Effects of Particle-Control Devices on Atmospheric Emissions of Minor and Trace Elements from Coal Combustion

摘要

Emissions of elements in total suspended particles and in discrete particle size intervals are compared from five coal utility boilers, equipped with either cold- or hot-side electrostatic precipitators (ESPs) or high-energy, venturi wet scrubber systems. Coal and ash samples collected from emission-control systems and samples of atmospheric discharges were analyzed by instrumental neutron activation analysis, atomic absorption spectroscopy, and x-ray fluorescence. Emissions of Cr, Mn, Zn, and Co were enhanced probably because of corroded internal metal surfaces of the scrubbers. Concentrations of several potentially toxic elements, including Br, As, Se, Sb, U, V, and Cr, in aerosol particles emitted from the scrubber were as much as 170 times greater than in aerosol particles from the ESP. Also, the scrubber emitted a greater proportion of aerosol mass in particles of respirable sizes than did units equipped with cold-side ESPs. We conclude that the wet scrubber systems tested would be less effective in reducing the potential hazard associated with the elements cited above than a cold-side ESP of comparable overall efficiency. Based on their relative concentrations in total suspended aerosol particles and in discrete size fractions, it appears that Se, Mo, and Cr, and to a lesser extent As, Ba, Ga, U, V, and In, may be less effectively collected by the hot-side ESP than by the cold-side ESPs tested. (ERA citation 05:007580)