Distillation column design
Cooling water, steam supply, hot oil systems, these will all have a bearing on your column operations.
Either can provide the large heat-transfer surface required. Column Operating Objectives The first step in column design is specifying the column operating objectives. The vapor holdup on each tray will be assumed to be negligible.
For components with close boiling points, the temperature change over the column is small and relative volatility is almost constant. Seader and Henley wrote in Section The liquid in stage 'n' and the vapour above it are in equilibrium, therefore, xn and yn lie on the equilibrium line.
Distillation column design calculation free download
The chosen design case from the simulation program provides the internal liquid and vapor flows and their physical properties for every stage of the column. Seader and Henley applied the Sundaram and Evans method and showed how the FUG equations were used to solve a simulation problem with constant reflux. The column consists of a cylindrical structure divided into sections by a series of perforated trays which permit the upward flow of vapor. From a practical point of view the boundary of the system of interest is outlined by dashed lines in Figure The FUG shortcut method assumes that the vapor and liquid holdup on each tray is negligible. A continuous distillation system maintains a steady state and is usually used to separate one chemical of interest. For these reasons the design, analysis and optimization of batch distillation columns have deserved attention from several researchers. Rectification 4. This indicates that benzene has a higher concentration in the vapor phase than toluene, that is, benzene is the more volatile component. Some of the less volatile component condenses from the rising vapor into the liquid thus increasing the concentration of the more volatile component MVC in the vapor. Figure-3a shows the behavior of temperature of the saturated liquid and saturated vapor i. It is also evident that unless we can describe how the concentrations and liquid holdups on each tray change with time, we cannot find how the variables of practical significance, such as xD and xB, change with time. During this initial time period liquid holdup in the column increases and approaches a value that is reasonably constant for the remainder of the distillation cycle. These are the McCabe—Thiele assumptions leading to the condition of constant molar overflow in the rectifying section, where the molar flow rates remain constant as the liquid overflows each weir from one stage to the next.
However, excluding the equilibrium line, only two other pairs of lines can be used in the McCabe-Thiele procedure. The liquid in the base of the column is frequently heated, either by condensing steam or by a hot oil stream, and the vapor rises through the perforations to the bottom tray.
The concentration of the MVC steadily falls in the liquid remaining in the still so that enrichment to the desired level of the MVC is not possible. Figure-3b shows an alternative way of representing the vapor—liquid equilibrium in a composition or x—y diagram.
Distillation column design nptel
By means of multiple, countercurrent stages arranged in a two- section cascade with reflux and boil up, a sharp separation between the two feed components is possible unless an azeotrope exists, in which case one of the two products will approach the azeotropic composition. A pump may be added to a thermosyphon reboiler to improve circulation. Although computer-aided methods are more accurate and easier to apply, the graphical McCabe—Thiele method greatly facilitates visualization of the fundamentals of multistage distillation, and therefore the effort required to learn the method is well justified. Minimum boiling azeotropes are much more common than maximum boiling azeotropes. The liquid from the reflux drum is partly pumped back in the column top tray, N with a molar flow rate FR reflux stream and is partly removed as the distillate product with a molar flow rate FD. Is your reflux ratio approximately 1. All the equations above are state equations and describe the dynamic behavior of the distillation column. In this work, to solve the problem, the strategy was to simulate the operation of a batch distillation column with 10 to 50 theoretical stages maintaining the mole fraction of the light component at a value of 0. From that point, the staircase is constructed by drawing horizontal and then vertical lines between the operating line and equilibrium curve, as in Figure, where the staircase is arbitrarily terminated at stage m. If you are estimating this yourself, it is always a good idea to double-check with some outside sources. Figure-3a shows the behavior of temperature of the saturated liquid and saturated vapor i.
A pump may be added to a thermosyphon reboiler to improve circulation. If yes, you have probably selected the optimal number of stages and the correct feed location.
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