对二甲苯装置吸附分离系统脱除C9芳烃研究

Study on C9 Aromatic Hydrocarbon Removal Using Paraxylene Unit’s Adsorption Separation System

重质解吸剂吸附分离工艺技术是从C8A(C8混合芳烃)中分离制备高纯度PX(对二甲苯)的主要方法。该技术通常采用PDEB(对二乙基苯)作为解吸剂,C9A(C9混合芳烃)是不可忽视的杂质,若操作不当导致吸附分离装置内物料中含有较高含量的C9A,会影响吸附剂对PX的吸附容量,也会影响PX产品纯度。在常规操作条件下C9A与解吸剂沸点较为接近,难以有效分离,会随着解吸剂循环在装置内累积。结合实际案例,选取直接影响系统内C9A含量的二甲苯塔、抽余液塔、抽出液塔为对象,采用Aspen Plus模拟计算了3个塔塔底热负荷随C9A脱除率变化规律,提出了最优的C9A脱除方案,可为对二甲苯装置解吸剂被超量C9A“污染”后的净化工作提供理论和实践指导。

The primary technique used to separate and manufacture high-purity PX(p-xylene)from C8A(C8 mixed aromatics)is the heavy desorbent adsorption separation process technology.As PDEB(p-diethylbenzene)is typically used as a desorbent in this method,it is impossible to disregard C9A(C9 aromatics)as an impurity.The adsorption capacity of the adsorbent for PX and the purity of the PX product will be impacted by inappropriate operation that results in a high content of C9A in the material in the adsorption separation device.Under normal operating conditions,the boiling points of C9A and the desorbent are relatively close,making it difficult to separate them effectively.So,CA9 accumulates in the equipment as the desorbent circulates.In this study,in combination with actual cases,a xylene tower,a raffinate tower,and an extraction tower,which directly affect the C9A content in the system,were selected as targets,and the fluctuation rule of the heat load at the bottom of the three towers depending on the C9A removal rate was studied by simulation,and a proposed optimal C9A removal scheme was created.This can provide theoretical and practical guidelines for cleaning the desorbent in the p-xylene unit after being“contaminated”by excess C9A.