Thermodynamic and economic analysis on a two-stage predrying lignite-fueled power plant

ABSTRACT

In this study, an improved configuration of lignite-fueled power plant integrated with a two-stage predrying system was proposed. The predrying system mainly consists of two fluidized-bed dryers and an additional feed water heater. Lignite is dried successively in the exhaust gas dryer and steam dryer. With boiler exhaust gas being the heat source of the first stage dryer, waste heat of a fraction of the boiler exhaust gas can be used. The exhaust gas of the second stage dryer was considered to be water vapor and its latent heat can be recovered by the additional feed water heater. The thermodynamic and economic analysis show that with the lignite drying degree being 0.1, 0.2, and 0.3 kg/kg, the power generation efficiency of the proposed power plant is 1.45, 2.12, and 2.81% higher than that of the conventional lignite power plant, respectively. Moreover, the annual net economic benefit will be 1.34, 2.03, and 1.60 M$/a during the lifetime of the drying system. The annual net economic benefit is not necessarily higher with higher power generation efficiency.

KEYWORDS:

• Economic analysis
• lignite
• power plant
• thermodynamic analysis
• two-stage drying

Abbreviations::

• BEDPP, boiler exhaust gas drying power plant
• CLPP, conventional lignite power plant
• SEDPP, steam extraction drying power plant
• TSDPP, two-stage drying power plant

Additional information

Funding

The authors acknowledge financial support from the National Key R&D Program of China (2017YFB0602003).