An evaluation of flare combustion efficiency using open-path Fourier transform infrared technology

Area of Science:

• Environmental Science
• Chemical Engineering
• Combustion Science

Background:

• Flares are crucial for destroying organic compounds, but efficiency may decrease with lower Btu content.
• Previous studies suggested low-Btu flares might operate at efficiencies as low as 65%.
• Combustion models exist to predict efficiency based on wind speed and discharge velocity.

Purpose of the Study:

• To evaluate the combustion efficiency of a low-Btu flare using Open-path Fourier transform infrared (OP-FTIR) technology.
• To compare OP-FTIR findings with existing combustion models.
• To develop methods for quantifying efficiency in dual-stack flare systems.

Main Methods:

• Utilized OP-FTIR technology for real-time gas analysis.
• Monitored ratios of carbon monoxide (CO) to carbon dioxide (CO2) and CO to tracer gases (SF6, CF4).
• Employed dispersion modeling and developed a method to differentiate between two flare stacks.

Main Results:

• OP-FTIR measurements indicated combustion efficiencies consistently above 90% for the low-Btu flare.
• This contrasts sharply with model predictions, which suggested efficiencies as low as 30%.
• A novel method was successfully developed to quantify efficiency for each of the two stacks.

Conclusions:

• OP-FTIR technology provides accurate, high combustion efficiency data for low-Btu flares, even those primarily composed of CO.
• Existing combustion models may overestimate the negative impact of low Btu content and specific operating conditions.
• The developed dual-tracer method enables effective analysis of multi-stack flare systems.