Research On Numerical Simulation Of Heat Transfer And Low Temperature Economizer Of Low Temperature Corrosion Of Utility Boiler

At present, the waste heat loss takes more than half of the whole thermal loss in the boiler, due to the high flue gas temperature of large coal-fired boiler ranging from 120 to 140℃. Making good use of waste heat from flue gas in-depth can reduce power consumption and improve the utilization ratio of energy. It has important significance to achieve the goal of energy conservation and emission reduction in our country. At present, there are a lot of waste heat recovery devices. However, the low temperature economizer is one of the safest and most efficient equipment for the recovery of the waste heat of power station. The application of low temperature economizer can further reduce the heat loss of boiler flue gas and improve the economic benefit of thermal power industry.Low-temperature corrosion can seriously affect the security of the waste heat utilization system. The flue gas acid dew point is one of the important parameters to assess low temperature corrosion. In this paper, the domestic and foreign acid dew point calculation formula and the field measurement of acid dew point meter were analyzed. Different acid dew point empirical formulas were calculated. The results showed that the acid dew points differed quite a bit in different formulas. Compared with the measurement parameters, the theoretical parameters were more conservative with 30℃ higher. Based on the mechanism of low temperature corrosion and the model of the temperature, the concentration of the gas condensate was predicted and analyzed. The results showed that the corrosion of the concentration of sulfuric acid ranging from 60% to 90% was not serious. When the wall temperature was higher than 82℃, it had a little influence on the metal wall corrosion.The structure of the heating surface of the low temperature heat exchanger has an important influence on the heat transfer. The numerical simulation method was used to study the heat transfer and flow characteristics of spiral finned tube, including different fin height, fin spacing, transverse pitch and longitudinal pitch. The results showed that the optimal heat transfer performance of the spiral finned tube was optimal under the condition:h/d=0.289, P=8mm, S1/d=2.37, and S2/d=2.63.In this paper, the optimization model and the acid dew point of the spiral fin tube were analyzed. We designed the structure of the new type of low temperature economizer for boiler unit of 1000MW ultra supercritical coal fired boiler unit. The length of the new type of low temperature economizer was 10.29m, the width was 11.62m, the height was 3.352m, the heat exchange area was 34136m2 (single), and the total resistance of the flue gas was 790.37 31743kW. Under the condition of low temperature corrosion having no influence on the low temperature module, increasing the heat transfer temperature difference as far as possible will improve the heat transfer efficiency of the low temperature economizer.