Design and practice of flue gas deep cooling device for energy saving and emission reduction

Aiming at the problem that at the Ningxia Daba 320MW Coal-fired Power Plant, where is a higher flue gas temperature and a greater difference of the outlet flue gas temperature, we have made an modification of the tail flue gas duct by installing a gas deep cooling device to recover the waste heat and heat the condensed water. We have depicted the general layout scheme of the device and the research results on key technology of low-temperature corrosion and deposited ash abrasion. In the device, the H-type finned tubes are used as the heat transfer components. The trial operation shows that through the installation of the deep cooling device with varying pitches, the inlet temperature of the electrostatic precipitator decreases by 25°C and the gas temperature difference is eliminated. Under the load of 300MW, the turbine heat rate decreases by 40.3kJ/kWh, the unit coal consumption rate reduces by 1.491g/kWh, and the power supply coal consumption decreases by 1.425g/kWh. The system can save the amount of the cooling water for desulfurization and reduce the emission of CO₂, so it is able to realize more economic and safe operation of the generating unit under various loads.