Design And Optimization Of The Efficient Waste Heat Recovery System In Air-cooling Unit

Compared with wet unit, the most significiant advantage of the air-cooling unit is water-saving. However taking its higher exhaust pressure and lower thermal efficiency into consideration, it is necessary to find out how to improve the efficiency of the system combined with its characteristics. In the air-cooling unit, the amount of either boiler flue gas heat loss or turbine exhaust heat loss is huge. It is significiant to make good use of these two kinds of waste heat, especially for improving efficiency and reducing coal consumption of the unit.To realize the utilization of the boiler flue gas waste heat, the most common method is setting low-temperature economizer behind the air preheater. In this paper, energy conservation principles and constraints are discussed in detail. It shows that the system of the low-temperature economizer is not only the simpliest and most effective method of flue gas waste heat recovery but also the foundation to achieve the utilization of the turbine exhaust heat. With the data of a typical600MW air-cooling unit, a waste heat utilization system for air-cooling unit based on the low-temperature economizer system is proposed. Method of how to recycle hot air heat from air-cooling condenser is initially introduced and related thermodynamic and economic analysis are also expanded. Binding energy cascade utilization theory, efficient waste heat recovery system for air-cooling unit is proposed. Further optimization about the system is developed as well. Study results of this paper have some reference value for design and optimization of the waste heat recovery system in air-cooling system.