糠醛精制装置抽出液加热炉炉管腐蚀分析及对策

Corrosion Analysis of Extract Furnace Tubes for Furfural Refining Plant and Countermeasures

介绍了糠醛精制装置抽出液加热炉的工艺特点、炉管结构和腐蚀状况。抽出液加热炉炉管急弯弯头内表面蜂窝状坑蚀及冲刷腐蚀严重,靠近外径处已形成深度约1.5 mm的沟槽,最严重处壁厚仅为5.0 mm。分析炉管产生腐蚀原因为:装置脱气塔停用造成系统中糠醛氧化,产生大量糠酸及焦粉;减四线原料油的酸值相对较高(0.47 mgKOH/g)是炉管产生腐蚀的原因和糠醛生成糠酸的诱因;抽出液加热炉辐射室炉管弯头因材质偏低,受到糠酸和环烷酸腐蚀、焦垢下缝隙腐蚀、焦粉的冲刷腐蚀等共同作用,使炉管弯头迅速减薄。针对以上腐蚀情况,采取了对装置脱气塔进行改造、系统中加注脱酸剂、炉管材质进行升级等防腐措施。

The process features and the structure of extract furnace tubes for furfural refining plant are introduced. The internal surface of elbow of extract furnace tubes suffered from serious honeycomb corrosion and erosion corrosion. Corrosion pit of 1.5 mm in depth was formed close to the outside diameter. The thickness of walls of serious corrosion was only 5.0 mm. The causes of corrosion are ： production of large amount of furoic acid and coke powder because of oxidation of furfural during the shutdown of the degassing tower, higher total acid number （TAN） of crude oil （0.47 mgKOH/g） which provides conditions for the formation of furoic acid from furfural, selection of lower grade materials for elbow of radiant tube elbows which are subject to furfural corrosion, naphthenic acid corrosion and erosion corrosion. The combination effects of these resulted in the rapid thinning of elbows of furnace tubes. To solve these problems, the following measures have been taken, such as revamping of degassing tower, addition of acid removal agent into the system and upgrading of materials of furnace tubes.