双流法溶出新工艺高温碱液腐蚀与防止方法试验研究

本文报导了国家攻关项目———双流法溶出新工艺及设备研究专题中高温碱液预热器工业模拟腐蚀试验和工业腐蚀试验结果。通过分析工业腐蚀试验中高温碱液预热器的温度径向分布,得出在预热器内套管内壁处碱液因饱和蒸气压大于其静压力产生气泡,气泡因压力梯度和温度梯度的存在,在向径向移动的过程中冷却破裂,对其内壁产生巨大冲击力而发生腐蚀,即空泡腐蚀;提出了应用双流法改进流程、降低熔盐温度、提高碱液与矿浆流的比例和采用全逆流预热流程等防止腐蚀方法。通过调整工艺条件和设备参数,应用双流法溶出新工艺稳定运行800多小时,无腐蚀现象发生。

Experimental researches on corrosive alkali liquor at high temperature and preventive measures there of

This paper sketched out industrial simulated tests of preheaters with alkali liquor at high temperature and presented their corrosion test results as the problem of the corrosion hinders an important innovation of the Dual Flow Digestion Technology in domestic alumina industry.By the analysis on radial distribution of temperature of alkali liquor at high temperature in preheaters industrially tested,it is found that the saturated steam pressure of alkali liquor at the sleeve tube wall of preheaters is higher than its static pressure with the occurance of gas blisters which are then cooled and broken up in the course of their radial movement due to the existance of both pressurd and temperature gradients.As a result,there occur a strong impulse at inner wall with consequent blister corrosion.Thus a modified Dual Flow Digestion Technology and corrosion preventive measures are presented,such as,lowering temperature of melted salt,elevation of flow proportion of alkali liquor to digesting slurry,and adopting overall counter current preheating system.It is demonstrated that there is no corrosion phenomenon found after a test of the modified Dual Flow Digestion Technology with,adjusted technological conditions and parameters of equipment for over 800 hours of stable operation.