加氢裂化空冷器管束失效的多相流数值分析

Numerical Analysis of Multiphase-flowing for Failure of High Pressure Air Cooler Bundle in Hydrogenated Cracking Unit

对加氢裂化空冷器换热管内流体进行了多相流数值计算。分析了衬管尾部结构对管束失效的影响,结果表明,衬管尾部直角结构在流体下游诱发涡流,产生高剪应力区,易发生冲刷腐蚀,而45°倒角结构和1:10锥角结构较为合理;同时对管内垢物的分布对流动状态的影响进行了分析,发现垢物沿轴向分布的不均匀改变了管内流体的流速,在垢物层最厚位置之后形成高剪应力区,产生冲刷腐蚀。计算结果与在役空冷器更换下来的换热管束腐蚀泄露位置吻合。

The numerical calculation of multiphase-flowing was carried out for the fluid in the air cooler bundle in hydrogenated cracking unit and the results were detailedly analyzed. The influence of the end structure of lining pipe of the bundle on the failure was analyzed. The 90-degree end would cause vortex in fluid at backward position where the high shearing force came into being and erosion-corrosion was easily to occur. But the structures of 45-degree chamfer end and 1：10 taper could largely improve this situation. The influence of distribution of corrosion products on flowing situation of fluid was also analyzed. The velocity of flow in pipes was largely changed by non-uniform distribution of corrosion products. The high shearing force zone appeared in backward position where the products was thickest and erosion-corrosion occured. Caculation results are accordant with the failure position of the air cooler bundle.