加氢原料煤焦油脱水除盐预处理工艺优化限值

Study on optimization limits of dehydration and desalination pretreatment of hydrogenated coal tar

原料煤焦油的脱水除盐预处理是保障后续加氢反应持久运行及装置安全的关键,而煤焦油的特殊物性及复杂组成导致当前预处理系统普遍存在效果差、调控困难的问题。以某大型煤焦油加氢装置预处理流程为基础,本文研究了预处理装置的脱水效果、除盐效果两个关键因素,首先分析了非热物理分离的脱水和除盐限值,进一步通过纤维聚结器与强化沉降器组合的中试测试,获得了聚结沉降分离限值、洗盐器级数和注水量的影响规律,在注水量6%、洗盐器三级串联、纤维聚结表观流速0.003m/s、沉降停留时间60min以上的最优条件下,煤焦油含水量降为3.1%、含盐量降为2.81mg/kg,均接近理论分离极限,为预处理装置的工艺设计及操作优化提供了新思路。

Pretreatment of coal tar by dehydration and desalination is the key to ensure the lasting operation of the subsequent hydrogenation reaction and the safety of the equipment.However,the special properties and the complex composition of coal tar lead to the bad performance and the difficulty of regulation in the current pretreatment system.Based on the pretreatment process of a large coal tar hydrogenation unit,the two key factors of the dehydration effect and the desalination effect were studied.Firstly,the dehydration and desalination limits of non-thermophysical separation were analyzed.Moreover,the pilot test of the combination of a fiber coalescence separator and an enhanced sedimentation device was conducted to obtain the separation limit of coalescence and sedimentation and evaluate the influence of salt washer series and water injection rate.Under the optimal conditions of 6%water injection rate,three-stage salt washers in series,0.003m/s superficial velocity of the fiber coalescence and the settling residence time of more than 60min,the water content of coal tar was reduced to 3.1%and the salt content was reduced to 2.81mg/kg,both of which were close to the theoretical separation limit.The results would provide a new idea for the process design and operational optimization of the pretreatment unit.