加氢裂化装置新氢中断处理方法的探讨

加氢裂化装置新氢中断会造成反应压力迅速下降,循环氢流量大幅度下降,而处理难点是避免反应器飞温和裂化剂中毒。通过对加氢裂化装置新氢中断不同处理方法分析可知,在高负荷高转化率工况下,新氢中断后,应第一时间启动0.7 MPa/min低速泄压,泄压时间超过5 min,且在5 min内精制平均反应温度降低3～5℃,裂化平均反应温度降低5～10℃,反应器各床层出口温度呈下降趋势,就可以关闭紧急泄压阀,该方法优点是操作简单,风险低。在低负荷低转化率工况下,新氢中断按原料中断处理,在5 min内精制平均反应温度降低3～5℃,裂化平均反应温度降低5～10℃,如果裂化反应器催化剂采用分级装填,应该首先大幅度降低裂化活性较高的催化剂床层与装填量最多的催化剂床层温度,且确保催化剂各床层出口温度呈下降趋势,该方法反应开工恢复时间短,但是操作难度较大,在切断原料后,反应温度在短时间内无法降低,就可能发生飞温风险。

Discussion on treatment for turning off the new hydrogen in hydrocracking unit

The loss of make-up hydrogen in the hydrocracking unit will cause quick reactor pressure drop and the flowrate of recycle gas will be greatly lowered.The difficulty in treatment is to control the temperature run-away of reactor and poisoning of cracking catalysts.It is known from the analysis of loss of make-up gas in hydrocracking unit that,after the loss of make-up gas at high load and high conversion rate,the 0.7 MPa/min emergency de-pressuring should be started at first time,and the pressure relief time shall exceed 5 minutes.Within 5 minutes,the average reaction temperature of hydrotreating is lowered by 3~5℃,the average cracking reaction temperature is reduced by 5~10℃.The temperature of the outlet of each bed of the reactor is declining,and the emergency safety relief valve can be closed.The advantages of this method are that the operation is simple and the risk is low.Under the conditions of low load and low conversion rate,the loss of make-up gas will be regarded as the loss of feedstrock.The average hydrotreating reaction temperature is lowered by 3-5℃and the average cracking reaction temperature is lowered by 5-10℃within 5 minutes.If the cracking reactor catalysts are hierarchically loaded,priority should be given to greatly reducing the high-activity catalyst bed layer and catalyst bed layer with most catalysts to ensure that the temperature of the catalyst bed outlet is going down.With this treatment,the recovery time for start-up is shortened,but the operation is more difficult.After the cut-off of feed,the reaction temperature can not be lowered in a short time,and the risk of temperature run-away may occur.