ENV-15-32 Evaluation of Alternative Methods for Remote Monitoring of Petrochemical Flare Operating Efficiency

Description:

A study was conducted to determine if an alternative method of visible flame verification, Multivariate Image Analysis (MIA), could be developed to monitor the operation of elevated steam assisted flares located at a petrochemical manufacturing facility’s ethylene manufacturing unit. The purpose of the study was to determine if flare flame appearance and intensity, as digitally recorded using a high definition video camera, could be correlated with combustion efficiency measured by a Passive Fourier Transform Infrared Spectroscopy Analyzer; and used as an alternative method to verify flare combustion efficiency as effectively as calculating Net Heating Value in the Combustion Zone (NHVcz) or Lower Flammability Limit (LFL). In order to develop and confirm that efficient operation of the flares could be verified by analyzing a visible image of the flame recorded by a high definition digital video camera, two steam assisted flares of different manufacturers and designs were studied over a two week period at varying operating conditions. One flare utilizes center steam, as well as upper (ring) and lower (near flare tip opening) steam; while the other flare only injects steam via an upper ring at the flare tip. The two flares were also chosen because they combusted streams of different composition; both are predominantly a hydrogen and methane stream, one with higher hydrogen concentrations while the other contained a higher concentration of the olefins ethylene and propylene in the hydrogen/methane stream. Each flare was simultaneously monitored with a High Definition Video Camera, FLIR Infrared Camera, and a SIGIS 2 Infrared Spectrometer. To the extent practical and achievable, each flare was tested at a target flow, composition, and flame rating condition by varying steam, Waste Gas, and Supplemental Gas rates to the flare. Key objectives of the flare testing were: 1) Investigate a correlation for destruction and removal efficiency (“DRE”) as compared to Combustion Efficiency (“CE”); 2) Develop and implement interim process control parameters while continuing evaluation of MIA, 3) Conduct longer-term evaluation of MIA as an alternative means of ongoing flare monitoring, including the development of process control parameters or operator feedback concepts for managing flare operation, 4) If successfully demonstrated, then implement MIA automated process control or, if automation is not successful, alternative operator feedback mechanisms. The field tests indicated that the average flare CE during each test run, based on the Passive Fourier Transform Infrared (PFTIR) measurements and analyses, were greater than 98% under all operating conditions tested, including high Steam-to-Vent Gas (S/VG) ratios and low theoretical calculations of NHVcz. Visual, Infrared (IR), and FLIR imagery suggest that the upper and lower steam did not mix completely within the flame zone, allowing a pocket of efficient combustion to occur within the surrounding steam envelope.