#### Stripping Columns: Screencasts

Describes a stripping column, demonstrates mass balances, and shows how to calculate the number of equilibrium stages

We suggest that after watching this screencast, you list the important points as a way to increase retention.

Demonstrates how mass balances and an equilibrium equation are used to count stages graphically on a y versus x diagram (gas-phase solute concentration versus liquid-phase solute concentration) for a stripping column.

We suggest that after watching this screencast, you list the important points as a way to increase retention.

##### Important Equations:

Solute mole balance for stage 1 to stage n (where n is any integer from 1 to N, where N is the total number of stages)

$x_0 L + y_{n+1} V = x_n L + y_1 V$

$$y_{n+1} = \frac{L}{V} (x_n – x_0) + y_1$$    (operating line on y versus x plot)

where $$L$$ = liquid molar flow rate, $$V$$ = gas molar flow rate, the mole ratios of solute are for the following streams:

$$x_0$$: liquid feed to column (stage 1)

$$y_1$$: gas stream leaving column (stage 1)

$$y_{n+1}$$: gas stream entering stage n

$$x_n$$: liquid stream leaving stage n

Solute mole balance around stage n

$x_{n-1}L + y_{n+1}V = x_n L + y_n V$

where the mole ratios of solute are for the following streams

$$x_{n-1}$$: liquid entering stage n

$$y_n$$: gas leaving stage n

The streams leaving stage n ($$x_n$$ and $$y_n$$) are in equilibrium

$$y_n = \frac{H}{P} x_n$$    (Henry’s Law)

where $$H$$ = Henry’s constant (atm) and $$P$$ = pressure (atm)

$H = H^0 exp \left( -\frac{E}{R} \left( \frac{1}{T} – \frac{1}{T_0} \right) \right)$

where $$H^0$$ = Henry’s constant at $$T_0$$ (298 K), $$E$$ = activation energy, $$R$$ = ideal gas constant, and $$T$$ = temperature (K).