吸收稳定系统的模拟与分析

PROCESS SIMULATION AND ANALYSIS OF ABSORPTION-STABILIZATION SYSTEM

针对国内吸收稳定系统普遍存在的干气中C3、C4含量较高、液化气产率低等问题,以国内某石化企业延迟焦化装置为例,在计算机模拟与分析的基础上,探讨吸收稳定系统的模拟策略,如单元模型、热力学方法的选取等,并对影响系统分离效果的主要因素进行分析,提出改善吸收稳定过程分离效果的操作方案。结果表明:RKS方程是较适宜应用于吸收稳定系统的热力学模型,其模拟计算结果与工业标定数据吻合较好;从全流程角度出发,解吸塔进料温度升高、稳定汽油吸收剂流量降低都有利于系统节能,但系统吸收效果出现下降;解吸塔塔釜温度对液化气组成与流量、干气中C3和C4含量都有一定的影响,在生产中应充分重视解吸塔塔釜温度的波动;稳定塔的回流比存在一个"理想值",小于该值时随回流比增加系统吸收效果改善明显,实际操作回流比应小于该"理想值"。

Simulations of absorption stabilization systems were conducted to study the methods for decreasing the content of C3 and C4 in dry gas. Taking a typical absorption-stabilization system of a domestic delayed coking unit as case study,the simulation strategies including the selection of unit model, the determination of thermodynamic methods and etc. were discussed. The main factors affecting the separation effect were analyzed and finally,an operation scheme to improve the separation efficiency of absorption-stabilization process was proposed. Results showed that RKS equation is a suitable thermody- namic model for absorption-stabilization system, its simulation results are in good agreement with the data from commercial performance test. With the increase of inlet feed temperature of desorption tower, and decreasing the flow rate of absorbent for stabilized gasoline, the energy consumption of the system could be reduced, yet the absorption effect might be reduced as well. Attention should be paid to the bottom temperature of the desorption tower since it might affect the compositions and flow rate of LPG,as well as the C3 and C4 content in dry gas. There is an ideal LPG reflux ratio for stabilizer,in order to obtain improved absorption effect the operating reflux ratio should be less than the ideal value.