| Global homotopy continuation is used to identify multiple steady states in ideal reactive flash and reactive distillation systems involving a reaction of the form A+B ↔C taking place in the liquid phase. The choice of specifications has an influence on the existence of multiple solutions for both the flash and the column. For the flash, specification of the heat input or withdrawal can give rise to multiplicities while specification of the split fraction does not. Specification of one internal energy balance variable and one external material balance variable does not produce multiplicities in the column; however, specification of two internal energy balance variables can produce multiplicities. This is seen to have implications for the selection of control variables for both the flash and the column.;The effects of the relative volatility between the light and heavy components, the forward rate constant, and the reaction equilibrium constant are studied. It is concluded that both the relative volatility spread and the equilibrium constant exhibit threshold values, below which only singular solutions are obtained. Above this threshold, multiplicities are to be found. The rate constant also affects the appearance of multiple solutions, but the multiplicities are found in regions bounded above and below by regions producing only singular solutions.;The cause of multiplicities in the idealized system studied is seen to be the interaction between consumption and creation of species by reaction and transfer of material between phases. The reaction rate appears to be the major contributor to this effect because it is able to reverse direction, assuming either positive or negative values. |
