Combustion mechanism development and CFD simulation for the prediction of soot emission during flaring

Abstract

Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data.

Key words： flare; soot emission; combustion mechanism; CFD simulation

References

1 Bond T C, Doherty S J, Fahey D W, Forster P M, Berntsen T, DeAngelo B J, Flanner M G, Ghan S, Kärcher B, Koch D, Kinne S, Kondo Y, Quinn P K, Sarofim M C, Schultz M G, Schulz M, Venkataraman C, Zhang H, Zhang S, Bellouin N, Guttikunda S K, Hopke P K, Jacobson M Z, Kaiser J W, Klimont Z, Lohmann U, Schwarz J P, Shindell D, Storelvmo T, Warren S G, Zender C S. Bounding the role of black carbon in the climate system: A scientific assessment. Journal of Geophysical Research, D, Atmospheres, 2013, 118(11): 5380–5552

2 Elvidge C D, Ziskin D, Baugh K E, Tuttle B T, Ghosh T, Pack D W, Erwin E H, Zhizhin M. A fifteen year record of global natural gas flaring derived from satellite data. Energies, 2009, 2(3): 595–622

3 U.S. EPA. 2009 Final Report: Integrated Science Assessment for Particulate Matter. 2009

4 United States Government Code of Federal Regulations‒Standards of Performance for New Stationary Sources, General Control Device and Work Practice Requirements, 40CFR § 60.18. Available at: http://edocket.access.gpo.gov/cfr_2009/julqtr/pdf/40cfr60.18.pdf (<Date>accessed in April, 2016</Date>)

5 U.S. EPA. 40 CFR Ch. I (7–1–09 Edition), Pt. 60, App. A–4, Meth. 9.: Method 9-Visual determination of the opacity of emissions from stationary sources. Available at: https://www.gpo.gov/fdsys/pkg/CFR-2010-title40-vol7/pdf/CFR-2010-title40-vol7-part60-appA-id11.pdf (<Date>accessed in April, 2016</Date>)

6 U.S. EPA Office of Air Quality Planning and Standards (OAQPS). Parameters for properly designed and operated flares, report for flare review panel, 2012. Available at: https://www3.epa.gov/airtoxics/flare/2012flaretechreport.pdf (<Date>accessed in April, 2016</Date>)

7 Fry C R, Coburn J, International R T I. Peer review of “Parameters for properly designed and operated flares”, 2012. Available at: https://www3.epa.gov/airtoxics/flare/2012flarepeerreviewmemo.pdf (<Date>accessed in April, 2016</Date>)

8 Allen D T, Torres V M. 2010 TCEQ Flare Study Final Report. The University of Texas at Austin, The Center for Energy and Environmental Resources, TCEQ PGA No. 582-8-86245-FY09-04 and Task order No. UTA10-000924-LOAT-RP9, 2011

9 Barlow R S, Frank J H. Summary Twelfth International Workshop Measurement and Computation of Turbulent Flames (TNF12).<Date>July 31–August 2</Date>, 2014, Pleasanton, California, USA

10 Action R. Particular Matler (PM) Pollution. Available at: http://www.epa.gov/airquality/particlepollution/actions.html (<Date>accessed in April, 2016</Date>)

11 Stohl A, Klimont Z, Eckhardt S, Kupiainen K, Shevchenko V P, Kopeikin V M, Novigatsky A N. Black carbon in the Arctic: The underestimated role of gas flaring and residential combustion emissions. Atmospheric Chemistry and Physics, 2013, 13(17): 8833–8855

12 Seinfeld J H, Pandis S N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. Environment. Science and Policy for Sustainable Development, 1988, 40(7): 26

13 Qin Z, Yang H, Gardiner W C Jr. Measurement and modeling of shock-tube ignition delay for propene. Combustion and Flame, 2001, 124(1-2): 246–254

14 Wang H. A Comprehensive Kinetic Model of Ethylene and Acetylene Oxidation at High Temperatures. Dissertation for the Doctoral Degree. Delaware: University of Delaware, 1998

15 McDaniel M, Tichenor B A. Flare Efficiency Study. US Environmental Protection Agency, Industrial Environmental Research Laboratory, 1983

16 Seinfeld J H, Pandis S N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. 2nd edition. New Jersey: John Wiley & Sons, 2006

17 Current P M. _2.5 levels — soot, dust, and smoke in your metro area. Available at: http://www.tceq.state.tx.us/cgi-bin/compliance/monops/texas_pm25.pl (<Date>accessed in April, 2016</Date>)

18 Fine Particulate Matter National Ambient Air Quality Standards. State Implementation Plan Requirements; Proposed Rule. Available at: https://www.gpo.gov/fdsys/pkg/FR-2015-03-23/pdf/2015-06138.pdf (<Date>accessed in April, 2016</Date>)

19 Kleiveland R N. Modelling of soot formation and oxidation in turbulent diffusion flames. Dissertation for the Doctoral Degree. Trondheim: Norwegian University of Science and Technology, 2005

20 2013 Emissions Inventory Guidelines. Available at: https://www.tceq.texas.gov/assets/public/comm_exec/pubs/rg/rg360/rg36013/TOC-covers.pdf (<Date>accessed in April, 2016</Date>)

21 Fact sheet proposed petroleum refinery risk and technology review and new source performance standards. Available at: https://www3.epa.gov/airtoxics/petrefine/20140515factsheet.pdf (<Date>accessed in April, 2016</Date>)

22 EPA’s strategy for reducing methane and ozone-forming pollution from the oil and natural gas industry. Available at: https://www3.epa.gov/airquality/oilandgas/pdfs/20150114fs.pdf (<Date>accessed in April, 2016</Date>)

23 EPA. 40 CFR Parts 60 and 63. Petroleum Refinery Sector Risk and Technology Review and New Source Performance Standards. Available at: https://www3.epa.gov/airtoxics/petrefine/20140515fr.pdf (<Date>accessed in April, 2016</Date>)

24 Guide, ANSYS FLUENT USER. Release 14.5, ANSYS. Inc., 2012

25 Singh J, Patterson R I A, Kraft M, Wang H. Numerical simulation and sensitivity analysis of detailed soot particle size distribution in laminar premixed ethylene flames. Combustion and Flame, 2006, 145(1-2): 117–127

26 Zhao B, Yang Z, Johnston M V, Wang H, Wexler A S, Balthasar M, Kraft M. Measurement and numerical simulation of soot particle size distribution functions in a laminar premixed ethylene-oxygen-argon flame. Combustion and Flame, 2003, 133(1-2): 173–188

27 Richter H, Howard J B. Formation of polycyclic aromatic hydrocarbons and their growth to soot—A review of chemical reaction pathways. Progress in Energy and Combustion Science, 2000, 26(4-6): 565–608

28 Frenklach M. Reaction mechanism of soot formation in flames. Physical Chemistry Chemical Physics, 2002, 4(11): 2028–2037

29 Lautenbergera C W, de Ris J L, Dembsey N A, Barnett J R, Baum H R. A simplified model for soot formation and oxidation in CFD simulation of non-premixed hydrocarbon flames. Fire Safety Journal, 2005, 40(2): 141–176

30 Colket M B, Hall R J, Sangiovanni J J, Seery D J. The Determination of Rate-Limiting Steps during Soot Formation. No. UTRC89-13 , United Technologies Research Center East Hartford CT, 1989, C-2–C-23

31 Frenklach M, Clary D W, Jr Gardiner W C, Stein S E. Detailed kinetic modeling of soot formation in shock-tube pyrolysis of acetylene. Symposium (International) on Combustion, 1985, 20(1): 887–901

32 Frenklach M, Clary D W, Jr Gardiner W C, Stein S E. Effect of fuel structure on pathways to soot. Symposium (International) on Combustion, 1988, 21(1): 1067–1076

33 Melius C F, Colvin M E, Marinov N M, Pit W J, Senkan S M. Reaction mechanisms in aromatic hydrocarbon formation involving the C5H5 cyclopentadienyl moiety. Symposium (International) on Combustion, 1996, 26(1): 685–692

34 Frenklach M. Reaction mechanism of soot formation in flames. Physical Chemistry Chemical Physics, 2002, 4(11): 2028–2037

35 Winans R E, Tomczyk N A, Hunt J E, Solum M S, Pugmire R J, Jiang Y J, Fletcher T H. Model compound study of the pathways for aromatic hydrocarbon formation in soot. Energy & Fuels, 2007, 21(5): 2584–2593

36 Fenklach M, Wang H. Aromatics growth beyond the first ring and the nucleation of soot particles. Divsion of Fuel Chemistry, 1991, 36: 1509

37 Miller J A, Kee R J, Westbrook C K. Chemical kinetics and combustion modeling. Annual Review of Physical Chemistry, 1990, 41(1): 345–387

38 Miller J A, Melius C F. Kinetic and thermodynamic issues in the formation of aromatic compounds in flames of aliphatic fuels. Combustion and Flame, 1992, 91(1): 21–39

39 Alexiou A, Williams A, Abdalla A Y. A shock-tube investigation of soot formation form toluene/methanol mixtures. In abstracts of papers of the American Chemical Society. Washington, DC: American Chemical Society, 1991, 202, 113

40 Lou H H, Martin C B, Chen D, Li X, Li K, Vaid H, Kumar A T, Singh K D, Bean D P Jr. A reduced reaction mechanism for the simulation in ethylene flare combustion. Clean Technologies and Environmental Policy, 2012, 14(2): 229–239

41 Wang H, You X Q, Joshi A V, Davis S G, Laskin A, Egolfopoulos F, Law C K. USC Mech Version II. High-temperature combustion reaction model of H₂/CO/C1-C4 Compounds. http://ignis.usc.edu/USC_Mech_II.htm<Date>(accessed in May, 2007)</Date>

42 Davis S G, Law C K. Determination of and fuel structure effects on Laminar flame speeds of C1 to C8 hydrocarbons. Combustion Science and Technology, 1998, 140(1-6): 427–449

43 Vagelopoulos C M, Egolfopoulos F N, Law C K. Further considerations on the determination of Laminar flame speeds with the counterflow twin-flame technique. Symposium (International) on Combustion, 1994, 25(1): 1341–1347

44 Zhu D L, Jomaas G, Zheng X L, Law C K. Experimental determination of counterflow ignition temperatures and laminar flame speeds of C2-C3 hydrocarbons at atmospheric and elevated pressures. Proceedings of the Combustion Institute, 2005, 30(1): 193–200

45 Heghes C I. C1-C4 Hydrocarbon oxidation mechanism. Dissertation for the Doctotal Degree. Heidelberg: Ruprecht-Karls-Universität, 2006

46 Qin Z, Yang H, Gardiner W C Jr. Measurement and modeling of shock-tube ignition delay for propene. Combustion and Flame, 2001, 124(1-2): 246–254

47 Ungut A, James H. Autoignition of gaseous fuel-air mixtures near a hot surface. Institution of Chemical Engineers, 1999, 148: 487–502

48 Law C K, Makino A, Lu T F. On the off-stoichiometric peaking of adiabatic flame temperature. Combustion and Flame, 2006, 145(4): 808–819

49 Fluent A. 14.5 Theory Guide. Canonsburg, PA: ANSYS Inc. 2012

50 Fenimore C P, Jones G W. Oxidation of soot by hydroxyl radicals. Journal of Physical Chemistry, 1967, 71(3): 593–597

51 Brookes S J, Moss J B. Prediction of soot and thermal radiation in confined turbulent jet diffusion flames. Combustion and Flame, 1999, 116(4): 486–503

52 Tesner P A, Snegiriova T D, Knorre V G. Kinetics of dispersed carbon formation. Combustion and Flame, 1971, 17(2): 253–260

53 Hall R J, Smooke M D, Colket M B. Physical and chemical Aspects of Combustion. New York: Gordon and Breach, 1997

54 Lindstedt R P. IUTAM Conference on Aerothermo-Chemistry in Combustors. Taiwan: IUTAM, 1991, 145–146

55 McDaniel M, Tichenor B A. Flare efficiency study. Washington: US Environmental Protection Agency, Industrial Environmental Research Laboratory, 1983, 40–49

56 Singh D K, Gangadharan P, Dabade T, Shinde V, Chen D, Lou H H, Richmond P C, Li X. Parametric study of ethylene flare operations using numerical simulation. Engineering Applications of Computational Fluid Mechanics, 2014, 8(2): 211–228