Electrostatic precipitators, pollutants

Figure 11.3 Electrostatic precipitation can be used to remove fine particles. (Reproduced with permission from Stenhouse, Pollution Control, in Teja, Chemical Engineering and the Enuironment, Blackwell Scientific Publications, Oxford, U.K., 1981.)...

E. Bakke, "The AppHcation of Wet Electrostatic Precipitators for Control of Eiue Particulate Matter," Preprint, Symposium on Control of Tine Particulate Emissions from Industrial Sources, Joint U.S.-USSR Working Group, Stationay Source Air Pollution ControlTechnology, San Francisco, Calif, Jan. 15—18, 1974. 

Handling of alumina and coke presents dusting problems. Hoods and exhaust systems collect the dust, which is then separated from the exhaust air either by cyclones, electrostatic precipitators, filter bags, or a combination of these methods, and recycled to the process (see Air pollution control PffiTHODS). 

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. 

The principal technological changes in the engineering control of air pollution were the perfection of the motor-driven fan, which allowed large-scale gas-treating systems to be built the invention of the electrostatic precipitator, which made particulate control in many processes feasible and the development of a chemical engineering capability for the design of process equipment, which made the control of gas and vapor effluents feasible. 

Fig. 29-9. Wet-wall ESP with tubular collection electrodes. Source Oglesby, S., Jr, and Nichols, G. B., Electrostatic precipitators, in "Air Pollution," 3rd ed., Vol. IV (A. C. Stern, ed.), p. 238, Academic Press, New York, 1977.

Operation and Maintenance of Electrostatic Precipitators." Specialty Conference Proceedings, Air Pollution Control Association, Pittsburgh, 1978. 

Englund, H. M., and Beery, W. T. (eds.), "Electrostatic Precipitation of Fly Ash," by Harry J. White. APCA Reprint Series, Air Pollution Control Association, Pittsburgh, 1977. 

Small solid particles, present in dust and grit emissions, have very low settling velocities (Table 4.4) The collection efficiencies of simple cyclones are tlierefore, as shown in Figure 17.3, relatively low. Fabric filters, electrostatic precipitators or wet scrubbers may be required to remove particles <5 pm in size with an acceptable efficiency. Therefore the cost of pollution control inevitably increases when dealing with particle size distributions skewed towards the lower end. 

The most important application of electrostatic precipitation is, however, the solving of environmental pollution problems caused by many heavy-iiidus try processes. The dimensions, corona voltages, and currents of these gas-cleaning systems are much larger than for ventilation electrostatic precipitators. Typical applications of industrial electrostatic precipitators are... 

Wliite, H. J. Control of Particulates by Electrostatic Precipitation. In Handbook of Air Pollution Tech nology, S. Calvert, and H. M. Engiund eds. New York John Wiley Sons. (1984), pp. 283-317,... 

ENVIRONMENTAL CONTROL EQUIPMENT Air Pollution Equipment Electrostatic Precipitators... 

L. Theodore, J. Reynolds, F. Taylor, and S. Errico, "Electrostatic Precipitator Bus Section Failure Operation and Maintenance," paper No. 84-96.10, presented at die 77di Aimual Meeting of Air Pollution Control Association, San Francisco, 1984. 

Van Wassen, R. H., Electrostatic Precipitators for Air Pollution Control, MTieelabrator Air Pollution Control, Pittsburgh, Pa. 

Ash particles produced in coal combustion are controlled by passing the flue gases through electrostatic precipitators. Since most of the mass of particulate matter is removed by these devices, ash received relatively little attention as an air pollutant until it was shown that the concentrations of many toxic species in the ash particles increase as particle size decreases. Particle removal techniques become less efiective as particle size decreases to the 0.1-0.5 pm range, so that particles in this size range that escape contain disproportionately high concentrations of toxic substances. 

Another critical part of the incinerator design is the pollution control system.11 Pollution control systems directly influence the levels and kinds of pollutants that are released and that can potentially reach the public. Most modern hazardous waste incinerators are designed with extensive air pollution removal systems. For example, a common pollution control system might include a system that cools or quenches gases produced by burning waste, followed by a system that reduces acid gas emissions, and ultimately followed by a particulate removal system such as fabric filters (bag-houses), electrostatic precipitators, venturi scrubbers, and others.10... 

These amines used as inhibitors show negative side effects (disturbances) when used for larger plants. They can be regarded as pollutants by themselves, and can disturb special devices in the plants, especially, when used on a larger scale, filters like electrostatic precipitators. Therefore, we have improved the inhibition method by the use of much safer inorganic compounds as inhibitors, such as. 

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