What is difference Between Acidic, Neutral and Alkaline Refractories? This article will introduce the details to you.
Refractory materials generally refer to inorganic non-metallic materials with a fire resistance of more than 1580 ℃. It includes natural ores and various products made through certain processes according to certain purpose requirements. It has certain high-temperature mechanical properties and good volume stability. It is a necessary material for all kinds of a-temperature equipment. There are many classification methods of refractory materials. According to chemical composition, it can be divided into acidic, neutral and alkaline refractories.
Acidic Refractory
Acidic refractories usually refer to refractories with SiO2 content greater than 93%. Their main feature is that they can resist the erosion of acidic slag at high temperature, but are easy to react with alkaline slag.
Acid refractory materials can be divided into the following categories based on their acidity:
(1) Strong acid silica brick, amorphous silica refractory, quartz glass products, fused silica re-bonding products;
(2) Medium acid semi silica refractory and pyrophyllite refractory;
(3) Weak acidic clay refractory material.
Zircon refractory materials and silicon carbide refractory materials, as special acidic refractory materials, are also classified as acidic refractories.
Alkaline Refractory
Alkaline refractory materials generally refer to the refractory materials mainly consisting of magnesium oxide (MgO) or calcium oxide(CaO).
These refractories have a high fire resistance and a strong resistance to alkaline slag. Alkaline refractories are mainly used in alkaline steelmaking furnaces, non-ferrous metal smelting furnaces, kilns for the glass and cement industries, and other thermal equipment.
Its main products are magnesia, magnesia-chrome, magnesia-olivine, magnesia-aluminium, dolomite and lime. Magnesium, dolomite and limestone are strongly alkaline, while Chrome-Magnesia and magnesia-chrome, magnesia-olivine and spinel are weakly alkaline.
There are many types of alkaline refractory materials :
According to chemical mineral composition, it can be divided into magnesium, magnesium spinel, dolomite, olivine, limestone, etc.
If classified by other methods, it can be divided into fired alkaline refractory products, unburned alkaline refractory products, and fired oil immersed alkaline products.
Non burned alkaline products refer to tar bonded products, which include asphalt bonded magnesium bricks, dolomite bricks, and magnesium dolomite bricks;
Burnt oil immersed alkaline products refer to products that have been impregnated with asphalt, including oil immersed magnesium dolomite bricks, magnesium bricks, dolomite bricks, and lime bricks.
Neutral Refractory
At high temperatures, refractories that do not react significantly with acidic or alkaline slag are called neutral refractories (also known as amphoteric refractory material).
Carbon bricks, chromium bricks (mainly composed of Cr2O3), and high alumina refractory materials (mainly composed of Al2O3 and SiO2) all belong to this category.
However, high alumina refractories are neutral refractories with acidic tendency; Chromic materials are neutral refractories with alkaline tendency.
Neutral refractory materials are widely used, and almost all types of thermal equipment need to be used to some extent.
High alumina refractory products have high ‘cold mechanical strength’, ‘load softening point’, and ‘resistance to rapid cooling and heating times’, but they have significant volume shrinkage and are mainly used for the top of steelmaking electric furnaces.
Carbon bricks are a high-grade refractory material with a fire resistance of around 3000 ℃, but they should not come into contact with oxidizing flames or slag containing a large amount of iron oxide during use.