Exergy analysis of a new lignocellulosic biomass-based polygeneration system

A new polygeneration system for production of ethanol, xylose, combined heat and power from lignocellulosic biomass is introduced as it may be much more competitive than those considered before. The polygeneration system is simulated by Aspen Plus based on mass and energy balances and evaluated from exergy point of view and the output value per unit of raw materials. The system can process corn cob 340,000 t/a with a production capacity of anhydrous ethanol 40,000 t/a and xylose crystals 51,600 t/a. The ratio of produced ethanol to dry biomass is 179.7 L/t. The output value per unit of raw biomass is much higher than other systems due to production of high value co-product xylose. The net energy ratio is 1.6 indicating the system has net energy gain. The power generation efficiency and thermal efficiency are 31.2% and 86.2%, respectively. The general exergy efficiency of the system is 62.8% and the largest irreversibility occurs in combined heat and power system (CHP). The work is valuable to find key unit of improving the process exergy efficiency and build an optimal energy network. Further work should take into account the process heat integration to improve the exergy efficiency of the system.