Vertical Roller Mill more detail inside function

Explain VRM

1. Contents

* Mill Overview

+ Mill Internals

» Concept of Nitrogen

* Water lance installation procedure
* Roller Calibration

* How to check buffer?

* Hydraulic System Working

» Wear measurement methodology
* Process Audit

* Mechanical Audit

* Gear Box Overview

* VRM Heat Balance

4. Bearing Cartridge

Vortex Rectifier

Optimized Guide Vane
Enlarged Classifying Gap
Chute inside the Grit Cone
Consequent Velocity Increase

Grit Cone Extension

7. Mill Internals

* Scatter Ring

* Dam Ring

* Louvres

* Armour Ring
* Water Lances

8. SCATTER RING

1) The main function of the scatter ring is to ensure the reject material should go into the louvre ring to
minimize the impact of wear on a table surface

2) Secondly to avoid air bypassing and ensure uniform gas flow through a louvre

3) Distance betweenlaxial gap) the louvres & scatter ring is to be maintained 10mm as the former is
dynamic & later is static part respectively

Physical Inspection Methdology

1) Measure the height & width then check with standard drawings for any deviation
2} Measure the axial gap between louvres & scatter ring as per standard norms(10mm)
3) During the audit, the following measurements have been found

9. Scatter Ring

10. DAM RING

1) The main function of dam ring is to form the stable grinding bed during mill
operation with water spray

2) The total dam ring is the sum of support ring ,inner dam ring & outer dam ring
TD = SR+ID+OD
TD 110+140+150
TD = 400 mm
Physical Inspection

1) Measure the heights & widths then check with standard drawings for any deviation
2) During the audit, the following measurements have been found

Dimensions Unit Support Ring Inner Dam Ring | Outer Dam Ring
Height mm 110 140 150
Width mm 80 80 25

11. DAM RING

12. Support
ring

13. LOUVRE & AMOUR RING

1) Minimum gas velocity is required to lift the particle through louvres that is called
nozzle ring velocity and it depends upon the total opening area of louvers

Nozzle ring velocity = Mill Inlet Volumetric flow(m?/hr)
Total louvres area(m?)
Nozzle Ring Velocity = 40 m/s

2) The main function of amour ring is to guide the flow to ensure minimum pressure
drop across louvres

Armour ring angle
Louvre ring angle

8-11° with respect to vertical
60-65 * with respect to horizontal

1

15. How to Calculate Louvre Areas

Area=LXW

17. WATER LANCE POSITION

O Water spray plays an important role to form the stable bed while the clinker mill
is in operation and benefits to reduce the mill vibration during operation

O Therefore, water lance position plays a critical role and should be positioned
inside the mill as per standard drawings & protocols

U To ensure proper water spray ‚the compressed air supply should be checked
physically otherwise jamming will take place inside the slots

O Recommended Dimension

LS- Distance from Inner Dam Ring -Support Ring Width +20mm.

LM-Distance from Table:-Damring height+50mm

Angle of Inclination:-35 degree

O Perpendicular distance of water lance from roller should be greater than 50mm

18. Water Lance Position

21. BLADDER & PISTON ACCUMULATOR —Nitrogen Pressure

O Bladder Accumulator

+ The main purpose of bladder accumulator is to provide continuous oil flow to the piston cylinder through
hydraulic system via ail tank and generates the working pressure in the mill to dawn the rollers on table

* Italso act as a shock absorber
Ni Pressure Concept

* Nitrogen pressure inside the bladder accumulator depends upon the maximum working pressure which is
required while grinding

* Working Pressure - 4 X Nitrogen pressure
. fores :-40 ‚bar pressure is required for generating 160 bar working pressure otherwise bladder accumulator may
jamaget

O Piston Accumulator
* The main function of piston accumulator is to provide continuous ail flow to the piston cylinder through hydraulic
system & generates counter pressure in the mill to lift the rollers

+ For lifting:-
* Maximum ail flow inside the cylinder to counter the working pressure

22. Bladder Accumulator

23. Piston Accumulator

Lo EEEIELESS ENTS EFSELIELITS “==

N

\

Vila

N

on AP LELEIE TES TES ARI DER DI Dre

24. Working & Counter Pressure Range

* Minimum Working Pressure = Nitrogen pressure X 1.25 + 5%
For example:- = 40X1.25+5%

= 52.5 Bar
* Maximum working Pressure = Nitrogen Pressure X 4

= 40X4

= 160 Bar

* Minimum Counter Pressure

* Maximum Counter Pressure
Key

owt Spring stiffness of the roller
pt Charging pressure of the hydraulic accumulator
p2 Operating pressure

A Operating ranger

Please note: Pimas © 0.8 * Pain Pin = 0.25 * Pamax

25. Fig. 25: Sora assembly cot

Kay
Y Rocker arm 5 Hytemuke supply (Por 3 cabinets, depends on
2 Hydra cylinder ber ef rebar}

3 Paton accumutaser © Biacer acxumuiator

4 Pesines 7 Poses

28122071 Leiche Presentation

28. VIEW FROM MOTOR
[SIDE - LEFT SIDE Le.
FIXED BEARING SIDE

Nitrogen Pressure Status-S Roller

| BLADDER ACCUMULATER NO.
(FROM RIGHT TO LEFT)

PISTON ACCUMULATER NO.

29. Hydraulic System Working-M Roller

obs eet,
de

30. Hydraulic System Working-M Roller

Pum Pum

Condition pi
(2.4)

Mill in
Operation
op |
OP
Raising
Rollers
Keep rollers
in top posi.

Lowering
rollers

31. Roller Lubrication System Working

32. Roller Lubrication System Working

1) There are two pumps in the roller lubrication system one is suction, and another is
pressure pump respectively

Function of Pumps

Pressure Pump: -The main function of this pump is to deliver oil continuously to the
roller from an oil tank

Suction Pump: -It is mainly used to draw oil from the roller and put it back into the oil
tank,(Case 2) if the oil level in the roller drop below a certain level then the suction
pump will draw air and form a bubble in the sight glass which indicates the insufficient
level of oil in the roller

If everything is OK, then the suction pump will only follow case 1

33. Roller Calibration & Buffer Position
Methodology

1) First take 20 mm plate and then place it below roller centre towards backside position as per image
shown as below

34. Roller Calibration & Buffer Position
Methodology

2) Then down the roller and note the readings of grinding bed thickness which comes either in PLC or
OCS, whatever reading comes but insert the value of 20mm against the original value

3) Again repeat the above procedure for 90mm plate and finally check the calibration by putting any
thickness of plate which should be above 20mm, generally 40mm,S0mm,60mm plates are used for roller
calibration

4) Finally note down the readings by placing above plates below roller and correspond for that check the
readings which are coming in OCS if the deviation is only 4mm to Smm then it's OK otherwise again
repeat the entire procedure

35. Roller Calibration & Buffer Position of Rollers

Buffer position

In Clinker & coal mills some gap is given between roller and table to avoid gearbox damage as we know that clinker is
fine therefore it’s difficult to make a proper bed for grinding while in the case of coal mills the coal is explosive
therefore to reduce the possibility of spark the buffer is provided in coal mills.

How to check ?

Placing the light on a mill table in such a way that the light & camera both are opposite to each other across the roller
position as shown in the image as below, if one can see the light on the opposite side it means there is a gap between
roller & table else it touches the table surface.

36. Parallelism of Rollers/Distance from support Ring
Methodology

To check whether the rollers are parallel with a table or not & Secondly, whether it should be
positioned in the correct position or not, the following procedure is carried out are as below: -

1) Firstly, place the roller on any of the plates of thickness between 20 mm to 150mm at the
backside of the roller (bigger diameter), and generally, it should be kept in the range from
40mm to 60 mm for the PPC grinding

2) Then by hit & trial method put the stick of any size at the front side of big roller diameter and
measure it with help of inch tape if the value matches with actual grinding plate thickness that
means rollers are parallel else again repeat the procedure to find the correct position

—

pou on ie

37. Parallelism of Rollers/Distance from support Ring
Methodology

3) After doing the parallelism activity, measure the distance from the support ring to the
centre of the roller which should be at least greater than 5mm & less than 20mm for making
grinding effective, also check from the left & right side of the rollers respectively to its centre

4) Also check the distance between the inner dam ring & centre of the roller to know the wear
rate of the roller

38. Wear Measurement

39. Roller Tires Profile

40. Roller Tires Profile

41. How to Check Tires Profile?

42. R3-Clearance

43. How To Check Material Distribution

44. Separator Inspection

DAnnual Classifying Gap

ÜDistance between the static Vanes
OSeal Air Gap

ODimensions of Static vanes

O Dimensions of Dynamic Vanes
ODistance of Grit Cone from table

45. Separator Overview

46. Annual Classifying Gap
7

47. el

STATIC VANES GAP

48. STATIC VANES WIDTH

49. GRIT CONE DISTANCE

50. How to take Seal Air Gap ?

51. Mill Optimization

+ Separator Loading(gm/m?)

+ Nozzle ring Velocity(m/s)

+ Rotor Cage Velocity(m/s) = Rotor diameter X Height x3.14=Area
> Circumferential Velocity(m/s) = N X 3.14 X D/60

+ Dam ring height(mm)

> Water Spray pattern, flow & nozzle condition

> Weigh Feeder Calibration by Drop test

+ Grinding Pressure(Working & Counter)

> Mill Outlet temperature(*C)

Mill Inlet pressure(mbar)

> Nitrogen pressure in bladder & piston accumulator(bar)

52. Mill Optimization

>» System resistance(Pressure drop profiling)
False air infiltration

Rollers Condition(wear rate)

>Table Liner Condition(wear rate)

Static Vanes condition

+ Dynamic Vanes Condition

Seal Air Gap(mm)

+ Main drive load(kW)

> Mill vibration(mm/s) & grinding layer thickness(mm)
+Fan Efficiency

+ Roller position(Distance from Support ring)

53. Separator loading(gm/m?)

> It is mainly defined amount of air is required to handle the material for

separation
> High dust loading is mainly helps to achieve good residue with desired

output

Coal Mill Coal Mill
5 E il A
Unit | Clinker Mill Raw Mill (Normal) {Pet Coke)

gm/m? 300-315 600-650 300-350 200-220

54. Nozzle Ring Velocity(m/s)

+ Minimum amount of velocity is required to lift the material in such a way
that reject should be come minimum from the mill.

> As nozzle velocity increases the pressure drop across the nozzle also
increases therefore its very important to operate the mill with optimum
nozzle ring velocity.

Coal Mill Coal Mill
(Normal) (Pet Coke)

m/s 40-45 45-60 60 60

Unit | Clinker Mill | Raw Mill

55. Impact of Nozzle Ring Velocity(m/s)
Generally, louvres area and nozzle ring velocity is to be decided upon
the dust loading of the mill

Louvres are blocked behind the rollers in case of clinker and raw mill

respectively to protect the bell housing of the roller and minimizing the
wear rate

EA
70-80 Trace 100
45-60 5-10% 84
40-45 20-30% 60

56. Nozzle Ring Velocity Calculations & Amour Ring

Nozzle ring velocity = Mill Inlet Volumetric flow(m?/hr)
Total louvres area(m?)

Area m?

Flow = m?/hr,

57. VRM HEAT BALANCE

58. CONCEPT OF ENERGY BALANCE

Dmmmmmmmmmmmmmmnmmncemmemmmcmcm nnnn

59. OVERALL MASS BALANCE

INPUT(Kg/kg material) Output(kg/kg material)
FEED with moisture Mill outlet gases including water vapor
Recirculation gases Product
| Hot flue gases from HAG
| Water Spray
False air

60. OVERALL ENERGY BALANCE

INPUT(kcal/hr) Output(kcal/hr)

Sensible heat from Raw material | Sensible heat of outlet Gases

Sensible heat from Recirculation gases | Sensible heat of product

‘Sensible heat of Hot flue gases from

HAG | Latent heat of Vaporization of water

Sensible heat from Water Spray Sensible heat of water

Sensible heat from False air |

Heat from main drive

61. INPUT(kcal/hr)

1) Sensible heat from HAG
Temperature difference
Reference temp

2) Sensible heat from recirculation

3) Sensible heat from water
4) Sensible heat from feed

5) Sensible heat from moisture
6) Sensible heat from false air

X * Cp*Temperature difference-----Eql
Gas temp- reference temp

ambient temperature
X*Cp*(T2-ambient temp)

Y *Cp*Temperature difference
Y *Cp*(T1-ambient temp)-———- Eq2

Water spray rate * CP Water *(Temp differ)---Eq3

Feed rate *CP feed*(Temp diff).

Moisture * CP * temp differenc:
FA rate *CP *Temp difference

62. A
P
G
1) Sensible heat from Product

2) Sensible heat from hot gases

3) Latent heat of Vaporization
4) Sensible heat of water

5) Sensible heat from moisture

OUTPUT(kcal/hr)

P +6

Product(kg/hr)

Mill O/L Gas flow rate

P* Cp*Temperature difference-----------Eq7

G *Cp*Temperature difference

G *Cp*(T3-ambient temp]... EB
Water rate *latent heat of Vaporization......Eq9

Water rate * Cp water*(100-input water temp)..10

Moisture * Cp * Temp difference...........o.Eq11

63. INPUT = OUTPUT

Eq1+Eq2+Eq3+Eq4+Eq5+Eq6 = Eq7+Eq8+Eq9+Eq10+Eq11

From the above equation the value of X can be evaluated
x = Input value of fuel from HAG

64. VRM Operation Concept
OTo Increase Grinding Pressure
+ Product residue will decrease
> Mill internal recirculation will decrease as a result mill DP |
> Main drive load will increase
OTo Decrease Grinding Pressure
> Mill DP will increase
> Mill reject will increase
> Residue quality will decrease
> Mill will not run at design output

65. VRM Operation Concept
OTo Increase Dam Ring Height
> Mill load will increase
> Mill reject will decrease
> Mill vibration will be reduced
+ Output may be decreased
OTo Decrease Dam Ring Height
+ Mill reject will increase
> Mill vibration will increase
> Mill load will decrease

66. VRM Operation Concept
OMaterial bed height
> Material bed height depends upon the feed material characteristics

>In case of high bulk density of material, the overall bed height will
increase as compared to low density

>Grindability factor is also important to decide the overall bed height of
the material

+C35 À it means for the same model of clinker mill will give the higher
output and overall bed height is on the lower side

+ New table liners as well as rollers are having higher bed height due to
improper profile.

67. VRM Operation Concept
OMaterial temperature & Mill O/L Temp.

> Mill outlet temperature should be greater than dew point temperature
by 20 degree C

> Feed material temperature in case of clinker mill should not be greater
than 120 degree C

> If mill outlet temperature is running on higher side as compared to mill
inlet it means material temperature is on higher side

> Higher mill inlet temperature leads to increase the tendency of mill
vibration due to bed destabilization (Fluidization of bed)

68. VRM Operation Concept

OMill Inlet Draft, Recirculation Damper & Water Spray

+ Mill inlet draft should be maintained in between (-20mmwg to -50Ommwg) to
minimize the fan inlet static pressure as well as for safety of the duct.

> Recirculation volume damper should be maintained in the range of (70% to 95%) to
reduce san load on the fan as well as to maintain the minimum recirculation volume
in the mil

> Water spray mainly dspande upon the mill vibration and to form the stable bed
during mill operation ‚high water spray in clinker mill may form the coating at

support ring which ultimately leads to mill vibration.

> Water spray pattern plays an important role in clinker as well as coal mill (Petcoke)
grinding

¥ If the feed moisture(>2.5%) in raw mill is on the higher side, then its not necessary
to run the water spray

69. Clinker Grindability

Table 2. Relationship between Clinker Grindability Ranking and Crystal Size and Content.

easiest

Ranking Value is Relative on a Scale of 1 to 4; 1 being Easy to Grind, and 4 being
Difficult to Grind

70. GEAR BOX OVERVIEW
OGear Box Lubrication System Working
QWibration measurement Points & sensor position in Gear Box
OGearbox Components

72. RENK GEAR BOX SENSOR POSITION

= il =i
en) 0 |
co

73. SENSOR POSITION DETAILS

Sensorl
Sensor2
Sensor 12

Sensor 13

Sensor 14

Sensor 15

Sensor 16

Speed Sensor

Torque Sensor
Oil Particle
Counter

Oil Condition
Sensor
Displacement
Sensor

Displacement
Sensor

Displacement

Sensor

77. SENSOR NO 4
TT

78. SENSOR POSITION NO 5

The acceleration sensor number 5 is
mounted radially inside the gearbox on
the bearing seat of the lower bearing of
the bevel wheel.

Fig. 22: Postion of Acceleration Senses 5

79. SENSOR NO 6

he acceleration sensor number 6 is
mounted radially inside the gearbox on
he bearing seat of the upper bearing of
he bevel wheel.

80. SENSOR NO 7

The acceleration sensor number 7 is
mounted radially inside at the ring gear
of the 1 st planetary stage on the rear
side of the gearbox.

81. SENSOR NO 8

The acceleration sensor number 8 is
mounted radially inside at the ring gear of
the 2nd planetary stage on the rear side of
the gearbox

Fig. 26: Position of Acceleration Senso &

82. SPEED SENSOR

83. DISPLACEMENT SENSOR

84. GB BASE PLATE VIBRATION MEASUREMENT

85. INPUT SHAFT VIBRATION-HORIZONTAL & VERTICAL

86. THRUST PAD VIBRATION

90. SPECIFICATION OF THE GEAR BOX MODEL

KMPS-396

Distance between Ihe centre
of sun gear & P.C.D. of inner
toothed ring gear.

Helical

Planetary

a Application (Vertical Mill)

Kegel (Bevel)

96. H.PLubrication line

98. il Il

m ngs À

110. es Le à

113. Body Vibration -3 to 6 mmis -Acceptable
Gear Box Input Shaft-:-<Smmi/s & 1.5 -3 mm/s

114. Mill circulation Factor Vs specific Roller Pressure

Circulation factor

115. Pressure distribution along Width of roller

Paak prossura/Avorago prossure
SRE
an

00 3 a

40 80
% Roller Width
Fig. SPressure distribution along the width of the roller

116. Effect of increased Grinding Pressure

ESA
3 >
a 40 L
3
E a
E] E
i Jm mk
/ L
5 2
5 Z KT= 1000 Attn? s
2 10 2 A Te SES Me a
= £ LS atte
Ë o# — — ‘es
o 20 40 60 80 100

% Roller Width

Fig. 7Peak pressures relative to specific roller pressures in a press W/D = 0.26
grinding cement clinker

117. Liners Design

UCasting design and tolerances. Hub conditions , clamps condition etc.

UrFeed Condition , Quartz in the Feed , Hardness of the feed, Moisture
Contents etc.

O Application : Different design for Raw , coal and Limestone Grinding.
U Operating and Performance Parameters.

U Mill internal conditions like Dam ring , whether reject handling system
and classifier design,

CL) In case of fine Grinding , the Casting design, Required Blaine , Residue
etc

118. Types of Wear & their implications

ABRASION — Presenceof
a * Quart

* Pyrites

+ Stone

CORROSION Presence of
ie] + Water contents

IMPACT + Due to Mill design
M + Metal to Metal contact

+ Hard foreign particles in
the feed

© Improve the Hardness
= Best Solution in casting made of Ceramic

© Any alloy with the Cr contents of >25 %

* Provide Cushioning effect with the design
« Solution with Soft Core and Very Hard
* Grinding face. AIAE Inserted Solution is the one

119. Feed Characteristics

Coal 40-120
Limestone 200
Clinker 700 120-150
Slag 300 160-180
Steal Stag 1100 200
Silica/Quariz 1800-1900 > 200
Pyrites 1500 120
EEES |
Allay Hardiness [ H Lite in Hours
Man Ste
Cr Mo Steal
Martansitic Stel 1000-1500
Ni Hard IV 2000-2500
Hi Cr In 400-700 2500-3000
Hard Facing 650750 3000-3500
Ceramic / Sinter cast 2100 10000-+2000

120. Coal

Mill Safety Interlocks

parameter

volatile matter content

fgnition temperature

limiting oxygen concentration

lower explosive limit carbon
jonoxide

low volatile
bituminous
coal, semi-
anthracite &

high volatile
bituminous coal &
medium volatile

lignite & high
unit volatile
bituminous coal |

| bituminous coal anthracite

pet coke

comment

=109,000ppm

121. Safety Points

olatile matter % >40 19-40 | 0-19 |Petcoke Comment
1) Mill inlet temperature should not exceed 2/3 of ignition
temperature;

aximum millintet | mc) | 255 | 305 | 350 | 350 L2)tor pet coke and coals with low volatile matter itis

concentration

estricted to 350°C because of maximum temperature of
steel used in ducts and LoMa

the limiting oxygen conce
including margir

ybrid mixtures of combustible compounds in different

ggregate conditions (carbon monoxide & coal dust)

pically reduce the lower explosive limit of the gas
component down to 20%

122. 5
I
=
E)
a
E
o
5
=
$
>
a
a.

123. > 063 oes | oer

5 20 25 30
Dry bulb temperature “C

B

Specific humidity (w) grams moisture / kilogram dry air

125. tes erty _— 5 ms mms E — 5 e ms
— ED

man mt CO} A UK 43

es 10) —
moisture content = 0.022 kaka
dew point temperature = 27.°C y
wet bulb temperature = 30. °C
volume = 0.99 mg ee

enthalpy = 96. kJ/kg 70
60

so

ES 40

10

o 10 20 E

temperature (°C)

0.80 0.85 0.90 0.95
volume (m*/kg dry air)

126. BAROMETRIC PRESSURE:
101.325 kPa
0 - 914 mt (0 - 3000 ft)

127. THANK YOU
Nitin Asnani
CEA-28964
8963965157

128. Dip tube failure in
5 th stage cyclone

129. QATAR NATIONAL CEMENT COMPANY

Cem

t Rotary Kiln

Questions & Answers

By: Nael Shabana
[email protected]
2013

130. » TYA 4

ATOX(22.5) COAL Mild OPTIMIZATION
FOR PET COKE(GRINDING UPTO
RESIDUE 1,2-27 ON 90 MICRON.

BY:-NITIN ASNANI
TIFIED ENERGY AUDITOR(BEE-EA28964)

131. GRINDING SYSTEM ANALYSIS 8 ITS EFFECT ON POWER CONSUMPTION.

Project Report on
“ANALYSIS OF VARIOUS GRINDING SYSTEMS WITH
RESPECT TO POWER CONSUMPTION KEEPING SAME
QUALITY PARAMETERS”

MM ZG628T: Dissertation

By
Karan Walla
2014HT79520
Dissertation work carried out at

o. COLLEAGUES

Colleagues Consultants Pvt. Ltd., Gurgaon

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE
PILANI (RAJASTHAN)

November 2016

132. Optimisation Of heat

cone

133. © Confederation of Indian Industry

134. D

Rotary Kiln

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