Removal of PM2.5 from coal combustion based on heterogeneous condensational enlargement

Heterogeneous condensation of water vapor is used to increase the collection efficiency of fine particles from coal combustion exhaust gas. A novel process to removal PM2.5 from coal. combustion with high efficiency based. on the condensational enlargement with fine particles acting as nucleation centers in wet scrubber was presented. Water vapor was injected into the flue gas to achieve supersaturation and correspondingly cause particles to grow in size by vapor condensation. The grown particles were then removed efficiently in wet scrubber. The influence of vapor addition amount, initial particle size distribution, number concentration and liquid to gas ratio on collection efficiency were investigated. Particle number concentration and size distribution were measured in real time by Electrical Low Pressure impactor (ELPI). The results show that supersaturation vapor tends to condense on bigger particles. Accordingly, the removal efficiency increases with the particle size. At the vapor addition amount of 0.08kg per m(3) flue gas, the collection efficiency of greater than 80% can be obtained for the particle with a size of 0.4 mu m. The removal efficiency increases with the addition amount of water vapor, which can be improved over 70% with a vapor addition of 0.08kg/m(3) than without water vapor addition. With an increase in the particle number concentration the collection efficiency decreases at the same addition amount of vapor. Moreover, increase of liquid to gas ratio can improve the removal efficiency with the same vapor addition. The present study indicates that high removal efficiency can be obtained by condensational enlargement as a preconditioning technique to separate PM2.5 from coal combustion.