manufacturing of pulverizerused used in bowl mill ppt

60 common examples of poka yoke - lean factories

The aim of mistake-proofing is to remove the need for people to think about the products or processes they are using. This is because the products have a design that makes it impossible to use them in the wrong way.

When someone uses the product the wrong way, it does not function and it becomes obvious to the user that they are doing the wrong thing. The simple yet effective design features make it difficult for errors to occur during usage of the product.

The concept developed out of the need to achieve quality in production processes. It was Shigeo Shingo, one of the pioneers of the Toyota Production System, who proposed the concept. He was a quality guru who proposed the idea of Zero Defects as a quality paradigm.

Many people lose their lives or get maimed through vehicular accidents each year. Safety of users of automobiles is of paramount importance and many measures have been taken to make them safe. The following are examples of mistake-proofing in the automotive industry:

In lean manufacturing systems, poka yoke also includes a philosophy of constantly working to prevent mistakes from occurring in the first place. The internal processes in lean manufacturing systems are supposed to produce quality products the first time. Error-proofing in this case is a quality assurance technique that ensures quality is in-built and results in better products.

For the final product to be of high quality, all the inter-connected process steps have to give first time quality. If an mistake or defect is allowed to move to the next step, the likelihood of it appearing in the finished product is very high. It is therefore necessary to develop ways of preventing a defective product moving to downstream process.

This is important because a finished product is considered to be the most expensive form of inventory due to the accumulated costs along the value chain. If a defect occurs in the finished product, the costs of production increase due to the effort required to correct it.

The space industry requires accurate procedures to be constantly carried out so as to ensure the successful completion of space missions. Any small error in the implementation of these procedures can lead to a major disaster.

The industry has therefore developed many mistake-proofing devices to prevent errors from occurring and this has resulted in the high success rates of space mission over the years. The following are a few examples of error-proofing in the space industry:

Nuclear accidents can have devastating effects as was seen in the Chernobyl disaster. Nuclear power plants use thedefense-in-depthconcept of barriers to the prevent fission material from being released from the reactor core to the environment.

The fuel rods have cladding that prevent the release of fission material in the event of a melt-down. The reactor is designed to assist in the cooling of the rods in case there is a decrease in the cooling water in the core. This is very important as the heat released during the decay of radioactive material can start a chain reaction that is unstoppable.

The fact that air travel is considered to be safer than road travel can be attributed to a number of fool-proofing devices that have been put in place over the years. While air accidents still occur, they have significantly been reduced because of these devices:

From the above comprehensive list of examples, it becomes obvious that there are certain characteristics of error-proofing devices that help in achieving the aims of mistake-proofing. These characteristics include:

This is a blue ocean, we feel everyone in this market can earn more than a good living so there is no such thing as a competitor at the moment. If you are in the industry and want to collaborate to bring more lean methodology to mankind, please reach out.

coil pulverizers for boilers - bright hub engineering

Boilers for steam generation in power plants and process industries use coal as fuel. The percentage of boilers operating with coal as fuel outnumbers the boilers using all other fuels combined. Coal is pulverized before firing for achieving a stable and efficient combustion. Many types of pulverizers are used in boilers by different designers.

History of pulverizationThe history of pulverization dates back as early as 1824 and was envisioned by Carnot in a coal fired engine. In 1890 Diesel made use of pulverized coal in his diesel engine. Pulverized coal firing was first developed in the cement industry and then migrated to the power and process industries. Actually Thomas Alva Edison and the Niepce brothers of France were pioneers in pulverized coal firing. This technology gained momentum after World War I in the power generating industry. It was John Anderson, chief engineer of power plants at the Wisconsin Electric Power Company who introduced pulverized coal firing in power stations.Pulverized coal is the most efficient way of using coal in a steam generator. The coal is ground so that about 70 % will pass through 200 mesh (0.075 mm) and 99 % will pass through 50 mesh (0.300 mm). A pulverized coal boiler can be easily adapted for other fuels like gas if required later without much difficulty. However, during the design stage it is possible to make boilers firing multiple fuels. With pulverization technology, large size boilers could be designed, manufactured, erected, and run much more efficiently.Types of pulverizersMainly there are three types of pulverizer used in industry: the slow speed mills like ball tube mills, the medium speed mills like bowl, ball and race, roller mills fall in this category, and the third type is the high speed impact mill. The slow speed and medium speed mills are selected for coals ranging from sub-bituminous to anthracite. The high speed mills are used mainly for lignite.The purpose of a pulverizer in a coal fired boilerTo supply pulverized coal to the boiler as per requirement of steam generationTransport the pulverized coal from pulverizer to the burners in the boilerTo remove moisture in coal to an acceptable level for firing in boilerTo remove high density inorganics from coal during pulverizationTo classify coal particles to the required level of fineness, normally 70 % through 200 mesh and less than 2% on 50 meshCoal parameters affecting pulverizer outputWhile selecting a pulverizer, the coal characteristics play an important role. The Hardgrove index, total moisture, input coal size, output fineness, and mill wear have direct impact on the mill output.The Hardgrove index of coal tells us about the ease with which it can be pulverized. A higher Hardgrove index indicates the coal is easier to grind. 50 HGI normally is taken for calculating the base capacity of the mill. When coal with HGI higher than 50 is fed to the pulverizer, the output will be higher than base capacity, and below 50 HGI, the output will be lower.The total moisture in coal has a high effect on mill output. The higher the moisture, the lower the output.Higher pulverized coal fineness increases the recirculation in the mill and the output reduces.The inlet size of the coal also affects the mill output directly.Mill air flow variations result in changes in mill outlet temperature and fineness as well as capacity.Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

The history of pulverization dates back as early as 1824 and was envisioned by Carnot in a coal fired engine. In 1890 Diesel made use of pulverized coal in his diesel engine. Pulverized coal firing was first developed in the cement industry and then migrated to the power and process industries. Actually Thomas Alva Edison and the Niepce brothers of France were pioneers in pulverized coal firing. This technology gained momentum after World War I in the power generating industry. It was John Anderson, chief engineer of power plants at the Wisconsin Electric Power Company who introduced pulverized coal firing in power stations.

Pulverized coal is the most efficient way of using coal in a steam generator. The coal is ground so that about 70 % will pass through 200 mesh (0.075 mm) and 99 % will pass through 50 mesh (0.300 mm). A pulverized coal boiler can be easily adapted for other fuels like gas if required later without much difficulty. However, during the design stage it is possible to make boilers firing multiple fuels. With pulverization technology, large size boilers could be designed, manufactured, erected, and run much more efficiently.Types of pulverizersMainly there are three types of pulverizer used in industry: the slow speed mills like ball tube mills, the medium speed mills like bowl, ball and race, roller mills fall in this category, and the third type is the high speed impact mill. The slow speed and medium speed mills are selected for coals ranging from sub-bituminous to anthracite. The high speed mills are used mainly for lignite.The purpose of a pulverizer in a coal fired boilerTo supply pulverized coal to the boiler as per requirement of steam generationTransport the pulverized coal from pulverizer to the burners in the boilerTo remove moisture in coal to an acceptable level for firing in boilerTo remove high density inorganics from coal during pulverizationTo classify coal particles to the required level of fineness, normally 70 % through 200 mesh and less than 2% on 50 meshCoal parameters affecting pulverizer outputWhile selecting a pulverizer, the coal characteristics play an important role. The Hardgrove index, total moisture, input coal size, output fineness, and mill wear have direct impact on the mill output.The Hardgrove index of coal tells us about the ease with which it can be pulverized. A higher Hardgrove index indicates the coal is easier to grind. 50 HGI normally is taken for calculating the base capacity of the mill. When coal with HGI higher than 50 is fed to the pulverizer, the output will be higher than base capacity, and below 50 HGI, the output will be lower.The total moisture in coal has a high effect on mill output. The higher the moisture, the lower the output.Higher pulverized coal fineness increases the recirculation in the mill and the output reduces.The inlet size of the coal also affects the mill output directly.Mill air flow variations result in changes in mill outlet temperature and fineness as well as capacity.Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

Types of pulverizersMainly there are three types of pulverizer used in industry: the slow speed mills like ball tube mills, the medium speed mills like bowl, ball and race, roller mills fall in this category, and the third type is the high speed impact mill. The slow speed and medium speed mills are selected for coals ranging from sub-bituminous to anthracite. The high speed mills are used mainly for lignite.The purpose of a pulverizer in a coal fired boilerTo supply pulverized coal to the boiler as per requirement of steam generationTransport the pulverized coal from pulverizer to the burners in the boilerTo remove moisture in coal to an acceptable level for firing in boilerTo remove high density inorganics from coal during pulverizationTo classify coal particles to the required level of fineness, normally 70 % through 200 mesh and less than 2% on 50 meshCoal parameters affecting pulverizer outputWhile selecting a pulverizer, the coal characteristics play an important role. The Hardgrove index, total moisture, input coal size, output fineness, and mill wear have direct impact on the mill output.The Hardgrove index of coal tells us about the ease with which it can be pulverized. A higher Hardgrove index indicates the coal is easier to grind. 50 HGI normally is taken for calculating the base capacity of the mill. When coal with HGI higher than 50 is fed to the pulverizer, the output will be higher than base capacity, and below 50 HGI, the output will be lower.The total moisture in coal has a high effect on mill output. The higher the moisture, the lower the output.Higher pulverized coal fineness increases the recirculation in the mill and the output reduces.The inlet size of the coal also affects the mill output directly.Mill air flow variations result in changes in mill outlet temperature and fineness as well as capacity.Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

Mainly there are three types of pulverizer used in industry: the slow speed mills like ball tube mills, the medium speed mills like bowl, ball and race, roller mills fall in this category, and the third type is the high speed impact mill. The slow speed and medium speed mills are selected for coals ranging from sub-bituminous to anthracite. The high speed mills are used mainly for lignite.

The purpose of a pulverizer in a coal fired boilerTo supply pulverized coal to the boiler as per requirement of steam generationTransport the pulverized coal from pulverizer to the burners in the boilerTo remove moisture in coal to an acceptable level for firing in boilerTo remove high density inorganics from coal during pulverizationTo classify coal particles to the required level of fineness, normally 70 % through 200 mesh and less than 2% on 50 meshCoal parameters affecting pulverizer outputWhile selecting a pulverizer, the coal characteristics play an important role. The Hardgrove index, total moisture, input coal size, output fineness, and mill wear have direct impact on the mill output.The Hardgrove index of coal tells us about the ease with which it can be pulverized. A higher Hardgrove index indicates the coal is easier to grind. 50 HGI normally is taken for calculating the base capacity of the mill. When coal with HGI higher than 50 is fed to the pulverizer, the output will be higher than base capacity, and below 50 HGI, the output will be lower.The total moisture in coal has a high effect on mill output. The higher the moisture, the lower the output.Higher pulverized coal fineness increases the recirculation in the mill and the output reduces.The inlet size of the coal also affects the mill output directly.Mill air flow variations result in changes in mill outlet temperature and fineness as well as capacity.Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

While selecting a pulverizer, the coal characteristics play an important role. The Hardgrove index, total moisture, input coal size, output fineness, and mill wear have direct impact on the mill output.The Hardgrove index of coal tells us about the ease with which it can be pulverized. A higher Hardgrove index indicates the coal is easier to grind. 50 HGI normally is taken for calculating the base capacity of the mill. When coal with HGI higher than 50 is fed to the pulverizer, the output will be higher than base capacity, and below 50 HGI, the output will be lower.The total moisture in coal has a high effect on mill output. The higher the moisture, the lower the output.Higher pulverized coal fineness increases the recirculation in the mill and the output reduces.The inlet size of the coal also affects the mill output directly.Mill air flow variations result in changes in mill outlet temperature and fineness as well as capacity.Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

Ball tube millBall tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

Ball tube mills are either pressurized or suction type. In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. In this type, leakage in the mill area is high.

In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

Normally the ball mill designers use three types of balls with three different diameters. These balls reduce in size as the mills operate and so the highest size ball is normally used for recharging. In earlier days, most of the ball mills had a single inlet and outlet, but now designers use both ends to feed coal and also for taking out pulverized coal. The control systems are well made to understand the requirement of ball charge and the output from the mill. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is very high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 75 tons per hour output for a specific coal.

Vertical spindle millThere are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

There are many different varieties of vertical mills. Designers use large steel balls ranging from 2 to 6 or more between two grinding rings for pulverizing. There are also other types like conical rollers with shallow bowl; deep bowl, etc. where load is applied on the rollers and the bowl rotates while pulverizing. These types of mill are designed normally up to 60 tons per hour for a specific coal; however there are vertical mills with 90 tons per hour output. A vertical spindle mill is also designed for pressurized and suction type requirements. Boiler designers use this type of mill for poor quality coal as this type of mill rejects foreign materials like stones and other high density materials. The power consumed by the mill per ton of coal ground is only two-thirds of the ball mills. However if the primary air fan power is also taken into account, in the case of a pressurized mill the power consumption is lower only by about 15%.High speed impact millThis type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

This type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized. High speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite.While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

While selecting the type of mill boiler designers must clearly understand the coal characteristics, the overall system being used, and the maintenance requirement. It is always seen that if the advantage of the mill alone is considered, then the overall boiler economics can prove to be different.

aluminium production process

The pure form of aluminium does not naturally occur in nature, so remained largely unknown until as recently as 200 years ago. Creating aluminium using electricity was first developed in 1886 and is still used to this day.

The aluminium production process starts with the mining of bauxites, an aluminium rich mineral in in the form of aluminium hydroxide. About 90% of global bauxite supply is found in tropical areas.

Bauxite is crushed, dried and ground in special mills where it is mixed with a small amount of water. This process produces a thick paste that is collected in special containers and heated with steam to remove most of the silicon present in bauxites.

The ore is loaded into autoclaves and treated with limecaustic soda. Aluminium oxide appears in the resulting slurry while all the admixtures settle to the bottom as red mud.

The sodium aluminate solution is stirred in precipitators for several days, eventually pure alumina or Al2O3 settles at the bottom.

At an aluminium smelter, alumina is poured into special reduction cells with molten cryolite at 950. Electric currents are then induced in the mixture at 400 kA or above; this current breaks the bond between the aluminium and oxygen atoms resulting in liquid aluminium settling at the bottom of the reduction cell.

Primary aluminium is cast into ingots and shipped to customers or used in the production of aluminium alloys for various purposes.

The process where the aluminium is shaped to its required form. This process is used for making the vast majority of aluminium products from spectacle frames, telephone bodies, aeroplane fuselages or spaceship bodies.

The malleability of aluminium means it can be easily rolled into thin sheets. To that end, aluminium alloys are cast into rectangular beams up to 9 metres in length, these are then rolled into sheets from which aluminium foil and beverage cans are made, as well as parts of automobile bodies and a vast array of other products.

The process where the aluminium is shaped to its required form. This process is used for making the vast majority of aluminium products from spectacle frames, telephone bodies, aeroplane fuselages or spaceship bodies.

Unlike iron, aluminium is corrosion resistant so it can be remelted and reused an infinite number of times. The added benefit is that recycling aluminium requires only 5% of the energy needed to make the same amount of primary aluminium.