(271b) CFD Study of Flare Operating Parameters

Flares have been identified as an important underreported or unreported emission source and recent flare tests performed on industrial-scale flare systems have indicated that, even if operating under the guidelines, flare efficiencies can go far below 98% depending on factors like air-to-fuel ratio, steam-to-fuel ratio, flare-tip velocity, vent gas heat content, and crosswind.  And there is a further question about the incomplete combustion products from flares including VOCs, NOx, HOx, CO, and soot, in addition to the unburned vent gas species.  Computational fluid dynamics (CFD) modeling has been shown to be a viable tool for predicting flare performance (DRE/CE) and emission species based on rigorous light-hydrocarbon combustion mechanisms. In this talk, validations of CFD modeling of the Berkeley flame, McKenna flame, and TCEQ’s 2010 controlled flare tests are presented. Much improved results were obtained for modeling the TCEQ/UT John Zink tests (within 5% of the measured DRE/CE). The CFD modeling cases to simulate various operating (jet velocity, combustion zone heating value or CZHV) and meteorological (crosswind) were also performed to study the interaction between these parameters.  An expanded definition of CZHV was proposed for air-assisted flares. The contour maps were generated to show the effect between DRE/CE and operating/meteorological parameters.