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OLI 24 th Users Conference October 24,2007

OLI 24 th Users Conference October 24,2007. Applying Electrolyte Theory To Real World Problems Noel C. Scrivner DuPont Fellow (Retired) Adjunct Professor ChE Rowan University (Active). Topics. Fluoride removal Cr+3 removal Graphical techniques for understanding.

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OLI 24 th Users Conference October 24,2007

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

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

  3. Waste Treatment Plantfor 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 OLI 24th Users NC Scrivner

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  6. 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 ? OLI 24th Users NC Scrivner

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

  8. 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 OLI 24th Users NC Scrivner

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

  11. 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 OLI 24th Users NC Scrivner

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

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

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

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  16. Metal Hydroxide Solubility Data • Literature values vary • Experimental method • Complexing agents • Particle size • Age OLI 24th Users NC Scrivner

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  19. Results from other programs • Cr+3 system • Cu+2 system • Zn+2 system OLI 24th Users NC Scrivner

  20. XXXXX xxxxx OLI 24th Users NC Scrivner

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  23. 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 OLI 24th Users NC Scrivner

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

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  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 OLI 24th Users NC Scrivner

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  29. 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 OLI 24th Users NC Scrivner

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  33. CO3= CO2 HCO3- OH- H+ OLI 24th Users NC Scrivner

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  35. Conclusions • Consider the Chemistry • Check other data sources • Uncertainty Analysis • Purpose is insight not pages of output • Experiments to Confirm OLI 24th Users NC Scrivner

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