THE FACT FTfrtz FERTILIZER DATABASES

 

The FTfrtz databases contain thermodynamic models evaluated/optimized by the FACT group as part of a project for the production of nitrate based fertilizers, from hydrous to anhydrous conditions).  It can also be used for calculating the thermodynamic properties and phase equilibria in the fertilizer products, and for some explosives.  The FTfrtz solution database (FTfrtz63Soln.sda) contains salt solutions.  The FTfrtz compound database (FTfrtz63Base.cdb) contains all stoichiometric solid and liquid salt compounds evaluated/optimized by the FACT group (see “collaborators”) to be thermodynamically consistent with the FTfrtz solution database. 

NH4NO3_KNO3_diag.emf 

 

                  Systems and Components

 

The FTfrtz databases contain data for pure salts and salt solutions based on the family of ammonium nitrate (AN, NH4NO3), mono-ammonium di-hydrogen phosphate (MAP, NH4H2PO4), ammonium chloride (AC, NH4Cl) and ammonium sulfate (AS, (NH4)2SO4) fertilizers with additions of their corresponding potassium salts (and in some cases sodium salts).  The model covers the addition of roughly up to 50% weight of water (H2O).  The liquid model for ammonium di-hydrogen phosphate (MAP, NH4H2PO4) also includes the dimerization reaction to form (NH4)2H2P2O7:

 

2 NH4H2PO4(liq.) « (NH4)2H2P2O7(liq.) + H2O(liq. or gas)

 

Binary, ternary and reciprocal anhydrous salt sub-systems have been evaluated and optimized, over all range of composition and for temperatures above -25oC.  The binary H2O-salt sub-systems were evaluated to the highest levels of H2O possible with the liquid model (which is the Modified Quasichemical Model in the Pair Approximation for Salt Solutions, using hydrated cations and anions).  Typically this means that the liquid solution covers the complete anhydrous range, but it limited to roughly 50% weight of water. 

 

The FTfrtz databases also contain data for the Ca(NO3)2-KNO3-H2O system, at all composition.  The properties at very high water contents are approximated.

 

FOR ALL THE ABOVE HYDROUS SYSTEMS, THE pH IS ASSUMED NEUTRAL (i.e. no H+ or OH- is taken into account).

 

ALSO, FOR CALCULATIONS INVOLVING AMMONIUM NITRATE (“AN”, NH4NO3), IT IS RECOMMENDED NOT TO SELECT N-CONTAINING GASEOUS SPECIES (AS N2(g), NO2(g), etc..) EXCEPT NH3(g) and HONO2(g), AS NH4NO3 IS A METASTABLE COMPOUND RELATIVE TO H2O, N2 and O2 (i.e. IT IS AN EXPLOSIVE!):

 

N2(g) + 2 H2O(liq.) + O2(g) ® NH4NO3(s)            DHo298.15K = 206 kJ/mol

 

In the EQUILIB or PHASE DIAGRAM Modules, metastable equilibria involving solid or liquid ammonium nitrate or one of its solutions can be calculated by removing all gaseous species which contain a N-N bond (as N2, N3, N2O, HNNH, N2H4, etc..) and some species involving N-O bonds where a free electron pair is present, like N(g), NO(g), NO2(g), NO3(g), N2O3(g), N2O4(g), N2O5(g), NH(g), NH2(g), HNO(g), HONO(g1) and HONO(g2).  This is equivalent to allowing ammonium nitrate to dissociate only to ammonia and to HONO2(g) according to NH4NO3(s or liq.) « NH3(g) + HONO2(g).

 

Permitted lists (groupings) of salts which have been optimized and for which accurate calculations can be expected within the above mentioned composition limits: 

(1) AN-AC with potassium and sodium (anhydrous and hydrous):  NH4+, K+, Na+ // NO3-, Cl-  +  H2O

All anhydrous binary and ternary subsystems have been fully optimized and evaluated together at all compositions.  Systems with water valid up to 50% weight of H2O (all binary and available ternary systems with H2O have been optimized above 25oC).

(2) AN-AC-MAP with potassium (anhydrous and hydrous, and also contains (NH4)2H2P2O7):  NH4+, K+ // NO3-, Cl-, H2PO4-, H2P2O72-  +  H2O

All anhydrous binary and ternary subsystems have been fully optimized and evaluated together at all compositions.  Systems with water valid up to 50% weight of H2O (all binary and available ternary systems with H2O have been optimized above 25oC).

(3) AN-AS with potassium (anhydrous and hydrous):  NH4+, K+ // NO3-, SO42-, Cl-  +  H2O

All anhydrous binary and ternary subsystems have been fully optimized and evaluated together at all compositions.  Systems with water valid up to 50% weight of H2O (all binary and available ternary systems with H2O have been optimized above 25oC).  However, the binary system H2O-K2SO4 is approximated.

(4) The Ca(NO3)2-KNO3-H2O system: Ca2+, K+ // NO3-  +  H2O

Optimized at all compositions, but less valid for the ice liquidus.

 

 

 

 

                                         Phases

 

For complete descriptions of all solution phases, click on “Description of solutions” in this menu.

 

 

                                          Liquid Solutions

 

The liquid phase contains all the components in the FTfrtz database.  The modified quasichemical model in the pair approximation is used, with hydrated cations and anions (and with neutral water on both cationic and anionic sublattices).  This model accounts for the very strong cation-anion short-range-ordering present in these solutions, but not for cation-cation short-range-order (although excess Gibbs energy terms are present).

 

The database contains 2 liquid solutions: LqFz and LQCaLQCa is for the Ca(NO3)2-KNO3-H2O system.  LqFz is for the other systems (AN, AS, AC, MAP + sodium and potassium salts).  Both solutions are for hydrous and anhydrous molten salts.  DO NOT USE SIMULTANEOUSLY LqFz and LQCa.

  

 

 

                                             Solid Solutions

 

Models have been developed and applied for the multicomponent solid solutions between the salts, especially between ammonium and potassium salts (N1, N2, N3, N4, N5, K1, K2, K3, ...).  These models take into account the mixing of various cations on crystallographically different sublattices, and are mostly based on the modified quasichemical model in the pair approximation to take into account the cation-anion short-range-order which is more important at the low temperature at which these solutions are stable. 

 

K1 “RHO” (distorted rhombohedral)

Based on the high-temperature KNO3 solid phase.  It is divided in 2 lists of components that are allowed to mix:

-         K+, NH4+, Na+ // NO3-

-         K+, NH4+ // NO3-, H2PO4-

 

K2 “Pmcn”

Based on the low-temperature KNO3 solid phase.  It is divided in 2 lists of components that are allowed to mix:

-         K+, NH4+, Na+ // NO3-, Cl-

-         K+, NH4+ // NO3-, H2PO4-, Cl-

 

K3 “R3m”

This is a binary KNO3-NH4NO3 solid solution.

 

N1 “Pm3m” (cubic CsCl protptype)

This solution is based on the high-temperature NH4NO3 solid phase and the low-temperature NH4Cl solid phase.  It is divided in 2 lists of components that are allowed to mix:

-         NH4+, K+, Na+ // Cl-, NO3-

-         NH4+, K+ // Cl-, NO3-, H2PO4-, SO42-

 

N2 “P4bm” (tetragonal)

This solution is based on a stable high-temperature NH4NO3 solid phase, with the following list of components that are allowed to mix:

-         NH4+, K+ // Cl-, NO3-, H2PO4-, SO42-

 

N3 “Pbnm” (orthorhombic)

This solution is based on NH4NO3, with the following list of components that are allowed to mix:

-         NH4+, K+ // Cl-, NO3-, H2PO4-, SO42-

 

N4 “Pmmn” (orthorhombic)

This solution is based on the room temperature NH4NO3, with the following list of components that are allowed to mix:

-         NH4+, K+ // Cl-, NO3-, H2PO4-

 

N5 “P4.2” (tetragonal)

This solution is based on the low-temperature NH4NO3, with the following list of components that are allowed to mix:

-         NH4+, K+ // Cl-, NO3-, H2PO4-

 

Fm3m (cubic NaCl protptype)

This solution is based on the NaCl Rocksalt structure, with NaCl-KCl-NH4Cl as components.

 

P1 “I42d”

This solution is the (K,NH4)H2PO4 solid solution (immiscibility gap below 30oC), with the following list of components that are allowed to mix:

-         NH4+, K+ // H2PO4-

 

NKSl “NKS-l” (orthorhombic)

This solution is the low-temperature (NH4)2SO4 solid solution, with the following list of components that are allowed to mix:

-         NH4+, K+ // SO42-

 

NKSh “NKS-h” (distorted orthorhombic)

This solution is the high-temperature (NH4)2SO4 solid solution, with the following list of components that are allowed to mix:

-         NH4+, K+ // SO42-

 

Beta (P63/mmc)

This solution is the high-temperature K2SO4 solid solution, with the following list of components that are allowed to mix:

-         NH4+, K+ // SO42-

 

NS21 “B”

This solution is the based on the (NH4)4(NO3)2SO4 compound (AN2AS1), with the following list of components that are allowed to mix:

-         NH4+, K+ // NO3- // SO42-

 

NS31 “A”

This solution is the based on the (NH4)5(NO3)3SO4 compound (AN3AS1), with the following list of components that are allowed to mix:

-         NH4+, K+ // NO3- // SO42-

 

                               Stoichiometric Solid Salts

Evaluated and optimized properties of 26 stoichiometric salts are found in the FTfrtz compound database.  For a list, see “List of compounds and solutions.”

 

                                Collaborators

This database was developed as part of a series of projects with an international fertilizer producer company.  The projects were under the direction of Prof. Patrice Chartrand and Prof. Arthur. D. Pelton (CRCT, Ecole Polytechnique) and with the help of Dr. Christian Robelin, Dr. Micheal Wadsley, Dr. Frederic Gemme and Dr. James Sangster (CRCT).