Observations and predictions of jet diffusion flame behaviour

Leahey, Douglas M.; Schroeder, Michael B.

doi:10.1016/0004-6981(87)90073-4

Cited by 6 publications

(19 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model is based on the assumption, following the theoretical findings of Escudier 17 and observational results of Becker et al, 18 that the effects of buoyancy forces on flame behavior are negligible. Observational assessments have shown that predictions of the Leahey and Schroeder model agree well with actual flame dimensions for a sour gas flare; 8,19 for methane, propane, ethylene, and butane flames observed in a wind tunnel; 20 and for a very large emergency flare. 21 One-to-one correlations between predicted and observed flame parameters were ~0.90.…”

Section: Introductionmentioning

confidence: 90%

See 1 more Smart Citation

Theoretical and Observational Assessments of Flare Efficiencies

Leahey

Preston

Strosher³

2001

Journal of the Air & Waste Management Association

Self Cite

View full text Add to dashboard Cite

Flaring of waste gases is a common practice in the processing of hydrocarbon (HC) materials. It is assumed that flaring achieves complete combustion with relatively innocuous byproducts such as CO 2 and H 2 O. However, flaring is rarely successful in the attainment of complete combustion, because entrainment of air into the region of combusting gases restricts flame sizes to less than optimum values. The resulting flames are too small to dissipate the amount of heat associated with 100% combustion efficiency.Equations were employed to estimate flame lengths, areas, and volumes as functions of flare stack exit velocity, stoichiometric mixing ratio, and wind speed. Heats released as part of the combustion process were then estimated from a knowledge of the flame dimensions together with an assumed flame temperature of 1200 K. Combustion efficiencies were subsequently obtained by taking the ratio of estimated actual heat release values to those associated with 100% complete combustion.Results of the calculations showed that combustion efficiencies decreased rapidly as wind speed increased from 1 to 6 m/sec. As wind speeds increased beyond 6 m/sec, IMPLICATIONS Flares are used extensively to dispose of gaseous wastes. The usual assumption is that combustion processes associated with flares efficiently convert HCs and sulfur compounds to relatively innocuous gases such as CO 2 , SO 2 , and H 2 O. It has been shown, however, that these processes can be efficient only at low wind speeds because the size of the flare flame, which is an indicator of flame efficiency, decreases with increasing wind speed. Therefore, the flaring process could routinely result, during periods of moderate to high wind speeds, in appreciable quantities of products of incomplete combustion such as anthracene and benzo(a)pyrene, which can have adverse implications with respect to air quality. combustion efficiencies tended to level off at values between 10 and 15%. Propane and ethane tend to burn more efficiently than do methane or hydrogen sulfide because of their lower stoichiometric mixing ratios.Results of theoretical predictions were compared to nine values of local combustion efficiencies obtained as part of an observational study into flaring activity conducted by the Alberta Research Council (ARC). All values were obtained during wind speed conditions of less than 4 m/sec. There was generally good agreement between predicted and observed values. The mean and standard deviation of observed combustion efficiencies were 68 ± 7%. Comparable predicted values were 69 ± 7%.

show abstract

Section: Introductionmentioning

confidence: 90%

“…Equations for flame dimensions (downwind extent, area, volume) as presented by Leahey et al 8 and Leahey and Schroeder 19,20 are as follows:…”

Section: Appendixmentioning

confidence: 99%

Theoretical and Observational Assessments of Flare Efficiencies

Leahey

Preston

Strosher³

2001

Journal of the Air & Waste Management Association

Self Cite

View full text Add to dashboard Cite

show abstract

“…f mix increases with increasing

\frac{U_{atm}}{{(U_{sc})}_{s = 0}}

. To model f mix , different‐structured equations were fitted to the experimental data studied by Leahey and Schroeder . After comparing results obtained with the equations, the following exponential equation is found to yield the most accurate results:

f_{mix} = 0.0802 \exp true(normal2.7786 \frac{U_{normalatm}}{{false(U_{normalsc} false)}_{s = 0}} true)

Figures compare model results of the flame length and the flame angle with the measured data from Leahey and Schroeder .…”

Section: Preliminary Model Calculationsmentioning

confidence: 99%

“…Flame angle is defined as the angle between the line connecting the flame base with the flame tip and the vertical. Data points that were deemed invalid by Leahey and Schroeder are indicated with a separate marker in the charts.…”

Section: Preliminary Model Calculationsmentioning

confidence: 99%

“…In another study, Steward developed a theoretical mathematical model for flare size, in which the flame length is a function of various air and fuel properties and temperature, as well as the stack exit radius, flare gas heat release, and stoichiometric air‐to‐fuel ratio. Some other equations for flare dimensions (downwind extent, area, and volume) were presented by Leahey et al and Leahey and Schroeder …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simplified flare combustion model for flare plume rise calculations

Rahnama

Visscher

2016

Can J Chem Eng

View full text Add to dashboard Cite

The dispersion of plumes released from stacks depends on wind speed, plume emission rate, stack height, and other meteorological and stack variables. Plume rise is an important aspect of plume dispersion because it increases the apparent release height, which leads to lower ground-level concentrations. Plume rise linked with flare combustion has received only minimal attention in the literature to date, despite its importance. This study develops a numerical model of plume rise with flare combustion based on material, heat, mass, and momentum balances. The basis of the model is a numerical plume rise model used in CALPUFF to model plume rise of large buoyant area sources, and is also used in PRIME (plume rise model enhancements), which models building downwash. The proposed model considers the reaction kinetics. The competition between CH 4 and CO combustion causes a modification of the temperature profile of up to 3 % in comparison with an instantaneous reaction model. Moreover, emissivity, which plays an important role in the heat conservation equations but which was only parameterized in an earlier work, is calculated more directly to increase the accuracy of the model. It was found that soot is the main contributor to flame emissivity. Finally, the air dispersion model CALPUFF was run according to the proposed flare model and an empirical flare model by Beychok to compare results of the models. This new flare method is sufficiently simple to be embedded into air dispersion modelling software such as CALPUFF.

show abstract

References

2012

Lees' Loss Prevention in the Process Industries

View full text Add to dashboard Cite

Observations and predictions of jet diffusion flame behaviour

Cited by 6 publications

References 17 publications

Theoretical and Observational Assessments of Flare Efficiencies

Theoretical and Observational Assessments of Flare Efficiencies

Simplified flare combustion model for flare plume rise calculations

References

Contact Info

Product

Resources

About