Estimated flare emissions created during flare ignition transient

Abstract

Gas flares are used to avoid catastrophic events where pressurized highly flammable gases must be safely discharged from processing facilities in chemical and petrochemical plants. Gas flaring in Russia, Iraq, and Iran represented approximately 39% of the 1,500 billion cubic meters of gas flared world-wide in 2016. Studies of flare design and performance have identified gas mixing, heat content, tip exit velocity, and crosswind velocity as key factors contributing to air emissions from gas flaring. To minimize these emissions, Computational fluid dynamics (CFD) has been used to analyze and optimize gas flare design and operation. Flare flame height and shape under diverse atmospheric conditions is highly variable and complex interactions between adjacent burner flames included in multi-point ground flares must be analyzed using Large-Eddy Simulation (LES) based CFD tools. Transient flare ignition and cross lighting requires detailed chemistry to accurately predict flame size/ shape, pressure profiles and associated gas emissions. Soot formation and radiation emissions from multi-tip flare systems burning upwards of 700,000 kg/hr in 400 flare tips have been predicted using a validated LES based CFD tool called C3d. This tool predicted radiation flux and respective temperature of surrounding equipment and gas emissions under no-wind and 10 mph wind. Predictions were compared to measured flame shape/size, radiation flux, and soot production for various fuel types under different wind conditions. A new technology to directly measure other air emissions during flare operation was also discussed. Comparison of measured flare performance to predictions haven been used to validate CFD results. The validated CFD tool along with the new measurement technology can be used to estimate world-wide flare emissions and develop strategies to minimize flare emissions.