Method of statics analysis

Assumptions ( ) the vapor and liquid flow rates in the column are infinitely large (ii) the capacity of the reaction part in the column is large enough to carry out a given conversion rate Hi) the plant is operated at steady state and theoretical stages are chosen and iv) one reversible equilibrium reaction is considered. 

These assumptions allow one to estimate the liquid composition on a tray as the composition of vapor one tray below i.e. Xi = j/i+i) and the profiles may be estimated by using usual distillation lines. 

Description this method considers that composition change due to reaction is negligible on each stage and that RD is a succession of reaction and distillation operations (Giessler et al., 1998), where the feed is firstly converted to a pseudoinitial mixture -with composition X assuming a certain extent of reaction e- w hich is then separated in a distillation column (figure 3.1a). For that pseudo-initial mixture feasible steady states occur when i) the composition X and the product compositions satisfy the mass balance and ii) a part of the distillation line lies inside the forward reaction rate region. 

The munber of theoretical and reactive stages is determined from the distillation line and from the intersection of the distillation line and chemical equilibrium manifold (GEM) and represents the boimdary of the forward and backward reactions) (Giessler et al., 1999). Since there are multiple pairs of X and product composition that satisfy the mass balance, the method sets one of the product composition as reference point and solves for the other two (for a 3-component system) by using material balance expressions. Thus, two of the components compositions and X lie on the same line of mass balance (LMB) in the diagram and allow the estimation of the ratio D/B at a certain reboil ratio only by exploring the ratio of the line segments (figure 3.1f ). 

Limitations i) this method assumes infinite separation efficiency and ii) matching the operating lines with the assumed product composition can be sometimes troublesome. 

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Figure 3.1. Method of statics analysis (adapted from Giessler et al. (1999)).

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