Document 4p3RMZ30yYwa1g6M88EN4Z61
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EVALUATION OF THE BONA DUST FILTER GREAT NOLIGWA MINE
7 March 2003
JJ Dekker O-ESH Manager Occupational Hygiene South African Region Central O-ESH Team
PURPOSE
To evaluate the dust filtering efficiency of the Bona Dust Filter. Both dust mass filtering efficiency and dust particle filtering efficiency was evaluated.
METHODOLOGY
Project was conducted at the Bona Dust Filter installation on Great Noligwa Mine. This unit is currently installed at the 76 Level station tips.
Two AEROCET 531 particle mass and count instruments were utilised to determine the filtering efficiency of the Bona Dust Filter.
Samples were collected at: The intake to the dust filter, The return of the dust filter, and The return of the side extraction bag.
Samples were collected during tipping and non-tipping activities.
The pressure over the filtration unit was also measured before the dust filtrating efficiency tests commenced and on completion of the dust filtrating efficiency tests.
FINDINGS
The detailed results of the tests are depicted in Appendix A.
Particle filtrating efficiency
The overall particle filtrating efficiency ranged from 14,4% to 53,4% (average of 36,8%) when there was no tipping being done. The highest efficiency occurred in the > 5 ^m category (19,7 to 56,1 % with an average of 25,3% filtrating efficiency). The filtrating efficiencies in the in the 0,5 to 5 category ranged from 10,1 to 50,7 %, with an average filtrating efficiency of 20,3%.
During tipping operations the particle filtrating efficiencies ranged from 66% (0,5 to 5^m category) to 88% (> 5|j,m category) with an overall particle efficiency of 69%.
The particle filtrating efficiencies for the side extraction bag ranged from 84% (0,5 to 5^m category) to 93% (> 5|j,m category) with an overall particle efficiency of 85%.
Dust mass filtrating efficiency
The overall dust mass filtrating efficiency ranged from 10% to 59% (average of 45%) when there was no tipping being done. The highest efficiency occurred in the PM1 category (10 to 90 % with an average of 78% filtrating efficiency).
During tipping operations the overall dust mass filtrating efficiencies ranged from 45% (PN2.5 category) to 74% (PM7 category) with an overall mass efficiency of 66%.
The mass filtrating efficiencies for the side extraction bag ranged from 50% (PM1 category) to 98% (PM7 and PM10 categories) with an overall mass efficiency of 98%.
Pressure
The pressure over the Bona Dust Filter reduced with 8,1% (from 740 Pa at start of tests to 680 Pa at end of tests).
Replacement period
The estimated replacement period for the secondary and tertiary filters could not be calculated at this stage. Test results on the primary filter filtrating efficiency and dust holding capacity is required, before the calculation can be done.
CONCLUSION
Although the Bona Dust Filter rendered relative good dust filtering efficiencies at the beginning of the tests (53% overall dust particle-filtering efficiency and 59% overall dust mass filtering efficiency) these efficiencies deteriorated as the tests progressed. Overall dust particle filtering efficiency decreased by 39% (from 53% to 14%) and overall dust mass filtering efficiency decreased by 49% (from 59% to 10%).
This decrease in efficiency is mainly due to the leakage's that occurs within the dust filter unit and were confirmed by the system pressure that also decreased by 8,1%.
During inspection (conducted directly after tests were completed) it was identified that the sealing material does not form a proper seal at all the identified areas and collapses due to vibrations from the fan and filter units inside the Bona Filter.
RECOMMENDATIONS
The sealing material must be replaced with a more robust material that could withstand the forces present inside the Bona Dust Filter.
Areas that are not properly sealed (as demonstrated to the Universal Engineering Representative who accompanied us during the visit) must be rectified.
The supplier must forward the dust filtrating efficiency and dust holding capacity tests results for the secondary filter to Great Noligwa Mine O-ESH Department.
The entire test must be repeated, once all the recommendations (as indicated above) have been completed.
APPENDIX A - Test Results
Location
No Tipping 1 No Tipping 2
Average
T ipping
Side Extraction Bag
BONA FILT ER UNIT (Particle Count Evaluation)
INTAKE
RETUJRN
EFFICIE NCY
0.5 u > /Litre
5.0 u > /Litre
0.5 u > /Litre
5.0 u > 0.5 u > 5.0 u > /Litre /Litre /Litre
Overall /Litre
468975
13902
231222 6105 50.7 56.1
53
346595
8807
311443 7072 10.1 19.7
14
271857 7570 180888 4392 20 25
37
434736
27066 147604 3373 66.0 87.5
69
271857
7570
42845
547 84.2 92.8
85
Location
No Tippinq 1 No Tipping 2
Average
BONA FILTER UNIT (Particle Mass Evaluation)
INTAKE
RETURN
EFFICIENCY
PM 1.0 PM 2.5 PM 7.0 PM TSP PM 1.0 PM 2.5 PM 7.0 PM 10.0 TSP PM 1.0 PM 2.5 PM 7.0 PM 10.0 mg/m3 mg/m3 mg/m3 10.0 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3 mg/m3
mg/m3
0.01 1.01 7.906 9.017 10.502 0.009 0.464 2.468 3.099 3.664 10
54
69
61
0.059 0.8 3.24 3.652 4.279 0.006 0.159 2.594 3.002 3.304 90
80
20
7
0.035 0.905 5.573 6.335 7.391 0.008 0.312 2.531 3.051 3.484 78
66
55
45
TSP mg/m3
59 10 45
T ipping
0.029 0.629 4.246 4.973 5.626 0.015 0.347 1.087 1.314 1.685 48
45
74
69
66
Side Extraction Bag 0.008 1.189 8.349 9.889 10.4 0.004 0.038 0.151 0.197 0.229 50
97
98
98
98
Pressure over Bona Dust Filter Unit:
Start of tests = 740 Pa End of tests = 680 Pa
Ventilating air quantity through Bona Dust Filter Unit = 4,0 m3/s
Number of filtration units inside Bona dust Filter = 8 units
100
90
80
70
xo 60
S'
50 u
it
40
30
20
10
0
No Tipping
A 50 7
56.1
4w ini
25.3
mi
0.5 u >
5.0 u >
BONA DUST FILTER EVALUATION (Particle Filtrating Efficiency) Tipping
88
i 53.4
1 36.8
66
69
1 14.4
Overall
0.5 u >
5.0 u >
Overall
Max Min Average
Side Extraction Bag 93
84 85
0.5 u >
5.0 u >
Overall
BONA DUST FILTER EVALUATION (Mass Filtrating Efficiency)
No Tipping 120
Tipping
Side Extraction Bag
100 97 98 98 98
90
80 1 78
on
74
vP
>Oc 60
CD 'u
LiUt
4 k 66 4 69
61 59
1 54 4 55
48
4 45 | 45
45
69 *66 50
40
20 on
1 10
| 7 10
0 PM 1.0 PM 2.5 PM 7.0 PM 10.0 TSP
PM 1.0 PM 2.5 PM 7.0 PM 10.0 TSP
Max BMin Average
PM 1.0 PM 2.5 PM 7.0 PM 10.0 TSP