Design and analysis of a combined Rankine cycle for waste heat recovery of a coal power plant using LNG cryogenic exergy
- Design and analysis of a combined Rankine cycle for waste heat recovery of a coal power plant using LNG cryogenic exergy
- 이웅; Keonhee Park; Yeong Su Jeong; Sangho Lee; Chonghun Han
- Issue Date
- Industrial & engineering chemistry research
- VOL 53, NO 23-9824
- In this study, a combined Rankine cycle was modeled and optimized. This process consists of a coal combustion unit, a steam cycle, a CO2 capture process, a gas conditioning process, and a CO2 organic Rankine cycle (ORC). This process is able to extract additional power without consuming additional fossil fuel by integrating the CO2-ORC with the steam cycle and a liquefied natural gas (LNG) evaporation process. Unlike conventional ORC, the CO2-ORC utilizes the low grade waste heat only for super heating of working fluid, while the main evaporation process is achieved by seawater. The CO2 condensation process in the ORC takes place at a temperature lower than the ambient temperature by coupling with the LNG evaporation system as a cold sink. Furthermore, a fraction of liquefied CO2 is purged for the sequestration. Therefore, CO2 liquefaction can be achieved without an additional refrigeration cycle. This process not only produces more power with the same fuel consumption but also reduces CO2 removal energy. The gross power is increased from 42.21 to 90.54 MWe compared with the conventional power plant, and total CO2 removal energy is decreased about 9%. The optimum design and operating conditions were also obtained through parameter sensitivity analysis. The power reduction of the proposed process resulting due to the CO2 capture process installation was identified as 19.3%. However, the net power generation is about 73% higher than that of the conventional power cycle even without CO2 capture.
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