housing is preassembled on the ground along with the classifier, before being lifted into place.

The fly ash feeding system (see Figure 6) conveys design feeds dry fly ash directly to the classifier as part of the fly ash already has product fineness and does not need to be ground. Due to that, the capacity of the mill is increased. In the two Indian grinding stations, the fly ash is fed to the machine via two air slides. However, other setups allow for at least four inlets giving a more even distribution of the fly ash over the circumference of the classifier. SummaryLoesche received the order for the two grinding systems in April 2007 and the FOB delivery was in November 2008. Erection started in December 2008 and commissioning commenced in December 2009 with the first feed in February 2010. By April 2010, 250tph of PPC had been reached and in September 2010 further optimisation was done leading to a stable mill operation without any water injection for grinding bed stabilisation.

As a result no hot gas generator was required. The specific power consumption achieved was 5kWh lower than expected. That was in part due to the easier-to-grind clinker and fly ash compared to the assumed values, both of which had an impact on the grindability of the feed mix and the related specific energy consumption. ______________________________ I

OPTIMISED GRINDING

JUNE 2011 INTERNATIONAL CEMENT REVIEW

Figure 7: Nalagarh grinding plant

Figure 6: gypsum and fly ash feed system to the mill

LOESCHE Mill Type LM 56.3+3, Nalagarh, India

Loesche GmbHHansaallee 24340549 DüsseldorfTel. +49 - 211 - 53 53 - 0Fax +49 - 211 - 53 53 - 500E-Mail: loesche@loesche.dewww.loesche.com

OPTIMISED GRINDINGOPTIMISED GRINDING

To creaTe The world’s finesT engineering we are prepared To Think like no one ThoughT before

Now it’s time for our grinding technology. For further information please call +49 211 53 53 0 or visit www.loesche.com

AZ_A4_Hoch_2011_engineering_RZ.indd 1 27.07.11 13:49

Standalone Vertical Roller Mills without Hot Gas Generator

LOE11034_Advertorial_Print_ICR_6Seiter.indd 1 28.07.11 16:00

INTERNATIONAL CEMENT REVIEW JUNE 2011

OPTIMISED GRINDING

For vertical roller mills (VRM), water injection on the grinding table is a common way to stabilise the grinding

bed and gives a smoother mill operation with lower vibration levels. However, there are some drawbacks to water use in a VRM. The feed moisture for OPC is commonly very low and in case water is added to the grinding process it has to be evaporated requiring thermal energy. If cooler exhaust gases are available in a cement plant this will not pose a major problem, but for a standalone grinding this source of hot gases is not available to drive-off any additional water. In this case a hot gas generator is needed to dry the material and to provide sufficient energy for the grinding system. This solution not only wastes fuel, it also creates further expenses.

In some parts of the world the cement industry is not permitted to utilise water or its use is limited. Loesche has been working on a system that can provide grinding without the need for any water injection. Even if some water is available the main aim is a grinding system that can be run without the need for permanent operation of a hot gas generator.

VRMsA vertical roller mill can process many materials such as clinker, slag, gypsum, fly ash or limestone to produce various cement types of various finesse. The mill is part of a process that begins at the quarry. Only after the initial material has been through the raw material grinding, preheater, kiln and the cooler it reaches the finish mill where additives are added and the final product is obtained. Both Loesche and its customers are essentially concerned with this final product and its properties which are influenced by all stages of the cement making process.

Material enters the VRM via a rotary feeder that poses as an air lock (see Figure 1), then moves down the feed chute to

what is the centre of the rotating grinding table. The product is then driven outwards by centrifugal forces, underneath the rollers where the grinding takes place. Ground material moves over the dam ring and goes up with the gas flow to the classifier. The material has either reached the required fineness and leaves the mill towards the bag filter or is sent back for further grinding, via the grid cone onto

the grinding table. Lumps, which escape the rollers and are too heavy to rise with the gas flow drop through the louvre ring to a reject system and are then fed back via the reject system.

Raw mills or coal mills operate using the same size of rollers. What is particular for Loesche cement mills is the 2+2 or 3+3 system, which features a combination of different sizes of rollers. In cement

Water and energy are precious resources and without them life would not be as we know it today. Both commodities will become more expensive and scarcer in the future. Consequently, saving energy and water is essential for ecologically- and economically-viable production, particularly in the cement industry.

by Dr Daniel Strohmeyer, Loesche GmbH, Germany

IStandalone VRMs without HGG

Figure 1: Loesche vertical roller mill for cement grinding – material flow, feed materials and products

Figure 2: grinding plant flowsheet

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

ash and gypsum (up to five per cent) all of which have different physical properties basically leading to different grindabilities and a particular individual behaviour inside the mill.

Standard procedure is to carry out a grinding test to establish a proper sizing for the mill and the gear box. However, at the start of both of the projects it was not known where the different fly

ash or clinker sources would be sourced. Therefore, Loesche had to assume a certain ‘grindability factor‘ and specific power consumption for the feed mix (see Figure 3). The assumptions were based on Loesche’s experience and knowledge of other fly ash cement grinding plants operating in India. Loesche concluded that it would need a 56.3+3 mill with a table diameter of 5.6m. The selected Flender gear box would have a power consumption of 5400kW, a Loesche dynamic classifier LSKS 102CS and a fan motor of 3000kW would form the other main parts of the system (see Table 1).

Loesche’s scope of supply for the two Indian projects was not for the whole grinding plants, but for the mills, classifiers, sampling stations and the air slides for the product transport. Loesche’s product targets were PPC of 4000Blaine at 250tph using a specific power consumption of 30.75kWh/t for all the Loesche equipment and the fan supply (see Table 2).

The PPC product would consist of 60 per cent clinker, five per cent gypsum and 35 per cent fly ash (2500 Blaine). If the plant receives clinker that is high in C3S then the fly ash content can be increased to the maximum permissible according to Indian standards. If the clinker exhibits a low C3S value, the plant can increase the clinker content and reduce the amount of fly ash to obtain the same required cement strength development.

Construction of the mill foundation and the base frame. This is followed by the erection of the pedestals, which are a critical part of the construction phase as correct alignment is essential. The mill gear box is mounted by applying an orange ‘Chockfast’ (see Figure 4) which provides good connection of the gear box base plate and the foundation. The mill

OPTIMISED GRINDING

Figure 5: height of Loesche LM 56.3+3 when installed

Figure 4: erection of gear box

PPC capacity (tph) 250 Gearbox power (kW) 5400 (Flender) Classifier LSKS 102 CS (kW) 560 Fan motor power (kW) 3000 Mill diameter (m) 13.5Height (m) 20 Grinding table diameter (m) 5.6 Grinding table weight (t) 109Master roller (mm) 3 x2450Support roller (mm) 3 x 1600

Table 1: key data for Dadri and Nalagarh grinding stations

Dadri PPC LM 56.3+3 Guarantee Achieved Mill throughput (tph) 250 253Fineness 4000 3920Feed moisture (%) – 1.1Product moisture (%) – 0.3Specific power consumption (kWh/t) 30.75 25.60(mill, fan, classifier, aux)

Table 2: Da ri performance datad

INTERNATIONAL CEMENT REVIEW JUNE 2011

Ambuja Cement‘s grinding station Nalagarh, India

OPTIMISED GRINDINGOPTIMISED GRINDING

LOE11034_Advertorial_Print_ICR_6Seiter.indd 2 28.07.11 16:00

INTERNATIONAL CEMENT REVIEW JUNE 2011

OPTIMISED GRINDING

For vertical roller mills (VRM), water injection on the grinding table is a common way to stabilise the grinding

bed and gives a smoother mill operation with lower vibration levels. However, there are some drawbacks to water use in a VRM. The feed moisture for OPC is commonly very low and in case water is added to the grinding process it has to be evaporated requiring thermal energy. If cooler exhaust gases are available in a cement plant this will not pose a major problem, but for a standalone grinding this source of hot gases is not available to drive-off any additional water. In this case a hot gas generator is needed to dry the material and to provide sufficient energy for the grinding system. This solution not only wastes fuel, it also creates further expenses.

In some parts of the world the cement industry is not permitted to utilise water or its use is limited. Loesche has been working on a system that can provide grinding without the need for any water injection. Even if some water is available the main aim is a grinding system that can be run without the need for permanent operation of a hot gas generator.

VRMsA vertical roller mill can process many materials such as clinker, slag, gypsum, fly ash or limestone to produce various cement types of various finesse. The mill is part of a process that begins at the quarry. Only after the initial material has been through the raw material grinding, preheater, kiln and the cooler it reaches the finish mill where additives are added and the final product is obtained. Both Loesche and its customers are essentially concerned with this final product and its properties which are influenced by all stages of the cement making process.

Material enters the VRM via a rotary feeder that poses as an air lock (see Figure 1), then moves down the feed chute to

what is the centre of the rotating grinding table. The product is then driven outwards by centrifugal forces, underneath the rollers where the grinding takes place. Ground material moves over the dam ring and goes up with the gas flow to the classifier. The material has either reached the required fineness and leaves the mill towards the bag filter or is sent back for further grinding, via the grid cone onto

the grinding table. Lumps, which escape the rollers and are too heavy to rise with the gas flow drop through the louvre ring to a reject system and are then fed back via the reject system.

Raw mills or coal mills operate using the same size of rollers. What is particular for Loesche cement mills is the 2+2 or 3+3 system, which features a combination of different sizes of rollers. In cement

Water and energy are precious resources and without them life would not be as we know it today. Both commodities will become more expensive and scarcer in the future. Consequently, saving energy and water is essential for ecologically- and economically-viable production, particularly in the cement industry.

by Dr Daniel Strohmeyer, Loesche GmbH, Germany

IStandalone VRMs without HGG

Figure 1: Loesche vertical roller mill for cement grinding – material flow, feed materials and products

Figure 2: grinding plant flowsheet

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

ash and gypsum (up to five per cent) all of which have different physical properties basically leading to different grindabilities and a particular individual behaviour inside the mill.

Standard procedure is to carry out a grinding test to establish a proper sizing for the mill and the gear box. However, at the start of both of the projects it was not known where the different fly

ash or clinker sources would be sourced. Therefore, Loesche had to assume a certain ‘grindability factor‘ and specific power consumption for the feed mix (see Figure 3). The assumptions were based on Loesche’s experience and knowledge of other fly ash cement grinding plants operating in India. Loesche concluded that it would need a 56.3+3 mill with a table diameter of 5.6m. The selected Flender gear box would have a power consumption of 5400kW, a Loesche dynamic classifier LSKS 102CS and a fan motor of 3000kW would form the other main parts of the system (see Table 1).

Loesche’s scope of supply for the two Indian projects was not for the whole grinding plants, but for the mills, classifiers, sampling stations and the air slides for the product transport. Loesche’s product targets were PPC of 4000Blaine at 250tph using a specific power consumption of 30.75kWh/t for all the Loesche equipment and the fan supply (see Table 2).

The PPC product would consist of 60 per cent clinker, five per cent gypsum and 35 per cent fly ash (2500 Blaine). If the plant receives clinker that is high in C3S then the fly ash content can be increased to the maximum permissible according to Indian standards. If the clinker exhibits a low C3S value, the plant can increase the clinker content and reduce the amount of fly ash to obtain the same required cement strength development.

Construction of the mill foundation and the base frame. This is followed by the erection of the pedestals, which are a critical part of the construction phase as correct alignment is essential. The mill gear box is mounted by applying an orange ‘Chockfast’ (see Figure 4) which provides good connection of the gear box base plate and the foundation. The mill

OPTIMISED GRINDING

Figure 5: height of Loesche LM 56.3+3 when installed

Figure 4: erection of gear box

PPC capacity (tph) 250 Gearbox power (kW) 5400 (Flender) Classifier LSKS 102 CS (kW) 560 Fan motor power (kW) 3000 Mill diameter (m) 13.5Height (m) 20 Grinding table diameter (m) 5.6 Grinding table weight (t) 109Master roller (mm) 3 x2450Support roller (mm) 3 x 1600

Table 1: key data for Dadri and Nalagarh grinding stations

Dadri PPC LM 56.3+3 Guarantee Achieved Mill throughput (tph) 250 253Fineness 4000 3920Feed moisture (%) – 1.1Product moisture (%) – 0.3Specific power consumption (kWh/t) 30.75 25.60(mill, fan, classifier, aux)

Table 2: Da ri performance datad

INTERNATIONAL CEMENT REVIEW JUNE 2011

Ambuja Cement‘s grinding station Nalagarh, India

OPTIMISED GRINDINGOPTIMISED GRINDING

LOE11034_Advertorial_Print_ICR_6Seiter.indd 2 28.07.11 16:00

INTERNATIONAL CEMENT REVIEW JUNE 2011

OPTIMISED GRINDING

For vertical roller mills (VRM), water injection on the grinding table is a common way to stabilise the grinding

bed and gives a smoother mill operation with lower vibration levels. However, there are some drawbacks to water use in a VRM. The feed moisture for OPC is commonly very low and in case water is added to the grinding process it has to be evaporated requiring thermal energy. If cooler exhaust gases are available in a cement plant this will not pose a major problem, but for a standalone grinding this source of hot gases is not available to drive-off any additional water. In this case a hot gas generator is needed to dry the material and to provide sufficient energy for the grinding system. This solution not only wastes fuel, it also creates further expenses.

In some parts of the world the cement industry is not permitted to utilise water or its use is limited. Loesche has been working on a system that can provide grinding without the need for any water injection. Even if some water is available the main aim is a grinding system that can be run without the need for permanent operation of a hot gas generator.

VRMsA vertical roller mill can process many materials such as clinker, slag, gypsum, fly ash or limestone to produce various cement types of various finesse. The mill is part of a process that begins at the quarry. Only after the initial material has been through the raw material grinding, preheater, kiln and the cooler it reaches the finish mill where additives are added and the final product is obtained. Both Loesche and its customers are essentially concerned with this final product and its properties which are influenced by all stages of the cement making process.

Material enters the VRM via a rotary feeder that poses as an air lock (see Figure 1), then moves down the feed chute to

what is the centre of the rotating grinding table. The product is then driven outwards by centrifugal forces, underneath the rollers where the grinding takes place. Ground material moves over the dam ring and goes up with the gas flow to the classifier. The material has either reached the required fineness and leaves the mill towards the bag filter or is sent back for further grinding, via the grid cone onto

the grinding table. Lumps, which escape the rollers and are too heavy to rise with the gas flow drop through the louvre ring to a reject system and are then fed back via the reject system.

Raw mills or coal mills operate using the same size of rollers. What is particular for Loesche cement mills is the 2+2 or 3+3 system, which features a combination of different sizes of rollers. In cement

Water and energy are precious resources and without them life would not be as we know it today. Both commodities will become more expensive and scarcer in the future. Consequently, saving energy and water is essential for ecologically- and economically-viable production, particularly in the cement industry.

by Dr Daniel Strohmeyer, Loesche GmbH, Germany

IStandalone VRMs without HGG

Figure 1: Loesche vertical roller mill for cement grinding – material flow, feed materials and products

Figure 2: grinding plant flowsheet

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

mills, Loesche has a ‘S’ support roller and a ‘M’ master roller. The ‘S’ roller is solely to prepare and stabilise the grinding bed. The most difficult thing to achieve when producing cement is to keep the grinding bed stable. In comparison to raw material grinding, with cement milling there are more fines and some parts of the grinding bed tend to become partly fluidised, caused by entrapped air. This reduces the

internal friction within the material layer making it difficult to efficiently apply the grinding forces. So the ‘S’ roller removes the air from the grinding bed and prepares the material for the master roller to carry out the grinding.

The flowsheet for a grinding system with a VRM (see Figure 2) shows that, after the classifier, product is precipitated and then recovered from the bag filter.

A system fan provides the draft through the machine and different sources of hot gases can be utilized if required. Furthermore a wide range of feed materials are tolerated and conveyed to the mill via the feeding system. Ambuja Cement’s Dadri and Nalagarh grinding stationsIn 2007, Loesche received an enquiry for two grinding stations in India. Both would have a cement capacity of 1.6Mta and each would be supplied with a Loesche VRM with 250tph of grinding capacity. The Dadri project is situated near New Delhi and the Nalagarh mill is located further to the north, close to the Himalayas. It became apparent that the grinding stations would need to be operated without a hot gas generator and consequently water injection for the purpose of grinding bed stabilisation was not permitted. Loesche looked at the customer’s requirements before deciding on the best solution. The main constituents to be ground were clinker, fly

OPTIMISED GRINDING

Figure 3: assumed grindability for Ambuja Cement´s Dadri and Nalagarh projects

JUNE 2011 INTERNATIONAL CEMENT REVIEW

ash and gypsum (up to five per cent) all of which have different physical properties basically leading to different grindabilities and a particular individual behaviour inside the mill.

Standard procedure is to carry out a grinding test to establish a proper sizing for the mill and the gear box. However, at the start of both of the projects it was not known where the different fly

ash or clinker sources would be sourced. Therefore, Loesche had to assume a certain ‘grindability factor‘ and specific power consumption for the feed mix (see Figure 3). The assumptions were based on Loesche’s experience and knowledge of other fly ash cement grinding plants operating in India. Loesche concluded that it would need a 56.3+3 mill with a table diameter of 5.6m. The selected Flender gear box would have a power consumption of 5400kW, a Loesche dynamic classifier LSKS 102CS and a fan motor of 3000kW would form the other main parts of the system (see Table 1).

Loesche’s scope of supply for the two Indian projects was not for the whole grinding plants, but for the mills, classifiers, sampling stations and the air slides for the product transport. Loesche’s product targets were PPC of 4000Blaine at 250tph using a specific power consumption of 30.75kWh/t for all the Loesche equipment and the fan supply (see Table 2).

The PPC product would consist of 60 per cent clinker, five per cent gypsum and 35 per cent fly ash (2500 Blaine). If the plant receives clinker that is high in C3S then the fly ash content can be increased to the maximum permissible according to Indian standards. If the clinker exhibits a low C3S value, the plant can increase the clinker content and reduce the amount of fly ash to obtain the same required cement strength development.

Construction of the mill foundation and the base frame. This is followed by the erection of the pedestals, which are a critical part of the construction phase as correct alignment is essential. The mill gear box is mounted by applying an orange ‘Chockfast’ (see Figure 4) which provides good connection of the gear box base plate and the foundation. The mill

OPTIMISED GRINDING

Figure 5: height of Loesche LM 56.3+3 when installed

Figure 4: erection of gear box

PPC capacity (tph) 250 Gearbox power (kW) 5400 (Flender) Classifier LSKS 102 CS (kW) 560 Fan motor power (kW) 3000 Mill diameter (m) 13.5Height (m) 20 Grinding table diameter (m) 5.6 Grinding table weight (t) 109Master roller (mm) 3 x2450Support roller (mm) 3 x 1600

Table 1: key data for Dadri and Nalagarh grinding stations

Dadri PPC LM 56.3+3 Guarantee Achieved Mill throughput (tph) 250 253Fineness 4000 3920Feed moisture (%) – 1.1Product moisture (%) – 0.3Specific power consumption (kWh/t) 30.75 25.60(mill, fan, classifier, aux)

Table 2: Da ri performance datad

INTERNATIONAL CEMENT REVIEW JUNE 2011

Ambuja Cement‘s grinding station Nalagarh, India

OPTIMISED GRINDINGOPTIMISED GRINDING

LOE11034_Advertorial_Print_ICR_6Seiter.indd 2 28.07.11 16:00

housing is preassembled on the ground along with the classifier, before being lifted into place.

The fly ash feeding system (see Figure 6) conveys design feeds dry fly ash directly to the classifier as part of the fly ash already has product fineness and does not need to be ground. Due to that, the capacity of the mill is increased. In the two Indian grinding stations, the fly ash is fed to the machine via two air slides. However, other setups allow for at least four inlets giving a more even distribution of the fly ash over the circumference of the classifier. SummaryLoesche received the order for the two grinding systems in April 2007 and the FOB delivery was in November 2008. Erection started in December 2008 and commissioning commenced in December 2009 with the first feed in February 2010. By April 2010, 250tph of PPC had been reached and in September 2010 further optimisation was done leading to a stable mill operation without any water injection for grinding bed stabilisation.

As a result no hot gas generator was required. The specific power consumption achieved was 5kWh lower than expected. That was in part due to the easier-to-grind clinker and fly ash compared to the assumed values, both of which had an impact on the grindability of the feed mix and the related specific energy consumption. ______________________________ I

OPTIMISED GRINDING

JUNE 2011 INTERNATIONAL CEMENT REVIEW

Figure 7: Nalagarh grinding plant

Figure 6: gypsum and fly ash feed system to the mill

LOESCHE Mill Type LM 56.3+3, Nalagarh, India

Loesche GmbHHansaallee 24340549 DüsseldorfTel. +49 - 211 - 53 53 - 0Fax +49 - 211 - 53 53 - 500E-Mail: loesche@loesche.dewww.loesche.com

OPTIMISED GRINDINGOPTIMISED GRINDING

To creaTe The world’s finesT engineering we are prepared To Think like no one ThoughT before

Now it’s time for our grinding technology. For further information please call +49 211 53 53 0 or visit www.loesche.com

AZ_A4_Hoch_2011_engineering_RZ.indd 1 27.07.11 13:49

Standalone Vertical Roller Mills without Hot Gas Generator

LOE11034_Advertorial_Print_ICR_6Seiter.indd 1 28.07.11 16:00