1 Cement Mill Ppt
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View 1 Cement Mill Ppt as PDF for free.
More details
- Words: 1,600
- Pages: 52
Loading documents preview...
Topic to be discuss 1. 2. 3. 4. 5. 6. 7. 8. 9.
Introduction Overview internal element Cataracting & cascading effect of grinding media charge. Cement grinding system Operation of cement mills. Chamber sampling Separator Method of evaluating separator Diagnostic study
1.
Comminute Engineering – Size Reduction
2.
Comminute – 50% - 70% of Plant Electrical Energy Consumption Comminute Methods i. ii. iii. iv.
Compression forces Friction / Shear forces Inter particles contact forces Impact Forces
1.Introduction Three
milling systems can be used in cement industry: - Open Circuit - Close Circuit - Air Swept
1.2.
Open Circuit Mills These are multi compartment grinding mills :
Compartment 1: -
for perishing by largest grinding media coarse grinding takes place here depends on hardness of material
Compartment 2: -
Fine grinding takes place here
-
Grinding by smallest size grinding media
Grinding media in each compartment is combination of different size balls
Open Circuit Mill (Compound Mill)
Feed material is pre ground in 1st compartment and in further compartments to increase fineness of final product .
Heat generated by grinding gets radiated by air. - Air flow rate is limited by maximum speed inside the mill i.e. coarse particles should not be swept out of the mill.
Advantages
Low investment Cost
Uncomplicated System
Disadvantages • Tendency of formation of coating and agglomeration. • Oversize particles in the final product. • High cement temperature due to limited air flow through the mill. • More sensitive against variations in grindability of material.
1.2
Closed Circuit Mills These are usually two compartment mills : Compartment 1: For pre crushing of Clinker by larger size of grinding media
Compartment 2: Fine – Grinding smaller size of grinding media • Once the material has gone through the mill it is transported to a separator where it is divided into two fractions. • The finer fraction being the product and the coarser being the return to the mill for further grinding.
Closed Circuit Grinding
SEPATATOR
ELEVATOR
COARSE RETURN PRODUCT
1. FEED
2.
2. Grinding Aspects
Open Circuit:
2.1 -
Fines is achieved after a few meters.
- This portion is further exposed to the ball impact of the remaining mill length.
Side effect of above aspects : -
Cushion effects of material
-
Coating on balls and liners
Partially the grinding energy is converted into heat by friction between particles and increases the CM temperature.
2.3 Closed Circuit
Retention time is shorter i.e. material is removed earlier less risk of coating.
Other reason for coating which reduces the grinding capacity :
while operating with too high temperatures of clinker feed to the mill, - therefore water injection needed.
3.
Abut Heat Generation •
Heat generated in cement mill consists of -
•
Heat produced by grinding Heat contained by clinker entering the mill
Heat removal from mill -
By radiation and convection Heat carried out by cement leaving the mill Remaining heat to remove
•
By ventilating the mill with aim
•
By internal or external cooling of the cement.
•
Problems due to unsuitable mill ventilation / cement cooling It affects cement quality i. Dehydration of Gypsum ii. False set iii. Loss of strength
Possibilities of Cement Cooling
4. •
In open circuit mills -
Cement is cooled inside the mill by ventilation / water injection
-
External coolers are often used after the mill *To reduce cement temperature to avoid storage problems in silos *Or to maintain acceptable temperature for Packing plant
•
Small mills are also cooled by water spray on outer shell -This needs large water flow rates and coating / scaling forms on shell -
So external water spray is avoided.
5.
Water Injection into The Mill
5.1 General • Water injection •
Control cement temperature within the mill
•
Prevent gypsum dehydration At any place within or after the mill -
To restrict false set and lump formation in silos
-
To reduce loss of strength properties
-
To reduce workability problems of the cement.
5.2 Water Injection Techniques • Water injection either in 1st or in 2nd chamber or in both •
Either in co-current or in counter current
•
Co-current injection leads to a more continuously decreasing cement temperature along the mill axis. i.e. peak temperatures as often experienced with countercurrent injection, can be avoided.
•
Due to problematic arrangement of water supply pipes along mill shell for Cocurrent method, preference is nowadays given to the counter-current injection.
a. Co-current Water injection
b.
Counter-current Water injection
Water Injection into 1st Compartment
•
In case of high clinker temperature (abore 150°C), more than 35% water flow rate in 1st compartment should be considered.
•
For low clinker temperature (less than 80ºC) no water required in 1st compartment.
Water Injection into 2nd Compartment
is
BALL MILL
Avdhesh varshney
Avdhesh varshney
Avdhesh varshney
Avdhesh varshney
Hybrid System
Two Stage Grinding System
Roller press combined with single chamber ball mill / tube mill
Finish Grinding System with Roller Press
Finish Grinding System with Vertical Roller Mill
Wear behaviour Open circuit Closed circuit Open circuit
~ 40 – 50 g/t
Closed circuit ~ 10 – 30 g/t
Other Aspects : • The grinding media in open circuit mill is adjusted to
suit a particular type of cement. • Other types can not be ground with the same charge.
1.5 General Equipment Description of Ball Mill
Cement mill (Ball Mill) consists mainly of : A rotation steel cylindrical shell supported at both ends on turning / slide shoe bearings. -
Liners for protecting the inside surface of the shell
-
Diaphragms for dividing the mill into two or more compartments
-
Grinding Balls
-
Mill cooling system
Details of Liners •
The lines which protect the shell from wearing action of clinker additives, also helps in the grinding process.
and
•
In the second compartment “classifying” liners are used which help to segregate the grinding media according to its size -larger balls towards the compartment, small balls towards the discharge end.
• This helps to improve the grinding efficiency.
Diaphragms • Mill diaphragms are provided with slots through which material air pass from 1st compartment to the 2nd compartment.
and venting
Grinding Media • The mill chambers are partially filled with steel balls having diameters ranging from 90 mm to 60 mm in 1st compartment and from 50 mm balls to 15 mm Ball in the 2nd compartment.
Heat Generation • During grinding heat is generated in the mill which if not controlled would raise the temperature of and affecting cement quality. • The grinding heat is dissipated by injecting atomized water in the mill
chamber which on evaporation, cools down the mill to acceptable temperature.
5.0 Trouble Shooting- Possible disturbances : Disturbance 1. Mill Sound a. Dull sound b. Loud sound 2. Mill Discharge Product a. Too coarse
b. Too fine
3. Mill outlet Pressure a. too high b. too low
Possible Reasons a. Mill overfilled b. No sufficient material a. - Mill overfilled - Separator clogged - Feed size to mill too large b. - Fresh feed rate to mill too low - High circulating load - Feed size too small - Separator not adjusted a. - Mill inlet clogged - Diaphragm clogged b. - Too low material in the mill - Diaphragm broken
Disturbance
Possible Reasons
4. Cement temperature a. too high b. too low
a. - Clinker temperature too high - Low venting air flow rate - Mill overfilled - Ball coating
5. Mill Output a. Too low
a. - Unsuitable ball charge composition or wear of balls - Change of clinker grindability - See also 2) – 7)
Avdhesh varshney
Open Circuit Mill
•
This helps to improve the grinding efficiency. Diaphragms'
•
Mill diaphragms are provided with slots through which material and venting from 1st compartment to the 2nd compartment.
air pass
Grinding Media •
The mill chambers are partially filled with steel balls having diameters ranging from 90 mm to 60 mm in 1st compartment and from 50 mm balls to 17 mm Ball in the 2nd compartment. Heat Generation
•
During grinding heat is generated in the mill which if not controlled would raise the temperature of and affecting cement quality.
•
The grinding heat is dissipated by injecting atomized water in the mill chamber which on evaporation, cools down the mill to acceptable temperature.
Cement Grinding mill
Cement Grinding mill
Ball Mill With Straight Liners
Cement Mill with large circulating load:
The circulating load factor is approximately 7, the residue gradient from inlet to outlet of the mill is low.
In the 1st compartment feed is mixed with a large amount of tailings, balls are relatively small.
Ball charge in 1st compartment ,has a low permeability, is saturated with material by the large circulating load.
In 2nd compartment material is rather coarse, balls are relatively large.
Ball Mill With Classifying Liners
Cement Mill with large circulating load: The circulating load factor is about 3, the residue gradient from inlet to outlet of the mill is high. Material in the 1st chamber contains a large quantity of coarse particles, balls are large. Charge in 1st compartment is permeable and material passes through easily, circulating load being low. In 2nd chamber the material is fine, grinding bodies are small and sorted, by self sorting liners, in order of decreasing size from inlet to outlet of the compartment.
Duo lift Lining Plate
A View of Diaphragm
Diaphragm Structure With Plates
Avdhesh varshney
Introduction Overview internal element Cataracting & cascading effect of grinding media charge. Cement grinding system Operation of cement mills. Chamber sampling Separator Method of evaluating separator Diagnostic study
1.
Comminute Engineering – Size Reduction
2.
Comminute – 50% - 70% of Plant Electrical Energy Consumption Comminute Methods i. ii. iii. iv.
Compression forces Friction / Shear forces Inter particles contact forces Impact Forces
1.Introduction Three
milling systems can be used in cement industry: - Open Circuit - Close Circuit - Air Swept
1.2.
Open Circuit Mills These are multi compartment grinding mills :
Compartment 1: -
for perishing by largest grinding media coarse grinding takes place here depends on hardness of material
Compartment 2: -
Fine grinding takes place here
-
Grinding by smallest size grinding media
Grinding media in each compartment is combination of different size balls
Open Circuit Mill (Compound Mill)
Feed material is pre ground in 1st compartment and in further compartments to increase fineness of final product .
Heat generated by grinding gets radiated by air. - Air flow rate is limited by maximum speed inside the mill i.e. coarse particles should not be swept out of the mill.
Advantages
Low investment Cost
Uncomplicated System
Disadvantages • Tendency of formation of coating and agglomeration. • Oversize particles in the final product. • High cement temperature due to limited air flow through the mill. • More sensitive against variations in grindability of material.
1.2
Closed Circuit Mills These are usually two compartment mills : Compartment 1: For pre crushing of Clinker by larger size of grinding media
Compartment 2: Fine – Grinding smaller size of grinding media • Once the material has gone through the mill it is transported to a separator where it is divided into two fractions. • The finer fraction being the product and the coarser being the return to the mill for further grinding.
Closed Circuit Grinding
SEPATATOR
ELEVATOR
COARSE RETURN PRODUCT
1. FEED
2.
2. Grinding Aspects
Open Circuit:
2.1 -
Fines is achieved after a few meters.
- This portion is further exposed to the ball impact of the remaining mill length.
Side effect of above aspects : -
Cushion effects of material
-
Coating on balls and liners
Partially the grinding energy is converted into heat by friction between particles and increases the CM temperature.
2.3 Closed Circuit
Retention time is shorter i.e. material is removed earlier less risk of coating.
Other reason for coating which reduces the grinding capacity :
while operating with too high temperatures of clinker feed to the mill, - therefore water injection needed.
3.
Abut Heat Generation •
Heat generated in cement mill consists of -
•
Heat produced by grinding Heat contained by clinker entering the mill
Heat removal from mill -
By radiation and convection Heat carried out by cement leaving the mill Remaining heat to remove
•
By ventilating the mill with aim
•
By internal or external cooling of the cement.
•
Problems due to unsuitable mill ventilation / cement cooling It affects cement quality i. Dehydration of Gypsum ii. False set iii. Loss of strength
Possibilities of Cement Cooling
4. •
In open circuit mills -
Cement is cooled inside the mill by ventilation / water injection
-
External coolers are often used after the mill *To reduce cement temperature to avoid storage problems in silos *Or to maintain acceptable temperature for Packing plant
•
Small mills are also cooled by water spray on outer shell -This needs large water flow rates and coating / scaling forms on shell -
So external water spray is avoided.
5.
Water Injection into The Mill
5.1 General • Water injection •
Control cement temperature within the mill
•
Prevent gypsum dehydration At any place within or after the mill -
To restrict false set and lump formation in silos
-
To reduce loss of strength properties
-
To reduce workability problems of the cement.
5.2 Water Injection Techniques • Water injection either in 1st or in 2nd chamber or in both •
Either in co-current or in counter current
•
Co-current injection leads to a more continuously decreasing cement temperature along the mill axis. i.e. peak temperatures as often experienced with countercurrent injection, can be avoided.
•
Due to problematic arrangement of water supply pipes along mill shell for Cocurrent method, preference is nowadays given to the counter-current injection.
a. Co-current Water injection
b.
Counter-current Water injection
Water Injection into 1st Compartment
•
In case of high clinker temperature (abore 150°C), more than 35% water flow rate in 1st compartment should be considered.
•
For low clinker temperature (less than 80ºC) no water required in 1st compartment.
Water Injection into 2nd Compartment
is
BALL MILL
Avdhesh varshney
Avdhesh varshney
Avdhesh varshney
Avdhesh varshney
Hybrid System
Two Stage Grinding System
Roller press combined with single chamber ball mill / tube mill
Finish Grinding System with Roller Press
Finish Grinding System with Vertical Roller Mill
Wear behaviour Open circuit Closed circuit Open circuit
~ 40 – 50 g/t
Closed circuit ~ 10 – 30 g/t
Other Aspects : • The grinding media in open circuit mill is adjusted to
suit a particular type of cement. • Other types can not be ground with the same charge.
1.5 General Equipment Description of Ball Mill
Cement mill (Ball Mill) consists mainly of : A rotation steel cylindrical shell supported at both ends on turning / slide shoe bearings. -
Liners for protecting the inside surface of the shell
-
Diaphragms for dividing the mill into two or more compartments
-
Grinding Balls
-
Mill cooling system
Details of Liners •
The lines which protect the shell from wearing action of clinker additives, also helps in the grinding process.
and
•
In the second compartment “classifying” liners are used which help to segregate the grinding media according to its size -larger balls towards the compartment, small balls towards the discharge end.
• This helps to improve the grinding efficiency.
Diaphragms • Mill diaphragms are provided with slots through which material air pass from 1st compartment to the 2nd compartment.
and venting
Grinding Media • The mill chambers are partially filled with steel balls having diameters ranging from 90 mm to 60 mm in 1st compartment and from 50 mm balls to 15 mm Ball in the 2nd compartment.
Heat Generation • During grinding heat is generated in the mill which if not controlled would raise the temperature of and affecting cement quality. • The grinding heat is dissipated by injecting atomized water in the mill
chamber which on evaporation, cools down the mill to acceptable temperature.
5.0 Trouble Shooting- Possible disturbances : Disturbance 1. Mill Sound a. Dull sound b. Loud sound 2. Mill Discharge Product a. Too coarse
b. Too fine
3. Mill outlet Pressure a. too high b. too low
Possible Reasons a. Mill overfilled b. No sufficient material a. - Mill overfilled - Separator clogged - Feed size to mill too large b. - Fresh feed rate to mill too low - High circulating load - Feed size too small - Separator not adjusted a. - Mill inlet clogged - Diaphragm clogged b. - Too low material in the mill - Diaphragm broken
Disturbance
Possible Reasons
4. Cement temperature a. too high b. too low
a. - Clinker temperature too high - Low venting air flow rate - Mill overfilled - Ball coating
5. Mill Output a. Too low
a. - Unsuitable ball charge composition or wear of balls - Change of clinker grindability - See also 2) – 7)
Avdhesh varshney
Open Circuit Mill
•
This helps to improve the grinding efficiency. Diaphragms'
•
Mill diaphragms are provided with slots through which material and venting from 1st compartment to the 2nd compartment.
air pass
Grinding Media •
The mill chambers are partially filled with steel balls having diameters ranging from 90 mm to 60 mm in 1st compartment and from 50 mm balls to 17 mm Ball in the 2nd compartment. Heat Generation
•
During grinding heat is generated in the mill which if not controlled would raise the temperature of and affecting cement quality.
•
The grinding heat is dissipated by injecting atomized water in the mill chamber which on evaporation, cools down the mill to acceptable temperature.
Cement Grinding mill
Cement Grinding mill
Ball Mill With Straight Liners
Cement Mill with large circulating load:
The circulating load factor is approximately 7, the residue gradient from inlet to outlet of the mill is low.
In the 1st compartment feed is mixed with a large amount of tailings, balls are relatively small.
Ball charge in 1st compartment ,has a low permeability, is saturated with material by the large circulating load.
In 2nd compartment material is rather coarse, balls are relatively large.
Ball Mill With Classifying Liners
Cement Mill with large circulating load: The circulating load factor is about 3, the residue gradient from inlet to outlet of the mill is high. Material in the 1st chamber contains a large quantity of coarse particles, balls are large. Charge in 1st compartment is permeable and material passes through easily, circulating load being low. In 2nd chamber the material is fine, grinding bodies are small and sorted, by self sorting liners, in order of decreasing size from inlet to outlet of the compartment.
Duo lift Lining Plate
A View of Diaphragm
Diaphragm Structure With Plates
Avdhesh varshney
Related Documents
1 Cement Mill Ppt
February 2021 0
Coal Mill Part(1)
February 2021 0
Ball Mill
February 2021 0
Understanding Cement
January 2021 1
Lucie Mill
January 2021 1More Documents from "Joko Dewoto"