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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1184-A

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Exergy assessment of renewable electricity from sugarcane straw for improved energy integration of sugarcane biorefineries

Pablo SILVA ORTIZ, University of Campinas, Brazil
Daniel FLÓREZ-ORREGO, University of Sao Paulo, Brazil
Adriano PINTO MARIANO, University of Campinas, Brazil
Viatcheslav KAFAROV, Industrial University of Santander, Colombia
Silvio DE OLIVEIRA JUNIOR, University of Sao Paulo, Brazil
Rubens MACIEL FILHO, University of Campinas, Brazil

In 2018, the participation of renewable energy in the Brazilian domestic energy consumption achieved 45.3%, out of which 17.4% corresponds to sugarcane energy, whereas 10.7% is explicitly related to sugarcane bagasse. Sugarcane and straw (i.e., sugarcane tops, dry and green leaves) represent useful energy inputs to the Brazilian electricity mix, often used as supplementary fuels in the cogeneration units of sugarcane biorefineries. However, the collection and conversion of these energy resources are typically performed by using inefficient conversion systems (<30%), which impacts the overall performance of the production process. Hence, this work focuses on existing sugarcane mills and cogeneration systems, aiming to increase the surplus electricity commercialization. Simulation processes are employed to denote incremental modifications related to sugarcane straw recovery utilizing in the harvesting systems. In this context, a technical comparison concerning the exergy efficiency, unit exergy cost, and the irreversibility rate as thermodynamic criteria of these processes is performed to allow identifying potential improvements in the sugarcane mills. A sensitivity analysis is carried out considering the main parameters related to industrial plant scale, operating period, sugarcane straw consumption, and economic criteria to assess different scenarios. Preliminary results show that the techno-economic assessment of straw recovery through harvesting systems increases up to 30% the surplus electricity when it is considered the integration of sugarcane biorefineries with the maximum straw recovery fraction. Also, the increment in the exergy cost of the straw collection influences the extended exergy efficiency of the cogeneration unit and the whole sugarcane biorefinery, rendering this sector a decarbonization alternative for the Brazilian electricity mix.

Keywords: Exergy analysis, Sugarcane straw, Irreversibilities, Biorefinery performance, Biofuels production
Acknowledgment: The authors acknowledge the São Paulo Research Foundation (FAPESP) for grants 2017/03091-8. Furthermore, this work was performed within the framework of a BIOEN thematic research project, FAPESP process 2015/20630-4. Daniel Flórez-Orrego would like to acknowledge the National Agency of Petroleum, Gas, and Biofuels (ANP) and its Human Resources Program (PRH/ANP grant 48610.008928.99), and the Administrative Department of Science, Technology, and Innovation (COLCIENCIAS 646/2014). Lastly, Silvio de Oliveira Jr. also acknowledges the National Research Council for Scientific and Technological Development, CNPq (grant 304935/2016-6).