81 posts
Request for feedback for a Two Chamber Cement Mill Ball Charge and Longitudinal Sieve Analysis
I am looking to get feedback for the following cement mill for a white cement plant. The first compartment has lifting liners and the second compartment has lifting at the beginning followed by classifying liner. The mill dimension is as follows:
Mill Diameter: 


3.4 
m 

Mill Length: 


11.0 
m 

First Chamber Effective Diameter: 


3.23 
m 

First Chamber Effective Length: 


2.3 
m 

Second Chamber Effective Diameter: 


3.27 
m 

Second Chamber Effective Length: 


8.0 
m 
Input clinker sieve analysis:
mm 
Clk 
25.40 
1.90% 
19.00 
3.50% 
12.70 
10.10% 
9.50 
19.50% 
8.00 
 
6.35 
45.10% 
4.76 
63.40% 
2.38 
85.30% 
1.19 
94.60% 
0.84 
97.40% 
0.60 
98.10% 
And the existing ball charge design:
First Chamber Ball Charge 









Ø Ball [mm] 
Weight [ t ] 
Percent [%] 



90 
6.5 
23 

80 
8.0 
29 

70 
5.8 
21 

60 
5.9 
21 

50 
1.8 
6 



Total: 
28 
100 

Average ball weight 
[ g ] 
1665 

Spec. media surface 
[m2 / t] 
9.7 

Volume Load 
[%] 
34.0 

Second Chamber Ball 






Ø Ball [mm] 
Weight [ t ] 
Percent [%] 



50 
8 
8 

40 
7 
7 

30 
6 
6 

25 
22 
22 

20 
55 
56 







Total: 
98 
100 

Average ball weight 
[ g ] 
46 

Spec. media surface 
[m2 / t] 
32.7 

Volume Load 
[%] 
31.3 

The longitudinal sieve analysis is as follow:
Using the Clk sieve analysis I calculated that the maximum ball required will be:
INPUTS: (Input Shaded Area Values) 

Wi = 
13.49 
s = 
3.09 
D_{80} = 
11000.00 
D = 
3.22 
Mill Speed 
17.20 
K= 
335.00 
Calculated Values: 

Critical Speed = 
23.57 
Pc = 
72.97 
Can you please tell me your opinion the mill charge composition and longitudinal analysis?
Should the mill feeling degree be decreased? What about the max ball used?
How can we increase production in this mill?
I appreciate all your comments and feedback.
Thx
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5 posts
Re: Request for feedback for a Two Chamber Cement Mill Ball Charge and Longitudinal Sieve Analysis
Dear Fjalali:can you send us your email in order we can get the excel sheets to do a better analysis. Then we can answer you here in the forum.
Have a great day.
Ariel
138 posts
Re: Request for feedback for a Two Chamber Cement Mill Ball Charge and Longitudinal Sieve Analysis
fjalali,
When editing your post, you can add attachments. Excel files with your data as well as drawing would be useful. You can do that using the option tab. The upload popup screen is cluttered with advertising and looks a bit crazy, but it works. Attaching files could be very useful. Large table are difficult to read on this forum, again because too much space of the screen is reserved for advertising.
Concerning you question, these additional information could be useful:
 is it an opencircuit ball mill or a closedcicuit?
 are you using steel balls or ceramic balls?
(could be ceramic sometimes for white cement)  are you producing one main product or
are you producing several different products?  eventually, what kind of separator is being used?
how does the separation curve looks like,
how much is the bypass ratio,
circulating load, ....  what is the (main) product being produced?
what are the raw materials and the recipe?
what is the fineness of the cement
particle size distribution of the cement, ...  are you using grinding aids?
 what are the temperatures in the grinding circuit?
 if it is a closed circuit, could you provide the
particle size distribution of the separator feed, reject, product?  what is the current power consumption and hourly production
and what is the current rotation speed?  It could be also useful to explain the symbols you are using!
Is D80 related to the feed or the product?
Some people write P80 when it is the product and F80 for the feed !
What do you mean by Pc, for example?
What are s or K?
Also show all the units in your data, I guess D80 is in µm?
What do you call "critical speed", and what are the units?  Would should also provide the formulas you are using.
Attaching an Excel file would be the easiest way.
Thanks,
Michel
Maybe you could enjoy reading this:
http://www.docentes.utonet.edu.bo/njacintoe/wpcontent/uploads/Grinding_Fundamentals.pdf
http://www.mineraltech.com/MODSIM/ModsimTraining/Module6/Grinding.pdf
www.smartdogmining.com/tools/SDM%20Mill%20Calcs.xls
www.uc.cl/sw_educ/simula/excel/Ballsim_Direct.xls
77 posts
Re: Request for feedback for a Two Chamber Cement Mill Ball Charge and Longitudinal Sieve Analysis
As per your given mill details.(mill output assumed to be 45 tons / hr) for more details you can contact me at vikprocem@gmail.com
It is not so easy to understand the cement plant without being present at site. But, still according to my calculations
 The size of your first chamber grinding media seems to be more.
 Max ball size should be upto 70 mm
Data Entry  Yellow cell
VIKpromill  
Data Entry  
Mill tube Length Mts.  11.00  
Mill tube Dia. Mts.  3.4  
Mill liner size Mts.  0.14  
Partition Wall size Mts.  0.7  
Nos of partition  1  
First comp. Length ( effect) Mts.  2.3  
First Comp. Useful Mill Dia. Mts  3.23  
Second comp. length ( effect) Mts.  8  
Second Cmp.Useful Mill Dia. Mts  3.27  
Third comp. length ( effect) Mts.  0  
Third Comp. Useful Mill Dia. Mts  0  
Mill RPM  17.2  
Size in microns, 80% of mill feed pass F  11000  
Bond's works index of mill feed, size Wi  13.49  
Specific gravity of mill feed. S  3.09  
Volume of first Comp. M3  18.84  
Power demand cal. 1st Comp  399  
Volume of second Comp.M3  67.15  
Power demand cal. 2nd Comp  1389  
Volume of third Comp.M3  0  
Power demand cal. 3rd Comp  0  
Power demand total. Kw ( Aprox)  1824  
Useful Mill Length Mts  10.3  
Material retaintion time min  6.3  
Mill Critical Speed  23.54  
Mill speed of critical speed %  73.07  
First compartment  
% of filling first compartment  32.7  % 
Grinding Area of first Comp. %  21.9  % 
Compartment Volume M3  18.8  M3 
Total Bulk Weight of balls  28.5  tons 
Bulk density of all balls.  4.631  t /d m3 
Bulk Volume  6.2  M3 
Total Numbers of Balls  34559  #s 
Nos. Of ball impact/ revolution.  61861  Impacts 
Nos of Ball impact / sec  17733  Impacts 
Material retaintion time ( min )  1.41  min 
Average Ball Weight  0.8  kg 
Ball Surface/Comp. Volume Ratio  27.1  
Second compartment  
% of filling second compartment  29.8  % 
Grinding Area of second Comp. %  78.1  
Compartment Volume M3  67.15  m3 
Total Bulk Weight of Balls  98.0  tons 
Bulk density of balls.  4.89  t / dm3 
Bulk Volume  20.03  m3 
Total Numbers of Balls  3564486  #s 
Nos. Of ball impact / revolution.  6380430  Impacts 
Nos of Ball impact / sec  1829057  Impacts 
Material retaintion time ( min )  4.89  min 
Average Ball Weight  0.027  kg 
Ball Surface/Comp. Volume Ratio  80.0 