1, CALY PRODUCTS
Clay products are produced based on clay clinker as aggregate, soft clay as binder, is a refractory product which AL2O3 content is in 30%-48% .
2, PROPORTIONING AND MIXING
With the combination ratio of clay clinker and clay binder, it should determine according to the product use, quality requirements, shapes, dimensions, properties of raw materials and process technology. For example the blast furnace brick and ladle, produced by the method of multi-filler formula which clinker account for 70%-90%, and for special clay products, clinker accounted for 30%-40%. General standard & common products have large proportion which accounted for 50%-60%.
Clay binder is added as the form of fine powder, if according to the requirements of the bulk density of the particle, when clay clinker and clay binder powder is surplus, the grain size of clay binder should meet the requirements of particle ratio.
About the amount of adding water and pulp waste liquid, should be according to the molding method and material properties, such as when semi dry molding clay has less water, and multiple clinker products with a small proportion of the clinker, especially products with complex shape and binding of raw clay is poor, often adding pulp waste liquid 1% -2% (density 1.2-1.25g/cm3), in order to improve the strength of brick.
Mixing in the mixer 4-10min. and high quality products require mixing 15-25min
3, MOLDING AND DRYING
Clay products by plastic molding, its volume density is 2.0-2.2g/cm3 .for semi dry method, as the size and quality of the brick product requirements are different, forming pressure change between 40-80Mpa. The bulk density of the products is in 2.1-2.3g/cm3. The block by plastic molding need dry in the natural air for 1-5 days, and then dry in the desiccator. Keeping the moisture content of less than 2% as well, it can increase the rate of finished products.
4, FIRING HAVE 4 STAGES
1 Room temperature - 200ºC, the phase remove water from embryo of brick. The elimination of the steam will cause a greater pressure on the steam, if the temperature rises too fast, the steam pressure will crack the embryo of brick, so the heating rate should be slow.
2 200-900 ºC, there is the decomposition of carbonate, iron oxidation, decomposition of organic matter, clay decompose and discharge crystalline water, embryo of brick contract about 0.5%, will not produce greater stress, this stage can be rapidly heating.
3 900-1380 ºC is the stage of mullite formation, liquid phase appearance and embryo sintering, at this stage, will have strong contractions of brick, about 2%-4%. if excessive heat or uneven heating, will make the products caused by the crack, so the temperature is slower, firing control.
4 Room temperature- 1380 ºC, is cooling stage, occurrence of mullite slow crystallization, solution fixed, with normal contraction, generally at 1000-800 ºC should be slow, because of the clay brick with good thermal shock resistance, it can cool faster, may appropriately use a blower for cooling.