Clinker burning

The basic material of all common cements, the so-called clinker, is produced at the Rumelange plant following the procedure described below:

The basic material for the production of cement is Portland cement clinker. For its production mainly limestone and marl is used.

In the Rumelange plant these natural materials are extracted by blasting on several stages in an open air quarry, located at about 1 km from the plant on the French territory.

The excavation takes place at several stages in the open quarry by blasting at the bottom of blastholes. Wheeled loader loads the blocks on a heavy dump truck which brings this material to the primary crusher where it is pre-crushed. A belt conveyor transports it then to a secondary crusher in the plant where it is re-crushed.

Raw material bedding

Limestone (coral limestone ) and marl (a mixture of red and grey marl) are crushed to fist size and deposited in layers on 2 bedding piles for prehomogenization in order to equalize the natural chemical variations. The two raw materials are transported from the bedding with conveyor belts to the dosing silos, from which they are extracted by belt feeders, together with various corrective ingredients, in order to achieve the right mixture to feed the raw mill.

The additional ingredients are used to correct the chemical composition.

Vertical roller mill

In a vertical roller mill, the raw material components are dried with the kiln exhaust gases and at the same time ground to produce a so-called raw meal.

The chemical composition is controlled on hourly taken samples with modern analytical instruments. By making changes to the weight belt feeders, the composition is continuously corrected. The finely grounded raw meal is separated from the exhaust gases in an electric precipitator, which also separates the exhaust gas from the dust. From here, the precipitated meal is pumped to 7 mixing cells.

To further homogenize the product, their content is simultaneously emptied into into a raw meal silo with a storage capacity of 10000 t.

Rotary kiln

From the raw meal silo, the homogenized meal is fed ba air transport into the preheater, where it is heated and partially calcinated by the hot gases on its way downwards.

Passing through several cyclones, the meal, heated up to 850 ° C, reaches the inclined rotary kiln, in which, due to the inclination and rotation, the meal reaches the burning zone. Here it is burned, at a temperature of about 1,450 ° C, with partial sintering, to produce cement clinker.

The high temperature is obtained by the combustion of coal dust and other alternative fuels. At the kiln end, the bright glowing mass – the clinker - falls into the side-mounted cooling tubes around the kiln, where it is cooled by air.

Control room

From a central control room, the entire plant is electronically controlled and monitored, from the bedding to the clinker loading. All measured values of the various stages of production are - via programmable control stations – transmitted to the control room for data processing and are electronically stored. The system supervisor receives messages of every disturbance and deviance.

Moreover, remote operation sites can be reached from the control centre via telephone, radio and intercom. Disruptions can so be reported immediately to the operating staff in the plant and corrected in a short time.

Laboratory Robot

In the plant samples are continuously and automatically taken from the rough meal, the kiln meal as well as from the finished clinker and routed to the laboratory via pneumatic tubes. After a sample is processed by robot, the chemical composition is determined by a modern X-ray fluorescence spectrometer.

When deviations from the specified target values are noted either the dosage of the components is altered or corrective ingredients are added at the kiln inlet in order to produce a clinker of uniform chemical composition and constant quality.

Silos and loading

In the cooling tubes, which are around the kiln outlet like satellites , the clinker is cooled down and then stored in two clinker silos with a capacity of 50,000 tons each.

The clinker is transported to the loading installation from which it is filled in railway waggons to be transported to the grinding plant in Esch.

The shipping installation also allows to load the clinker on trucks.