ETBE Synthesis via Reactive Distillation. 1. Steady-State Simulation and Design Aspects

Abstract

Ethyl tert-butyl ether (ETBE) is an alternative gasoline oxygenate that combines the blending properties of methyl tert-butyl ether (MTBE) and the renewability of ethanol. Technologically, the best means of synthesis utilizes reactive (or catalytic) distillation to maximize hydrocarbon conversion and energy efficiency while simultaneously producing a high-purity ether product. Mathematical models of reactive distillation are based on the conventional distillation process with supplementary equations added to model the reactions present. Ether-alkene-alcohol systems are highly nonideal in the liquid phase so that careful selection of physical property routines is required to ensure satisfactory simulation results. Column simulations performed here using both Pro/II and SpeedUp show excellent agreement with previously published experimental data for a MTBE system and also agree well with each other for both MTBE and ETBE systems. A homotopy analysis was performed on the tuned simulation models to determine the effects of key design and operating variables on column performance and, subsequently, to develop a design method for reactive distillation columns. Some unusual behavior was identified in ETBE reactive distillation columns compared with either MTBE columns or conventional distillation.

Pattern-based predictive control for ETBE reactive distillation

“…The reaction is equilibrium limited in a range of temperatures. The reaction kinetics has been investigated in [6] and discussed in [3], from where detailed expressions for the equilibrium constant and rate equation are available.…”

“…Measurement points are also indicated in Figure 1 for temperature, flow rate, pressure, and level variables. More information about the the architecture of the RD process can be found in [3,4,7].…”

“…While more complex expressions of T 7 dynamics can be precisely established from the first principles of mass balance and energy balance, e.g. [3,4], these types of models are difficult to use for control design.…”

“…PI control, cannot provide satisfactory control performance, while the application of modern control technology requires good process models. A reasonable process model as described in [3,4] contains hundreds of equations for the 10-stage RD process under consideration. It is too complicated to be directly used for control system design.…”

“…Although it is possible to develop a reasonable model for specific RD processes [3,4], such a model is too complex for control design. Furthermore, RD processes contain a large degree of uncertainties that cannot be well described in process modelling.…”