Distillation-reaction multiple steady states

The design equations for a single-feed distillation column using these variables have been formulated by Barbosa and Doherty (1988a,b,c) (see also Rev, 1994). The procedure has been extended to multiple reactions by several authors (see, e.g., Ung and Doherty, 1994a,b,c, and Kolah et al., 1996). The appearance of multiple steady states in the solution of the DCR equations has also been considered (Huan et al., 1995) in methyl-/ert-butyl ether production. 

First simulation results on steady state multiplicity of etherification processes were obtained for the MTBE process by Jacobs and Krishna [45] and Nijhuis et al. [78]. These findings attracted considerable interest and triggered further research by others (e. g., [36, 80, 93]). In these papers, a column pressure of 11 bar has been considered, where the process is close to chemical equilibrium. Further, transport processes between vapor, liquid, and catalyst phase as well as transport processes inside the porous catalyst were neglected in a first step. Consequently, the multiplicity is caused by the special properties of the simultaneous phase and reaction equilibrium in such a system and can therefore be explained by means of reactive residue curve maps using oo/< -analysis [34, 35]. A similar type of multiplicity can occur in non-reactive azeotropic distillation [8]. 

At this input-output level the following assumptions are considered ( ) steady-state modeling (n) multiple feeds (nfeed ), side draw-off streams (notr Z+), heat streams (n, Z+), reactions rirx Z+) and components (uc Z+) and Hi) single bottom and distillate streams. Component and energy balances are performed over the structure. The component molar balances MC) include the distillate, bottom, feed and draw-off streams and the production (or consumption) of species due to chemical reaction. 

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