Loesche Round Table MCL

Operating Experience of the Upgradation of Raw and Coal mill at MCL Alathiyur

M. Srinivasan : Sr. VP (Mfg.)S. Shanmugam : VP (Mfg.)

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2Loesche India Round Table 2012

Contents

Introduction

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

Coal Mill LM 20.2DUpgradation with LSKS 36ZD Classifier for Pet coke grinding

Conclusion

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

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

Introduction

ISO 9001:2008ISO 14001:2004 IS 18001:2007

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Introduction

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

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MCL Alathiyur Cement Plant, Tamil Nadu

Introduction

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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.

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

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

Introduction

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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

Alathiyur Plant Details

Introduction

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Contents: Raw Mill LM38.3

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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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.

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

Introduction : Raw Mill LM 38.3

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Technical Details of Raw Mill

Type of mill LM38.3

Rated Capacity (t/h) 215 @ 17% R 90μm

Feed Moisture (%) Normal: 5 Maximum:10

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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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.

Raw Mill motor was overloaded frequently with periodic power kicks.


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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.

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

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Operating data of Raw Mills before modifications

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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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.

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

Driving Force for the Upgradation

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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:

Mill inlet ductMill Outlet ductDuct from Cyclone to mill fan inlet

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Comparison between LSKS52 and LSKS57

Description LSKS52 LSKS57

Rotor diameter (mm) 3080 3400

Rotor Height (mm) 2000 2200

Area of rotor (m2) 19.35 23.50

Classifier Details

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Classifier Details

Vortex Rectifier

LSKS With Vortex RectifierLSKS

Rotor

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Vortex RectifierVortex Rectifier reduces the turbulences at the mill outlet

Vortex kinetic energy recuperation

Homogenous velocity distribution at mill outlet

Uniform/ laminar flow pattern at mill outlet

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Vortex Rectifier

With vortex RectifierUniform and Laminar Flow

Without Vortex Rectifier

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

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Classifier without vortex rectifier

Classifier with vortex rectifier

Laminar Flow

Turbulent Flow

Results of CFD

Flow Characteristics

Vortex Rectifier

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Vortex Rectifier

Actual Photographs during installation at site.

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Comparative operating data of Raw Mill 1

Description Before Modification After Modification

Classifier Size LSKS 52 LSKS 57

Feed Moisture (%) >=10 >=10

Mill Output (t/h) dry 207 231

Product Residue 212 µm (%) 2.5-3.0 1.5-2.0

Product Residue 90 µm (%) 19-20 16-17


Specific Power : Fan (kWh/t) 6.33 6.28


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Comparative operating data of Raw Mill 2


Classifier Size LSKS 52 LSKS 57

Feed Moisture (%) >=10 >=10

Mill Output (t/h) dry 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



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Improvement Raw Mill 1 Raw Mill 2Output (%) 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



Performance Improvement

Comparative operating data

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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 1.5-2%.

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.

Achieved the lowest specific power consumption (mill + fan) RM-1 : 10.82 kWh/t

RM-2 : 10.94 kWh/t

Benefits achieved from upgradation

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With improved particle size distribution of mill product, free lime in clinker reduced to <2%

Quality of clinker improved : C3S >=55%

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

Stable Kiln Operation established

Benefits achieved from Upgradation

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Contents : Coal Mill LM 20.2D

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


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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.

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

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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

Technical details of Coal Mill

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Difficulties in Pet coke grinding

MCL started using imported Pet coke & coal due to techno-economicreasons.

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 <2% Residue on 90µm for complete combustion.

The existing LKS Classifier was not able to provide efficient separation for the very fine grinding of Pet coke. The fines along with grits returning on the table leads to over grinding and unstable bed formation.

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Solutions for Pet coke Grinding

The stability of mill could be achieved/improved by:

An efficient and state of art classifier, designed suitably for very fine grinding, minimizes the fines in return grits.

Due to reduced fines in return grits, the over grinding is avoided and stable/uniform bed formation is ensured.

Additionally the bed stability can be influenced by:

Increasing dam ring height

Water sprinkling on table

Reducing table speed (varying mill motor speed)

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Modifications Carried out

Replacing the existing classifier from LKS 40ZD by LSKS 36ZD

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

Modified dam ring suitable for Pet coke grinding

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Classifiers: LKS...ZD and LSKS...ZD Type

LKS Classifier New LSKS Classifier

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Classifier Size LKS 40 ZD LSKS 36 ZD

Output (dry basis) (t/h) 13 17

Product Residue @ 90 µm (%) 4 1.5 -2


Fan Power in GRR Mode (kW) 420 450


Specific power: Fan (kWh/t) 32.30 26.47


Comparative Operating Data in Pet coke Grinding

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Classifier Size LKS 40 ZD LSKS 36 ZD

Output (dry basis) (t/h) 23 28

Product Residue @ 90 µm (%) 18 <16


Fan Power in GRR Mode (kW) 440 475


Specific Power: Fan (kWh/t) 19.13 16.96


Comparative Operating Data in Coal Grinding

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Improvement Coal Pet coke

Mill Output dry basis (%) 21.73 30.76

Product Residue % 90µm 2 (Absolute) 2 (Absolute)

Specific Power (kWh/t) Mill + Fan

6.13 13.88

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Pet Coke usage increased up to 85%

Improved mill stability ; especially in Pet Coke grinding

Mill Vibration reduced to <2mm/sec

Improved burning efficiency in kiln due to homogenous quality of pulverized fuel

Abnormal coatings in Kiln eliminated

Kiln is being operated to its full upgraded capacity

Reduced running hours of coal mill and it’s increased availability for maintenance etc.

Benefits achieved from upgradation

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Conclusion

The performance of upgraded raw mill and coal mill met the expectation of MCL to cater the enhanced kiln capacity at improved clinker quality.

With significant saving in specific power of grinding sections, MCL achieved specific power consumption of 63-64 kWh/t in PPC for complete plant, which is the benchmark in the industry.

The series of national awards for the highest energy efficient plant bears a testimony of innovative commitment by MCL.

MCL would like to put on record the appreciation for continuous support given by OEM such as Loesche to meet the target.

MCL firmly believes in continual improvement and is working together with Loesche to further reduce specific power ; especially in clinker grinding with similar Upgradation philosophy.

THANK YOU

Documents

Loesche Round Table MCL