延迟焦化分馏塔塔盘腐蚀原因分析及防护措施

Analysis of Corrosion Causes of Overhead Tray of Delayed Coker Fractionator and Improvement Measures

2011年装置大检修期间,对某石化分公司延迟焦化装置分馏塔顶部3至7层塔盘存在较严重程度的腐蚀现象进行了分析。采用电子能谱分析法(EDX)和X射线衍射法(XRD)等方法进行腐蚀产物分析,发现腐蚀垢样主要成份是铁的硫化物。认为造成腐蚀的主要原因是:减压渣油性质劣化,回炼重污油盐含量高,电脱盐效果不佳,回炼废环丁砜二氧化硫含量高,分馏系统水洗流程不完善及结盐冲蚀等。提出采取微萃取技术,将水均匀分散到循环油中,经深度捕获盐类离子并将油水进行预分离,利用粗粒化及波纹强化沉降,实现油水分离等措施,达到顶循油在线脱盐目的。改进措施实施后,油中Cl质量分数降低了27.59%,含盐水中Cl-质量浓度降低了34.27%,避免了分馏再次结盐的情况,保证了装置的长周期安稳运行。同时为其它装置解决类似问题提供了借鉴。

In the overhaul of delayed coking unit of a petrochemical company in 2011, the corrosion products of the overhead 3 -7 trays of fractionatian tower were analyzed by energy dispersive X- ray （EDX） and X- ray diffraction （XRD） methods. It is found that the main component of corrosion scale is iron sulfides. It is concluded that the main causes of corrosions are ： degradation of vacuum residue properties, high salt content in recycled heavy residue oil, poor electro desalting efficiency, high sulfur dioxide content in recycled sulfolane and lower efficiency of water washing process and impingement erosion of salt in fractionation system. It is suggested to adopt the micro extraction process to disperse water into the recycle oil, separate water from oil by capture of salt ions and strengthen the settlement by coarse graining and corrugating to realize oil - water separation in on - line desahing of the overhead recycle oil. After implementation of these measures, the chlorine in oil is reduced by 27.59% , chloride ion in brine is lowered by 34.27%, which eliminates the salt deposition in the fractionation system and ensures the long - term stable operation of the unit. At the same time, a good reference is provided for other units to solve the similar problems.