提高延迟焦化装置原料适应性及轻质油收率的措施

Measures to Enhance the Feedstock Adaptability and Light Oil Yields of Delayed Coking Units

中小型炼油厂常减压蒸馏装置能力不足,原料油不稳定,品种既多且杂,加之下游缺乏焦化蜡油加工手段,如何提高延迟焦化装置原料适应性以及轻质油收率,是面临的问题之一。工艺流程选择上,采取原料油进换热器换热→原料缓冲罐→两级电脱盐→换热器换热→再换热→分馏塔分馏的方案,采用三级电脱盐工艺;焦化分馏塔兼作常压蒸馏塔,原油在焦化分馏塔内进行闪蒸,以拔出其中的直馏轻组分,同时与焦化反应产物一并分离,使装置具有常压蒸馏装置和焦化装置的双重功能。提出了原料油经换热、脱盐再换热后进焦化分馏塔分馏,采用大循环比操作,以及相应的防结盐、防结焦和提高轻质油收率的措施。运行经验表明,优化原料油换热流程,增加电脱盐部分及循环比的调节,可以使延迟焦化装置对重质原料油、常渣、减渣进料都有很好的适应性;完善分馏系统、吸收稳定系统及大循环比操作,可以提高轻质油收率;相应采用有效的防结盐、结焦措施,可以提高装置的运行稳定性。

The atmospheric and vacuum distillation units in small and medium-sized refineries usually have a small processing capacity and an unstable source of feed oil characterized by multiple types and grades of crude oil processed.In addition,these refineries usually do not have CGO processing means downstream atmospheric and vacuum distillation units.Raising the feedstock adaptability and light oil yields for delayed coking units is one of the main challenges faced by these refineries.This article proposes several measures.On technical process,it recommends the following scheme： feed oil enters the heat exchanger for exchanging heat → feedstock buffer tank → two-stage electric desalting → heat exchange in heat exchanger → heat exchange again → fractionation in the fractionator.A three-stage electric desalting process is adopted.The coking fractionator will also be used as the atmospheric distillation tower.Crude oil is flash distilled in the coking fractionator to extract the straight-run light components and meanwhile separate the products from the coking reaction process,enabling the unit to perform both atmospheric distillation and coking functions.Other measures recommended include fractionating the feed oil in the coking fractionator after heat exchange,desalting and secondary heat exchange processes,adopting large recycle ratio operation,preventing salt depositing and coking and raising the yields of light oils.Operational results show that optimizing the feed oil heat exchange process,adding the electric desalting process and adjusting recycle ratio can raise the adaptability of delayed coking units to heavy feed oil,atmospheric residuum and vacuum residuum.Improving the fractionating system,the absorption stabilizing system and large recycle ratio operation can raise the yields of light oils.Taking measures to prevent salt depositing and coking can enhance the stability of operation of units.