Sub-micron Particle Removal Efficiency of Electrically Enhanced Wet Scrubber A. Laitinen, K. Vaaraslahti and J. Keskinen

Wet scrubbers are mainly used to remove undesirable gaseous components from flue gases. Normally most scrubbers have low removal efficiency for fine particles. One way to increase the fine particle removal efficiency is to use pre-charging. Particles can be charged by corona discharge like in an electrostatic precipitator. Charged fine particles are removed by the combined effect of i. Inertial impaction of particles and droplets ii. Diffusion of particles to droplets and scrubber walls iii. Space charge force iv. Bipolar attraction between particles and droplets v. Image force attraction between particles and droplets / scrubber walls. Particles are also agglomerated in the charger in a precipitation / re-entrance process. Resulting large particles are removed in the scrubber by inertial impaction. Results from laboratory tests, several pilot installations and a full scale (biomass combustion) electrically enhanced scrubber are presented. For fine particles the removal efficiency was observed to be up to 92% for pilot installations and 86% for full scale installation. For pilot installations the removal efficiency depended strongly on particle properties and varied between 65 92%.