The solubility of ammonia (NH3) and ammonium chloride (NH4Cl) in the systems NH3–CH3OH, NH3–C2H6O2, NH4Cl–CH3OH, NH4Cl–C2H6O2, NH3–NH4Cl–CH3OH, NH3–NH4Cl–C2H6O2, and NH3–NH4Cl–C2H6O2 + 8 % CH3OH are reported for temperature conditions relevant to the crystallization of pure magnesium chloride hexammoniate (MgCl2·6NH3) within the Australian Magnesium (AM) process. The solubility of NH3 in anhydrous methanol and ethylene glycol decreased within the temperature range 298 K to 333 K. The solubility of NH4Cl in methanol increased from 3.3 % at 298 K to 3.7 % at 313 K, and in ethylene glycol the NH4Cl solubility increased approximately linearly with temperature between 313 K and 353 K extending from 9.7 % to 11.9 %, respectively. The solubility of NH4Cl in saturated ammoniated methanol at 298 K was 7.9 % with a corresponding NH3 content of 15.0 %. At 313 K it was 5.5 %, while the NH3 content was approximately 9 %. The solubility of NH4Cl in saturated ammoniated ethylene glycol at 313 K, 323 K, and 333 K was 11.0 %, 11.7 %, and 13.2 %, respectively. The results for the systems NH3–NH4Cl in C2H6O2 and CH3OH indicate that minor amounts of NH4Cl, formed during MgCl2·6NH3 crystallization, will dissolve in ammoniated ethylene glycol and ammoniated methanol and ensure an NH4Cl-free hexammoniate product.

This paper uses experimentally determined solid-liquid phase relation studies within the MgCl 2 -H 2 O-C 2 H 4 (OH) 2 ternary system to identify the origin of scale which formed in the packing of the dehydration column of the Australian Magnesium (AM) process for producing anhydrous magnesium chloride. The scale formed during dehydration of a purified magnesium chloride (MgCl 2 ) leach liquor plus recycled ethylene glycol (C 2 H 4 (OH) 2 ) solution. Experiments at 333 K showed the following phase fields present: a liquidonly phase region (Liq T ); three two-phase regions T + Liq T , MgCl 2 · 6H 2 O + LiqR, and MgCl 2 · 3[C 2 H 4 (OH) 2 ] + Liq ; plus two three-phase regions MgCl 2 · 6H 2 O + T + LiqR and MgCl 2 · 3[C 2 H 4 (OH) 2 ] + T + Liq . The compositions LiqR and Liq represent liquid compositions that extend a small distance into the ternary from the invariant points A and B located along the respective MgCl 2 -H 2 O and MgCl 2 -C 2 H 4 (OH) 2 binaries, while T represents a ternary phase of composition MgCl 2 · 2H 2 O · 2[C 2 H 4 (OH) 2 ]. An additional four threephase regions were predicted based on the existence of known crystalline phases. These included: MgCl 2 · 6H 2 O + T + MgCl 2 · 4H 2 O, MgCl 2 · 4H 2 O + T + MgCl 2 · 2H 2 O, MgCl 2 · 2H 2 O + T + MgCl 2 , and MgCl 2 + T + MgCl 2 · 3[C 2 H 4 (OH) 2 ]. The ternary compound was identified as the solid that precipitated within the dehydration column. Additional testwork between (293 and 363) K indicated that the position of the solid-liquid boundary was relatively insensitive to temperature changes.

The ammoniated magnesium chloride hexammoniate compound (HEX) is the key precursor phase required for the production of anhydrous magnesium chloride by the Australian Magnesium (AM) process. It is produced by direct ammoniation of MgCl2-saturated ethylene glycol solutions at 323 K. To determine the conditions required to form HEX, the C2H4[OH]2-rich part of the MgCl2–NH3–C2H4[OH]2 system was investigated at 323 ± 0.5 K. Seven phase regions were determined. These were: NH3(g)+LiqT, HEX+LiqT+NH3(g), HEX+LiqT, HEX+T+LiqT, T+LiqT, MgCl2·3EG+T+LiqT, and LiqT. The symbol T represents a ternary compound of composition MgCl2·2NH3·2C2H4[OH]2, and LiqT represents a ternary liquid phase. To produce only hexammoniate in the AM process, bulk ammonia levels need to be maintained at levels of greater than about (11 to 13) % (w/w) NH3. At lower ammonia levels, the formation of T-phase is promoted, resulting in coprecipitation of HEX and T-phase.

The ammoniated magnesium chloride compounds MgCl2·nNH3, where n is 2, 4, or 6, are potentially usable as materials for producing anhydrous magnesium chloride. The MgCl2−NH3−CH3OH system was investigated at 298 K to determine phase stability regions for hexammoniate (HEX), tetrammoniate (TET), and diammoniate (DI). Five phase regions were determined. These were: HEX+Liq, HEX+T+TLiq, T+TLiq, MgCl2·6CH3OH+T+TLiq, and a ternary liquid phase, TLiq. The phase represented by the symbol T is a previously unknown ternary compound of composition MgCl2·4NH3·2CH3OH, and Liq refers to the liquid phase with a composition along, or very close to, the NH3−CH3OH binary. An additional five phase regions were also predicted based on the existence of known crystalline phases. These were: HEX+Liq(17.45 %NH3/MeOH)+NH3, HEX+TET+T, TET+DI+T, DI+T+MgCl2, and MgCl2·6CH3OH+T+MgCl2. The ternary phase was unstable, breaking down to produce ammonium chloride, ammonia, and magnesium methoxide (Mg(CH3O)2). These were all partially soluble in the methanol-rich ternary liquid. The MgCl2−NH3−CH3OH system could potentially be used to produce magnesium chloride hexammoniate as feedstock for anhydrous magnesium chloride production, providing the ammonia concentration remains high enough to suppress formation of the ternary compound.

A twenty-tray single bubble-cap column was used to air strip ammonia and methanol from a synthetic, as well as a plant wastewater stream. When feeding synthetic solutions containing $700 mg/kg ammonia, stripping efficiencies of more than 98% were achieved at gas to liquid mass ratios (G/L) ratios of 2.5-2.7. This produced stripper bottom solutions contains $10 mg/kg ammonia. Reducing the air flow by 25% increased the ammonia content in the stripper bottoms to $30 mg/kg.Using the graphical McCabe-Theile method, the overall column efficiency for the bubble cap column during ammonia stripping was between 9 and 26% because of the low contact efficiency of this column.When treating the ''as received'' plant wastewater, the ammonia removal efficiency was only 84% at the lower G/L ratio. This increased to 99% by raising the pH from 9.8 to 11.5 and increasing the G/L mass ratio.The ammonia volumetric mass transfer coefficient (K L a) for these tests was calculated to be between 0.38 and 0.58 h 21 . Both stripping and absorption of methanol occurred in the column during stripping of ammonia. Based upon solution analyses, the methanol removal efficiency varied between 55 and 95%.