Mass Transfer within Electrostatic Precipitators:  In-Flight Adsorption of Mercury by Charged Suspended Particulates

Electrostatic precipitation is the dominant method of particulate control used for coal combustion, and varying degrees of mercury capture and transformation have been reported across ESPs. Nevertheless, the fate of gas-phase mercury within an ESP remains poorly understood. The present analysis focu...

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Bibliographic Details
Published in:Environmental science & technology 2006-06, Vol.40 (11), p.3617-3622
Main Author: Clack, Herek L
Format: Article
Language:English
Subjects:
01 COAL, LIGNITE, AND PEAT
20 FOSSIL-FUELED POWER PLANTS
ADSORPTION
Aerosols
Aerosols - analysis
Aerosols - chemistry
Air Pollutants - analysis
Air Pollutants - chemistry
Air Pollution - prevention & control
AIR POLLUTION CONTROL
Applied sciences
Atmospheric pollution
Chemical Precipitation
COAL
Combustion and energy production
ELECTROSTATIC PRECIPITATORS
Environmental Monitoring - methods
Exact sciences and technology
FLUE GAS
FOSSIL-FUEL POWER PLANTS
LAMINAR FLOW
MASS TRANSFER
MERCURY
Mercury - analysis
Mercury - chemistry
PARTICLE SIZE
PARTICULATES
Pollution
Prevention and purification methods
SPHERES
Static Electricity
TEMPERATURE DEPENDENCE
TURBULENT FLOW
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Summary:Electrostatic precipitation is the dominant method of particulate control used for coal combustion, and varying degrees of mercury capture and transformation have been reported across ESPs. Nevertheless, the fate of gas-phase mercury within an ESP remains poorly understood. The present analysis focuses on the gas-particle mass transfer that occurs within a charged aerosol in an ESP. As a necessary step in gas-phase mercury adsorption or transformation, gas-particle mass transferparticularly in configurations other than fixed bedshas received far less attention than studies of adsorption kinetics. Our previous analysis showed that only a small fraction of gas-phase mercury entering an ESP is likely to be adsorbed by collected particulate matter on the plate electrodes. The present simplified analysis provides insight into gas-particle mass transfer within an ESP under two limiting conditions:  laminar and turbulent fluid flows. The analysis reveals that during the process of particulate collection, gas-particle mass transfer can be quite high, easily exceeding the mass transfer to ESP plate electrodes in most cases. Decreasing particle size, increasing particle mass loading, and increasing temperature all result in increased gas-particle mass transfer. The analysis predicts significantly greater gas-particle mass transfer in the laminar limit than in the turbulent limit; however, the differences become negligible under conditions where other factors, such as total mass of suspended particulates, are the controlling mass transfer parameters. Results are compared to selected pilot- and full-scale sorbent injection data.
ISSN:0013-936X
1520-5851
DOI:10.1021/es050246+