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，增加国内产业，并通过减少不可再生来源产生的二氧化碳数量来帮助缓解全球变暖。我们目前大约30%的运输燃料使用量可以被来自木质纤维生物质的生物燃料所取代，这些生物燃料使用的是“生物精炼”过程。(木质纤维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，浓缩生物质是一种非常粘滞的非牛顿复杂流体，这给生物质的工业化加工带来了挑战。智力优势：生物质流动表现出各种有问题的现象，包括高屈服应力、可压缩性、非均质性和不稳定性。拟议工作的总体目标是开发浓缩生物质流动的模型，以捕捉所有相关和有问题的现象。拟议的研究将首次为设计有效的生物质运输过程提供必要的建模、理论和计算框架。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，然后在更复杂的加工几何形状中建立；(2)确定重现观测和预测流动必须包括的模型特征和物理性质；(3)将流动模型移植到开源计算流体力学包中，以便模型可以用于更复杂的流动。这项工作还将揭示潜在现象的机制，如不仅在生物质加工中，而且在其他流变性复杂材料中出现的不均匀和不稳定性。虽然本工作的重点是密度生物质悬浮液中的动量传递及其与浓度变化的耦合，但这项工作也是预测生物质流动过程中热量和质量传递的必要的第一步。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的流动反应堆，这一点尤其重要。广泛的影响：拟议的工作将在几个层面上产生影响。它将改善具有国家(甚至全球)技术、经济和社会重要性的一类工艺的工程知识库。一名研究生和几名本科生将接受进入这一领域的培训，并获得专业知识，为基本理解复杂流体的流变学和流体动力学做出贡献。拟议的研究与PI的教育努力高度协同，为大学的一年级课程做出了贡献。该项目的主要目标之一是通过说明工程学的更多人道主义影响，招募和留住妇女和其他代表性不足的群体进入工程学。建议的工作将通过范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.