Charged fraction and electrostatic collection of ultrafine and submicrometer particles formed during O₂-CO₂ coal combustion

The charged fraction of submicrometer and ultrafine particles generated during bench scale coal combustion and the subsequent penetration of particles through a cylindrical-wire electrostatic precipitator (ESP) in O₂-CO₂ and O₂-N₂ environments were measured. In all combustion environments, natural particle charging within the combustor was not adequate for high efficiency particle collection in the ESP; thus, corona generation was necessary for enhanced particle charging. With a positive applied potential, the corona inception voltage and voltage required to reach a given current level in the ESP in gas mixtures composed of O₂ and CO₂ were higher than those composed of O₂ and N₂, while similar voltages were needed for negative corona generation. In positive coronas, particle penetration through the ESP in O₂-CO₂ environments was 1-2 orders of magnitude higher than in O₂-N₂ environments. Little difference in particle penetration between O₂-N₂ and O₂-CO₂ was seen in negative coronas.