Evaluation of the Dynamics of a Distillation Column with Two Liquid Phases

• Main Authors: G. Marinho Cordeiro, S. Dantas, L. Vasconcelos, R.P. Brito
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2013-06-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/6733

Distillation is one of the oldest and most important separation processes used in chemical process industry. On the other hand, it presents extremely low thermodynamic efficiency, accounting for the largest percentage of the overall energy consumption of a plant. In this sense, distillation is the most referred process when it comes to energy consumption. The present work was initiated with a search for the reduction in the energy consumption in a distillation train of 1,2-dichloroethane (EDC) of a commercial plant for producing vinyl monochloride (MVC), which involves azeotropic distillation. The results obtainedusing the commercial simulator AspenTM show that the reduction in the reboiler heat duty caused significant changes in both concentration and temperature profiles throughout the column due to the formation of two liquid phases. This fact is an indication that the occurrence of this 2nd liquid phase causes significant changes in the operation of the column as well as on the separation to be obtained. The results also show that the operation of the column with two liquid phases throughout some stages still satisfies bottom product specification (mass fraction of H2O), and also consume less energy. The formation of two liquid phases occurs even with a reduced amount of H2O present in the feed stream. Therefore, it is necessary to verify the feasibility of operating such a column with the presence of two liquid phases, requiring, therefore, the evaluation of the dynamics of the process which will also be useful for controllability purposes. The results indicate that the temperature of some of the stages of the column canact as an indicator about the formation of the 2nd liquid phase. Therefore, controllers that maintain the parameters of the processes at acceptable levels must be proposed avoiding controlling the temperature of stages with two liquid phases.