Abstract:

In establishing the mechanistic dynamic model of flash tank, a commonly used industrial chemical unit, the liquid-phase characteristic equation is differential, while the gas-phase characteristic equation is algebraic, treated as "quasi-steady-state". Therefore, the realistic dynamic response of pressure can not be obtained, but is completely attached to the dynamic response of the liquid-phase. In this paper, the algebraic equation of pressure was replaced with dynamic differential equation and the model to two-time scale was established. The singular perturbation method was used to precisely calculate the full-order model, and compared with the quasi-steady-state model. The control system for the established two-time scale model was designed. Compared with the performance of quasi-steady-state model, the full-order model provided better control performance, which also illustrated the rationality of modeling and its practical significance.

Key words: dynamic modeling, dynamic simulation, process control, quasi-steady-state, two-time scale modeling, singular perturbation, control performance

摘要：

闪蒸罐是工业常用的化工单元设备, 在对其进行动态机理建模时, 气相物质的动态特性方程被拟稳态处理转化为稳态代数方程, 而液相仍为微分方程。由此一来, 与气相相关的压力的真实动态信息无法得到, 而是完全依赖于液相相态的变化。基于闪蒸罐的化工动态学机理和“拟稳态”的系统特点, 通过增加快变量的动态物料守恒关系式, 还原系统的气相快暂态过程, 建立了TE过程闪蒸罐的双时间尺度全阶模型。利用奇异摄动方法将全阶模型精确求解后, 与拟稳态模型进行了仿真对比;最后, 设计了全阶模型的压力控制回路, 得到很好的控制效果, 验证了建模方法的合理性和工业应用价值。

关键词: 动态建模, 动态仿真, 过程控制, 拟稳态, 双尺度建模, 奇异摄动, 控制性能