Clinker is a nodular material produced in the kilning stage during the production of cement and is used as the binder in many cement products. The lumps or nodules of clinker are usually of diameter 3-25 mm and dark grey in color. It is produced by heating limestone and clay to the point of liquefaction at about 1400°C-1500°C in the rotary kiln. Clinker, when added with gypsum (to control the setting properties of cement and ensure compressive strength) and ground finely, produces cement. Clinker can be stored for long periods of time in a dry condition without degradation of quality, hence it is traded internationally and used by cement manufacturers when raw materials are found to be scarce or unavailable.

Types of Clinker

The most common type of clinker is produced for Portland cement and its blends. The types of clinker vary depending on the type of cement for which the clinker is produced. Aside from the Portland cement blends, some special types of cement clinker are listed below:

Sulfate Resistant Clinker

It contains 76% alite, 5% belite, 2% tricalcium aluminate, 16 % tetracalcium aluminoferrite, and 1% free calcium oxide. Its production has decreased in recent years because sulfate resistance can easily be obtained by using granulated blast furnace slag in cement production.

Low Heat Clinker

It contains 29% alite, 54% belite, 2% tricalcium aluminate and 15 % tetracalcium aluminoferrite, with very little free lime. It is no longer produced because cement produced from ordinary clinker and ground granulated blast furnace slag has excellent low heat properties.

White Clinker

It contains 76% alite, 15% belite, 7% tricalcium aluminate, no tetracalcium aluminoferrite, and 2% free lime, but the composition may vary widely. White clinker produces white cement which is used for aesthetic purposes in construction. The majority of white cement goes into factory-made pre-cast concrete applications.

Low-alkali Clinker

Reduction of alkali content in clinker is done by either replacing the raw-mix alumina source with another component (thus obtaining a more expensive material from a more distant source), or installing an "alkali bleed", which involves removing some of the kiln system's high temperature gases (which contain the alkalis as fume), resulting in some heat wastage.

Belite Calciumsulfoaluminate Ternesite (BCT)

This concept is used in producing a type of clinker with up to 30% less carbon dioxide emission. Energy efficiency improves and the electricity costs for the manufacturing process are about 15% lower as well.

Traditional clinker grinding unit adopts ball mill to grind clinker, and has much dust, loud noise and high energy consumption in the process of production, it will be replaced gradually by vertical roller mill, CHAENG（Xinxiang Great Wall Machinery Co., Ltd）can provide customers with clinker grinding stations with various output.