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

doi:10.1007/s11705-016-1594-y

Front. Chem. Sci. Eng.

2016, Vol. 10

Issue (4) : 459-471 https://doi.org/10.1007/s11705-016-1594-y

REVIEW ARTICLE

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

Anan Wang¹,Helen H. Lou¹(

),Daniel Chen¹,Anfeng Yu²,Wenyi Dang²(

),Xianchang Li³,Christopher Martin⁴,Vijaya Damodara¹,Ajit Patki³

¹. Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, TX 77710, USA
². SINOPEC Safety Engineering Institute, Qingdao 266000, China
³. Department of Mechanical Engineering, Lamar University, Beaumont, TX 77710, USA
⁴. Department of Chemistry, Lamar University, Beaumont, TX 77710, USA

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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.

Keywords flare soot emission combustion mechanism CFD simulation

Corresponding Author(s): Helen H. Lou,Wenyi Dang

Just Accepted Date: 28 September 2016 Online First Date: 09 November 2016 Issue Date: 29 November 2016

Cite this article:

Anan Wang,Helen H. Lou,Daniel Chen, et al. Combustion mechanism development and CFD simulation for the prediction of soot emission during flaring[J]. Front. Chem. Sci. Eng., 2016, 10(4): 459-471.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-016-1594-y
https://academic.hep.com.cn/fcse/EN/Y2016/V10/I4/459

Fig.1 Reaction-path diagram of C₆H₆ production with 15 major intermediate species

Fig.2 Rate of production of the major reactions influencing the production of C₆H₆

Fig.3 Rate of production of the major reactions influencing the production of C₆H₅

Fig.4 Error of reduced mechanism Vsoot vs. USC-II

Fig.5 Laminar flame speed for different equivalence ratios for C₃H₆

Fig.6 Laminar flame speed for different equivalence ratios for CH₄

Fig.7 Laminar flame speed for different equivalence ratios for C₂H₄

Fig.8 Ignition delay time for different temperature for C₃H₆

Tab.1 Comparison of Ignition delay time results

Fig.9 Adiabatic flame temperature of CH₄

Fig.10 Adiabatic flame temperature of C₂H₄

Fig.11 Schematic drawing of an air assisted flare stack and flare tip

Fig.12 Mesh view of computational model for air assisted flare

Tab.2 Input conditions for 6 air-assist cases

Fig.13 Temperature contours for various air assisted test cases

Tab.3 Comparison of soot emissions

Tab.4 Comparison of combustion efficiency (CE) results

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