GOALI: Collaborative Research: Fundamental Studies of water-hydrocarbon condensation

目前，天然气供应约占美国能源需求的23%。除了CH4，原始天然气还含有水、高级碳氢化合物和其他物质，在运输和使用天然气之前必须去除这些物质。对于海上油井，井口附近的处理对于防止天然气流向大陆时形成笼状物并堵塞管道至关重要。原料气通常通过添加化学品或降低露点进行处理，但标准的处理设备往往很大，需要人工平台操作。另一种方法是使用超音速天然气分离器，该分离器(1)在超音速膨胀中冷却气体以诱导液滴形成和生长，(2)将液滴从气体中分离，(3)使用扩散器重新压缩干燥气体，以将压力损失降至最低。这些分离器比传统工艺设备更小，没有活动部件，也不需要任何化学品。因此，它们既适合近海应用，也适用于海底应用。在全球范围内，其中三个设备现已投入商业运营。这项提议的工业合作伙伴Twister BV处于开发和实施这项技术的前沿。然而，随着这些设备的采用，关于这些复杂的蒸汽混合物中液滴的形成和生长的关键问题仍然存在，这些问题与液滴的结构有关。智慧的优点：该方案以提高天然气生产效率为首要目标，在模拟超音速分离器的条件下，研究高度非理想的水烃系统中液滴的形成、生长和结构。该实验计划将利用压力测量和光谱分析，在与实际分离器相当的马赫数下，表征超音速喷嘴中的冷凝过程。将使用小角x射线和/或中子散射对生成的气溶胶进行表征。理论课程将侧重于了解液滴的结构、形成和生长速度作为关键参数的函数，即汽相组成和温度。将实验结果与理论计算和详细建模相结合，将得到更可靠的多组分液滴形成和生长的描述，然后可以被纳入用于描述和优化超音速分离器性能的计算流体力学程序中。这种计算机模拟技术和密度泛函理论以及小角中子和X射线散射实验的新应用，通过使以前无法解决的问题得以解决，帮助改变了气溶胶科学领域。更广泛的影响：这项工作旨在更广泛的背景下，提高天然气生产的能源效率。除了它们与国内天然气工业以及Twister BV有关外，这项工作产生的结果还引起成核、气溶胶科学以及云和大气物理方面的其他研究人员的兴趣。在教育和培训领域，该项目将为所有学生提供一个丰富的、高度跨学科的研究环境，并将为研究生提供独特的国际经验。将鼓励本科生参与研究，特别是来自少数群体和代表性不足群体的参与。作为一项重要的推广活动，将建立桌面扩散云室，以便学生和教师可以在课堂上可视化云的形成，这是一个在小学和高中教育中非常感兴趣但不易实现的过程。

Currently, natural gas supplies ~23% of U.S. energy needs. In addition to CH4, raw natural gas contains water, higher hydrocarbons, and other substances that must be removed before the gas is transported and used. For off-shore wells, treatment near the wellhead is critical to prevent clathrates from forming and plugging the pipeline as gas flows to the mainland. The raw gas is normally treated by adding chemicals or reducing its dew point, but standard processing equipment is often large and requires manned platform operation. An alternative approach is to use supersonic natural gas separators that (1) cool the gas in a supersonic expansion to induce droplet formation and growth, (2) separate the droplets from the gas, and, (3) recompress the dried gas using a diffuser to minimize pressure losses. These separators are smaller than traditional process equipment, have no moving parts, and require no chemicals. Thus, they are suited for both off-shore and sub-sea applications. Worldwide, three of these devices are now in commercial operation. Twister BV, the industrial partner for this proposal, is at the forefront of developing and implementing this technology. As these devices are adopted, however, critical questions remain regarding droplet formation and growth in these complex vapor mixtures, and these questions are related to the structure of the droplets.Intellectual Merit: With an overarching goal of improving the efficiency of natural gas production, this proposal examines droplet formation, growth, and structure in highly non-ideal water hydrocarbon systems under conditions that mimic those found in the supersonic separators. The experimental program will characterize the condensation process in supersonic nozzles, at Mach numbers comparable to the real separators, using pressure measurements and spectroscopy. The resultant aerosols will be characterized using small angle x-ray and/or neutron scattering. The theoretical program will focus on understanding droplet structure, formation and growth rates as a function of the key parameters, i.e., the vapor phase compositions and temperature. Combining the experimental results with the theoretical calculations and detailed modeling will result in more robust descriptions of multicomponent droplet formation and growth that can then be incorporated into the computational fluid dynamics codes used to describe and optimize the performance of supersonic separators. This novel application of computer simulation techniques and density functional theory and of small angle neutron and x-ray scattering experiments is helping transform the field of aerosol science by enabling the solution of problems that previously defied investigation.Broader Impacts: In a broader context, this work is directed toward improving the energy efficiency of natural gas production. In addition to their relevance to the domestic natural gas industry, as well as to Twister BV, the results stemming from this work are of interest to other researchers in nucleation, aerosol science, and cloud and atmospheric physics. In the area of education and training, this project will provide a rich, highly interdisciplinary research environment for all students and will incorporate a unique international experience for graduate students. Participation in the research by undergraduate students, particularly from minority and underrepresented groups, will be fostered. As an important outreach activity, table top diffusion cloud chambers will be built so that students and teachers can visualize cloud formation in the classroom, a process that is of great interest in elementary and high school education but is not easily realized.