Joseph D. Smith, Ph.D. and Ahti Suo-Ahttila, Ph.D.,
Systems Analyses and Solutions, LLC Owasso, Oklahoma, USA
Scot Smith and Nigel Philpott, Zeeco, Inc.
Zeeco Inc. Broken Arrow, Oklahoma, USA
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Abstract
A detailed computational fluid dynamics (CFD) model of an elevated multipoint flare has been developed using a proprietary flare modeling tool. This tool has been used to simulate the ignition phenomena for this particular flare at a gas flow rate of 350 Tons per hour (TPH). Simulation results have been directly compared to operating test data for this flare. Verification results has demonstrated the ability of this virtual tool to replicate the measured flame spread rate and reproduce the measured pressure wave generated during the ignition event. Based on this verification, the tool has been used to conduct over sixty separate simulations to investigate the ignition behavior for this flare. Results from these simulations clearly show the critical effect of ignition delay on the magnitude of the pressure wave generated during ignition. The main conclusion drawn from this analysis is that the ignition system’s reliability to quickly ignite the flare gas above the flare tip is critical to safe operation. Results show that a delay of from 0.3 to 0.6 sec has a major impact on the magnitude of the pressure wave generated during flare ignition. This is especially important given these results were based on a low flow rate which is approximately one-tenth of full flare operating conditions. At higher flow rates, a pressure wave capable of damaging local equipment and injuring plant personnel may be possible. Based on this observation, additional work has been conducted to assess the explosion potential. Results of this work will be discussed during the presentation. This tool has also been used to evaluate and identify more efficient and reliable ignition techniques to reduce the explosion risk caused by excessive flare gas accumulation above the flare tip.