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Entropy analysis as a tool for optimal sustainable use of biorefineries
University of Borås, School of Engineering.
2007 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [en]

The biorefinery concept is attractive. Increasing international concerns over issues such as climate change have led to political as well as social pressures for a shift from fossil fuels to renewable resources and biomass is one abundant renewable resource. Biomass has the potential of supplying many of the fuels and chemicals which are currently dependent on petroleum. Much development is still needed in the field of biorefineries and a systematic approach to evaluate and compare process technologies and to suggest optimizations seems necessary. The objective of this thesis is to develop entropy analysis as a possible evaluation tool for optimization of biorefinery processes. This is a new application of entropy analysis which is rarely discussed in the literature. The scientific basis of the entropy analysis is described and the proposed methodology is explained. The position of entropy analysis among other system analysis tools such as exergy analysis and life cycle assessment is discussed along with entropy analysis earlier applications. A case study is introduced which is the IBUS (Integrated Biomass Utilization System) project in Denmark. The idea in IBUS is to integrate the biomass plant with a power plant to utilize the surplus steam from the power plant for the internal use of the biorefinery. The suggested method of entropy analysis is applied to this case study to compare different processes for production of ethanol along with solid biofuel and animal feed from Danish wheat straw. The evaluation is a gate to gate analysis in which production of energy carriers are also included in addition to biorefining of wheat straw. A parallel life cycle assessment study with equivalent system boundaries is also carried out to compare the results with a conventional environmental systems analysis method. The results from the entropy analysis of the IBUS case study show that fermentation of C5 and C6 sugars by yeast is the most efficient process thermodynamically while fermentation of only C6 sugars by yeast is the least efficient among the three cases studied. Integration of the biorefinery with a coal fired CHP plant is identified as a wise choice by the results of the entropy analysis method. For the IBUS process alternatives investigated in this study, the entropy results and the LCA results (aggregated environmental load) are in correlation; entropy results are consistent with weighting results based on two different weighting methods namely Eco indicator 99 and EPS 2000. Entropy generation is also in correlation with production cost for the processes analyzed in this evaluation. Another observation is that cooling in the biorefining process contributes highly in the generation of entropy. This potential improvement option is not surfaced by the LCA conducted. The potential for further investigation and development of the tool is recognized reflecting on some interesting observations in the results. Improvement of the tool is highly possible for example by supplementing other implications of entropy in process design such as "waste potential entropy" concept which is developed as an eco-toxicity measure.

Place, publisher, year, edition, pages
University of Borås/School of Engineering , 2007.
Series
Magisteruppsats
Keywords [en]
biomass conversion, biorefinery, entropy, life cycle assessment, second law analysis, thermodynamic optimization
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:hb:diva-18679Local ID: 2320/2934OAI: oai:DiVA.org:hb-18679DiVA, id: diva2:1310613
Note
Uppsatsnivå: DAvailable from: 2019-04-30 Created: 2019-04-30

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