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CGB-Lab test ( As grinding media for Fly ash )

2020-08-10 17:45:46

As CGB technology has increasingly caught the eyes of the global cement industry thanks to its remarkable performance in power saving,we’d like to share the lab test a couple years ago ( 2016 ) in China, which gives better picture on how to put this new technology into use properly after replacing steel ball in fly ash grinding.

1.Equipment

φ700mm×700mm  Lab Batch mill. It is equiped with torquemeter that can read the power consumption directly.Below is the technical parameter tables:

Item

DescriptionTechnical Data
1Mill Shell Dimension

φ700×700mm  Effective. 600×600mm

2

Gear reducer

XW635       Raito:( 291)

3

Torquemeter

 HX-100

4

Motor

 Y132M47.5  Power7.5kW

5

Liner Shape

 Dragpeb

2.Fly ash origin and grinding media arrangement

The test fly had been stocked for 3 years in lab.Their physical properties literally are better than the regular one and the details are as follow.

Blaine

3498cm2/g
R45um=

50.2%

R80um

32.5%

Grindability

T6000=35.4min

FGD gypsum blaine:

9460cm2/g

3.Mill loading rate ( CGB -ceramic ball Vs steel ball)

During the test, both CGB and steel balls were set with media scheme as below:

Dia. mm

30252015

Ratio %5%23%33%39%

100%

4.The relation between grinding medias and optimal ratio of grinding media to materials:

During test, the mill is set at 40.4 rpm.Steel balls=173kgs @ 23% loading level,CGB= 82kgs @23% loading level ; Below charts demonstrate that at various feeding weight, and various blaines, the grinding time consumed by CGB and steel balls.

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Ceramic ball performance

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Steel ball performance

Above chart suggest, when the blaine is at low span(4000~6000cm2/g), be it CGB or steel ball,the ratio of balls to materials has no big leverage to the grinding time, and the electric power consumption rate are nearly the same. However,when the blaine go high level, the grinding time rise gradually following the ratio of balls to materials increase. When CGB works,at around 14kg feeding weight, the grinding time stay at shortest. It suggests that the optimal ratio of balls to materials for CGB is 6:1. When Steel ball works,at around 15.5kg feeding weight, the grinding time stay at shortest. It suggests that the optimal ratio of balls to materials for steel ball is 11:1.

5.The relations between grinding media and power consumption rate:

Below chart 5.1 demonstrates at same loading level ( 23%), the power consumption rate comparison of Steel ball and CGB-ceramic ball as grinding media. And below Chart 5.2 demonstrates at various loading level ( CGB-45%, steel ball-32%), the power consumption rate comparison of these 2 different grinding medias.

5.1 CGB & Steel ball loading level are both at 23%

Blaine

CGB Steel BallDifference

 Power saving rate

cm2/gkWh/tkWh/tkWh/t

%

~5300

12.120.07.939.5%

~7200

27.643.716.1

36.8%

~970072.295.623.4

24.5%

5.2 CGB loading level at 45%,Steel ball loading level at 32%

Blaine

CGB Steel BallDifference

 Power saving rate

cm2/g

kWh/tkWh/tkWh/t%
~530012.519.87.3

36.9

~7200

30.345.715.433.7
~970086.2104.718.5

17.7

It’s well known that during grinding process,it’s difficult to regulate the blaine on equal value in various place.Hence,the data in above chart are calculated result after multi-point measurement and formula emulating the relation between power consumption and blaine.

Based on above comparison, it suggests that at same loading level of 23%, CGB-ceramic ball has 20-40% power saving value than steel ball; And when the loading levels are different ( CGB @ 45% and Steel ball @ 32% ), the power saving value is between 15-35%. The higher the blaine, the lower the power saving value.

Therefore, for those who intend to use CGB for fly ash grinding, to design the most suitable loading level is of importance.

6.The relations between grinding media and grain distribution:

Below chart shows the grain distribution variation at different blaine by different grinding media ( CGB and steel ball):

Grain size

Steel ballCGBDiff.Steel ballCGB Diff.Steel ballCGB

 Diff.





um

5371cm2/g5387cm2/g⑵-⑴7181cm2/g7203cm2/g⑵-⑴9805cm2/g9730cm2/g

⑵-⑴

1

7.567.20-0.3611.8812.911.0325.0024.24

-0.76

318.7617.67-1.0927.7429.922.1850.4149.44

-0.97

1047.2246.80-0.4261.3865.133.7583.8483.43

-0.41

15

60.0160.400.3974.9779.214.2491.8792.60

0.73

30

82.5184.091.5893.9296.412.4999.2799.86

0.59

45

92.6594.191.5499.1599.920.77100.00100.00

0.00

R45um

3.5

2.5








Above chart suggest: at R45um, CGB fly ash is smaller than steel ball one.The grain content below 10um is also less.However, in the span 10-30um, the content is high. This result comply with the test for CGB cement.It again concludes that for grain size below 3um,CGB has less grinding value than steel ball,but for grain size between 10-30um, CGB is prior in grinding value.

7.The relations between grinding media and fly ash activity:

Below chart shows the relation.Be it CGB or steel ball, when the fly ash blaine is less than 7200 cm2/g, the activity change little.However,when it goes high, the activity will witness a big difference.

Although the leverage is slight on activity between CGB and steel ball,test result still suggests that CGB has better activity value more or less than steel ball in fly ash grinding.

Time

7 day activity

28 day activity

Grinding MediaSteel ballCGBSteel ball

CGB

Raw fly ash555562

62

~5300 cm2/g

64667783

~7200 cm2/g

667180

84

~9700 cm2/g697585

91

Individual test was performed for CGB grinding value to fly ash at different loading level, the result suggests no big difference as below chart show:

   Time

7 day activity

28 day activity

Loading level

23%35%45%23%35%

45%

~5300 cm2/g

6466657774

75

8.The relations between grinding media and water requirement: 

Below chart shows at different blaine, with different grinding media ( CGB and steel ball),the water requirement of fly ash product:

Blaine

Steel ball

CGB

~5300cm2/g

105%104%
~7200cm2/g102%

103%

~9700cm2/g102%

101%

The test result suggests be it CGB or steel ball, the water requirement of fly ash productwillfall as the blaine rise. At equal blaine, these 2 grinding medias leverage nearly the same value to the water requirement of fly ash.

9.Summary of this test:

According to above test result analysis, the comprehensive comparison result between steel ball and CGB is listed as follow:

Item.NoDescription   Steel ballCGB

Comparison

1Mill power,%10085~65

Average↓20%

2

R45μm,%3.52.5↓1.0%
3Fly ash activity100105

↑5.0%

4Water requirement100100

To summarize:

  • (1) At low blaine requirement, be it CGB or steel ball, the ratio of ball to materials matters little. However, as the blaine requirement go high, the ratio of ball to materials begin leveraging remarkably. As grinding media for fly ash, the most suitable ratio is 6:1, and 11:1 for steel ball.

  • (2) Be it CGB or steel ball, the loading level matter the power consumption rate in same way. When the blaine is less than 7200cm2/g, the higher loading level doesn’t necessarily result in too much higher consumption rate.Chances are, it’s mere 0-5% increase; However, when the blaine is upto 9700cm2/g, the CGB loading level may bring up the power rate by 10-18%, whereas steel ball by 9%;

  • (3) When CGB and steel ball are both regulated at 23% loading level, the power saving rate of CGB is around 20-40%. When CGB stay at around 45% and steel ball 32%, the power saving rate of CGB is around 15-35%.The higher blaine,the less power saving rate.

  • (4) Regardless of CGB or steel ball, when the fly ash blaine is less than 7200cm2/g, the activity doesn’t change too much against the blaine change. However, when the blaine stay at high level, the activity will witness big difference against . By comparison, in terms of fly ash activity, CGB shows better value than steel ball though it is little difference.

  • (5) In regards of water requirement for fly ash final product, there’s nearly no difference between CGB and steel ball both serving as grinding media.

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