Saturated aqueous solutions in Potash industry. Modeling of properties and composition Sergei Panasiuk, Ph.D. Chief mineral process specialist WorleyParsons Canada, Minerals & Metals
Potash – any potassium compound (KCl – most common). Potash = “pot ashes” old method of making K 2 CO 3 by leaching of wood ashes, evaporating the resulting solution in iron pots. The first U.S patent issued in 1790 and sighed by G. Washington. “in the making of Pot ash … by new Apparatus and Process”.
Samuel Hopkins “…making of Pot ash and Pearl ash by a new Apparatus and Process” In 1791, Government of Lower Canada (Quebec) issued “letter of reward” to Hopkins for his improved method. Regarded as the first “patent” issued in Canada.
Potassium minerals Mineral Composition K 2 O, % Mines (Canada, USA, Russia) - 96% Chlorides: Sylvinite KCl · NaCl mixture 28 Sylvite KCl 63 Carnalite KCl · MgCl 2 · H 2 O 17 Evaporating ponds (USA, Jordan, Israel) - 3% Kainite 4KCl · 4MgSO 4 · 11H 2 O 19 Hanksite KCl · 9Na 2 SO 4 · 2Na 2 CO 3 3 Sulphates: Polyhalite K 2 SO 4 · 2MgSO 4 · 2CaSO 4 · 2H 2 O 16 Langeinite K 2 SO 4 · 2MgSO 4 23 Leonite K 2 SO 4 · MgSO 4 · 4H 2 O 26 Schoenite K 2 SO 4 · MgSO 4 · 6H 2 O 23 Krugite K 2 SO 4 · MgSO 4 · 4CaSO 4 · 2H 2 O 11 Glaserite 3K 2 SO 4 · Na 2 SO 4 43 Syngenite K 2 SO 4 · CaSO 4 · H 2 O 29 Aphthitalite (K,Na) 2 SO 4 · 30 Kalinite KAl(SO 4 ) 2 · 11H 2 O 10 NEW Alunite K 2 Al 6 (OH) 12 · (SO 4 ) 4 11 Nitrates: Niter KNO 3 47
Potash deposits composition Seawater KCl·NaCl K 2 SO 4 ·2MgSO 4 Dead Sea
KCl-NaCl mining 1000m deep
Surface mining Dead Sea
Block Flow Diagram – Potash Solution Mine Solubility: Density: - Flotation (salts and amines) - U/G solution mining - U/G solution mining - Evaporation/crystallization - Brine evaporation - Brine U/G injection - KCl crystallization - Brine U/G injection Boiling point elevation: - Evaporation/crystallization - Dryers Vapor pressure and composition: - Evaporation/crystallization - Exhaust gas scrubbers - Dryers
KC l- NaCl - MgCl 2 - H 2 O
METSIM(PFD KCl centrifuges)
METSIM solubility equilibrium
METSIM – Equilibrium functions
KC l- NaCl - H 2 O OLI NaCl s NaCl – KCl invariant KCl s
KC l- NaCl - H 2 O OLI data 0C 35 25C 30 50C NaCl 75C 25 100C NaCl, weight % 20 150C NaCl + KCl 15 10 KCl 5 0 0 5 10 15 20 25 30 35 40 KCl, weight %
KC l- NaCl -H 2 O invariant solubility NaCl KCl
Solution mine 65 °C 55 °C NaCl saturated NaCl saturated KCl depleted KCl saturated NaCl 1500 m depth KCl -NaCl NaCl
Solution mine KCl NaCl Δ C (KCl)
Solution mine with evaporaton KCl NaCl Δ C evp (KCl) Δ C ( NaCl) Δ C (KCl)
Saskatchewan solution mine KCl NaCl Δ C evp (KCl) Δ C ( NaCl) Δ C (KCl) Δ C fr (KCl)
KC l- NaCl - MgCl 2 - H 2 O 0 g/ L MgCl 2 NaCl + KCl 20 g/ L MgCl 2 100 g/ L MgCl 2
KC l- NaCl - CaSO 4 - H 2 O
pH of vapor condensate Vapor: HCl-H2O
No problems? 1 OLI predicts proper pH for the vapor condensate from evaporators but not for dryers. MgCl 2 ·2H 2 O = MgOHCl + HCl + H 2 O t > 135 °C
Problem 2 65 °C 55 °C NaCl saturated NaCl saturated KCl depleted KCl saturated NaCl 1500 m depth KCl -NaCl NaCl
Oversaturation Reality - >10% undersaturation for KCl
Problem 3. Complexity
Process Flow Diagrams (Dryers)
Dynamic process simulation
Conclusions: • Potash industry requires accurate prediction of solubility in system K-Na-Mg-Cl-SO 4 -H2O system • Predictions of the brine density, boiling point elevation, viscosity, vapor pressure and compositions are also very important • METSIM uses polynomial functions to approximate some of the brine parameters • OLI is capable to predict all required brine properties in the wide range of conditions • OLI and METSIM predictions of the brine properties are very similar in the narrow range of the most common potash industry applications. • Computer simulation of the large industrial projects requires to use some simplifications of OLI approach
Recommend
More recommend
