700℃燃煤发电机组多层结构主蒸汽管道及其壁温计算

Multilayer Structure Main Steam Pipe and Its Wall Temperature Calculation for 700 ℃ Coal-Fired Generation Unit

主/再热蒸汽管道制造技术是700℃火力发电机组的关键技术之一。为了降低蒸汽管道的制造成本,根据耐热与耐压分开的原则,提出了多层结构蒸汽管道方案,即内层管道耐热,但是不让其承受太大的压力;而外层管道承压,但是不让其温度太高。这样,内外层管道的制作材料选择上有了很大的灵活性,成本大大降低。依据具体的结构和隔热介质不同,蒸汽管道又可以分成空气隔热、蒸汽隔热和蒸汽冷却3种型式。建立了蒸汽冷却方式的传热计算模型并对冷却蒸汽温度、外管道的温度进行了计算。计算结果表明:在管内蒸汽为700℃、冷却蒸汽为400℃且管长为10 m时,外层承压管道的温度不超过415℃。

The manufacturing technology of main steam and reheat steam pipe is one of the key technologies to develop the 700℃thermal power generation units.In order to reduce the manufacturing cost of the steam pipe,the multilayer structure of steam pipe was proposed according to the principle of separating heat and pressure.It means that the inner pipe would be heated without too much high pressure,while the outer pipe undertakes pressure with lower temperature.So the materials of the inner and outer pipes could be chosen flexibly,and the cost of steam pipe would be greatly reduced.Based on the specific type of structure and insulation media,the steam pipe can be divided into three kinds,namely,the air insulation type,steam insulation type and steam cooling type.The heat transfer model of steam cooling type was established and the temperature of cooling steam and the outer pipe were calculated.The calculation results show that when the main steam in the pipe is 700℃,the cooling steam is 400℃and the pipe length is 10 m,the temperature of the outer pressure pipe does not exceed 415℃.