CEMENT MANUFACTURING PROCESS
QUARRY The raw material from quarry is brought by dumpers.The main
raw material used in cement industry are
1)Slate
2)laterite
3)limestone
The quarry is open pit type.
First of all primary mining is done by
1) Explosive
2) T.N.T
3) Urea
If the size is greater than 1m^3 than secondary mining is
done by drilling.
MAIN CRUSHER The
type of crusher used in cherat cement factory is rotary impact type crusher.
The crusher has two rotors 1)Primary rotor and 2) secondary rotor.
Primary rotor has 6 beaters and its speed is 1987 r.p.m. The
motor which runs it is a medium voltage motor. Its crushing size is 60-70 mm
and is run in a range of 20-25 amp.
2) The crushing size of secondary rotor is 20-35 mm. It has
18 beaters and its speed is 1492 rpm.
Main crusher hopper capacity is 70 ton and overall crushing
capacity is 450 ton/hr.
DEDUSTING UNIT The
material after passing through main crusher is allowed to pass through
dedusting unit where the dust is collected by canvass cloth and the material
follows its path on conveyer belt.
The material is collected in the form of file is given to
the file stacker. There are four piles
1) Mix
pile ( height=9.2m, weight=12000-13000ton, length=75-76m)
2) Literate
pile ( containing iron ore)
3) Salete
pile ( containing silica)
4) Limestone (PI)
Safety of conveyer belt:
1) Emergency
wire
2) SCS
( Speed control Switch)
3) Local
on/off
4) Limit
Switch/Offset Switch
Crusher residue is 5% of 25 mesh
screen and moisture is 5.5-6%
RAW MILL From the
propotional unit the material is brought
to raw mill by conveyer belt . The production of raw mill is 120 ton/hr. Mill
inlet moisture is 6% and outlet moisture is 0.8%.
Residue is 12%.
Ist Chamber media size 50-90 mm.
2nd chamber size 20-40
mm.
No of Plates in ist chamber:
No of plates/row =54
No of row =10
Total plates =54*10=540
No of Plates in 2nd chamber:
Total Plates = 54*10 =540
Dia of the plates is 0.375 mm.
Length of drying chamber is 1.4m.Length
of ist chamber is 3.77 m and length of 2nd chamber is 4.50 m and
total length of mill is 9.67 m.
In the mid of the mill there is a
static separator which takes the grinded material in which there is a diaphragm
and gives it cyclone . In cyclone separation of fine and course material occurs
due to three forces:
1) Centrifugal
force
2) Drag
force
3) Gravity
Ultra fine material (Minute
Particles) goes to EP in which there is
a high voltage .Efficiency of EP will be greater if there is moisture content
in minute particles EP works like an
electrode(positive and negative terminals) in which inside there are plates.At
the time fine particles start conduction and become behave as charged particles
the fine material stick to these plates which are than hammered constantly and
fine material is got by screws and then
given to airslides to get through in their respective silos.
The course material is recycle to
the ist and 2nd chamber of the mill by ducts to get the respective
fine material.
Air slides has three functions
1) Air 2) Slope 3)Canvass Cloth
The mill is constantly lubricated and to avoid
heating of oil there is a heat exchanger connected and a water line which
constantly control the temperature of oil to about 40 celcius.
RAW PRESS The raw material from the hopper
is brought by 2312 N conveyer belt to the primary crusher . The amount of
laterite slate and raw mix is 130 ton/hr.
From the crusher material is taken
by the bucket elevator to the top and is given to the OSEPA where fine and
course particle are separated . OSEPA gives the respective fine material to the
cyclones then from cyclone material is given to air slides and then material is
collected in silos.
If some problem occurs in OSEPA
and separation is not done then the material is sent to shoot by OSEPA by pass
valve and material is constantly recycled till the OSEPA starts its function
accurately.
PRE-CALCINATION In the PC oxides are removed. The important reaction occurring inside
the PC is heating of CaCo3. which decomposes to give cao and co2.
CaCo3→ CaO+CO2
In PC the material from C2 duck
leaves into C1 drum.
·
Then from C1 drum to C3 duct
·
From C3 duct to C2 drum.
·
From C2 drum to C4 duck
·
From C4 duct to C3 drum.
·
From C3 drum to C5 duck.
·
C5 duct to C4 drum.
·
From C4 drum to PC.
·
From PC to C5 drum.
·
From C5 drum to Kiln.
KILN Length of the kiln is 58.8
m with 3% slope of the total height. The kiln is inclined at 1.58 m. Actual dia
of the kiln is 4.1m. Inside the shell of kiln there are three types of bricks
used to avoid shell of kiln from severe heat.
1) Magnesite
2) High Alumina bricks
3) Low
Alumina bricks
The dia of these brick is 200mm
and hence the effective dia of the kiln is 3.7m.
Basically kiln has no zone but
zones are created on temperature difference.
1) Calcining
zone ( 90% oxide is removed in PC and remaining 10% is removed
in calcining zone)
2) Transition
Zone:- ( In transition zone raw material is converted into paste
)
3) Burning
zone:- ( In burning zone
clinker is formed)
4) Cooling
zone:- ( in cooling zone clinker is allowed to cool )
The speed of kiln is 3.94 rpm
Different chemical reactions
occurred in kiln.
Most of these reactions occurred
in solid phase , but, towards the end of the process the important fusion
occurs.
TriCalcium silicate (3CaO.SiO3)
formatin occurs above 125 celcius which
is the chief strengthening constituent.
REACTIONS
CaSO4→ CaSO4.2H2O
CEMENT MILL AND CEMENT PRESS The operation of cement mill and cement press
is somewhat similar to that of the raw mill and raw press. Clinker from the
silos is taken into the mill and press by respective air slides and bucket.
Again the material is grinded to a fine powder. In press grinding is done by
rollers in which the material is allowed to fall in between the rollers one
roller is fixed and the other is moveable when the material falls between these
roller it grind the material to a fine powder. These roller are adjusted and
shim is introduce between theses roller to avoid collision of the two rollers.
The rollers are lubricated constantly by lubrication point connected to the
rollers at different points.In cement mill and press clinker is grinded to a
fine powder and then gypsum is added to about 5% to increase the water setlling
time of the cement.
PACKING PLANT From cement mill and cement press
the cement is collected into cement silos from where the cement is carried on
conveyer belts to packing plant. In packing plant there are three packing
plants installed where the empty bags of cement are connected to the opening of
the packing machine and the machine sense through sensor when the required
weight of cement is reached in the bag. Then the cement bags are carried by the
belts to the transportation vehicles where they are ready for supply to the
market.
Operational Problems During our stay in cherat cement we come across the following operational problems.
1) After
that the bucket elevator were open and the material is removed from the bucket.
2) Mill
was ist given start by auxiliary motor when mills come to its normal position
then it is given start by main motor.
3) In
the press OSEPA was not separating the material well because in addition to
fine there was some course material. For solving the problem rollers were open
they were chocked were clean and then bring to nirmal position.
4) Moisture
material must be avoided to crusher mill because they can cause the chocking of
material and can decrease the efficiency of the equipment.
5) If
air slides are choked they are hammered if the problem is still not solve then
the canvass cloth in the air slide is changed.
LABORATORY In laboratory different tests are
performed including:
1) to
check the calorific value of coal.
2) To
check the moisture content of coal.
3) After
every single hour composition of slate, laterite etc are checked whether they
are present in required quantity or not..
Three parameters must be remember
1) MA
(Alumina modulus) 1.2-1.7%
2) MS(
Silica Modulus) 2.3-2.7%
3) LSF(Lime
saturation Factor) 0.66-1.02
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| Bestway Cement Farooqia |
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