Analysis and optimization of a coal-fired power plant under a proposed flue gas recirculation mode

• A new flue gas recirculation configuration in coal-fire power plant is proposed.
• The influence of flue gas recirculation on thermodynamics properties is analyzed.
• The key parameters are optimized and operation suggestions are provided.
• The proposed system can greatly improve off-design energy efficiency.

This study mainly investigated the influence of flue gas recirculation (FGR) on reheat steam temperature, boiler efficiency, and thermal efficiency in a proposed FGR scheme. The main parameters of the boiler are calculated under different modes on the basis of a 600 MW coal-fired boiler. Optimization is conducted, and the optimum recirculation rate and coal input are determined. Results from case study showed that under the same recirculation rate, the reheat temperature increases higher and the net coal consumption decreases more in the improved recirculation system than those in the traditional recirculation system. The key parameters, such as the FGR rate and coal feed rate are optimized. Under optimum recirculation rate and coal input conditions, the net coal consumption rate can be reduced by 2.35–2.60 g/(kW h) compared with that obtained with the use of a conventional recirculation system. This net coal consumption rate can be reduced by 3.50–5.11 g/(kW h) compared with that obtained without gas recirculation system. For a better operation, lower recirculation rate and relative higher coal input are recommended under high-load conditions, whereas higher recirculation rate and relative lower coal input are appropriate for low-load conditions.