Thermodynamic Calculation And Energy Saving Analysis Of A 1069 T/h Circulating Fluidized Bed Boiler

In recent years, due to the optimization of thermal power structure, a energy structure that large-capacity, high-parameter coal-fired generating units as the main has gradually formed, the coal consumption rate of our coal-fired power generation dropped significantly, with an average annual decline 5.5 g/kWh. However, with the dividend bringed by policys like "developing large units and suppressing small ones" is nearing completion, meanwhile the requirements of controling emissions of coal-fired power plants increasingly stringent, thus the request of building new coal-fired units are increasingly faced with strict approval. In the next decade, the efficiency of coal-fired units whether it continues to rise, depend on how to improve the overall level of the operational units effectively, thereby gaining considerable economic and social benefits.In this paper, a circulating fluidized bed (CFB) boiler is took for the study. Its excessive gas temperature brings a low efficiency and a series of equipment failures. Firstly, depend on the thermodynamic parameters of several operating conditions of the boiler, we establish a precise calculation boiler thermodynamic model. The model is then used to assess the retrofitting’s effect, a comprehensive thermodynamic calculations and analysis has been conducted for three typical operating conditions before and after the retrofitting. In addition, the air pre-heater and economizer heat transfer characteristics were analyzed, and recommendations to improve the air preheater sootblower. At last, probe the program adding a Low-Temperature Economizer(LTE) in flue duct of the boiler tail, thus saving the flue gas heat and reduce flue gas temperature. This paper analyses three programs on the basis of thermodynamic、technical and economic properties by equivalent enthalpy drop method and fluid dynamics and economic analysis.The result shows, simply reduce the gas temperature beforhead economizer is difficult to reduce the final exhaust gas temperature. The main reason of flue gas exhaust is the badly ash deposition in air preheater, so the increasing efficience of soot blower is quite important. The result also shows, taking all factors considered, the LTE paralleling 6# and 7# regenerative heater is the best program. When the LTE’s outlet gas temperature is 110℃, the unit coal consumption decreased by about 2.1 g/(kWh), an annual saving of more than 3100 tons of standard coal, fuel savings over 2 million yuan (run by the unit in 5000 h per year, standard coal price 650 yuan/tons), the annual net income of 1.28 million yuan, economic benefits significant.