Analysis of the Environmental and Safety Aspects of a Routine Utility Flare Using Computational Fluid Dynamics

The CFD code C3d was used to investigate the operation of a routine utility flare at low and high gas firing rates in an oil field in Iraq. This code was developed for the analysis of transient flares, enables the simulation of flare operation, and offers detailed estimates of the flame shape and the emissions produced. In this work, the numerical simulations included two flare gas rates, 9 t/h (2.5 kg/s) and 45 t/h (12.5 kg/s), under three crosswind conditions (4 m/s, 8 m/s, and 14 m/ s) and using three stack heights (35 m, 45 m, and 55 m). The results of this work provided insights into the flame shape and size, pollutant types and dispersion, and ground heat radiation levels from the flare. The safety analysis found that ground-level heat increased with higher flare gas rates and decreased with higher stack heights. The stack height of 55 m and the lower gas firing rate of 9 t/h were identified as the safest operating conditions, as they provided lower ground-level heat compared to the higher flare gas rate of 45 t/h. The heat radiation at a stack height of 55 m during normal firing rates remained below 1600 W/m2, which was within the safe continuous exposure limit for personnel not wearing protective clothing. This limit is in accordance with the recommended safety guidelines for personnel and equipment as outlined in API 521. Likewise, the environmental analysis showed that the plume size increased with increasing flare gas rate, while pollutant dispersion intensified with stronger crosswinds. When comparing the two gas firing rates, in the case of 9 t/h, there was a smaller plume and less pollutant dispersion, which illustrated a relatively lower impact on the environment.