Electrostatic precipitator particulate collection

Gas cleaning by filtration, demisting, electrostatic precipitation, wet collection of particulates, cyclonic separation. 

Another device used to separate particulate and vapor phase PAHs is an electrostatic precipitator, consisting of a conducting surface to which an electric field has been applied. A corona is produced, which charges particles and allows them to collect on an oppositely-charged surface. A sorbent is placed downstream of the electrostatic precipitator to collect gaseous PAHs. The electrostatic precipitator is often referred to as an EA method (electrostatic precipitator-adsorbent). EA methods are less susceptible to sorption/desorption. The corona has the potential to destroy PAHs and create other artifacts by reactions with corona-generated ozone. ... 

There are hundreds of desulfurization processes proposed in the literature. These processes may be classified as wet and dry (Patkar, 1981). Spray drier absorption is a semi-wet system in which an alkali slurry is fed to the unit and the reaction product is collected dry. This process is generally applied to power stations. It is reported by Felsvang et al (1988) that spray drier scrubbers are in operation in power plants of over 10,000 MWe in different parts of Ae world. These absorbers are generally coupled with fabric filters or electrostatic precipitators to collect particulates. Spray drier absorption is experienced as a wet-dry system with different reagents such as lime, limestone, trona (natural soda) and ammonia. 

Cement plants in the United States are now carehiUy monitored for compliance with Environmental Protection Agency (EPA) standards for emissions of particulates, SO, NO, and hydrocarbons. AH plants incorporate particulate collection devices such as baghouses and electrostatic precipitators (see Air POLLUTION CONTROL methods). The particulates removed from stack emissions are called cement kiln dust (CKD). It has been shown that CKD is characterized by low concentrations of metals which leach from the CKD at levels far below regulatory limits (63,64). Environmental issues continue to be of concern as the use of waste fuel in cement kilns becomes more widespread. 

Particulate Emissions To meet environmental regulations, AFBC boilers, and some PFBC boilers, use a back-end particulate collector, such as a baghouse or an electrostatic precipitator (ESP). Compared to PC units, the ash from FBCs has higher resistivity and is finer Decause the flue-gas path contains cyclones. Both factors result in reduced ESP collection efficiency with AFBC units, but good performance has been achieved with PFBC units, where the SO3 present in the flue gas lowers the ash resistivity. In general, however, bag-houses are the preferred collection devices for both AFBC and PFBC apphcations. 

Electrostatic precipitators are satisfactory devices for removing small particles from moving gas streams at high collection efficiencies. They have been used almost universally in power plants for removing fly ash from the gases prior to discharge. Electrostatic precipitators have the capability of fine particulate control. Resistivity plays an important role in determining whether a particle can be readily collected in this device. 

Where low-grade coal is burned, electrostatic precipitators or fabric filters may be required for flue-gas particulate collection and a wet desulfurization system (gas scrubbers) to remove sulfur from the flue gas. 

Primary copper processing results in air emissions, process wastes, and other solid-phase wastes. Particulate matter and sulfur dioxide are the principal air contaminants emitted by primary copper smelters. Copper and iron oxides are the primary constituents of the particulate matter, but other oxides, such as arsenic, antimony, cadmium, lead, mercury, and zinc, may also be present, with metallic sulfates and sulfuric acid mist. Single-stage electrostatic precipitators are widely used in the primary copper industry to control these particulate emissions. Sulfur oxides contained in the off-gases are collected, filtered, and made into sulfuric acid. 

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. 

Catalytic processes (finid catalytic cracking, catalytic hydrocracking, hydro-treating, isomerization, ether manufacture) also create some residuals in the form of spent catalysts and catalyst fines or particulates. The latter are sometimes separated from exiting gases by electrostatic precipitators or filters. These are collected and disposed of in landfills or may be recovered by off-site facilities. The potential for waste generation and hence leakage of emissions is discussed below for individual processes. 

Mittal, et al. reported the proximate chemical composition of a number of different samples collected in the model card room at North Carolina State University (31). Samples in this study included a coarse trash which was comprised of relatively large, mostly lint-free particulate matter that fell to the floor of the condenser filter chamber in a Pneumafil filter system (Model FCV8-3MTRK) (31). The second sample set was separated by the sonic sifting procedure from the condenser trash. Another set of samples was collected from an electrostatic precipitator located in the air conditioning return of the model card room. Results of ash analyses are shown in Table VII. 

Elutriation is important in most industrial fluidized beds and is generally thought of as a disadvantage. In addition to the small particles which may be present in the initial particle size distribution, fines may be created in the course of operation by the attrition of bed particles. Elutriated particles usually need to be collected and recovered either because they represent the loss of product particles of a given size, because they must be separated from the exhaust gas for environmental reasons, or because of safety concerns there is a considerable risk of a dust explosion with very fine particles and perhaps especially so with many food particulates. Therefore the fluidized bed plant will require ancillary gas cleaning equipment such as a cyclone, filter or electrostatic precipitator to separate the fines from the gas. The loss of a particular size fraction from the bed may change fluidized bed behaviour and it then becomes important to return the fines to the bed continuously. 

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. 

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