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AU-BCE-EE / tric-fil-mod

A trickling filter model to simulate air treatment, written in Python
GNU General Public License v3.0
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Consider ionization in tfmod (Daw not Kaw) #6

Open sashahafner opened 1 year ago

sashahafner commented 1 year ago

So model will need pH and Ka as inputs as in Kga_onda.

sashahafner commented 1 year ago

Added in fed7a4a9fca8486f01afd39d97b8f682f0681824

sashahafner commented 1 year ago

Note that I used 

    alpha = 1 / (1 + 10**(pKa - pH))

Not ...pH - pKa from the Onda function.

sashahafner commented 1 year ago

I also corrected the Onda function in 8d3dca59067feddee2d82742737613e5c7a04b50

sashahafner commented 1 year ago

Oops, I see alpha was "alpha0", fraction in free (uncharged, volatile) form. So Onda function was originally correct. Switched function and corrected model in c9da34167eaf57f7d73557c830c1e0a8abb552cd and 23461909d74b18241fd99563f7f2c9157c560986

sashahafner commented 1 year ago

I've renamed alpha alpha0 for clarity (I think this is what Snoeyink and Jenkins use in Water Chemistry).

sashahafner commented 1 year ago

We need to consider whether reaction should apply equally to both species. Presently it does.

sashahafner commented 1 year ago

I'm leaving this open for now because we might want to consider different reaction rates for the two species (charged and uncharged) in the future. But the ionization should be functional.

sashahafner commented 11 months ago

I think we should allow for a missing pKa value in the inputs, where the volatile concentration is total concentration.

sashahafner commented 11 months ago

For example a gas that doesn't react.

sashahafner commented 5 months ago

@AnneMortensen I am moving this discussion from #21 here.

2. I will erase L237, I had a feeling I had misunderstood something (and I probably need to brush up on the definitions of Daw and Kaw anyways).

Actually it would be good to define these variables in the model script or better, to create a proper help file.

Both Daw and Kaw are distribution coefficients. Kaw is the more "thermodynamic" one, based on the dissolved species that is actually in equilibrium with gas/vapor phase species. Daw includes all dissolved species. So for H2S, Kaw = conc. H2S in gas phase / conc. dissolved H2S, Daw = conc. H2S in gas phase / (conc. H2S + conc.

You can find more details on the difference searching for partition versus distribution coefficient. What we called Kaw is called a partition coefficient in places (like this good Wikipedia summary: https://en.wikipedia.org/wiki/Partition_coefficient). Note that the term "partition coefficient" is often used for the same thing. But technically that is based on chemical activity and not concentrations. In this model and many places we probably assume activities = concentrations, assuming we use values for Henry's law constant. So it is largely a matter of language.