外部环流反应精馏塔的分散控制方案设计

Decentralized control system designs for reactive distillation columns with external recycle

对于具有最不利相对挥发度排序(即反应物为最轻和最重组分,生成物为中间组分)的四元反应分离物系而言,在反应精馏塔的顶部和底部之间引入外部环流能够提高系统的反应分离效率,从而大幅度地降低系统的能量消耗和固定投资成本。以理想四元可逆放热反应的分离为例,研究了外部环流反应精馏塔的分散控制方案的设计问题。结果表明外部环流的引入提高了系统的反应速率,使得外部环流反应精馏塔的闭环控制效果更好(与传统反应精馏塔相比),对干扰的处理能力更强。另外,由于外部环流反应精馏塔比常规反应精馏塔有更多的操作变量(即外部环流流量),利用该变量对出料浓度进行控制,可以进一步提高系统的闭环控制效果。

For a quaternary reaction separation system having the most unfavorable relative volatility order(i.e.,the reactant is the lightest and heaviest component,the product is the intermediate component),an external is introduced between the top and bottom of the reactive distillation column.The seperation for an hypothetic ideal reversible exothermic reaction was taken as an illustrative example to study the problem of the decentralized control system designs.The results show that the reactive distillation columns with a top-bottom external recycle has better closed-loop control performance and stronger controll ability in the face of large disturbances as compared to the conventianal reactive distillation columns due to the fact that the introducing of external recycle enhance the system reaction rate.In addition,the processes have more operating valuable(i.e.,the external recycle flow rate)compared to conventianal reactive distillation columns;therefore,one can utilize the extra operating valuable to control the product purity.The unique control system can further enhance process closed-loop control performance.