THERMOECONOMIC ANALYSIS OF A COGENERATION THERMAL POWER PLANT USED IN A SUGAR INDUSTRY

Abstract

Thermoeconomic analysis of a cogeneration thermal power plant used in a sugar industry consists of exergy analysis and thermoeconomic evaluation of the sugar plant. Exergy analysis of a sugar plant includes exergy. analysis of different components (e.g. boiler, turbine, evaporator, juice heater) where heat exchange takes place. Process analysis based on exergy analysis gives better insight on how the quality of energy degrades through the process. Exergy analysis of a sugar processing plant determines how exergy loss is taking place in different plant components as well as different process equipments. Thermoeconomic evaluation directly shows the cost flow through each individual component as well as through overall system. It also identifies the hidden cost (cost rate associated with exergy destruction) of individual component. Finally the thermoeconomic factor suggests what type of changes should be implemented to a component to optimize the cost flow rate through overall system. In this report a sugar processing plant having capacity of 6250 TCD (Ton Crushed Per Day) has been analyzed. The results of exergy analysis show that, there is high rate of exergy loss in boilers (40.79 MW for boiler I and boiler 2 and 45.73 MW for boiler 3) and at the starting part of evaporation of juice (14.91 MW for semi kestner). From the thermoeconomic evaluation it is noticed that the value of exergoeconomic factor is higher for turbines. Exergoeconomic factor, f, for turbine 1, 2 and 3 is 93.79%, for turbine 4 is 87.79% and for turbine 5 is 91.40%. The recommended value of exergoeconomic factor is 75% [12]. This suggests that the overall system can be cost optimized by decreasing the capital cost of the turbines. Iterative cost optimization has also been done for the overall system and it is found that the optimum value of pressure and temperature at the inlet of the turbines should be 42.11 bar and 405°C respectively. The cost optimized exergetic efficiency of the turbines is 72.64% and for boilers is 36.51%. By cost optimization the cost flow rate of product is reduced by.Rs. 1.09 lacs per year.