Gaussian model for emission rate measurement of heated plumes using hyperspectral data

Grauer, Samuel J.; Conrad, Bradley; Miguel, Rodrigo Bernardi; Daun, Kyle J.

doi:10.1016/j.jqsrt.2017.11.005

Cited by 16 publications

(10 citation statements)

References 33 publications

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“…Importantly, it is not critical to accurately reconstruct the spatial distribution of gas temperature and H2O volume fraction along the path; the column distribution simply allows for meaningful path-average values to be calculated from an unknown distribution. Preliminary simulations also showed the column distribution approach to be more stable and accurate, at least in this application, than the Gaussian distribution approach proposed by Grauer et al (2018).…”

Section: H2o Detection -Tunable Diode Laser Absorption Spectroscopy (mentioning

confidence: 83%

Species Correlation Measurements in Turbulent Flare Plumes: Considerations for Field Measurements

Seymour¹,

Johnson²

2021

Preprint

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Abstract. Field measurement of flare emissions in turbulent flare plumes is an important and complex challenge. The simplest approaches necessarily assume that combustion species are spatially and/or temporally correlated in the plume, such that simple species ratios can be used to close a carbon balance to calculate species emission rates (i.e. emission factors) and flare conversion efficiency. This study examines the veracity of this assumption and the associated implications for measurement uncertainty. A novel tunable diode laser absorption spectroscopy (TDLAS) system is used to measure the correlation between H2O and black carbon (BC) volume fractions in the plumes of a vertical, turbulent, non-premixed, buoyancy-driven lab-scale gas flare. Experiments reveal that instantaneous, path-averaged concentrations of BC and H2O can vary independently and are not necessarily well-correlated over short time intervals. The scatter in the BC / H2O ratio along a path through the plume was well beyond that which could be attributed to measurement uncertainty and was asymmetrically distributed about the mean. Consistent with previous field observations, this positive skewness toward higher BC / H2O ratios implies short, localized, and infrequent bursts of high BC production, that are not well-correlated with H2O. This demonstrates that the common assumption of fixed species ratios is not universally valid, and measurements based on limited samples, short sampling times, and/or limited spatial coverage of the plume could be subject to potentially large added uncertainty. For BC emission measurements, the positive skewness of the BC / H2O ratio also suggests that results from small numbers of samples are more likely to be biased low. However, a bootstrap analysis of the results shows how these issues should be easily avoidable with sufficient sample size and provides initial guidance for creating sampling protocols for future field measurements using analogous path-averaged techniques.

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Section: H2o Detection -Tunable Diode Laser Absorption Spectroscopy (mentioning

confidence: 83%

Species Correlation Measurements in Turbulent Flare Plumes: Considerations for Field Measurements

Seymour¹,

Johnson²

2021

Preprint

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“…This may be less of an issue in full-sized aircraft sampling approaches (e.g. Gvakharia et al, 2017;Weyant et al, 2016), which would be expected to measure a much larger volume than the presented technique; however, the required data averaging to obtain representative results will depend on the relative plume volumes sampled at that downstream measurement position, sampling duration, and how the technique interrogates the plume (e.g. stationary point or line-of-sight, transect downwind or crosswind, among others).…”

Section: Implications For Field Measurementsmentioning

confidence: 99%

“…The relative species concentrations are then used to close a molar-or mass-balance of carbon to determine the desired flare performance metrics (e.g. Gvakharia et al, 2017;Herndon et al, 2012;Pohl et al, 1986;Strosher, 2000;Weyant et al, 2016). Non-intrusive techniques typically employ Fourier transform infrared spectroscopy (FTIR, both active and passive) to measure column concentrations of each species along a line-of-sight (LOS) through the plume (e.g.…”

Section: Introductionmentioning

confidence: 99%

Species correlation measurements in turbulent flare plumes: considerations for field measurements

Seymour

Johnson

2021

Atmos. Meas. Tech.

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Abstract. Field measurement of flare emissions in turbulent flare plumes is an important and complex challenge. Incomplete combustion from these processes results in emissions of black carbon, unburnt fuels (methane), CO2, and other pollutants. Many field measurement approaches necessarily assume that combustion species are spatially and/or temporally correlated in the plume, such that simple species ratios can be used to close a carbon balance to calculate species emission factors and flare conversion efficiency. This study examines the veracity of this assumption and the associated implications for measurement uncertainty. A novel tunable diode laser absorption spectroscopy (TDLAS) system is used to measure the correlation between H2O and black carbon (BC) volume fractions in the plumes of a vertical, turbulent, non-premixed, buoyancy-driven lab-scale gas flare. Experiments reveal that instantaneous, path-averaged concentrations of BC and H2O can vary independently and are not necessarily well correlated over short time intervals. The scatter in the BC/H2O ratio along a path through the plume was well beyond that which could be attributed to measurement uncertainty and was asymmetrically distributed about the mean. Consistent with previous field observations, this positive skewness toward higher BC/H2O ratios implies short, localized, and infrequent bursts of high BC production that are not well correlated with H2O. This demonstrates that the common assumption of fixed species ratios is not universally valid, and measurements based on limited samples, short sampling times, and/or limited spatial coverage of the plume could be subject to potentially large added uncertainty. For BC emission measurements, the positive skewness of the BC/H2O ratio also suggests that results from small numbers of samples are more likely to be biased low. However, a bootstrap analysis of the results shows how these issues can be avoided with sufficient sample size and provides initial guidance for creating sampling protocols for future field measurements using analogous path-averaged techniques.

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“…In their work, the plume temperature and species concentrations are assumed to be homogeneous along each LOS in order to simplify the spectroscopic model. However, Grauer et al [17] and Miguel et al [18] used CFD simulations to demonstrate that Gaussian distributions are more appropriate in the case of flare plumes. Miguel et al [18] also conducted several proof-of-concept measurements on lab scale heated vents and a lab-scale steam and air-assist flare.…”

Section: Introductionmentioning

confidence: 99%

Quantifying flare combustion efficiency using an imaging Fourier transform spectrometer

Lapeyre,

Miguel,

Nagorski

et al. 2024

Journal of the Air & Waste Management Association

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Mid-wavelength infrared (MWIR) imaging Fourier transform spectrometers (IFTSs) are a promising technology for measuring flare combustion efficiency (CE), defined as the fraction of carbon supplied to the flare as fuel that is converted into carbon dioxide. These devices generate spectrally-resolved intensity images of the flare plume, which may then be used to infer column densities of relevant species along each pixel line-of-sight. In parallel, a 2D projected velocity field may be inferred from the apparent motion of flow features between successive images. Finally, the column densities and velocity field are combined to estimate the mass flow rates for the species needed to calculate the CE. Since the MWIR IFTS can measure all carbon-containing species in the flare plume, it is possible to measure CE without knowing the fuel flow rate, which is important for fenceline measurements.This work demonstrates this approach on a laboratory heated vent, and then deploys the technique on two working flares: a combustor burning natural gas at a known rate, and a steamassisted flare at a petrochemical refinery. Analysis of the IFTS data highlights the potential of this approach, but also areas for future development to transform this approach into a reliable technique for quantifying flare CE.

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Gaussian model for emission rate measurement of heated plumes using hyperspectral data

Cited by 16 publications

References 33 publications

Species Correlation Measurements in Turbulent Flare Plumes: Considerations for Field Measurements

Species Correlation Measurements in Turbulent Flare Plumes: Considerations for Field Measurements

Species correlation measurements in turbulent flare plumes: considerations for field measurements

Quantifying flare combustion efficiency using an imaging Fourier transform spectrometer

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