GAS- AND SOLID-PHASE PARTITIONING OF PCDDs/Fs ON MSWI FLY ASH AND THE EFFECTS OF SAMPLING

Introduction 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 gasphase 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 gasphase 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 (MSWI) 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.