Design of distillation towers

How to calculate the theoretical plates for the design of a distillation column?

The number of theoretical plates for the design of a distillation column, calculated using graphical methods, is the most accurate. The quantities calculated using empirical formulas are less accurate than those obtained through graphical methods.

The process is quite complicated; you can check out the information on forums – there’s a lot of it.

The theoretical number of theoretical plates is calculated plate by plate through equilibrium stages. The required data or equations include: the gas-liquid equilibrium relationship ； Distillation section operating line equation ； Distillation section operating line equation ； Q-line equation.

The right-angled ladder graphical method (M-T method) is a classic approach for binary distillation. The M-T method is a standard technique for this purpose. This method involves plotting the equilibrium curve of x/y on the x-y coordinate system representing the two-phase composition, as well as the operating line and the q-line that indicate the feed condition. By then drawing continuous steps between the operating line and the equilibrium line, it is possible to determine the required number of theoretical plates and the appropriate position for the feed plate. To obtain more accurate results, appropriate scaling should be used for plotting. The M-T method provides an intuitive representation of the ease of the separation process, especially for illustrating the case of the minimum reflux ratio. The M-T method appears simple because it can directly provide the equilibrium curve. If the gas-liquid equilibrium data are to be calculated from a gas-liquid equilibrium model, this method loses its simplicity.