A new economizer system was developed for a 600 MW power plant to control exhaust flue gas temperature. By using this system, the flue gas temperature entering the electrostatic precipitator can be reduced to 95°C, improving unit efficiency and reducing fuel consumption. Compared to traditional systems, this new system can save even more fuel. The system can actively control the exhaust flue gas temperature by adjusting the bypass flue gas ratio, leading to better efficiency in different conditions.