Development of commercial explosive reducing development pressure on the environment

17/07/2014 2:29pm

Автор: Zakusylo V.R., Efymenko A.A.

Категории: ecology

Development studies of nitrateammonium commercial explosive (CE) reducing development pressure on the environment during mining are presented. For providing of waterproofness, ammonium nitrate prills were primed bynitrate cellulose or conversionblasting powder, not suitable for further usage for the purpose specified. By thermodynamic calculation it was stated the correlation of ammonium nitrate and primed coating of commercial explosive, providing the absence of toxic fumes in explosion products. Introduction of coating of surface-active materials allowed to eliminate static characteristic of commercial explosive and make it save at spilling and loading of chinks even by pneumatic transport. New commercial explosive is waterproof, does not form toxic gases at explosive conversion, does not electrify at spilling and transportation, that provides ecological security of its usage. 
Key words: ecological security, commercial explosive, gaseous products of explosion, waterproofness, static characteristic

UDK 502.7

 

Vasyl Zakusylo

PhD, docent of chemical technology of macromolecular compounds department
Shostka Institute of Sumy State University, Shostka, Ukraine

Anna Efymenko

 graduate student, department of chemical technology of macromolecular compounds
Shostka Institute of Sumy State University, Shostka, Ukraine


Ecological security when applying commercial explosive for mining is relevant task in mining industry all over the world. Productive activity of metallurgical and mining complex affects greatly environment. At explosive conversion of high energy systems, millions of tons of harmful substances are wasted into atmosphere, millions of cubic meters of polluted wastewater are thrown into water, and huge amount of solid wastes are stored on the top of the ground.
The main commercial explosives used both in Ukraine and abroad, are nitrate ammonium and tolite-containing ones. During application of tolite-containing commercial explosives there forms up to 115 l/kg of carbonic oxide [1, 2]. This substance is very toxic, as it is dangerous not only for air ecosystem but also for a human. During longtime contact of operating personnel with small concentration of carbonic oxide, poisoning is possible, which may lead to fainting. Carbonic oxide affects human’s cerebral cortex, provokes irreversible nervous system disorder. Besides tolite, which is included as coating of ammonium nitrate prills, such CE as grammonite 79/21 GS is dielectric. Pneumatic loading of granulated CE, containing tolite, is followed by intensive electrification of the CE flow, herein electrostatic energy is 52.8mJ at minimum ignition energy of grammonites 1.05 mJ. That is why electrification phenomena should be considered during manufacturing and application of explosives, as it may lead to striking of spark and non-planned explosion during exploitation of CE. 
Analysis of existing literary sources showed that existing commercial explosives on the base of ammonium nitrate have the following disadvantages:

  1. pollute the atmosphere by toxic gases exceeding the norms of ecologically permissible concentration;
  2. low water resistance (exept emulsive CE), which is followed by pollution of ground ecosystem by ammonium nitrates;
  3. low energetic characteristics;
  4. low  chemical and physic constancy;
  5. granulated CE is tended to electrification, which increases the possibility of explosions during their storage, usage at transportation;
  6. emulsive CE is used for loading of chinks only in hot condition, that determines their usage just after manufacturing;
  7. granulated CE with coating  is brittle, breakaway, dust, increasing man-caused load on the environment.

It is possible to create balance between ecological aspects and increased explosive characteristics of CE by means of creation of new waterproof nitrate ammonium CE, which would not have these disadvantages. That is why for environmental security, high water resistance, energetic characteristics and absence of post-detonation toxic fume and electrification during usage, security of high strength as coating of ammonium nitrate prills, high-powered material - nitrate cellulose is chosen [3].
At this stage of industrial development utilization of non-effective armament [4] is fulfilled by means of outdoor burning, which is followed by emission of great amount of nitrogen oxides and carbon. Creation of CE on the base of nitrate ammonium and conversion nitrate cellulose powder explosive provides not only water resistance and high explosive characteristics but also allows to reduce man-caused load on the environment by means of processing of utilizable powders explosive into ecologically clean commercial explosive.
Researches concerning application of colloxylins, conversion pyroxiline and ballistit powders and also ballistite rocket fuel as a composite of nitrate ammonium CE are presented. For reduction of air pollution by post-detonation toxic fume of CE, system oxygen balance was preliminary calculated. For calculation of oxygen balance of the mixture, molecular number of components was calculated:

  1. ammonium nitrate (AN) (NH4NO3) with 80 molecular number and +20% oxygen balance;
  2. BP NDT-3 (C23.00H30.00N10.00O 34.00) with 990,00 molecular number and - 44% oxygen balance;
  3. Industrial powder explosive (IPE) (С6H7.55N2.45O9.9) with 272,25 molecular number and - 38% oxygen balance.

Composition of nitrate ammonium CE with zero oxygen balance contains: 66% AN and 34% IPE; 69% AN и 31% BP or ballistite rocket fuel RSI-12K.  Commercial explosive under development is called ammoporom –W [5]. In order to determine amount of gas and thermodynamic characteristics, which is evolved during explosive conversion of CE, there were fulfilled researches in accordance with multi-purpose program “Astra” – “Modeling of chemical and phase equilibrium at different temperatures” and   Avakyan methodology .In the base of “Astra” program lies universal thermodynamic method for determination of characteristics of heterogenic systems balance; these systems are based on the basis of maximum entropy. The program allows to calculate the amount and composition of combustion gases. Research results are presented in the table 1.

Table 1 thermodynamic characteristics and gas composition of CE

 

Indicator name

Values

Ammoporom –W

Tolite-containing  CE

Entalpy Hs, kJ/kg

952.96

44.49

Acidity coefficient, А

101.58

36.36

Coefficient of sales, К %

0.97

0.76

Oxygen balance, %

0.91

-74.01

Heat capacity, cal/mole

149.18

86.68

Explosion heat, kcal/kg

916 - 925

985

Gas volume, l/kg

909 - 920

785

Explosive temperature, К

2642 - 2705

2869

Fougasseness, ml

316

307

Detonation velocity, м/с

5400

4250

Pressure Pr, kg/sm2

59509

58282

 

Gas composition

Amount of gas, mole/kg

Ammoporom –W

Tolite-containing  CE

Н2О

21.91

20.36

СО2

5.25

6.38

СО

0.00

14.78

С

0.00

14.41

Н2

0.01

2.66

N2

6.86

10.56

О2

2.2

1.91

NO

0.4

3.06

Calculations showed that ammoporom –W has high explosive characteristics, and also during its explosion toxic gases are not formed. Gas composition of explosion products is exposed mainly by Н2О steams, СО2 and N2 bioxyde, which are provided by zero oxygen balance.
When applying most of nitrate ammonium explosives in wet holes, there take place scavenging and accumulation of AN in subsurface water and quarry cracks, which pollute them. For lowering of man-caused load on the environment with the help of device with fluidized bed, laquer on the base of utilized powders, saluted in acetic ether, was applied on the ammonium nitrate prills for formation of firm waterproof jacket. Physical form of commercial explosive and section of ammoporom –W granula are shown in the figure 1.


Physical form

а


Physical form

b

Figure 1 Physical form of CE a; section of ammoporom –W granula, 120х magnification range – b.

For determination of degree of coating water perviousness special methodology is developed [6]. This method allows to determine water resistance of films at different pressures, from air pressure to 2 kg/sm2, and also within temperatures from 18оС to 40оС. This is connected with the necessity of CE application in underground conditions, where increased temperatures and pressures are possible. Increased pressure imitates water flowage.
Research of characteristics of coating on the AN granules is complicated. That is why at technological mode of CE production, nitrate rayon laquer was applied on the glass or plastic plates in order to get the film in the form of sheet material. For reliability of data, density of coating and film was determined. Density of nitrate rayon film and CE coating, which was determined by volume-weight method, was similar and made 1.46 (±0.01) g/sm3.
Research results represented in the form of characteristic curves in the figure 2.

water resistance

 

Figure 2 Dependence of water resistance of nitrate rayon film on holding time in the water:

■ – at atmospheric pressure  and temperature 18оС;
● – at atmospheric pressure  and temperature 40оС;
▲– at pressure 1.5 kg/sm2 and temperature 18оС.

It follows from the figure 2 that increase of the temperature and pressure contributes acceleration of diffusion processes of water molecules penetration through nitrate rayon film.
Operating CE grammonite 79/21 GS has coating on the base of tolite with low strength characteristics, up to 1.2 kg/sm2. Coating may crack when granules contact with each other, also destroy and peel while exploitation, these provokes man made danger while application of grammonite 79/21, considering its high static characteristic. Nitrate rayon coating ammoporom –W has the strength up to 20 kg/sm2, that is why it is not destroyed.
To reduce its static characteristic, 0.1-0.2% of surface-active substance, such as polyoxyethylene allylphenol ethers of OP-4, OP-7 or OP-10 type were included.  Volume resistivity of CE reduced from 108 Ohm·m to104 Ohm·m, i.e. ammoporom –W was changed from dielectric to conductor. Absence of ammoporom –W static characteristics provides its save exploitation even during pneumatic conveying and pneumo-loading of holes, which is particularly topical during blasting workings connected with iron ore crop in underground conditions of Kryvyi Rih region.
Developed nitrate ammonium commercial explosive will reduce man-caused load on the environment by means of:

  1. processing of conversion and ballistit powders,  rocket fuels, being accumulated in Ukraine and presenting ecological threat for natural environment;
  2. lowering of solvability of nitrate ammonium that will provide reduction of ground-water ecosystem pollution during blasting workings;
  3. reduction of emission of toxic gaseous products during blasting workings connected with mining;
  4. securing of accumulation of static charge on the CE surface, excluding man-induced disaster during spilling, transporting and loading of holes.

References

  1. Pozdnyakov Z. G. Spravochnik po promyshlennym vzryvchatym veshchestvam i sredstvam vzryvaniya [ Reference book about commercial explosives and means of initiation]. Moscow, Nedra, 1977, 253 p.
  2. Калякин С. А. Разработка граммотола 1-1 для замены тротилсодержащих граммонитов / С. А. Калякин, Н. А. Новикова //  Сучасні технології в машинобудуванні, транспорті та гірництві. – 2012. – № 1(72). – С. 78–82.
  3. Kalyakin S. A., Novikova N. A. (2012). Development of grammotol 1-1 for replacement of tolite-containing grammonites. Modern technologies in machine building, transport and mining. No 1(7), p. 78-82.
  4. State objective defensive program concerning utilization of general armament, which is unsuitable for further usage and storage for 2008-2017, confirmed by Resolution of the Cabinet of Ministers of Ukraine dated 22 of October, 2008, No 940.
  5. Patent 72202 U Ukraine MPK6 C О6 B 31/28. Commercial explosive. V. P. Kuprіn, V. R. Zakusilo, A. O. Єfimenko, O. V. Kuprіn. No 01085, bulletin No15.
  6. Patent 85425 Ukraine МПК6 G О1 N 9/32. Way of determination of water perviousness of film materials. V. R. Zakusilo, A. O. Єfimenko. No 02657, bulletin No22.


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