Tips to Scale-up & Design

Evaporation / Distillation

Guidelines for the Number of Distillation Separation Stages (0902)
Distillation calculation is the unit operation that benefited the most of the development of computers. Until the 1970’s, sequential stage calculations by large computers (mainly engineering companies) and the McCabe-Thiele method (chemical companies) were mainstream, but now the use of PC based process simulators is widespread. Using a simulator makes it easy to calculate, but the conditions for starting case studies can be quite different depending on individual skills. Whereas experienced engineers may undertake efficient investigations close to the solution, it is also true that beginners do not know where to start from. In this sense, having guidelines for determining the number of stages is important for efficient examination. Here, we will introduce these guidelines for continuous distillation and batch distillation.　(Y. Kumagae)
Guidelines for Distillation Column Thermal Analysis and Optimal Reflux Ratio (0907)
Previously we introduced how the state of a distillation tower can be considered from the thermodynamic minimum energy by using the column targeting method. This time, improvements to a distillation tower will be concretely considered by using the column targeting method. In addition, the optimal reflux ratio that minimizes the total of the equipment and operation costs of the distillation tower and peripheral equipment will be discussed. (H. Taguchi)
Calculation of Minimum Number of Theoretical Stages using Fenske Equation (1009)
When performing a new distillation calculation, it is necessary to determine the theoretical number of stages (and/or the reflux ratio) after determining the operating pressure. A plotting method using the McCabe-Thiele method is also effective, but it is difficult to apply to multicomponent systems. On the other hand, there is a shortcut method that is often used as a guideline for multicomponent distillation calculation. In this shortcut method, the minimum number of theoretical stages and the minimum reflux ratio are obtained, and then the theoretical number of stages and the reflux ratio can be determined by using Gilliland’s correlation. For systems that are not strongly non-ideal, it is an effective method to estimate rough values. Here, we will introduce the Fenske equation for finding the minimum number of theoretical stages. (H. Taguchi)
Effect of Pressure on Distillation Separation Operation (1205)
Generally, it is known that, for distillation, separation tends to be enhanced by lower pressures. For two components, the ease of distillation separation can be judged from the value of the relative volatility (α). Here, we will take typical substances as examples and examine the effect of pressure changes on their relative volatilities. (H. Taguchi)