Ultra High Efficiency ESP for Fine Particulate and Air Toxics Control
Nearly ninety percent of U.S. coal-fired utility boilers are equipped with electrostatic precipitators (ESP). Cost effective retrofittable ESP technologies are the only means to accomplish Department of Energy's (DOE) goal of a major reduction in fine particulate and air toxic emissions from coal-fired power plants. Particles in the size range of 0.1 to 5 {micro}m typically escape ESPs. Metals, such as arsenic, cadmium, lead, molybdenum and antimony, concentrate on these particles. This is the main driver for improved fine particulate control. Vapor phase emissions of mercury, selenium and arsenic are also of major concern. Current dry ESPs, which operate at temperatures greater than 280 F, provide little control for vapor phase toxics. The need for inherent improvement to ESPs has to be considered keeping in perspective the current trend towards the use of low sulfur coals. Switching to low sulfur coals is the dominant approach for SO{sub 2} emission reduction in the utility industry. Low sulfur coals generate high resistivity ash, which can cause an undesirable phenomenon called ''back corona.'' Higher particulate emissions occur if there is back corona in the ESP. Results of the pilot-scale testing identified the ''low temperature ESP'' concept to have the biggest impact for the two low sulfur coals investigated. Lowering the flue gas temperature to 220 F provided the maximum impact in terms of decreased emissions. Intermediate operating temperatures (reduction from 340 to 270 F) also gave significant ESP performance improvement. A significant reduction in particulate emissions was also noted when the flue gas humidity was increased (temperature held constant) from the baseline condition for these moderately high resistivity ash coals. Independent control of flue gas humidity and temperature was an important and a notable element in this project. Mercury emissions were also measured as a function of flue gas temperature. Mercury emissions decreased as the flue gas temperature was lowered, indicating the native ability of ash to capture the mercury. Pulsed operation of the ESP with the SIR module provided a 2 to 3-fold reduction in emissions at the higher operating temperatures. In light of the positive results from Phase I, we propose proof of concept testing in the field in Phase II. The main objective of the Phase II testing would be to determine the ESP performance improvement as a function of flue gas temperature and humidity for a range of low-sulfur coals being fired by utilities. Equally important will be the long-term evaluation of the risk of corrosion and plugging (due to acid condensation) associated with low temperature operation. The impact of higher flue gas velocities (lower SCA-specific collection area), compared to the laboratory pilot program, would also need to be evaluated. A secondary objective would be to examine mercury capture by the ESP at the different temperatures and with sorbent injection.
- Research Organization:
- National Energy Technology Lab., Pittsburgh, PA, and Morgantown, WV (US)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE) (US)
- DOE Contract Number:
- AC22-95PC95259
- OSTI ID:
- 16490
- Report Number(s):
- DOE/PC/95259-98/C0912; CONF-970772-; ON: DE98051613; TRN: US200511%%117
- Resource Relation:
- Conference: Advanced Coal-Based Power and Environmental Systems, Conference location not provided, Conference dates not provided; Other Information: Supercedes report DE00016490; Supercedes report DE98051613; PBD: 1 Jul 1997; PBD: 1 Jul 1997
- Country of Publication:
- United States
- Language:
- English
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