Automatic Feeding System
Dumpers or belts convey the coarse aggregates via feeding hopper and conveyor belts to the stock pile. From the stock pile the particular fractions are conveyed via conveying troughs onto the corresponding belts. Each specific grain size can be batched onto each belt. With these two belts the coarse aggregates are conveyed to the 150 m long cooling gallery.
The fine aggregates as well are conveyed via feeding hopper and belt to the stock pile. The fine aggregates are conveyed to the inline silo without being chilled.
Cooling of Coarse Aggregates
Water chillers produce large quantities of cold water at + 4 degree C. The cold water is sprayed via nozzles across the total length of the cooling gallery onto the rock grains greater than 5 mm. At the end of the cooling gallery we obtain a temperature of the graining of approx. + 7 degree C. The aggregates are dewatered at selected points. At the end of the cooling gallery dewatering screens dewater the material to a residual moisture of 2 %. This method is very effective because much water is accumulated in the coarse grain.
Water is then led into the sedimentation tank to have the flushed floating particles deposited. The cleaned water is now cooled again and added to the circuit.
Alternatively for other projects and according to the requirements the cooling of the aggregates can be effected in an aggregate cooling silo.
The particular cooled components are conveyed into separate compartments of the insulated inline silos. The sizes of the separate compartments of the inline silo have been dimensioned to take up the total capacity of the belt. It is important for safety requirements that each component can be conveyed via each belt into each compartment of the inline silo.
Production and Handling of Ice Flakes
Two containerized flake ice plants produce 24 hours continuously flake ice into both ice storage tanks. The requested ice is conveyed with screws from these ice storage tanks into the day tanks which provide the ice to the particular ice weighers for weighing. The requested ice can be supplied from each day tank into each of the 4 ice weighers.
The water chillers have been containerized as well. They provide the cooling of the aggregates, the ice treatment and the requested mixing water for the concrete.
Storage and Transportation of Cementitious Materials
To guarantee a sufficient quantity of cement and pozzolan on site all in all 10 x 1000 t storage silos have been installed. Pneumatic cement blower systems provide the corresponding service silos – per plant 2 silos à 150 t – from these storage silos.
Concrete Batching and Concrete Production
To obtain the requested nominal plant capacity of 500 m³/h compacted concrete 2 twin plants with a total of 4 x3 m³ twin shaft mixers have been installed.
Each twin plant is equipped with an inline silo of 4 x 100 m³. From this inline silo the particular fractions are -according to the recipe – weighed additively on the weighing belt. All materials, such as aggregates, cement, pozzolan, admixtures, cold water and ice are weighed and conveyed into the mixer.
For a homogeneous mixing of the concrete Liebherr exclusively uses twin shaft mixers from internal production. These mixers stand out for short mixing times and short discharge times. Due to special wear plates these mixers have a very long durability. The maintenance works are reduced due to a central lubrication system.
Concrete Delivery System
Below each high performance mixer an especially developed rotary system has been installed which allows feeding the high speed belt and the dumpers as well which are filled from 2 mixers at the same time. The high speed belt has been equipped with a discharge point to provide further tipping of dumpers.