Electrostatic Precipitator

Tuesday, 23 August 2016

Electrostatic Precipitators Manufacturer, Ahmedabad, Gujarat, India



About Electrostatic Precipitator:
Electrostatic precipitators have been used widely in industry, and play an important role in environmental protection. Electrostatic precipitator (ESP) can be operated with a high collection efficiency and a low pressure drop. Recently, Electrostatic precipitator also has been used for cleaning indoor air. In this review, principles of electrostatic precipitation, such as particle charging, migration velocity of charged particles and collection efficiency are described. Performance of Electrostatic precipitator deteriorates by abnormal phenomena, including back corona for treating high resistivity dust, abnormal re-entrainment for low resistivity dust, and corona quenching for fine dusts. To cope with these phenomena, new technologies have been developed. Pulsed energisation is a technique to cope with high resistivity dusts, and these results in lower power consumption. Using pulsed energisation, non-thermal plasma can be generated and chemical reactions can be promoted for treating gaseous pollutants such as No and volatile organic compounds. Wet Electrostatic precipitator can also remove dusts and gaseous pollutants simultaneously; these new advancements will widen the field of application of electrostatic precipitation. Some novel applications of Electrostatic precipitators, such as removal of dioxin from incinerators, are also included in this review.

Electrostatic precipitators (ESPs) have been used for over 100 years to remove entrained solid particulates or fine mists from gas flows in the power, metal production, paper, cement, and other industries. As a response to ever changing state and federal regulations for coal - fired utility power plants, existing Electrostatic precipitators or new air quality control systems are needed to meet lower emission limits. Since many of these Electrostatic precipitators have been in operation for 30 to 50 years, many are in need of upgrades to improve performance and reliability. Even if a new pulse jet fabric filter will be installed downstream of an Electrostatic precipitator, an Electrostatic precipitator upgrade may be economical because the enhanced ESP could reduce maintenance costs and preserve fly ash sales. Many of the modern Electrostatic precipitator designs and controls can be installed in old Electrostatic precipitators. This article will address some of the general principles of dry electrostatic precipitators and discuss modern methods for upgrading Electrostatic precipitators.

Basics of Electrostatic Precipitator
Electrostatic precipitators can be designed for high volumetric gas flow rates, variable temperatures and pressures, and variable particulate loading. Precipitators have been placed in a number of locations at different power plants, including downstream of the economizer (hot side), downstream of the air preheated (cold side), or after a wet scrubber (which requires a wet Electrostatic precipitators). This article will focus on dry Electrostatic precipitators and will highlight typical upgrade options. With a properly designed electrostatic precipitator, 99% collection efficiency is possible with medium and high ash coals.

History and Principles of Electrostatic precipitators:
The first electrostatic precipitator was developed by a physical chemistry professor, Dr. Frederick Cottrell, in 1906. He was awarded a patent for his design on August 11, 1908. Mr. Cottrell successfully demonstrated in his research the precipitation of particulates from an air stream via particle charging in an electric field. The principles in this early design still apply today. Transformer-rectifiers energize discharge electrodes with a negative potential, producing an electrical field between the discharge electrodes and the positively-grounded collecting plates.

Particulate matter that enters the electrical field develops a negative charge and migrates away from the discharge electrodes and towards the collecting plates. When the particulates reach the collection plates, the negative charge is neutralized and a cake-like layer of ash accumulates. Migration and collection of the charged particles depends upon the particulate resistivity and the electrical field between the two electrodes, as well as the gas flow profile. Particulate matter that precipitates on the collection plates is periodically removed by mechanical rapping. The fly ash falls to collection hoppers from which it is then disposed.

Reasons for Electrostatic precipitator Upgrades:
A number of factors influence Electrostatic precipitators upgrades including performance degradation, increased maintenance, changes in particulate resistivity, volumetric flow rate changes, poor reliability, sodium ion depletion (primarily for hot-side Electrostatic precipitators), increased inlet particulate loading (typically due to dry sorbent injection), stricter emission regulations and compliance protocols, and even normal wear and tear such as plate warping and leaks in the casing. An Electrostatic precipitator upgrade will improve performance and reliability, which will reduce the plant's operating costs in the long run.

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