Energy Aspects of Implementing Very High Gravity Fermentation Technology in Industrial-Scale Bioethanol Production

This study aims to evaluate and analyse industrial-scale data regarding the relationship between energy consumption (during distillation, rectification, and sorption dehydration) and ethanol concentration in fermented worts derived from corn, sorghum grain, and pea fractionation waste.

Technological parameters of very high gravity fermentation in industrial bioethanol production were investigated, while energy resource consumption was monitored using automatic process control system devices. Particular attention was paid to assessing heat energy consumption during distillation at varying ethanol concentrations in the fermentation medium.

The final ethanol concentration in the fermented wort increased from 13.5% to 17.5% v/v. At an ethanol concentration of 17.2±0.4% v/v, the total specific boiler steam consumption was 1.84±0.10 t/m³ of bioethanol, including the steam required for wort preparation. The average specific electricity consumption was 212 ± 14 kWh/m³ of bioethanol.

The specific boiler steam consumption for distillation, rectification, and sorption dehydration decreased from 2.66 t/m³ of bioethanol for a fermented wort with 14.0% v/v ethanol to 1.14 t/m³ for a fermented wort with 17.0% v/v ethanol. Similarly, at the distillation stage alone, specific boiler steam consumption was reduced from 1.60 t/m³ of bioethanol at 14.0% v/v ethanol to 0.47 t/m³ at 17.0% v/v ethanol.

Increasing the final ethanol concentration in the fermented wort from 14% to 17% v/v reduced the practical specific steam consumption within the distillation, rectification, and sorption dehydration by a factor of 2.3. These steam savings are primarily driven by a 3.4-fold reduction in energy consumption during the distillation stage alone.