Abstract
Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) emission characteristics and vapour/particulate phase partitions under three continued operation conditions, i.e. shut-down, start-up and after start-up, were investigated by sampling stack gas. The results indicated that the PCDD/F emission levels were 0.40–18.03 ng I-TEQ Nm−3, much higher than the annual monitoring level (0.016 ng I-TEQ Nm−3). Additionally, the PCDD/F emission levels in start-up were higher than the other two conditions. Furthermore, the PCDD/F congener profiles differed markedly between shut-down and start-up, and the chlorination degree of PCDD/F increased in shut-down and decreased evidently in start-up. Moreover, PCDD/F vapour/particulate phase distributions varied significantly under three transient conditions. The PCDD/F vapour phase proportion decreased as the shut-down process continued, then increased as the start-up process proceeded, finally more than 98% of the PCDD/F congeners were distributed in the vapour phase after start-up. The correlations between log(Cv/Cs) versus of each PCDD/F congener in stack gas were disorganized in shut-down, and trend to a linear distribution after start-up. Besides, polychlorinated biphenyl emissions show behaviour similar to that of PCDD/F, and the lower chlorinated congeners have a stronger relationship with 2,3,7,8-PCDD/Fs, such as M1CB and D2CB.
Highlights
Waste products generated by the chemical and hospital industries are classified as hazardous waste (HW) in China and include a wide variety of types, compositions and calorific values
The data of polychlorinated dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and other pollutants are shown in table 2
The results indicated that PCDD/F concentrations generated during transient conditions, were much higher than those under normal operation conditions
Summary
Waste products generated by the chemical and hospital industries are classified as hazardous waste (HW) in China and include a wide variety of types, compositions and calorific values. PCDD/Fs are partitioned as gas phase and particle-bound products (particulate phase). To control PCDD/F emission levels and meet the stringent standards, various types of air pollutant control devices (APCDs) would be equipped within HWIs. Vapour phase PCDD/Fs can be removed by various methods including adsorption on carbon-based adsorbents, or catalytic destruction, such as activated carbon injection (ACI) and selective catalytic reduction. While particulate phase PCDDs/Fs are largely controlled by electrostatic precipitator (EP) and bag filters (BFs). Among those devices available for use, ACI to adsorb vapour phase PCDD/Fs and BF to remove particulate matter are considered the simplest. Information on PCDD/Fs partitioning in vapour/particulate phases is important in selecting, designing and operating PCDD/F control equipment
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