Heterogeneities and instabilities during flow processing of biomass

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

1336611 Klingenberg Utilizing 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.