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Particulate emissions from turbulent diffusion flames with entrained droplets: A laboratory simulation of gas flaring emissions
Journal of Aerosol Science ( IF 4.5 ) Pub Date : 2021-05-14 , DOI: 10.1016/j.jaerosci.2021.105807
Mohsen Kazemimanesh , Alberto Baldelli , Una Trivanovic , Olga Popovicheva , Mikhail Timofeev , Natalia Shonija , Yuri Obvintsev , Chen Kuang , A. Melina Jefferson , Joel C. Corbin , Greg G. Goss , Daniel S. Alessi , Matthew R. Johnson , Steven N. Rogak , Jason S. Olfert

Global flaring volume exceeds 140 billion m3 annually and flares are a key source of particulate air pollution. During flowback operations subsequent to fracturing of a well, droplets of flowback water—with varying levels of dissolved salts—can be entrained in the flared gas. Despite the widespread prevalence of fracturing, very little is known about the properties of particle emissions from such flares. To study these properties, we used a laboratory pipe flare producing a turbulent diffusion flame without and with entrained droplets. Entrained droplets of deionized water, sodium chloride solution, and solutions representing two typical flowback waters in Canada (Cardium and Duvernay) were used. Three different gas compositions (consisting of C1 to C7 alkanes, carbon dioxide, and nitrogen) representative of flares in the upstream oil and gas sector in Alberta, Canada were studied. The results showed that the salt in the entrained flowback droplets increased the particle concentration by about one order of magnitude by forming freshly nucleated salt particles. Moreover, soot concentration increased as a result of entrained salt. Effective density results showed that small particles (<150 nm mobility diameter) were mainly salt, while large particles (>300 nm) were mostly soot—a result also confirmed by transmission electron microscopy (TEM). Electron micrographs showed that the majority of particles were either individual salt particles or internally-mixed soot-salt particles. The inorganic salt particles mainly consisted of Na and Cl, the two most abundant elements in flowback water. Raman spectroscopy indicated that the salt had much less (or no) impact on graphitic nanostructure of soot, while the fuel blend had a significant effect. The results of this study are significant as they reveal that current emission inventories based on flaring of gases only may underestimate soot emissions from flares with entrained droplets.



中文翻译:

夹带液滴的湍流扩散火焰中的颗粒物排放:燃烧气体排放的实验室模拟

全球燃烧体积超过了140十亿米3每年,火炬是空气中颗粒物污染的主要来源。在井压裂后的回流操作过程中,带有不同溶解盐含量的回流水滴会夹带在燃烧的气体中。尽管压裂普遍存在,但对于这种火炬的颗粒排放特性知之甚少。为了研究这些特性,我们使用了实验室管火炬,该火炬产生了湍流的扩散火焰,没有或带有夹带的液滴。使用了去离子水,氯化钠溶液和代表加拿大两种典型回流水(Cardium和Duvernay)的溶液的夹带液滴。研究了加拿大艾伯塔省上游石油和天然气部门火炬的三种不同气体成分(由C1至C7烷烃,二氧化碳和氮气组成)。结果表明,夹带的回流液滴中的盐通过形成新的成核盐颗粒而使颗粒浓度增加了约一个数量级。此外,由于夹带盐,烟灰浓度增加。有效密度结果表明,小颗粒(迁移直径<150 nm)主要是盐,而大颗粒(> 300 nm)主要是烟灰-透射电子显微镜(TEM)也证实了这一结果。电子显微照片显示,大多数颗粒是单个盐颗粒或内部混合的烟尘盐颗粒。无机盐颗粒主要由Na和Cl组成,这是返排水中最丰富的两种元素。拉曼光谱表明,该盐对烟灰的石墨纳米结构的影响较小(或没有),而燃料混合物起了很大的作用。这项研究的结果是有意义的,因为它们表明,仅基于气体燃烧的当前排放清单可能会低估夹带液滴的火炬产生的烟尘排放。

更新日期:2021-05-19
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