Perpustakaan Digital ITB

Exhaust flue gas in coal-fired power plants is a rich low-temperature waste heat source, which its lost energy is a considerable amount among the losses of power generating unit. Furthermore, Organic Rankine Cycle (ORC) have been demonstrated as promising technology for low-temperature heat recovery. In this work, a certain amount of exhaust flue gas of 350 MW steam power plant in West Jawa island is extracted for heating the pressurized hot water that is the heat source of ORC used to generate electricity. After releasing the heat via fin-tube heat exchanger, the exhaust flue gas is cooled down from 157.56 oC to 120 oC, which is limited by acid dew point temperature, and it provide minimum available heat 10.825 MWth when steam power plant is operated at load 50% TMCR. The maximum used heat and gross power output of heat recovery plant is totally calculated based on the specification of selected ORC manufacturer. Moreover, simulating any heat exchanger in the system by using HTRI program, designing ducting system and pipe sizing are performed in order to estimate all kind of losses used for calculating consumed power of circulating pump and additional fans. Simultaneously, to obtain the net power output of heat recovery plant as high as possible, variating width (or lengthening tubes) of fin-tube heat exchanger matches with each of four ORC models with different operating performance is analyzed. With fixing the height of fin-tube heat exchanger at 5.0 m, and changing the width of it from 5.0 m to 6.5 m, the losses of heat recovery plant is reduced when the width is longer. Anyways, an ORC model which is operated with 150 oC heat source matches with 6.5 m width of the heat exchanger generated not only the maximum gross power (1250 kW) but also the highest net power (959.035 kW), and it requires 42.998 billion IDR of investment cost which is the highest price among the total case studies in the work. Therefore, the most appropriate matching between the width of fin-tube heat exchanger and ORC model will be considered after getting the result of analyzing net present value (NPV) for each matching. According to techno-economic study, for 5.0 m width of heat exchanger, an ORC model operated with 140 oC heat source and 4000 kWth input power exhibits the highest NPV with 1.460 billion IDR while another ORC model which is operated with 150 oC heat source represents the highest NPV with 1.967 billion, 3.047 billion, and 3.635 billion IDR, for case 5.5 m, 6.0 m, and 6.5 m width of heat exchanger respectively. These systems provide the internal rate of return (IRR) more than 12% in case they will be operated in 12 years of life cycle cost, and their payback period is in the fifth year.