Description: Magnesia alumina bricks include ordinary magnesia alumina bricks, magnesia alumina spinel bricks and modified magnesia alumina spinel bricks. In the firing process of magnesia alumina bricks, MgO and Al203 react at high temperatures to form a high temperature mineral phase of magnesia alumina spinel (MgO·Al203). Magnesium-aluminum spinel has a small thermal expansion coefficient and isotropic thermal expansion, which can reduce the thermal stress caused by temperature changes. Magnesia alumina bricks have good thermal shock stability and other thermomechanical properties.
Title: Application of different magnesia-alumina bricks in kilns
Keyword: Magnesia alumina brick, kiln, application, type
Ordinary magnesia alumina bricks are made of ordinary sintered magnesia and high alumina bauxite clinker as raw materials. The granular material for making bricks is sintered magnesia, and the powder is a mixed powder of sintered magnesia and high alumina bauxite clinker. During the firing process, magnesia-aluminum spinel minerals are formed in the matrix of the brick. Used in steel-making open-hearth furnaces, electric furnaces, glass furnaces, tunnel kilns, shuttle kilns and other furnaces for the firing of refractory products.
Magnesia alumina spinel bricks are also called periclase-spinel bricks. It uses high-purity fused magnesia or high-purity two-step calcined magnesia and high-purity pre-synthesized magnesia-aluminum spinel as the main raw materials, using precise ingredients, high-pressure molding, and high-temperature firing production processes. Compared with magnesia-chrome bricks, this magnesia-aluminum composite brick not only eliminates the harm of hexavalent chromium, but also has good corrosion resistance, oxidation-reduction resistance, heat resistance and high temperature volume stability. It is a large and medium-sized cement The most practical chromium-free refractory material for the transition zone of the rotary kiln. It has also been used in high temperature equipment such as lime kilns, glass kilns and refining devices outside the furnace, and has also achieved good results. The physical and chemical indicators of the magnesium-aluminum spinel brick produced by a domestic refractory factory are: MgO82.90%, Al20313.76%, SiO21.60%, Fe2O30.80%, apparent porosity 16.68%, volume density 2.97g/cm3 , Compressive strength at room temperature is 54.4MPa, and flexural strength at 1400°C is 6.0MPa.
Magnesium-aluminum spinel bricks have been successfully used in the transition zone of cement rotary kilns, but they are prone to structural embrittlement and structural spalling when used in the firing zone, difficult to hang on the kiln skin, and have poor resistance to alkali steam and liquid phase permeability of cement clinker. And the poor ability to resist the mechanical stress caused by the deformation of the kiln body limits the application in the firing zone. For this reason, researchers have developed modified magnesia-aluminum spinel bricks suitable for the firing zone of cement rotary kilns.
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