GOALI: Segregation and Elutriation of a Binary Mixture

目标：二元混合物的分离和淘析

• 批准号: 0650893
• 负责人: Christine Hrenya
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0650893&HistoricalAwards=false
• 关键词: GOALI; Segregation; Elutriation; Binary; Mixture

National Science Foundation - Division of Chemical &Transport Systems Particulate & Multiphase Processes Program (1415)Proposal Number: 0650893Principal Investigators: Hrenya, ChristineAffiliation: University of Colorado at BoulderProposal Title: GOALI: Segregation and Elutriation of a Binary MixtureGas solid flows are ubiquitous, though not well understood. A study of solids processing plants indicates that 80% of the plants experienced solids handling problems such as pipe blockage and that the performance of such operations was typically only 40-50% of design. Furthermore, even "reliable" empirical correlations for fluid catalytic cracking units are often inadequate. The proposed GOALI effort is targeted at advancing the fundamental knowledge associated with a phenomenon that is typically handled empirically, namely elutriation. Elutriation refers to the carryover of fines in a bubbling, gas-fluidized bed. Although more than 50 elutriation correlations have been proposed in the literature over the last two decades, the disagreement between experiments and empirical prediction is typically over 100%, and in some cases may differ by a factor of more than a hundred.Intellectual MeritTo better predict the elutriation phenomenon, a combined modeling and experimental effort is proposed. Research on the bubbling bed (dense) and freeboard (dilute) regions will be pursued in parallel. Two outstanding questions will drive this effort: (i) what physical mechanism(s) lead to the observed segregation (de-mixing) and bubbling patterns in the bubbling bed region, and (ii) what physical mechanisms lead to the counter-intuitive behavior observed in the freeboard region in which the addition of fines to the bed is known to increase the elutriation rate of relatively coarse particles (i.e., particles which have a terminal velocity that is greater than the superficial velocity at which the bed operates)? It is hypothesized that particle particle interactions play a key role in both regions. Similarly, a plausible explanation for the counter-intuitive behavior observed in the freeboard is the expected preferential collision of fine particles with the bottom half of upwardly moving coarse particles (since the fines travel at a higher velocity due to their reduced mass). This additional collisional force on the bottom of the coarse particles is expected to lead to their increased elutriation. The hypotheses will be tested by means of a two-fluid gas-solid model based on a new kinetic theory for mixtures that does not involve any of the assumptions of previous theories (nearly elastic, equipartiton of energy, Maxwellian velocity distribution). Model validation will be carried out with measurements that are both local and species-specific (species velocities and concentrations). A new probe will be developed that is both capable of measuring species velocities and concentrations and is adaptable to an industrial setting. The resulting data will represent the first detailed measurements of segregation and elutriation of two non-cohesive materials, and will be the first to characterize the impact of non-uniform particles on bubbling behavior. Furthermore, the model data comparison will be the first attempt to predict elutriation based on fundamentals (no adjustable parameters).Broader ImpactsThis work is motivated by complementary interests of each partner: the University of Colorado (polydispersity and segregation), Millennium (elutriation modeling), and PSRI (fluidization instrumentation and elutriation). This interdisciplinary team has over 50 years of experience in particle technology. Industry-university interaction will be promoted via industrial internships of PhD students involved in the project, co-advising of PhD students, and regular meetings and telecons. The results will be shared with the public using standard methods (conference presentations, peer-evaluated publications, website, etc.) and via the incorporation of the new model into MFIX (www.mfix.org), an open-source, no-cost CFD code which all of the PI's have extensive experience with. The proposed work will also involve the training student researchers in the area of particle technology, which has been identified as a national need. The PI has a strong record in involving undergraduates in research and promoting a diverse workforce.

美国国家科学基金会-化学运输系统分部颗粒多相过程计划（1415）提案编号：0650893主要研究者：Hrenya，Christine所属机构： 科罗拉多大学博尔德分校提案题目：目标：二元混合物的分离和淘析气固两相流是普遍存在的，尽管还没有得到很好的理解。一项对固体处理厂的研究表明，80%的工厂遇到了固体处理问题，如管道堵塞，这些操作的性能通常只有设计的40-50%。此外，对于流化催化裂化装置，即使是“可靠的”经验关联式也常常是不够的。拟议的GOALI努力旨在推进与通常凭经验处理的现象（即淘析）相关的基本知识。淘析是指在鼓泡气体流化床中携带细粒。虽然在过去的二十年里，在文献中已经提出了超过50个淘析相关性，实验和经验预测之间的分歧通常超过100%，在某些情况下，可能会有不同的因素超过100.Intellectual MeritTo更好地预测淘析现象，提出了一个相结合的建模和实验的努力。对鼓泡床（密相）和稀相区的研究将同时进行。两个突出的问题将推动这一努力：（i）什么物理机制导致在鼓泡床区域中观察到的分离（分层）和鼓泡模式，以及（ii）什么物理机制导致在稀相区中观察到的反直觉行为，其中已知向床中添加细粉增加相对粗颗粒的淘析速率（即，具有大于床操作的表观速度的终端速度的颗粒）？据推测，粒子粒子相互作用在这两个区域中起着关键作用。类似地，对于在干舷中观察到的反直觉行为的合理解释是细颗粒与向上移动的粗颗粒的下半部分的预期优先碰撞（因为细颗粒由于其质量减小而以更高的速度行进）。这种作用在粗颗粒底部的额外碰撞力预计会导致粗颗粒淘析增加。这些假设将通过一种基于新的混合物动力学理论的双流体气-固模型进行测试，该模型不涉及以前理论的任何假设（近弹性、能量均分、麦克斯韦速度分布）。将利用当地和特定物种的测量值（物种速度和浓度）对模型进行验证。将开发一种新的探针，既能够测量物种的速度和浓度，并适应于工业环境。所得数据将代表两种非粘性材料的分离和淘析的第一次详细测量，并且将是第一次表征不均匀颗粒对起泡行为的影响。此外，模型数据比较将是第一次尝试预测淘析的基础上的基本面（没有可调参数）。更广泛的影响这项工作是由每个合作伙伴的互补利益的动机：科罗拉多大学（多分散性和偏析），千年（淘析建模）和PSRI（流化仪器和淘析）。这个跨学科的团队在粒子技术方面拥有超过50年的经验。将通过参与该项目的博士生的工业实习、博士生的共同咨询以及定期会议和电话会议来促进产学互动。将使用标准方法（会议演示、同行评估出版物、网站等）与公众分享成果。并通过将新模型并入MFIX（www.mfix.org），MFIX是一个开源的、免费的CFD代码，所有PI都有丰富的经验。拟议的工作还将涉及培训粒子技术领域的学生研究人员，这已被确定为国家的需要。PI在让本科生参与研究和促进多元化劳动力方面有着良好的记录。