engleski

Optimization of CCPP's Bottom Cycle by using Organic Working Fluids – Exergoeconomic Optimization

One of the measures to reduce CO2 emissions and to increase energy efficiency is to improve thermodynamic efficiency of a combined cycle power plant by improving heat utilization in heat recovery steam generator. In this paper a mathematical model of a combined cycle power plant's bottom cycle was made. Heat recovery steam generator, which is a crucial element of bottom cycle, is modeled as a heat-exchanger's network. It consists of multi pressure levels and a reheater and uses organic working fluids in lower pressure levels. The mathematical model gives possibility that heat-exchangers, of each pressure level, can be in their mutual parallel and serial arrangement. In this paper exergoeconomic optimization was conducted. Optimization variables were heat-exchangers' layout and operating parameters of working fluid of each pressure level. The objective of optimization was minimization of exergy losses of a bottom cycle and minimization of investment costs. The genetic algorithm and gradient optimization methods were used as optimization tools. By reviewing literature it has not been found that any of the authors carried out simultaneous exergoeconomic optimization of HRSG heat-exchangers' layout and optimization of operating parameters of each pressure level while using organic fluids in lower pressure levels. Results show that lower exergy losses can be achieved by using organic fluids in lower pressure levels of heat recovery steam generator.

combined cycle ; steam cycle: heat recovery steam generator ; organic cycle ; exergoeconomic optimization ; heat-exchangers' network

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