Study On Emission Characteristics And Control Of PCDD/Fs From Typical Industries

Polychlorinated dibenzo-p-dioxins and dibezofurans (PCDD/Fs) are potential riskpollutants for ecosystem and human health due to their properties of strange toxicity, stabilityand bioaccumulation. Waste incineration, ferrous and non-ferrous metal production, powerand heating, mineral production, transport, open burning processes are main PCDD/Fssources, and the emission characterizations are different in various sources. It is significativeto investigate the emission concentrations and characterizations of PCDD/Fs, which help tounderstand the PCDD/Fs formation mechanisms, adopt reasonable pollution control measuresand define responsibilities.This paper investigated the emission concentrations and characterizations of PCDD/Fsfrom municipal solid waste incinerators (MSWI), secondary non-ferrous metallurgy andferrous productions, the affect of production technology and air pollution control devices(APCDs) on PCDD/Fs emission are also studied. The results showed as follows:(1) Comparison of toxic equivalent quantity (TEQ) in stack gas and fly ash from typicalindustriesThe result showed that PCDD/Fs concentrations in stack gases from solid wasteincinerator, secondary non-ferrous production and ferrous production were relatively high,and there were some different emission characterizations in various industries. The TEQconcentrations of PCDD/Fs in stack gases of various industrial sources ranging form high tolow were as follow: fluid-bed MSWI (9.85ng I-TEQ/Nm3)>Secondary aluminum production(SAl,1.47ng I-TEQ/Nm3)> Secondary Copper production (SCu,1.13ng I-TEQ/Nm3)> gratefurnace MSWI (0.43ng I-TEQ/Nm3)> Iron ore sintering (Sinter,0.22ng I-TEQ/Nm3)>Electric arc furnace (EAF,0.18ng I-TEQ/Nm3)> Secondary lead production (SPb,0.04ngI-TEQ/Nm3).PCDD/Fs concentrations emission from fluidized bed waste incinerators were higherthan which from grate waste incinerators.TEQ concentrations of PCDD/Fs in fly ashes were little correlation with which in stackgases, which range from high to low were as follow: SCu (30.31μg I-TEQ/kg)>Hospitalwaste incinerator (HWI,26.03I-TEQ/kg)>SAl (14.73μg I-TEQ/kg)>MSWI (4.27μgI-TEQ/kg)>SPb (13.61μg I-TEQ/kg)>EAF(1.81ng I-TEQ/kg)>Sinter(1.02ng I-TEQ/kg).(2) Relevency between PCDD/Fs congener and total TEQ in stack gas and fly ash samplersPCDD/Fs congener profiles in flue gases from various industries were some differences,d the2,3,4,7,8-PeCDF is the most dominant contribution congener to the TEQ of PCDD/Fs. There is a good correlation between2,3,4,7,8-PeCDF concentrations and total TEQ ofPCDD/Fs in samplers from various industries. And the linear regression equation between2,3,4,7,8-PeCDF concentrations and total TEQ of PCDD/Fs in flue gas was y=0.913x+0.073,the correlation coefficient R2was0.9948, which PCDD/Fs TEQ concentrations range from0.0051to12.71ng I-TEQ/Nm3. It was y=1.008x+0.448in fly ashes, and the R2was0.9506.With in the permitted error,2,3,4,7,8-PeCDF can be used as the indicator of PCDD/Fs.(3) Pollution control in typical PCDD/Fs emission industriesThe TEQ of PCDD/Fs in fly ash from waste incinerator exceed3.0ng TEQ/kg, andshould be solidified before landfill. The heavy metal and its leaching toxicity wereinvestigated in the same time, Cu and Zn are the highest heavy metal content in fly ashes, andthe copper content in fly ashes from secondary copper production was11.8%, which can bereused in the actual production process. A variety of heavy metals leaching toxic of fly ashesfrom HWI were above the landfill admittance limit standard value, as well as the Pb in flyashes from MSWI, should be stabilized or solidified before landfilling.This paper also studied the PCDD/Fs emissions control of the small size wasteincinerator, the results showed: the PCDD/Fs removal efficiency in stack gas was51.1%afteruse activated carbon filter fabric (ACF) as the air pollution control device, while it came toabove90%by using activated carbon filter fabric and bag filter (BF) together. The PCDD/Fsemission concentration can be controlled and below the latest national emission standard inthis way, thus, joint use ACF and BF as APCDs is an effective technology to controlPCDD/Fs emission from small size waste incinerator.