Powder Resistivity Inferred Differential Collection of Heterogeneous Coal Fly Ash and Powered Activated Carbon Admixtures Within a Cylindrical Electrostatic Precipitator

Abstract

One of the primary goals of U.S. EPA’s Mercury Air Toxics Standards (MATS) is to remove approximately 90 % of mercury emissions from coal-fired power plants (CFPPs). Sorbent injection upstream of electrostatic precipitators (ESPs) has been the leading method for capturing mercury at CFPPs. However, electrostatic precipitators (ESPs) that are marginally sized and/or operated may face new performance challenges due to sorbent injection. Injected mercury sorbent particles having different properties (i.e., particle size, surface chemistry, or electrical properties), mixing with native fly ash, can potentially affect the collection behaviors of ESPs. The present study uses powder resistivity to study the differential collection behaviors within a cylindrical ESP by manually feeding admixtures containing Norit DarcoⓇ FGD powdered activated carbon (PAC) and fly ash samples from either Powder River Basin (PRB) or Illinois bituminous coals. Powder resistivity measurements, performed on fly ash admixtures at various PAC ratios (i.e. 0−10 wt. %) prior to ESP processing, serve as the initial resistivity data to infer the impact of PAC injection on ESP collection by comparing to powder resistivity of samples collected from the collection electrode. This study presents not only the evidence of differential collection behaviors within an ESP but also the implications for mercury emissions and the particulate matter (PM) control through ESPs.