Contact: Zhang general
Contact phone: 13940740409
Contact: Stone Manager
Contact phone: 18641721806
Address: Zhenxing Road, Dashiqiao, Liaoning
Web site: www.ghref.cn
Technology development and application of basic magnesium chromium brick magnesia brick price
Alkaline brick for cement rotary kiln has 4 kinds, namely magnesia chrome brick, magnesia spinel brick, dolomite brick, magnesia zirconia brick, the development process is as follows:
1, magnesia chrome brick
The early common magnesia chrome bricks were silicate bonded magnesia chrome bricks, which had poor performance and could not adapt to chemical erosion of the new dry kiln clinker, such as liquid phase, alkali, sulfur and chlorine. Combination of common magnesia chrome brick is mainly M2S and other minerals, by C2S, C3A, clinker melt into C4AF, easy to form a low melting point of CMS, C3MS2 and erosion damage, due to poor mechanical properties of common magnesia chrome brick, which makes use of common magnesia chrome brick is limited. From twentieth Century 60s onwards, the excellent performance of direct bonded magnesia chrome brick, magnesia chrome bricks with high strength (more than 60Mpa), high load softening temperature, thermal shock stability, anti erosion performance of clinker strong, and the node kiln skin good performance, which is a lot in firing zone and thermal stability in the system of new dry process kiln on the transition zone.
Direct bonded magnesia chrome brick refers to solid phase reaction between periclase and spinel, periclase, direct binding between grain and grain. Therefore, the production of directly combined magnesia chrome bricks must have good raw material crystallization, high purity, low impurity content, high forming pressure (1000T) and high sintering temperature (1750~1800 C), so as to produce excellent direct bonding magnesia chrome bricks. The components of direct combination of magnesia chrome brick are: MgO 70%, Cr2O3 8~9%, SiO2 1.5~3%. China's large-scale cement rotary kiln directly combines magnesia chrome bricks, which still rely mainly on imports. The difference between domestic magnesia chrome bricks and imported bricks is poor quality stability and large brick type tolerances.
Because of alkali and sulfur magnesia chrome brick used in cement kiln of brick in the original Cr2O3 group in the kiln, non-toxic gas kiln material under the action of the formation of R2CrO4 and R2 (Cr, S) O4 toxic Cr6+ Cr6+ on human skin, respiratory nerve and lung cause serious harm and carcinogenic. Cr6+ public hazards have become a problem that can not be ignored. Pay attention to the elimination of chrome pollution and industrial developed countries formulated a series of standards in water conservation, environmental protection and health aspects of cement kiln flue gas and eliminate the magnesium chromium brick bricks and cement factory, workshop air drainage, the content of Cr6+ and residual brick processing control measures are strictly limited. China provides drinking water Cr6+ content is less than 0.05mg/l, the cement industry to enter the water drainage, the provisions of the Cr6+ = 0.5mg/l. Because of the requirements of environmental protection, the use of it will be limited.
Magnesia chrome brick
2, spinel brick
Spinel brick products appear early, early conventional spinel brick for sintering synthesis of spinel brick, the main chemical components of MgO, Al2O3, SiO2 is the main harmful impurities, its content is: MgO 77~86%, Al2O3 13~18%, SiO2 = 1%, CaO < 1%. High temperature strength and load softening temperature, better anti reduction performance, better thermal shock stability and mechanical stress resistance. But early conventional spinel brick on thermal stress sensitivity, salt erosion ability is insufficient, coating performance is poor, has not been widely used in cement kiln, generally used only for transition belt. Along with the original fuel, expanding the scope of its use, in the firing zone at both ends of the edge area, the use of conventional spinel brick kiln system has become the weakest link. Because the conventional spinel brick, magnesia alumina spinel in spinel MgO Al2O3 eroded by C3A in clinker under high temperature, the formation of melting aluminum rich C12A7 is only 1360 DEG C, the formation of C4A3S in sour condition, the characteristics of mineral as parts of the formation of kiln crust, particularly rich in alkaline conditions, kiln the skin is very easy to burn, skin defect caused by kiln, clinker and salt to melt infiltrated brick in open channel, so that it also increased the possibility of overheating, so that it becomes the precalciner kiln using high alkali and sulfur fuel (fuel) after the kiln lining life of the shortest position.
In order to adapt to the original fuel used to expand the scope of material requirements in the premise of ensuring good thermal shock resistance, decreasing the content of spinel spinel brick, which decreased the content of Al2O3 to 3~5%, in order to improve the anti erosion ability of salt. Take the pre synthesized spinel (sintered spinel or fused alumina and magnesia spinel) and special sintering synthesis methods, such as pre spinel particles formed by the reaction, and the reaction of spinel formation in the matrix synthesis of sintered brick, thus reducing the content of Al2O3 in spinel brick, increase the content of MgO, the to improve the performance of refractory brick, while improving the sensitivity of brick on thermal stress and salt erosion.
3, dolomite brick
In twentieth Century 50s the dolomite brick, because dolomite brick containing a large number of f-CaO, easy to react with C2S in clinker, formed on the surface of the brick to C3S stable kiln crust characteristics of mineral, is suitable in the firing zone use.
Compared with the spinel dolomite brick, magnesia chrome brick, dolomite brick kiln skin hanging the best performance, and the brick kiln crust with dense, strong adhesion, magnesia chrome brick of spinel brick coating performance is the worst. In the cement kiln has stable kiln skin protection parts, service life and the optimal effect of dolomite brick.
But because f-CaO is easy to absorb water, easy absorption of the dolomite brick during storage and to stop the kiln, in unstable operation, open the rotary kiln frequently in dolomite brick will absorb moisture metamorphism. At present, annual operating rate of less than 80% do not use dolomite brick kiln. Due to moisture absorption and deterioration of dolomite brick, its use is limited.
In three kinds of alkali erosion, alkaline brick, dolomite brick, brick of spinel, magnesia chrome brick is the worst.
The ability of conventional dolomite brick thermal shock damage is the worst, adding 1~3% in conventional zirconia in dolomite brick, can change the properties, increase the permeability of zirconium dolomite brick than conventional dolomite brick, adding zirconium after dolomite brick can improve thermal shock stability is poor, and improve the salt resistance of brick inhibition ability. In addition, in order to meet the requirements of calcined industrial waste, has developed a low porosity increase of zirconia magnesia dolomite brick, this brick not only keep the performance of easy coating, also has high resistance to alkali, sulfur, chlorine and other harmful substances erosion and excellent abrasion resistance.
4, magnesia zirconium brick
The magnesia zirconium brick, which appeared in 70s twentieth Century, was used in the precalcined kiln in 90s. Because the use of industrial waste fuel increases the enrichment of hazardous materials in the kiln. If the sulfur content in the fuel is high, when the temperature of the upper transition zone exceeds (1500 degrees), the spinel brick will easily be eroded by clinker, generating C12A7 or C4A3S, resulting in the dense densification and damage of firebricks.
Because the melting point of zirconia is 2715 C, it is eroded by the clinker when the temperature is over 1660. Therefore, magnesia zirconia brick has high refractoriness, and ZrO2 has the function of micro crack toughening. Zirconium brick has the characteristics of large flexural strength under hot and cold conditions.
Magnesia zirconia brick has the advantages of resistance to SO3, CO2, alkali steam, Cl and other harmful substances, erosion resistance of clinker, oxidation reduction atmosphere, and high compressive strength. The trend is expanding in the harsh conditions of the kiln. The trend is to further improve the performance and reduce the production cost under the premise of maintaining good performance, so that it is easy for popularization and application.