Particulate emissions from flares with entrained droplets

  • Author / Creator
    Kazemimanesh, Mohsen
  • In this work, particles emissions from flares with entrained droplets were characterized during the operations of oil/gas wells. It is a likely scenario that droplets of flowback fluids or produced water entrain in the flare gas and burn in an open flame. Major ions found in these fluids are sodium and chloride ions, which can affect the particle emissions from a flare. A benchtop-scale laminar methane diffusion flame with and without NaCl particles, coupled with a high dilution sampling system, was used to study the fundamental interactions between soot and NaCl particles. Soot formation and evolution from inception and surface growth to coagulation and oxidation were observed for soot particles inside the flame. NaCl reduced the coagulation between soot particles in the agglomeration region; however, it also inhibited soot oxidation, leading to higher soot concentration released to ambient air. Freshly nucleated NaCl particles from its vapour phase formed in the post-flame region which were occasionally internally mixed with soot. NaCl also increased light absorption of soot due to its increased concentration; however, this study was inconclusive about whether or not the mass-specific absorption coefficient of soot changed with the addition of NaCl to the flame.

    A lab-scale turbulent diffusion flame from a pipe flare with different diameters with various gas compositions representative of flare gases in the upstream oil and gas industry was used with and without entrained droplets of different liquids, including flowback fluids from Cardium and Duvernay formations. Soot particle size and concentration did not depend on flare diameter or exit velocity, but noticeably changed with gas composition and its higher heating value. Data from electron microscopy images and effective density data provided consistent information on soot morphology. Flare soot had an effective density (and hence, a morphology) similar to that of soot from various combustion engines. Moreover, soot morphology was independent of gas composition, flare diameter, and flare exit velocity over the range tested. Adding water to the flame suppressed soot particle size and concentration. Addition of a tiny amount of inorganic salts to the flame increased particle concentration by orders of magnitude and decreased the particle size significantly, which was due to re-nucleation of salt particles in the post-combustion region. The addition of salts also increased the concentration of soot particles due to inhibition of soot oxidation near the flame front. Adding more salts increased the particle size markedly and the particle concentration slightly. Most of the particles smaller than ~150 nm had an effective density similar to that of salt and most of the particles larger than ~300 nm had a density close to that of soot. This result was also confirmed by electron microscopy images of the particles. These images also showed that most of the particles were either individual salt particles or internally mixed soot and salt particles. The significance of this study lies in its climate implications: increased soot and salt concentrations directly affect global climate by higher absorption and scattering of sunlight, respectively. On the other hand, they indirectly affect the climate by increasing cloud formation as cloud condensation nuclei. These implications may be currently underestimated for particle emissions from flares.

  • Subjects / Keywords
  • Graduation date
    Spring 2020
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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