The main objective of this presentation is that how to optimize the mill in pet coke grinding and what modification is required when changing from normal coal to pet coke.

1. ATOX(22.5) COAL MILL OPTIMIZATION
FOR PET COKE GRINDING UPTO
RESIDUE 1.2-2% ON 90 MICRON.
BY:-NITIN ASNANI
CERTIFIED ENERGY AUDITOR(BEE-EA28964)

2. PARAMETERS
 Nozzle ring velocity
 Circumferential velocity inside the rotor case
 Mill outlet ratio(gm/m3)
 Dam ring height
 Seal air gap
 Distance between the static vanes of
separator

3. NOZZLE RING VELOCITY
 For pet coke grinding the nozzle ring velocity
should be
greater then 55m/s on the basis of mill inlet flow
for Atox
coal mill.
 For low wear and tear inside the mill
recommended velocity should be in the range
of 55-60m/s.
 Before optimization nozzle ring velocity was 42
m/s but
after nozzle modification the present velocity is
around
60m/s no reject has been observed at this
velocity.

4. CIRCUIMFRENTIAL VELOCITY INSIDE THE ROTOR CASE
 Circumferential velocity inside the rotor case
should be
around 27-30 m/s for pet coke grinding it should be
calculated by this formula as below:-
CV=n*3.14*D/60 m/s
N=separator rpm
D=rotor dia in case(m)
 Presently its around 27m/s and cant be
increased beyond this due to no margin in
separator.

5. DUST CONCENTRATION AT MILL OUTLET
 For fine petcoke grinding and reduce the
load on
separator the mill outlet dust concentration
should be in
the range of 250-300 gm/m3
 Before optimization the ratio was around
170gm/m3
and but after optimization by reducing the fan
flow from
70% TO 65% without affecting the output of the
mill the
outlet dust concentration is 210 gm/m3.

6. DAM RING HEIGHT
In Atox coal mill the dam ring height is
required for pet
coke grinding is around 5-5.5% of table
diameter.
Table diameter(mm)=2250 mm
Before optimization dam ring height was
145mm which
is around 6.4% of table dia but after
optimization the
dam ring height reduced to 110 mm which is
almost 5%
of table dia.

7. SEAL AIR GAP
Seal air gap is the most important parameter
for any
type of grinding weather its petcoke or coal the
seal air
gap should be less then 10mm presently the
seal air gap
of mill is 5-6 mm which is very good.

8. DISTANCE BETWEEN THE STATIC VANES OF SEPARATOR
 The distance between the static vanes of
separator
should be uniform for maintaining the uniform
velocity
profile across the separator as result
centripetal force
which acts on the particle should be uniform.
 Before modification the distance between
static vanes
was uneven but after modification the distance
between
static vanes is 30mm.

9. IMPACT ON RESIDUE
By maintaining all the parameters which have
been
discussed in previous slides the residue of
petcoke
on 90 micron is reduced from 6-7% to 1-1.5%
on 90
micron without investing a single rupee.

10. COMPARISON
BEFORE MODIFICATION
Nozzle velocity-42 m/s
Dam ring height-145 mm
Seal air gap- 5-6mm
Mill outlet dust(gm/m3)-170
Circuimfrential velocity-27m/s
Distance between static vanes-
uneven
AFTER MODIFICATION
Nozzle velocity- 60 m/s
Dam ring height- 120mm
Seal air gap- 6-7mm
Mill outlet dust(gm/m3)- 210
Circuimfrential velocity-27m/s
Distance between static vanes- 30
mm.

11. CONCLUSION
SIDHI CEMENT WORKS
Atox mill After modification Before modification(m/s)
Nozzle ring velocity(m/s) 60 41
fan inlet flow(m3/hr) 107000 120000
dam ring height(mm) 120 mm 145mm
static vanes gap(mm) 30 uneven(35-45 mm)
seal air gap(mm) 6.0-7.00 6.00-7.00
mill outlet dust load(gm/m3) 210 170
residue(90 micron) 1.5-2.0% 8%
fan flow reduce (rpm) 65-68% 71-72%
out put (tph) 18-20 18-20
GRINDING PRESSURE(Bar) 145 145
circuimfrential velocity(m/s) 27-28m/s 27-28m/s
water flow(m3/hr) 2-4 m3/hr 2-4 m3/hr
Nozzle ring area(m2) with gap
between the tables and
nozzles. 0.45
0.96

12. THANK YOU