Cement grinding
In the Esch plant, cement is ground according to the following steps
Clinker unloading
The clinker produced in Rumelange is delivered by rail. The existing trains of 15-19 covered waggons are discharged by a de-dusted unloading and transportation facility either directly into the intermediate silo of the cement mills or into tonnes storage silo of 40 000 tonnes capacity.
The unloading device also allows a dust free unloading of trucks.
The additional components - anhydrite and limestone - are delivered by trucks which discharge into separate unloading installations to feed the corresponding intermediate silos of the mills.
Round stockpile for blast furnace slag
The second most important material for manufacturing cement is water granulated blast furnace slag, a by-product of pig iron production in blast furnaces.
This slag sand is delivered by rail or truck and is stored on a circular stockpile for homogenization. From there, the wet slag is transported by rubber conveyor belt to the intermediate silos in the mill building.
Before entering the ball mills, the slag is dried. For one of the mills this takes place in a vertical tube dryer, where hot air dries the slag during the pneumatic transport in a vertical tube. For the other ballmill, drying is made in a drum dryer which is flanged to the mill.
Ball mills
The two-chamber ball mills consist of armored, with hardened steel balls filled cylinders, which are driven by electric motors.
In these mills, the main components clinker and slag, together with anhydrite - to regulate the setting - and limestone are ground in different proportions according to the desired cement type. The finished cement is separated in an air separator behind the mill and the air required for the transport of cement is dedusted by bag-filters. The cement is then cooled down in a cement cooler and conveyed by air-slides and bucket elevators to the cement silos.
Laboratory
During cement grinding, cement samples are continuously taken and analyzed.
Based on the results, the fineness and the composition is corrected in order to ensure a homogeneous product. In the company's own laboratory, standardized tests of cement (such as setting time and normal strength) and chemical analysis are performed on modern laboratory equipment in accordance with the applicable standards.
A corresponding quality management system and an external quality control according to European Standard EN 197 exists in order to ensure a quality product.
Loading facilities
Most of the cement is supplied as bulk cement by special tank trucks.
It is the driver himself who loads the truck by using one of the 11 shipping roads disposing of 7 single or multiple chamber silos. The driver only needs to place correctly its truck under the silo assigned to him by the dispatch personnel and to enter the desired weight. A security system with magnetic cards prevents that the driver can load the wrong type of cement.
From one of the multiple chamber silos, the three types of cement, which are delivered in bags, are pneumatically pumped into the pre-silos of the packaging plant.
Roto-packer for bag cement
In the Esch plant, actually 8 different cement qualities are produced in different standardized classes :
- • Portland cements
- • Portland Blast Furnace Slag cements
- • Blast Furnace Slag cements
- • Portland Blast Furnace Slag cements