Distribution of PCDD/F and PCB at Different Positions of Circulating Fluidized Bed Municipal Solid Waste Incinerators

Abstract

Because of a high moisture content and a low heating value of Chinese municipal solid waste (MSW), circulating fluidized bed (CFB) incinerators have been widely adopted in China for incinerating MSW since 1998. In this study, two typical CFB incineration plants (A and B) were investigated for contents and fingerprints of PCDD/F and PCB at different positions downstream their post-combustion zone, aiming to draw a full picture of formation and distribution of these organochlorinated pollutants. Both flue gas and ashes were sampled at five different positions of Plant A, from high-temperature superheater to outlet of baghouse filter, representing a huge range of flue gas temperatures; for Plant B, five ash samples were collected at different positions of the waste heat boiler (from high-temperature superheater to lower economizer). A continuous increase in contents of PCDD/F and PCB in flue gas was observed from superheater to inlet of air pollution control system (APCS) in Plant A, with the most significant rise noticed at air preheater. The load of PCDD/F and dioxin-like PCB in ashes also amplified steadily along the cooling path of flue gas in both plants. Changes in formation pathways are discussed based on homologue and isomer distribution patterns.