Experimental Analysis of the Impacts of Aerosolized Liquids on Flare Emissions
Creators: Bello, Olanrewaju Wasiu
Publisher: name: University of Alberta Library
Year: 2024

<p>This study characterized flare-like flame emissions and improved methods of reducing flare emissions during well completion operations in the upstream oil and gas industries. Flowback fluids are water-based solutions that return to the earth’s surface with extracted oil and gas during and after the completion of hydraulic fracturing. Droplets of the flowback fluids are likely to become entrained in the flare gas and burn in an exposed flame. Sodium and chloride ions, which are prevalent in flowback fluids, can influence the particle emissions from flaring. In trying to mitigate flare emissions, steam-assisted flares, which are often used in the downstream oil and gas industries as a strategy to produce &quot;smokeless&quot; combustion, were compared with liquid water. Three fuels were used to investigate this comparison: pure propane, pure methane, and a mixture of 90% methane and 10% propane, the latter approximating the typical volumetric higher heating value of Alberta flare gas. Both steam and liquid water were injected into the flare through the fuel stream. The result of the investigation suggests that liquid water-assisted flares in the oil and gas industries would likely produce lower emissions with a lower operating cost than steam-assisted flares. This finding initiated the second study, in which liquid water injected through the fuel stream was compared with liquid water injected through the air stream into the flare. Liquid water with impurities (NaCl) was also investigated because NaCl is a surrogate species for the impurities contained in the water used at offshore and downstream oil and gas facilities. Liquid water injection through the air stream (external injection) directed very close to the base of the flame ensured water was present early in the combustion process and reduced NOx emissions to a greater extent compared to when the water was injected through the fuel stream. External liquid water injection into turbulent non-premixed flames can effectively reduce black carbon without a need for costly boiler operation to produce steam. NaCl impurities in the injected liquid water cause an increase in soot emissions. The increase in soot emissions due to NaCl addition initiated the third study. <br>
The third study investigates the effect of sodium chloride on the charge state of soot nanoparticles evolved in a laminar diffusion flame by measuring the soot particle size distribution (PSD), average charge per particle, and charge fraction at various locations within the flame. A charged monodispersed coagulation model was employed to ascertain whether coagulation was the primary cause of the differences observed in particle emissions when NaCl is introduced into flames. The effect of sodium chloride on a methane flame was investigated by comparing the experimentally measured data for methane-only and methane-NaCl flames. The addition of NaCl particles to the laminar diffusion flame did not have a significant effect on the particles in nucleation region of the flame. The majority of the incipient soot particles in both flames are uncharged, and their sizes are nearly the same, with diameters of approximately 5 nm or less. However, the size of soot particles differs by approximately 10% to 25% between methane-only and methane-NaCl flames in the coagulation-dominated region (i.e., between HAB 47 mm and 55 mm) of the flame. The net charge on soot particles within the coagulation region of the methane-only flames is negative while it changes to positive with NaCl addition. The fraction of charged particles and ion concentration decreases with NaCl addition within the coagulation region and more uncharged particles are witnessed.  Interestingly, the coagulation model results for charged and uncharged particles in coagulation processes were identical. The study reveals that the smaller particle size in methane-NaCl flames is primarily a result of oxidation rather than a reduction in particle charge. NaCl promotes oxidation in specific flame regions, leading to differences in soot evolution between methane-only and methane-NaCl flames.</p>