STUDY OF THERMAL DECOMPOSITION
OF NATURAL AND SYNTHETIC MAGNESIUM COMPOUNDS
I. D. Kashcheev,
K. G. Zemlyanoi,
V. M. Ust’yantsev,
and E. A. Voskretsova
Translated from Novye Ogneupory, No. 10, pp. 28 – 35, October 2015.
Original article submitted May 21, 2015.
Processes are considered for thermal decomposition of natural (magnesite, brucite) and synthetic (hydro
magnesite, hydroxide) magnesium compounds. Thermophysical properties are established for calcination, ef
fect of heating rate, and temperature on phase composition and amount of heat required for calcination. Coef
ficients determined are the activation energy and pre-exponential factor in an Arrhenius kinetic equation for
decomposition of test minerals. It is established that a more convenient form of magnesium-containing prod
uct, obtained as a result of chemical enrichment, is hydromagnesite.
Keywords: magnesium oxide, calcination, kinetics, crystallite size, Arrhenius equation, activation energy.
One of the main development trends in contemporary re-
fractory materials is improvement of quality, including as a
result of using cleaner starting (raw) material [1, 2]. This en-
tirely concerns one of the main refractory materials for met-
allurgical production, i.e., magnesium oxide.
As an element magnesium occupies eighth place with re-
spect to content in the earth’s lithosphere (~2 wt.%), and
third place with respect to mineral content in sea water. This
concentration is about 1300 ppm. The magnesium element
consists of three stable isotopes
Mg (11.3%) with an average atomic weight of
24.31. More than sixty minerals containing magnesium are
known. The most important ore-forming minerals containing
magnesium are chlorites, pyroxenes, and amphiboles, dolo
mite, and dolomatized limestone. It is also present in
and hydrated carbonates such as
O and lansfordite MgCO
and also in brucite Mg(OH)
. A number of basic magne
sium carbonates exist with an empirical formula
O, which concern in particular
O and artinite
O. Magnesium is also encountered in
salt deposits such as carnallite KMgCl
O, and kieserite MgSO
The main sources for preparing magnesium oxide in in
dustry are magnesite, brucite, and sea water; aqueous solu
tions and deposits of water soluble magnesium-containing
salts are used mainly as raw material for preparing magne-
sium metal and chemically pure salts.
The main magnesite and brucite reserves containing not
less than 90 wt.% MgO (for calcined substance) within the
world are estimated as 8.5 billion tons, including known re-
serves of 3.6 billion tons . Leading mining countries are
China, Russia, North Korea, and Turkey, and the proportion
of the undisputed leader, i.e., China, is about 65% of world
Very valuable types of raw material for preparing magne
sia products are sea water and brine, and these sources oc
cupy a significant place in the structure of magnesia powder
preparation. Production obtained from sea water and brine is
characterized by high quality: 96 – 99% MgO, high density
and micrograin size composition (40 – 80 mm), which is very
important for refractory quality. The main producers of mag
nesium oxide from sea water are USA, Netherlands, Japan,
Mexico, Israel, Ireland, and Jordan.
The economic expediency of this method is confirmed in
particular by the fact that for example in the USA in spite of
presence of a considerable amount of industrial deposits of
magnesite, magnesium is mainly prepared from sea water
and also from underground brine. According to estimates of
the USA Geological Service the proportion of Japanese,
Netherlands, and USA is currently 56% of world magnesia
powder production from sea water.
Refractories and Industrial Ceramics Vol. 56, No. 5, January, 2016
1083-4877/16/05605-0522 © 2016 Springer Science+Business Media New York
FGAOU VPO Ural Federal University, Ekaterinburg, Russia.