What Are The Classification Ways Of Refractory Raw Materials?
There are many kinds of refractory raw materials and various classification methods. There are six categories in general.
First, according to the chemical components of refractory raw materials classification
It can be divided into oxide raw materials and non-oxide raw materials. With the development of modern science and technology, some organic compounds have become the precursor materials or auxiliary materials of high performance fire resistance raw materials.
Two, according to the chemical components of refractory raw materials classification
According to chemical characteristics, fire resistance raw materials can be divided into acid fire resistance raw materials, such as silica, zircon, etc.; Neutral fire resistance raw materials, such as corundum, bauxite (acidic), mullite (acidic), pyrite (alkaline), graphite, etc.; Alkaline fire resistance raw materials, such as magnesia, dolomite sand, magnesia calcium sand, etc.
Three, according to the production process function classification
According to its role in refractory production process, refractory raw materials can be divided into main raw materials and auxiliary raw materials.
The main raw material is the main body of refractory material. Auxiliary raw materials can be divided into binders and additives. The function of the binder is to make the refractory body have enough strength in the process of production and use. Commonly used are sulfite pulp waste liquid, asphalt, phenolic resin, aluminate cement, sodium silicate, phosphoric acid and phosphate, sulfate, and some of the main raw materials themselves have the role of bonding agents, such as bonded clay; The role of additives is to improve the production or construction process of refractory materials, or strengthen some properties of refractory materials, such as stabilizer, water reducing agent, inhibitor, plasticizer, foaming agent dispersant, expansion agent, antioxidant, etc.
Four, according to the nature of acid and base classification
According to acid and alkali, refractory raw materials can be mainly divided into the following five categories.
(1) Acidic raw materials
Mainly siliceous raw materials, such as quartz, squamquartz, quartzite, chalcedony, chert, opal, quartzite, white silica sand, diatomite, these siliceous raw materials contain silica (SiO2) at least in more than 90%, pure raw materials have silica up to more than 99%. Siliceous raw materials are acidic in high temperature chemical dynamics, when there are metal oxides, or when in contact with the chemical action, and combined into fusible silicates. Therefore, if the siliceous raw material contains a small amount of metal oxide, it will seriously affect its heat resistance.
(2) semi-acidic raw materials
It is mainly refractory clay. In the past classification, clay is listed as acidic material, actually is not appropriate. The acidity of refractory raw materials is based on free silica (SiO2) as the main body, because according to the chemical composition of refractory clay and siliceous raw materials, the free silica in refractory clay is much less than the siliceous raw materials.
Because there are 30%~45% alumina in the general refractory clay, and alumina is rarely free state, bound to be combined with silica into kaolinite (Al2O3·2SiO2·2H2O), even if there is little excess silica amount, the role is very small. Therefore, the acid property of refractory clay is much weaker than that of siliceous raw materials. Some people believe that the refractory clay at high temperature decomposition into free silicate, free alumina, but not unchanged, free silicate and free alumina will be combined into quartz (3Al2O3·2SiO2) when continued to be heated. Quartz has good acid resistance to alkaline slag, and because of the increase of alumina composition in the refractory clay, the acid substance gradually weakened, when alumina reached 50%, alkaline or neutral properties, especially made of clay brick under high pressure, high density, fine compact, low porosity, resistance to alkaline slag is stronger than silica under high temperature conditions. Quartz is also very slow in terms of its erosivity, so we consider it appropriate to classify refractory clay as semi-acidic. Refractory clay is the most basic and widely used raw material in refractory industry.
(3) neutral raw materials
Neutral raw materials are mainly chromite, graphite, silicon carbide (artificial), under any temperature conditions do not react with acid or alkaline slag. There are currently two such materials in nature, chromite and graphite. In addition to natural graphite, there are artificial graphite, these neutral raw materials, have significant resistance to slag, the most suitable for alkaline refractory materials and acid refractory insulation.
(4) alkaline refractory raw materials
Mainly magnesite (magnesite), dolomite, lime, olivine, serpentine, high alumina oxygen raw materials (sometimes neutral), these raw materials have strong resistance to alkaline slag, mostly used in masonry alkaline furnace, but especially easy and acid slag chemical reaction and become salt.
(5) Special refractory materials
Mainly zirconia, titanium oxide, beryllium oxide, cerium oxide, thorium oxide, yttrium oxide and so on. These raw materials have different degrees of resistance to all kinds of slag, but because the raw material source is not much, can not be used in a large number of refractory industry, can only be used in special circumstances, so it is called special fire resistance raw materials.
Five, according to the generation of raw materials classification
According to the generation of raw materials, can be divided into natural raw materials and synthetic raw materials two categories.
(1) natural refractory raw materials
Natural mineral raw materials are still the main body of raw materials. Minerals that occur in nature are composed of the elements that make them up. At present, it has been proved that the total amount of oxygen, silicon and aluminum three elements account for about 90% of the total amount of elements in the crust, and oxide, silicate and aluminosilicate minerals account for obvious advantages, which are very huge reserves of natural raw materials.
China has rich refractory raw material resources, a wide variety. Magnesite, bauxite, graphite and other resources can be called the three pillars of China's refractory raw materials; Magnesite and bauxite, large reserves, high grade; Excellent quality refractory clay, silica, dolomite, magnesia dolomite, magnesia olivine, serpentine, zircon and other resources are widely distributed.
The main varieties of natural raw materials are: silica, quartz, diatomite, wax, clay, bauxite, cyanite mineral raw materials, magnesite, dolomite, limestone, magnesite olivine, serpentine, talc, chlorite, zircon, plagiozircon, perlite, chromium iron and natural graphite.
Six，According to chemical composition, natural refractory raw materials can be divided into:
Siliceous: such as crystalline silica, quartz sand cemented silica, etc.;
② semi-siliceous (phyllachite, etc.)
③ Clay: such as hard clay, soft clay, etc.; Combine clay and clay clinker
(4) High aluminum: also known as jade, such as high bauxite, sillimanite minerals;
⑤ Magnesium: magnesite;
⑥ Dolomite;
⑦ Chromite [(Fe,Mg)O·(Cr,Al)2O3];
Zircon (ZrO2·SiO2).
Natural raw materials usually contain more impurities, the composition is unstable, the performance fluctuates greatly, only a few raw materials can be used directly, most of them have to be purified, graded or even calcined to meet the production requirements of refractory materials.
(2) synthetic fire resistance raw materials
The types of natural minerals used for raw materials are limited, and they are often unable to meet the requirements of high quality and high technology refractory materials for the special requirements of modern industry. Synthetic refractory raw materials can fully reach people's pre-designed chemical mineral composition and structure, its texture pure, dense structure, chemical composition is easy to control, so the quality is stable, can manufacture a variety of advanced refractory materials, is the main raw material of modern high skill and high technology refractory materials. The development of synthetic refractory materials is very rapid in the last twenty years.
Synthetic refractory raw materials are mainly magnesium aluminum spinel, synthetic mullite, seawater magnesia, synthetic magnesium cordierite, sintered corundum, aluminum titanate, silicon carbide and so on.