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Reactive Distillation (reactive + distillation)
Terms modified by Reactive Distillation Selected AbstractsInteraction of separation and reactive stages on ETBE reactive distillation columnsAICHE JOURNAL, Issue 3 2004Budi H. Bisowarno Abstract Reactive distillation is a favorable alternative to conventional series of reactor-distillation processes for ether productions. However, the design of such columns is complicated due to the interaction between vapor-liquid equilibrium and reaction rates. There are conflicting reports on whether adding excessive separation stages degrade the column performance. A comparison is made of several designs of single and double feed reactive distillation columns for ETBE production to investigate the effects of separation and reaction stages on the overall performance. The explanations are presented using simulation results, whose mathematical models are written in the Aspen Plus environment. The results confirm that a conservative approach by adding extra separation and reaction stages can be applied to reactive distillation design. However, output multiplicity may be observed for longer column and should be considered in the early design phase. © 2004 American Institute of Chemical Engineers AIChE J, 50: 646,653, 2004 [source] A generic feasibility study of batch reactive distillation in hybrid configurationsAICHE JOURNAL, Issue 5 2009C. Stéger Abstract A new graphical feasibility method is developed to investigate batch reactive distillation processes in middle vessel column. The suggested methodology can deal with fully reactive, nonreactive, and complex column configuration. A new formulation is suggested to describe the composition profiles in the reactive sections. Its application has made possible to develop a generic feasibility methodology containing the same model equations independently of the presence or absence of reaction. By combining the reactive and nonreactive models, not only the fully reactive and fully nonreactive but also hybrid configurations can be studied. Feasibility criteria related to the hybrid configurations are also presented. Application of the new methodology is demonstrated on the production of ethyl acetate in batch reactive distillation. Five configurations are found feasible; pure EtOAc is produced as distillate, and pure H2O is produced at the bottom. In each case, continuous feeding of AcOH is necessary. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Design of reactive distillations for acetic acid esterificationAICHE JOURNAL, Issue 6 2005Yeong-Tarng Tang Abstract The reactive distillation provides an attractive alternative for reaction/separation processes with reversible reactions, especially for etherification and esterification. The discrete nature of chemical species and the complexity of phase equilibria seem to cloud the picture in understanding reactive distillation. The esterifications of acetic acid with five different alcohols, ranging from C1 to C5, are studied. First, qualitative relationships between macroscopic process flowsheet and microscopic phase equilibria are established, and the process flowsheets are classified into type I, II, and III for these five systems. Next, a systematic design procedure is devised to optimize the design, based on the total annual cost (TAC) and dominant design variables are identified for different flowsheets. Once quantitative design is available, process characteristic are analyzed and potential problems in process operation are identified. Finally, the economic potentials of these three different flowsheets are explored and explanations are given. The results clearly indicate that it is possible to systemize the design of reactive distillation by qualitatively generating flowsheet from phase equilibria and by quantitatively completing the process flow diagram from a sequential design procedure. Moreover, some of the flowsheets presented in this work cannot be found elsewhere in the open literature. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Experimental study of feasibility in kinetically-controlled reactive distillationAICHE JOURNAL, Issue 2 2005Madhura Chiplunkar Abstract Bifurcation studies predict limited ranges of feasibility for products in certain reactive distillations. These are closely related to the bifurcations in the singular points of dynamic models for simple reactive distillation (isobaric open evaporation with liquid phase reaction). A new dynamic model is described with constant vapor rate together with an experimental study for the reactive distillation of acetic acid with isopropanol to produce isopropyl acetate, catalyzed by Amberlyst-15 ion-exchange resin. An experimental apparatus with real-time measurement of liquid compositions based on Fourier transform infrared (FTIR) spectroscopy is described, and used to follow the composition dynamics at several initial conditions and Damköhler numbers (Da). The experimental results match model predictions that show four regions of behavior. For Da , 1, these show a stable node at acetic acid and several other fixed points as saddles. However, near Da , 2, both isopropanol and acetic acid are stable nodes and a quaternary singular point appears. The presence of two stable nodes requires the presence of a distillation boundary and, therefore, a limited feasibility for the bottom product compositions from continuous reactive distillation. For the reaction rates studied, the model predictions are closely consistent with the experimental findings, and are robust to variations in the vapor rate. These experiments are among the first to analyze the dynamics and feasibility in a kinetically-controlled reactive distillation and are consistent with previous studies for the reaction equilibrium limit, indicating the formation of a reactive azeotrope. © 2005 American Institute of Chemical Engineers AIChE J, 51: 464,479, 2005 [source] Shortcut method for kinetically controlled reactive distillation systemsAICHE JOURNAL, Issue 6 2003J. W. Lee A geometric-based shortcut method for reactive distillation is addressed. The rectification body method for nonreactive distillation, the concept of critical Damköhler numbers, and the geometric design method for reactive distillation are combined with a new eigenvector analysis of pinch points. This shortcut method provides a minimum or reasonable Damköhler number for a given heat duty, as well as the design implication of how to effectively distribute reaction zones inside a column. This method can be used for a fast screening of process design alternatives and for an initialization of rigorous optimization. [source] Effect of chemical kinetics on feasible splits for reactive distillationAICHE JOURNAL, Issue 3 2001Nitin Chadda Feasible direct and indirect sharp splits for multicomponent single-feed continuous reactive distillation are predicted with a model, in which each column section is represented by a series of cocurrent isobaric flashes. In the limits of no reaction and equilibrium chemical reaction, the model reduces to conventional models for distillation lines, and each column section can be represented by the same equations. At intermediate reaction rates, however, the models for the column sections differ, and new results for fixed points and feasible products are obtained. A bifurcation study shows the limits of feasibility, including the influence of flow rate, catalyst level and holdup. Unlike distillation without reaction, limited ranges of feasibility in all of these variables are found. The method has been applied to five examples, one of which is described in detail. Feasibility predictions are validated by column simulations. [source] Effects of Liquid Holdup in Condensers on the Start-Up of Reactive Distillation ColumnsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2006H.-X. Wu Abstract Compared with start-ups in conventional distillation columns, those in reactive distillation (RD) columns are much more time and energy consuming, and generate a large amount of by-products which are not easy to deal with together. For several years, researchers have been trying out different methods to shorten the time required to lower the cost of the start-up. In this work, a rigorous dynamic model in the ChemCAD simulator is applied to model the start-up process for the esterification of ethyl acetate in a reactive distillation column. In the model, two sets of equations are employed: one for the fill-up and heating stage and the other for the equilibration process which follows. In the fill-up and heating stage, fluctuation curves of the reboiler temperatures with respect to time which are similar to those for conventional distillation columns are observed, while in the equilibration process it is found that the increase of the liquid holdup volume in the condenser reduces the time required to reach steady state for the reactive column and decreases the liquid holdup volume in the reboiler at the equilibrium state. This shows that the liquid holdup volume in the condenser has an important effect on the start-up of reactive distillation columns. [source] Design of reactive distillations for acetic acid esterificationAICHE JOURNAL, Issue 6 2005Yeong-Tarng Tang Abstract The reactive distillation provides an attractive alternative for reaction/separation processes with reversible reactions, especially for etherification and esterification. The discrete nature of chemical species and the complexity of phase equilibria seem to cloud the picture in understanding reactive distillation. The esterifications of acetic acid with five different alcohols, ranging from C1 to C5, are studied. First, qualitative relationships between macroscopic process flowsheet and microscopic phase equilibria are established, and the process flowsheets are classified into type I, II, and III for these five systems. Next, a systematic design procedure is devised to optimize the design, based on the total annual cost (TAC) and dominant design variables are identified for different flowsheets. Once quantitative design is available, process characteristic are analyzed and potential problems in process operation are identified. Finally, the economic potentials of these three different flowsheets are explored and explanations are given. The results clearly indicate that it is possible to systemize the design of reactive distillation by qualitatively generating flowsheet from phase equilibria and by quantitatively completing the process flow diagram from a sequential design procedure. Moreover, some of the flowsheets presented in this work cannot be found elsewhere in the open literature. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Experimental study of feasibility in kinetically-controlled reactive distillationAICHE JOURNAL, Issue 2 2005Madhura Chiplunkar Abstract Bifurcation studies predict limited ranges of feasibility for products in certain reactive distillations. These are closely related to the bifurcations in the singular points of dynamic models for simple reactive distillation (isobaric open evaporation with liquid phase reaction). A new dynamic model is described with constant vapor rate together with an experimental study for the reactive distillation of acetic acid with isopropanol to produce isopropyl acetate, catalyzed by Amberlyst-15 ion-exchange resin. An experimental apparatus with real-time measurement of liquid compositions based on Fourier transform infrared (FTIR) spectroscopy is described, and used to follow the composition dynamics at several initial conditions and Damköhler numbers (Da). The experimental results match model predictions that show four regions of behavior. For Da , 1, these show a stable node at acetic acid and several other fixed points as saddles. However, near Da , 2, both isopropanol and acetic acid are stable nodes and a quaternary singular point appears. The presence of two stable nodes requires the presence of a distillation boundary and, therefore, a limited feasibility for the bottom product compositions from continuous reactive distillation. For the reaction rates studied, the model predictions are closely consistent with the experimental findings, and are robust to variations in the vapor rate. These experiments are among the first to analyze the dynamics and feasibility in a kinetically-controlled reactive distillation and are consistent with previous studies for the reaction equilibrium limit, indicating the formation of a reactive azeotrope. © 2005 American Institute of Chemical Engineers AIChE J, 51: 464,479, 2005 [source] | ||||||||||