The objective of this article is to study the inhibition characteristics of SO2 on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) at various temperatures and to explore its inhibition mechanism by simulation of reaction process utilizing HSC Chemistry 6.1 software. Model fly ash and flue gas (10%O2/5%H2O/85%N2) were used as materials of the de novo formation of PCDD/Fs in a temperature range of 200-400℃. SO2 of concentration 200 mg·m-3 was added as inhibitor in inhibiting experiments. The suppression rate and homologue distribution of PCDD/Fs were analyzed to find SO2 inhibiting characteristics. The results showed that the control ability of SO2 was obvious and became stronger along with increase of temperature. Both total suppression rates and toxic equivalent concentration of PCDD/Fs increased with temperature

at 200℃ both below 20%

at 300℃ 75.6% and 77.3%

and at 400℃ up to 89.2% and 80.5% respectively. SO2 caused a lower-chlorinated distribution of PCDD/Fs

especially for PCDDs. At higher temperature

SO2 restrained chiefly PCDFs while at lower temperature PCDDs was mainly inhibited. Besides

SO2 showed selective inhibition for dioxin isomer. At 300℃ de-chlorination of high-chlorinated PCDFs

like HpCDF and OCDF

made 2

3

7

8-TCDF increase. Based on the computation for Gibbs free energy of pivotal reactions and their equilibrium composition

SO2 preferentially reacted with CuCl2

and CuSO4 formed had no catalytic activity. Then

reaction of SO2 with Cl2 made decrease of chlorine source. So

formation of PCDD/Fs was brought down. The results of reaction simulation could not only verify and replenished the sulfur inhibition mechanism existed but also could be an effective and creative method for exploring inhibition mechanism of different kinds of inhibitors like nitrogen-compounds. This could help develop high-effective inhibitors and apply in municipal solid waste incinerator practically.