Views: 0 Author: Site Editor Publish Time: 2026-01-26 Origin: Site
A certain power plant is equipped with 2×135 MW ultra-high-pressure double-extraction heating turbine units. The boilers are designed with ultra-high-pressure parameters, single reheat, single furnace, balanced draft, natural circulation, and solid slag discharge circulating fluidized bed (CFB) technology. The plant operates two 440 t/h circulating fluidized bed boilers.
The boilers were originally designed to burn bituminous coal. Due to changes in fuel supply, the current operating condition has shifted to 100% lignite firing. Under this new coal quality, the boilers experience excessively high flue gas exhaust temperatures, resulting in increased exhaust heat losses and reduced boiler efficiency.
Lignite is characterized by:
High inherent moisture content
High volatile matter
Low lower heating value
These properties lead to higher flue gas volumes and elevated exhaust temperatures during boiler operation. As a result:
Flue gas heat loss increases significantly
Boiler thermal efficiency decreases
Unit coal consumption for power supply rises
To address these challenges and achieve energy-saving and environmental benefits, the power plant plans to implement heat-exchange-based flue gas waste heat recovery technology to recover waste heat from the flue gas of Boiler No. 1.
The retrofit adopts a high-efficiency flue gas waste heat recovery heat exchanger, installed in the boiler tail flue gas system. By cooling the high-temperature flue gas and transferring the recovered heat to the plant’s thermal system, low-grade waste heat is effectively utilized.
Recovered heat can be applied to:
Feedwater or condensate water heating
District heating or auxiliary heating systems
Overall improvement of the boiler thermal balance
Key technical features of the solution include:
Designed for lignite-fired CFB boiler conditions
Wear-resistant and corrosion-resistant heat exchanger structure
Optimized design to prevent low-temperature corrosion and ash fouling
Minimal additional flue gas pressure drop
No negative impact on boiler safety or stable operation
According to technical calculations and operational evaluations, the retrofit delivers clear energy-saving results:
Summer operating conditions:
Reduction in coal consumption for power supply of 3.206 g/kWh
Winter operating conditions:
Reduction in coal consumption for power supply of 2.76 g/kWh
By lowering the flue gas exhaust temperature and reducing exhaust heat losses, the boiler efficiency is significantly improved. Over long-term operation, this leads to substantial fuel cost savings and improved overall plant economics.
The flue gas waste heat recovery retrofit provides multiple benefits:
Improved boiler efficiency under lignite-firing conditions
Reduced standard coal consumption per unit of electricity generated
Lower fuel usage, contributing to reduced CO₂ and pollutant emissions
Enhanced adaptability of existing CFB boilers to low-grade coal
With the transition from bituminous coal to lignite, flue gas waste heat recovery technology has become an effective and practical solution for circulating fluidized bed boilers facing high exhaust temperature issues. This project successfully reduces flue gas heat losses, improves boiler efficiency, and delivers strong economic and environmental benefits, offering a proven reference for similar coal-fired power plants seeking energy-efficient and low-carbon operation.
