高酸原油脱钙实践与探讨

Practices and Discussions on Decalcification of High-Acidity Crude Oil

高酸原油通常指酸值高于1mgKOH/g的原油,由于酸值高,在炼制过程中容易导致设备在高温部位发生腐蚀,给炼油装置长周期运行带来不利影响。惠州炼油设计加工渤海蓬莱19-3原油,该原油属于典型的高酸值原油,具有低硫、高氮、高酸、高金属含量的特点,按原油类型分类属于环烷中间基原油。随着蓬莱原油开采深度的增加,原油中的钙、镁离子含量明显增加,金属含量中钙、镁总含量上升明显,由60mg/kg上升至220mg/kg,为初期的3～4倍。当蓬莱原油的加工比例在60%以上时,会导致石油焦灰分含量超过0.5%,最高值达到1.0%。通过原油深度电脱盐及控制高钙镁含量的蓬莱原油掺炼比例,可生产1B级石油焦。当蓬莱原油掺炼比例较大时,可考虑加注脱钙剂。进行了蓬莱原油脱钙试验,根据试验结果,选用一、二、三级罐均参与反应的流程时,当混合阀压降为50～60kPa,注剂量为400μg/g时,总钙镁脱除率可达83.55%,但对含盐污水COD及常顶污水pH值影响较大。

High-acidity crude oil usually refers to a crude oil with an acid value higher than 1mgKOH/g.Due to its high acid value,highly sour crude oil can easily cause corrosion at high-temperature spots of equipment during the refining process,impairing the long-term stable operation of the refining units.CNOOC Huizhou Refinery was designed to process crude oil from the Penglai 19-3 in the Bohai Sea,which is a typical high-acidity crude,characterized by low sulfur,high nitrogen,high acid value and high metal contents.By crude type,it is a naphthene-intermediate base crude oil.As the depth of crude deposits developed in the Penglai field,the contents of calcium and magnesium ions in the crude have increased considerably and the total content of calcium and magnesium among all metals has risen sharply,from 60mg/kg to 220mg/kg,about 3-4 times the original content when the field started production.When the share of Penglai crude used exceeds 60%,the ash content of petroleum coke produced will exceed 0.5% and can even top 1.0%.The crude can be used to produce 1B-grade petroleum coke by means of deep electro-desalting and by controlling the share of Penglai crude with high contents of calcium and magnesium in the feed.When the share of Penglai crude blended is high,a decalcifying agent can be used.According to the results of an decalcification experiment on Penglai crude,if a process where all the three stages of tanks are involved in reaction is used,when the mixing valve pressure drop is 50-60kPa and 400μg/g of decalcifying agent is injected,up to 83.55% of the calcium and magnesium in the crude can be removed,but this method will have a relatively large effect on the COD of salt-containing sewage and the pH of atmospheric overhead sewage.