1. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
REPORT
Scope
Determination of pre-homogenization factor of limestone homogenization pile
and calculation of layers of limestone and clay piles
Methodology
• Methodology used consists in taking sufficient samples during pile
construction and chemically analyzing all the samples and calculating the
LSF standard deviation. Applying the same logic, we collected sufficient
samples during pile reclaiming to the raw mill silos and chemically analyzed
samples and determined the LSF standard deviation.
• By dividing the LSF standard deviation before pile creation and LSF standard
deviation during consumption we determine the pre-homogenization
factor.
• For determination of the number of layers per pile, we measured for
relatively long periods (up to 3 hours), the time that the stacker needs to
travel from one extreme to the other extreme of the pile. We performed
this exercise for different stacker speeds and calculated the number of
layers for various crusher capacities.
Description of the work
Determination of pre-homogenization factor for limestone pile – preparatory work
- On 23 August 2012, during construction of pile A, since the beginning of the
pile, we took spot samples each hour from 09:00 to 21:00.
- The samples were taken from the belt conveyor right after the crusher by
crash stopping it (pulling rope switch). We attempted to take as a
representative sample as possible by taking the whole cross section of the
belt conveyor for about 30cm length. Then the spot samples were taken to
laboratory for chemical analysis.
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2. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
- On 24 August 2012 we continued sample taking until the pile was filled up.
- On 27 August 2012 we took spot samples when raw mill was operating and
the samples were taken directly from the limestone feeder chute. The
samples were taken every 2 hours and later sent to laboratory for chemical
analysis.
- Sample taking from limestone weight feeder continued for 2 more days
until the pile was consumed and changed to new pile.
Determination of number of layers for limestone and clay piles
Limestone pile
- On 17 August 2012 we measured the time that needs the stacker to create
one layer, while the stacker speed was 30% and then while stacker speed
was 40%. Then we calculated how many layers the stacker can create until
the pile is filled up. We measured the time during construction of pile A.
- On 21 August 2012 we performed the same exercise on LIMESTONE
STORAGE for pile B
For PILE A:
While stacker speed is 30 % it takes 8’30” to create one layer and for
stacker speed 40 % it takes 6’30” to create one layer.
- While knowing that:
Q= 20 000ton; q=650 t/h;
For stacker speed 30% we have the results that stacker create 210 layers.
For stacker speed 40% we have the results that stacker create 270 layers.
For PILE B:
While stacker speed is 30 % it takes 7’8” to create one layer and for stacker
speed 40 % it takes 5’8” to create one layer.
- While knowing that:
Q= 20 000ton; q=650 t/h;
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3. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
For stacker speed 30% we have the results that stacker create 240 layers.
For stacker speed 40% we have the results that stacker create 300 layers.
Capacity Stacker speed (%)
t/h 30 40
Pile A (650) 210 270
Pile B (650) 240 300
Flysch pile
- On 29 August 2012 we measured the time that needs the stacker to create
one layer. We measured for a period of 3 hours.
- After calculation we have the results that stacker needs 3’26” to create one
layer.
While knowing that:
Q= 4000ton; q=217 t/h; t=3’26”
For stacker speed 50%we have the results that stacker create 322 layers.
- On 30 August 2012 we measure the time that needs stacker to create one
layer, while the stacker speed is 55 % and 60 %.And the results are for
stacker speed 55 % it takes 3’07” to create one layer and for stacker speed
60 % it takes 2’52” to create one layer.
- We measured the time that needs stacker to create one layer for different
speeds. In the table below we have the calculation about the numbers of
layers for a pile for different capacity, different times and different stacker
speeds.
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4. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
Capacity
t/h
Stacker speed (%)
50 55 60
210 333 366 398
215 325 357 328
217 322 354 385
220 318 350 380
CALCULATIONS
Determination of LSF standard deviation for limestone pile by using chemical
data of the samples.
According to lab analysis, the average chemical data of the samples before pile
construction are as below (average values and standard deviation):
Moisture SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 LSF SM AM
AVE
0.76 1.73 1.11 0.52 53.85 0.44 0.08 0.01 0.44 2614.33 1.14 1.94
STDEV
0.18 0.35 0.14 0.07 0.34 0.00 0.02 0.00 1.51 623.79 0.15 0.07
Meanwhile, the chemical data of the sample during consumption are as follows
(average values and standard deviation):
Moisture SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 LSF SM AM
AVE 0.86 1.49 0.89 0.42 54.43 0.43 0.02 0.01 0.31 1526.65 1.14 2.10
STDEV 0.60 0.28 0.18 0.08 0.54 0.01 0.01 0.00 0.01 560.23 0.01 0.05
By dividing the standard deviation before and after the pile creation we get the
pre-homogenization factor (HFactor):
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5. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
Hfactor=STDEV before pile construction/STDEV during
consumption=623.79/560.23=1.11
CONCLUSIONS
1. The most important factors that influenced the low homogenization factor are:
a) Preparation of the representative sample. Lack of an appropriate crusher
just for raw materials means the amount of sample and pre-mixing of the
sample to take a representative sample left a lot of room for error.
b) The amount of sample should be increased in order to be sufficiently
representative.
c) The point where we took samples during the consumption should be the
same with the point we took samples before construction of the piles (it
mean to take samples by stopping the belt conveyer before reaching the
limestone silo).
2. The number of layers on pile on limestone storage it’s too low to achieve
appropriate homogenization.
3. For not too high capacity (lower than 210t/h) the actual stacker speed (50 %)
achieves sufficient number of layers at the clay pile.
4. Target of layers in both piles A and B can be achieved if:
a) We increase stacker speed where applicable
b) We decrease the capacity of the crusher within acceptable values.
SUGGESTIONS
• We suggest repeating the test by taking into consideration the findings in
the conclusions above.
• To perform the test for flysch pile as well to have a picture of the pre-
homogenization achieved.
• To increase stacker speed min 55% for Flysch
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6. DETERMINATION OF PRE-HOMOGENIZATION FACTOR
03.09.2012
• To iIncrease stacker speed min 50% for Limestone
Prepared by
Doris BULKU
Bachelor of Geo-Mining Engineering
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