Influence of H2O and SO3 on fine particles coagulation for sintering flue gas after desulfurization in an alternating electric field

Electric coagulation of fine particles has been studied in the simulated sintering flue gas after semi-dry desulfurization to quantify the influence of H2O and SO3. The electric coagulation platform has a DC charging zone and an AC coagulation zone. Fine particles were divided into different diameter intervals to deeply explore the impact of H2O and SO3, including less than 0.15 mu m (PM0.15), 0.15-0.5 mu m (PM0.15-0.5) and 0.5-1 mu m (PM0.5-1). The particle charge, mass fractions of fine particles, and the mean diameter are measured and compared under water and SO3 atmosphere. The experiments showed that the increasing AC voltage helps particles larger than 0.5 mu m to coagulate but has little effect on the rest particles without H2O or SO3. Both H2O and SO3 enhance the PM1.0 AC coagulation. When flue gas relative humidity went up from 20 to 80%, the charge per particle maximally increased by 120%, as well as the mass fraction of PM0.5-1, PM0.15-0.5, and PM0.15 decreased by 83.2%, 64.5%, and 66.6%, respectively. When the SO3 concentration rose up from 0 ppm to 12.3 ppm, the charge per particle maximally increased by 100%, as well as the mass fractions of PM0.5-1, PM0.15-0.5, and PM0.15 decreased by 54.5%, 28.6%, and 33.3%, respectively. The impact of water and sulfuric mist on the particle intervals was sequenced as: PM0.5-1 > PM0.15 > PM0.15-0.5. The influence on PM1.0 AC coagulation was sequenced as H2O > sulfuric mist > AC voltage. Through data regression, H2O had approximate linear correlation with the particle mass fractions while the impact of sulfuric mist was non-linear. The interparticle forces were calculated to analyze the dominant force of particle AC coagulation with water: liquid bridge force > Coulomb force > > van der Waals force. The liquid bridge force indicated that liquid film was form on the surface of fine particles when water or sulfuric mist was added into the system which was the main reason enhancing the AC coagulation.