超临界直流锅炉蓄热的分析与计算

Analysis and Calculation of Heat Storage in Supercritical Once-through Boilers

根据水和水蒸气的热力性质,将超临界直流锅炉蒸发受热面分为过冷水段、过渡段和过热段,通过机理分析和模型简化,采用集总参数法建立蒸发受热面、分离器和过热器的模型,利用锅炉结构设计数据计算不同负荷下锅炉的蓄热系数,并对某1 000MW超临界机组锅炉进行实例计算.结果表明:当锅炉在亚临界状态下运行时,随着压力的变化,水冷壁内工质蓄热的变化量大于超临界状态下的变化量;金属的蓄热远大于工质的蓄热,过热器的蓄热占整个锅炉蓄热的70%左右;超临界锅炉的蓄能系数随着压力的升高而减小.

By dividing the evaporating surface of supercritical once-through boiler into cold-water, density change and overheat-steam three sections according to thermal properties of water and steam, a lumped pa rameter model was built up for the evaporating surface, separator and superheater through mechanism a nalysis and model simplification, with which the heat storage coefficient of boiler was calculated under dif ferent loading conditions based on design data of boiler structure. Application results to a 1 000 MW su percritical unit show that the heat storage of working medium in boiler water wall varies more greatly along with the pressure at subcritical pressure than at supercritical pressure; the heat storage capacity of metal material is much higher than working medium; the superheater collects about 70% heat of the whole boil er; the heat storage coefficient of supercritical boiler reduces with rising pressure.