How should refractory fire bricks for kilns be classified and selected according to acidity and alkalinity? When choosing a matching refractory brick for a kiln, its acidity and alkalinity should be considered. Request refractory bricks for kilns – acid resistant refractory bricks. Common refractory bricks are some high melting point oxides, which can usually be divided into three categories: acidic, alkaline, and neutral according to their chemical properties.
The main components of acid refractory bricks are acid oxides such as SiO2, such as silica bricks. The main components of alkaline refractory bricks are alkaline oxides such as MgO and CaO, such as magnesia bricks. The main components of neutral refractory bricks are amphoteric oxides such as Al2O3 and Cr2O3, such as clay bricks and high alumina bricks. Request refractory bricks for kilns, most kilns can use neutral refractory bricks, such as high alumina bricks, clay bricks, and mullite bricks. There are more alkaline refractory bricks used in cement kilns and lime kilns.
Acid refractory bricks are easily eroded by reacting with alkaline substances at high temperatures. Alkaline refractory bricks are easily attacked by acidic substances at high temperatures. Neutral refractory bricks form a chemically inert variant due to amphoteric oxides such as Al2O3 and Cr2O3 after being burned at high temperatures. It is not easy to interact with acidic substances, and it is not easy to interact with alkaline substances. Therefore, it has better resistance to acid and alkali erosion.
When choosing refractory bricks, Request refractory bricks for kilns should also pay attention to the redox properties of furnace gas. If the furnace gas contains more CO, CO can easily react with some metal oxides (such as FeO) in the refractory brick at a high temperature to reduce the metal. The deposition of carbon in the gap of the refractory brick will also cause the strength of the refractory brick to decrease and break. Therefore, this kind of refractory brick requires the oxide content of iron to be less than 3% (called anti-carburizing brick). For another example, refractory bricks containing Cr2O3 (melting point 2266°C) can be used in an oxidizing atmosphere at high temperatures. If used in a reducing atmosphere, it may be reduced to metallic chromium (melting point 1857°C).
In addition, Requesting refractory bricks for kilns, also need to consider the erosion resistance of refractory bricks.
The corrosion resistance of refractory bricks refers to the ability of refractory bricks to resist the erosion and erosion of various erosive media at high temperatures. These corrosive media include various slags (blast furnaces, electric furnaces, converters, refining furnaces, non-ferrous metal smelting furnaces, calciners, and reaction furnaces). Fuel, ash, fly ash, iron filings, lime, cement clinker, alumina clinker. Garbage, liquid molten metal, glass melt, acid and alkali, electrolyte, various gaseous substances (gas, CO, sulfur, zinc, and alkali vapor), etc.
Erosion resistance is a very important indicator to measure the resistance of refractory bricks to chemical erosion and mechanical wear. For formulating the correct production process, the rational selection of refractory bricks is of great significance.
There are intrinsic and extrinsic factors that affect the corrosion resistance of refractory bricks. The internal factors mainly include the chemical and mineral composition of the refractory brick, and the structure and other properties of the refractory brick. The external ones are the nature of the erosive medium, the conditions of use (temperature, pressure, etc.), and the interaction between the erosive medium and the refractory bricks under the conditions of use.
Chemical and mineral composition of refractory bricks. Materials with different chemical compositions have different resistance to erosion. Acid refractory bricks have good corrosion resistance to acidic corrosive media, while alkaline refractory bricks have very weak resistance to acid corrosive media.
Other properties of refractory bricks. The bulk density, apparent porosity, thermal shock resistance, oxidation resistance, and high-temperature volume stability of refractory bricks have a great influence on their erosion resistance. Dense materials with high bulk density and low porosity have better erosion resistance than loose materials. When a material with poor thermal shock resistance is subjected to thermal shock, cracks or cracks will appear, so the erosive medium will enter the material and reduce its corrosion resistance. Carbon-containing refractory bricks with poor oxidation resistance will form a decarburized layer after the surface is oxidized, and the structure is loose and easy to fall off, which reduces the corrosion resistance. Materials with poor high-temperature volume stability generally also have poor corrosion resistance.
Interaction of refractory bricks with erosive media. The refractory brick reacts with the erosive medium to form a high melting point or high viscosity phase, which is beneficial to reduce the erosion of the material. Influence of the conditions of use of Request refractory bricks for kilns. It mainly includes temperature level and fluctuation, pressure, atmosphere, contact time and area, etc. High temperature, large fluctuation, high pressure or vacuum, strong corrosive atmosphere, long contact time, and large area, the more serious the erosion to the material.
Request refractory bricks for kilns, pay attention to the selection of refractory bricks and try to choose refractory bricks with similar chemical composition to the erosive medium. In addition, in the use of refractory bricks, it should also be noted that the chemical properties of the materials used should be similar to prevent or reduce the interface damage reaction between the materials used under high-temperature conditions. Request refractory bricks for kilns – acid resistant refractory bricks, please search https://www.hy-refractory.com/ for more quotations of acid resistant refractory bricks products, please contact us.
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