Post-combustion syntheses of PCDD/F and PBDD/F from halogen-rich fuel is suppressed by a pebble heater technology

• Published in: Environmental science and pollution research international 2007-09, Vol.14 (6), p.414-420
• Main Authors: Schlummer, Martin, Mäurer, Andreas, van Eldik, Rudi, Quicker, Peter, Fischer, Werner, Faulstich, Martin
• Format: Article
• Language: English
• Subjects: Bromine; Chlorine; Combustion; Congeners; Cooling; Developing countries; Dioxins; Dioxins - chemical synthesis; Electronic equipment; Emissions; Emissions control; Exhaust emissions; Flame retardants; Furans; Furans - chemical synthesis; Gases; Halogens; Halogens - chemistry; Health risks; Heat transfer; Heaters; Heating equipment; High temperature; Incineration; Incineration - instrumentation; Incineration - methods; Landfills; LDCs; Legislation; Liquid chromatography; Mathematical analysis; Pesticides; Pilot Projects; Polychlorinated dibenzodioxins; Polymers; Temperature; Temperature gradients; Temperature requirements; Toxicity; Waste disposal sites; Waste treatment; Waste treatment plants; X-ray fluorescence
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1065/espr2006.11.362

Changes in German and European legislation shifted processing of polymer-rich shredding residues (SR) from landfill to thermal treatment. However, when waste of electric and electronic equipment (WEEE) is the source of SR, thermal treatment is complicated by halogens as well as the presence of polybrominated dioxins and furans (PBDD/F) and brominated flame retardants (BFR). Hence, WEEE requires high temperature incineration with sufficient residence times. Post-combustion synthesis of polyhalogenated dioxins and furans (PXDD/F) is dominant in the temperature range between 250-450 degrees C. Thus, a very rapid gas cooling from 450 degrees to 250 degrees C is important for proper raw gas treatment. The pebble heater technology developed by ATZ Entwicklungszentrum (Sulzbach-Rosenberg, Germany) might serve as an alternative to the state-of-the-art quench cooling. It is based on the application of a pebble bed of natural bulk material, which the exhaust gases flows through radially. It provides an excellent heat transfer and a temperature gradient in the range of 1,500-2,000 K/m. The paper presents data of a pilot application of the pebble heater technology for the treatment of raw gas derived from the incineration of polymeric materials from WEEE. A liquid fuel was chosen in order to minimise technical modifications of the plant. It was analysed for halogens by x-ray fluorescence, for brominated flame retardants by HPLC-UV/MS and for PXDD/F by GC-HRMS. Combustion gases were rapidly cooled down to temperatures below 200 degrees C and emissions of PBDD/F and PCDD/ F were estimated without further off-gas treatment. PBDD/F emissions were computed as PCDD/F toxicity equivalents applying two different calculation approaches. PCDD/F emissions accounted for 0.04 ng I-TEQ/Nm3 and are in compliance with European emission limits. Calculated PBDD/F toxicity equivalents exceeded the emission limit of 0.1 ng I-TEQ/Nm3 by factors of 75 and 208 depending on the calculation approach. A mass balance of PBDD/F and PCDD/F congeners revealed an efficient elimination of more than 95% in most cases. Lower reduction rates (76% for 2,3,7,8-TeBDF and 82% for 1,2,3,7,8-PeBDF) were attributed to incomplete combustion. An intended recovery of halogens by one-stage scrubbing downstream of the pebble heater was ineffective, recovering 28% of the applied chlorine and 9% of the bromine, only. Our pilot incineration test indicates that the pebble heater technology can effectively suppress a p