Effect of residual carbon on precipitator performance

Hybrid electrostatic precipitator is one of prospective devices for ultra⁃low emissions in coal⁃fired industrial boilers because a single bag filter has been difficult to meet stricter emission standards. An experiment has been car⁃ ried out based on the coupling electric bag filter experimental system to investigate the effect of carbon residue on par⁃ ticle characteristics，dust removal performance，operating conditions and energy consumption of the bag filters and hy⁃ brid electrostatic precipitators. The results show that the bulk density increases slowly and then increases sharply as the carbon residue increases more than 18.18%. Compared to the bag filter，the total and grade dust mass concentrations at the outlet of hybrid electrostatic precipitators are lower， the total and grade dust removal efficiencies are higher，the blowing cycles are extended，the minimum pressure drop is reduced，and the total energy consumption is decreased. Moreover，dust removal performance is better with lower carbon residue of fly ash. The penetration win⁃ dows of the bag filter distribute at different particle sizes with different carbon residues. Also the hybrid electrostatics has no obvious penetration window expected for the fly ash with residual carbon less than 18.18%. The blowing cycles of both dust collectors decrease and the minimum pressure drop of both dust collectors increases as the number of blows increases. An average blowing cycle of the hybrid electrostatic precipitators for four kinds of fly ash is 3.27，4.27，4.91 and 1.92 times of the fiber filter，respectively. With carbon residue decreasing，the blowing cy⁃ cle of the fiber filter extends and the minimum pressure drop decreases，the blowing cycle of hybrid electrostatic pre⁃ cipitators first extends and then shortens and the minimum pressure drop decreases firstly and then increases. In addi⁃ tion，with the residual carbon reduction，the total energy consumption first decreases and then increases for the bag fil⁃ ter and first decreases and then increases for the hybrid electrostatic precipitators. Bag pressure drop is the main factor in the total energy consumption of the bag filters and hybrid electrostatic precipitators. Overall，the hybrid electrostatic precipitator is better than the bag filter in terms of dust removal performance，long⁃cycle operation and energy con⁃ sumption. Therefore，the hybrid electrostatic precipitator is one of the prospective ways to achieve ultra⁃low emissions for coal⁃fired industrial boilers.