Scope: Determination of pre-homogenization factor for limestone pile – preparatory work

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.

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By dividing the LSF standard deviation before pile creation and LSF standard deviation during consumption we determine the pre-homogenization factor.

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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

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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.

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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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DETERMINATION OF PRE-HOMOGENIZATION FACTOR 03.09.2012

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On 24 August 2012 we continued sample taking until the pile was filled up.

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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.

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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

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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.

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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.

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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.

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While knowing that: Q= 20 000ton; q=650 t/h;

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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

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On 29 August 2012 we measured the time that needs the stacker to create one layer. We measured for a period of 3 hours.

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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.

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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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DETERMINATION OF PRE-HOMOGENIZATION FACTOR 03.09.2012

Stacker speed (%)

Capacity t/h

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):

 AVE STDEV

Moisture

SiO2

Al 2O3

Fe2O3  CaO

MgO

K 2O

Na2O

SO3

LSF

SM

AM

0.76

1.73

1.11

0.52

53.85

0.44

0.08

0.01

0.44

2614.33

1.14

1.94

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):

 AVE

Moisture 0.86

SiO2 1.49

Al 2O3 0.89

Fe2O3  CaO 0.42 54.43

MgO 0.43

K 2O 0.02

Na2O SO3 LSF 0.01 0.31 1526.65

SM 1.14

AM 2.10

STDEV

0.60

0.28

0.18

0.08

0.01

0.01

0.00

0.01

0.05

0.54

0.01

560.23

By dividing the standard deviation before and after the pile creation we get the pre-homogenization factor (H Factor):

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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.

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To perform the test for flysch pile as well to have a picture of the prehomogenization achieved.

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To increase stacker speed min 55% for Flysch

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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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