HK1201252A1 - Modified blasting agent - Google Patents

Abstract

The present invention relates generally to an explosive composition comprising an aqueous emulsion of: an oxidizer component, a hydrocarbon fuel component containing emulsifier, and a bulking agent being a fuel-type waste material in a solid particulate form substantially lacking rough surfaces and sharp edges. Preferably the composition is of an ammonium nitrate based emulsion and a pelletised bulking agent. It also involves a method of providing an explosive composition to a blast site using a conventional mobile processing unit (MPU), being a truck having separate compartments adapted for holding fuel oil, dry ammonium nitrate prill, and ammonium nitrate based emulsion, where a compartment instead holds particulate waste material. It also concerns a method of blasting soft and wet ground, which comprises injecting into one or more blast holes in the soft and wet ground a sufficient quantity of the composition, and then setting off the composition.

Description

Improved blasting agent

Technical Field

The present invention relates generally to blasting agents and explosive compositions and to methods of making, using, and delivering such agents. More particularly, the present invention relates to multi-component explosive formulations utilizing waste materials that are not otherwise shipped to landfills or high temperature incineration. In particular, although not exclusively, the invention relates to the production, use and delivery of blasting agents comprising various forms of ammonium nitrate based emulsion explosives, which have been improved by the incorporation of waste material as an explosive component.

Background

Once the material has been used for a certain purpose or is a by-product of an industrial process, it becomes a waste material. There are generally many different ways in which it can be managed in order to dispose of it safely and environmentally. One way is separation, recovery and ultimate reuse. Another way is to produce the material from a material that is readily biodegradable; thus, the material has a shorter life time when disposed of at the end of a landfill than non-biodegradable material.

However, there are some materials that cannot be recycled or made of biodegradable materials. In this case, the material is managed by burning or burying it in a landfill where it will only slowly degrade. Disposal of waste in a landfill limits the use of this land, for example some waste such as plastics take 400 years to decay. Burning waste materials such as plastics often requires high temperatures, which is difficult and costly to achieve. But this process can also release harmful contaminants, often in industrial areas where contamination can already be a problem.

One way to address these problems is to incorporate waste materials that are so difficult to recover or degrade into explosive compositions that the extreme conditions and high temperatures generated upon detonation of such explosive compositions achieve the goal of disposing of the material in a manner similar to high temperature incineration, but achieve useful results and may be less costly.

This approach has previously proven to be achievable with the addition of rubber particles and solid ammonium nitrate as disclosed in U.S. patent No.5,505,800(Harries et al). This reference is primarily directed to the production of "low impact energy explosives" (LSEE). The rubber may originate from tires used in shredded form. However, the resulting rubber particles have rough edges, which since been found to cause crystallization in explosive mixtures when the rubber is mixed with ammonium nitrate based emulsions. Crystallization can prevent the mixture from detonating or will produce undesirable results.

Another attempt to use waste in this manner, as disclosed in U.S. patent No.5,536,897(Clark et al), involves blending the energy waste with different explosive compositions such as AN, ANFO, hydrogels, and emulsions. This reference generally relates to the use of rocket fuel contaminated waste. The waste is then broken up. The presence of residual rocket fuel in the waste ensures that the waste contributes to the explosive properties of the final explosive. However, the absence of such fuels in the waste material may result in the explosive composition not detonating.

The presence of broken materials in the emulsion blend may produce materials with rough edges and these edges may cause the product to crystallize. Product crystallization can lead to poor explosive performance, reduced water resistance and increased risk of smoke generation after blasting.

It would therefore be useful to provide a solution that avoids or ameliorates any of the disadvantages present in the prior art, or to provide another alternative to the prior art processes.

Disclosure of Invention

According to one aspect of the present invention there is provided an explosive composition comprising an aqueous emulsion of an oxidant component, a hydrocarbon fuel component containing an emulsifier and as filler a fuel based waste material in the form of solid particles substantially free of rough surfaces and sharp edges, insufficient to promote crystallisation of the emulsion.

Another aspect of the invention involves a method of providing an explosive composition to a blast site having one or more blastholes for containing the composition by means of a conventional Mobile Processing Unit (MPU), the unit comprising a truck having separate compartments adapted to contain (a) a hydrocarbon fuel component, such as fuel oil, (b) a dry oxidizer component, such as dry ammonium nitrate prills, and (c) a wet oxidizer component, such as an ammonium nitrate-based emulsion, and the unit having means for mixing together two or more components from compartments (a), (b) and (c) and injecting the resulting mixture into the blastholes, characterized in that compartment (b) is instead containing a bulking agent in the form of particulate waste material, and wherein a density reducing agent is added to the mixture from compartments (a), (b) and (c) prior to injecting it into the blastholes, preferably with an auger on the MPU, and wherein the composition is as described herein.

Yet another aspect of the invention relates to a method of blasting soft, moist ground comprising injecting into one or more blastholes in the soft, moist ground a sufficient amount of a composition according to the invention and then detonating the composition.

The oxidizer component of the emulsion is typically an aqueous solution or melt containing an oxygen-releasing salt. Preferably the oxygen-releasing salt is selected from one or more of ammonium nitrate, sodium nitrate, calcium nitrate or ammonium perchlorate, and most preferably ammonium nitrate.

Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 is a schematic view of a truck that can be used to deliver a blasting explosive according to the invention:

figures 2a and 2B show photographs (not to scale) of two products (a & B) of waste pellet components useful in the present invention; and is

Figure 2c shows a photograph (not to scale) of a waste pellet product B (figure 2B) showing its smooth appearance that can be used in the present invention,

FIG. 2d shows a photograph (not to scale) of another waste pellet product for use in the present invention, and

figures 3a and 3b show photographs (not to scale) of comparative rejects not forming part of the invention, showing the rough and jagged nature of their surface and the presence of sharp edges and corners.

Detailed Description

According to the present invention, AN explosive composition is provided, preferably comprising AN emulsion based on Ammonium Nitrate (AN) type and waste material as filler. The waste material is in the form of solid particles.

The waste is a fuel-based waste, typically a waste that can be burned at high temperatures in the presence of an oxidant. Typically such waste may be carbonaceous materials such as waste plastics, rubber, paper, wax and the like. Some suitable waste sources include nylon pellets, cardboard, polyethylene, wax, and hybrid plastic waste. Preferably the solid particulate form is in the form of pellets or waste. Some other suitable waste sources include easily oxidizable metals such as aluminum.

Miscellaneous plastic waste derived from plastic from domestic waste collection, including large amounts of polyethylene and similar plastics, may be utilized. These fines are typically chopped and ground into a powder, and the powder is melted or pressed together and then extruded to form smooth surfaced, rounded corners and edges of the waste plastic pellets. Other materials such as hybrid paper and paperboard waste, optionally, may be shredded and pressed together with waxy waste to form smooth pellets with rounded edges.

The waste material is in granular or particulate form, preferably having an average particle size of from 0.5 to 1.0mm, and more preferably from about 1 to 4mm, and most preferably from about 2 to 3 mm. These pellets may be spherical, cylindrical, cubic, in square or rectangular blocks or irregular in shape, typically having smooth surfaces and rounded edges.

It is also a preferred feature that the granulated waste material in particulate form should have a similar size to the solid particulate AN pellets in the blasting composition. AN pellets are typically between 1-4mm in size, so it is advantageous to use a particulate waste material with a similar size distribution. The loading apparatus is able to operate effectively with pellet particles so by using waste particles of similar size the apparatus will also operate effectively with it.

It is also advantageous that the density of the waste is not too low, since it is known to add very low density additives, such as microspheres or styrene beads, as sensitizers. Preferably, the waste particles may have a density of 0.2-1.0g/cm³About, and more preferably 0.4 to 0.7g/cm³Left and right. Ideally, the waste particles themselves must not substantially affect the sensitization of the blasting emulsion.

As described in more detail below, these waste particles should have a relatively smooth surface and very small sharp edges, which is sufficient that they do not destabilize the emulsion, or promote emulsion crystallization. The stability of the emulsion can be measured using the Rod Rating test (Rod Rating test) described below, and preferably, waste type pellets that provide Rod Rating test results of 6 or higher when mixed with AN emulsion are desirable for the present invention.

Figures 2a, 2b, 2c and 2d show photographs (not to scale) of some pellet samples that may be used in the present invention. The samples in fig. 2a originate from paper and cardboard. The samples in fig. 2b, 2c and 2d show samples derived from waste plastic. In these samples, high density waste polyethylene was the major component. These samples showed smooth outer surfaces and rounded edges and corners. In contrast, the samples shown in the photographs of fig. 3a and 3b show prior art fillers having rough surfaces, sharp edges and corners and sharp whiskers that break the emulsion if these are used in a similar blasting composition.

The advantage of waste materials is that they are discarded and therefore would be a cost-effective material if used. Use of it also allows for the removal of waste from the environment by incineration in an explosion. Alternatively, the new plastic may be used as a source of some (or all) of the fuel-based waste. The term "waste" is to be interpreted broadly in the present invention and at the same time it is preferred to use plastic waste, recovered from other applications, also allowing the use of virgin material if the same purpose is fulfilled. Because of their low cost, there is a tendency to use recycled waste as a primary source, but sometimes such materials may be lacking, or the temporary price rises, or the demand for blasting compositions unexpectedly increases, in which case the waste can be replaced with some new material.

In addition, other difficulties or costs of disposing of materials may be included in the waste, especially in addition to being potentially expensive to dispose of in high temperature incinerators. Waste disposal companies may pay to add these components to the explosive by incorporating them into the particulate waste material, thereby improving the economic efficiency of producing the blasting agent of the invention. Any such material should be included if small amounts are not obtained to be completely incinerated without destroying the environment. This option is also advantageous if blasting is used on coal, for example combustion to generate electricity, so that any such material will burn under any circumstances. Such materials are desirably carbon-containing waste products that would otherwise be incinerated but which may be included in the blasting composition. Colorants such as organic waste dyes and similar materials may be examples of such materials.

The oxidizer component used in the present invention is preferably AN Ammonium Nitrate (AN) based emulsion. However, other oxidizers may be used instead of or in addition to ammonium nitrate. These may include alkaline earth metal nitrates (e.g., calcium nitrate) or alkali metal nitrates (e.g., sodium nitrate) and urea (urea). Some other examples may include alkaline earth or alkali metal perchlorates such as ammonium perchlorate, although these are less commonly used due to environmental concerns. Most preferably, an aqueous solution of ammonium nitrate is used alone as the oxidizing agent.

The hydrocarbon fuel component of the present invention is typically a fuel oil such as mineral oil or diesel oil used in the quarrying, mining and civil construction industries with conventional ANFO blasting explosives.

The hydrocarbon fuel component contains AN emulsifier, which is generally any emulsifier used with AN emulsion explosive. A single emulsifier or a combination of emulsifiers may be used. Some preferred emulsifiers may be selected from the group of emulsifiers produced by condensation reactions between PIBSA and amines or alkanolamines. Another example of a suitable emulsifier is sorbitan monooleate (sorbitan mono-oleate) and the like. Preferably the emulsifier may be selected from poly (isobutylene) succinic anhydride or at least one derivative of poly (isobutylene) succinic emulsifier with diethylethanolamine or other alkanolamines. The emulsifier preferably constitutes 0.3-3.5% by weight and most preferably 0.5-1.5% by weight of the total composition.

Most preferably, the waste material used is such that, when mixed with the other AN emulsion components, the emulsion is not sensitized to allow for explosions. This acts as a safety feature to prevent accidental initiation of an uncontrolled explosion.

Ideally, it is preferred to sensitize the mixture of AN emulsion and waste by adding a separate sensitizing component when injecting it into the wellbore. The sensitizing component can be density-reducingSmall dose. One preferred example of a suitable such sensitizer is an alkali metal nitrate and an acid which, when mixed together, generate nitrogen gas, thereby reducing the density of the explosive blasting emulsion. Ideally, the density of the emulsion is reduced to less than 1.15g/cm by selecting an appropriate amount of sensitizer to mix with the emulsion³And preferably between 0.80g/cm³And 1.15g/cm³In the above-mentioned manner,

the particulate waste is in the form of solid particles having particles substantially free of rough surfaces and sharp edges. This feature does not promote emulsion crystallization. The lack of sharp/rough edges does not provide a means of disruption and therefore does not provide for crystallization of the emulsion droplets.

A number of simple tests may be performed to test whether potentially suitable waste particles will function in the present invention. Ideally, any waste product could be utilized if it could be oxidized in the resulting explosion and not destabilize the emulsion. Also preferably, the waste product must not provide sensitization to the product to allow the explosive agent to be separately sensitized when pumped into the blasthole, for example by aerating the emulsion to reduce its density.

Preferably, the waste particles are in the form of pellets, ideally pellets having rounded and smooth surfaces and edges. These pellets may have AN average particle size similar to AN AN pellet, for example, desirably about 2-3mm in diameter.

Preferably, when all components are combined prior to initiating an explosion, the waste comprises 1% to 50% by weight of the total composition. More preferably, the waste material comprises 10% to 40% of the composition.

The blasting agent of the present invention is particularly useful in wet soft ground. Typically, explosive compositions have good water resistance if an emulsion content of 60% or more is present in the explosive. Thus, the explosive compositions of the present invention are generally well suited for use on wet floors.

Soft ground requires less energy to move the ground. The calculated ANFO energy was 3.7MJ/kg compared to 2.0MJ/kg for one of the formulations of the present invention. The relative weight strength of the formulation was 0.54 compared to 1.0 ANFO and the relative bulk strength at 1.05g/cc density was 0.69 compared to 1.0 ANFO. This product therefore has less energy than ANFO or even emulsion-ANFO blends and is therefore more suitable for soft ground.

Preferably, the compositions of the present invention are delivered to the site to be blasted using a conventional Mobile Processing Unit (MPU) truck that transports the components in the section typically used to contain conventional AN emulsion blasting agent components. The waste material is stored in and derived from a storage container reserved for ammonium nitrate added for drying, part (b). The explosive composition was delivered by augers of the MPU. It is desirable to add a density reducing agent to the explosive composition before it exits the auger into the blasthole.

Examples

Laboratory batches of ammonium nitrate-based emulsions were produced as follows. Table 1 lists the ingredients and weights used to produce the emulsion. Other formulations are also within the scope of the invention.

General emulsion production Process

The components of the oxidant phase were heated to 75 ℃ to form an aqueous solution. Separately, the components of the fuel phase were mixed while heating to 65 ℃. The hot oxidant phase was then slowly poured into the fuel phase using a syringe equipped with 65mm "Jiffy^TM"lightning' Labmaster with stirring blades^TM"Mixer, begin to rotate at 600rpm for 30s to provide agitation. The crude emulsion was refined by stirring at 1000rpm for 30s, 1400rpm for 30s and 1700rpm until the specified viscosity was reached. The amount of product prepared in each sample was 2.0 kg.

This represents a standard formulation for use as a source of emulsion for different blends. The formulations are shown in table 1 below.

The emulsion is selected from the group of emulsifiers resulting from the condensation reaction between PIBSA and an amine or alkanolamine. The mineral oils used are mainly paraffinic with some aromatic and naphthalene building blocks. An emulsion with a viscosity of about 25,000cP was formed.

TABLE 1 Standard emulsion formulation

Oxidant component	94％
		-ammonium nitrate	75％
-water	25％
		Hydrocarbon fuel component	6％
-emulsifiers	15％
		-mineral oil/fuel oil	85％

Table 1.

The waste material is supplied by "australian composite technology" company ("plasma") of victoria, australia. In these examples, the material is supplied in either a crushed form or as pellets. The broken material typically has sharp edges and this leads to instability of the ammonium nitrate based emulsion due to the sharp edges interacting with the droplets in the emulsion and causing crystallization. In another form, the pelleted material will not generally destabilize the emulsion, although this will also depend on the material used.

Four materials were tested, these included (1) nylon pellets, (2) cardboard pellets, (3) pellets composed of a mixture of cardboard, polyethylene, and wax (referred to as "product a") and (4) pellets composed of a hybrid plastic (referred to as "product B"). A photograph of product a is shown in the drawing (not to scale) in figure 2a, and a photograph of product B is shown in figure 2B, in which a scale is shown, indicating that the particle diameter is about 3 mm.

It should be noted that paperboard does contain some coarse fibers and in theory, this results in an unstable emulsion. However, if the board is pelletized, this effectively reduces the surface area with which some ammonium nitrate-based emulsions can be used. In particular, whereby the fuel phase consists only of emulsifiers and mineral oils, formulations without the presence of diesel oil appear to be particularly suitable in this combination.

In order to maintain the water-resistance of the emulsion, at least 50% of the emulsion should be maintained in the blend, although it should ideally be 60% or higher. Conversely, the level of waste material may be between 1-50%, although it will preferably be between 10 and 40%.

Dry blends may be added to the ammonium nitrate-based emulsion. The dry blend may consist of ammonium nitrate or a mixture of ammonium nitrate and diesel oil (ANFO). If used, the dry additives comprise 0-40% by weight of the total composition. The burst side may be modified by adding ANFO, for example by providing more tension to the burst side.

The scrap is preferably pelletized so as to provide a dense structure without any significant voids in the material. Thus, the waste material does not provide sensitization and does not participate in the explosive reaction. Furthermore, the size of the material, about 3mm in size, means that there is decoupling between the oxidant and the fuel. This was observed when the product B pellets were mixed with ammonium nitrate in a ratio of 93 wt.% ammonium nitrate and 7 wt.% pellets. The product was ignited in 223mm diameter PVC pipe without the composition detonating. Only when 1.5% of the ammonium nitrate was replaced with diesel oil, the material detonated at 1,700m/s in the low position.

Sensitization is provided by the addition of a density-reducing agent. Such density-reducing agents may be any of a number of described in the art, such as glass or plastic microspheres, enclosed air, or chemically aerated. It is preferred to use an alkali metal nitrite such as sodium nitrite or potassium nitrite for chemical gassing of the material. Typically, a 20-30% sodium nitrite solution is added to the acidified ammonium nitrate based emulsion. The nitrous acid ions are protonated and then reacted with ammonium ions to generate nitrogen gas. The gas generation is usually completed within 20-60 minutes. The amount of sodium nitrite solution used determines the final density of the explosive composition. The density of the final explosive composition should ideally be less than 1.15gm/cm³And most preferably between 0.8 and 1.15g/cc to ensure that the composition will detonate.

Embodiments of the invention are shown below. Are examples only and are not intended to limit the invention in any way.

Comparative example 1 (not according to the invention)

In a first embodiment, not part of the invention, 70% by weight of TITAN is used^TMThe 2000 emulsion was blended with 30 wt% ANFO. The mixture was acidified with a 50% acetic acid solution and then a 25% sodium nitrite solution was added to the explosive composition at 0.30% by weight of the total explosive composition. This addition reduces the explosive composition from 1.32g/cc to 1.10 g/cc. The explosive composition was charged into 102mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record 4,000m/s VOD. The stability of the mixture was determined after 28 days on a bar scale of 6.

Comparative example 2 (not according to the invention)

In a second embodiment, not part of the invention, 80% by weight of TITAN is used^TMThe 2000 emulsion was mixed with 20 wt% product B and did not increase sensitization. The mixture had a density of 1.17g/cc and was packed into 152mm diameter PVC tubing and detonated. Upon initiation of a 400g Pentolite booster equipped with a #12 strength detonator, the product failed to detonate. These results indicate that product B did not provide emulsionAnd (4) sensitizing.

The following examples show that sensitization is required.

Example 3

In a third example, 80% by weight of TITAN was added^TM7000 emulsion was mixed with 20% by weight of product B. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.3% by weight of the total explosive composition. This addition reduces the explosive composition from 1.27g/cc to 1.10 g/cc. The explosive composition was charged into 152mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record VOD of 3,800 m/s. The bar rating for stability of the mixture was determined to be 6 after 20 days and the blend decomposed after 28 days.

Example 4

In a fourth example, 80% by weight of TITAN was added^TM2000 emulsion was mixed with 20 wt% of product B. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.2% by weight of the total explosive composition. This addition reduces the explosive composition from 1.17g/cc to 1.02 g/cc. The explosive composition was charged into 152mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record 4,000m/s VOD. The stability of the mixture was determined after 28 days on a bar scale of 7.

Example 5

In a fifth example, 80% by weight of TITAN was added^TM7000 emulsion was mixed with 20% by weight of product B. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.2% by weight of the total explosive composition. This addition reduces the explosive composition from 1.22g/cc to 1.03 g/cc. Will be provided withThe explosive composition was charged into 152mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record a VOD of 5,100 m/s.

Example 6

In a sixth example, 60% by weight of TITAN was added^TM2000 emulsion was blended with 10 wt% product B and 30 wt% ANFO. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.2% by weight of the total explosive composition. This addition reduces the explosive composition from 1.23g/cc to 1.12 g/cc. The explosive composition was charged into 152mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record 4,500m/s VOD.

Example 7

In a seventh example, 60% by weight of TITAN^TMThe 2000 emulsion was blended with 20 wt% product B and 20 wt% ANFO. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.1% by weight of the total explosive composition. This addition reduces the explosive composition from 1.18g/cc to 1.10 g/cc. The explosive composition was charged into 152mm diameter PVC pipe and detonated using 400g Pentolite booster equipped with a #12 strength detonator. Record 4,200m/s VOD.

Example 8

In an eighth example, 80% by weight of TITAN was added^TM7000 emulsion was mixed with 20% by weight of product B. The mixture was acidified with a 50% acetic acid solution and then a 25% by weight sodium nitrite solution was added to the explosive composition at 0.1% by weight of the total explosive composition. This addition reduces the explosive composition from 1.22g/cc to 1.15 g/cc. The explosive composition is charged into a 152mm diameter PVC pipe and the use equipmentA400 g Pentolite booster of #12 strength detonator was detonated. Record 4,900m/s VOD.

Bar rating test

The stability of the various components was tested as shown in table 2. This test involves mixing the filler, ANFO and/or emulsion and then monitoring the level of crystallization in the emulsion as a function of time. This was achieved by dipping a 10mm glass rod at a 45 degree angle into the blend to a depth of about 20mm to coat one side of the glass rod with the blend. The glass rod was then gently tapped to remove excess filler, spherulites and/or emulsion. The glass rod was placed toward the light source, the emulsion coated side face was back lit and light was passed through the glass rod. The emulsion was then gently rubbed 3 times along the glass rod and the proportion of crystals was measured as follows: -8 ═ no crystals; 7 ═ a few crystals; 6-half emulsion/half crystal; 5-predominantly crystalline, with some emulsions; all 4 are crystalline, no emulsion. The proportion of crystal formation continues to be evaluated over time for the blend at known intervals.

Example 9 stability test

According to the invention, 80% by weight of TITAN are used^TMThe 2000 emulsion was mixed with 20 wt% product B and aerated to a density of 0.99g/cc for the first test, and this resulted in a bar rating of 7 after 28 days.

In contrast, testing with other materials as waste components produced poorer results for emulsion stability. It is highly preferred that such emulsions must be stable for at least 14 days, and preferably for 28 days. The test for stability is preferably a bar rating test as described herein and suitably the stability will be such that the emulsion has a bar rating of 6 or more for at least 14 days.

The results of these tests are given in table 2 below.

TABLE 2 stability test

From the micrographs of the various wastes tested in figures 3a, 3b and 3c, it can be seen that the waste according to the invention in figure 3a has a significantly smoother surface and edges than the shredded tyre in figure 3b or the hybrid plastic in figure 3 c. The stability test in table 2 shows that crystallization occurred and thus destabilized the emulsion.

Example 10 blasting test

The test was carried out in the field using a blasting composition with pellets according to fig. 2b and 2d as filler. And selecting a site, and drilling blast holes for the natural surface at the site.

The results of these tests are given in table 3 below.

Sample (I)	Volume (kg/eye)	Depth of blast hole (m)	Density (g/cm3)	VOD(m/s)
					2b	250	8-10	1.02–1.04	3000
2b	230-310	7-8	0.98–1.06	3800
					2d	250	8	0.94–0.98	3900

TABLE 3

The burst test involves loading several blastholes with an emulsion according to the invention. The test was performed 3 shots and the results are shown in table 3. The product detonates to a high position and a steady state. No smoke was observed for any location containing the blasting emulsion including the waste material filler.

Delivery of explosive compositions

Figure 1 shows a schematic view of a truck used in a mine site for the production and delivery of bulk explosives into blastholes. The truck 1, also called Mobile Processing Unit (MPU), has 3 sections 10, 20, 30. The first and smallest portion 10 is typically used to store fuel that traditionally contains only about 6% of the ANFO component. The second section 20 is typically used to store ammonium nitrate for dry addition. The third section 30 is used to store an ammonium nitrate based emulsion.

Preferably the scrap is approximately spherical in shape and about 2-3mm in size. This size and shape gives the material a fluidity similar to that of ammonium nitrate for dry addition. Thus, the waste material may be substituted into the second portion 20 of the truck. The lack of waste fines and flowability allows the second portion 20 to be used with any material (waste pellets or AN pellets) that does not have significant contamination problems. Furthermore, the lack of scrap sensitivity means that even if some residual scrap is present in this section 20, the ammonium nitrate prills are not provided with a source of fire or with fuel. The MPU truck can therefore be used in either arrangement and readily changed to deliver either set of blast components.

The MPU truck 1 has an auger 40 that mixes the waste with the emulsion. A density-reducing agent may also be added to the mixture to reduce the density of the explosive composition. If the density-reducing agent is an alkali metal nitrite, a saline solution may be applied to the auger arm 42 through an inlet (not shown). The explosive composition is conveyed out of the auger 40 into the blasthole (not shown).

The blasting composition and the method of delivering it to a blasthole according to the invention are particularly beneficial in blasting soft, wet ground, such as natural surfaces. The invention is also beneficial when smoke mitigation is important, as blasting produces minimal smoke, and in particular toxic NO is produced when sensitised with nitrogen in the composition_xAnd (4) smoke.

In the present invention, unless the context clearly dictates otherwise, the term "comprising" has a non-exclusive meaning in the sense that the term "comprises at least" and not an exclusive meaning in the sense that "consisting of … … only" is used. It applies to other forms of the word such as "comprising", "comprises", etc., in corresponding grammatical variations.

Although the invention has been described above with reference to specific embodiments, a person skilled in the art will recognize that it is not limited to the embodiments described, but may also exist in many other forms.

Industrial applicability

The invention may be used in industries where blasting compositions of the invention are used, including mining, quarrying and construction industries.

Claims (18)

1. An explosive composition comprising an aqueous emulsion comprising:

the components of the oxidant are mixed and stirred,

an emulsifier-containing hydrocarbon fuel component, and

fuel-based waste, in the form of solid particles without rough surfaces and sharp edges, is insufficient to promote the emulsion crystallization.

2. The composition of claim 1, wherein the waste material alone does not provide sensitization of the emulsion to allow explosion; the detonation is allowed by later addition of a sensitizing component to the composition.

3. The composition of claim 2, wherein the sensitizing component is a density reducing agent.

4. The composition of claim 1, wherein the oxidizer is selected from one or more of ammonium nitrate, sodium nitrate, or calcium nitrate.

5. The composition of claim 4, wherein the oxidizer is ammonium nitrate.

6. The composition of claim 3, wherein the density-reducing agent is a salt of an alkali metal nitrite and an acid that, when combined, produces nitrogen gas.

7. The composition of claim 1, wherein the composition of the fuel-based waste material is selected from the group consisting of: plastics, rubber, paper, cardboard, wax materials and miscellaneous plastic waste.

8. The composition of claim 6, wherein the density of the composition is reduced to between 0.80 and 1.15g/cm by the addition of the density-reducing agent³In the meantime.

9. The composition of claim 1, wherein the particulate waste is in the form of pellets substantially free of rough surfaces and sharp edges.

10. The composition of claim 1, wherein the average particle size of the particulate waste is about 2-3 mm.

11. The composition of claim 1, wherein the waste material comprises 1% to 50% by weight of the total composition.

12. The composition of claim 11, wherein the waste material comprises 10% to 40% by weight of the total composition.

13. The composition of claim 1, wherein the fuel-based waste material in solid particulate form has a bar rating test (as described herein) value of 6 or greater.

14. A method of providing an explosive composition to an explosion site having one or more blastholes for containing said composition by means of a conventional Mobile Processing Unit (MPU), said apparatus comprising a truck having separate compartments adapted to contain (a) fuel oil, (b) dried ammonium nitrate prills and (c) an ammonium nitrate based emulsion, and said apparatus having means for mixing together two or more components from compartments (a), (b) and (c) and injecting the resulting mixture into a blasthole,

characterized in that said compartment (b) is adapted to contain particulate waste material, and

the density reducing agent is added to the mixture from compartments (a), (b) and (c) with an auger on the MPU before the mixture is injected into the blasthole.

15. A method according to claim 14, wherein the mixture is injected into the blasthole by means of an auger.

16. A method of blasting soft wet ground comprising injecting into one or more blastholes in the soft wet ground a sufficient amount of a composition according to any one of claims 1-12 and then detonating the composition.

17. The method of claim 16, wherein the composition is injected into the blasthole by means of a conventional mobile handling device comprising a truck having separate compartments adapted to contain (a) fuel oil, (b) dried ammonium nitrate prills, and (c) an ammonium nitrate-based emulsion, and the device having means for mixing together two or more components from compartments (a), (b), and (c) and injecting the resulting mixture into a blasthole,

characterized in that said compartment (a) is adapted to contain particulate waste material, and

the density reducing agent is added to the mixture from compartments (a), (b) and (c) with an auger on the MPU before the mixture is injected into the blasthole.

18. A method according to claim 17, wherein the mixture is injected into the blasthole by means of an auger.