ISSN (0970-2083)

ON DUST AND GAS GENERATION UPON MULTIPLE BLASTS IN OPEN-PIT MINES

Gennady Petrovich Paramonov* and Vladimir Nikolayevich Kovalevskyi

Saint-Petersburg Mining University, 21 line, 2, Saint-Petersburg, 199106 Russia

Corresponding Author:
Gennady Petrovich Paramonov
E-mail:
mihmarinin@yandex.ru

Received date: April 06, 2017; Accepted date: April 08, 2017

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Abstract

This article discusses the influence of explosive charge diameter and type of explosive substance on generation of fine dust. Dependences of dust generation intensity for various size fractions and dust concentration upon blasting for operation conditions of open-pit mines of building materials. Calculation procedures of dust and gas pollutions upon blasting operations are reviewed and analyzed. Sample calculation of dust and gas pollution according to the proposed procedure is given with consideration of gas dynamic processes in blasthole charging pocket, blasting and drilling parameters, properties of explosive substances and rock massif, including results of commercial approbation in open-pit mines of building materials. Results of commercial experiment are given, the known calculation procedures of dust and gas emissions upon blasting and drilling operations in open-pit mines are analyzed.

Keywords

Dust, Concentration, Explosive charge, Explosive charge diameter, Detonation velocity, Open-pit mine, Blast, explosion

Introduction

In Huge amounts of dust and gas are emitted into environment upon multiple blasts. The amount of explosive charge for multiple blasts in openpit mines reaches 300 t to 1000 t, and the weight of blasted rocks amounts to 5 million t. According to particle size distribution of blasted rocks of various strength it is established that in terms of 1 kg of explosive substance upon multiple blasts the dust and gas cloud contains from 80 g to 320 g of 20 μm size fraction (Adushkin, 1996). It has been shown in Beresnevich and Mikhailov, 1990; that specific amount of dust per unit of rocks depends on rock strength and increases with increase in mining depth and varies in the range of 30 g/m3 to 160 g/m3.

Experimental

Nowadays several procedures for calculations of dust and gas environmental pollutions upon multiple blasts in open-pit mines are known, such as the procedure for calculations of harmful emissions (effluents) for open-pit mining (on the basis of specific performances) developed in Skochinsky Mining institute (Procedures of calculation of harmful emissions (effluents) for equipment of open-pit mines (on the basis of specific performances, 1990), Unified Program of air pollution estimation, Ecolog, ver. 3 (Integral Company), Mining operations, ver. 1.1.0.4 (Integral Company), and others. The software packages Ecolog, ver. 3.00 and Mining operations, ver 1.1.0.4 (Integral Company) are based on the procedures in procedures of calculation of harmful emissions (effluents) for equipment of openpit mines (on the basis of specific performances, 1990), however, they do not take into account energy properties of explosive substances (ES) and their detonation velocities, drilling and blasting parameters (borehole diameters and their amount, explosive charge weight in borehole). A procedure is discussed in (Menzhulin and Paramonov, 1997) which calculates dust size fractions generated in near zone of blast with accounting for the use of various explosive charge designs, ES types and properties of blasted massif. This procedure is based on the theory of destruction including kinetics of accumulation of induced fracturing resulted from blasting loads on rock massif with consideration for gas dynamic processes in explosive charge pockets, detonation properties of fractured rocks. This procedure is implemented in Dust software developed by Saint Petersburg Mining Institute. it should be mentioned that this procedure accounts for dust generation only in near zone of blast and does not account for dust generation due to additional crushing upon rock displacement.

This work proposes calculation procedure of dust generation with consideration for peculiar features of the above listed procedures, as well as reveals dependences estimating dust and gas emissions upon blasting of various ES on the basis of known blast parameters of ammonites: the most popular explosives for drilling and blasting.

The amount of pollutants emitted upon blasting in open-pit mines was determined in the course of experiments performed at OAO Kamennogorsk department of open-pit mines and ZAO Gavrilovskoe department of open-pit mines, Leningrad oblast. The experiments were performed with granite and granite gneiss, their Protodyakonov strength coefficient varies in the range of 12-14.

In order to approbate the calculation procedure with regard to conditions of Kamennogorsk deposit model experiments were performed with rock samples (Larichev, et al., 2009). Convergence of results of laboratory tests, calculations, measurements of dust and gas emissions (Procedures of calculation of harmful emissions (effluents) for equipment of openpit mines (on the basis of specific performances, 1990; Menzhulin and Paramonov, 1997; Larichev, et al., 2009a; Larichev, et al., 2010; Shmeleva, et al., 2006), obtained upon pilot multiple blasts, makes it possible to apply them for estimation of new ES types, to forecast polluting emissions upon blasting using boreholes of various diameters in deposits and open-pit mines, as well as to apply the proposed procedure in counter-explosive criminalistics for identification of ES type and weight on the basis explosion products, weight and size fractions of dust.

Numerical calculations (Larichev, et al., 2009) of dust generation according to the procedure in (Menzhulin and Paramonov, 1997), developed in Saint Petersburg Mining institute, confirmed their convergence with experimental data on the basis of weight estimation by size fractions generated upon blasting of borehole charges.

Results

Analysis of experimental and calculated data Tables 1-4 using the procedures (Procedures of calculation of harmful emissions (effluents) for equipment of open-pit mines (on the basis of specific performances, 1990; Menzhulin and Paramonov, 1997) in (Larichev, et al., 2009; Larichev, et al., 2009a; Larichev, et al., 2010) and measurements of harmful pollutions (Shmeleva, et al., 2006) by OAO Kamennogorsk department of open-pit mines demonstrates that the dust amount generated upon blasting and calculations differ by not more than 15%, which confirms possibility of the developed procedure to estimate dust and gas generation.

ES type Protodyakonov
strength
coefficient
ES density,
kg/m3
D, m/s dBore ,
10−3 m
Gas emission
coefficient for
ammonite
equation
Dust emission
coefficient for
ammonite
equation
Ammonite No. 6 ZhV 12-14 950 4500      
252 1 1
220 0.947 0.663
165 0.614 0.606
130 0.682 0.586
112.5 0.666 0.423
75 0.833 0.165
1200 5300 252 1.384 1.403
220 1.313 1.065
165 0.852 0.912
130 0.945 0.831
112.5 0.923 0.598
75 1.155 0.233
Grammonite 79/21 870 4300 252 0.698 0.907
220 0.920 0.616
165 0.596 0.549
130 0.590 0.530
112.5 0.647 0.388
75 0.810 0.151
1200 4800 252 1.342 1.156
220 1.276 0.770
165 0.826 0.685
130 0.921 0.642
112.5 0.898 0.493
75 1.123 0.194
Sibirite 1000 5080 252 0.346 0.355
220 0.324 0.197
165 0.213 0.185
130 0.234 0.177
112.5 0.229 0.130
75 0.287 0.050
1200 6000 252 0.473 0.445
220 0.450 0.290
165 0.293 0.269
130 0.324 0.256
112.5 0.317 0.183
75 0.396 0.058

Table 1. Universal coefficients of dust and gas emissions

 ES type  ES density, kg/
m3
 D, m/s  dBore , 103m  Calculated dust weight
kg /1kg ES
 Calculated gas weight
kg /1kg ES
Ammonite No. 6 ZhV 950 4500 252 0.110 0.063
220 0.073 0.060
165 0.067 0.039
130 0.064 0.043
112.5 0.047 0.042
75 0.018 0.052
1200 5300 252 0.154 0.087
220 0.117 0.083
165 0.100 0.054
130 0.091 0.060
112.5 0.066 0.058
75 0.026 0.072
Grammonite 79/21 870 4300 252 0.099 0.044
220 0.068 0.058
165 0.060 0.038
130 0.058 0.037
112.5 0.043 0.041
75 0.017 0.051
1200 4800 252 0.127 0.085
220 0.085 0.080
165 0.075 0.052
130 0.071 0.058
112.5 0.054 0.056
75 0.021 0.071
Sibirite 1000 5080 252 0.039 0.022
220 0.022 0.020
165 0.020 0.013
130 0.019 0.015
112.5 0.014 0.014
75 0.005 0.018
1200 6000 252 0.049 0.030
220 0.032 0.028
165 0.030 0.018
130 0.028 0.020
112.5 0.020 0.019
75 0.006 0.025

Table 2. Dust and gas emissions after blasting of 1 kg ES

Explosive substance Brisancy, mm Fugacity, cm3 Detonating velocity, m/s Density, g/cm3 Heat of explosion, kJ/kg Trinitrotoluene equivalent
Tetranitropentaerytrite 16 500 7520 1510 5800 1.37
Ammonite No. 6ZhV 14 360 4500 950 4355 1.03
Grammonite 79/21 25 360 4300 870 4300 1.02
Sibirite 1200 17 400 6000 1200 4100 0.96
Trinitrotoluene 16 285 6600 1660 4228 1
Plastic explosive (PE-4) 21 280 7000 1440 5440 1.28
Hexogen 24 470 8380 1800 5500 1.3

Table 3. Properties of some explosive substances

Protodyakonov strength coefficient Specific dust emission (qD , kg/m3), according to Skochinsky Mining Institute Adjustment rock strength coefficients Specific dust emission (qD , kg/m3), according to Skochinsky Mining Institute Adjustment rock strength coefficients
For emulsified ES For water-free ES
2-4 0.015 0.3-0.33 0.03 0.27-0.33
4-6 0.02 0.4-0.44 0.04 0.36-0.44
6-8 0.025 0.5-0.55 0.05 0.45-0.55
8-10 0.03-0.04 0.66-0.8 0.06-0.08 0.66-0.72
10-12 0.04-0.045 0.89-0.9 0.08-0.09 0.81-0.88
12-14 0.045-0.05 1 0.09-0.11 1
14-16 0.05-0.06 1.11-1.2 0.11-0.13 1.18-1.22
16-18 0.06-0.08 1.33-1.6 0.13-0.16 1.44-1.46

Table 4. Adjustment rock strength coefficients of dust emission as a function of rock strength for water free ES and emulsified ES

1. Example of calculations of harmful emissions resulted from ammonite No. 6 ZhV using the procedure (Procedures of calculation of harmful emissions (effluents) for equipment of open-pit mines (on the basis of specific performances, 1990), of Skochinsky Mining institute for conditions of OAO Kamennogorsk department of open-pit mines in terms of single blast of 30 t ES, dBore = 252 mm , 950 / 3 ρES = kg m . The Protodyakonov strength coefficient of granite is in the range of 1 2-14.

Weight of harmful gases (carbon oxide, nitrogen oxides), emitted with dust and gas cloud (DGC):

equation

Weight of harmful gases remaining in blasted rock mass (RM) and gradually released into environment:

equation

Calculation of total weight of harmful gases emitted upon blast (in terms of conventional CO ):

equation

Weight of solid particles (dust) emitted with DGC:

equation

equation

Total weigh of harmful substances emitted upon single blast:

equation

Total weigh of harmful substances emitted upon single blast:

equation

All coefficients Table 1 were calculated using the procedure in Menzhulin and Paramonov, 1997, which enable forecasting of dust and gas weights upon the use of various explosive boreholes, various types of ES with various detonation velocities and density.

Therefore, it would be reasonable to introduce the notions of ammonite dust equivalent and ammonite gas equivalent similar to trinitrotoluene equivalent, that is, amount (weight) of dust and gas after blasting of ammonite No. 6ZhV (density 950 kg/m3, detonation rate 4500 m/s) as one of the most widely used ES in open-pit mines.

equation is the coefficient of gas emission in terms of ammonite No. 6ZhV (density 950 kg/m3, detonation velocity 4500 m/s); equation is the coefficient of dust emission in terms of ammonite No. 6ZhV (density 950 kg/m3, detonation velocity 4500 m/s).

Therefore, in order to determine the amounts of gas and dust emitted upon blast it is required to calculate the amounts of dust and gas using Eqs. 1.1- 1.6 for ES: ammonite No. 6ZhV (density 950 kg/m3, detonation velocity 4500 m/s), and then to multiply by equation or equation , respectively.

Dust and gas emissions upon ES blasting in terms of 1 kg ES are summarized in Table 2.

The data are given for dust dN ≤ 300 μm according to the proposed procedure.

Using the data in Table 3 it is possible to interrelate the ES trinitrotoluene equivalent with dust or gas equivalents.

When ammonite No. 6ZhV with the density of 950 g/cm3 is used as ES, the emissions of dust with size fraction of dÍ ≤ 300 μm are 0.11÷0.018 kg/1 kg ES. Taking into account that 1 kg of ammonite No. 6 ZhV in terms of energy=1.03 kg of trinitrotoluene, upon blasting of 1 kg of trinitrotoluene with the density of 1660 g/cm3 the emissions of dust with size fraction of dÍ ≤ 300 μm are 0.1068÷0.017 kg/1 kg ES, hence, the proposed procedure can be applied in blasting technique upon determination of ES weight and composition.

In order to calculate dust and gas emissions in rocks with strength differing from that of granite (Protodyakonov strength coefficient of 12-14) it is required to apply conversion rock strength coefficients of dust emission summarized in Table 4.

Discussion

Therefore, it is possible to estimate the difference in dust emissions under identical conditions varying only by strength of blasted rocks. For instance, 141.68 t of dust are generated at OAO Kamennogorsk department of open-pit mines in one year, provided that Protodyakonov strength coefficient of granite rocks varies in the range from 12 to 14, and in the case of rock blasting with the strength of 8-10 the dust emissions are 93.5 t/year to 113.344 t/year.

Table 5 illustrates application of ammonite dust and gas equivalents, as well as summarizes emitted amounts of dust and gas upon multiple blasts of various ES and borehole diameters.

 ES
type
 ES
density,
kg/m3
 D,
m/s
 dBore ,
10−3 m
 Calculated
dust weight *
103 kg / year
 Calculated
dust weight **
103 kg / year
 Calculated dust
weight ***
103 kg / year
 Experimental
dust weight
103 kg / year
 Calculated gas
weight
103 kg / year
Ammonite No. 6 ZhV 950 4500 252 59.81 118.8 118.8 141.68 67.68
220 39.46 78.8 64.08
165 36.25 72.0 41.58
130 35.09 69.6 46.14
112.5 25.30 50.2 45.05
75 9.89 19.6 56.38
1200 5300 252 83.95 166.6 93.84
220 63.74 126.5 88.85
165 54.54 108.3 57.65
130 49.73 98.7 63.98
112.5 35.76 71.0 62.46
75 13.96   27.7   78.18
Grammonite 79/21 870 4300 252 54.24 107.8 107.8 129.70 65.52
220 36.86 73.2 62.28
165 32.85 65.2 40.32
130 31.72 63.0 45.00
112.5 23.23 46.1 43.81
75 9.02 17.9 54.82
1200 4800 252 69.12 137.3 90.85
220 46.08 91.5 86.36
165 40.95 81.4 55.91
130 38.42 76.3 62.40
112.5 29.47 58.6 60.75
75 11.61 23.0 76.01
Sibirite 1000 5080 252 76.56 42.2 42.2 50.76**** 23.40
220 49.72 23.4 21.96
165 45.68 21.9 14.40
130 40.04 21.0 15.84
112.5 32.92 15.4 15.48
75 12.67 5.94 19.44
1200 6000 252 107.91 52.9 64.06**** 32.04
220 71.74 34.5 30.45
165 66.74 32.0 19.80
130 63.33 30.4 21.96
112.5 46.08 21.7 21.44
75 14.49 6.8 26.83

Table 5. Experiments and calculations

Aiming at estimation of emitted dust with regard to size fractions for Kamennogorsk open-pit mines the weights of dust after blasting of various ES were calculated using the procedure (Menzhulin and Paramonov, 1997), it was established that the 0-300 size fraction is emitted in amount of 110.69 t. The ratios of dust size fractions in DGC (the data are comprised of dust contents after blasting of ammonite No. 6ZhV, grammonite 79/21, sibirite-1000 with the densities of 950, 870, and 1000 kg/m3, respectively), are summarized in Table 6.

  Quantitative composition of dust, %
Size fraction 0-40 Size fraction 40-75 Size fraction 75-150 Size fraction 0-150
Average 0.182 3.185 96.63 100
For ammonite No. 6ZhV 0.283 3.305 96.41 100
For grammonite 79/21 0.145 2.979 96.87 100
For sibirite -1000 0.118 3.268 96.61 100
  Quantitative composition of dust, %
Size fraction 0-150 Size fraction 150-300 Size fraction 0-300
Average 54.030 45.968 100
For ammonite No. 6ZhV 53.885 46.113 100
For grammonite 79/21 53.686 46.312 100
For sibirite -1000 54.519 45.479 100

Table 6. Comparison of dust fractions in dust and gas cloud upon blasting by various ES

Data analysis demonstrates that when ammonite No. 6ZhV with the density of 950 kg/m3 is used as ES the dust size fractions 0-40, 40-75, 75-150 are emitted in amount of 0.0109, 0.191, and 57.794 t/year, respectively, and the dust size fractions 0-150, 150-300 in amount of 59.81 and 50.886 t/year, respectively.

Table 7 summarizes quantitative composition of dust after blasting of ammonite No. 6ZhV with the density of 950 g/cm3 at DBore = 252 mm on the basis of procedure (Menzhulin and Paramonov 1997).

equation Quantitative composition of dust, %
Size fraction 0-40 Size fraction 40-75 Size fraction 75-150 Size fraction 0-150
1 0.044 0.33 6.54 6.91
2 0.053 0.36 8.81 9.22
3 0.033 0.40 10.37 10.80
4 0.032 0.41 10.57 11.01
5 0.031 0.35 10.77 11.15
6 0.026 0.34 10.54 10.91
7 0.017 0.31 9.90 10.23
8 0.016 0.29 9.87 10.18
9 0.014 0.27 9.57 9.85
10 0.013 0.25 9.47 9.73

Table 7. Quantitative composition of dust after blasting of ammonite No. 6ZhV with the density of 950 g/cm3 at 252 DBore = mm

Conclusions

Therefore, this work analyzed known calculation procedures of dust and gas emissions upon drilling and blasting. It is proposed to estimate the dust and gas emissions using ammonite dust and gas equivalents. The proposed method makes it possible to estimate environmental situation at drilling and blasting sites for various ES and blasting conditions.

References

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Beresnevich, P.V. and Mikhailov, V.A. 1990. Aerology of open-pit mines, Guidebook. Moscow: Nauka.

Larichev, Yu., Matash, S.L. and Mazur, A.S. 2009. Influence of drilling and blasting on generation of dust and gas cloud. Izv. SPbGTI (TU). 6(32) : 60-62.

Larichev, Yu. 2009a. Safety services upon identification of explosive substances on the basis of analysis of explosion products. Safety services in Russia: experience, challenges, issues: Proceedings, II International Conference. SPbUGPS Emercom of Russia. 55-57.

Larichev, Yu., Kovalevskii, V.N. and Mazur, A.S. 2010. On influence of drilling and blasting on generation of dust and gas cloud. Vzryvnoe Delo. 103(60) : 268-282.

Menzhulin, M.G. and Paramonov, G.P. 1997. Generation of dust fractions upon blasting destruction of rocks, Vzryv-1997: Collection of research papers, IGD, Alma-Ata. 152-155.

Procedures of Calculation of Harmful Emissions (effluents) for equipment of open-pit mines (on the basis of specific performances). 1990. Lyubertsy: Skochinsky Mining Institute.

Shmeleva, T.P., Shevchenko, M.A. and Tkacheva, A.M. 2006. Draft regulations of maximum permitted emissions into environments for open-pit mines with crushing and screening facility at Kamennogorsk deposit of granite and gneissogranite (ZAO Kamennogorsk department of open-pit mines). Sosnovy Bor. 13-19.

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