Gas-and Solid-Phase Partitioning of PCDDs/FS on MSWI Fly Ash and the Effects of Sampling
Semi-volatile organic compounds (SOCs), including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs), are partitioned as gas-phase and particle-bound products of many industrial combustion processes. This gas/particle partitioning of SOCs has severe implications on both monitoring and control technologies. While particle-bound PCDDs/Fs are largely controlled by particulate collection devices such as fabric filters or electrostatic precipitators (ESPs), the gas-phase fraction may escape. Additionally, current real-time or near-real-time monitor development has focused on detection of the gas-phase fraction of SOCs, including PCDDs/Fs. Post filter gas-phase PCDDs/Fs have been reported to be greater than 50% of the total PCDD/F emissions when sampling the raw gas downstream of the boiler of a large scale municipal solid waste incinerator producing a low (<1%) carbon content fly ash. Others have reported that 50-90% of the PCDDs/Fs formed from thermal processes can be present in the fly ash fraction. This paper reports on a study to assess the potential bias to the actual emission gas/particle-phase partitioning using conventional sampling techniques. A novel sampling technique was developed and used to determine the actual partitioning during formation on MSWI fly ash in an entrained flow reactor (EFR). This partitioning was examined from both a reactor emissions and total formation view point in order to relate to sampling and monitoring applications in addition to mechanistic implications.
Ryan, S.; Touati, A.; Wikstrom, E.; Gullett, B. 2003. Gas- and Solid-Phase Paritioning of PCDDs/Fs on MSWI Fly Ash and the Effects of Sampling. Oranohalogen Compounds 63:45-58.