As an example, the kiln feed rate for the 4500 TPD clinker is 4500 TPD x
clinkerisation factor 1.54 /24 hours = 288.75 t/hour.
Raw meal silo Capacity = 24-hour x 288.75 = 6930 tons.
- FLSmidth and Lafarge
It recommends 1-day storage capacity of the raw meal silo provided the
installation of the Cross belt analyzers and better pre blending and
homogenization stockpiles (linear or circular) with bridge type reclaimer.
If no cross belt analyzers are provided in the raw material circuits then, FLS
recommends 2 days’ storage capacity of the raw meal silo.
2.1.2 Deciding Parameters of Raw meal storage silo capacity
- Pre mill feed blending and homogenization
In the raw meal silo, it has been observed that a cavity formation inside the
storage silo takes place during the running of the mill and material falls
directly to the outlet portion of the silo, thus reducing the blending effect
to bare minimum. So it is advantageous to complete a pre blending process
during material handling from mines to raw material hoppers including the
stockpiles. The cross belt analyzer on the crusher output belt conveyor and
on the mill feed belt conveyor helps to get the uniform quality product to a
major extent. The circular or linear stockpiles with bridge type reclaimer also
help to get the uniform quality material. In this case the capacity of blending
of raw meal inside silo can be reduced.
When Pre blending of raw material is not envisaged in stockpiles and with no
cross belt analyzers then the capacity requirement of raw meal storage silo
becomes high for performing adequate blending inside the silo for uniform
quality kiln feed.
- Type of Raw Meal Grinding and its availability
In case of vertical roller mill, the major breakdowns will be, the grinding roller
bearing failure, grinding roller sealing failure and the gear box failure. All
these breakdowns take at least 5 to 6 days to rectify. If we consider this for
the storage silo capacity, then the silo capacity will be 4500 TPD x 1. 54
(Clinkerisation factor) x 6 days = 41580 MT. This is not desirable as it requires
a high capacity silo involving high capital cost. To avoid these breakdowns,
the timely preventive and predictive maintenance is required to be carryout.
The planned major stoppages for the vertical roller mill are the roller /Roller
tyre and the table liner replacement. These works also require 6-7 days and
should be matched with kiln shutdown time.
For the roller press operation, the major breakdowns will be for rollers and
bearing. These take more than 5 to 7 days to replace so the buffer stock of 7
days is quite significant in capex expenditure for 4500 TPD plant.
The running hours of the mill is reduced due to various chute and raw material
hoppers jamming due to high moisture and improper inclination angle. To