| Due to lack of energy resource, flue gas heat recovery of thermal power plant plays an important role in the national energy saving and emissions reducing work today. Air preheater is one of the essential heat-exchange equipment to recycle the exhaust fume heat in power plant boiler. During the operation of power plant boiler, the metal heating surface of air preheater exists ash deposition and corrosion commonly.It raises boiler’s exhaust temperature, lowers boiler’s thermal efficiency, and it also effects the safe operation of boiler when the situation becomes worse. Three-dimensional finned tube(3-D FT) is a new kind of heat exchange tube, it’s special heat transfer mechanism and processing equipment make it have the characteristics of unlimited processing materials, adjustable arrangement and structure parameters of fins, better heat transfer performance, self-cleaning, anti-fouling, small volume etc. 3-D FT used in air preheater of power plant boiler can reduce the likelihood of ash deposition and corrosion occurrence, it has been applied in some domestic power plants. In order to promote the application of 3-D FT in air preheater of power plant, this paper conducts a field test in a power plant for study the ash deposition and corrosion performance of internal and external 3-D fined tube air preheater. And then using internal and external 3-D fined tube to design a new air preheater for a power plant to replace its smooth-tube one before.This paper designs the test scheme and experimental devices for the ash deposition and corrosion performance experiment of the internal and external 3-D fined tube air preheater.This paper takes internal and external 3-D fined tube and smooth-tube as the objects of the research and conducts a field test in the bypass of a power plant, then comparing the ash deposition and corrosion performance of them.At the same time, this paper also conducts SO3 content test, and chooses the SO3 content has been known formula as the calculation formula of acid dew point. The experiment found that under the experiment condition, smooth-tube’s engineering acid dew point is over 60℃, 3-D FT’s engineering acid dew point is about 40-50℃,and the acid dew point of the flue gas in power plant 1 is about 133℃.The engineering acid dew point of the 3-D FT is lower than the actual acid dew point of flue gas at least 80 ℃.Therefore, the 3-D FT air preheater operates under less than 80℃ below the design exhaust temperature, it doesn’t occur ash deposition and corrosion. Therefore, using 3-D FT as the heat exchange tube of air preheater, it can reduce the exhaust temperature of the boiler tail to 90-100℃, realizes the deep utilization of flue gas waste heat, enhances the economy of air preheater and makes no ash deposition or corrosion.Based on good application of 3-D FT in air preheater of power plant and the results of the ash deposition and corrosion performance field experiment, this paper uses internal and external 3-D FT to design the air preheaters of #1 and #2 units of a power plant.It is in order to solve the serious problems of corrosion and leakage of the original smooth-tube heat exchanger. According to the practical operating parameters of the power plant, this paper does thermodynamic calculation and drag calculation of the air preheater, ensures the arrangement and structure parameters of fins, analyzes the feasibility, economic benefits, environmental benefits and risks of the renovation project. The implementation of the renovation project solves the problems of corrosion and leakage of the original smooth-tube heat exchanger, improves the efficiency of the boiler, reduces the emissions of greenhouse gases and air pollutants greatly, lowers the consumption of the coal and water resources and it doesn’t produce other pollutants. This plays an important role to improve the environmental problems of acid rain and greenhouse effect. The investment recovery period of the project is less than two years, it has remarkable economic and environmental benefits. |
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