Design distillation device

Once one has proposed alternative configurations for systems of separation devices to effect a desired separation, one must then design these devices so the various alternatives may be compared. For a distillation column, the first set of design decisions is to choose the number of trays, the feed tray location, and the reflux ratio at which to operate it. For a binary separation, the McCabe-Thiele diagram (or the concepts behind it) is an indispensable aid in making these decisions. 

Simple Distillation. In this category, we include the separation of ideal or slightly non-ideal mixtures that do not form azeotropes, based on the differences in the relative volatilities of components. A simple column designates a device that separates one or several feeds in only two products top distillate and bottoms. Complex columns are can deliver more than two products. In this category we include columns with side-streams, columns equipped with auxiliary devices, as prefractionators, side-strippers and side-rectifiers, as well as thermally integrated columns. 

K. I. Sotowa, K. Kusakabe, Design of mi-crochannels for use in distillation devices,... 

All the foregoing test programs involve distillation of well-defined mixtures under total reflux conditions. The primary value of the results is in the comparative data, but it should be emphasized that the design of each device was not necessarily optimized for the test conditions. 

A common type of distillation contacting device used in refinery applications is the sieve tray. In the early 50 s and for many years before, the bubble cap tray was the mainstay of the distillation field. A sieve tray consists of a flat plate with regularly spaced holes, normally 1/2 to 1 inch in diameter. Liquid flows horizontally across the tray and into a channel, called a downcomer, which leads to the tray below. The sieve tray exhibits good capacity, excellent efficiency, low pressure drop, and good flexibility i.e., it will operate quite efficiently at tower loadings which are 1/2 to 1/3 of design values. 

Initial Extraction Technique Continuous extraction apparatus was employed, including an extractor designed to contain the starting plant materials, a distillation flask to hold the solvent mixture, the flask being equipped with a reflux condenser, a drip device to facilitate the removal of the volatilized mixture from the condenser and to percolate it through the continuous extractor, and a Soxhiet type return. Means for heating the continuous extraction system were provided. 

Finally, if vaporization of a liquid is required for applications other than distillation, then the same principles and methods can be applied. The one distinctive difference is that with all designs, with the exception of kettle designs, a vapor-liquid separation device will be required at the vaporizer outlet, as illustrated in Figure 15.15. 

It has already been noted that trays which are suitable for distillation may be used for absorption duties though in general lower efficiencies will be obtained. In Chapter 11, the design of trays for common contacting devices is considered and the methods presented in that chapter are generally applicable. The most commonly used tray types are shown in Figure 11.50a with the crossflow tray being the most popular. 

A device described by Sawyer and Dixon [13] was used for the determination of alcohol and acid in beer and stout. Attempts to improve the reliability of this method and to improve the signaTto-noise characteristics of the measurements prompted a critical design described by Lidzey et al. [14]. This unit overcomes many of the fluctuations in results observed with use of the first unit in this a number of possible sources of surging were indicated and these were not controlled owing to the varying conditions in the coil. In addition, the separation of the waste involatile material from the volatile phase took place outside the heated flask distillation unit. Air bubbles present in the segmented stream were also responsible for considerable surging. 

Unfortunately, most of Kitaibel s work was never published, but his manuscripts preserved at the Hungarian National Museum in Budapest show that he was an ingenious designer of chemical apparatus, such as a salt-evaporating pan which utilized the heat of the fuel gas on the countercurrent principle a device for the saturation of mineral water with carbon dioxide apparatuses for vacuum filtration and for the distillation of water and an improved lime kiln and brick kiln (12). 

These reactants A and B are thus brought together in a reactor with the required temperature, pressure and catalysts to speed up the reaction. It is important that the reactor is designed with a suitable material of construction in such a manner that chemicals A and B spend the required reaction time. The final step might be to send the product to a continuous distillation unit or to a settling tank or to any other device which may be called as a separator which would separate C away from other chemicals in the stream. The additional... 

Therefore, adopting the solution of reactive distillation instead of separate reaction and separation units does not lead automatically to a more efficient process. Matching the conditions of separation and reaction in the same device requires careful design. The element with the highest impact is the chemical reaction. The key condition for an efficient and competitive process by reactive distillation is the availability of a superactive catalyst capable to compensate the loss in the driving force by phase equilibrium, but at the same time ensuring a good selectivity pattern. 

---