Efeito da pressão sobre a dinâmica e o controle de colunas de destilação com retirada lateral.

Abstract

Distillation is the most used separation process in chemical and petrochemical industry. As any process, its performance mainly depends on the implementation of an adequate and effective control.Due to the importance and complexity of distillation columns, their control is a topic widely explored in the literature. Despite this fact and the pressure to be one of the most important controlled variables, the effect of this variable on the dynamics and control systems of distillation columns has not been carefully studied. This work aims to present results for different pressure control schemes of a real column, which is part of a production unit of polyethylene. This column is considered unconventional because it has three feeds and four withdrawn, one being a side withdrawal. The simulations of steady and transient state (using Aspen Plus and Aspen Dynamics simulators) showthat disturbances inthe vapor feed stream changes the column pressure, having a strong influence on other process variables such as composition and temperature. The results indicates that the pressure control currently used in the column is not the most effective and that other control schemes can perform better.