What does constant molar overflow mean?
DEFINITION: Constant Molal Overflow (CMO) is the assumption that all liquid (L) and vapor (V) flows (on a molar basis) in the rectifying section are constant and that all liquid (L’) and vapor (V’) flows (on a molar basis) in the stripping section are constant (but not the same as those in the rectifying section).
In which case constant molar overflow is true?
7. In which case Constant Molar overflow is true? Explanation: CMO is totally based on the assumption of equal-molar counter diffusion, mainly used in the calculation of trays in the McCabe Thiele method.
Under what conditions does the McCabe Thiele assumption of constant molar overflow hold?
At the heart of the McCabe-Thiele method for a distillation column composed of equilibrium stages is the constant molar overflow (CMO) condition, which may be stated as follows: in a section of the distillation column where (i) the pressure remains the same, (ii) there are no external streams, and (iii) there are no …
What are the limitations of McCabe-Thiele method?
Limitations of McCabe Thiele Method for Distillation
- It is not used when the relative volatility is less than 1.3 or greater than 5.
- It is not used when more than 25 theoretical stages/plates are required, and.
- It is not used when the operating reflux ratio is less than 1.1 times the minimum reflux ratio.
What does total reflux mean?
Total Reflux is the operating condition where vapor and liquid are passing each other in the column but no product is removed (i.e., D = 0 and R = L/D = ∞ ).
What is Q-line in distillation?
The q-line is that drawn between the intersection of the operating lines, and where the feed composition lies on the diagonal line. Depending on the state of the feed, the feed lines will have different slopes. For example, q = 0 (saturated vapour) q = 1 (saturated liquid)
What is reflux ratio at total reflux?
The reflux ratio is defined as the ratio of the liquid returned to the column divided by the liquid removed as product, i.e., R = Lc/D.
Which method is based on the assumption of constant molar overflow?
McCabe–Thiele method – Wikipedia.
What is CMO in separation?
The total feed entering each stage is formed by mixing the liquid stream leaving the stage above and the vapor steam leaving the stage below. (For vapor-liquid separations the stages are usually stacked vertically, and are referred to as a “column”.) The “Constant Molar Overflow” (CMO) approximation.
What does the McCabe-Thiele diagram tell us?
McCabe-Thiele Method. This method uses the equilibrium curve diagram to determine the number of theoretical stages (trays) required to achieve a desired degree of separation.
Which of the following is explained by using McCabe-Thiele plot?
Which of the following is explained by using McCabe-Thiele plot? Clarification: The McCabe-Thiele plot is a basic tool to assist distillation. It is a method to calculate the number of theoretical trays required for the distillation process of a binary mixture.
What is a good reflux ratio?
approximately 1.2 to 1.5 times Rmin
The total cost, which is the sum of fixed cost and operating cost, must therefore passes through a minimum. The reflux ratio at this minimum total cost is the optimum (or economical) reflux ratio. Typically the optimum reflux ratio is approximately 1.2 to 1.5 times Rmin.
Is Q line same as feed line?
The Feed Line (q-line) The q-line is that drawn between the intersection of the operating lines, and where the feed composition lies on the diagonal line. Depending on the state of the feed, the feed lines will have different slopes. For example, q = 0 (saturated vapour)
What is RMIN in distillation?
Rmin = 1/xF * 1/(a-1) xF is the mass fraction in the feed and is 0.8, a is the relative volatility, which has been taken average from top and bottom of the column and is 77. This will give a minimal reflux of 0.016. Usually the optimal reflux is somewhere between 1.1 and 1.5, say 1.3, which in this case would be 0.021.
What are the assumptions of Mccabe Thiele method?
the molar heats of vaporization of the feed components are equal; for every mole of liquid vaporized, a mole of vapor is condensed; and. heat effects such as heat of solution are negligible.
What is the Q-line in distillation?