Clinker zoned clinkers

Cooling zone In this very short zone, clinker begins cooling as it is introduced into the cooler. 

If the feed to the kiln contains too much calcium oxide, or if the reaction in the clinkering zone is insufficiently complete, the cement contains free lime which slakes, after the cement has set. The reaction is accompanied by an increase in volume, causing blistering of the concrete. This effect is called unsoundness . 

An average temperature of cells, that have left a zone of stability, is calculated (clinker in these cells is rolling down along a line of the greatest angle). 

The cells, that occupy a zone of stability, but free of clinker due to mechanical translation, are again filled with clinker with an averaged temperature. 

Nodules of clinker, typically 3-20 mm in diameter, are formed in a semisolid state in the burning zone, and solidify completely on cooling, which begins in a short cooling zone within the kiln, and continues in a cooler. In modern plants, when the nodules leave the kiln, their internal temperatures are around 1350°C, but their surface temperatures are considerably lower. 

Fuels.—Success may be expected with confidence when anthracite (pea or No. 1 buckwheat) is used. The factors of chief importance are moisture, ash, tar, clinkering and heat value. Soft coal is used with success in down-draft or double-zone producers. 

Burning zone In this zone, the exothermic clin-kerization reaction occurs and the raw meal is transformed into clinker. 

Burning zone In this zone, approximately 20% of the kiln length, the exothermic clinkering reactions take place with temperatures in the range from 1100°C and 1450°C. 

Flame formation must be favorable to a dense, stable coating on the brick refractory lining in the burning zone of the kiln as well as to a nodular clinker formation with low dust content and correctly developed clinker phases. 

The main objective of the rotary kiln section is to transfer the heat flux from the diffusion flames to the material to allow the clinkering reaction and noduliza-tion in the burning zone. As previously described the heat is transferred by conduction, convection, and radiation mechanisms to the material. 

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