Techno-economic analysis of the lignite-fired power plant integrated with a steam or flue gas dryer

Abstract

Lignite is considered as an raw energy material with abundant supply worldwide. However, power plants that directly fire lignite exhibit low efficiency, which can be improved by applying lignite pre-drying technologies. Lignite-Fired power plants integrated with a steam or flue gas dryer (SPLPS or FPLPS) are designed and optimized. Previous studies mainly focused on the thermodynamic performance and techno-economic analyses of single drying technology. However, sensitivity analyses of parameters are disregarded in the techno-economic analysis. Therefore, system configurations are optimized in this study, and different drying technologies are subsequently compared on the basis of their techno-economic performance. Moreover, the sensitivity analyses of key parameters are investigated. Optimization results show that the steam extraction pressure of SPLPS should not be substantially low, and optimum extraction should be performed at steam turbine 4# regenerative extraction (0.9539 MPa, 360.9 °C) or 5# (0.3758 MPa, 249.6 °C). This approach differs from the thermodynamic performance presented in previous studies. Moreover, the detailed optimization strategy of SPLPS is realized on the basis of net present value (NPV) and payback period. The comparison results show that the maximum NPV of FPLPS would be 9.5 million USD more than the earnings from a conventional lignite-fired power system (CLPS), whereas that of SPLPS would be 40.1 million USD more than the earnings from CLPS. However, the economic benefits of FPLPS and SPLPS can be reversed with the fluctuation of parameters based on sensitivity analyses.