Loesche Round Table MCL

Operating Experience of the Upgradation of Raw and Coal mill at MCL Alathiyur M. Srinivasan S. Shanmugam

: :

Sr. VP (Mfg.) VP (Mfg.)

Contents  Introduction  Raw Mill LM 38.3 Upgradation with LSKS 57 Classifier and Vortex Rectifier

 Coal Mill LM 20.2D Upgradation with LSKS 36ZD Classifier for Pet coke grinding

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 Conclusion

Introduction  Madras Cement Ltd. (MCL) is a flagship company of RAMCO Group.

ISO 14001:2004

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ISO 9001:2008

IS 18001:2007

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 MCL is having five Cement manufacturing units, three cement grinding units and two packing units with the total annual capacity of 13 Million tones.

MCL Alathiyur plant with two clinkerisation units, is located at Alathiyur in Tamil Nadu, India.

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Introduction

Introduction

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MCL Alathiyur Cement Plant, Tamil Nadu

Introduction

 The cement plant at Alathiyur was setup in two phases.  Line-I was installed with a capacity of 2350 tones/day in 1997 and presently operational at 3500 tones/day.  Line-II was installed with a capacity of 3000 tones/day in 2001 and presently operational at 3500 tones/day.  Line-II was repeat of Line-I with upgraded capacity.

 The products manufactured are Ordinary Portland Cement as per BIS & Sri Lanka Standards (SLS), Portland Pozzolana Cement and Sulfate Resistant Portland Cement (SRPC).

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 Loesche VRM LM 56.2+2C was considered for clinker grinding in Line-II in place of OK mill 33.4 of Line-I

Introduction

Line 1

Line 2

Commissioned (year)

1997

2001

Kiln

FLS – 3500 t/d

FLS - 3500 t/d

Raw Mill

Loesche LM38.3

Loesche LM38.3

Coal Mill

Loesche LM20.2D

Loesche LM20.2D

Clinker Mill

O.K 33.4

Loesche LM 56.2+2 C

 Two coal based captive thermal power plants each 18MW ensure uninterrupted power supply

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Alathiyur Plant Details

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

Introduction: Raw Mill LM 38.3



Technical Details of Raw Mill



Operating data before modifications



Constraints in plant operation



Driving force for the upgradation



Modifications carried out



Classifier Details



Vortex Rectifier



Comparative Opertaing Data



Benifits achieved after upgradation

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Contents: Raw Mill LM38.3

Introduction : Raw Mill LM 38.3

Raw Mill-1 was commissioned with rated capacity of 180t/h @17%R90 µm to cater the kiln of 2350t/d in 1997. Raw Mill-II was commissioned with rated capacity of 215 t/h @ 17%R90 µm to cater the kiln of 3000t/d in 2001. By the time of ordering Line-II, MCL decided to upgrade Line-I to have same capacities. Raw Mill-I was successfully upgraded by replacing classifier from LJKS65 to LSKS52 and bigger tires in 2000/2001.

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Both raw mills were in smooth & stable operation at output of 215-220 t/h @17% R90µm

Technical Details of Raw Mill Type of mill

LM38.3

Rated Capacity (t/h)

215 @ 17% R 90μm

Feed Moisture (%)

Normal: 5

Table diameter (mm)

3800

Grinding rollers

3 Nos.

Main Gear Box

Flender KMP 450

Main Gear box rating (kW)

1320

Classifier Size

LSKS52

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Maximum:10

Constraints in plant operation

The Raw mill was designed for a feed moisture of 5% normal & 10% maximum. Over a period of time, the normal feed moisture increased to more than 10% causing the reduced raw mill output to 205-210 t/h from 215-220 t/h. During monsoon, Mill output was further reducing to 190 t/h. Hot Gas Generator (HGG) had to be operated to get the output of 210 t/h to meet the clinker production. Since more heat was required for drying, the gas volume was to be increased in mill and thereby causing higher product residue.

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Raw Mill motor was overloaded frequently with periodic power kicks.

Constraints in plant operation

 Kiln feed had to be reduced as the Raw mill was unable to support the raw meal requirement.  At high residue of raw meal on 212 µm, problems related to clinker burning resulted in high free lime of >2.5%.  HGG had to be turned on, consuming about 2 t/h of fine coal.  Raw mill with HGG met the raw meal requirement but residue was still high.

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 The raw mill fan was a bottleneck to handle higher gas flow.

Description

Raw Mill 1

Raw Mill 2

Feed Moisture (%)

>=10%

>=10%

Mill Output dry (t/h)

207

210

Product Residue % 212 µm

2.5-3.0

2.5-3.0

Product Residue % 90 µm

19-20

19-20

Mill Motor Power (kW)

1150

1170

Fan Power (kW)

1310

1530

Specific Power: Mill (kWh/t)

5.56

5.57

Specific Power: Fan (kWh/t)

6.32

7.29

Total Specific Power (kWh/t)

11.89

12.86

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Operating data of Raw Mills before modifications

Driving Force for the Upgradation

 MCL decided to further enhance the kiln capacity to 3500 t/d  Accordingly the revised capacity requirement from raw mill was>= 230 t/h to support the upgraded kiln.

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 Product residue @212 µm was required to be less than 2%

Modifications Carried out



Replacing the existing classifier from LSKS 52 by a larger size LSKS 57 with inbuilt Vortex Rectifier. This was the first Vortex rectifier in India.



Modified louver and armor ring to maintain uniform gas flow/velocity profile inside the mill.



Increase the capacity of the raw mill fan by replacement/ retrofitting



Increase the size of the following ducts due to higher gas flow:

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Mill inlet duct Mill Outlet duct Duct from Cyclone to mill fan inlet

Classifier Details

Description

LSKS52

LSKS57

Rotor diameter (mm)

3080

3400

Rotor Height (mm)

2000

2200

Area of rotor (m2)

19.35

23.50

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Comparison between LSKS52 and LSKS57

Classifier Details

Vortex Rectifier

LSKS Loesche India Round Table 2012

LSKS With Vortex Rectifier 18

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Rotor

Vortex Rectifier Vortex Rectifier reduces the turbulences at the mill outlet  Vortex kinetic energy recuperation  Homogenous velocity distribution at mill outlet

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 Uniform/ laminar flow pattern at mill outlet

Vortex Rectifier

Hard twisted gas flow created by high speed rotation of classifier rotor

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With vortex Rectifier Uniform and Laminar Flow

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Without Vortex Rectifier

Vortex Rectifier Flow Characteristics Results of CFD

Classifier with vortex rectifier

Classifier without vortex rectifier Laminar Flow

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Turbulent Flow

Vortex Rectifier

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Actual Photographs during installation at site.

Description

Before Modification

After Modification

LSKS 52

LSKS 57

>=10

>=10

207

231

Product Residue 212 µm (%)

2.5-3.0

1.5-2.0

Product Residue 90 µm (%)

19-20

16-17

Specific Power: Mill (kWh/t)

5.56

4.55

Specific Power : Fan (kWh/t)

6.33

6.28

Total Specific Power (kWh/t)

11.89

10.83

Classifier Size Feed Moisture (%) Mill Output (t/h) dry

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Comparative operating data of Raw Mill 1

Description

Before Modification

After Modification

LSKS 52

LSKS 57

>=10

>=10

210

233

Product Residue 212 µm (%)

2.5-3.0

1.5-2.0

Product Residue 90 µm (%)

19-20

15-16

Specific Power : Mill (kWh/t)

5.57

4.42

Specific Power : Fan (kWh/t)

7.29

6.52

Total Specific Power (kWh/t)

12.86

10.94

Classifier Size Feed Moisture (%) Mill Output (t/h) dry

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Comparative operating data of Raw Mill 2

Comparative operating data

Improvement

Raw Mill 1

Raw Mill 2

11.59

10.95

Product Residue % on 90 µm

3 (Absolute)

4 (Absolute)

Product Residue % on 212µm

1 (Absolute)

1 (Absolute)

Specific Power : Mill Motor (kWh/t)

1.01

1.15

Specific Power : Fan (kWh/t)

0.05

0.77

Total Specific Power (kWh/t)

1.06

1.92

Output (%)

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Performance Improvement

Benefits achieved from upgradation

 At feed moisture >=10% average output increased to >230 t/h at improved residue.  Product Residue on 212 µm, which is crucial for burning came down to 1.52%.  Product Residue on 90 µm came down to 15-16%.  The mill can be operated at 240t/h-245t/h with increased Hot Gas from HGG.  Saving of about 1-2 kWh/t in specific power drawn by mill and fan.

RM-1 :

10.82 kWh/t

RM-2 :

10.94 kWh/t

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 Achieved the lowest specific power consumption (mill + fan)



With improved particle size distribution of mill product, free lime in clinker reduced to =55%



Kiln is being operated to its full capacity due to increased raw meal of better quality



Stable Kiln Operation established

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Benefits achieved from Upgradation

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Introduction: Coal Mill LM 20.2D



Technical Details of coal mill



Difficulties in Pet coke grinding



Solutions for Pet coke Grinding



Modifications carried out



Classifiers



Comparative Operating Data in Pet coke Grinding



Comparative Operating Data in Coal Grinding



Benefits achieved from Upgradation

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Contents : Coal Mill LM 20.2D

Introduction : Coal Mill LM 20.2D

MCL Alathiyur has two Coal mills of LM 20.2D size. The coal mills were designed for lignite grinding with central feed.

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The coal mills were operating smooth & stable, meeting all performance guarantees.

Mill Size

LM 20.2 D

Fuel Type

Lignite / Coal

Feed Moisture (%)

15

Product Rate (t/h)

23 ( wet basis )

Product residue % @90μm

15

Table diameter (mm)

2000

Grinding rollers

2 Nos.

Main Gear Box

Flender KMS 595

Main Gear box rating (kW)

330

Classifier Size

LKS 40ZD

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Technical details of Coal Mill

Difficulties in Pet coke grinding  MCL started using imported Pet coke & coal due to techno-economic reasons.  In Pet coke grinding, the mill operation was very unstable due to non-uniform bed formation  Due to spheroid and uniform shape of Pet coke, the nipping under rollers is extremely difficult.  Due to the low volatile matter in Pet coke, it has to be ground to a fineness of