Absorber sizing equilibrium stages

Equilibrium-stage methods are usually adequate for nearly ideal distillation systems when coupled with calculations of plate efficiency to estimate actual trays or, in the case of packed towers, when HETS (height equivalent of a theoretical stage) or HETP (height equivalent to a theoretical plate) values are known from experience or from experiment to enable the estimation of packed height. For absorbers, strippers, and nonideal distillation systems, mass-transfer models are preferred, but their use requires a value for the tower diameter and a tray layout or type and size of packing. Even when mass-transfer models are preferred, initial calculations are usually made with equilibrium-stage models. Also, note that data for reliable mass-transfer coefficients is often difficult to obtain. 

Several rigorous modules may be available in a given simulator. Differences between the modules are the different solution algorithms used and the size and conplexity of the problems that can be handled. Tray-to-tray calculations can be handled for several hundred stages in most simulators. In addition, these modules can be used to simulate accurately other equilibrium staged devices, for exanple, absorbers and strippers. 

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