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Emissions of nitrogen oxides from flares operating at low flow conditions / Vincent M. Torres in Industrial & engineering chemistry research, Vol. 51 N° 39 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12600-12605 Titre : Emissions of nitrogen oxides from flares operating at low flow conditions Type de document : texte imprimé Auteurs : Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; Ezra Wood, Auteur Année de publication : 2012 Article en page(s) : pp. 12600-12605 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Nitrogen  Oxides Résumé : Full scale flare tests have been conducted to test the impacts of flare operating conditions on the fraction of flared gases that are converted to carbon dioxide and water (combustion efficiency, CE) for flares combusting low heating value gases (350–600 BTU/scf) at low flow rates (0.1–0.25% of maximum flow). Flares produce lower flame temperatures when operating with low heating value gases at low combustion efficiencies than when operating with high heating value gases at high combustion efficiencies. This leads to reduced formation of nitrogen oxides (NOx) in the flame. For a series of tests conducted under low flow conditions, with low heating value gases, NOx emission factors ranged between 10 and 120% of the NOx emission factor reported in AP-42. Emissions of NOx were highest for air assisted flares operating at high CE and lowest for steam assisted flares operating at low CE. In general, emissions were lower in steam assisted flare tests than in air assisted flare tests conducted under similar conditions. Photochemical modeling simulations indicated that these reductions in NOx emissions had relatively small impacts on the ozone formation potential of flares operating at low CE. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300179x [article] Emissions of nitrogen oxides from flares operating at low flow conditions [texte imprimé] / Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; Ezra Wood, Auteur . - 2012 . - pp. 12600-12605. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12600-12605 Mots-clés : Nitrogen  Oxides Résumé : Full scale flare tests have been conducted to test the impacts of flare operating conditions on the fraction of flared gases that are converted to carbon dioxide and water (combustion efficiency, CE) for flares combusting low heating value gases (350–600 BTU/scf) at low flow rates (0.1–0.25% of maximum flow). Flares produce lower flame temperatures when operating with low heating value gases at low combustion efficiencies than when operating with high heating value gases at high combustion efficiencies. This leads to reduced formation of nitrogen oxides (NOx) in the flame. For a series of tests conducted under low flow conditions, with low heating value gases, NOx emission factors ranged between 10 and 120% of the NOx emission factor reported in AP-42. Emissions of NOx were highest for air assisted flares operating at high CE and lowest for steam assisted flares operating at low CE. In general, emissions were lower in steam assisted flare tests than in air assisted flare tests conducted under similar conditions. Photochemical modeling simulations indicated that these reductions in NOx emissions had relatively small impacts on the ozone formation potential of flares operating at low CE. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300179x

Impacts of air-assist flare blower configurations on flaring emissions / Fahad M. Al Fadhli in Industrial & engineering chemistry research, Vol. 51 N° 39 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12606-12610 Titre : Impacts of air-assist flare blower configurations on flaring emissions Type de document : texte imprimé Auteurs : Fahad M. Al Fadhli, Auteur ; Vincent M. Torres, Auteur ; David T. Allen, Auteur Année de publication : 2012 Article en page(s) : pp. 12606-12610 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Air  assist  flare Résumé : Air-assisted flares, operating under low flow conditions (<1% of maximum flow) with low BTU gases, have relatively narrow bands of air-to-vent gas ratios that can achieve destruction and removal efficiencies (DREs, fraction of waste gases destroyed by complete and incomplete combustion) greater than 98%. If blower configurations are not able to operate within these narrow bands, emissions may be greater than those predicted based on 98% DRE, but if air-assist rates can be finely tuned, emissions much lower than those predicted assuming 98% DRE are achievable. This work examines the potential impact on emissions of using four different blower configurations (single fixed speed, dual fixed speed, single variable speed, and dual variable speed) on an air-assisted flare. Typical patterns of flare vent gas flow rates were obtained from hourly data on flared gas flow rates from Houston, Texas. The analyses indicate that flare emissions can be much greater (up to a factor of 40) than a base case assuming 98% DRE if single, fixed speed blower configurations are used. Conversely, flare emissions can be much lower than a base case assuming 98% DRE if air-assist rates can be closely matched to stoichiometric requirements. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3012209 [article] Impacts of air-assist flare blower configurations on flaring emissions [texte imprimé] / Fahad M. Al Fadhli, Auteur ; Vincent M. Torres, Auteur ; David T. Allen, Auteur . - 2012 . - pp. 12606-12610. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12606-12610 Mots-clés : Air  assist  flare Résumé : Air-assisted flares, operating under low flow conditions (<1% of maximum flow) with low BTU gases, have relatively narrow bands of air-to-vent gas ratios that can achieve destruction and removal efficiencies (DREs, fraction of waste gases destroyed by complete and incomplete combustion) greater than 98%. If blower configurations are not able to operate within these narrow bands, emissions may be greater than those predicted based on 98% DRE, but if air-assist rates can be finely tuned, emissions much lower than those predicted assuming 98% DRE are achievable. This work examines the potential impact on emissions of using four different blower configurations (single fixed speed, dual fixed speed, single variable speed, and dual variable speed) on an air-assisted flare. Typical patterns of flare vent gas flow rates were obtained from hourly data on flared gas flow rates from Houston, Texas. The analyses indicate that flare emissions can be much greater (up to a factor of 40) than a base case assuming 98% DRE if single, fixed speed blower configurations are used. Conversely, flare emissions can be much lower than a base case assuming 98% DRE if air-assist rates can be closely matched to stoichiometric requirements. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3012209

Industrial flare performance at low flow conditions. 1. / Vincent M. Torres in Industrial & engineering chemistry research, Vol. 51 N° 39 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12559–12568 Titre : Industrial flare performance at low flow conditions. 1. : Study overview Type de document : texte imprimé Auteurs : Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; Zach Kodesh, Auteur Année de publication : 2012 Article en page(s) : pp. 12559–12568 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Industrial  flare  Flow  conditions Résumé : A series of full-scale industrial flare tests were conducted at low flow and low BTU content of flared gases at an industrial test facility. Both a 24” diameter air-assisted flare with a flow capacity of 144,000 lb/h and a 36” steam-assisted flare with a flow capacity of 937,000 lb/h were employed in the testing. Flared gases were mixtures of natural gas, propylene, and nitrogen or natural gas, propane, and nitrogen. Natural gas to propane or propylene ratio was 1:4 by volume for all experiments. Nitrogen was used as a diluent to achieve the desired lower heating values (LHV) for the vent gas. The range of flared gas flow rates was 0.1% to 0.65% of the flare’s design capacity. Flare operation was characterized by measurements of flow rates to the flare, extractive measurements made of the vent gases fed to the flare, extractive measurements made at the end of the flare plume, and remote sensing measurements of the flare plume made by a variety of spectroscopic instruments. Destruction/removal efficiencies (DRE, fraction of vent gas reacted) of flared species were calculated based on the observed composition of the species in the plume. The tests demonstrated that destruction efficiencies for steam-assisted flares drop dramatically when combustion zone heating values fall below 250 BTU/scf. Air-assisted flares showed a linear drop in DRE as a function of air flow. While the primary focus of the measurements was on DRE, products of incomplete combustion were also measured. Dominant products of incomplete combustion were CO, ethylene, formaldehyde, acetylene, and acetaldehyde. CO represented approximately 24% to 80% (carbon basis) of the total products of incomplete combustion for DRE > 90%. While DREs of 98–99% were observed in some experiments, many operating conditions produced DREs of substantially less than 99%. Since prescribed methods for estimating emissions would have predicted 98–99% DRE for all the tests, some test conditions resulted in the production of flare emissions multiple times the value that would be calculated using the prescribed estimation methods. In practice, total emissions from flares will depend on both operating conditions and the duration of operation at the various operating conditions. ISSN : 1385-8947 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202674t [article] Industrial flare performance at low flow conditions. 1. : Study overview [texte imprimé] / Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; Zach Kodesh, Auteur . - 2012 . - pp. 12559–12568. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12559–12568 Mots-clés : Industrial  flare  Flow  conditions Résumé : A series of full-scale industrial flare tests were conducted at low flow and low BTU content of flared gases at an industrial test facility. Both a 24” diameter air-assisted flare with a flow capacity of 144,000 lb/h and a 36” steam-assisted flare with a flow capacity of 937,000 lb/h were employed in the testing. Flared gases were mixtures of natural gas, propylene, and nitrogen or natural gas, propane, and nitrogen. Natural gas to propane or propylene ratio was 1:4 by volume for all experiments. Nitrogen was used as a diluent to achieve the desired lower heating values (LHV) for the vent gas. The range of flared gas flow rates was 0.1% to 0.65% of the flare’s design capacity. Flare operation was characterized by measurements of flow rates to the flare, extractive measurements made of the vent gases fed to the flare, extractive measurements made at the end of the flare plume, and remote sensing measurements of the flare plume made by a variety of spectroscopic instruments. Destruction/removal efficiencies (DRE, fraction of vent gas reacted) of flared species were calculated based on the observed composition of the species in the plume. The tests demonstrated that destruction efficiencies for steam-assisted flares drop dramatically when combustion zone heating values fall below 250 BTU/scf. Air-assisted flares showed a linear drop in DRE as a function of air flow. While the primary focus of the measurements was on DRE, products of incomplete combustion were also measured. Dominant products of incomplete combustion were CO, ethylene, formaldehyde, acetylene, and acetaldehyde. CO represented approximately 24% to 80% (carbon basis) of the total products of incomplete combustion for DRE > 90%. While DREs of 98–99% were observed in some experiments, many operating conditions produced DREs of substantially less than 99%. Since prescribed methods for estimating emissions would have predicted 98–99% DRE for all the tests, some test conditions resulted in the production of flare emissions multiple times the value that would be calculated using the prescribed estimation methods. In practice, total emissions from flares will depend on both operating conditions and the duration of operation at the various operating conditions. ISSN : 1385-8947 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202674t

Industrial flare performance at low flow conditions. 2. / Vincent M. Torres in Industrial & engineering chemistry research, Vol. 51 N° 39 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12569–12576 Titre : Industrial flare performance at low flow conditions. 2. : Steam- and air-assisted flares Type de document : texte imprimé Auteurs : Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; David T. Allen, Auteur Année de publication : 2012 Article en page(s) : pp. 12569–12576 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Industrial  flare  Steam Résumé : Full-scale tests of steam- and air-assisted industrial flares were conducted using low BTU content (lower heating value) vent gases at low flow rates. A 36″ diameter steam-assisted flare with a flow capacity of 937,000 lb/h and a 24″ diameter air-assisted flare with a flow capacity of 144,000 pounds per hour were operated with mixtures of natural gas, propylene, and nitrogen or natural gas, propane, and nitrogen at flow rates less than 1% of maximum flow. Combustion efficiency (percentage of the flared gases converted to carbon dioxide and water) ranged from less than 50% to more than 99%. For the steam-assisted flare, combustion efficiency (CE) at low steam-to-vent gas flow ratios (0.5–1.0) was typically in excess of 95%. CE would gradually decrease as steam-to-vent gas ratio increased, to a point, after which CE would decrease dramatically. The steam-to-vent gas ratio at which CE would decrease dramatically depended on the heating value of the vent gas and the position of the steam injection. Higher heating values of the vent gas (600 vs 350 BTU/scf) and the minimization of steam coinjected with the vent gas, rather than injected at the flare tip, promoted higher CE. For the air-assisted flare, CE at low air assist rates (<30–50 times the vent gas flow rate) was typically above 90%. The CE decreased linearly with increasing air assist to vent gas ratio and did not exhibit the rapid decrease exhibited by the steam-assisted flare. Combustion efficiencies for vent gases with higher heating values (600 BTU/scf versus 350 BTU/scf) decreased more slowly in the air assisted flare. For both the steam- and air-assisted flares, the composition of the vent gas (propane vs propylene) had a much smaller effect on combustion characteristics than steam or air injection and vent gas heating value. Products of incomplete combustion were dominated by CO; other significant species included acetylene, ethylene, formaldehyde, acetaldehyde, and acrolein. The effect of wind speed on CE was estimated to be less than 2.5% of the CE, over the range of wind speeds 0–16 mph. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202675f [article] Industrial flare performance at low flow conditions. 2. : Steam- and air-assisted flares [texte imprimé] / Vincent M. Torres, Auteur ; Scott Herndon, Auteur ; David T. Allen, Auteur . - 2012 . - pp. 12569–12576. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12569–12576 Mots-clés : Industrial  flare  Steam Résumé : Full-scale tests of steam- and air-assisted industrial flares were conducted using low BTU content (lower heating value) vent gases at low flow rates. A 36″ diameter steam-assisted flare with a flow capacity of 937,000 lb/h and a 24″ diameter air-assisted flare with a flow capacity of 144,000 pounds per hour were operated with mixtures of natural gas, propylene, and nitrogen or natural gas, propane, and nitrogen at flow rates less than 1% of maximum flow. Combustion efficiency (percentage of the flared gases converted to carbon dioxide and water) ranged from less than 50% to more than 99%. For the steam-assisted flare, combustion efficiency (CE) at low steam-to-vent gas flow ratios (0.5–1.0) was typically in excess of 95%. CE would gradually decrease as steam-to-vent gas ratio increased, to a point, after which CE would decrease dramatically. The steam-to-vent gas ratio at which CE would decrease dramatically depended on the heating value of the vent gas and the position of the steam injection. Higher heating values of the vent gas (600 vs 350 BTU/scf) and the minimization of steam coinjected with the vent gas, rather than injected at the flare tip, promoted higher CE. For the air-assisted flare, CE at low air assist rates (<30–50 times the vent gas flow rate) was typically above 90%. The CE decreased linearly with increasing air assist to vent gas ratio and did not exhibit the rapid decrease exhibited by the steam-assisted flare. Combustion efficiencies for vent gases with higher heating values (600 BTU/scf versus 350 BTU/scf) decreased more slowly in the air assisted flare. For both the steam- and air-assisted flares, the composition of the vent gas (propane vs propylene) had a much smaller effect on combustion characteristics than steam or air injection and vent gas heating value. Products of incomplete combustion were dominated by CO; other significant species included acetylene, ethylene, formaldehyde, acetaldehyde, and acrolein. The effect of wind speed on CE was estimated to be less than 2.5% of the CE, over the range of wind speeds 0–16 mph. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202675f