Synthetic refractory raw materials are two or more natural raw materials or industrial raw materials, after fine grinding, homogenization and high temperature treatment (sintering or melting) to form the expected mineral phase. Synthetic raw materials can be artificially controlled in terms of chemical composition and mineral composition according to the purpose of use, and have multiple properties superior to natural raw materials. The refractory raw materials that exist in nature but have no mining value and are very important can also be obtained through artificial synthesis.
In the process of synthesizing refractory raw materials, batching, homogenization and high temperature treatment are particularly important. Synthetic raw materials inevitably have impurities, so the actual composition and performance of the raw materials are less than theoretical values. In order to obtain synthetic raw materials with good performance, the compounding generally deviates from its theoretical composition point. For example, when synthesizing cordierite, AzO3 is usually increased to more than 38%; when synthetic magnesia alumina spinel, MgO is usually increased to more than 32% or AlzO3 is increased to more than 77% to form magnesium-rich spinel or aluminum-rich spinel.
Homogenization is especially important for the synthesis of refractory raw materials by sintering. In order to obtain synthetic raw materials with uniform phases, the natural raw materials, industrial raw materials and additives used should be strictly metered, thoroughly mixed and finely ground, so that the components are highly uniformly dispersed. The wet mixed grinding process can guarantee the quality of synthetic raw materials to the greatest extent. The expected minerals can be formed only after the materials are mixed with high temperature treatment. Commonly used are high temperature sintering method and melting method (electric melting method). The raw material synthesized by the sintering method is actually the reaction sintering of batch materials at high temperature. Its process is easy to control. Commonly used sintering equipment includes inverted flame chamber, shuttle chamber, shaft kiln, rotary kiln and tunnel kiln. Compared with the sintering method, the electric melting method has a simplified process, high melting temperature, higher purity of synthesized raw materials and good crystal development, so some properties are better than the sintering method. It is a very promising method for the synthesis of refractory raw materials in the future.
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