Heterogeneities and instabilities during flow processing of biomass

利用生物质作为能源可以帮助减少对进口石油和天然气的需求，改善农村经济，增加国内工业，并通过减少不可再生能源产生的二氧化碳量来缓解全球变暖。我们目前使用的运输燃料的大约30%可以被使用“生物精炼”过程的木质纤维素生物质的生物燃料所取代。（木质纤维素生物质不是食物供应的一部分。这种方法的商业化需要降低加工成本。提高固体浓度可以降低加工成本。然而，浓缩生物质是一种非常粘稠的非牛顿复杂流体，这使得生物质的工业加工具有挑战性。 智力优点：生物质流动表现出各种各样的问题现象，包括大的屈服应力，可压缩性，不均匀性和不稳定性。拟议工作的总体目标是开发浓缩生物质流动模型，以捕捉所有相关和有问题的现象。拟议的研究将首次提供有效的生物质运输过程的设计所必需的建模，理论和计算框架。具体目标是：（1）首先在简单的处理几何形状中，然后在更复杂的处理几何形状中，开发生物质的压力驱动流动的单流体和双流体模型;（2）确定必须包括以再现观察和预测流动的模型特征和物理性质;（三）将流动模型移植到一个开放源代码的计算流体力学软件包中，以便模型可以用于更复杂的流动。这项工作也将揭示潜在的机制例如在加工过程中不仅在生物质而且在其它流变学复杂材料中出现的不均匀性和不稳定性的现象。虽然本工作的重点是动量传输及其耦合到密集的生物质悬浮液中的浓度变化，这项工作也代表了预测生物质流动过程中的传热传质的必要的第一步。这一点尤其重要，因为目前正在开发复杂的流动反应器，用于高效、高通量地转化为高价值产品。更广泛的影响：拟议的工作将在多个层面产生影响。它将改善工程知识基础的一类过程中的国家（实际上是全球）的技术，经济和社会的重要性。一名研究生和几名本科生将接受进入这一竞技场的培训，并获得专业知识，为复杂流体的流变学和流体动力学的基本理解做出贡献。拟议的研究与PI的教育工作高度协同，为威斯康星州大学的新生课程做出了贡献，该课程名为"社会工程大挑战导论"，其主要目标之一是通过说明工程的更多人道主义影响来招募和留住妇女和其他代表性不足的群体。建议的工作将通过示例和项目主题出现在本课程中。

1336611KlingenbergUtilizing biomass as an energy source can help to reduce the need for imported oil and gas, improve rural economies, increase domestic industries, and aid in mitigating global warming by decreasing the amount of CO2 generated from nonrenewable sources. Roughly 30% of our current transportation fuel usage could be replaced by biofuels from lignocellulosic biomass using "biorefining" processes. (Lignocellulosic biomass is not part of the food supply.) Commercialization of such processes requires reducing the processing costs. Increasing the solids concentration can decrease processing costs. However, concentrated biomass, is a very viscous, non-Newtonian complex fluid, which makes industrial processing of biomass challenging. Intellectual Merit :Biomass flows exhibit a variety of problematic phenomena including large yield stresses, compressibility, heterogeneities, and instabilities. The overall goal of the proposed work is to develop models of the flow of concentrated biomass that capture all of the relevant and problematic phenomena. The proposed research will provide for the first time the modeling, theoretical and computational framework that is necessary for design of efficient biomass transport processes. The specific objectives are to: (1) develop one-fluid and two-fluid models of the pressure-driven flow of biomass first in simple, and then in more complex processing geometries; (2) determine the model features and physical properties that must be included to reproduce observations and predict flow; (3) port the flow models into an open source computational fluid mechanics package so that the models can be used in more complicated flows.This work will also shed new light on the mechanisms underlying phenomena such as heterogeneities and instabilities that arise in processing not only in biomass but other rheologically complex materials. While the focus of the present work is momentum transport and its coupling to concentration variations in dense biomass suspensions, this work also represents a necessary first step in predicting heat and mass transfer during biomass flows. This point is particularly important given the complex flow reactors that are being developed for efficient high-throughput conversion to high-value products.Broader Impacts :The proposed work will have impacts at several levels. It will improve the engineering knowledge base for a class of processes in an area of national (and indeed global) technological, economic and societal importance. A graduate student and several undergraduates will be trained for entering this arena, as well as gaining expertise and making contributions to the fundamental understanding of the rheology and fluid dynamics of complex fluids. The proposed research is highly synergistic with the PI's educational efforts in contributing to a freshman level course at Univ. of Wisconsin called "Introduction to Society's Engineering Grand Challenges", which has as one of its main goals to recruit and retain women and other underrepresented groups into engineering by illustrating the more humanitarian impacts of engineering. The proposed work will appear in this course via examples and project topics.