Does calcium hydroxide precipitate in a "reactor"

[sfsuphysics]

Just trying to wrap my mind around how reactors work the way they do as you apparently have a saturated (full strength) solution of kalkwasser yet you're supposedly putting in more than what will saturate it so that when you do top off and freshwater replaces what you used there's still calcium hydroxide mix in the "reactor" so you can keep your kalkwasser at full saturated strength.

I'm not a chemist, nor pretend to be :), is it something about freshwater that doesn't make it precipitate? Or the reactor is a sealed environment so very little CO2 infiltration?

[Habib]

Kalkwasser is the same as calcium hydroxide solution.

The calcium hydroxide only dissolves in a limited amount.
All that is added more does settle.

When the calcium hydroxide solution is (partly) replaced by freswater, some of the settled calcium hydroxide will dissolve until the limit of what is soluble is reached.

So the settled solid calcium hydroxide is a reservoir, going into solution untill the maximum soluble value is reached.

[sfsuphysics]

Interesting, was not aware that would happen with calcium hydroxide, I thought it might precipitate out essentially "wasting" what you put in, as I have in the past (without a reactor) noticed clumps of white stuff at the bottom of the container I made my kalkwasser.

Thanks for the reply.

[bertoni]

As carbon dioxide dissolves into the water, the lime will precipitate as calcium carbonate, but that rate might be very slow. At least some reactors have covers to reduce the aeration rate, or at least that's what I've been told.

[shaggss]

There will be solids that remain undissolvable. These include calcium carbonate and magnesium hydroxide from the initial lime. So you cannot gauge whether you need more by the mere presence of undissolved solids.

this is a reply that I got from Randy on the same question.

cheers