add 36% HCL to wastestream

[Jason R]

In the field I had a 100 mL sample of fluid that I had 36% HCL to until the pH dropped from 11.5 to 7. the amount I added was .3186 grams of 36% hcl to 100 mL of the waste stream. when I run this in the program, I get .25 grams of 36% hcl added to 100 mL of the waste stream to bring the pH from 11.5 to 7. Can someone please look to determine if I am doing something wrong? I have also attached the initial water analysis.

GSS Chemwaste 36% HCL.rea Water Analysis for Geochem workbench.xlsx

[Jia Wang]

Hello Jason,

I took a quick look at your input files and noticed a couple of issues with the set up. In the Reactant pane, you have set up reaction pathway for HCl to be titrated into your system. As it is, React titrates in HCl until the it reaches 36 wt% of your fluid and not titrating an acid of 36 wt% of HCl. You would need to create the 36 wt% acid you want to use before setting it as a reactant. To do so, set up the basis pane with 1 kg of H2O and enter H+ and Cl- as a basis species and enter the concentration corresponding to the acid. Select Run -> Go and have React speciate this fluid. You can up the pickup feature and use the resulting fluid composition as your reactant (Run -> Pick up -> Reactant -> Fluid). Throughout the simulation, your reactant is titrated linearly into your fluid. You can scale down the amount of reactant titrated into your system in the reactant times box (e.g. 0.01). 

After picking up the results, return to the basis pane and enter the basis species and concentrations for the basis species as given by the geochemical fluid analysis. I noticed that you are using the alkalinity measurement directly as the component concentration for the carbonate species. In React, alkalinity units accepted are in terms of CaCO3 or in equivalents of acids (Chapter 6.1 Units in the GWB Command User Guide). You would want to convert your alkalinity units from your geochemical analyses to either one of the accepted units above. To convert to units of meq_acid/l, you would divide the alkalinity reported as mg/l as HCO3- by the molar mass of HCO3-.

My apologies for the late response. This part of the forum was set up as an archive for older posts, so I don't receive notifications when people add new topics there. If you post to the font page, though, notifications to the GWB staff will be sent out. 

Hope this helps,

Jia Wang

[Jason R]

36% HCL + Chemwaste V1 23JUNE2020.reaReact_output_36% HCL + Chemwaste 23JUNE2020.txt36% HCL only V1 23JUNE2020.reaReact_output_36% HCL Only V1 23JUNE2020.txt

 

Jia,

Water Analysis for Geochem workbench.xlsx

I have attached the files, but I think an explanation on what I am trying to do might be relevant to make sure I am on the right track.

In the field, I took 100 mL of the sample in the attached water analysis and added .269 mL or .3186 Grams of 36% HCL to reduce the pH from 11.5 to 7.038 the specific gravity of 36% HCL is 1.18. What I am trying to do is as follows:

 

1) replicate this in the simulator. when I do a pH vs volume of 36% hcl graph, it should show me a pH of 7 when I add .269 mL or .3186 Grams of 36% HCL

2) if I show a pH range from 0 to 14, it would accurately simulate the amount of 36% HCL that would need to be added in order to achieve that pH

 

Let me know how the file looks and what I need to do in order to get the desired results. I really appreciate your time helping me with this

 

[Jia Wang]

Hello Jason,

I took a quick look at your input files and here are a few suggestions. For alkalinity concentration, you should use meq_acid/l for the unit and not meq/l for HCO3-. This will change your calculation by quite a bit. I also noticed in the basis pane that 1 free kg of H2O is designated but your problem describes a 100 ml sample with a density of 1.01 g/cm3. I would suggest setting the amount of free solvent at 0.1 kg so your calculation is performed at or very close to your sample volume. Another suggestion is to change the value of "reactant times" in the Reactants pane to something like 0.0001. It looks like you created a 10 kg solution of your 36% HCl acid. You won't need to titrate all of it if you are only expecting to see the change you want with a small amount added. Reactants times factors the total amount of your reactant that you are adding to your fluid. You can also turn off precipitation in your React simulation by going to Config --> Option and uncheck precipitation. Unless you are expecting minerals to precipitate during your titration, it might be worth considering turning it off so that mineral precipitation is not a factor in your calculation. I think with these changes, you will get much closer to the field measured volume and mass of HCl added. You can view your result in Gtplot by choosing your x-axis variable as "mass reacted total" under the variable type "Reactant properties" and your y-axis variable as the pH under the variable type "Chemical parameters".  For more information on plot configuration, please see section 6.2 XY Plot configuration in the Reaction Modeling User guide.

Hope this helps,
Jia Wang