Atmospheric pollution electrostatic precipitators

Electrostatic precipitators have been used commercially for almost a century for the collection of particulates present in the gas streams on many industrial processes. The early plants were installed to recover valuable material that, otherwise, would have been lost to atmosphere, rather than in preventing atmospheric pollution. These plants, mainly in the sulfuric acid, bullion, and nonferrous smelting industries, were designed and priced to produce a commercial pay back in the order of 3-5 years. In recent years, with the increasing awareness and worldwide recognition of the problems associated with atmospheric pollution, most industrialized nations have enacted legislation to limit emissions from all sources. This legislation is continuously... 

Two commercially available aerosol mass concentration analyzers have been described for the determination of aerosols and particulates [18], The instruments are both portable and relatively rugged and operate on ordinary commercial power. A portable system utilizing an electrostatic precipitator was described for mass concentration measurements in the range of airborne dust particles smaller than 10 /Am [19]. Chuan [20] also described a typical commercial instrument based on the piezoelectric quartz crystal microbalance for the rapid assessment of particular mass concentrations in the atmosphere. The adhesive coating used in the device is non-hygroscopic and non-reactive to the usual concentrations of pollutant gases in the atmosphere, such as CO, SO2, NOjt, and hydrocarbons. 

Coal combustion releases fly ash into the atmosphere (Chapter 14) (Fisher and Natusch, 1979 Adriano et al., 1980). Fly ash contains toxic metals such as arsenic and cadmium. In the United States the Clean Air Act requires that fly ash be removed from coal emissions. As a result, antipollution devices such as air baghouses and electrostatic precipitators are used to trap these pollutants. 

Fly ash Airborne bits of unbumable ash that are carried into the atmosphere by stack gases coal ash that exits a combustion chamber in the flue gas and is captured by air pollution control equipment such as electrostatic precipitators, baghouses, and wet scrubbers. 

In addition, certain devices are used for pollution control in industry. They either destroy contaminants or remove them (from an exhaust stream) so they are not emitted into the atmosphere. Several examples are provided. An electrostatic precipitator removes (collects) particles from a flowing gas, using the force of an induced electrostatic charge. It can remove fine particles such as dust and smoke from a stream of air. 

Unconverted SOj, SO3 (mainly as sulphuric acid mist) and entrained organic acid are present in the exhaust gas and are the main potential atmospheric pollutants. The recommended practice is to use an electrostatic precipitator (ESP) to trap any particulate material in the form of mist or aerosols and a caustic soda scrubber which absorbs SO2 and small amounts gaseous SO3 that will pass the ESP. 

Most combustion gases that contain sulfiir dioxide also contain a small, but significant amount of sulfur tcioxide (or its reaction product with water, sulfuric acid). This component is of considerable importance because of its highly corrosive nature, its effect on the chemistry of many sulfur dioxide recovery processes, and its suspected critical role in air pollution problems. The amount of sulfur trioxide emitted to the atmosphere is a function of combustion air/fiiel ratio, fuel composition, combustion temperature, time at temperature, the presence or absence of a catalyst, electrostatic precipitator conditioning with ammonia, and the... 

Are waste products produced by the process In what quantities Are they potentially harmful if released untreated into the environment If so, in what way What should be done to reduce pollution hazards Chemically treat the wastes Dump liquid and solid wastes into containers, seal and cart them out to sea Disperse gases in the atmosphere with a high stack Precipitate solids electrostatically from gas exhausts ... 

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