Removing Sludge from B Molasses at the Providencia Sugar Mill Distillery: Performance Evaluation and Proposed Operating Alternative

Abstract

Different studies have demonstrated the effect of organic acids and minerals on the decrease of ethanol production by yeast fermentation. Other impacts have been observed at the operational level, such as increased consumption of inputs, higher occurrence of fouling in equipment, more frequent episodes of microbial contamination or difficulties in handling by-products, among others. Since 2018 these adverse effects have been increasingly observed in Colombia’s sugarcane agro-industrial sector. The sludge present in the raw material (cane molasses) is one of the sources of microbial contamination by lactic acid bacteria, acetic acid bacteria, and wild yeasts. The Providencia Sugar Mill located in rural El Cerrito, Department of Valle del Cauca, Colombia, accordingly implemented in 2011 a sludge removal technology by sedimentation, improving the operating conditions of equipment such as plate heat exchangers, pipes and mash column. However, the increase in concentrations of organic and inorganic impurities in the cane molasses prompted the study of strategies to mitigate these sources of impact on the fermentation process. Laboratory tests indicated that temperature was the variable that had the greatest impact on the removal of insolubles. Under the most optimal conditions possible, the decrease in insolubles was 74%, with decreases of 15% in ashes, 27.4% in calcium, 15.4% in magnesium and 4.8% in potassium as well. Laboratory results were then validated on an industrial scale, indicating that a 86% decrease in turbidity was obtained with operating temperatures ≥ 75 °C.