Heavy Metals' Absorption by Limes at High Temperature Incineration Flue Gas Incineration/Pyrolysis and Emission Control

摘要

In incineration factories, flue gas scrubbers are generally installed after heat recovery surface within the flue gas temperature range of 200～300°C or even below. Those scrubbers can collect most of the heavy metals and prevent their emission into the atmosphere but the air pollution control (APC) residues, namely fly ash, un-reacted absorbents and reaction products collected in those scrubbers are toxic and difficult to be disposed of. An effective method to improve the APC-residues' quality is to collect th em at high temperatures so that they are free from dioxins or even heavy metals. Limes are common absorbents for acidic ga ses, to check the absorption abilities of limes for heavy metals, four kinds of heavy metals were evaporated and then absorbed in flue gas with three kinds of limes. The experimental results we have got so far showed that: (1) The limes absorbed heavy metals with relatively low efficiency for the three tested heavy metals: Cu, Cd and Zn, only for Pb the absorption efficien cy is as high as 55.5 ～ 77.5% at 600°C, which may be partially due to condensation. And Cd is most difficult to be absor bed. (2) Among the three tested limes, the common slaked lime is most effective except that for Zn, to which CaCO_3 wa s more effective. (3) Appearing of other heavy metals in the flue gas at the same time would have negative influence on Pb and C u absorption. (4) Generally high temperature absorption is not a decisive method for heavy metals' emission control, and limestone or modified lime is suggested as absorbents for high temperature flue gas scrubbing in order to improve APC-residues' quality.