In order to study the emissions of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) during the transient and steady conditions of a medical waste incinerator (MWI) in east China

PCDD/Fs distributions and emission rate under different operating conditions of MWI was investigated. Flue gas sampling of MWI was conducted in accordance with operating conditions

start-up 1

start-up 2

start-up 3 and start-up 4 (four samples)

12 h after start-up(after-start 1

after-start 2

two samples) and 24 h after start-up (after-start 3

after-start 4

two samples). The I-TEQ values of flue gas were 1.68 ng I-TEQ·m-3 at the end of start-up and 2.77 ng I-TEQ·m-3 at 12 h after start-up

while the I-TEQ values of fly ash was 4.5 ng I-TEQ·g-1. The average concentrations of the PCDD/Fs emissions at start-up (0.78 ng I-TEQ·m-3) and after-start (1.5 ng I-TEQ·m-3) exceeded the emission limit (0.5 ng I-TEQ·m-3) for MWIs in China. The PCDD/Fs concentrations at 24 h after start-up (after-start 3

after-start 4) were still above the emission limit

which was proved as a "memory emission" effect due to the start-up conditions. The PCDFs/PCDDs ratio ranged from 0.14 to 0.95 at the beginning of start-up and from 5.46 to 6.29 during the after-start process

which meant PCDFs were dominant in the flue gases of MWI. PCDD/Fs congener profiles of flue gas samples during start-up and after-start were characterized by higher chlorinated PCDD/Fs. The PCDD/Fs congener profiles of fly ash samples were similar to flue gases

also mainly dominated by 2

3

4

7

8-PeCDF. PCDD/Fs in particle phase at the beginning of start-up accounted for 50%

while gas phase PCDD/Fs accounted for over 90% at 12 h after start-up. The PCDD/Fs emission rates of flue gas during start-up were much higher than normal conditions. The highest emission rate was 58.1 mg I-TEQ·h-1

40 times higher than the normal level. The total PCDD/Fs emission during start-up was 0.785 mg I-TEQ. The start-up of this MWI was approximately three times per year

and the start-ups of MWI accounted for 28% of the whole year's PCDD/Fs emission.