煤焦油馏分塔的腐蚀原因分析及评价

Analysis and Evaluation of Causes Leading to Corrosion of Coal Tar Rectification Tower

对煤焦油馏分塔的使用现状进行了调查,并借助金相显微镜、能谱仪、耦合等离子发射光谱仪、X射线衍射仪等手段从煤焦油馏分塔的材质、腐蚀介质、腐蚀产物等角度讨论了其腐蚀的原因;利用塔板在一定时间内的尺寸变化测定了其均匀腐蚀速度。结果表明,该塔的内件材质是奥氏体型不锈钢316L,基体分布着少量铁素体,介质中存在着大量的硫离子及氯离子,使316L具有很大的孔蚀倾向;腐蚀产物中存在着大量的硫元素,并以Fe7S8形式存在;4mm的塔板约2a可被均匀腐蚀掉,但孔蚀的发生将使塔板的腐蚀破坏时间远低于2a;316L不宜作为煤焦油馏分塔的材料使用。

A survey was made about the use and corrosion of coal tar rectification tower in engineering.Thus the causes leading to corrosion of the rectification tower were analyzed,based on investigation of the microstructures of the materials for construction of the tower,the corrosive medium,and the corrosion products by means of metallographic microscopy,energy dispersion spectroscopy,inductively coupled plasma spectrophotometry,and X-ray diffraction.The uniform corrosion rate was measured by measuring the thickness change of the tower board in a certain period.Results indicated that the inner wall of the tower was made of 316L austenitic stainless steel containing a small amount of ferrite.Because a lot of sulfur ions and chlorine ions existed in the corrosive medium,the stainless steel was liable to pitting corrosion.At the same time,there was a large amount of S in the corrosion products,appearing as Fe7S8.The tower board with a thickness of 4 mm experienced overall corrosion in 2 years,but its corrosion destruction duration was much less than 2 years,owing to the pitting corrosion.Therefore,the 316L stainless steel was not suitable to be used as the structural material of the coal tar rectification material.