In recent times with large industrialization in mining and the cement sector, the
environment conservation needs to be addressed by all the concerns. The government
has strengthened the environment protection laws under the MOEF (Ministry of
Environment and Forests) for all the sectors. All new cement plants are giving due
diligence on selection of equipment and technology best for the environment at
the beginning of the project.
In a cement plant the major dust prone areas are wagon tippler, truck tippler, lime
stone crusher hopper while unloading limestone and various transfer points in
material handling system. The fugitive emission in these areas not only affects
the environment but also adversely deteriorates the equipment life, increases the
operating cost of equipment and is a great risk to the human health. There are
various technologies available to minimize the dust generated either by providing
the dust collectors or the dust suppression system either by water spray nozzles
or Cold Fog systems.
6.1 Dust Collectors
The principle of the bag filter is as follows. The dust-laden air enters the bag filter.
The air is uniformly distributed through baffles before entering in to bags. Initially
a coat of dust forms on the bags. Subsequently, this coat acts as the filtering medium.
The dust is accumulated on filter cloth while the air passes thorough the filter bags
from outside to inside. The accumulated dust powder is dislodged from the bags
by reverse pulse-jet air intermittently. The dislodged dust powder falls on bottom
cone and is discharged through rotary air locks or flap gates discharge valves for
ongoing process. The dust free air is sucked by induced draft fan and is exhausted
to atmosphere.
The system consists of the bag filter casing, filter bags mounted on cages, the
cleaning system, and compressed air, the fan with ducting and rotary air locks or
Double flap valves.
The followings are the advantages and disadvantages of the bag filters compared
to the Cold fog system particularly for the crushed limestone and additive material
handling systems.
- Advantages
It is cost economical when it is use for the single point location.
It is used almost for all type of material handled.
It is proven system for any type of dust including limestone and additive
handling systems. - Disadvantages
It requires the extra space for the installation.
The transfer points supporting structure is required to be designed to take
care of load of the bag filter systems.