Heterogeneities and instabilities during flow processing of biomass

1336611 klingenberg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帮助缓解全球变暖。我们目前使用的运输燃料中，大约30%可以通过“生物精炼”过程，由木质纤维素生物质制成的生物燃料取代。（木质纤维素生物质不是食物供应的一部分。）这种工艺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，浓缩的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。智力优势：生物质流动表现出各种有问题的现象，包括大屈服应力、可压缩性、异质性和不稳定性。拟议工作的总体目标是开发浓缩生物质流动的模型，以捕获所有相关和有问题的现象。拟议的研究将首次提供建模、理论和计算框架，这是设计有效生物质运输过程所必需的。具体目标是：(1)首先建立简单的生物质压力驱动流动的单流体和双流体模型，然后是更复杂的加工几何形状；(2)确定模型特征和物理性质，这些特征和物理性质必须包括在重现观测和预测流动中；(3)将流动模型移植到一个开源的计算流体力学包中，使模型可以用于更复杂的流动。这项工作还将揭示在生物质和其他流变复杂材料的加工过程中出现的异质性和不稳定性等现象的机制。虽然目前工作的重点是动量输运及其与密集生物质悬浮液中浓度变化的耦合，但这项工作也代表了预测生物质流动过程中传热和传质的必要的第一步。考虑到正在开发的用于高效高通量转化为高价值产品的复杂流动反应器，这一点尤为重要。更广泛的影响：拟议的工作将在几个层面上产生影响。它将改善在国家（实际上是全球）技术、经济和社会重要性领域的一类过程的工程知识基础。一名研究生和几名本科生将接受培训，以进入这个领域，并获得专业知识，并对复杂流体的流变学和流体动力学的基本理解做出贡献。这项拟议中的研究与PI在威斯康星大学的一门名为“社会工程大挑战导论”的新生课程的教育工作高度协同，该课程的主要目标之一是通过说明工程的更多人道主义影响，招募和留住女性和其他代表性不足的群体进入工程领域。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.