Re: raw meal silos
Generally; silo or aerated gravity silo systems are designed according to these three concepts:
1- As inverted cone silos
2- As central chamber silos
3- As multiple-outlet silos
1- The inverted cone concept: The inverted cone silo represents the pure concept of the aerated gravity silo. The silo is, as said by its name, equipped with a huge inverted cone covering most of its centre bottom area. The remaining annulus is divided into segmented areas that are covered by open airslides. Each sector is equipped with its own outlet. Raw meal is activated predominantly at the silo’s circumference by sequential air supply to the individual sectors, avoiding by this the formation of huge zones of stagnant product.
2- The central chamber silo concept: The central chamber silo configuration refers to a concept that uses the inverted cone as a centre chamber for additional reduction of residual compositional short-term variations. The annulus is divided into segmented areas that are covered by open airslides as for the inverted cone configuration. Again raw meal is activated by sequential air supply to the individual sectors. Design of the central chamber differs in shape (conical or cylindrical) and volume. Compressed air is introduced for air-fluidisation through a permeable media (open airslides) covering the chamber bottom that is typically divided into quadrants. The blending potential of a central chamber silo is slightly better compared to that of a simple inverted cone silo.
3- The multiple-outlet silo concept: Multiple-outlet type gravity silos follow the concept of blending the raw meal while it is discharged via different outlets at different rates.
This type of silos is available in various configurations:
#. The FLS’ Controlled Flow (CF) silo concept: The silo bottom of the CF silo is divided into seven identical hexagonal sectors, each of which has its centre outlet covered by a pressure relief cone made of steel. Each of the hexagonal sectors is subdivided into six triangular segments all equipped with open aeration boxes. Raw meal extraction follows a sequence where three segments positioned at three different outlets are aerated at a time. From the outlets it is conveyed at different rates to the central mixing tank installed below the silo. The aeration sequence is cyclic in a way that all the 42 segments will be activated once within about 15 minutes.
#. The Fuller-Kovako Random Flow silo concept:
Again the silo bottom of the Random Flow silo is divided into a number of sectors. In addition these sectors are subdivided in six discharge zones and equipped with a closed collecting airslide. Each discharge zone has its pick-up point to the collecting airslide from which the raw meal is transferred to the centre mixing tank installed below the silo. Selective aeration is the means by which raw meal is discharged out of three different silo areas at a time. Again aeration sequence is cyclic.