 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 K2CO3 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 K2O, % Chlorides: Mines (Canada, USA, Russia) - 96% Sylvinite KCl · NaCl mixture 28 Sylvite KCl 63

Carnalite KCl · MgCl2 · H2O 17 Evaporating ponds (USA, Jordan, Israel) - 3% Kainite 4KCl · 4MgSO4 · 11H2O 19

Hanksite KCl · 9Na2SO4 · 2Na2CO3 3 Sulphates:

Polyhalite K2SO4 · 2MgSO4 · 2CaSO4 · 2H2O 16

Langeinite K2SO4 · 2MgSO4 23

Leonite K2SO4 · MgSO4 · 4H2O 26

Schoenite K2SO4 · MgSO4 · 6H2O 23

Krugite K2SO4 · MgSO4 · 4CaSO4 · 2H2O 11

Glaserite 3K2SO4 · Na2SO4 43

Syngenite K2SO4 · CaSO4 · H2O 29

Aphthitalite (K,Na)2SO4· 30

Kalinite KAl(SO4)2 · 11H2O 10

Alunite K2Al6(OH)12 · (SO4)4 11 NEW Nitrates:

Niter KNO3 47 Potash deposits composition

Seawater KCl·NaCl

K2SO4·2MgSO4

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 - MgCl2 - H2O METSIM(PFD KCl centrifuges) METSIM solubility equilibrium METSIM – Equilibrium functions KC l- NaCl - H2O

OLI

NaCls NaCl – KCl invariant

KCls KC l- NaCl - H2O

OLI data 0C 35 25C

30 50C

NaCl 75C 25 100C 20 150C

15 NaCl + KCl

NaCl, weight % weight NaCl, 10

KCl 5

0 0 5 10 15 20 25 30 35 40 KCl, weight % KC l- NaCl -H2O 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

ΔC (KCl) Solution mine with evaporaton

KCl

NaCl

ΔCevp (KCl) ΔC (NaCl)

ΔC (KCl) Saskatchewan solution mine

KCl

NaCl

ΔCevp (KCl) ΔC (NaCl)

ΔC (KCl)

ΔCfr (KCl) KC l- NaCl - MgCl2 - H2O

0 g/ L MgCl2

NaCl + KCl

20 g/ L MgCl2

100 g/ L MgCl2 KC l- NaCl - CaSO4 - H2O pH of vapor condensate

Vapor: HCl-H2O No problems?

1 OLI predicts proper pH for the vapor condensate from evaporators but not for dryers.

MgCl2·2H2O = MgOHCl + HCl + H2O 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-SO4-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