Energy Conversion and Management: X (Aug 2022)
Improvement of conventional design of lignite-fired thermal power plant by integrating steam-air preheater and flue gas dryer
Abstract
The conventional design of thermal power plant uses regenerative feed water heating to increase the overall power plant efficiency. This method is limited by the number of feed water heaters and the amount of extracted steam supplied to each feed water heater. It is proposed in this paper that the improvement of the conventional design is possible by integrating steam–air preheater and flue gas dryer into the power plant. Extracted steam is used to increase air temperature in steam–air preheater before air is sent to boiler. Due to increased air temperature at the boiler inlet, flue gas temperature at the boiler outlet is increased. Flue gas dryer is used to decrease exhaust flue gas temperature to 150 °C. In doing so, the fuel moisture content is reduced, which results in increased boiler efficiency and increased overall power plant efficiency. A case study of the design of a 500-MW lignite-fired subcritical power plant is considered to demonstrate that the integration of steam–air preheater and flue gas dryer increases the overall power plant efficiency. Furthermore, this integration is shown to be economically justified because of a low value of levelized cost of electricity.
