Table of Contents
How does pressure affect a distillation column?
the authors state that increasing pressure can decrease the diameter of a distillation column for a given separation. The result is higher efficiency and vapour capacity, and lower column diameter.” However, some other authors state that decreasing pressure can increase the capacity of a distillation column.
Why the reflux is used and how does it affect the size of the distillation tower?
The Reflux ratio is the ratio between the boil up rate and the take-off rate. The higher the reflux ratio, the more vapor/liquid contact can occur in the distillation column. So higher reflux ratios usually mean higher purity of the distillate. It also means that the collection rate for the distillate will be slower.
What affects the reflux ratio?
The liquid level in the reflux drum is directly affected by three variables: distillate flow rate, reflux flow rate, and condenser duty. Condenser duty affects the amount of liquid entering the reflux drum due to condensation of the vapor coming overhead from the column.
What is the relationship between reflux ratio and number of stages?
As reflux ratio increases, less stages are required but larger equipment are now needed to handle the increased reflux liquid and reboiled vapour load. Thus the fixed cost initially decreased but eventually increase again when the reflux ratio approaches total reflux.
How high can a reflux ratio be?
There is no typical reflux ratio. There is however a typical percent above minimum reflux. That’s usually 10 to 15\% unless the column ends up being too tall, like a C3 splitter, then you can use a higher percent above minimum reflux to reduce the number of stages at the expense of a larger diameter.
What is the maximum reflux ratio?
Typically the optimum reflux ratio is approximately 1.2 to 1.5 times Rmin.
Is it possible to increase the reflux ratio of distillation column?
However, it would be at expense of less enrichment achieved than required. Increasing reflux ratio would act in reverse i.e, it would have a disadvantage of increase in duty of condenser and reboiler as load increases. This increases the operation cost of distillation column, however, more enrichment is achieved.
Why does the height of distillation column increase with increasing pressure?
At lower pressure with decreasing pressure boiling point reduction is higher compare to boiling point reduction at higher pressure. If we increase pressure then relative volatility decrease so for the same purity of product more stages required. So height of distillation column will increase.
What is the effect of increasing pressure on reflux ratio?
Increasing pressure increases the temperature required for the separation. So number of trays or the reflux ratio has to be increased to be increased in order to maintain the same distillate composition. It means operating cost increases if increases reflux ratio
What is the relationship between pressure and composition of distillate?
X1(P1-P2) = (P-P2) Increasing the pressure would mean that your distillate will have a decrease in the compositions of the heavier components if temperature remains the same, while your bottoms’ compositions will see an increase in the heavier components.