Toward a Better Air-Assisted Flare Design for Purge Flow Conditions: Experimental and Computational Investigation of Radial Slot Flow into a Crossflow Environment

Abstract

Enhancing the flare gas/air mixing process above the flare tip is critical to optimizing flare performance in terms of emissions. A new flare tip design using an aerodynamic nozzle (such as that used in jet engines to increase thrust on takeoff) has been developed to control the flare gas exit velocity and the local mixing above the flare tip. The work described in this paper focuses on understanding the fluid mixing for the new flare tip design. The flow field of a jet injected into a crossflow is found in several systems, including combustion equipment, drying systems, quenching systems, and mixing tanks. A computational fluid dynamics (CFD) technique for simulating radial slot jet flow into crossflow has been validated with experimental results. Sets of experimental data were obtained from an experimental setup, which was designed and built in our laboratory. A hotwire anemometer was used to obtain the measurements of the radial velocity profiles at different axial positions and the centerline velocity profiles that are produced from the impingement of these axial profiles of velocity. A comparison between the simulation velocity profiles and experimental data was performed, and good agreement between the profiles was clearly observed. The obtained data showed that the centerline velocities were increased significantly just after the injection plane of the radial slot due to the reduction of cross-sectional area available for the flow.

Toward a Better Air-Assisted Flare Design for Safe and Efficient Operation during Purge Flow Conditions: Designing and Performance Testing

“…The new flare tip was tested under various operating conditions. Previous studies on flares , were conducted to investigate the impact of the radial slot air jet on the crossflow field. The first study was focused on collecting the required experimental data using cold flow conditions for a radial slot air jet injected perpendicularly into air crossflow.…”

“…Waste gases in these flow conditions do not have sufficient mixing energy to effectively mix waste gas with the surrounding ambient air. Consequently, this leads to poor mixing in the combustion zone, which causes low CE …”

“…Thus, this paper, which is the final part of a series of studies on designing a new air-assisted flare tip, describes the design, construction, and testing of a high-performance air-assisted flare that can efficiently operate under a wide range of flow rates, including purge flow conditions. In the first part of this series of studies, the experimental data required to validate a Computational Fluid Dynamics (CFD) model were collected . In the second part, the validated CFD model was used to examine the impact of different design parameters (injection angle, slot height, jet velocity) on the flow field above the flare tip .…”

“…Consequently, this leads to poor mixing in the combustion zone, which causes low CE. 8 Several previous experimental and theoretical studies have been conducted to investigate the effects of flare assist media, 7,9−12 waste gas flow rate, 6,13,14 and other operating factors including waste gases heating value, 9,15 crosswind velocity, 16,17 flare head configuration, 10 etc. as relates to the CE aimed at finding the optimum range of each factor to achieve high CE.…”

“…In the first part of this series of studies, the experimental data required to validate a Computational Fluid Dynamics (CFD) model were collected. 8 In the second part, the validated CFD model was used to examine the impact of different design parameters (injection angle, slot height, jet velocity) on the flow field above the flare tip. 25 Based on the findings of these studies, the best design parameters were selected and used in this study to build the new flare tip.…”