vertical roller mill
DESCRIPTION
Vertical Roller MillTRANSCRIPT
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Confederation of Indian Industry
VERTICAL
ROLLER MILLS
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Confederation of Indian Industry
Vertical Roller Mills (VRM)
An advancement over ball mill
Roller mill Grinding by Compression
Rollers / Balls on ring
Presently for Raw meal, Coal &
Cement
More Energy efficient
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Confederation of Indian Industry
VRM - Features
VRM Drive - 40% of ball mill
Dry moisture up to 15 %
More compact & Less space
Fan Power consumption - High
Separator - Integral Part of Mill
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Confederation of Indian Industry
Features of VRM
Energy Efficient Grinding System
Mill drive 40% less consumption
Most suited for drying upto 15%
moisture
More compact & occupies less space
More amenable for Controls
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Confederation of Indian Industry
Comparison of Ball Mill & VRM
Ball Mill VRM
Moisture (%) 3.0 7.0 3.0 7.0
Mill Drive (units/ton) 14.0 14.0 6.5 6.5
Fan + separator 1.9 5.0 7.5 7.5
Total 15.9 19.0 14.0 14.0
Ideal choice for high moisture materialIdeal choice for high moisture material
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Confederation of Indian Industry
ENERGY SAVING IN VRMs
Fine tuning of louvres
Mechanical Recirculation system
High efficiency classifier
High Level Control system
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Confederation of Indian Industry
Install Variable Area Louvre Ring
Air flow inside VRM not uniform
Material leaves in a definite pattern
around table
Max. material behind and in front of each
roller
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Confederation of Indian Industry
Install Variable Area Louvre Ring
Uniform area louvre ring
Uniform gas system
Uneven bed of material
Gas prefers path of least resistance
Higher gas flow rates essential
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Confederation of Indian Industry
Install Variable Area Louvre Ring
Variable area louvre ring
Larger area at points of larger
concentration
Gas flow directed to material
Potential open area higher
Lower Pr.Drop and lower gas flow
Reduced fan power consumption
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Confederation of Indian Industry
Install Variable Area Louvre Ring
Presently fixed area louvre ring
Pr.Drop across mill 870MM WG
Flow thro mill 3,40,000 M3 / HR
Mill output 155 TPH
Recommended to install variable area
louvre
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Confederation of Indian Industry
Install Variable Area Louvre Ring
Pr. Drop across mill 820 MM WG
Flow thro mill 3,10,000 M3/HR
Mill output 155 TPH
Annual savings 15000 USD
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Confederation of Indian Industry
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C4 Roller 2 Roller
3 R
olle
r1
Rol
ler
Mot
or
Mill Door
Area 1.132 m2
Velocity 83 MPS
Rejects
RejectsGas
Rejects
RejectsGas
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Confederation of Indian Industry
Fan Power Consumption in VRM
High in comparison to Ball Mill
Major Reason
Higher pressure drop
400 900 mm WG
Higher air flow rates
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Confederation of Indian Industry
Pressure drop in a VRM
Ranges from 400 - 900 mm Wg
Pressure drop
75% - Mill louvre
25% - Housing & classifier
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Confederation of Indian Industry
Why High Pressure Drop ?
High louvre velocity : 55 85 m/sec
Why high louvre velocity ?
Lift particles of higher sizes
Grinding table to separator
Reduction of louvre velocity
Reduction of mill - P
Higher quantity of rejects at mill bottom
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Confederation of Indian Industry
Mechanical Recirculation System
Rejects handled mechanically
Recirculated back to mill through BE
Tremendous reduction in pressure
drop & energy consumption
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Confederation of Indian Industry
Installation of Mechanical Recirculation
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Confederation of Indian Industry
Louvre velocity vs. Mill power
Louvre velocity (m / sec) 75 50 35
Mill P (mm Wg) 900 630 450
Reject rate (% of fled) 0 5 15% 150%
Fan Power (units / ton) 6.9 5.5 4.7
Mill power (units / ton) 6.5 6.6 7.2
Total power 13.4 12.1 12.1*
* Includes power for mechanical recirculation
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Confederation of Indian Industry
Louvre velocity How much reduction possible ?
Air flow through mill depends on
Louvre velocity
Drying requirement
Separator requirement
Reduction of louvre velocity to lower levels
Large material handling equipment
Large mill housing
Leads to pre-separation
Less stability & Table vibration
Optimum louvre velocities with mechanical
recirculation : 45 55 m/sec
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Confederation of Indian Industry
Reduce Recirculation Air in VRM
Recirculation air 60 kM3/Hr
High recirculation air
High velocity At louvres
High P
High power consumption
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Confederation of Indian Industry
Reduce Recirculation Air in VRM
Trial taken
Recirculation reduced by 20 kM3/HR
RPM of class red.
Same residue maintenance
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Confederation of Indian Industry
Reduce Recirculation Air in VRM
R/M Fan power consumption
reduced by 150 kW
Savings- 48000 USD
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Confederation of Indian Industry
Separators for VRMs
I stage - Static separator
II stage - Dynamic
conventional
separator
III stage - High efficiency
separator
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Confederation of Indian Industry
High Efficiency Separators
Air requirement lower
High eff. - 0.6 0.8 kg matl / kg of air
Conv. - 0.4 0.5 kg matl. / kg of air
Better separation efficiency
Lower P across mill
Higher output & lower specific energy
consumption
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High efficiencySeparator
OldSeparator
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Confederation of Indian Industry
Features of high efficiency Separator
Minimum pre-separation in mill
housing
Maximum separation in the
separator
Coarse return drops exactly in the
centre of the table
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Confederation of Indian Industry
Benefits
Increase in output 10 to 30%
Reduction in specific energy
1.5 to 3.5 units/ton
Very attractive financially
Features of high efficiency Separator
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Confederation of Indian Industry
Replacement with High Efficiency Separator (Raw Mill)
Before After
Capacity 250 TPH 290 TPH
Residue (90 ) 11.5% 13.2%
Mill power (units / ton) 4.7 4.1
Fan power (units / ton) 8.5 6.2
Total Power 13.3 10.3
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Confederation of Indian Industry
Effect of Roller to Table Dia
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Confederation of Indian Industry
For the LM 38.4 the ratio
between diameter for roller and
table is 0.45, for the Ube LM 45.4
the ratio is 0.5, whereas for the
LM 56.4 the ratio is 0.40.
Effect of Roller to Table Dia
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Confederation of Indian Industry
LM 38.4 LM 45.4(Ube) LM 56.4
Diameter of Grinding Table 3.80 m 4.50 m 5.60 m
Diameter of Rollers 1.70 m 2.24 m 2.24 m
Width of Rollers 0.67 m 0.85 m 0.85 m
Kwh/ts, Mill 6.31 5.99 7.00
Kwh/ts, Fan 6.23 5.51 7.00
Residue (90/212 microns) 12/0.8 11/0.8 11/0.9
Dust Load (g/cum) 610 630 595
Delta P, Mill 83 56 87
Vibration of Mill 3 - 5 2 - 4 5 - 8
Effect of Roller to Table Dia
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Confederation of Indian Industry
Effect of Operating Pressure
Ube LM 40.4
Grinding Pressure
kN/m2
650 662 675 687 700
Capacity 290 295 300 305 310
Kwh/ts, Mill 9.0 9.0 9.0 9.0 9.0
Vibration 4-5 4-5 4-5 4-5 4- 4.5
Delta P of Mill 54 53.5 53 52.5 52
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Confederation of Indian Industry
Effect of Operating Pressure
10 % increase in Grinding pressure
Capacity increase by 7%
Mill drive SEC no change
Fan power 0.5 kWh / MT reduction
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Confederation of Indian Industry
Influence of Feed Size for an LM 40.4 Raw Mill
Max 90 mm Max 30 mm
Capacity 240 262
Kwh/ts, Mill 8.05 7.41
Delta P, Mill 76 73
Vibration 5 - 7 4 - 6
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Confederation of Indian Industry
High Level Control System for Mills
Conventional Open loop controls
I Generation
P vs Feed controls
Latest control system
Min. 3 to 5% improvement
Production & Energy
More stable operation of VRM
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Confederation of Indian Industry
High Level Control System for Mills
Latest control system
Feed Based on P, Load & Recirculation (B.E)
Mill flow kept constant
Mill Load, P, Recirculation load Fineness predicted
Separator speed varied
Prediction mechanism varied depending
on actual fineness
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Confederation of Indian Industry
BEST RAW MILL VRM SEC
Sl
no
Parameter Plant 1 Plant 2
1 Output, TPH 403 320
2 Mill DP, mm WC 750 740
3 Sep Loading,
g/m3536 495
4 Mill drive SEC,
kW /MT Material
9.25 6.00
5 Mill fan SEC,
kW /MT Material
5.69 6.40
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Confederation of Indian Industry
rotor
Vortex Rectifier
grit cone
Vortex rectifier for classifier
low dp leading to a reduced specific energy
consumption
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Confederation of Indian Industry
Vortex kinetic
energy recuperation
Restores a linear
flow in the ductwork
Vortex rectifier for classifier
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Confederation of Indian Industry
conventional design
high velocity
differences
LDC (new design)
homogeneous velocity
distribution
Install Vortex rectifier for classifier
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Confederation of Indian Industry
To Sum-Up
VRM Developing into an excellent
choice
Raw mill, Coal, Cement & Slag
Further improvement opportunities
Mechanical recirculation
High efficiency separators
High level control system
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Confederation of Indian Industry