C6组分加氢系统压降升高原因及改进措施

中国石化上海分公司苯抽提装置系由1974年投产的重整—抽提—精馏装置改造而来，因原料中含有烯烃，高温下容易在加热炉炉管及反应器上部的催化剂床层处生焦，造成C6组分加氢系统压降升高，导致装置停工。为此，采取多项改进措施：增加一台热载体换热器，以替代加热炉，避免局部高温，减缓生焦速率；对装置实施爆破吹扫，清除固体颗粒；使用活性更高、选择性饱和烯烃的能力更强的新型催化剂；改装置进料为上游连续重整装置直接进料，避免了C6组分中二烯烃长时间储存后生成低聚物并转化为高聚物生焦，导致压降升高的可能；同时，于2008年更换一台压缩机，增强装置运行的稳定性。措施实施后，加氢系统压降一直稳定在0.7MPa，实现了装置长周期运行。

Causes of Higher Pressure Drawdown in C6 Hydrogenation System and Countermeasures

SINOPEC Shanghai Company＇s benzene extraction unit was buih based on a refiwming-extraction- distillation unit that went into operation in 1974.Since the feedstock used in the unit contains olefin,the tubes of the heating furnace and the catalyst bed at the lop of the reactor are prone to coke buildup under high temperatures,which wouhl result in an increase in the pressure drawdown of the C6 hydrogenation system and thereby a shutdown of the unit.To resolve this problem,technicians at the company took measures to optimize the perfurmance of the unit.They added a heal carrier exchanger to replace the heating furnace to prevenl local high temperatures and to slow down the coke buildup;blast-blow was conducted on the unit to remove solid particles;new types of catalysts were adopted,which have higher activity and selective saturated olefin with stronger ability;changing the feeding mode of the unit to direct feeding at the upsteam continuous reforming unit （this eliminates the possibility that alkadiene in C6 becomes low polymers after long-time storage,which will convert to high polymers and further to coke,resulting in an increase in pressure drawdown）; in 2008,a compressor was replaced to enhance the operational stability of the unlt.After these measures were taken,the pressure drawdown of the hydrogenation system remained at 0.7MPa and the unit achieved long- term operation.