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

目前，天然气占美国能源需求的23%。除CH4外，原料天然气还含有水、高级碳氢化合物和其他在天然气运输和使用前必须除去的物质。对于海上油井，井口附近的处理对于防止水合物形成和天然气流向大陆时堵塞管道至关重要。原料气通常通过添加化学品或降低其露点来处理，但标准的处理设备通常很大，需要有人操作的平台。另一种方法是使用超音速天然气分离器：(1)在超音速膨胀中冷却气体以诱导液滴的形成和生长，(2)将液滴从气体中分离出来，(3)使用扩散器重新压缩干燥的气体以最小化压力损失。这些分离器比传统的工艺设备更小，没有活动部件，也不需要化学品。因此，它们适用于海上和海底应用。在全球范围内，其中三种设备现已投入商业运营。Twister BV是该提案的工业合作伙伴，处于开发和实施该技术的最前沿。然而，随着这些装置的采用，关于这些复杂蒸汽混合物中液滴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。智力优势：以提高天然气生产效率为总体目标，本提案在模拟超音速分离器中发现的条件下，研究了高度非理想水烃系统中的液滴形成、生长和结构。实验项目将利用压力测量和光谱技术，在马赫数与实际分离器相当的情况下，对超音速喷嘴中的冷凝过程进行表征。合成的气溶胶将用小角x射线和/或中子散射来表征。理论程序将侧重于理解液滴结构、形成和生长速率作为关键参数的函数，即气相组成和温度。将实验结果与理论计算和详细建模相结合，将对多组分液滴的形成和生长进行更可靠的描述，然后将其纳入用于描述和优化超音速分离器性能的计算流体动力学代码中。计算机模拟技术和密度泛函数理论以及小角度中子和x射线散射实验的新应用，通过解决以前无法研究的问题，正在帮助改变气溶胶科学领域。更广泛的影响：在更广泛的背景下，这项工作旨在提高天然气生产的能源效率。除了与国内天然气工业以及Twister BV相关外，这项工作的结果还引起了成核、气溶胶科学、云和大气物理学等领域的其他研究人员的兴趣。在教育和培训方面，该项目将为所有学生提供丰富的、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，特别是少数民族和代表性不足群体的学生参与研究。作为一项重要的外展活动，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，这是小学和高中教育中非常感兴趣但不易实现的过程。

Abstract 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.