Mass and Heat Integration in Ethanol Production Mills for Enhanced Process Efficiency and Exergy-Based Renewability Performance

Silva Ortiz Silva Ortiz,Maciel Filho Maciel Filho,Posada Posada

doi:10.3390/pr7100670

Silva Ortiz Silva Ortiz, Maciel Filho Maciel Filho + Show 1 more

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https://doi.org/10.3390/pr7100670

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Abstract

This paper presents the process design and assessment of a sugarcane-based ethanol production system that combines the usage of both mass and heat integration (pinch analysis) strategies to enhance the process efficiency and renewability performance. Three configurations were analyzed: (i) Base case: traditional ethanol production (1G); (ii) mass-integrated (1G2G); and (iii) mass and heat-integrated system (1G2G-HI). The overall assessment of these systems was based on complementary approaches such as mass and mass–heat integration, energy and exergy analysis, exergy-based greenhouse gas (GHG) emissions, and renewability exergy criteria. The performances of the three cases were assessed through five key performance indicators (KIPs) divided into two groups: one is related to process performance, namely, energy efficiency, exergy efficiency, and average unitary exergy cost (AUEC), and the other one is associated to environmental performance i.e., exergy-based CO2-equation emissions and renewability exergy index. Results showed a higher exergy efficiency of 50% and the lowest AUEC of all the systems (1.61 kJ/kJ) for 1G2G-HI. Furthermore, the destroyed exergy in 1G2G-HI was lower by 7% and 9% in comparison to the 1G and 1G2G cases, respectively. Regarding the exergy-based GHG emissions and renewability performance (λindex), the 1G2G-HI case presented the lowest impacts in terms of the CO2-equivalent emissions (94.10 gCO2-eq/MJ products), while λindex was found to be environmentally unfavorable (λ = 0.77). However, λindex became favorable (λ > 1) when the useful exergy of the byproducts was considered.

Highlights

Increasing global energy demand combined with global warming effects associated with greenhouse gas (GHG) emissions have accentuated the need to find more sustainable and environmentally friendly energy sources to replace fossil fuels [1]
The conventional system is compared to two levels of process integration by first doing mass integration and mass–energy integration for ethanol production and power generation based on the results of the key performance indicators (KPIs)
An exergy-based performance analysis was conducted from a cradle-to-gate approach. This analysis represented a trade-off between mass and heat integration options with respect to a conventional sugarcane plant using multiple KPIs, which combined exergy analysis, heat integration, and the renewability exergy approach

Summary

Introduction

Increasing global energy demand combined with global warming effects associated with greenhouse gas (GHG) emissions have accentuated the need to find more sustainable and environmentally friendly energy sources to replace fossil fuels [1]. In this context, biofuels could contribute as a player in achieving environmental goals and energy demand. One of the key factors to implement and consolidate a more efficient process in the biofuel sector is related to technological improvements in conventional biorefinery systems (i.e., mass and energy integration). In the particular case of ethanol production, the integration of second-generation processes into traditional ethanol mills (1G2G biorefineries) could increase its supply potential and process. To understand to what extended these processes could potentially be improved, mass and heat integration strategies are needed along with the development of suitable process performance indicators and renewability metrics

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Results

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