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dc.contributor.authorShen, Jiachengen_US
dc.date.accessioned2014-03-14T20:21:10Z
dc.date.available2014-03-14T20:21:10Z
dc.date.issued2008-12-19en_US
dc.identifier.otheretd-12262008-144226en_US
dc.identifier.urihttp://hdl.handle.net/10919/30264
dc.description.abstractIn this study, the hydrolytic kinetics of mixtures of cotton gin waste (CGW) and recycled paper sludge (RPS) at various initial enzyme concentrations of Spezyme AO3117 and Novozymes NS50052 was investigated. The experiments showed that the concentrations of reducing sugars and the conversions of the mixtures increased with increasing initial enzyme concentration. The reducing sugar concentration and conversion of the mixture of 75% CGW and 25% RPS were higher than those of the mixture of 80% CGW and 20% RPS. The conversion of the former could reach 73.8% after a 72-hour hydrolysis at the initial enzyme loading of 17.4 Filter Paper Unit (FPU)/g substrate. A three-parameter kinetic model with convergent property based on enzyme deactivation and its analytical expression were derived. Using nonlinear regression, the parameters of the model were determined from the experimental data of hydrolytic kinetics of the mixtures. Based on this kinetic model of hydrolysis, two profit rate models, representing two kinds of operating modes with and without substrate recycling, were developed. Using the profit rate models, the optimal enzyme loading and hydrolytic time could be predicted for the maximum profit rate in ethanol production according to the costs of enzyme and operation, enzyme loading, and ethanol market price. Simulated results from the models based on the experimental data of hydrolysis of the mixture of 75% CGW and 25% RPS showed that use of a high substrate concentration and an operating mode with feedstock recycle could greatly increase the profit rate of ethanol production. The results also demonstrated that the hydrolysis at a low enzyme loading was economically required for systematic optimization of ethanol production. The development of profit rate model points out a way to optimize a monotonic function with variables, such as enzyme loading and hydrolytic time for the maximum profit rate. The study also investigated the ethanol production from the steam-exploded mixture of 75 wt% cotton gin waste and 25 wt% recycled paper sludge at various influencing factors, such as enzyme concentration, substrate concentration, and severity factor, by a novel operating mode: semi-simultaneous saccharification and fermentation (SSSF) consisting of a pre-hydrolysis and a simultaneous saccharification and fermentation (SSF). Four cases were studied: 24-hour pre-hydrolysis + 48-hour SSF (SSSF 24), 12-hour pre-hydrolysis + 60-hour SSF (SSSF 12), 72-hour SSF, and 48-hour hydrolysis + 12-hour fermentation (SHF). SSSF 24 produced higher ethanol concentration, yield, and productivity than the other operating modes. The higher temperature of steam explosion favored of ethanol production, but the higher initial enzyme concentration could not increase the final ethanol concentration though the hydrolytic rate of the substrate was increased. A mathematical model of SSSF, which consisted of an enzymatic hydrolysis model and a SSF model including four ordinary differential equations that describe the changes of cellobiose, glucose, microorganism, and ethanol concentrations with respect to residence time, was developed, and was used to simulate the data for the four components in the SSSF processes of ethanol production from the mixture. The model parameters were determined by a MATLAB program based on the batch experimental data of the SSSF. The analysis to the reaction rates of cellobiose, glucose, cell, and ethanol using the model and the parameters from the experiments showed that the conversion of cellulose to cellobiose was a rate-controlling step in the SSSF process of ethanol production from cellulose.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartdissertation.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectProfit rateen_US
dc.subjectDiffusivity.en_US
dc.subjectKinetic modelen_US
dc.subjectSimultaneous saccharification and fermentationen_US
dc.subjectEnzymatic hydrolysisen_US
dc.subjectEthanolen_US
dc.subjectCelluloseen_US
dc.subjectDeactivationen_US
dc.subjectOperating modeen_US
dc.subjectRecycled paper sludgeen_US
dc.subjectCotton gin wasteen_US
dc.titleModeling and Production of Bioethanol from Mixtures of Cotton Gin Waste and Recycled Paper Sludgeen_US
dc.typeDissertationen_US
dc.contributor.departmentBiological Systems Engineeringen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineBiological Systems Engineeringen_US
dc.contributor.committeechairAgblevor, Foster Aryien_US
dc.contributor.committeememberWen, Zhiyouen_US
dc.contributor.committeememberZhang, Chenming Mikeen_US
dc.contributor.committeememberBarbeau, William E.en_US
dc.contributor.committeememberHelm, Richard Fredericken_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12262008-144226/en_US
dc.date.sdate2008-12-26en_US
dc.date.rdate2009-02-03
dc.date.adate2009-02-03en_US


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