Performance Improvement and Repowering Strategies for an Existing Sugarcane Cogeneration Plant: Energy, Exergy, Economic and Environmental Assessment

This study evaluates performance-improvement and repowering strategies for an existing sugarcane cogeneration plant in Espírito Santo, Brazil, using field data and thermodynamic simulations performed with Thermoflex and EES software. The current operating condition was adopted as the Base Case and compared with three progressively more intensive scenarios. Increasing steam generation from 75 to 110 t/h raised net electrical power from 10.800 to 18.633 MW, while the simulated condenser steam flow reached 41.3 t/h, slightly exceeding its 40 t/h nominal capacity. Operation at the nominal boiler capacity of 150 t/h increased net electrical power to 32.560 MW and required additional condensation capacity. A repowering configuration at the same steam-generation rate, but with higher steam pressure and temperature and reheating, further increased net electrical power to 38.304 MW and net electrical efficiency from 23.12% to 27.44%. Exergetic efficiency increased from 23.50% to 26.85%, while total combined exergy destruction and losses decreased from 147.698 to 140.554 MW. Specific direct CO2 emissions decreased from 2.962 to 1.468 tCO2/MWh between the Base Case and Scenario 3. The revised incremental economic assessment, based on 3300 operating hours per year, resulted in an NPV of US$6.88 million and a discounted payback of 0.67 years for the transition to Scenario 2, whereas the repowering investment resulted in an NPV of −US$27.44 million. The results distinguish capacity recovery from technological repowering and show that higher thermodynamic performance does not necessarily correspond to greater economic attractiveness.