#### Absorption Columns: Screencasts

Describes an absorption 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.

Uses an interactive simulation to demonstrate how various process parameters affect the number of stages in an absorption column that is used to transfer a solute from a gas phase to a liquid phase.

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).