title: Characteristics of dioxin emissions from a Waelz plant with acid and basic kiln mode.
abstract: The concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were measured in the flue gas of a Waelz plant operated in acid and basic modes, respectively. To abate (PCDD/F) and other pollutants, the plant operates with a post-treatment of flue gases by activated carbon injection and subsequent filtration. Relatively high PCDD/F discharge by fly ashes is found with acid kiln mode of the Waelz process. Therefore, basic kiln mode of the Waelz process is investigated and compared in this plant. With the adsorbent injection rate of 7 kg/h (95 mg/Nm(3)), the PCDD/F concentration in stack gas was measured as 0.123 ng I-TEQ/Nm(3) in the basic operating mode. The added Ca(OH)(2) reacted with metal catalysts and HCl((g)) in the flue gas and thus effectively suppressed the formation of PCDD/Fs. PCDD/F concentrations in fly ashes sampled from the dust settling chamber, cyclone, primary filter and secondary filter in basic kiln mode were significantly lower than that in acid kiln mode. Total PCDD/F emission on the basis of treating one kg of electric arc furnace dust in the basic operation mode was 269 ng I-TEQ/kg EAF-dust treated which was significantly lower than that in acid mode (640 ng I-TEQ/kg EAF-dust treated).
authors.affiliation: Graduate Institute of Environmental Engineering, National Central University, Chungli 320, Taiwan.
authors.forename: Pao Chen
authors.initials: PC
authors.lastname: Hung
authors.forename: Kai Hsien
authors.initials: KH
authors.lastname: Chi
authors.forename: Mei Lien
authors.initials: ML
authors.lastname: Chen
authors.forename: Moo Been
authors.initials: MB
authors.lastname: Chang
mesh_terms: D000327:Adsorption; D000393:Air Pollutants / Q000032:analysis* / Q000302:isolation & purification; D001572:Benzofurans / Q000032:analysis / Q000302:isolation & purification; D002126:Calcium Hydroxide / Q000737:chemistry*; D002606:Charcoal / Q000737:chemistry; D060729:Coal Ash / Q000737:chemistry; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins / Q000032:analysis* / Q000302:isolation & purification; D004391:Dust; D005374:Filtration; D006256:Hazardous Waste; D006851:Hydrochloric Acid / Q000737:chemistry*; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives / Q000032:analysis / Q000302:isolation & purification
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D060729:Coal Ash; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins; D004391:Dust; D006256:Hazardous Waste; D000072317:Polychlorinated Dibenzodioxins; D002606:Charcoal; D002126:Calcium Hydroxide; D006851:Hydrochloric Acid