Modification of electrostatic precipitator performance by use of fly-ash conditioning agents

Abstract

Pilot-scale (75 kg/h) combustion trials using a pulverized western Canadian coal of low sulphur content have shown that fly-ash resistivity can be significantly modified by use of SO3, H2SO4, NH2S02H, NH3, (NH4) 2 SO4, (C2H5) 3N and Na2SO4 as fly-ash conditioning agents. These conditioning agents were added as solutions to the combustion products and also, in some instances, as solids in the coal feed to the pulverizer. The measured fly-ash resistivity was found to decrease exponentially from its base level of 5 x 10 11 ohm-cm to a limiting value as the concentration of the conditioning agent increased. Optimum electrostatic precipitator efficiency always occurred at a resistivity of 5 x 10 9 ohm-cm. Reduced resistivity, however, was not always synonymous with improved precipitator performance.