# How can internal reflux be determined from the external reflux?

## How can internal reflux be determined from the external reflux?

In the design of distillation columns, engineers use internal reflux in their calculations rather than external reflux. The most common method of determining internal reflux makes use of external reflux flow measurement and the number of degrees of condensate subcooling* (see Figure 11.1 and reference 15):

## What is reflux ratio in distillation column?

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.

How does reflux ratio affect separation?

In general, the lower reflux rate reduces the methanol purity of the distillate. A higher reflux rate improves the separation at high operating costs.

### What is external reflux ratio?

D/Vn is called as external reflux ratio (ER). The Minimum Reflux Ratio (R min) is the lowest value of reflux at which separation can be achieved with an infinite number of plates. It is possible to achieve a separation at any reflux ratio above the minimum reflux ratio.

### What is reflux ratio at total reflux?

The Reflux ratio is the ratio between the boil up rate and the take-off rate. Or in other words, it is the ratio between the amount of reflux that goes back down the distillation column and the amount of reflux that is collected in the receiver (distillate). Instead we call this “total reflux” or equilibration.

What is maximum reflux ratio?

Typically the optimum reflux ratio is approximately 1.2 to 1.5 times Rmin.

## Which reflux ratio is most suitable?

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.

## What is internal and external reflux ratio?

Ln+1/Vn is called as internal reflux ratio (IR). D/Vn is called as external reflux ratio (ER). At steady state, Ln+1/Vn = 1-D/Vn. 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 = ∞).

How do you find the minimum reflux ratio on a graph?

Minimum Reflux Ratio (Rm) Draw a line from ( xD, yD) passing through ( x1, y1) with an intercept xD / (Rm + 1) on Y axis. Reflux ratio is calculated as 1.5 times the minimum reflux ratio.

### What causes pressure drop in distillation column?

Pressure drop in packed column is due to following reasons: Due to resistance in fluid (generally gas) flow due to downcoming liquid. Due to resistance because of column packing and column internals. Due to some solid particles getting accumulated in packing causing resistance in fluid flow (also causing channeling).

### What happens in a distillation column if the reflux ratio is zero?

If no liquid is recycled back to the column, the internal liquid and vapour flow-rates can not be controlled and the design of the column gets more difficult. No liquid is recycled back to the column.

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.

## How do you calculate internal reflux?

The internal reflux, that is, the actual flow of liquid from tray 1 to tray 2, can be calculated as follows: Cp = Heat capacity of the reflux (e.g., BTU/lb-°F) Λ = Heat of vaporization of the reflux (e.g., BTU/lb)

## What is the difference between total reflux and external reflux ratio?

D/Vn is called as external reflux ratio (ER). 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 = ∞). The slopes of the Operating Lines are then L/V = 1.0, that is by mass balance, between each plate y = x.

What is reflux ratio in column chromatography?

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 = L c /D. Figure 2 also shows the column as a series of theoretical plates. A theoretical plate is defined as a vapor-liquid contacting device such that the vapor leaves it in equilibrium with the liquid which leaves it.