Application of Kalina cycle for augmenting performance of bagasse-fired cogeneration plant of sugar industry

Abstract

Power generation through bagasse-fired cogeneration plants is a common practice in sugarcane producing countries. The exergy-based analysis of a 16 MW grid-connected cogeneration plant of a sugar factory situated in India carried out by the author earlier and published as a separate paper, had disclosed that 6.34% of fuel energy and 5.20% of fuel exergy were lost through the flue gases. To utilize a part of this waste heat for conversion into electricity, in this paper, Kalina cycle is theoretically integrated with the considered plant. The sulphuric dew point is estimated to be 100.25 °C. Hence, to prevent acid condensation from exhaust gases, the exhaust heat can be safely utilized up to a temperature of 105 °C. Keeping ammonia-mass fraction at 0.8 and turbine inlet pressure at 4000 kPa, the net power output of the integrated plant is found to increase by 375.2135 kW thereby increasing the overall energy and exergy efficiencies of cogeneration by 0.3819% and 0.3150% respectively. The plant currently uses bagasse containing 50% moisture. If bagasse is completely dried by suitable means, power output will further increase by 3531.5 kW increasing the cogeneration energy and exergy efficiencies further by 3.5948% and 2.9630%.