Wet scrubber - what happens if you continue to re-circulate a scrubbing liquid?

Hi,
Probably good for you to review this document.
If you don't add make up water, the level of water in the sump will decrease because the gas leaving the tower is saturated. You will damage the pump soon or later.
Other consequences, viscosity, charge of pollutant, superficial tension will increase, and Foam may appear thus will affect the mass transfer.
By the way, check the validity of your model using Henry's law.

Good luck.
Pierre

water will be completely lost with a gas or will be substituted by components of a gas having lower vapor pressure than water has

Agreed, it will stop absorbing when the recirc. absorbent liquid concentration reaches the Henry's Law limit at this operating temp

I appreciate everyone’s input.

To summarize, provided that the solubility limit has not been reached, the ratio of the molar fraction of the chemical in vapor and recycling liquid will simply equal its Henry constant. Chemical concentration in vapor needs to be low (say, <3%) for Henry's Law to apply.

Other factors to consider:
- Need a minimum liquid level in sump to protect pump
- Consider changes in liquid properties, such as viscosity, surface tension, and foam, that can affect mass transfer

Is this correct?

Incorrect.

Mass transfer is impossible once the equilibrium concentration is reached. This is why you make up fresh solvent in a circulation loop—to keep the concentration of a pollutant in the circulating solvent below the equilibrium one. The further the concentration in the circulation loop is from the equilibrium one, the less packing height is required in the scrubber.

This entire "thought experiment" of yours is meaningless; it doesn't work as you believe.

Note that you're ignoring that solvent vapors (e.g., water) are continuously lost with the gas. Also, you're overlooking that Henry's Law assumes a gas component being absorbed is above its critical temperature and therefore insoluble in any solvent.

You should try dynamic modeling of this scrubber, as it's a relatively simple activity.