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Abstract

Content

Introduction

Industrial explosives are widely used in various industries. With the help of blasting produces about 70% of minerals, carried more than 90% of the workings in the mines, and nearly 70% – in the coal mines of the Donets Basin. It is impossible to develop the mining industry, the construction of large structures , dams, roads in the mountains, in swamps without the use of explosives. With the explosive is seismic exploration for minerals, massive explosions in the open deep in the bowels of the earth deposits of ore. People have learned to change the colossal explosion reliefs of the mountains and create barriers mudslides, quickly reverse the effects of mountain landslides and earthquakes, to extinguish forest fires, welding thin sheets of dissimilar metals, to strengthen steel structures.

In this regard, is highly relevant to work toward improving the safety, effectiveness, efficiency, increase utilization of potentially explosive second energy.

Industrial explosives (IE) – is explosive, which are characterized by reduced sensitivity to external influences and the relatively low cost. They must detonate without fail by means of initiation not have a harmful effect on the human body during the manufacturing and working with them.

It is known that an explosive transition of modern industrial explosives based on the oxidation of the combustible elements of oxygen. Therefore, without exception, mechanical explosives mixture should consist of at least two (non-explosive or explosive) components, namely fuel and oxidant. Oxidants – chemicals that contain excess oxygen, and can easily give him (ammonium, potassium, sodium nitrate). With remaining oxidant properties, and will certainly affect the properties of a substance th explosively. That's why I study of the effect of oxidant on the properties of IE in a hot topic.

The aim is to study the effect of oxidant on the properties of industrial explosives.

To achieve this goal it is necessary to solve the following tasks:

  1. Conduct analysis of research and publications to determine the main types of oxidants used in the IE.
  2. To examine the effect of various oxidants on the properties of explosives.
  3. Consider the possibility of new cleaner and more efficient industrial explosives.

1. Literature review

1.1 Types of oxidants for the IE

As an oxidizing agent in the composition of industrial explosives, ammonium nitrate can be used and other liquids and solids.

Explosive mixtures based on ammonium nitrate are the most common industrial explosives. This is due to the availability of nitrate, a broad industrial base of manufacturing, as well as compare the safety of processing mixtures based on it. In the explosive mixtures of ammonium nitrate acts as an oxidant and fuel can be a variety of organic compounds, including explosives with negative oxygen balance, such as TNT, dinitronaphthalene and others, as well as metal powders of aluminum.

In addition to ammonium nitrate in the industrial explosives as an oxidizer can be introduced other liquid and solid compounds. Their relative performance can be evaluated on the energy characteristics of stoichiometric mixtures, which contain the same fuel. Table 1 shows the results of calculations of energy characteristics of the mixtures with TNT, with the efficiency criterion adopted by the magnitude of the ideal work of explosion, the relative efficiency is expressed as a percentage of the ideal work of TNT mixture with ammonium nitrate as 100.

The highest rates are based on a mixture of liquid oxidizing agents that are superior in performance to the ammonites 1,42-1,66 times.

From the above Table. 1.1 oxidants other than ammonium nitrate in the industrial explosives used salt of perchloric and chloric acids (perchlorate and chlorate explosive), nitrates, alkaline earth and alkali metals. The last part introduces some of the water-filled BP to increase the density, as well as selectively detonating fuse IE.


Table 1.1 – Energy characteristics of explosive mixtures
Oxidant The content of TNT, % The heat of the explosion, kJ/kg The volume of gas explosion, L / kg Complete the perfect work of the explosion, kJ/kg Efficiency relative to TNT,%
Nitrogen tetroxide (N2O4) 48,4 7930 650 5950 166
Hydrogen peroxide (Н2O2) 41,3 7080 835 5680 159
Nitric acid monohydrate (НNO3) 46,3 6360 695 5090 142
Ammonium perchlorate (NH4ClO3) 31,5 5710 745 4620 129
Sodium perchlorate (NaClO4) 41,4 6170 450 4360 122
Ammonium nitrate (NH4NO3) 21,3 4310 892 3570 100
Sodium nitrate (NaNO3) 38,8 4960 420 3420 95,5
Potassium nitrate (KNO3) 35,0 4370 380 2940 82

Perchlorate explosives – a mixture that is used as an oxidizer salt of perchloric acid –potassium perchlorate, sodium or ammonium. Explosive mixtures containing perchlorate salts have a very high sensitivity to friction and impact, so they are hardly used.

Perchlorates as oxidizers provide a large energy gain as compared with ammonium nitrate. Thus, the stoichiometric mixture of ammonium nitrate with TNT have the heat of explosion 4190 kJ/kg, with paraffin – 3770 kJ/kg, and those with a combustible mixture of ammonium perchlorate formed with the heat of the explosion, respectively, 5550 kJ/kg and 5230 kJ/kg.

Traditional methods of desensitization of nitro compounds and their mixtures introduction of these low-melting organic substances (paraffin and, as ceresin, wax, and etc.) not only reduces the sensitivity of the perchlorate salts of x and their compositions, but on the contrary, increase it. The strongest is phlegmatizer gelatinize water, which reduces the sensitivity to shock perchlorate salts from 80-100 to 40-60%.

Perchlorates of sodium and potassium form a less sensitive mixture than ammonium perchlorate. In the explosion, they form a fine metal chlorides, which act as inhibitors. According to their e introduced into the compositions of some explosives safety.

There are patents U.S., UK, in which suggest ways of preparing the compositions based on nitric acid. Such compounds have been known at an early stage of development of industrial explosives. The greatest amount of heat in systems of acid-TNT stands for TNT content of 35-40%. The most accessible and cost-effective are based on the position gelatinize polyacrylics acid enzymes, the heat of the explosion are 8370-9210 kJ/kg. The heat of explosion of mixtures of nitric acid, aluminum can reach 11,720 kJ/kg.

The high volatility of nitric acid, its aggressiveness and poor survival of the gel on the basis of its hinder the practical use of such compositions.

The liquid explosive mixtures based on nitrogen tetroxide, tetranitromethane, and 98% nitric acid, used as an oxidant, and kerosene and (fuel), characterized by a high capacity of the detonation. The critical diameter of detonation of these mixtures 1.2-2 mm. Mixtures of this kind used in drilling technology explosion [1].

Because of the convenience and, propagation as an oxidant for IE was ammonium nitrate. According to its properties will be discussed in more detail.

1.2 Ammonium nitrate and its properties

Ammonium nitrate – the technical name of the ammonium nitrate NH4NO3, molecular weight 80.05. In pure form, it contains 35% nitrogen, 5% hydrogen and 60% oxygen, 20% of which is allocated in the free state in full expansion. Melting point: 169,6 ° C [2].

Ammonium nitrate – a white crystalline substance which is prepared by reacting ammonia with nitric acid according to the equation


NH3 + HNО3 → NH4NО3.

Available in the form of granules or crystals. The granules of ammonium nitrate, which are formed during solidification of the melt, are capillary-porous body. The maximum possible density of the crystals 1,725 g/сm3. In practice it is lower due to the presence of shells and other defects in the crystal lattice [1].

Ammonium nitrate had been applied in the pure form of insensitive explosives in mass explosions, the heat of explosive conversion of nitrate 1600 kJ/kg, performance in the lead bomb 165-230 cm 3. The heat of formation – 355 kJ/ mole.

Explosive reaction of ammonium nitrate


NH4NО3 → N2 + 2H2O + 1/2O2.

With insufficient initiation, as well as the thermal explosion, it can decompose for other equations with lower thermal effects, and with the release of toxic nitrogen oxides as well. This, in particular, explains plained release of nitrogen oxides in the inferior explosions based on ammonium nitrate.

Sensitivity to the nitrate pulse detonation depends on the moisture content, granule size and density pa. Detonation of a dry finely divided AU at a density of 0.8 g/cm3, according to Belyaev, firmly apply the open charges with a diameter of about 100 mm. Detonation with a particle size of 1 mm and relative humidity of 1% charge is attenuated in the open diameter of 300 mm. speakers with 3% moisture content does not explode in charges even larger diameters. Sensitivity to explosion increases as a result of local dissolution and recrystallization following nitrate, which leads to porosity.

According to Cook, the detonation velocity of AN depending on the charge diameter takes the value given in Table 1.2.


Table 1.2 – Dependence of detonation velocity on charge diameter AN
d, mm 100 150 200 250 300 460
D, km/s none 1,4 1,6 1,8 1,15 2,75

2. The experimental part

2.1 Electrification of IE

In manufacturing the accumulation of static electricity can reach such limits at which the discharge is capable of igniting or causing an explosion sensitive spark discharges of substances. In addition, the electrification process can be created obstacles, such as the buildup on the walls of vessels and pipelines, balling powders, difficulty in sifting, etc. Because the phenomenon of electrification should be considered when manufacture and use of explosives and provide, where necessary, appropriate measures protection.

To assess the reliability and the risk of electrification in the application of industrial explosives into account not only the electrical characteristics of explosives, but also the conditions of their application, which can significantly affect the formation and accumulation of static electricity when working with explosives. In certain circumstances, some are capable of industrial explosives and sprayed flake (for transportation, pnevmozaryazhanii, filling in holes, etc.). IE dusting usually leads to an increase in electrification, and the electrification becomes dangerous, if a dust-sensitive spark discharge of substances such as TNT or aluminum [7].

2.2 Improvement of IE based on ammonium nitrate

One of the most common explosives on the basis of AN is Grammonite 79/21. Grammonite 79/21[1] the substance of the second class is intended for blasting in quarries, mines and coal mines, non-hazardous gas and dust in manual and mechanized load the wet and dry (dehydrated), boreholes, wells, and cameras. To initiate electric detonators and detonating cord requires an intermediate detonator, for which open work quite the same pieces of T-400g, and underground work of a standard ammonite cartridges of any brand. Available in nepatronirovannom form and can be used in all climatic regions of the CIS countries.

During the years of practice to use grammonite identified the following deficiencies: caking, dusting, and electrified.

Caking grammonite 79/21 comes from the hygroscopicity of ammonium nitrate and its ability to polymorphic transformations. Caking agents leads to a crash in the bunkers, arching at pnevmnozaryazhanii wells complicated transportation of explosives on pipelines and hoses to the places of loading.

Dusting grammonite appears by mechanical loading wells. If you load the mechanized steps must be taken to prevent spillage and release of dust or particles of explosives into the surrounding space. In all cases, the content of components of explosives in the air of working zone, regardless of contact time with the people, shall not exceed the maximum allowable concentration, which is 0,5 mg/m3.

Grammonite 79/21 packed in bags, which are composed of two layers: the inner – plastic, and external – polypropylene. Because of this increased grammonite electrified. In production conditions the accumulation of static electricity can reach such limits in which they discharge able to ignite or cause an explosion sensitive to spark discharge of substances. In addition, the electrification process can form barriers such as food sticking to the walls of vessels and pipelines, and the difficulty in sifting etc. Therefore, the phenomenon of electrification should be considered in the manufacture and use of explosives substances.

In order to eliminate caking and dusting of the explosives enveloping added supplements, such as industrial oil (IO), but this leads to an increase in electrified. To reduce the above drawbacks, it was decided to introduce into the grammonite 79/21 enveloping additive in the form of industrial oil [8] and powder supplements in the form of graphite grades. Components of the mixture of ammonium nitrate with graphite and ammonium nitrate with 0.5% oil and graphite. The graphite content ranged from 0.24% to 1.02%.

Check electrified AN mixtures was carried out as follows. Ammonium nitrate was placed in a container an even layer, whose thickness was 15 mm. Electrified megger tested, with the electrode contact surface which is 3,5x3. The experimental data are shown in Table 2.1.


Table 2.1 – Electrical characteristics AN and mixtures based on it

Composition of the mixture Composition, % Composition, g Electrified, kОm
АN 100 50 300
АN+graphite 100+0,24 50+0,12 150
АN+graphite 100+0,48 50+0,24 120
АN+graphite 100+0,72 50+0,36 100
АN+graphite 100+0,96 50+0,48 85
АN+graphite 100+1,02 50+0,6 70
АN+IO 100+0,5 50+0,25 500
АN+IO+graphite 100+0,5+0,24 50+0,25+0,12 300
АN+IO+graphite 100+0,5+0,48 50+0,25+0,24 250
АN+IO+graphite 100+0,5+0,75 50+0,25+0,36 200
АN+IO+graphite 100+0,5+0,96 50+0,25+0,48 180

Figure 2.1 shows a graphical relationship electrified the content of graphite in mixture. According to the experimental data we see that the AN electrified net is 300 kOm. When adding electrified industrial oil sharply increases up to 500 kOm. At adding 0.24% graphite AC electrified drops sharply from 300 to 150 kOm. With a further graphite content increases to 1% electrified gradually reduced to 70 kOm. The composition, containing graphite and industrial oil, has electrified more than a mixture of AN and graphite. Electrified mixture of graphite+AN+IO also decreased with increasing content of graphite. The resulting mixtures retain flowability during the six months to the end of this period form small lumps are easily broken under pressure with your fingers.


Figure 2.1 – The dependence of the electrified content of graphite in a mixture

The optimal recommended content can be considered an 0.5% of IO and 0.8% of graphite.

From the standpoint of safety of the explosion products in the preparation of explosive mixtures should strive to mixtures with zero oxygen balance or with a small deviation, so the calculations were carried out[9] oxygen balance and heat of explosion of new mixture. The oxygen balance of the original grammonite 79/21 is +0.02, the oxygen balance improved mixture is estimated at -3.6. The heat of the explosion before the grammonite addition of 4280 kJ/kg, when administered IM 0.5% and 0.8% graphite, the figure rose to 4710 kJ/kg.

Conclusion

At this stage of the study was to consider the influence of various oxidants on the IE properties. The highest rates are based on a mixture of liquid oxidizing agents that are superior to ammonites in the performance of 1,42-1,66 times. Stoichiometric mixture of ammonium nitrate with TNT have heat of explosion of 4190 kJ/kg, with paraffin – 3770 kJ/kg, the same fuels with ammonium perchlorate form a mixture with the heat of the explosion, respectively, 5550 kJ/kg and 5230 kJ/kg. But because of the inconvenience use and the high sensitivity of these explosives are not widely used.

The paper discusses the most common oxidant properties in the industrial explosives - ammonium nitrate. Its prevalence is explained by the availability of nitrate, a broad industrial base of manufacturing, as well as compare the safety of processing mixtures based on it.

IE based on ammonium nitrate has the following disadvantages: caking, dusting, electrified. In the course of the improved explosive composition Grammonite 79/21, by introducing additives in the form of industrial oil and graphite. The improved composition has less electrified and caking. Optimal amounts of additives: 0.5% of industrial oil and 0.8% graphite. Were calculated energy characteristics of a new composition. Its oxygen balance is reduced, and -3.6, the heat of the explosion has increased from 4280 to 4710 kJ/kg.

Master's work is not yet completed in writing this abstract. Completion date of work – December 2012. Full text of the work and materials on this topic can be obtained from the author or his head after that date.

References

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