INFLUENCE OF MICROSTRUCTURE ON FORMATION
OF DETERIORATION LAYER IN PERICLASE-HERCYNITE BRICKS
and Jia-lin Sun
Translated from Novye Ogneupory, No. 5, pp. 39 – 43, May, 2016.
Original article submitted September 7, 2015.
The microstructure of the original layer and the cement melt-penetrated layer of a used periclase-hercynite
brick from a cement rotary kiln with a daily output of 5000 tons for 12 months was studied by XRD, SEM,
EDS, and a mercury porosimeter. The results show that the cation diffusion between hercynite and periclase
particles in the brick at high temperatures decreases the pore size of the brick. The pore size in the original
layer is located mainly in the range of 4 – 20 mm; the decreased pore size increases the penetration resistance
of the cement melt to the inside of the brick and makes the cement melt react with the pore walls better. The
components of the matrix pore walls such as MgO and Al
dissolve in the cement melt, enhancing the hot
properties of the penetrated melt, decreasing the penetration depth, and slowing the formation of the deteriora-
tion layer. The pore structure and the element distribution endow the brick with good thermal shock resistance.
Keywords: periclase-hercynite bricks; microstructure; cement melt; burning zone of cement rotary kilns
Cement rotary kilns are commonly composed of the pre-
heating zone, decomposition zone, upper transition zone,
burning zone, and lower transition zone [1, 2], in which, the
burning zone possesses the highest temperature and the most
severe service condition for refractories. Refractories for the
burning zone undergo high temperature and furnace charge
wear and endure the chemical corrosion of cement melt,
structure stress, the as-resulted structural spalling damage,
and so on . The most fatal damage for refractories used in
the burning zone of cement rotary kilns is the structural
spalling [4 – 6].
As the traditional refractories for the burning zone of ce
ment rotary kilns, magnesia chrome bricks have excellent
kiln coating ability and good chemical corrosion resistance
[7 – 10], and their service life ranges from 8 to 12 months.
However, stopping kiln operation must be avoided during the
application of magnesia chrome bricks because it will lead to
spalling, rupture, or even failure of the magnesia chrome
bricks, which is the biggest disadvantage of the bricks.
Compared with the traditional magnesia chrome bricks,
the recently developed chrome-free periclase-hercynite
refractories are environmental friendly and have become an
important trend for chrome-free refractories for the burning
zone of cement rotary kilns . What’s more, the bricks
have outstanding structure stability against temperature fluc
tuations [12 – 16]. Even when used in the rotary kiln where
kiln maintenance happens regularly, they still perform well,
and rupture happens rarely. This is an overwhelming advan
tage over magnesia chrome bricks and magnesia calcia
bricks [12 – 17].
The chemical composition of magnesia chrome bricks
for the burning zone of cement rotary kilns is usually as fol
lows: MgO 60 – 85%, Al
1 – 4%, Fe
2 – 7%, and
3 – 12%; while that of the periclase-hercynite is MgO
86 – 89%, Al
4.8 – 6.2%, and Fe
4.0 – 5.3% . The
two bricks have similar apparent porosity, bulk density, and
crushing strength, and they are both magnesia refractories
with periclase as the major phase. The only difference is that
the magnesia chrome brick contains Cr
, which increases
the viscosity of the cement melt and retards the corrosion of
cement melt [18, 19]. However, they have very different per
formances, especially in thermal shock resistance and struc
tural spalling resistance.
By studying the used magnesia chrome bricks, it is found
that the penetration is deep and the deterioration layer is
Refractories and Industrial Ceramics Vol. 57, No. 3, September, 2016
1083-4877/16/05703-0267 © 2016 Springer Science+Business Media New York
School of Materials Science and Engineering, University of Sci
ence and Technology Beijing, Beijing 100083, China.
Department of Materials Science and Engineering, China Univer
sity of Mining and Techonology (Beijing), Beijing 100083, China.