Refractories are typically broken down into acidic, basic, and neutral. Acidic refractories consist of minerals like alumina (Al2O3) and silica (SiO2) and can be used in acid like environments. Basic refractories consist of minerals like lime (CaO) and magnesia (MgO) and can be used in basic like environments. Neutral refractories usually contain varying amounts of chrome in several forms in combination with alumina or magnesia and work well in the middle of the acid / base spectrum. Carbon containing refractories can also be classified as neutral and depending on the mixture in which it is used can deal with a range of acid, neutral and basic environments. The range of environments just described usually can be determined using a simple ratio of CaO /SiO2 (known as “V” ratio) taken from a slag analysis that can come in contact with the brick. Slags can penetrate or “wet” the brick it meets and degrade it if it’s not compatible. A general rule of thumb is as follows:
CaO/ SiO2 < 1.25 ---- equates to an acid environment
CaO/ SiO2 = 1.25 to 1.75 ---- equates to a neutral environment
CaO / SiO2 > 1.75 ----- equates to a basic environment
Acid Refractory Key Features: 1. Comprised of alumina (Al2O3) and silica (SiO2) in a wide range of amounts
2. Not attacked by acidic environments
3. Can be attacked by hydrofluoric and phosphoric acid and fluorinated gases.
Acid Refractories main applications:In the iron and steel industry typically used in the production of iron and the transport or containment of liquid iron and steel. In non-ferrous industrial application can be used in the production and refinement of liquids and solids when meeting the above environment criteria.
Basic Refractory Key Features: 1. Mainly comprised of CaO and MgO and carbon as required
2. Not attacked by basic environments
Basic Refractories main applications:In the iron and steel application typically in the production and refinement of iron into steel and its transport as liquid to final processing into solidified product In non-ferrous industrial applications where, extreme temperature and basic environments dictate their use.
Neutral Refractory Key Features: 1. Usually comprised of chrome ores and magnesites in varying compositions formulated for a specific environment
2. Can deal with the narrow neutral range defined above
Neutral Refractories main applications;In the iron and steel industry can still be used in the production of and transport of liquid steel or as safety linings behind other working lining compositions. In the non-ferrous industries typically used in the production of copper, lead, and nickel.