Horton-Franklin equation

In order further to simplify the computations, Edmister [13] has written the Horton-Franklin equations in terms of average or effective absorption and stripping factors instead of the /I s and iS s for each tray. Thus, for absorption, Eq. (8.102) becomes... 

Horton and Franklin (1940) used the average absorption factor approach in analyzing a number of absorbers in the petroleum industry. Edmister (1943) extended the Horton and Franklin concept, retaining the Kremser equation form and making use of several empirical factors. He used an effective absorption factor Ae and a modified absorption factor A, given by... 

Values of A and 5 at the top and bottom stages are based on assumed temperatures and on total molal vapor and liquid rates leaving the stages. Total flow rates can be estimated by the following equations of Horton and Franklin." ... 

As a result, for the tray-to-tray calculations suggested above, not only must the outlet gas temperature be guessed but also the complete outlet gas composition, all to be checked at the end of the calculation. This becomes so hopeless a trial-and-error procedure that it cannot be done practically without some guidance. This is provided through an approximate procedure, either that offered by the Kremser equations, which apply only for constant absorption factor, or through some procedure allowing for variation of the absorption factor with tray number. To establish the latter, we first need an exact expression for the absorber with varying absorption factor. This was first derived by Horton and Franklin [21] as outlined below. 

Equations (8.109) and (8.112) can be used to determine the number of equilibrium trays required to absorb or strip a component to a specified extent and to estimate the extent of absorption or stripping of all other components. This then provides a basis for using the exact equations of Horton and Franklin, Eqs. (8.102) and (8.103). These latter can be used only for an integral number of equilibrium trays. A change of Lq/ C v may be necessary to meet the specifications exactly with such an integral number alternatively the nearest larger integral number of trays may be accepted. 

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