Predicting Multiple Steady States in Equilibrium Reactive Distillation. 1. Analysis of Nonhybrid Systems

Abstract

During the last few years, multiple steady states (output multiplicities) have been discovered for reactive distillation processes, for example, for the production of fuel ethers and for some esterification processes. Using the transformation of Ung and Doherty (Chem. Eng. Sci. 1995e, 50 (1), 23−48), a method is presented to predict the existence of output multiplicities based on the reactive vapor−liquid equilibrium for the limiting case of reactive columns of infinite length operated at infinite internal flows. This graphical method rests upon the ∞/∞ analysis for azeotropic distillation columns by Bekiaris et al. (Ind. Eng. Chem. Res. 1993, 32 (9), 2023−2038). It is directly applicable to systems where the reactions take place in the entire column (“nonhybrid” columns). When all possible profiles and products are located through a bifurcation analysis, qualitative and quantitative predictions are obtained. The region of feed compositions leading to multiple steady states can be constructed graphically by applying a necessary and sufficient geometrical condition. The prediction results are shown to carry over to finite columns by application to the methyl tert-butyl ether process and are verified by simulation.

Biodiesel Production by Reactive Flash: A Numerical Simulation

“…Multiple steady states exist in conventional chemical reactors operated in continuous mode (i.e., continuous stirred tank reactors) and in nonreactive and reactive distillation columns. Investigations of the physical phenomena that cause multiplicities of steady states and Hopf bifurcations in RD have been reported by many researchers around the word [5][6][7][8][9][10][11][12][13][14][15][16][17]. These studies show that there are various reasons for the occurrence of output and input multiplicity, which include multiple steady states caused by heat effects, or kinetic instabilities [6,18,19], or presence of singularities due to nonlinear transformation and decoupling of energy balance [20].…”

Process design in SISO systems with input multiplicity using bifurcation analysis and optimisation

“…A number of published papers have reported input and output multiplicity found in various chemical processes [1][2][3][4][5][6][7][8][9][10][11].…”

Residue curves map analysis for tert-amyl methyl ether synthesis by reactive distillation in kinetically controlled conditions with energy-saving evaluation

“…The potential importance of this method was reconsidered by Bekiaris et al [23] which led to its much use [24]. The method was extended to heterogeneous systems [25], hybrid distillation columns with reactive and non-reactive sections [26,27], process synthesis for finding and ranking feasible separation schemes according to energy consumption, [28] and studying the influence of recycle streams [29]. N/N analysis is able to take into account the energy savings in the early steps of distillation process design and can be used to evaluate new opportunities with the existing distillation systems.…”