Characteristics of PCDD/F distributions in vapor and solid phases and emissions from the Waelz process

Journal Article · Wed Mar 15 00:00:00 EST 2006 · Environmental Science and Technology

OSTI ID:20741058

Chi, Kai Hsien; Chang, Shu Hao; Chang, Moo Been ^[1]

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1. National Central University, Chungli (Taiwan). Graduate Institute of Environmental Engineering

The Waelz process is a classic method used for recovering zinc from electric arc furnace (EAF) dusts containing relatively high concentrations of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) as well as volatile metals, such as Zn, Pb, and Cu, and chlorine. The EAF dust is mixed with coke (30%) and sand (20%) then fed into a rotary kiln. Significant PCDD/Fs are formed in the typical Waelz process, causing public concerns regarding PCDD/F emissions. In this study, flue gas and ash samplings are simultaneously conducted at different sampling points to evaluate the removal efficiency and the partitioning of PCDD/Fs between the vapor and solid phases in the Waelz plant investigated. With the environment (temperature window, sufficient retention time, chlorine, and catalysts available) conducive to PCDD/F formation in the dust settling chamber (DSC), a significantly high PCDD/F concentration (1223 ng TEQ/Nm{sup 3}) is measured in flue gas downstream from the DSC of the Waelz plant investigated. In addition, the cyclone and bag filter adopted in this facility can only remove 51.3% and 69.4%, respectively, of the PCDD/Fs in the flue gas, resulting in a high PCDD/F concentration (145 ng TEQ/Nm{sup 3}) measured in the stack gas of the Waelz plant investigated. On the basis of treating 1 ton of EAF dust, the total PCDD/F discharge (stack gas emission + ash discharge) is 840 ng TEQ/kg EAF dust of the Waelz plant investigated. Because of the lack of effective air pollutant control devices for PCDD/Fs, about 560 ng TEQ/kg EAF dust are discharged via stack gas in this facility. 16 refs., 7 figs., 2 tabs.

• OSTI ID: 20741058
• Journal Information: Environmental Science and Technology, Vol. 40, Issue 6; Other Information: [e-mail]; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
POLYCYCLIC AROMATIC HYDROCARBONS
BENZOFURANS
DIOXIN
EMISSION
ELECTRIC ARCS
ARC FURNACES
SLAGS
COKE
FLUE GAS
SAND
SILICA
ZINC
DUSTS
INDUSTRIAL PLANTS
METAL INDUSTRY
CLEANING
SAMPLING
QUANTITATIVE CHEMICAL ANALYSIS
VAPORS
SOLIDS
MATERIALS RECOVERY
AIR POLLUTION CONTROL
ASHES
REDUCTION
REDUCING AGENTS
WASTE PROCESSING PLANTS
RECYCLING
FABRIC FILTERS
PARTITION