fjalali 15/06/2011 10:36:15

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*
D₈₀ =	*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

Lafecapo 15/06/2011 12:44:01

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

lalbatros 16/06/2011 07:17:07

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 open-circuit ball mill or a closed-cicuit?
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/wp-content/uploads/Grinding_Fundamentals.pdf

http://www.mineraltech.com/MODSIM/ModsimTraining/Module6/Grinding.pdf

http://www.fivesgroup.com/FivesFcb/EN/Expertise/Documents/Grinding%20plants-Optimization%20and%20modelling.pdf

www.smartdogmining.com/tools/SDM%20Mill%20Calcs.xls

www.uc.cl/sw_educ/simula/excel/Ballsim_Direct.xls

Vikpro 17/06/2011 12:36:35

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

VIK-promill
VIK-promill
Data Entry
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