Estimation of the Air-Demand, Flame Height, and Radiation Load from Low-Profile Flares

ISIS-3D General Comments

• Based on Computational Fluid Dynamics with radiative heat transfer and combustion chemistry
• Linked model is capable of simulating complex, three-dimensional objects engulfed in fires
• Provide reasonably accurate estimates of the total heat transfer to objects from large fires
• Predict general characteristics of temperature distribution in object
• Accurately assess impact of variety of risk scenarios (wind, % flame coverage, thermal fatigue for given geometry, etc.)
• Reasonable CPU time requirements on “standard” desktop LINUX workstation

Approach to Modeling Full Flare Fields

• Model Single Burner Test
• Perform Calibration Tests
• Calibrate Soot Yield and Reaction Parameters for Test Fuel
• Predict flame shape and size
• Model Multi-Burner Test
• Perform Radiation Calibration Tests
• Check Tip/Row Spacing
• Predict flame shape and size
• Model Full Flare Field
• Use Calibrated Soot Yield and Radiation Models
• Predict Flare Performance (Smoke Production/Air Demand)
• Predict Radiation Load on Wind Fence

Conclusions

• ISIS-3D Model:
• Single-burner model used 110,000 cells
• Three-burner model used 188,000 cells
• Full-field model used 700,000 cells (Sustained Flow)
• 1,200,000 cell (Peak Flow)
• Combustion chemistry for propane, ethylene, mixed gas
• Modeled flame shape/size for 3 fuels for single and three burner tests
• Predictions compared to data from 12 tests (2 tip sizes, 3 operating pressures, 2 radiation sample locations)
• Predicted “reasonable” estimates of radiation heat transfer and air demand for low profile flare
• Air/fuel ratios range from 28 to 47 for 3-burner test and from 37 (Peak Flow Case) to 51 (Sustained Flow Case)
• Calibrated flare model applied to full-flare field to estimate:
• Air demand for specified tip/row spacing
• Radiation load on wind fence for nominal and peak flow cases
• Expected flame height and smoke production for nominal and peak flow cases