Investigation of mass and heat transport and sustainability of the novel thermally driven membrane distillation crystallization process

1236846当考虑到较流行的海水淡化工艺之一反渗透时，实际海水淡化中的水回收在水力上被限制在大约60%，而在微咸水淡化中，由于矿物垢的形成，回收被限制在大约80%。限制水回收和在较高回收率下不断增加的能源需求可能会限制当前使用的膜淡化技术的进一步改进。蒸馏过程，特别是利用蒸汽压作为驱动力的膜过程，不受进料或盐水流渗透压的限制，可能是克服当前海水淡化过程局限性的一种解决方案。因此，本研究的主要目的是全面研究新型膜蒸馏结晶过程中的热质传递，在这种过程中，水从过饱和的料液中可持续地脱盐，同时矿物可以被回收用于有益的用途。这项研究的重点是测量在含有难溶盐分的水的淡化过程中形成的矿物晶体的形成速度、粒度分布、与膜的粘附性以及矿物晶体的去除/收获。还研究了操作条件和环境对膜蒸馏结晶过程可持续生产纯净水和矿物的影响。将进行受控实验室实验，其中将应用严格的科学方法来识别、表征和量化控制整体和表面结晶的单独和组合机制及其对通过膜的热量和质量传输的影响。特别是，研究的重点将是确定最佳的操作条件，在这种条件下，这一海水淡化和矿物回收的混合过程可以在过饱和条件下可持续地运行，以生产水和生产有价值的矿物。通过将作为这项研究的一部分开发的分析方法和定量工具，将改善目前对水通过鳞片层蒸发的基本原理和机制的理解，随后是多孔合成膜。这些将有助于将这些知识应用于小型和大型工程系统的建模和设计。现有海水淡化过程中有限的水回收是海水淡化运行成本上升的原因。这项研究将解决通过不断改进以更高质量、更低能源需求、使用可再生能源且不损害环境的水生产技术来增加水可获得性的全球需求。了解热驱动膜过程处理过饱和溶液时可逆和可重复的膜污染结垢机理，将缓解咸水淡化过程中遇到的主要问题之一。归根结底，这项研究的目标是提高我们以负担得起的成本向现代和发展中国家的公众提供清洁水的能力。结果还将有助于设计更好的处理工艺，以减少向环境排放的盐水，并增加对自然资源的依赖，如太阳能，用于海水淡化。研究和教育计划将支持本科生和理工科研究生，特别是代表人数不足的群体/少数群体参与研究和教育。开展互动讲座和实践活动，建立大学前教师继续教育课程，将提高学生对科学、工程和环境的兴趣，并有望引导更有积极性的学生继续接受环境工程方面的高等教育。

1236846CathWhen considering one of the more popular desalination processes, reverse osmosis, practical water recovery in seawater desalination is hydraulically limited to approximately 60 percent, and in brackish water desalination, recovery is limited to approximately 80 percent by mineral scale formation. Restricted water recovery and increasing energy demand at higher recoveries might limit further improvement of currently used membrane desalination technologies. Distillation processes, and specifically membrane processes that utilize vapor pressure as a driving force, are not limited by the osmotic pressure of feed or brine streams, and might be a solution to overcome the limitations of current desalination processes. Thus, the main objective of this research is to comprehensively investigate heat and mass transport in novel membrane distillation crystallization processes in which water is sustainably desalinated from supersaturated feed solutions and minerals can be simultaneously recovered for beneficial use. The research focuses on measuring the rates of formation, size distribution, adhesion to membranes, and removal/harvesting of mineral crystals that form during desalination of water containing sparingly soluble salts. It also investigates the effects of operating conditions and environments on the sustainable production of purified water and minerals using the membrane distillation crystallization process. Controlled laboratory experiments will be carried out in which a rigorous scientific approach will be applied to identify, characterize, and quantify the individual and combined mechanisms controlling bulk and surface crystallization and their effects on heat and mass transport through the membrane. In particular, the focus of the research will be to identify the optimal operating conditions under which this hybrid desalination and mineral recovery process can be sustainably operated under supersaturated conditions to produce water and produce valuable mineral. Through the analytical methods and quantitative tools that will be developed as part of this research, improvements will be made to the current understanding of the fundamental principles and mechanisms involved in evaporation of water through scale layers followed by porous synthetic membranes. These will help the application of this knowledge in the modeling and design of small and large engineered systems.Limited water recovery in existing desalination processes is the cause for elevated operating costs of desalination. This research will address the global need to increase water availability through the constant improvement of technologies that produce water at higher quality, lower energy demand, using renewable sources of energy, and without harming the environment. Understanding the mechanisms of reversible and repeatable membrane fouling scaling when treating supersaturated solutions by thermally driven membrane processes will mitigate one of the main problems encountered in desalination of saline water. Ultimately, the goal of this research is to improve our ability to provide clean water at an affordable cost to the public in modern and developing countries. The results will also facilitate the design of better treatment processes to reduce the discharge of brines to the environment and increase the reliance on natural resources, such as solar energy, for desalination. The research and educational plan will support the participation of undergraduate and graduate science and engineering students, and specifically from underrepresented groups/minorities in research and education. The development of interactive lecture and hands-on activities, and the establishment of continued education programs for pre-college teachers will enhance the interests of their students in science, engineering, and the environment, and will hopefully direct more motivated students to pursue higher education in environmental engineering.