Development and Application of Simulation Methods for Clathrate Hydrates Phase Equilibria

笼形水合物相平衡模拟方法的开发与应用

• 批准号: 0933856
• 负责人: Amadeu Sum
• 金额: $ 33.5万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0933856&HistoricalAwards=false
• 关键词: Development; Application; Simulation; Methods; Clathrate

0933856SumClathrate hydrates are non-stoichiometric solids (generally hydrates of methane) with intriguing molecular structures consisting of water cavities enclosing small non-polar molecules. Accurate and reliable predictions of hydrate phase equilibria require knowledge of the hydrate composition, a quantity that is not easily accessible, but is greatly needed given the increasing importance of gas hydrates in the energy resource landscape. To date, much of the knowledge on hydrate phase equilibria derives from predictions based on the solid-solution theory by van der Waals and Platteeuw, which albeit practical, has several fundamental shortcomings. This proposal undertakes a fundamental study to investigate the molecular thermodynamics of clathrate hydrates in terms of their composition. The specific objectives for this project are to develop a rigorous computational methodology to determine the composition and distribution of guests in hydrate cavities and to then apply it in the prediction of three-phase (Lw-H-V) equilibria of clathrate hydrates.Intellectual Merit. To achieve the stated objectives, this study will develop and implement computational methods capable of determining solid phase equilibria. To accomplish this, two main tasks will form the core of the study: i) Develop and implement a novel algorithm for solid-phase Gibbs ensemble Monte Carlo with helical boundary conditions to rigorously capture solid phase equilibria, initially applied to model systems and water/ice, for the eventual application to clathrate hydrates, and ii) Perform GEMC and classical thermodynamic integration (TI) simulations, in a parallel effort to determine the composition and distribution of one or more guests in clathrate hydrates, including at conditions along the three-phase (Lw-H-V) equilibrium. Although laborious, the parallel effort with the thermodynamic integration method will validate and extend the applicability of the method. The proposed work is novel and transformative in that: i) the methodology overcomes severe sampling inefficiency that heretofore prohibited direct solid phase simulations using Gibbs ensemble Monte Carlo, and ii) it will be the first to directly evaluate, either through simulation or experiment, the absolute equilibrium composition and distribution of guests in the hydrate cages. If successful, this study will greatly expand the scope of practical simulations to the many areas that involve solid phase equilibria, and significantly advance the underlying science of clathrate hydrates phase equilibria underpinning applications such as their increasing role as a prominent energy resource.Broader Impact. This study will develop a framework toward more accurate and reliable methane hydrate phase equilibria predictions, which are routinely needed in industry, and consequently provide better knowledge on how to account for the composition of guests in the hydrate structure. Hydrate phase equilibria plays a central role in all current areas of technological interest on hydrates. In addition, the PIs and graduate students will be involved in the outreach activities coordinated by Prof. Barbara Moskal at CSM. This program supports students and teachers from elementary to high school by providing direct contact with the PIs in an out of the classroom to prepare and deliver lessons and instruction materials. The current CSM GK-12 program serves three public schools systems in the Denver area with large representations of minority students. In collaboration with Prof. Moskal, the PIs will develop materials focused on the science of clathrate hydrates, their potential importance in energy technologies, as well as an introduction to molecular simulation. The PIs are also closely involved with the Center for Hydrate Research and the NSF Renewable Energy MRSEC at CSM. Clathrate hydrates is central in the research and educational activities of these centers, and the impact of this work will potentially extend to other timely projects in the centers by leveraging mutual interaction and collaboration among PIs and students

0933856 SumClathrate水合物是非化学计量的固体（通常是甲烷的水合物），具有由封闭小的非极性分子的水腔组成的有趣的分子结构。水合物相平衡的准确和可靠的预测需要水合物组成的知识，这是不容易获得的量，但鉴于天然气水合物在能源领域的重要性日益增加，非常需要。迄今为止，水合物相平衡的知识大多来自于基于货车德瓦尔斯和普拉图的固溶体理论的预测，虽然实用，但有几个基本的缺点。该方案从笼形水合物的组成出发，对笼形水合物的分子热力学进行了基础性研究。该项目的具体目标是开发一种严格的计算方法，以确定水合物空腔中客体的组成和分布，然后将其应用于预测笼形水合物的三相（Lw-H-V）平衡。为了达到既定的目标，本研究将开发和实施能够确定固相平衡的计算方法。为实现这一目标，两项主要任务将构成研究的核心：i）开发和实施具有螺旋边界条件的固相吉布斯系综蒙特卡罗的新算法，以严格捕获固相平衡，最初应用于模型系统和水/冰，最终应用于笼形水合物，以及ii）执行GEMC和经典热力学积分（TI）模拟，在确定笼形水合物中一种或多种客体的组成和分布的平行努力中，包括在沿着三相（Lw-H-V）平衡的条件下。虽然费力，并行的努力与热力学积分方法将验证和扩展的方法的适用性。所提出的工作是新颖的和变革性的，因为：i）该方法克服了严重的采样效率低下，迄今为止禁止使用吉布斯系综蒙特卡罗直接固相模拟，和ii）它将是第一个直接评估，无论是通过模拟或实验，绝对平衡组成和水合物笼中的客人分布。如果成功的话，这项研究将极大地扩大实际模拟的范围，涉及固相平衡的许多领域，并显着推进基础科学的笼形水合物相平衡支撑的应用，如他们作为一个突出的能源资源越来越多的作用。这项研究将开发一个框架，以更准确和可靠的甲烷水合物相平衡预测，这是在工业中经常需要的，从而提供更好的知识，如何占水合物结构中的客人的组成。水合物的相平衡在当前所有有关水合物的技术领域中起着核心作用。此外，PI和研究生将参与由CSM的Barbara Moskal教授协调的外展活动。该计划支持从小学到高中的学生和教师，通过在课堂外与PI直接接触来准备和提供课程和教学材料。目前的CSM GK-12计划为丹佛地区的三所公立学校系统提供服务，其中有大量少数民族学生。与Moskal教授合作，PI将开发专注于笼形水合物科学的材料，它们在能源技术中的潜在重要性，以及分子模拟的介绍。PI还与CSM的Hydrocarbon研究中心和NSF可再生能源MRSEC密切合作。笼形水合物是这些中心的研究和教育活动的核心，通过利用PI和学生之间的相互互动和合作，这项工作的影响可能会扩展到中心的其他及时项目