Theory

The theory of batch distillation permits design, operation and optimization calculations by integrating the concepts of thermodynamic equilibrium, mass and heat transfer, energy and material balances to solve the problem of predicting the compositions and flow rates of process streams. The traditional approach to the development of governing equations is to model the equipment as a stack of equilibrium stages. Departures from ideality are taken into account by introducing the concept of stage efficiencies. Modelling in terms of equilibrium stages is convenient because of the availability of extensive equilibrium data for multicomponent systems and the associated predictive thermodynamic models. Packed columns, which do not possess physical mass transfer stages, can be translated into this technical framework by the use of the transfer unit concept (see, for example, McCabe et al., 1993).

Relinquishing or including levels of complexity and interdependence in the fundamental equation and process variables will result in more or less rigorous treatments, with gains in accuracy usually being accompanied by substantial drawbacks in complexity and computational difficulty. Hereunder, three different sets of model equations are presented in decreasing levels of complexity. A rigorous approach to the problem involves the solution of a set of time-dependent differential and algebraic equations for the material and heat balances and for the equilibrium relations. Batch columns are usually constructed so that there is only one section, either above or below the feed stage. The typical column design depicted in Figure 1 represents the rectifying section. From this simplification it is possible to write the following equations to define the problem completely in each stage except the top stage and the feed drum (reboiler).

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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