Assessment of the thermodynamic performance improvement of a typical sugar mill through the integration of waste-heat recovery technologies

The cogeneration system is the most inefficient unit a typical sugar mill. This paper evaluates the improvements in the exergy performance of a sugar-mill cogeneration system, through the integration of the absorption heat pump (AHP) and the organic Rankine cycle (ORC) technologies for waste-heat recovery. The cogeneration system was simulated in Aspen Plus (R) process simulator and its thermodynamic performance determined through exergy analysis. In addition to providing an alternative cooling for the mill, the AHP integration minimized the irreversibility of the deaerator, sugar-drying unit and the overall system by 51%, 76% and 0.14%, respectively, saving 0.83% of total bagasse combusted. The ORC increased the cogeneration system's exergy efficiency by 1.7% by generating green electricity up to 10% of the cogeneration capacity. The AHP and ORC were economically feasible with payback periods of 8.3 years and 6.3 years, respectively. This paper provides basis for waste-heat recovery based exergy improvement studies in other process industries.