QCL-Based perfluorocarbon emission monitoring

Abstract

Periodic, short-term, extractive sampling with Fourier transform infrared (FTIR) spectrometers is often employed to measure perfluorocarbon (PFC) emissions at aluminum smelters. FTIRs have been routinely deployed by Alcoa to measure tetrafluoromethane (CF4) and hexafluoroethane (C2F6) gases during 2-4 week sampling campaigns at smelters worldwide. In conjunction with plant process logs, the data collected from these short-duration measurements are used to estimate production- Normalized plant-specific PFC emission factors. Quantum cascade lasers (QCL) have recently become available for the mid-infrared monitoring of air pollutants. QCL-based, purpose-designed measurement systems could facilitate long-term in-situ stack measurement of CF4 at one or a few representative dry scrubber exhaust stacks. This paper discusses paired in-plant measurements by FTIR and QCL-based optical systems employed to develop future QCL measurement platforms and optimize the latter for long term stack PFC monitoring.