Article Contents

Number of trays in distillation column Distillation is a common process used in the chemical industry for the separation of different components of a mixture based on their boiling points. One of the most important aspects of distillation is the number of trays or plates in a distillation column. This determines the efficiency of the separation process and the quality of the final product. In this article, we will discuss the different methods for calculating the minimum number of stages in a distillation column, the number of theoretical plates formula, and the use of the McCabe-Thiele and Ponchon-Savarit methods in distillation.

number of trays in distillation column

The minimum number of trays in distillation column can be calculated using a number of methods. One of the simplest methods is the Fenske equation, which is based on the relative volatility of the components in the mixture and their mole fractions. The Fenske equation is given by:

N = (ln xD / ln xB) / (ln yD / ln yB)

where N is the minimum number of stages, xD and xB are the mole fractions of the most volatile component in the distillate and bottoms, respectively, and yD and yB are the corresponding mole fractions of the less volatile component.

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Result:

Above equation is use for distilation column tray calculation.

Another method for calculating the minimum number of stages is the Gilliland correlation, which is based on the average relative volatility of the components in the mixture. The Gilliland correlation is given by:

N = (1 / α – 1) x log(xD / xB) / log (yD / yB)

where α is the average relative volatility of the components.

Number of Theoretical Plates Formula The number of theoretical plates in a distillation column can be calculated using the number of theoretical plates formula, which is given by:

N = 5 to 6 (L/V) (dH / ΔH)

where N is the number of theoretical plates, L/V is the height to diameter ratio of the column, dH is the difference in height between two trays, and ΔH is the change in heat of vaporization between two adjacent trays.

McCabe-Thiele Method for Distillation

The McCabe-Thiele method is a graphical method for determining the number of theoretical plates in a distillation column (or to calculate number of trays in distillation column). It is based on the equilibrium relationship between the vapor and liquid phases at each tray in the column. The method involves plotting the operating line and the equilibrium line on a McCabe-Thiele diagram and determining the number of trays required to achieve the desired degree of separation.

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The McCabe-Thiele method is particularly useful for batch distillation, where the composition of the mixture changes as the distillation progresses. The method can also be used to determine the number of theoretical plates for continuous distillation, although it is less commonly used for this purpose.

Fig distillation column tray calculation

Ponchon-Savarit Method

The Ponchon-Savarit method is another graphical method for determining the number of theoretical plates in a distillation column. It is similar to the McCabe-Thiele method, but it involves plotting the operating line and the equilibrium line on a Ponchon-Savarit diagram. The method is particularly useful for distillation columns with a large number of theoretical plates and for mixtures with large relative volatilities.

Tie Line in Distillation

A tie line in distillation refers to a line connecting two points on the McCabe-Thiele or Ponchon-Savarit diagram, representing the equimolar composition of the vapor and liquid phases at a given tray in the dist

ulation column. The length of the tie line represents the degree of separation achieved at that tray, with longer tie lines indicating a higher degree of separation. The position of the tie line on the diagram also indicates the composition of the vapor and liquid phases, with the tie line intersecting the operating line at the vapvapor pressureor composition and the equilibrium line at the liquid composition.

McCabe-Thiele Method for Batch Distillation The McCabe-Thiele method can also be applied to batch distillation, where the composition of the mixture changes as the distillation progresses. In batch distillation, the operating line changes as the distillation progresses, and the number of theoretical plates can be determined by considering the change in composition and the change in the operating line.

conclusion

The number of trays in distillation column is a crucial factor in determining the efficiency and quality of the separation process. There are several methods for determining the minimum number of stages in a distillation column, including the Fenske equation and the Gilliland correlation. The number of theoretical plates can be calculated using the number of theoretical plates formula, and the McCabe-Thiele and Ponchon-Savarit methods can be used to determine the number of theoretical plates graphically. The McCabe-Thiele method can also be applied to batch distillation, where the composition of the mixture changes over time. Understanding these methods and principles is essential for successful distillation operations in the chemical industry.

1.2 number of trays in distillation column