Published: Oct 2012
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Electrostatic precipitators (ESPs), which are particulate collectors, are now used as part of the flue gas scrubbing strategy. In these combined systems, hydrated lime is injected into the flue gas ahead of the ESP to either neutralize or adsorb a gaseous pollutant. Then the ESP must remove the combined fly ash from fuel combustion, plus the unreacted rea-gent and reaction products. The primary parameter in ESP performance is the particulate resistivity. Particulate resistivity is a measure of how well the particulate, when deposited on the ESP collecting electrodes, conducts electricity to ground. Variations in resistivity from optimum to extremely high can change ESP particulate emissions by significant amounts. When injecting hydrated lime into the flue gas, we must be very concerned with the impacts of injected lime and reaction products on combined particulate resistivity in the ESP. Resistivity will have a greater impact on ESP performance than all other parameters combined. This paper is a study of the impacts on resistivity from injecting hydrated lime to treat flue gas. Lime and some of its reaction products are known to be somewhat high in resistivity, and its addition to the fly ash could be a concern in performance modeling. The impact of typical lime injection rates will be analyzed for impacts on fly ash resistivity. In addition, the - paper will also discuss the impacts of these resistivity changes on ESP particulate emissions.
Mastropietro, Robert A.
Vice President of Technology, Lodge-Cottrell Inc., The Woodlands, TX