1. OLI 24th Users Conference October 24,2007
Applying Electrolyte Theory
To Real World Problems
Noel C. Scrivner
DuPont Fellow (Retired)
Adjunct Professor ChE
Rowan University (Active)
10/24/07
OLI 24th Users NC Scrivner

2. OLI 24th Users NC Scrivner
Topics
Fluoride removal
Cr+3 removal
Graphical techniques for understanding
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OLI 24th Users NC Scrivner

3. Waste Treatment Plant for Acidic Fluoride Stream
Environmental requirements
pH 6 to 9 range
”Total” fluoride (dissolved & suspended) low teens
Feed stream
pH 2 to 3
Fluoride 1,000 ppm
Lime slurry at site for neutralization
ESP simulation shows 8 ppm Fluoride over 6 to 9 pH range
Small scale pilot of system for other reasons
10/24/07
OLI 24th Users NC Scrivner

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6. OLI 24th Users NC Scrivner
Pilot Plant Results
Smooth operation
Controlled pH 8 to 9 range
Fluoride < 10 ppm
Met other requirements
Towards end of scheduled operation Fluoride increases to 20 ppm
Ran low on lime, went to Newark Farm & Home for 40 lb bag of Dolomitic lime
What could be happening ?
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OLI 24th Users NC Scrivner

7. Critical Stability Constants CaF+ & MgF+ Complexes and CaF2 & MgF2 ppt
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OLI 24th Users NC Scrivner

8. OLI 24th Users NC Scrivner
ESP Model changes
Added Mg(OH)2 to chemistry generation file
Dolomitic Lime 10% Mg(OH)2 & 90% Ca(OH)2
New simulation
Predicted total fluoride about 20 ppm in 6 to 9 pH range
10/24/07
OLI 24th Users NC Scrivner

9. OLI 24th Users NC Scrivner
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10. OLI 24th Users NC Scrivner
MgF2 ppt does not form
Add more dolomitic line for CaF2 ppt formation
Too high pH from Mg(OH)2
Stoichiometric Ca
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OLI 24th Users NC Scrivner

11. OLI 24th Users NC Scrivner
Learnings
Don’t use Dolomitic Line at the plant
Need full and correct list of feed chemicals
Go to the literature for leads on additional chemistry to include in the ESP model
Need a complete and correct database
Need both ESP simulation and experiments
Chemistry is still an experimental science
10/24/07
OLI 24th Users NC Scrivner

12. OLI 24th Users NC Scrivner
Chromium Problem
Wastewater from CrO2 process
Chromium concentration > 50 ppm
Soluble Cr(VI) as CrO4 = anion
Reduce total Chromium to < 1ppm
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OLI 24th Users NC Scrivner

13. OLI 24th Users NC Scrivner
Process
Reduce Cr+6 to Cr+3
Reducing agent HSO3-
Reduction kinetics fast at low pH
Form Cr(OH)3 precipitate at high pH
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OLI 24th Users NC Scrivner

14. Reactions & Soluble Chromium Species
Cr(OH)3 PPT = Cr OH-
Cr+3 + OH- = Cr(OH)+2
Cr(OH)+2 + OH- = Cr(OH)2+
Cr(OH)2+ + OH- = Cr(OH)3 AQ
Cr(OH)3 AQ + OH- = Cr(OH)4-
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OLI 24th Users NC Scrivner

15. OLI 24th Users NC Scrivner
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16. Metal Hydroxide Solubility Data
Literature values vary
Experimental method
Complexing agents
Particle size
Age
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19. Results from other programs
Cr+3 system
Cu+2 system
Zn+2 system
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20. OLI 24th Users NC Scrivner
XXXXX
xxxxx
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xxxxx
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XXXXX
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23. OLI 24th Users NC Scrivner
Conclusions
Use theory to suggest which species could be important
If these are not in the database, could be problems
Check other sources for data & do a hand calculation
Include all possible feed compounds in the chemistry model
Use the model to suggest critical experiments
10/24/07
OLI 24th Users NC Scrivner

24. What else have I learned ?
Garbage In => Garbage Out
The purpose of computing is insight not numbers
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OLI 24th Users NC Scrivner

25. OLI 24th Users NC Scrivner
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OLI 24th Users NC Scrivner

26. What else have I learned ?
Garbage In => Garbage Out
The purpose of computing is insight not numbers
Show the big picture to clients & peers (and yourself)
“Flood” plots
“Sillen” plots
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OLI 24th Users NC Scrivner

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29. OLI 24th Users NC Scrivner
Flood Plot for Diprotic System
pH from adding only CO2 or NaHCO3 or Na2CO3
Most “Flood” lines not shown
pKa1=6.35
pKa2=10.33
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33. OLI 24th Users NC Scrivner
CO2
HCO3-
CO3=
OH- H+
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35. OLI 24th Users NC Scrivner
Conclusions
Consider the Chemistry
Check other data sources
Uncertainty Analysis
Purpose is insight not pages of output
Experiments to Confirm
10/24/07
OLI 24th Users NC Scrivner