Patent Application
20230331638
In a first aspect, the present invention relates to a granulated explosive based on a water-in-oil emulsion with one or more oxygen carriers, water, one or more fuel carriers and emulsifier. Additionally provided is a method for producing a granulated explosive according to the invention, based on a water-in-oil emulsion, containing oxygen carriers, water, fuel carriers and emulsifier. Lastly described is a granulated explosive obtainable using the method according to the invention, and the use of the granulated explosive according to the invention.
Granular explosives based on ammonium nitrate, as typical examples of commercial explosives used across a wide variety of different sectors, are composite explosives. These so-called ANC (ammonium nitrate-carbon) and ANFO (ammonium nitrate-fuel oil) or ANDEX explosives are provided in the form of a flowable mixture of ammonium nitrate and carbon carriers. ANFO is produced typically in the form of millimeter-size porous granules, which are also referred to as prills, by mixing with liquid hydrocarbons, typically oil. The reaction of such explosives is associated with the evolution of comparatively high amounts of toxic blasting fumes. In particular, nitrogen oxides (NO and NO:) and also carbon monoxide (CO) represent critical fume constituents, which must be reduced to the achievable minimum for the protection of people and environment. Especially in mines and underground pits, in other words in subsurface mining, there is a requirement to reduce nitrogen oxide emissions (NOx). In underground mining, the blasting fumes given off are conducted as foul air through the mine workings, and the stated gases pollute the underground working atmosphere (air). The workplace limits for components of these gasses in the air breathed in, are strictly regulated. Correspondingly there is a requirement to provide low-emission explosives, preferably in granular form, which when used give off only small amounts of environmentally and physiologically harmful off-gasses, in other words to further reduce the fraction of possible harmful gas components, including NOx, in the blasting fumes that are released.
Granular emulsion explosives represent a further embodiment of such suitable explosives. Here, for example, there is the Landex® product from Kayaku Japan Ltd., in the form of a granular emulsion developed primarily for tunneling. The granules in the form of pellets, are produced by extrusion and are composed, along with the oxygen carriers ammonium nitrate and sodium nitrate, of a fuel phase with emulsifier, wax and resin. This product necessarily requires the presence of hollow microspheres for sensitization; see also Taguchi et al., Sci. Tech. Energetic Materials, 2005, 66, 393-397. An essential feature of this product is that the structure is relatively soft and hence on mechanical stressing, such as in pneumatic charging procedures on densely packed charge columns, the extruded pellets are deformed and crushed. By varying the pneumatic insertion pressure it is therefore possible to adapt the density of the charge column and thereby to exert a targeted influence over the detonation properties, such as the velocity of detonation. The presence of the hollow microspheres ensures the detonation capability of the charge column even with the borehole filled out to the maximum. Because of the comparatively low strength and the presence of the hollow glass microspheres, however, this product can only be sold in small packaging units of not more than 20 kg; shipment and storage in large quantities is not possible. Furthermore, after the detonation, it is possible for remnants of the hollow microspheres—i.e. the glass fragments—to be present in the blasted material.
The advantage of emulsion explosives, in comparison to conventional granular explosives, such as the aforementioned ANFO explosive, is an even greater reduction in the toxic blasting fumes. This is due to the intense mixing of the fluidized reaction partners within the emulsion. The finely disperse state is achieved through the homogenization of the fluid phases. Within solid bodies, such as ammonium nitrate prills, where the contact area of the reaction partners is determined by the pore network and the dimension of the solid-state structure, this is possible only to a limited extent.
Emulsions are disperse systems composed of at least two mutually immiscible liquids, where the dispersed phase is present in the form of distributed droplets within a continuous phase. Water-in-oil emulsions are emulsions where water is present as the disperse phase in a continuous oil phase. An essential feature of emulsions is the finely disperse state of the disperse phase. In the case of emulsion explosives, the emulsion matrix is a water-in-oil emulsion, with the fuel, in the form of mineral oil, for example, the continuous phase, and a supersaturated solution of oxidizing salts (oxygen carriers) constituting the disperse phase. The contact area of the reaction partners is increased substantially in comparison to conventional ANC explosives, owing to the finely disperse structure with droplet sizes in an order of magnitude of 10 μm, and the reactive reaction is additionally promoted by the dissolved state of the oxygen carriers. Corresponding structural properties favor the stoichiometrically balanced reaction of the composite explosive, and so the energy utilization of the reaction increases and fewer toxic reaction products are formed. Emulsion explosives, described for example in U.S. Pat. No. 3,447,978A, have been used commercially since the 1980s/1990s, and there are also descriptions of emulsion preparations which are solidified by polymerization reaction and employed in the form of cartridged explosives. In the prior art, furthermore, the structuring of granular emulsion explosives via the solidification of the continuous phase is described; the shaping may be accomplished by spray drying, vacuum pelletizing, or comminution of the cured emulsion matrix.
CN 101555183 B describes emulsified explosive particles comprising ammonium nitrate with at least one further oxygen carrier from among sodium nitrate, aluminum nitrate, calcium nitrate and magnesium nitrate, water, emulsifier, specifically sorbitan monooleate or a mixture of sorbitan monooleate and polyisobutylene succinimide, and a fuel carrier based on paraffin, ceresin, rosin, asphalt and/or stearic acid. Known from CN 110357755 is the production of mixed emulsion explosives, which comprises adding an aqueous solution and an oil-phase solution to an emulsifier to form a water-in-oil structure.
One problem of emulsion explosives is the use of water as solvent for the oxygen carriers, as the water is detrimental to the energy content of the explosive. In order to reduce the amount of this inert component, the heavy temperature-dependence of the solubility of oxygen-supplying salts is utilized, which rises significantly as temperatures increase. The water content of completed emulsions is usually 10% to 20%, as also in the above mentioned Landex® product.
Additionally there are usually emulsifiers present, which are soluble in the continuous phase and lead to a critical reduction on the surface tension.
An aim of the present invention is to provide granular explosives, especially those based on ammonium nitrate, which feature a reduced fraction of toxic gas components, especially NOx, in the blasting fumes released, with correspondingly high energy contents.
Improved emulsion explosives can be provided by improving the composition in respect of the oxygen carriers, water, fuel carriers and emulsifiers in order to provide granulated explosives based on a water-in-oil emulsion. These granulated explosives of the invention, based on a water-in-oil emulsion, exhibit much lower values in terms of the emission of the toxic gas components and especially of the NOx compounds (nitrogen oxide), but also of CO (carbon monoxide), in the blasting fumes released, while achieving a very good blasting effect. Provided accordingly, in a first aspect, is a granulated explosive based on a water-in-oil emulsion, comprising:
It has emerged that, relative to conventional ANC explosives, these granulated explosives have very much lower NOx fume volumes. It has been possible, furthermore, to achieve higher velocities of detonation relative to conventional explosives, especially to a granular explosive such as ANDEX LD as an example of an ANFO explosive.
In one embodiment the granulated explosive based on a water-in-oil emulsion consists of
It has been found that these proportions and amounts of the individual components provide a granular emulsion explosive having very good usability.
Because the explosive of the invention contains less water by comparison with prior-art granular emulsion explosives, an example being the explosive sold under the Landex@ product name, the product is firmer, has good flow behavior, and in particular also displays improved storage stability.
A high water content additionally means that caking of the granulated explosive may occur and therefore impairs its use, particularly the charging of the blast boreholes.
The oxygen carrier may be one compound or a combination of compounds. In one embodiment the oxygen carrier is selected from alkali metal and alkaline earth metal nitrate, ammonium nitrate, alkali metal and alkaline earth metal chlorate, ammonium chlorate, alkali metal and alkaline earth metal perchlorate and ammonium perchlorate. Alkali metal nitrite or chlorate and perchlorate include sodium nitrate, potassium nitrate, sodium chlorate, potassium chlorate, sodium perchlorate and potassium perchlorate. Alkaline earth metal nitrate and chlorate and perchlorate include magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, calcium chlorate, strontium chlorate, barium chlorate, magnesium perchlorate, calcium perchlorate, barium perchlorate and strontium perchlorate.
In one embodiment a constituent of the oxygen carrier is ammonium nitrate.
Ammonium nitrate is used typically in combination with a second nitrate, especially an alkali metal nitrate, such as sodium nitrate. In one embodiment in this case the oxygen carrier is a mixture of ammonium nitrate and sodium nitrate, with the mass ratio of ammonium nitrate to sodium nitrate being 5 to 8:1. In one embodiment, however, the oxygen carrier ammonium nitrate is also used on its own in the granulated explosive of the invention.
If ammonium nitrate is used on its own, then in one embodiment additionally an auxiliary is added, in particular for seeding the crystallization of the ammonium nitrate in the granulated explosive. The skilled person knows of suitable auxiliaries for seeding. This auxiliary is added typically at not more than 0.5 percent by mass.
In one embodiment the granulated explosive is one based on a water-in-oil emulsion, the fuel carrier being selected from plant wax, plant oil, animal oil and fat, paraffin wax, light crude oil, kerosine, mineral oil, lubricating oil, heavy oil, carboxylic acid, carboxylic ester and microcrystalline wax, or else combinations of at least two fuel carriers. Suitable fuel carriers include in particular a paraffin, stearic acid and salts of this carboxylic acid, such as magnesium stearate. Monocarboxylic acids and their salts, especially salts with alkali metals and alkaline earth metals, are preferred. In one embodiment the fuel carrier is stearic acid. In another embodiment the fuel carrier is a combination of stearic acid and magnesium stearate or stearic acid with paraffin.
One embodiment of the present invention, then, relates to granulated explosives of this kind, the fuel carrier being at least one selected from paraffin, animal or plant oil and salts thereof, especially paraffin or stearic acid. Likewise possible are the combinations of these fuel carriers, especially paraffin and stearic acid, or stearic acid and stearate, or paraffin and stearic acid and stearate. The paraffin and stearate combination is also conceivable.
In accordance with the invention there is an emulsifier in the granulated explosive. Suitable emulsifiers are, for example, those based on polyisobutylene-succinic anhydride (PIBSA), based on sorbitan monoisostearate (SMIS), or an emulsifier based on polyisobutene lactone (PIB lactone), or mixtures thereof. In general an emulsifier may consist of one or a mixture of two or more emulsifiers. In one preferred embodiment the emulsifier is based on PIBSA. Emulsifiers are known in the form, for example, of products from Lubrizol or Croda Mining, such as Anfomul.
One embodiment uses only one emulsifier, this emulsifier being one, for example, based on PIBSA or one based on PIB lactone. It is optionally possible to use two or more emulsifiers based on PIBSA or two or more emulsifiers based on PIB lactone.
In one embodiment the water fraction in the granulated explosive is a mass in a range with a mass fraction of 6% to 10%, such as 6.5% to 9.5%, more particularly 6.5% to 9%, based on the total mass of the explosive. If the fraction of water is too high, the transportability and storability and also the flow behavior of the material are impaired. In particular, caking of the granulated materials may occur. Conversely, a minimum level of water is needed in order to enable production. The lower the water fraction, the higher the processing temperature when producing the granulated explosive and the firmer the explosive produced. The processing temperature ought not, however, to be above 130° C.; for example, for safety reasons, the processing temperature ought not to be above 125° C., such as 120° C.
Corresponding amounts of water are provided, for example by providing the ammonium nitrate in the form for example of a hot solution, with one possible hot ammonium nitrate solution, i.e., ammonium nitrate dissolved in water, being at 91% to 93% (percent by mass) ammonium nitrate. Correspondingly a large proportion of the water needed is introduced by way of this hot ammonium nitrate solution.
In a further aspect, a granulated explosive based on a water-in-oil emulsion is provided, wherein the granules have an average particle size in the 0.5 mm to 4 mm range, such as 1 mm to 3 mm, more particularly 1 mm to 2 mm. At smaller particle sizes, the storability and conveyability of a corresponding bulk material are impaired. The stated ranges are suitable especially for transport and for the charging procedure in blasting boreholes, and for forming corresponding charged densities. In contrast to the Landex@ product, whose extruded, cylindrical pellets have a size range of 3 to 10 mm in diameter and 5 to 15 mm in length, the average particle size presently, in the above-stated ranges, of the granulated explosive of the invention is preferred. The particle sizes stated for the explosive of the invention were determined by means of sieve analysis.
In a further aspect, the granulated explosive based on a water-in-oil emulsion is one which has no further fillers, more particularly no cenospheres, e.g., hollow glass microspheres or foamed hollow spheres such as Styropor spheres.
In one embodiment the granulated explosive based on a water-in-oil emulsion is one which has no further additives at all; as well as the further fillers not present, this explosive in particular contains no further organic auxiliaries and additives.
The absence of these hollow spheres, such as hollow glass microspheres or Styropor spheres, is desirable in particular when the explosives are used for extracting raw materials which are processed further in the sectors of pharmacy, chemistry, fertilizers, food stuffs, comestibles or animal feed, or generally in sectors where contamination of the products with remnants of explosive is unacceptable. The presence of hollow microspheres in raw materials, in particular, such as in salts which are used in the sectors of pharmacy, fertilizers, food stuffs, comestibles or animal feed, is not permissible. In one embodiment the granulated explosive is one based on a water-in-oil emulsion, with
In another embodiment the explosive granulated in accordance with the invention is one based on a water-in-oil emulsion, with
This granulated explosive additionally comprises an auxiliary for the crystallization of the ammonium nitrate, this auxiliary being added typically in an amount of 0.01% to 0.8% mass fraction, such as not more than 0.5% mass fraction.
In a further aspect, the present application is directed to a method for producing a granulated explosive based on a water-in-oil emulsion, with this explosive comprising oxygen carriers, water, fuel carriers and emulsifier. This method of the invention comprises the following steps:
The granulated explosive of the invention based on a water-in-oil emulsion, then, is produced by means of hot emulsification, with the phase containing fuel carrier and emulsifier (fuel phase) being heated to a suitable temperature, so that there is no degradation of the emulsifier. Generally speaking, the temperature in this case ought not to exceed a value of 90° C., with the heating taking place to not more than 80° C., such as no more than 70° C.
Furthermore, the oxidant phase, the water-containing phase with oxygen carrier, is heated. This heating takes place necessarily above the crystallization temperature of the mixture of oxygen carrier and water, such as the mixture of ammonium nitrate and sodium nitrate, for example. The crystallization temperature here is dependent on the water fraction and on the mixing ratio of the salts provided. Heating in particular ought not to take place above 130° C., such as above 125° C., in order to prevent evaporation effects and also the formation of harmful gases (e.g. nitrous gases).
The oxygen carrier present is dissolved here completely in the water (oxidant phase). Separately from this, the fuel phase is melted, and in one embodiment the desired temperature of the fuel phase is achieved directly before the uniting of the fuel phase with the oxidant phase.
After the two compositions have been united, in the heated state, the emulsion is homogenized in a reactor with stirring function. In one embodiment, subsequently, the water-in-oil emulsion is cooled below the solidification temperature, where in one embodiment there is simultaneous shaping by means of suitable shaping processes for granulating the water-in-oil emulsion. The skilled person knows of suitable shaping processes and granulating processes. Shaping processes may be those selected from spray drying, extrusion, prilling, pastillation or pelletizing.
In one preferred embodiment the shaping and granulation process takes place in the form of pastillation.
Depending on the shaping by granulation, there may be subsequent grinding and subsequent classifying, especially sieving. The skilled person knows of processes suitable accordingly.
The homogenization in the stirring vessel may take place, for example, with the aid of a disk stirrer, a coil stirrer or, preferably, with a conical stirrer. An alternative possibility is to use a suitable dispersing system operated in continuous flow, such as a rotor-stator mixer, for example. The skilled person knows of suitable systems for homogenizing the emulsion.
The method of the invention may further envisage the addition of further components to the emulsion during the homogenization in the reactor. Further components which may be present in the granulated explosive of the invention based on a water-in-oil emulsion include the following: fillers, such as perlite or zeolite, additional structuring components in the form of water-insoluble polymers, e.g. polyisobutylene, natural rubber or synthetic rubber, or supplementary performance-enhancing constituents, such as aluminum powder, magnesium powder, sulfur, and explosives, such as nitro compounds or nitrate esters, for example.
The present invention additionally relates to a granulated explosive obtainable with the method of the invention for producing a granulated explosive based on a water-in-oil emulsion. This granulated explosive is notable for improved storage and free-flow properties and also for a reduced caking tendency. Following granulation, it is possible additionally to add anticaking agents or free-flow aids to the explosive of the invention in order to improve the flow and storage properties further. Moreover, the explosive of the invention exhibits, compared to ANFO explosive, a shortened initiation distance for detonation and also an increased velocity of detonation, with the consequence of a higher efficiency when blasting, because of the improved utilization of energy.
Lastly provided, in a further aspect, is the use of the granulated explosive of the invention, based on a water-in-oil emulsion, for producing explosives having improved properties of the release of gaseous nitrogen oxides and carbon monoxide during reaction, especially for use in cavity construction such as tunneling or cavern construction and also in raw materials extraction, such as quarrying, strip mining, excavation mining or in underground mining beneath the surface. The granular explosive of the invention is especially suitable for use as an explosive for the extraction of raw materials for the sectors of pharmacy, chemistry, fertilizers, food stuffs, comestibles and animal feed, and also, generally, for the extraction of raw materials for which instances of contamination with remnants of explosive are unacceptable.
Additionally provided in accordance with the invention is a packaging unit of the granulated explosive of the invention, this explosive based on a water-in-oil emulsion being present in the packaging unit in an amount of more than 25 kg, such as at least 30 kg, such as at least 50 kg, e.g., at least 100 kg. These packaging units are especially suitable for the transport and the storage of the explosive of the invention.
The present invention relates lastly to the use of the explosive of the invention based on a water-in-oil emulsion for blasting soft or hard rock, especially for use in the mining of potash salts and rock salts. In this context no booster charge is necessary for initiation, especially in small-caliber blasting boreholes. It has emerged unexpectedly that the initiation by means of detonators is sufficient and, with inclusion, there is a detonative reaction with comparatively high velocity of detonation, without any booster charge being used. The initiation with a detonator of the customary nature and strength is sufficient, where legally permissible.
On the basis of the structural characteristics of the explosive of the invention based on a water-in-oil emulsion, water-resistant granules can be produced, since with appropriate shaping the water-soluble salts are completely encased by the continuous phase. Where granules with fracture faces are present, the water resistance may be achieved by a suitable coating. In contrast to other granular ANC explosives, such as ANFO, for example, it is therefore also possible to use the explosive of the invention in wet and water-carrying boreholes.
Below, the explosive of the invention is described further by means of examples, without being limited thereto.
Components used:
Ammonium nitrate and sodium nitrate are used as oxygen carriers, and various carbon carriers, solid at room temperature, and also various emulsifiers are used. A corresponding overview is shown below:
Production method:
The water-in-oil emulsion according to the invention is produced by hot emulsifying. Both phases are heated/melted separately from one another, then united with one another with stirring and thereafter homogenized with vigorous stirring. For the production of the water phase, the oxygen carriers are weighed out together with the corresponding amount of water and are dissolved with heating. Further heating above the crystallization point should be avoided. The pH of this solution is in the range from 4 to 5. In parallel with this, the fuel phase is melted, being composed of the fuels and also the emulsifier. Phase unification takes place in the fuel phase preparation vessel at a peripheral stirrer speed of 1.5 m/s. For this purpose a Visco Jet@ conical agitator mechanism is preferably employed. The water phase is poured slowly into the initially-taken fuel phase, until the crude emulsion begins to form. Thereafter the speed of phase unification is increased, with a simultaneous increase in the peripheral stirrer speed to 3 m/s, until the addition of the water phase is concluded. The homogenization of the emulsion then takes place at a peripheral speed of 6 m/s for 1 minute. In the next step, the emulsion is spread out over an area, with a layer height of 3 to 5 mm. Immediately after the spreading-out, owing to the cooling, the emulsion matrix begins to solidify, and so a solid body is formed. From the solidified emulsion matrix, after cooling, fracture granules are produced, and can be fractionated via sieves having different mesh sizes.
Measurement of relevant fume constituents:
For the measurement of the blasting fumes, the explosives under test are ignited with enclosure in a steel tube closed off at one end and having a length of 1 m, a wall thickness of 17.5 mm and an internal diameter of 35 mm (see Elfferding, Triebel and Wachsmuth, Kali & Steinsalz 01/2018). The initiation took place using an electrical instantaneous detonator and a booster charge with 20 g of nitropenta. In addition, selected tests were carried out without a booster charge, and are described in example 4. The gas constituents in the blasting fumes were measured by means of a chemoluminescence instrument (CLD 822 Mr, ecoPhysics) and NDIR spectrometer (Sidor, Sick Maihack). For comparability of different measurements, the results are expressed as specific fume volumes in liter of gas component per kg of explosive under standard conditions, taking account of the mass of explosive tested. The results reported represent mean values from at least two measurements. The associated error indicators come from the calculation of the 95% confidence interval.
Employed as a reference were the blasting fumes from ANDEX LD with the composition, in terms of mass fractions, of 94% ammonium nitrate prills and 6% mineral oil. The velocity of detonation (VOD) was measured discontinuously by means of electrooptical signal processing (Explomet-Fo-2000, Kontinitro SA), allowing the development of the velocity of detonation to be appreciated over the length of the steel tube. Where only one value is reported for the velocity of detonation, it is the mean value weighted by the lengths of the individual measurement distances.
The composition of the formulation is represented in table 1.
The oxygen balance of the formulation indicated in table 1 is minus 0.4% and the theoretical specific standard gas volume on complete reaction is 932 L/kg. In the present example, the fracture granules were sieved off using sieves with mesh sizes of 2.5 mm, 3.15 mm and 4 mm.
The production of the formulation stated in table 1 produces granules of the explosive of the invention with good properties. The strength, the caking tendency and the flow behavior are highly suitable for the application. For further evaluation, fume measurements were carried out. Depending on the sieve used, particle size distributions of the explosive of the invention with mean sizes of 1.4 mm, 1.8 mm and 2.1 mm were obtained. Table 2 represents a compilation of the corresponding granular characteristics, and table 3 gives an overview of the specific fume volumes of relevant gas components and also an overview of the velocities of detonation.
The results in table 3 show that. the granular emulsion explosive of the invention has a significant potential for reducing toxic blasting fumes in comparison to ANDEX LD. Depending on the sieve fraction used, on average specific NOx fume volumes in the range from 0.8 to 1.1 L/kg were measured. It is found that lower specific NOx fume volumes are achieved with reducing particle size. The improved detonative reaction of smaller particle sizes is attributable to the greater sensitization as a result of the larger number of pores between the granules. A reduction in the specific CO fume volumes relative to ANDEX LD is also achieved. On average the results show that, irrespective of the particle size, a reduction in the specific CO fume volumes of 40 to 50% is possible using the booster charge. An indicator of the improvement in the detonative reaction with decreasing particle size is represented by the velocities of detonation. With a decrease in the mean particle size of the emulsion granules, the velocity of detonation increases.
Below, the various emulsifiers were investigated. For this purpose, the formulations represented in table 4 were produced. The oversize of the fracture granules was removed by sieving with a sieve of mesh size 3.15 mm.
Table 5 shows that the resulting specific NOx fume volumes are influenced by the type of emulsifier. On average the highest specific NOx fume volume of 0.87 L/kg was measured for the granules produced using Anfomul™ S5. With the PIBSA-based emulsifiers from Lubrizol (2820) and Croda (Anfomul™ 2000), mean specific fume volumes in the region of 0.63 L/kg and 0.44 L/kg of NOx respectively, were measured. The granules with the Anfomul™ 2887 emulsifier give a specific NOx fume volume of 0.46 L/kg. In terms of the resultant CO fumes, no significant differences were observed. The influences of the different emulsifiers are attributable to the microstructures of the emulsion granules. The finer the distribution of the disperse phase within the granules, the lower the resultant toxic blasting fumes.
In this example, the composition of the fuel phase is altered by carbon carriers having different melting temperatures. An increasing melting temperature is generally accompanied by an increase in the strength of the substances. Through the targeted selection of corresponding components, therefore, it is possible to exert a direct influence over granule strength and caking tendency. An overview of the formulations is represented in table 6. The oversize of the fracture granules was removed using a sieve with a mesh size of 3.15 mm.
Table 7 represents the mean specific NOx fume volumes of the granules with different fuels in comparison to ANDEX LD. The alteration of the composition of the fuel phase with constant oxygen balance shows that this also affects the resultant blasting fumes. On average the lowest specific fume volume of 0.55 L/kg of NOx was measured for the formulation produced exclusively with stearic acid. Relative to the formulation composed of the combination with paraffin there is no significant difference apparent. If additionally, on a comparative basis, the strength and flowability of the bulk material are evaluated, they are preferably improved through the use of stearic acid. The incorporation of 1% of magnesium stearate does not result in any significant improvement in these properties, and the resultant NOx fume volume is also somewhat higher on average.
With the composition based on the exclusive use of stearic acid as essential carbon carrier and on a water fraction of 6.5% (cf. table 6), further tests were carried out. The oxygen balance of this formulation is minus 1.7% and the theoretical specific standard gas volume on complete reaction is 928 L/kg. Following production, the fracture granules were relieved of their coarse fraction >2 mm and of their fine fraction <1 mm by sieving. Relevant fume constituents were measured in accordance with the preceding description, except that is this example no booster charges were used—instead, exclusively electrical detonators were used for initiating the charge columns.
Table 8 represents the specific fume volumes of relevant gas components for ANDEX LD and for the emulsion granules with particle sizes in the 1-2 mm range, measured without a booster charge. With a mean specific fume volume of 0.26 LNOx/kg, it was possible to demonstrate a significant reduction in nitrogen oxides of 89% relative to ANDEX LD. Also, on average, a reduction in the CO fumes by 48% was achieved. The narrow particle size distribution of the emulsion granules, in the range from 1 to 2 mm, is therefore particularly advantageous for the quality of the reaction. This is critically attributable to the sensitization provided by the granular porosity. The flow behavior of the bulk product as well is improved considerably by the removal of the fine fraction <1 mm. The quality of the detonative reaction may be seen, furthermore, from the development in the velocity of detonation over the length of the charge column.
Production of a composition according to example 5 of CN 101555183 B:
The manufacturers thereof are those stated above and also Span 80, Sigma-Aldrich, Paraffin, VWR Chemicals,
and
Rosin, Acros Organics
After the emulsifying operation as described herein, the matrix was coated onto a steel plate and solidified by cooling. The solidified product was subsequently processed by comminution and sieving into granules having a particle size distribution in the range of 1-2 mm.
This reference example was investigated in comparison to the inventive example 4 in terms of NOx blasting fumes and velocity of detonation, as described above, by means of steel tube blastings:
The composition produced according to example 5 of CN 101555183 B as reference example gives off a significantly higher degree of nitrogen oxide compounds, under identical test conditions, than the inventive emulsion granules according to example 4. The granules described in the present invention achieve a mean specific fume volume of 0.26 LNox/kg; the explosive granules according to the prior art, CN 101555183 B, are situated at 5.74 LNox/kg.
From
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 004 567.7 | Jul 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/071140 | 7/28/2021 | WO |
