Column distillation stages, calculating number

Distillation stage calculations are usually performed with ideal stages, The number of ideal stages required for the separation is divided by the overall column efficiency (Sec, 7,1,1) to obtain the required number of trays. In packed towers, the number of stages in the column is multiplied by the HETP (Height Equivalent of a Theoretical Plate, see Sec. 9.1,2) to obtain the packed height. 

In this chapter consideration is given to the theory of the process, methods of distillation and calculation of the number of stages required for both binary and multicomponent systems, and discussion on design methods is included for plate and packed columns incorporating a variety of column internals. 

Thus, the key result from the tray-by-tray calculation is that the column design must ensure complete alcohol consumption in the reactive zone, only lauric acid and water are allowed in the top vapor stream. The column behaves more as a reactive absorber than reactive distillation. A higher number of equilibrium stages... 

THIS PROGRAM HILL CALCULATE THE FEED COMPONENT RECOVERY IN BOTH THE COLUMN DISTILLATE AND BOTTOMS PRODUCTS AND ESTIMATE THE MINIMUM NUMBER OP STAGES NEEDED TO PERFORM THE GIVEN SEPARATION. 

The knowledge of the occurrence of azeotropic points in binary and higher systems is of special importance for the design of distillation processes. The number of theoretical stages of a distillation column required for the separation depends on the separation factor i.e. the ratio of the 7< -factors (7required separation factor can be calculated with the following simplified relation (Reference 1) ... 

Consider the distillation column shown in Figure S-7. where all the non-keys are HNKs. Note that the column is now numbered from the bottom up, since that is the direction in which we will step off stages. With no LNK, a good first guess of concentrations can be made at the bottom of the column, and we can start the stage-by-stage calculations by calculating the reboiler tenperature and the values of yj R from a bubble-point calculation. For the bubblepoint calculation, we want to find the tenperature that satisfies the stoichiometric equation. 

For many tasks in process simulation, the vapor pressure is the most important quantity. It is often decisive for the determination of the number of theoretical stages of distillation columns and the calculation of temperature profiles. In environmental protection, the vapor pressure is important to determine the load of a component in exhaust air and to evaluate the options for an exhaust air treatment. Furthermore, a vapor pressure curve that has been carefully evaluated is also useful for the estimation of other thermophysical properties, especially the enthalpy of vaporization. 

The distillation colunm described in Problem 6.2 is to be designed with the provision that the hot process stream will supply only 20 x 10 Btu/hr to the reboiler. It is proposed to supplement the column duty requirements by utilizing another process stream that can supply 10x10 Btu/hr. However this stream is at 200°F, and a temperature approach of 25 is required between the process stream and the column temperature where the heat would be supphed. Determine the optimum locations of the heater and the feed and the total number of equilibrium stages. Calculate the condenser duty. 

Example 3 Calculation of TG Method The TG method will he demonstrated hy using the same example problem that was used above for the approximate methods. The example column was analyzed previously and found to have C -I- 2N + 9 design variables. The specifications to be used in this example were also hstedat that time and included the total number of stages (N = 10), the feed-plate location (M = 5), the reflux temperature (corresponding to saturated liquid), the distillate rate (D = 48.9), and the top vapor rate (V = 175). As before, the pressure is uniform at 827 kPa (120 psia), but a pressure gradient could be easily handled if desired. 

This type of calculation does not have to be carried out for a plate column because the two phases are well mixed on each plate. This means that on each individual plate a state of equilibrium can be presumed. Therefore a volume element is identical to an equilibrium stage, and the height of the column can be obtained from the number of equilibrium stages required for a particular separation. This is a thermodynamic rather then mass transfer problem. This explains why a mass transfer device, such as a distillation column can be sized without any knowledge of the laws of mass transfer. 

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