Process Utility Performance Evaluation and Enhancements in the Traditional Sugar Cane Industry

Abstract: The need to achieve sustainable development has led to devising various approaches for the efficient utilization of natural resources. Renewable energy technology and energy efficiency measures feature prominently in this regard, and in particular for industries such as sugar production:  the sugar cane industry’s eponymous feedstock is a renewable resource, and mills have potential for increased energy savings via improvements to cogeneration units, electric drive retrofitting, and other measures.  The overall objective of this research work is to investigate different approaches of efficiency improvements for enhancing sugar cane conversion, thereby increasing the services obtained including surplus electric power delivery. Traditional sugar cane mills, i.e. those that lack modern components such as high-performance boilers and electric drives, are the focus of this investigation. System simulations show that modern mills generate more electrical power as compared to traditional mills, with power-to-heat ratios nearly one order of magnitude higher (i.e. 0.3-0.5).  Comparison of the thermodynamic performance of three retrofits showed that such modifications could raise the performance of traditional mills to approach those for their modern counterparts. Results for a base case traditional plant show that losses related to mechanical prime movers are high, since the mills and shredder are driven by steam and generate excess mechanical power. When considering press mill stoppages, steam is wasted during the ensuing fuel oil-fired start-up period. CO2emission for such transient conditions can be decreased owing via bagasse drying and storage.  In studying both energy and water impacts, a comparison of four technological improvements demonstrates benefits outside the crushing season for three scenarios: recovery of excess wastewater for enhanced imbibition; recovery of waste heat for thermally-driven cooling; and pelletization of excess bagasse. The fourth option, involving upgrading of the mill’s cogeneration unit, is advantageous for continuous surplus power supply.