炼厂加工伴洗油的影响与对策

Impact and Countermeasures for Processing Wash Oil in Refineries

某炼厂租用国家管网原油罐作为进口原油的中转罐,中转罐清罐前使用原油进行冲洗,洗后原油俗称伴洗油,与其他原油混输至炼厂加工。因伴洗油中水、盐和固体杂质含量高,原油切水量大,固体杂质易在储罐中沉积,不利于储运系统切水清罐操作。加工伴洗油期间,常减压装置脱前原油水含量超出控制指标≤0.5%(质量分数)共计35次,盐含量最高1316mgNaCl/100mL,出现电脱盐电流波动,脱后盐含量多次不合格,初馏塔与常压塔顶压、液位等参数大幅波动,低温部位设备腐蚀加剧,污水处理系统污水氨氮及电导率升高等问题。针对存在的问题,采取了单炼石蜡基原油,控制伴洗油配炼比例,加强电脱盐反冲洗,污水处理系统加注硝化菌种,优化污水处理流程等措施,有效缓解了伴洗油的影响。提出优化原油库原油预处理剂,完善原油库脱水设施,优化调整原油罐功能,增加原油沉降时间等建议,以进一步缓解伴洗油对炼厂平稳运行的影响。

A refinery rents PipeChina's oil tanks as the transfer tanks for imported crude oils.Before cleaning the transfer tanks,crude oil is used to wash the tanks.The washed crude oil,commonly known as wash oil,is mixed with other crude oils and transported to the refinery for processing.Due to the high content of water,salt and solid impurities in the wash oil,a large amount of water needs to be drawn off from the crude oil and the solid impurities are easily deposited in the tanks,which is not conducive to the water draw-off and tank cleaning operation of the storage and transportation system.During the processing of wash oil,the water content of crude oil exceeded the control index of no higher than 0.5%(m/m)for a total of 35 times prior to the electric desalting in CDU/VDU,with a maximum salt content of 1316mg NaCl/100mL.Some problems occurred,such as the current fluctuations of electric desalting,the multiple failures to meet the salt content indicator after electric desalting,the significant fluctuations in overhead pressure,liquid level and other parameters of primary tower and atmospheric tower,the intensified equipment corrosion in low-temperature areas and the increased ammonia nitrogen and conductivity of wastewater in wastewater treatment system.In response to the existing problems,some measures were taken to effectively alleviate the impact of wash oil,such as processing paraffin-based crude oil alone,optimizing the mixing ratio of wash oil,strengthening the backwashing of electric desalting,adding nitrifying bacteria to the wastewater treatment system,and optimizing the wastewater treatment process.Some suggestions were proposed including optimizing the crude oil pre-treatment agent in the crude oil depot,improving the dehydration facilities in the crude oil depot,optimizing and adjusting the functions of crude oil tanks,and increasing the sedimentation time of crude oil,in order to further alleviate the impact of wash oil on the smooth operation of the refinery.