Abstract

This study aims to conduct a performance evaluation of a 135 MW Circulating Fluidized Bed (CFB) Coal Based Thermal Power Plant using exergy analysis and use these assessments in order to provide an optimum operation of the said plant. The study includes on determining the effects of ambient condition on the exergy analysis of the plant. The necessary parameters such as temperature, pressure and mass flow rates were collected from the DCS (Distributed Control System) of the plant. These parameters are then inputted in the excel file prepared by the proponent in order to arrive at necessary thermodynamic values. The results in the exergy analysis of the plant showed that most of the exergy losses occur in the boiler with a total of 172222.8 kJ/s under low temperature ambient and 182602.3 kJ/s at high temperature ambient. The high exergy loss in boiler is caused by unutilized heat that was not fully transferred in to turbine cycle system and is just venter out in the atmosphere. Turbine cycle exergy only accounts to 5 to 6 percent of the total initial exergy available. Most of these exergy losses are located at IP/LP turbine (8564.64 kJ/s), condenser (4818.07 kJ/s), cold reheat pipe (4690.16 kJ/s), HP turbine (1697kJ/s) and Deaerator (1055.82 kJ/s). Moreover, based the exergetic efficiency, most of the components in the turbine cycle that involve phase change are most likely to have low efficiency these include the boiler (50.97%), condenser (42.68%), gland steam cooler (75.34%) and LPH no.7 (13.46%). The effect of ambient temperature on the generation of irreversibility in the plant is considerable. During high ambient temperatures, the boiler produces high irreversibility than that of the low ambient temperatures. However, if we look into the turbine cycle side, the most irrversibilities are seen during low ambient conditions which are around 6.54 percent whilst the hotter ambient condition poses only a tad lower value of 5.79 percent. The optimized parameter in maximizing the load is suggested on the results which are: Unit load = 40 MW and main steam temperature = 530 Mpa. Heat exchange between the component and the system is a significant part in the exergy analysis of the plant. Thus an exact approximation of the actual heat transfer would decently make the exergy analysis more accurate. Moreover, the program for thermodynamic value determination can be made from other programming platform aside from excel in order to create a faster generation of data and can be easily organize accordingly. Lastly based on the results provided by the exergy analysis on the plant, it recommended to formulate plans for improvements on plant components with high exergy loses especially the cold reheat pipe.

Keywords: Circulating Fluidized Bed (CFB); Distributed control system; Exergy; Exergy loss; Exergetic efficiency; Irreversibility