R. Bruce Eldridge

Dynamic rate-based and equilibrium models for a packed reactive distillation column

Dynamic rate-based and equilibrium models were developed for a packed reactive distillation column for the production of tert-amyl methyl ether (TAME). The two types of models, consisting of differential algebraic equations, were implemented in gPROMS and dynamic simulations were carried out to study the dynamic behaviour of reactive distillation of the TAME system. The dynamic responses predicted by the two types of models are similar in general, with some differences in steady-state values. The influence of manipulated variables, such as distillate flow rate, reflux ratio, and reboiler duty, on the dynamic responses of the controlled variables (reactant conversion and product purity) was studied. The dynamic response of reactant conversion is very nonlinear and unconventional, but the response of product purity is well approximated by a linear first-order differential equation. The CPU time required to complete a dynamic simulation of the rate-based model is at least an order of magnitude higher than that for the equilibrium model. Therefore, the dynamic rate-based model is much more complicated than the equilibrium model, and simplification of the rate-based model is necessary for the implementation of model-based control. A new approach was proposed to simplify the dynamic rate-based model by assuming that the mass transfer coefficients are time invariant. This approach was demonstrated to be superior to the conventional simplification methods. It can reduce the number of equations by up to two-thirds and still accurately predicts the dynamic behaviour.

The experimental application of X-ray tomography to a vapor-liquid contactor

Abstract Initial results obtained from the application of X-ray tomography to an operating vapor–liquid contactor indicate that the technology has the potential to provide insight into the underlying hydraulic behavior of a packed column. Experiments were performed with counter-current air–water flows in a 6-in-diameter contactor packed with random packing. Liquid and gas velocities typical of a commercial column were tested. Liquid distribution patterns and holdup values were obtained for three tower elevations. The majority of liquid holdup values obtained from the tomography experiments were within 15% on the parity plot of model versus experiment. The experimental flow patterns for random packing showed a preference for the liquid stream to flow in rivulets.

Hybrid Separations/Distillation Technology. Research Opportunities for Energy and Emissions Reduction

This report focuses on improving the existing separations systems for the two largest energy-consuming sectors: the chemicals and petroleum refining industries. It identifies the technical challenges and research needs for improving the efficiency of distillation systems. Areas of growth are also highlighted.

EXPERIMENTAL VALIDATION OF MODEL-BASED CONTROL STRATEGIES FOR MULTICOMPONENT AZEOTROPIC DISTILLATION

Abstract This work presents the results from dynamic modeling and control of an azeotropic distillation system. The model was validated with experimental data from a packed distillation unit. The physically-based process dynamic model, developed in HYSYS, was linked online with the control software used in the process. Model parameters were modified online using a feedback configuration to eliminate the difference between the process and model outputs. The fundamental model was used in the implementation of different control strategies, including a multivariable control strategy using model predictive control (MPC) software Predict Pro, via an inferential control strategy to treat missing process measurements.