grids and collection plates by... 

A coal combustion pilot plant is used to obtain efficiency data on the collection of particulate matter by an electrostatics precipitator (ESP). The ESP performance is varied by changing the surface area of the collecting plates. Figure E2.2 shows the data collected to estimate the coefficients in a model to represent efficiency 17 as a function of the specific collection area A, measured as plate area/volumetric flow rate. 

Electrostatic precipitators devices used to trap fine dust particles (usually in the size range 30 to 60 p,m) that operate on the principle of imparting an electric charge to particles in an incoming airstream which are then collected on an oppositely charged plate across a high-voltage field. 

Wet electrostatic precipitators (WESP) are used for removal of liquid contaminants such as sulfuric acid mist, aerosols, and particulate matter. The acid mist and aerosols are typically formed in a WGS by condensation of SO3. Unlike dry precipitators, wet precipitators do not require rapping to remove the dust. The collected mist and particulate matter form a liquid film that runs down a vertical collecting plate. In some cases, a continuous spray of liquid is used to prevent solids deposition on the collecting plates. 

An example of a study in which this approach was applied involved the use of a transmission electron microscopy (TEM) grid as the collector plate in the electrostatic precipitator (Witkowski et a ., 1988). After sample collection, analysis by TEM (vide infra) could then be carried out. 

Fluid Electrode Precipitator. In general, the best way to remove fine dust from an air stream is to use conventional electrostatic precipitators. Although the efficiencies of these devices are quite high, there are inherent drawbacks that do not make them acceptable in continuously operating air systems. The collection plates eventually become saturated with the deposited... 

The collection efficiency of the wire-plate-type of electrostatic precipitator can be estimated by the widely used Deutsch theory [Deutsch, 1922]. To obtain the Deutsch equation, the following assumptions are made (1) because of the turbulent mixing effect, particle concentration at any cross section of the precipitator is uniformly distributed ... 

Fig. 4.3. Schematic of dry rod and plate electrostatic precipitator (after Oglesby and Nichols, 1978). The rods have sharp horizontal protrusions (nails) which promote corona formation. Dusty gas flows between the plates and around the rods. A large electrical potential (60 000 V) is applied between the rods and plates. This negatively charges the dust particles - causing them to approach and adhere to the positive collection plates. The dust is gathered by periodically rapping the plates, causing sheets of dust to fall into dust bins below, Fig. 4.4. Table 4.2 gives industrial precipitation data.

In Figure 20.8, several chambers are included in the rectangular chamber, each consisting of electrodes and collection plates. Generally, electrostatic precipitators are high-efficiency units but... 

You have been requested to calculate the collection efficiency of an electrostatic precipitator containing three ducts with plates of a given size, assuming a uniform distribution of particles. Also determine the collection efficiency if one duct is fed 50% of the gas and the other passages 25% each. Operating and design data include ... 

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