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

Abstract

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® 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.