The ability to capture SO2 and halogens is one of the most important advant
ages of fluidized bed combustion (FBC), In order to clarify the affects of
chlorine in the absorption of SO2 emission, experiments involving the addit
ion of PVC to coals were carried out using the 0.3 m ID bench scale FBC sys
tem at Western Kentucky University. During the experiments, PVC was added t
o three coals in different percentages, and the mixtures fed into the FBC s
ystem. The Ca/S ratio was kept constant at 3:1. The experimental results in
dicate that chloride addition dramatically decreased the SO2 concentration
in flue gases. The sulfur and chlorine contents in both fly ash and bed ash
increased. At the same time, the utilization efficiency of calcium increas
ed with an increase in the PVC weight percent. This reduction in SO2 is att
ributed to more voids on the sorbent particle surface (limestone and/or ash
) through transient formation of a mobile halide ion-containing phase (CaCl
2), and to the reactions:
4HCl + O-2 <-> 2Cl(2) + 2H(2)O
Cl-2 + SO2 + H2O ,-> 2HCl + SO3.
A proposed mechanism involving the interaction between SO2 and HCl is discu
ssed in detail. (C) 1999 Elsevier Science Ltd. All rights reserved.