Three Refractory Clinkers: Bauxite Sand, Flint Sand and Coal Gangue Sand

The clinker is one of the important materials for the refractory plants. The main component of refractory clinker is mullite (3Al2O3•2SiO2). It is made from sinter cakes sintered with hard clay (such as bauxite or kaolin) at high temperature (1300～1500℃) by crushing and screening. The refractoriness of clinkers increases with the increase of the Al2O3 content and the sintering temperature. 

The refractoriness of bauxite sand calcined from bauxite can reach up to 1800℃ when the content of Al2O3 is 71.8%. 

 

The theoretical composition of flint sand calcined from kaolin (Al2O3 • 2SiO2 • 2H2O) is 46% Al2O3 and 54% SiO2. Its density is 2.78g/cm3, Mohs hardness 5-6 and refractoriness as high as 1750℃.

 

Coal gangue is also a type of carbonaceous hard clay. Coal gangue calcined from featured coal gangue has looser texture and more pores than flint sand and shakeout are easy to clean. The presence of impurities such as Fe2O3 and CaO can affect the refractoriness. 

 

The advantages of refractory clinkers include small thermal expansion, stable volume at high temperature, high refractoriness, good resistance to slags and lower iron and iron oxides wettability than quartz. Refractory Clinker is a typical amphoteric oxide. Depending on the composition, it can be basic or neutral at high temperature. it can be used to make the model of large steel castings, core sand, coating and paste. 

 

Bauxite sand and powder can be divided into two categories according to the main crystal phase after firing. Bauxite sand can be divided into four grades according to their size. The total remaining amount after three-time screening should be no more than 95%.