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The factory I work at has a large flume system that contains sugar and organics. CaO is added to the flume to maintain a 12pH and keep bacterial activity to a minimum. In order to reduce the use of CaO I need to roughly calculate losses due to different mechanisms.

Currently the two main unknown losses are:

  1. Bacteria forming organic acids that neutralize the Ca(OH)2. This is a very big factor if pH is permitted to drop. It may also be a factor in flume side streams even when a high pH is maintained, but it is complex and I will put it in the "unknown loss category" for now.
  2. Atmospheric carbon dioxide entering solution and bonding with the Ca(OH)2 to form CaCO3. The flume has roughly 4000m^2 of surface area. There are also some areas of agitation and air entrapment that would take some more analysis to parameterize. This is the one I'm hoping to be able to calculate.

So here are my questions:

How do I calculate the rate Ca(OH)2 is being neutralized? (I know moles, units, and general chemistry, but now sure how to calculate reaction rates from partial pressures on this scale and geometry)

Is the amount of Ca(OH)2 being neutralized, proportional(linear, log, or otherwise) to pH? (Not sure if this is a 100% surface area relationship or if it depends on the amount of Ca(OH)2 in the water)

Thanks!

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  • $\begingroup$ @Mithoron, I have made that correction, thanks. I work in an industry where they call it "milk of lime" so give me some slack ;-). I'm a mechanical engineer and can figure it out; I'm just looking for some direction. $\endgroup$ – ericnutsch Oct 15 '18 at 20:56
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    $\begingroup$ Hmm, looks like most of this stuff should be done experimentally - why don't you have pH data already? $\endgroup$ – Mithoron Oct 15 '18 at 21:07
  • $\begingroup$ The flume is currently in use. We add CaO as necessary to maintain a 12pH. I remember some about partial pressures, but not how they relate to reaction rates. I realize experimental numbers would be better, just hoping to find some rough calculations to make sure Im in the right ballpark. $\endgroup$ – ericnutsch Oct 15 '18 at 22:01
  • $\begingroup$ Well, you are measuring pH to adjust, don't you? That's the data needed. To get full data experiments outside of normal regime would be also needed. $\endgroup$ – Mithoron Oct 16 '18 at 0:27
  • $\begingroup$ We do record how many tons of CaO we add, but the microbial aspect can be quite large as well so I was hoping to be able to distinguish between the two with calculation. I will look back at running some experiments but I will leave the question up to see if anybody has any other ideas. Thanks $\endgroup$ – ericnutsch Oct 16 '18 at 0:41

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