1.2Mt/a延迟焦化装置低循环比运行可行性分析

Feasibility Analysis of Low Recycle Ratio Operation of 1.2Mt/a Delayed Coking Unit

独山子石化1.2Mt/a延迟焦化装置采用循环比在0.2~0.6范围内、可调的循环油脱过热工艺,无法实现装置长周期低循环比运行,生焦率≥1.65,开展93.33%负荷(140t/h)时循环油外甩,低循环比运行标定,验证其经济效益。针对目前流程无法实现低循环比运行现状,提出"现有的重污油流程外甩循环油"、"现有的重蜡油流程外甩循环油"、"改造分馏塔底人字挡板,降低循环油上下回流量"、"循环油脱过热的可调循环比工艺改为蜡油脱过热的可调循环比工艺"等4种改造方法;对于下游二次加工装置原料劣质化问题,可根据下游日常监测分析,控制好重蜡油(循环油)掺炼比例;对于加热炉结焦倾向增大问题,可依据不同循环比油样相对结焦因子分析评价,选择循环比≥0.15,并辅以工艺操作控制;对于低负荷时加热炉分支进料流量低、系统物料少、操作波动大等问题,可在焦炭塔不同生产阶段,提前对分馏塔进行调整,防止大幅波动,必要时改加热炉单炉膛生产。改造后装置可实现低循环比运行。

The 1.2Mt/a delayed coking unit at PetroChina Dushanzi Petrochemical Company adopted circulat- ing oil desuperh operation of the eating process with an adjustable recycle ratio of 0.2 to 0.6,the long-term low recycle ratio unit could not be achieved and the coking rate was 1.65 or higher.Low recycle ratio test run,with the circulating oil sent out of the unit,was carried out at 93.33% load （140t/h） to verify its eco- nomic benefit.Since low recycle ratio operation could not be achieved with the existing process flow,four modification measures were put forward including sending the circulating oil out of the unit in the existing heavy slop oil process,sending the circulating oil out of the unit in the existing HVGO process,revamping the chevron baffle at the bottom of fractionator to reduce the reflux of circulating oil and using HVGO desuperheating process with adjustable recycle ratio instead of circulating justable recycle ratio.To solve the poor quality problem of the feedstock oil desuperheating process with ad- to downstream secondary processing units,the blending ratio of HVGO may be controlled based on daily monitoring analysis.To solve the in- creased coking tendency problem of furnace,a recycle ratio no less than 0.15 may be selected based on the relative coking factor analysis of oil samples with different recycle ratios ,and supplemented with process oper- ation control.To solve the problems of low flow rate of branch feed to furnace ,less material in system and large operation fluctuations during low load operation,the fractionator may be adjusted in advance at different production stages of the coke drum to avoid large fluctuations, and if necessary ,single-furnace production may be used.After the modification,the low recycle ratio operation of delayed coking unit can be achieved.