Reactive cascade difference points

Reactive cascade difference points are defined as the combined points of stoichiometric coefficients vectors and product compositions. For the isomolar reaction 2R -I-P21 the difference 

Assumptions (i) known top and bottom compositions (ii) known reflux ratio Hi) CMO assumption and iv) chemical reaction of the type 2R Pi + P2. 

This approach is tested in the gas-phase disproportionation of toluene and in the de-hydratation of methanol into water and dimethyl ether. In the first case study the most competitive configuration is reported to be the reaction zone in the stripping and feed sections. The effect of the reaction equilibrium constant is analyzed in the second example, resulting in feasible configurations with a single reactive stage. 

This method is particularly helpful to find fuUy or partially optimized solutions for RD design variables (Malone and Doherty, 2000). The objective function for the RD problem is commonly composed of two basic terms annual operating cost (e.g. consumption of raw materials, steam and cooling water) and the annualized investment i.e. column, internals, reboiler and condenser). The constraints are formed from the MESH equations on each tray, material balances at the top and bottom of the column, kinetic and thermodynamic relationships and logical relationships between process variables and the number of trays. 

Assumptions i) the vapor and liquid phases are in equilibrium on each tray ii) no reaction takes place in the vapor phase (m) the liquid phase is always homogeneous iv) the enthalpy of liquid streams is negligible (w) the heat of evaporation is constant vi) temperature dependence of the reaction rates can be expressed in Arrhenius form and vii) the cost of separating products downstream is given by an anal dical function. 

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The concepts of reactive cascade and scalar/vectorial difference points in reactive cascades (c/. explanatory note 3.2) have been successfully applied by Hauan et al. (2000a) Lee et al. (2000a) and Lee and Westerberg (2000) in the design of RD processes. 

Table 3.2. Qualitative fingerprint of the design methods used in reactive distillation (continuation). Nomenclature. Gi Statics analysis G2 ROM G3 Attainable region G4 Fixed-points G5 Reactive cascade Ge Thermodynamic-based G7 Conventional graphic techniques Gg Phenomena-based Gg Difference points Mi MINLP M2 OCFE M3 MIDO Hi Heuristics. Key. applicable nonapplica ble/nonmentioned A original assumption relaxed by later contributions...

Hauan S., Ciric A., Westerberg A. and Lien K. (2000a). Difference points in extractive and reactive cascades. I. Basic properties and analysis. Chemical Engineering Science 55, 3145-3159. 3.2.9... 

J. W. Lee, S. Hauan, K. M. Lien, and A. W. Westerberg, Difference points in extractive and reactive cascades. II. Generating design alternatives by the lever rule for reactive systems, Chem. Eng. Sci. 55, 3161-3174 (2000). 

The easy access of a hydroxy group of ninhydrin (254) to its substitution and the presence of the carbonyl groups makes this highly reactive compound an interesting starting point for cascade reactions with amino compounds. These have been mechanistically investigated with AFM on six different faces of 254 and strictly relate to the crystal packing [94]. 

We formulate the reactive flash modd for an equimolar chemistry. Next, we hypothesize a condition under which the trajectories of the flash cascade model lie in the feasible product regions for continuous RD. This hypothesis is tested for an example mixture at different rates of reaction. The fixed point criteria for the flash cascade are derived and a bifurcation analysis shows the sharp split products from a continuous RD. 

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