1 research outputs found
Direct measurement of volatile organic compound emissions from industrial flares using real-time online techniques: Proton Transfer Reaction Mass Spectrometry and Tunable Infrared Laser Differential Absorption Spectroscopy
During the 2010 Comprehensive Flare Study a suite of
analytical
instrumentation was employed to monitor and quantify in real-time
the volatile organic compound (VOC) emissions emanating from an industrial
chemical process flare burning either propene/natural gas or propane/natural
gas. To our knowledge this represents the first time the VOC composition
has been directly measured as a function of flare efficiency on an
operational full-scale flare. This compositional information was obtained
using a suite of proton-transfer-reaction mass spectrometers (PTR-MS)
and quantum cascade laser tunable infrared differential absorption
spectrometers (QCL-TILDAS) to measure the unburned fuel and associated
combustion byproducts. Methane, ethyne, ethene, and formaldehyde were
measured using the QC-TILDAS. Propene, acetaldehyde, methanol, benzene,
acrolein, and the sum of the C<sub>3</sub>H<sub>6</sub>O isomers were
measured with the PTR-MS. A second PTR-MS equipped with a gas chromatograph
(GC) was operated in parallel and was used to verify the identity
of the neutral components that were responsible for producing the
ions monitored with the first PTR-MS. Additional components including
1,3-butadiene and C<sub>3</sub>H<sub>4</sub> (propyne or allene) were
identified using the GC/PTR-MS. The propene concentrations derived
from the PTR-MS were found to agree with measurements made using a
conventional GC with a flame ionization detector (FID). The VOC product
(excludes fuel components) speciation profile is more dependent on
fuel composition, propene versus propane, than on flare type, air-assisted
versus steam-assisted, and is essentially constant with respect to
combustion efficiency for combustion efficiencies >0.8. Propane
flares
produce more alkenes with ethene and propene accounting for approximately
80% (per carbon basis) of the VOC combustion product. The propene
partial combustion product profile was observed to contain relatively
more oxygenated material where formaldehyde and acetaldehyde are major
contributors and account for ∼20 - 25% of VOC product carbon.
Steam-assisted flares produce less ethyne and benzene than air-assisted
flares. This observation is consistent with the understanding that
steam assisted flares are more efficient at reducing soot, which is
formed via the same reaction mechanisms that form benzene and ethyne