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Thermodynamic and kinetic studies of the MgCl 2 ‐NH 4 Cl‐NH 3 ‐H 2 O system for the production of high purity MgO from calcined low‐grade magnesite
Author(s) -
Wang Junfeng,
Li Zhibao,
Park AhHyung Alissa,
Petit Camille
Publication year - 2015
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.14789
Subject(s) - magnesite , calcination , chemistry , magnesium , leaching (pedology) , inorganic chemistry , analytical chemistry (journal) , nuclear chemistry , mineralogy , chromatography , catalysis , organic chemistry , biochemistry , environmental science , soil science , soil water
To improve the overall sustainability of MgO‐based refractory production, a novel process to produce high purity MgO from calcined low‐grade magnesite in ammonium chloride solution was developed. The process was designed on the basis of the phase equilibria of the NH 4 Cl‐MgCl 2 ‐NH 3 ‐H 2 O system obtained using the Mixed Solvent Electrolyte model embedded in OLI software. The optimum calcination temperature of low‐grade magnesite was determined to be 650°C in terms of the conversion ratio of magnesium and calcium in the leaching experiments. An apparent activation energy of Mg extraction was 30.98 kJ/mol, which is slightly lower than that of Ca leaching. An empirical kinetic model of magnesium extraction was also developed to describe the effects of NH 4 Cl concentration, particle size of calcined magnesite, and solid‐to‐liquid ratio on the extent of extraction of magnesium. At leaching time of 10 min, the leachate with high Mg/Ca molar ratio was obtained. Then, MgO with a purity of 99.09% was produced through the decomposition of intermediate 4MgCO 3 ·Mg(OH) 2 ·4H 2 O. © 2015 American Institute of Chemical Engineers AIChE J , 61: 1933–1946, 2015