Preparation, grinding and extrusion
For preparation of the clays, a semi-dry method has been chosen. Box feeders are used to supply the raw materials to the processing line. Grinding is started in a primary crusher and completed in a disintegrator followed by a roller mill and a mixer in order to guarantee the optimum grain size of the resulting clay body ready for processing.
This mixture is delivered to a clay pit in order to enhance its homogeneity and to give the plant greater autonomy since it guarantees the continuous supply of clay. The clay pit is equipped with a bridge-type bucket reclaimer so clay is collected by an entirely automated system, enabling more efficient use of the stored raw material.
The clay body is shaped by means of a box feeder, a roller mill and an extruder.
The products are dried in a semi-continuous dryer equipped with cone-shape air recirculation fans. The dryer cars run on rails through drying tunnels between rows of air recirculation fans which distribute the air vertically to obtain greater drying uniformity over the height of the load.
The hot air required for the drying process comes from the waste kiln recovery system and from some auxiliary generators. The two air flows are mixed in a mixing box and air is drawn out by centrifugal fans, which distribute it through the entire dryer.
At the exit to the dryer, the dryer cars are handled fully automatically and the dry products are transferred to a setting machine where they are loaded onto kiln cars for firing.
The firing process is preceded by a pre-kiln so the temperature increases progressively, thus obtaining a final product of a better colour while minimizing the risk of spalling.
Firing itself is performed in a highly automated traditional “FT” tunnel kiln operating on gas. At the exit of the pre-kiln, kiln cars loaded with ware are introduced into the kiln. The kiln is equipped with all the circuits and components required to guarantee a homogeneous hot air flow through the kiln and over the entire kiln car load, the appropriate pressure at all the stages of the process to maintain the optimum temperature curve, and energy efficiency by recycling the resources used in the process.
Kiln regulation and control is also fully automated through a system that allows the customer to comprehensively monitor the drying and firing process as well as to keep close control of the parameters involved in both processes.
Unloading and pack forming
Products are unloaded from kiln cars by means of grippers that collect the layers of fired products to make horizontally and vertically strapped dispatch packages in order to ensure their stability. According to the traditional Algerian method, two gaps are left in the bottom layer of packs so they can be collected by the fork lift.
In this project, the grippers set two dispatch pack-high stacks, thus improving the efficiency of lift trucks that take them to the storage area.
Source Ziegelindustrie International