重整预加氢氧汽提系统堵塞原因分析与对策

某连续重整装置预加氢单元氧汽提系统塔顶空冷器压力降上升快、腐蚀堵塞严重。从氧汽提系统各部位的堵塞和腐蚀情况,原料油来源、存储以及原料油的氧、H2S、氯、烯烃等杂质含量和氧汽提工艺流程等方面,对氧汽提系统腐蚀堵塞的原因进行分析,认为外购石脑油中的氧含量高(质量分数达10μg/g以上)和加氢焦化石脑油进入氧汽提系统是造成系统腐蚀堵塞的主要原因。提出了氧汽提塔顶增设注缓蚀剂、回流罐顶吹惰性气体改至空冷器前或氧汽提塔底兼作汽提气、控制原料油进氧汽提塔温度、适当提升空冷器设备材料等措施,以解决和改善预加氢单元氧汽提系统腐蚀堵塞问题,改造后回流罐分水包中酸性水的铁离子的质量浓度降至200 mg/L以下,汽提塔顶空冷器进出口压力降维持在50kPa左右。

Causes and countermeasures of blockage in oxygen stripping system of reforming pre-hydrogenation unit

The pressure drop of top air cooler in oxygen stripping system of pre-hydrogenation unit of a continuous reforming unit rises rapidly and the corrosion blockage is serious. The causes of corrosion blockage in oxygen stripping system are analyzed from the aspects of blockage and corrosion situation and process flow, source and storage of feedstock oil, and impurity content of oxygen, H2S, chlorine and olefin in feedstock oil. It is considered that the main reason is that the oxygen content in purchased naphtha is over 10 μg/g, and the hydro-coking naphtha enter the oxygen stripping system. The measures of adding corrosion inhibitor to the top of oxygen stripping tower, changing the top of reflux tank to blow inert gas before air cooler or at the bottom of oxygen stripper as stripping gas, controlling the temperature of feedstock oil inlet oxygen stripper and properly raising the material quality of air cooler equipment can solve and improve the corrosion blockage of oxygen stripping system in pre-hydrogenation unit. After that, the iron ion content of sour water in the water separator of the reflux tank is reduced to less than 200 mg/L, and the pressure difference between the inlet and outlet of the headspace cooler of the stripper is maintained at about 50 kPa.