Kirkbride equation

Use the Kirkbride equation, equation 11.62. Product distributions taken from Example 11.6,... 

Locate the feed point from the Kirkbride equation. Equations (6.27.12 and 6.27.13). 

The feed point location is calculated from the Kirkbride equation. Equation 6.27.12. 

To use the Kirkbride equation to determine the feed-stage location, we must first estimate the composition of the distillate and bottoms from the results of Example 6.10. We found there that at total reflux, 99.7% of the LNK (benzene) is recovered in the distillate, 95% of the light key is in the distillate, and 95% of the heavy key is in the bottoms. For a basis of 100 mol of feed, the material balances for... 

Use the Gilliland correlation to estimate the number of ideal stages required for the separation of Example 6.4. Assume that, for the system benzene-toluene at atmospheric pressure, the relative volatility is constant at a = 2.5. Use the results of Problems 6.15 and 6.16. Use the Kirkbride equation to estimate the optimum feed-stage location. 

Although the result from the Kirkbride equation is not very satisfactory, the Fenske ratio method is much worse. 

Example 12.7. Use the Kirkbride equation to determine the feed stage location for the debutanizer of Example 12.1, assuming an equilibrium stage requirement of 18.27. 

Step 5 Estimation of the feed-stage location by the Fenske equation. The calculation is made with Eq. (14.1) by applying it to the section of stages between the feed composition and the distillate composition to obtain the minimum number of rectification stages, and then to the section of stages between the feed and bottoms product to obtain the minimum number of stripping stages, The ratio of to Ns,mm is assumed to be the same as the ratio of to at finite reflux conditions. Alternatively, the empirical, but often more accurate, Kirkbride equation can be applied. 

Distillation columns are designed by setting the total number of trays (Nt) equal to twice the minimum number of trays Nmi and the optimum feed tray is estimated from the Kirkbride equation. 

Next, shortcut methods are applied to find the minimum number of trays (Fenske equation) for distillation columns, locate the feed tray location (Kirkbride equation), and size the... 

Kirkbride equation An equation used for the design of distillation columns to determine the ratio of the number of trays above and below the feed point. It is therefore used to determine the location of the feed tray in the column ... 

Substituting values of mole fraction of LK and HK in feed stream distillate and bottom stream and mole flow rate of bottom and distillate in Kirkbride equation ... 

---