直吹式制粉系统与空气预热器的质量能量平衡关系分析

An Analysis of the Mass-and-Energy Balance Relationship Between a Direct-fired System and Air Preheater

针对火力发电厂燃煤锅炉变煤种后导致制粉系统冷风份额增大和锅炉排烟温度升高的问题,以华北某大型火力发电厂330MW燃煤机组正压直吹式制粉系统和三分仓回转式空气预热器为研究对象,基于制粉系统和三分仓回转式空气预热器的热力计算,得出了制粉系统和空气预热器风量-风温特性曲线;基于制粉系统和空气预热器空气质量平衡和热量平衡关系确定制粉系统和空气预热器的工作点。分析计算结果与现场运行状况相符合。根据计算结果,对降低锅炉排烟温度、减少冷风份额的措施进行了分析评价,降低空气预热器进口烟气温度可以有效地降低排烟温度,而减小空气预热器一次风冲刷转子的份额以降低排烟温度的效果不明显。

To solve the problems of an increase in cold-air share in a milling system and a rise in boiler exhaust gas temperature which are caused by a change in coal types for coal-fired boilers at a thermal power plant, the air quantity-temperature characteristic curves of the milling system and air preheater have been identified based on a thermodynamic calculation of the milling system and the three-chamber rotary air preheater. This has been realized with the positive-pressure direct-fired system and three chamber rotary air preheater of a 330 MW coal fired boiler unit at a North China large thermal power plant serving as an object of study. On the basis of the air mass balance and heat quantity balance of the milling system and air preheater, their operational points can be determined. The analysis and calculation results are in good agreement with the on-site operation conditions. Proceeding from the calculation results, an analysis and evaluation of the measures to reduce the exhaust gas temperature and cold air share has also been conducted. A reduction of flue gas temperature at the air preheater inlet can effectively lower the exhaust gas temperature but a reduction of the share of primary air sweeping across the air preheater rotor has little effect in reducing the exhaust gas temperature.