INVESTIGATION OF TIO
-ADDED REFRACTORY BRICK PROPERTIES
FROM CALCINED MAGNESITE RAW MATERIAL
Y. K. Kalpakli
Translated from Novye Ogneupory, No. 7, pp. 56 – 60, July 2008.
Original article submitted November 27, 2007.
This paper is the second part of a study on recycling magnesite and chromite ore (in the 0 – 10
powder, which remains as a production process waste. In this work, 90% magnesite-10% chromite
composition was used as a brick composition. Compaction pressure, sintering temperature, ratio of TiO
addition, and influence of bonding type on refractory properties were examined. In refractory brick
production, one of the most important parameters that affects the properties of the product is the particle size
distribution of the blend. Experiments show that using a magnesite particle size of –10
m and a chromite
particle size of –63´10
m affects the properties of the product in a positive way. Experiment blends with the
particle sizes selected above were used. Magnesite ore was used in experiments after calcination at 1200°C for
four hours. In the experiments we mention, MgCl
solutions were used as a bonding agent, as a
result of which a 6% bonding ratio of MgCl
solutions was determined as optimum. The effect of
compacting pressure on the refractory properties was studied, and the optimum compacting pressure was
determined as 180 MPa. For bricks prepared using calcined magnesite, the optimum sintering temperature
was found to be 1750°C. The positive effect of TiO
addition on the magnesite chrome refractory brick
structure has been reported in the literature. Thus, 1, 3, 5, and 7 wt.% TiO
ratios were used in the blend, and
the refractory properties were positively affected by the 3% TiO
addition. Taking the result of the MgCl
bonding solution into consideration, it is clear that the refractory properties of brick can be improved
by using a mixture of MgCl
bonding solutions. In light of the above concept, bonding mixtures
with 1:3, 1:5, and 1:10 ratios were prepared, and these bonding mixtures were studies as a bonding material.
The experimental results show that the cold crushing strength (CCS) and volume density of bricks increase,
whereas the porosity decreases when a 1:5 ratio of MgCl
in the bonding mixture and 3% TiO
addition were used. Microstructural study of the produced bricks was done using scanning electron
microscope (SEM). In addition to this, the phases forming the structure of brick were examined via x-ray
diagrams of the material. In bricks where a mixture of a 1:5 MgCl
bonding solution was used as
bonding agent and 3% TiO
was added, spinel (magnochromite (MgCr
)), magnesium orthotitanate
), monticellite (CaMgSiO
), and forsterite (Mg
) phases were found. The perovskite phase was
not observed during the experimental study.
The aim of this study is to reuse the waste magnesite and
chromite dust with particle size below –10
m for refractory
brick production. Magnesite ore is used in refractory
production after being sintered, but due to the transport of
dust to from the movement of gases coming out from the
cold end of the rotary furnace, magnesite dust is not suitable
for sintering in a rotary furnace . Previous studies on
calcination of magnesite have shown that calcination at low
temperatures gives MgO, which is to moisture, and CO
found in such a medium. To achieve physically and chemi
cally stable magnesite, the most suitable calcination tempe
rature has been found to be about 1200°C .
Chemically bonded refractory bricks are pressed with the
addition of a chemical binder in order to strengthen them .
Magnesia binders are obtained from caustic magnesite
], which are magnesium chloride and magnesium
sulfate solutions .
In magnesite–chromite refractories, the periclase-chro
mite-spinel bond is stronger when the chromite particle size
used is fine .
Refractories and Industrial Ceramics Vol. 49, No. 4, 2008
1083-4877/08/4904-0314 © 2008 Springer Science+Business Media, Inc.
Yildiz Technical University, Faculty of Chemistry and Metallurgy,
Department of Chemical Engineering, Istanbul, Turkey.