Quantifying the Carbon Conversion Efficiency and Emission Indices of a Lab-Scale Steam-Assisted Flare

• Author / Creator

  Ahsan, Abbas

• A lab-scale flaring facility was established to study the carbon conversion efficiency (CCE) and emission indices (EIs) of total unburned hydrocarbons (THC), carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), and black carbon (BC) for a 25.4 mm diameter steam-assisted flare. Diagnostic equipment including a photoacoustic extinctiometer, NOx analyzer, and gas chromatograph were used to measure the concentration of the plume species generated by 20 or 40 standard liters per minute (SLPM) methane or propane flames with inner or outer coflows of steam. A carbon mass balance was applied to the flare to account for the carbon-based species produced by combustion and allow for estimates to be made of combustion efficiency and species emission rates of THC, CO2, CO, NOx, and BC. Seven unique experimental sets were performed in which the reference case was defined as a 20 SLPM methane jet diffusion flame with an inner coflow of steam through a 12.7 mm diameter tube. The remaining six sets branched off from the reference case with each set featuring a single experimental design difference. Each experimental set was based on a fixed fuel flow rate in which increasing amounts of assist fluid were injected into the flame until a CCE of < 10% was achieved. The steam-to-fuel gas mass flow rate ratios which provoked the onset of the collapse in CCE at 96.5% had a range of 1.0 – 4.1 for the various experimental sets. EIs for NOx and BC were found to be at a maximum when the flame was unassisted, but decreased by approximately two orders of magnitude with increasing steam assist. EIs for CO2 remained at a maximum value until the onset in the CCE collapse at which point they began to drop by an order of magnitude. The reverse trend occurred for THC emissions as a result of fuel stripping. During the CCE collapse phase, some of the experimental sets generated CO emissions as a result of poor fuel-air mixing. The hydrodynamic conditions at the burner exit plane were investigated to provide insight into the discrepancy in behaviour between the different experimental sets.

• Subjects / Keywords

  • Carbon Conversion Efficiency
  • Combustion
  • Emission Index
  • Flaring
  • Steam Assist

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-jtz6-m751

• License

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