EP3659992B1

EP3659992B1 - Metallic mixture blasting capsule

Info

Publication number: EP3659992B1
Application number: EP18907112.9A
Authority: EP
Inventors: Claudio Nunez ASECIO; Chulwon KIM; Sung Kook Kim
Original assignee: Enaex SA
Current assignee: Enaex SA
Priority date: 2018-02-21
Filing date: 2018-02-21
Publication date: 2021-06-16
Anticipated expiration: 2038-02-21
Also published as: CO2020005323A2; PT3659992T; AU2018410014A1; AR111294A1; EP3659992A1; ES2886020T3; BR112020010200A2; BR112020010200B1; WO2019164027A1; EP3659992A4; PE20201324A1; AU2018410014B2; ZA202001878B; MX2020005672A

Description

[Technical Field]

The present invention relates to a metallic mixture blasting capsule, and more particularly to a metallic mixture blasting capsule including a metal salt as an oxidizing agent and a metal powder as a reducing agent.

[Background Art]

Korean Patent No. 10-0213577 discloses a rapidly expanding metallic mixture, comprising a metal salt as an oxidizing agent, a metal powder that is increased in volume through an exothermic reaction while being oxidized by the metal salt, and a reaction promoter for promoting the oxidation reaction of the metal salt and the metal powder. The metal salt is composed of a nitrate that oxidizes the metal powder and a metal oxide that determines the rate of oxidation of the metal powder while the metal powder is being oxidized. As the amount of metal oxide that is added increases, the rate of oxidation decreases. Examples of the metal salt include nitrates such as iron nitrate, copper nitrate, barium nitrate, manganese nitrate, magnesium nitrate, potassium nitrate, sodium nitrate, and calcium nitrate, and metal oxides such as diiron trioxide, triiron tetraoxide, copper oxide, manganese dioxide, dinickel trioxide, and lead oxide. The nitrate functions to oxidize the metal powder, and the metal oxide functions to oxidize the metal powder and also to determine the rate of oxidation of the metal powder. Examples of the metal powder include aluminum, manganese, magnesium, and other metals usable as reducing agents. The reaction promoter is composed of an oxidation promoter, which promotes the oxidation reaction of the metal salt and the metal powder when the rapidly expanding metallic mixture is operated by an electric spark and is operated by a primer, and an electric-spark induction electrolyte, which induces and promotes the oxidation reaction of the metal salt and the metal powder when the rapidly expanding metallic mixture is operated by an electric spark. As the oxidation promoter, sodium sulfate, magnesium sulfate, iron sulfate, manganese sulfate, nickel sulfate, calcium sulfate and other metal sulfates may be used alone or in combinations thereof, and as the electric-spark induction electrolyte, a solution resulting from dissolving a small amount of ammonium borate and nitrate or sulfate in glycerin or alcohol such as ethylene glycol may be used. The rapidly expanding metallic mixture is charged in a cartridge (or a capsule), and the positive electrode and the negative electrode, connected by a resistance wire, are buried in the rapidly expanding metallic mixture. Then, when a direct-current (DC) voltage of 3,000 V or more is applied to both electrodes, an electric spark at 1500° C or higher is generated between the electrodes by melting the resistance wire, whereby oxygen decomposed in the metal salt between the thermally shocked electrodes instantaneously combines with the vaporized metal powder, resulting in a chain oxidation reaction. As such, the metal powder is rapidly oxidized by the nitrate, and the metal powder is oxidized with a slight time difference by the metal oxide. When the oxidation reaction of the metal salt and the metal powder is initiated, a high temperature of 10,000° C or more is generated again and the metal powder in the cartridge is instantly oxidized, whereby the volume of the metal powder, the metal salt and the oxidation reaction product is rapidly expanded. When rock breaking is performed using such a rapidly expanding metallic mixture, the rock is cracked due to rapid volume expansion, and when the temperature is lowered, the oxidation reaction is immediately stopped and shrinkage takes place again, thus enabling safe rock breaking without vibration, noise or scattering of rock fragments. Accordingly, the rapidly expanding metallic mixture may be usefully employed in mining development and civil works.
However, the invention of Korean Patent No. 10-0213577 is problematic because it is difficult to trigger the initial oxidation reaction or to initiate the oxidation reaction even though an electric spark is applied.
In the rapidly expanding metallic mixture, which is stored and transported to the site in the state of being charged in the cartridge, there are many cases in which it is difficult to trigger the oxidation reaction even when an electric spark is applied. The reasons therefor are as follows.
In the rapidly expanding metallic mixture, the surface of the metal powder used as the reducing agent is easily oxidized when exposed to moisture or oxygen in the air. The metal powder surface thus oxidized has a very high melting point compared to unoxidized metal. When the metal powder is mixed with a metal salt, a reaction promoter and the like and is then charged in the cartridge, the metal powder is exposed to moisture or oxygen in the air and the surface thereof is oxidized, and thus, an oxidation reaction is not easily triggered (initiated) upon real-world application.
In order to prevent the metal powder from being oxidized and degraded, Korean Patent Application Publication No. 10-2003-0037707 discloses a method of adding oil or an inorganic preservative. However, when a resistance wire is used to connect the electrodes and a high voltage is applied thereto, an electric spark is generated in the path of the resistance wire by melting the resistance wire due to the large current. As such, the generated electric spark has a high temperature of 1,500° C or more to thus melt the electrodes, and thereby the electrodes disappear in an extremely short time. Meanwhile, since the oil or inorganic preservative hinders the instant transfer of the high temperature of the electric spark to the metal salt and the metal powder, the oil or inorganic preservative may interfere with the initiation of efficient redox reaction between the metal powder and the metal salt in the course of triggering the oxidation reaction.
As is apparent from a variety of test results, sodium sulfate, magnesium sulfate, iron sulfate, manganese sulfate, nickel sulfate, calcium sulfate, and other metal sulfates, which are used as the oxidation promoter in Korean Patent No. 10-0213577 , hinder the triggering of the initial oxidation reaction, and the electric-spark induction electrolyte, which is a solution resulting from dissolving a small amount of ammonium borate and nitrate or sulfate in glycerin or alcohol such as ethylene glycol, interferes with the generation of the electric spark and shortens the time for which the electric spark is maintained.
Despite the advantages of the rapidly expanding metallic mixture such as low vibration, low noise, and no scattering, the low likelihood of triggering or initiating the oxidation reaction of the rapidly expanding metallic mixture is regarded as a major cause of inhibiting the application of the rapidly expanding metallic mixture to the rock-breaking operation. In the case where the triggering of the oxidation reaction is low, rock breaking has to be repeatedly performed by eliminating the misfired cartridges from the rock and then installing new cartridges, thereby reducing the number of cartridges of the rapidly expanding metallic mixture that may be simultaneously blasted by applying the same amount of electric energy.
In order to solve the problem related to the low likelihood of triggering or initiating the oxidation reaction of the rapidly expanding metallic mixture, Korean Patent No. 10-0770316 discloses the use of a priming composition. Typically, a priming composition is an explosive that is used to cause combustion in gunpowder, and a mixture of lead thiocyanate and potassium chlorate or lead dinitrosoresorcinate is used as the priming composition that is ignited by an electric primer. The priming composition, such as a mixture of lead thiocyanate and potassium chlorate or lead dinitrosoresorcinate, has an ignition temperature of about 800° C upon ignition and thus has no problem in igniting a typical gunpowder, but is problematic because the ignition temperature thereof is too low to cause the triggering of the oxidation reaction of the rapidly expanding metallic mixture, which is composed mainly of the metal salt and the metal powder, making it impossible to trigger the oxidation reaction. For this reason, a method of igniting a rapidly expanding metallic mixture using the priming composition disclosed in Korean Patent No. 10-0770316 has not yet been used in the industry GB 1 205 378 discloses a method of cracking concrete, for example for demolition purposes; a squib is inserted into a cylindrical body filled with a combustible composition. JP 4 489142 discloses a stone crushing apparatus comprising an igniting composition and a high temperature high heat generation composition inside an insensitivity fracturing composition.

[Disclosure]

[Technical Problem]

Accordingly, the present invention has been made keeping in mind the problems with a conventional rapidly expanding metallic mixture encountered in the related art, and the objective of the present invention is to provide a metallic mixture blasting capsule using a rapidly expanding metallic mixture, which is able to easily initiate the oxidation reaction using an electric spark.

[Technical Solution]

In order to accomplish the above objective, the present invention provides a metallic mixture blasting capsule, comprising an outer cartridge, an inner cartridge, accommodated in the outer cartridge, a rapidly expanding metallic mixture, charged between the outer cartridge and the inner cartridge and comprising a sodium nitrate powder, a ferric oxide powder, an aluminum powder, a solid lubricant powder, and a glass filler powder, a rapid-trigger metallic mixture, charged in the inner cartridge and comprising a sodium nitrate powder, a ferric oxide powder, a copper oxide powder, an aluminum powder, and a magnesium powder of the higher weight percentage than aluminum powder, and an electric spark generation unit, embedded in the rapid-trigger metallic mixture.

[Advantageous Effects]

According to the present invention, unlike a conventional rapidly expanding metallic mixture, in which only electrode rods are provided, a material group in which a metal oxidation reaction occurs efficiently and accurately due to an electric spark (a rapid-trigger metallic mixture) is selected and then charged in the inner cartridge, after which the inner cartridge is embedded in the rapidly expanding metallic mixture accommodated in the outer cartridge, and the rapid-trigger metallic mixture in the inner cartridge is exploded by an electric spark. As such, the high heat thus generated causes the chain oxidation reaction of the rapidly expanding metallic mixture in the outer cartridge, whereby the triggering of the oxidation reaction of the rapidly expanding metallic mixture can be greatly improved, and moreover, the number of cartridges that can be simultaneously blasted by applying the same amount of energy can be increased at least ten times, thereby significantly improving the work efficiency of the rock-breaking site.

[Description of Drawings]

FIG. 1 is a cross-sectional view showing the outer cartridge, the inner cartridge and the electric spark generation unit of a metallic mixture blasting capsule according to an embodiment of the present invention;
FIG. 2 is an exploded view of the main part of FIG. 1;
FIG. 3 is a cross-sectional view showing a rapidly expanding metallic mixture and a rapid-trigger metallic mixture respectively charged in the outer cartridge and the inner cartridge of the metallic mixture blasting capsule of FIG. 1;
FIG. 4 is a cross-sectional view showing the outer cartridge, the inner cartridge and the electric spark generation unit of a metallic mixture blasting capsule according to another embodiment of the present invention; and
FIG. 5 is a cross-sectional view showing a rapidly expanding metallic mixture and a rapid-trigger metallic mixture respectively charged in the outer cartridge and the inner cartridge of the metallic mixture blasting capsule of FIG. 4.

[Mode for Invention]

Hereinafter, a detailed description will be given of a metallic mixture blasting capsule according to embodiments of the present invention with reference to the appended drawings.
The present invention includes a rapidly expanding metallic mixture, comprising a metal salt powder, serving as an oxidizing agent, a metal powder, which is increased in volume through an exothermic reaction while being oxidized by the metal salt powder, and a solid lubricant powder, which is loaded between powders to thus eliminate friction between the powders during mixing of the metal salt powder and the metal powder. As the oxidizing agent, the metal salt powder is preferably composed of a sodium nitrate powder and a ferric oxide powder, which are mixed at a weight ratio of 1:2 to 2:1, and the metal salt powder is preferably used in an amount of 50 wt% to 90 wt% based on the total weight of the rapidly expanding metallic mixture. The metal powder is preferably an aluminum powder, and is preferably used in an amount of 9 wt% to 45 wt%. The solid lubricant is preferably zinc stearate, and is preferably used in an amount of 1 wt% to 5 wt%. The rapidly expanding metallic mixture is capable of generating the rapid expansion force necessary to break rocks under the condition that the metal salt powder and the metal powder that is oxidized by the metal salt powder are uniformly mixed. To this end, the metal salt powder and the metal powder are uniformly mixed, and the solid lubricant powder is added thereto, thus preventing friction between powders during mixing and the generation of sparks due thereto, whereby the metal salt powder and the metal powder may be very uniformly mixed without fear of explosion.
Even when the mixture of the metal salt powder and the metal powder is combined with the solid lubricant powder, an air layer is formed between the powders, and moisture or oxygen in the air oxidizes the metal powder. In order to prevent the above problems, the rapidly expanding metallic mixture further includes a inorganic filler powder that is able to fill the space between the metal salt powder and the metal powder. The inorganic filler is preferably hollow glass bubbles, and is used in an amount of 1 wt% to 5 wt% based on the mass of the mixture of the metal salt powder and the metal powder.
The solid lubricant powder and the inorganic filler powder are components that are very useful for manufacturing the rapidly expanding metallic mixture and for preventing contact with air, but may act as obstacles in triggering the oxidation reaction of the rapidly expanding metallic mixture by the electric spark. Therefore, the present invention does not use the rapidly expanding metallic mixture to trigger the oxidation reaction around the electrodes.
As shown in FIGS. 3 and 5, a metallic mixture blasting capsule according to the present invention is configured to include an outer cartridge 1, which constitutes an outer cover thereof; an inner cartridge 7, having a diameter and a length smaller than those of the outer cartridge 1 and accommodated in the outer cartridge 1; a rapidly expanding metallic mixture 21 charged between the outer cartridge 1 and the inner cartridge 7 and comprising a sodium nitrate powder as an oxidizing agent, a ferric oxide powder as an oxidizing agent, an aluminum powder as a reducing agent, and a solid lubricant powder for removing friction in the aluminum powder, and a inorganic filler powder for filling an air layer between the powders; a rapid-trigger metallic mixture 23 charged in the inner cartridge 7 and comprising a sodium nitrate powder as an oxidizing agent, a ferric oxide powder as an oxidizing agent, a copper oxide powder as an oxidizing agent, an aluminum powder as a reducing agent, and a magnesium powder as a reducing agent; and electric spark generation units 11a, 11b, 13 embedded in the rapid-trigger metallic mixture 23.
The rapidly expanding metallic mixture 21 and the rapid-trigger metallic mixture 23 differ in composition. The rapid-trigger metallic mixture 23 excludes the solid lubricant and the inorganic filler which are included in the rapidly expanding metallic mixture 21, and contains copper oxide, which is not included in the rapidly expanding metallic mixture 21 and has relatively low oxygen content but releases oxygen at a comparatively low temperature, as the oxidizing agent, and magnesium powder, which is not included in the rapidly expanding metallic mixture 21 and has weak expansion force due to relatively low heat generated upon oxidation but is oxidized at a comparatively low temperature, as the reducing agent. The ferric oxide releases oxygen at a high temperature compared to the sodium nitrate, and the copper oxide releases oxygen at a low temperature compared to the sodium nitrate. Magnesium is rapidly subjected to an exothermic reaction with oxygen at a low temperature compared to aluminum. Therefore, such a difference in composition brings a great difference in the ease of triggering the oxidation reaction between the rapidly expanding metallic mixture 21 and the rapid-trigger metallic mixture 23.
In the metallic mixture blasting capsule according to the present invention, the rapid-trigger metallic mixture 23, which excludes the solid lubricant and the inorganic filler, and contains copper oxide, which has relatively low oxygen content but releases oxygen at a comparatively low temperature, as the oxidizing agent, and magnesium powder, which has weak expansion force due to relatively low heat generated upon oxidation but is oxidized at a comparatively low temperature, as the reducing agent, is charged in the inner cartridge 7 and thus disposed around the electric spark generation units 11a, 11b, 13, whereby the oxidation reaction is triggered very quickly without failure due to the electric spark.
On the other hand, only the aluminum powder, having high heat generated upon oxidation and thus very large expansion force but being oxidized at a comparatively high temperature, is contained in a large amount as the reducing agent in the outer cartridge 1, thereby maximizing the expansion force of the metallic mixture blasting capsule.
In the rapid-trigger metallic mixture comprising the sodium nitrate powder, ferric oxide powder, copper oxide powder, aluminum powder, and magnesium powder, 10 wt% to 27 wt% of the sodium nitrate powder, 15 wt% to 30 wt% of the ferric oxide powder, 10 wt% to 28 wt% of the copper oxide powder, 5 wt% to 14.99 wt% of the aluminum powder, and 15 wt% to 28 wt% of the magnesium powder are mixed based on the total weight thereof. At this time, the weight ratio of the magnesium powder to the total powder is always higher than the weight ratio of the aluminum powder to the total powder. When the aluminum powder weight ratio is higher than the magnesium powder weight ratio, the oxidative triggerability is greatly reduced.
The rapidly expanding metallic mixture may further comprise a waterproofing agent in a small amount (less than 2% based on the total mass thereof). The waterproofing agent is preferably oil.
As shown in FIG. 1, when the outer cartridge 1 is short, only one end thereof is joined to the inner cartridge 7 and the remaining end thereof is sealed with an outer cartridge bottom cap 5.
As shown in FIG. 2, in order to join the inner cartridge 7 to the inside of the outer cartridge 1, the central portion of an outer cartridge top cap 3 is formed in a hollow shape, and the inner cartridge 7 and the inner cartridge top cap 19 are joined to the central portion of the outer cartridge top cap 3. The electrodes 11a, 11b fixed by electrode holders 15 are provided in the inner cartridge 7 and the inner cartridge top cap 19. The electrodes 11a, 11b are connected to a DC high-voltage generation device (not shown) by means of lead wires 21a, 21b passing through the inner cartridge top cap 19. The inside of the inner cartridge top cap 19 is sealed by the electrode holders 15 made of rubber or silicone, and the upper lead wires 21a, 21b of the inner cartridge top cap 19 are wrapped with a lead wire sealant 17 made of rubber or silicone so as to completely block the inflow of air or moisture into the inner cartridge. The lower end of the inner cartridge 7 is sealed with the inner cartridge bottom cap 9a. The joined portion between the outer cartridge bottom cap 5 and the outer cartridge 1, the joined portion between the outer cartridge top cap 3 and the outer cartridge 1, the joined portion between the outer cartridge top cap 3 and the inner cartridge top cap 19, and the joined portion between the inner cartridge top cap 19 and the inner cartridge 7 are completely sealed by means of an adhesive.
The inner cartridge top cap 19 is injected, and the lead wire sealant 17 and the electrode holders 15 are molded in the state in which the lead wires 21a, 21b and the electrodes 11a, 11b are inserted into the inner cartridge top cap 19, whereby the inner cartridge top cap 19, the lead wires 21a, 21b, the lead wire sealant 17, the electrode holders 15, and the electrodes 11a, 11b are integratedly formed. The inner cartridge is joined to the inner cartridge top cap 19 in the state in which the inner cartridge 7 is filled with the rapid-trigger metallic mixture 23. In this procedure, the electrodes 11a, 11b are embedded in the rapid-trigger metallic mixture 23. Thereby, the airtightness of the inner cartridge 7 may be completely ensured.
A resistance wire 13 for connecting the positive electrode 11a and the negative electrode 11b is connected to the lower ends of the electrodes 11a, 11b, and the DC high-voltage generation device functions to apply a high voltage of 3 KV or more to the electrodes 11a, 11b, and thus an electric spark occurs between the two electrodes by melting the resistance wire.
As shown in FIGS. 4 and 5, when the outer cartridge 1 is long, each of both ends thereof is provided with an inner cartridge 7, and the rapid-trigger metallic mixture 23 and the electrodes 11a, 11b are provided to each inner cartridge 7 so as to simultaneously cause explosions at both ends of the outer cartridge 1. Furthermore, the inner cartridge bottom cap 9b is formed in a shape that is tapered toward the tip thereof, whereby the inner cartridge 7 may be easily inserted into the rapidly expanding metallic mixture 21 in the outer cartridge 1.
As described above, in the metallic mixture blasting capsule according to the present invention, the outer cartridge 1 is filled with the rapidly expanding metallic mixture 21 and the rapid-trigger metallic mixture 23, which facilitates the triggering of the oxidation reaction, is contained in the small inner cartridge 7, and the inner cartridge is embedded in the central portion of the outer cartridge, and the electric spark generation units 11a, 11b, 13 are provided in the inner cartridge 7 to thus accurately and rapidly perform an explosion reaction.
The metallic mixture blasting capsule according to the present invention is configured such that the rapid-trigger metallic mixture 23 in the inner cartridge 7 is ignited using an electric spark and is thus exploded, and thus the rapidly expanding metallic mixture 21 in the outer cartridge 1 is ignited by the explosion of the rapid-trigger metallic mixture 23, thereby remarkably increasing the reaction success rate of the metallic mixture blasting capsule using the rapidly expanding metallic mixture. Moreover, the number of cartridges that may be blasted simultaneously by applying the same amount of energy may be increased at least ten times, thereby significantly improving on-site work efficiency.

[Industrial Applicability]

The metallic mixture blasting capsule according to the present invention is capable of maximizing the effects of low noise and low vibration, which is a requirement of conventional inventions for real-world application (civil engineering, mining development, etc.), and of completely eliminating the failure rate of explosion to thus ensure stability, thereby enabling safe construction, and furthermore, work efficiency may be increased at least ten times, ultimately generating economic benefits.

Claims

A metallic mixture blasting capsule using a rapidly expanding metallic mixture, comprising:
an outer cartridge;

an inner cartridge, accommodated in the outer cartridge;

a rapidly expanding metallic mixture, charged between the outer cartridge and the inner cartridge and comprising a sodium nitrate powder as an oxidizing agent, a ferric oxide powder as an oxidizing agent, an aluminum powder as a reducing agent, a solid lubricant powder for removing friction in the aluminum powder, and a inorganic filler powder for filling an air layer between the powders;

a rapid-trigger metallic mixture, charged in the inner cartridge and comprising a sodium nitrate powder as an oxidizing agent, a ferric oxide powder as an oxidizing agent, a copper oxide powder as an oxidizing agent, an aluminum powder as a reducing agent, and a magnesium powder of the higher weight percentage than aluminum powder as a reducing agent; and

an electric spark generation unit, embedded in the rapid-trigger metallic mixture.
The metallic mixture blasting capsule of claim 1, wherein the solid lubricant is zinc stearate.
The metallic mixture blasting capsule of claim 1, wherein the inorganic filler powder is glass bubble.
The metallic mixture blasting capsule of claim 1, wherein the rapid-trigger metallic mixture comprises 10 wt% to 27 wt% of the sodium nitrate powder, 15 wt% to 30 wt% of the ferric oxide powder, 10 wt% to 28 wt% of the copper oxide powder, 5 wt% to 14.99 wt% of the aluminum powder, and 15 wt% to 28 wt% of the magnesium powder are mixed based on the total weight thereof.