Analysis on the corrosion mechanism of magnesia-zirconium bricks used in glass kiln regenerators
Most of the domestic glass kiln regenerators use three-layer magnesia-zirconium checker bricks for the upper part. The bricks are fired in ultra-high temperature tunnel kilns. They are a new type of high-quality magnesia refractory material combining periclase-forsterite-zirconite. . Before use, magnesia-zirconium bricks have produced large stable forsterite and zirconium oxide, and are closely surrounded by periclase. Due to the strong corrosion resistance of forsterite and zirconium oxide, the corrosion resistance of the bricks is improved. The highest temperature in the upper part of the regenerator is around 1300°C, and the magnesia-zirconium bricks can fully resist the impact of high temperatures at this temperature. With the exchange of air flow in the regenerator, a large amount of silicon, sodium, and calcium in the molten pool glass fly and a large amount of sulfur and a small amount of phosphorus in the gas adhere to the surface of the brick, gradually invading the inside of the brick, and forming sodium, calcium, and magnesium. The sulfates, phosphates, silicates and their complex salts simultaneously dismember the bonding strength of the bricks, resulting in a reduction in the strength of the bricks.
1. Silicon dioxide erosion
The erosion of magnesia-zirconium bricks is between periclase and zircon. As the Si02 content increases, the CaO/Si02 ratio changes, forming new low-melting-point silicate phases, such as: diopside ( CMS2), magnesia rhodonite (C3MS2), forsterite (CMS), etc. The formation of these silicate phases leads to a large volume effect, causing cracking and spalling of magnesium zirconium bricks.
2. Erosion by sulfur and alkali vapor
The fuel water gas used produces a large amount of harmful oxide gases such as sulfur and phosphorus after combustion. At the same time, a certain amount of alkali is added as a flux when producing glass products. These substances adhere to the magnesium during the air flow exchange process in the regenerator. The surface of zirconium bricks penetrates into the interior of the bricks, deposits in the pores of the bricks and on the cleavage surface of periclase, and reacts to generate new salt substances, magnesium sulfate and anhydrous Glauber's salt (Na2S04). Change the structure of the brick and destroy the microstructure of the brick, thereby reducing the service life of the brick.
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