An uncertainty-based protocol for the setup and measurement of soot–black carbon emissions from gas flares using sky-LOSA

Abstract

Abstract. Gas flaring is an important source of atmospheric soot–black carbon, especially in sensitive Arctic regions. However, emissions have traditionally been challenging to measure and remain poorly characterized, confounding international reporting requirements and adding uncertainty to climate models. The sky-LOSA optical measurement technique has emerged as a powerful means to quantify flare black carbon emissions in the field, but broader adoption has been hampered by the complexity of its deployment, where decisions during setup in the field can have profound, non-linear impacts on achievable measurement uncertainties. To address this challenge, this paper presents a prescriptive measurement protocol and associated open-source software tool that simplify acquisition of sky-LOSA data in the field. Leveraging a comprehensive Monte Carlo-based general uncertainty analysis (GUA) to predict measurement uncertainties over the entire breadth of possible measurement conditions, general heuristics are identified to guide a sky-LOSA user toward optimal data collection. These are further extended in the open-source software utility, SetupSkyLOSA, which interprets the GUA results to provide detailed guidance for any specific combination of location, date–time, and flare, plume, and ambient conditions. Finally, a case study of a sky-LOSA measurement at an oil and gas facility in Mexico is used to demonstrate the utility of the software tool, where potentially small regions of optimal instrument setup are easily and quickly identified. It is hoped that this work will help increase the accessibility of the sky-LOSA technique and ultimately the availability of field measurement data for flare black carbon emissions.

Quantifying flare combustion efficiency using an imaging Fourier transform spectrometer

“…While the approach focused on calculating CE, it may also be used to quantify emissions of other types of flare emissions, including black carbon [27] and sulphur dioxide [28]. The combined spectral and spatial resolution afforded by the IFTS is particularly well-suited in cases where the species may be distributed heterogeneously in the flare plume and in cases where the species present in the plume may be unknown or uncertain.…”

“…A second source of model error comes from the use of intensity-weighted projected velocities obtained from the optical flow algorithm. When the intensity variations are caused by the absorption of background radiation it can be shown that the projected velocity field is a "massweighted velocity", which is appropriate for calculating a mass-flow rate [30,27]. In this case, 31 however, the intensity variations are due to coupled fluctuations in local temperature and concentration, and the resulting velocity field may not be mass-weighted.…”