延迟焦化装置大油气线结焦因素及预防措施

Causes of Coke Depositing in Overhead Vapor Line of Delayed Coking Units and Countermeasures

辽河石化公司针对延迟焦化装置大油气管线与焦炭塔出口接口处结焦的影响因素进行了分析,提出预防措施:控制好加热炉出口温度;焦炭塔顶温度采用注入急冷油使塔出口温度保持在(420±5)℃;焦炭塔在切换新塔2h前,将加热炉出口温度提高2～3℃,将干气脱硫塔顶出口处压力由0.90MPa憋压到0.94MPa,减少大油气管线结焦几率;采用12点分4路向管网注3.5MPa中压蒸汽,来提高管内介质流速以缩短缩和反应时间,减少因缩和反应生成的中间相吸附在炉内管壁引起的结焦;老塔切换新塔后,将小吹汽1.0MPa低压蒸汽由设计值6～8t/h调整为4～6t/h,时间由1.5h调整为2.0h,减少在小吹汽过程中因部分泡沫层和焦粉带入大油气管线引起结焦;控制焦炭塔顶压力在0.15～0.18MPa,避免因压力过高发生泡沫夹带和压力过低增加操作成本;在焦炭塔18m、23m、27m处分别安装137Cs作为γ射线料位计放射源,随时监测料位高度,防止因生焦高度过高引起焦粉携带和溢塔事故。

Technicians at Liaohe Petrochemical Company analyzed the factors affecting the coke depositing at the joint of the overhead vapor line and the coking tower of its delayed coking units and proposed countermeasures which are outlined as follows ：controlling the temperature at the outlet of the heating furnace ;maintaining the temperature at the outlet of the coking tower at （420±5）℃ by injecting in quenching oil;raising the temperature at the outlet of the heating furnace by 2-3℃ two hours before switching to new coking tower and increasing the pressure at the outlet of the top of the dry gas desulfurization tower to 0.94MPa from 0.90MPa to reduce the possibility of coke depositing in the overhead vapor line;injecting 3.5MPa mediumpressure steam in the pipeline network through four routes at 12 points to increase the flow rate of the medium in the pipelines to reduce the contraction reaction time and reduce the coke depositing caused by the adsorption of intermediate phase generated from contraction reaction on the inner wall of the furnace ;after switching to the new tower,reducing the flow rate of 1.0MPa steam injected to 4-6t/h from the designed value of 6-8t/h and increasing the duration to 2h from 1.5h to reduce the coke depositing caused by the entry of some foaming and powdered coke in the overhead vapor line during steam blowing;maintaining the pressure at the top of the coking tower between 0.15-0.18MPa to prevent foam entrainment caused by excessively high pressure or higher operational cost due to excessively low pressure;installing 137Cs at locations 18m,23m and 27m of the coking tower as the radioactive source of γ-ray charge level indicators to monitor the level of charges in real time to prevent powdered coke entrainment and tower overflow due to excessively high coke column deposited.