Such problems as serious salgging,frequent tube burst,superheater and reheater overtemperature and insufficient pulverizing system capacity occurred in the 600 MW unit once-through tower boiler in Yuanbaoshan Power Plant.Thus,the water wall of this boiler was optimized.According to the structural characteristics of the water wall and the heat load distribution features in the furnace after the transforma-tion,the water wall was divided into the flow circuit,pressure point and flow network system comprised of connected tubes.On the basis of the mass conservation equation,momentum balance equation and energy conservation equation,the mathematic models for pressure drop and outlet steam temperature of water wall tube in subcritical boiler were established.Moreover,the total pressure drop in rising system and the outlet steam temperature of the upper and lower water wall were calculated,under conditions with different unit loads.The results show that,the temperature of the inner pipes,outer pipes,middle points and the rear fin are all reliable,which can ensure the boiler work safely.%针对元宝山电厂亚临界600 MW机组塔式直流锅炉炉内结焦严重、“四管”泄漏频繁、过热器再热器超温、制粉系统出力不足等问题，对该机组锅炉水冷壁进行了优化改造。根据改造后的锅炉水冷壁结构特点及炉内热负荷分布特点，将水冷壁划分为由流量回路、压力节点和连接管组成的流动网络系统，根据质量守恒、动量守恒和能量守恒方程，建立了亚临界锅炉流量分配及出口汽温的计算模型。在此基础上对锅炉在不同工况时各回路流量分配及壁温分布进行了计算。结果表明，在TRL、75％TRL及30％TRL工况下，管内、外壁温度、壁厚中间点温度和鳍端温度均处于管子的允许温度范围之内，可以保证锅炉的安全运行。
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