Flare Noise Reduction Exxon Chemical- Baytown Olefins Plant: 1994 CMA Energy Efficiency Award for "Flare Noise Reduction" in the category of "Public Outreach/Plant Site"

Abstract

Numerous community complaints were received because of what nearby residents perceived as excessive noise from BOP's elevated flares. Representatives from the Baytown Olefins Plant met with community residents to better understand their concerns. This qualitative data helped identify the flare noise problem to which BOP responded. BOP continued to solicit community feedback as various flare noise tests were conducted. Of particular concern to the community were low frequency rumbling noise and a higher frequency noise that resembles the sound of a jet plane passing overhead. To supplement the qualitative data received from the community, quantitative noise data was collected at various flaring conditions, wind conditions, and steam rates. Additional testing was performed to determine optimum steam rates for flaring events that could eliminate smoking and minimize noise. These tests concluded that reducing steam to the flare could reduce flare noise without jeopardizing smokeless operation. High intensity, low frequency rumbling noise (0-10 Hz), was rattling the windows and doors in the nearby community. It is typically generated by flame instability. Flame instability was occurring at BOP at fairly low flaring rates, and has been attributed to changes in the flare gas heating value and flare steam rates. Although a moderate amount of center steam lifts the flame off the top of the flare tip and prevents backburning (another source of flare noise), too much center steam makes a flame even less stable. This instability essentially causes a series of small explosions at the flare tip that generate low frequency noise. Combustion noise and steam injection noise contributed to the jet engine sound that was objectionable to the community. Steam injection noise increases as the amount of hydrocarbon burned in the flare increases, and noise increases as both hydrocarbon and steam injection increase. Although it is difficult to minimize the hydrocarbon to the flare, the steam to hydrocarbon ratio can be controlled to a minimum amount required for smokeless operation. Additionally, BOP can optimize the use of its two flares to reduce noise.