原料性能对加氢裂化装置长周期运行的影响

结合长庆石化120×104t/a加氢裂化装置运行数据,从原料油预处理过程,原料油的硫、氮含量、重杂质含量、金属含量及原料油干点几方面进行分析,总结出维持加氢裂化装置长周期运行的改进措施:鉴于原料油罐倒罐频繁,建议增加一具原料油罐,以保证进料前的充分沉降,除去原料油中的固体颗粒和水,减少原料油过滤器反冲洗频次;加强与上游装置的联系,严格常减压装置减压塔切割效率,密切监控原料油性质变化,增加色度分析法,监控VGO中重杂质含量,以指导加氢裂化生产,改善装置操作;由于减压蜡油硫低氮高,需要向系统补充一定量的硫,同时保持注水,减少循环氢中的氨浓度,但注水增加后,又伴随着循环氢中硫化氢的损失,因此从经济上考虑,需要保持三者的平衡,才能保证催化剂活性,维持装置的长周期运行;如果改善原料性质,维持循环氢中的硫化氢含量,降低氨含量,或者选用适合低硫原料油的催化剂,可提高装置运行周期。

Impact of Feedstock Properties on Running of Hydrocracking Units

This article discusses the optimized measures of maintaining the long-term operation of hydrocracking units by analyzing the feed oil pretreatment process,the contents of sulfur,nitrogen,heavy impurities and metals in feed oil and the dry point of feed oil using data from the 120×104t/a hydrocracking unit in PetroChina Changqing Petrochemical Company.Given the high frequency of overturning the feed oil tank,the article suggests adding a feed oil tank to ensure the full sedimentation prior to oil feeding.This can also help remove the solid particles and water in the feed oil,reducing the frequency of back flush for the feed oil filter.Other optimization measures recommended by this article include： strengthening the interaction with the upstream units;raising the cutting efficiency of the vacuum distillation tower of the atmospheric and vacuum distillation unit;closely monitoring the changes in the properties of the feed oil;adding a colorimetric analysis process;and monitoring the contents of heavy impurities in VGO to guide the hydrocracking operation and to improve the unit′s operation.As the content of sulfur is high and that of nitrogen is low in VGO,an additional amount of sulfur is needed in the system and at the same time water injection should be maintained and the concentration of ammonia in the circulating hydrogen should be reduced.However,with the increase of the amount of water injected,some hydrogen sulfide in the circulating hydrogen will be lost.Therefore,economically,a balance between the above three factors is necessary to ensure the activity of catalysts and to sustain the long-term operation of the unit.If the properties of the feedstock are changed to maintain the content of hydrogen sulfide in the circulating hydrogen and reduce the content of ammonia,or a catalyst suited to low-sulfur feed oil is used,the cycle of operation of the unit can be extended.