Nonequilibrium stage model condensers

Chapter 12 presents models of mass transfer on distillation trays. This material is used to develop procedures for the estimation of point and tray efficiencies in multicomponent distillation in Chapter 13. Chapter 14 uses the material of Chapter 12 in quite a different way in an alternative approach to the simulation and design of distillation and absorption columns that has been termed the nonequilibrium stage model. This model is applicable to liquid-liquid extraction with very little modification. Chapter 15 considers the design of mixed vapor condensers. 

For the purposes of simulating a packed column the packing was divided into a number of sections each of which is modeled as a nonequilibrium stage as discussed above. The C4 splitter was modeled using 150 nonequilibrium sections, an equilibrium reboiler and a total condenser. The bottom product rate in molar units and the reflux ratio were fixed at the values observed in the plant tests. Additional specifications included the component feed flows and the column pressures. 

Most of the quantities normally specified in an equilibrium stage simulation (number of stages, feed stage location, feed flow rates and composition, reflux ratio, distillate or bottoms rate, and so on) must be specified for a comparable nonequilibrium simulation. By including the hydraulic or pressure drop equations in the model it is not necessary to specify the pressure of each stage for a nonequilibrium simulation only the pressure of the top stage and of the condenser need be specified. 

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