AU2019365614B2

AU2019365614B2 - A sensitised, safe to manufacture and environmentally friendly explosive composition

Info

Publication number: AU2019365614B2
Application number: AU2019365614A
Authority: AU
Inventors: Miguel ARAOS
Original assignee: Etken Teknologi AB
Current assignee: Etken Teknologi AB
Priority date: 2018-10-25
Filing date: 2019-10-25
Publication date: 2022-10-27
Anticipated expiration: 2039-10-25
Also published as: WO2020085986A1; EP3870557A1; AU2019365614A1; WO2020085986A8; EP3870557A4

Abstract

An explosive composition, its manufacture process and its use comprising an oxidiser solution, with at least one water soluble fuel or at least one water insoluble fuel, with at least one pH sensitive thickener, with at least one pH modifier, with at least one sensitising material to create hot spots, optionally with at least one hydrogen peroxide stabiliser, optionally at least one surfactant to assist with the incorporation of solid sensitising material or produce homogeneous sized gas bubbles in the final gel, with at least one high-density material to Increase the density of the product so It sinks easily in water and water.

Description

A sensitised, safer to manufacture and environmentally friendly explosive composition

Field of the invention

The present invention relates to a mining explosive composition and its method of manufacture that

• Does not produce nitrate leaching in blasting operations in mines / quarries / underground or civil construction.

• Can be manufactured at room temperature, using non explosive fluids, near the point of use, so no need to transport the material on public roads.

• Sensitising materials, which alter the density of the product, are incorporated before the production of the main product, to eliminate the task of adjusting density by the operator.

• Can be manufactured near the blasthole at the mines, so no energetic material is transported in public roads.

Definitions

Sensitising material. Compressible material (with a low density, such as glass microballoons - GMB, gas bubbles - GB or expanded polystyrene - EPS) which can create hot spots, with a temperature above 500-C, after being compressed by s shock wave in an explosive. These sensitising materials have an inherently low density.

HP. Hydrogen peroxide solution

HP-based gel. A gel that contains HP (oxidiser), fuel(s) (combustible) and thickener(s)

HP-based explosive gel. A gel that contains HP (oxidiser), fuel(s) (combustible), thickener(s) and sensitising material to create hot spots in the gel.

Nitrate leaching. AN that leaches out from undetonated explosives into mine water.

Background of the invention

AN-based emulsion or watergel compositions are made using ammonium nitrate (AN) (hereinafter AN-based emulsions / watergels). These compositions can then be mixed / blended with AN prills and fuel oil (also known as ANFO). The mixing of AN-based emulsion or watergel compositions with ANFO can be conducted in any ratio, preferable (but not limited) between 70/30 to 30/70 by weight. During this step, sensitising materials (like GMB, GB or EPS) are incorporated in the AN-based emulsion or watergel / ANFO compositions. These sensitising materials produce hot spots in explosive products to make them sensitive to the initiation by a booster. Then the product is loaded into a blasthole and can be used to break rock by blasting in mines.

Generally speaking, the preparation of AN-based emulsions or watergels compositions with ANFO followed by the addition of sensitising materials the following operational disadvantages:

• AN absorbs water from the air, which causes a problem called "caking". Caking does not allow AN to flow, so the ANFO prepared makes difficult to reach the final target mixing ratio of AN-based emulsion or watergel compositions with ANFO. This situation worsens in tropical countries due to high humidity.

• Solid materials (like ANFO) are difficult to meter and operator must be competent with the field equipment to get the target emulsion or watergel compositions / ANFO blend ratio.

• The addition of chemicals to create sensitising material of the GB type is a complicated process and requires highly skilled operators. GMB or EPS can be used, as they are less dependent on the operator, but its addition into the energetic material in field operations increases the risk of unwanted event like a detonation, as the product is already sensitised.

Additional problems presented by emulsion or watergels compositions blended with ANFO are of the environmental type. The presence of AN in the compositions have the following disadvantages

• Produce NOx fumes after blasting. These fumes are harmful and there have been cases where employees of public have been taken to hospitals due to the NOx breathing. In some countries the regulators have issues regarding these NOx fumes after blasting

(https://www.dnrme.qld.gov.au/ _ data/assets/pdf_file/0010/212500/qld-guidance- note-20-mgmt-oxides-nitrogen.pdf) and incidents must be reported to the same regulators. This reporting issue consume time and resources. However, the main issue is the potential injury to people.

• Produce nitrate-leaching from undetonated explosives (Nitrogen leaching from explosives into mine water of an underground mine; Nikolay Sidenko, International Mine Water Association, https://www.imwa.info/docs/imwa 2018/IMWA2018 Sidenko 729.pdf). AN-based emulsion / watergel explosives also acknowledge this issue and work towards the elimination / minimisation (https://www.incitecpivot.com.au/sustainability/research- and-development/explosives; http://www.bme.co.za/resources/news/2016/62- tackling-nitrate-contamination-of-water-in-mines). Environmental laws in different countries impose demanding requirements to prevent leaching out. These requirements also cause a consumption of time and resources.

AN-based emulsion or watergels compositions blended with ANFO however still have some disadvantages, such as

• Manufacture in central location and then distribution to mines, using public roads.

There is evidence that transporting the materials have detonated after a fire (Explosion Accident during Mobile Production of Bulk Explosives; https://www.dsb.no/globalassets/dokumenter/rapporter/explosion-accident- during-mobile-production.pdf; Due-Hansen, Maria E., and Ove Dullum. "Review and analysis of the explosion accident in Drevja, Norway: a consequence of fire in a mobile explosives manufacturing unit (MEMU) carrying precursors for the on-site production of bulk explosives." Safety science 96 (2017): 33-40.).

Patent WO 2013013272 claims a product which is made of HP, fuel, thickeners and sensitising material which is able to work as an explosive and therefore eliminate the use of ammonium nitrate-based explosives. Furthermore, the above H P-based explosive does not produce NOx upon detonation. It does not use solid materials, like ANFO, for the manufacturing process. Overall the HP-based explosives are an improvement to common AN-based emulsion or watergel explosive compositions.

Summary of the Invention

Technical problem Notwithstanding the above advantages of the HP-based explosive gels disclosed in patent WO2013013272 over AN-based emulsion / watergel explosive compositions, these HP-based explosive gels still present some problems such as

• Operational difficulties when using the system glycerine (or any alcohol) with gum to thicken the HP to prepare the HP-based explosive gel. The glycerine/gum mixture needs continue stirring to prevent the gum settling at the bottom of the tank. This settling, if it takes place, causes loss of time as the gum needs to be re-suspended before begin the manufacture of the HP-based gel.

• Difficulties to incorporate additives (like sensitising material) into the HP-based gel.

Once the HP gel is formed, due to its viscosity and rheology, the mixing of the sensitising material (GMB, GB or EPS) is particularly difficult and therefore not homogeneously mixed throughout the HP-based explosive gel - this uneven mixed mixture could cause different velocity of detonation along the column of the HP-based explosive gel in a blasthole. The addition of sensitising materials during the process is shown in figure 4.

• Another disadvantage of the HP-based explosive gels is that when sensitising material (which have a low density) are mixed into the gel to render it sensitive, the gel density drops from 1.20 g/ml to 1.10 g/ml (and lower). At this density the HP-based explosive gel sinks slowly into water if present in the blasthole. This low rate of sinking does not displace the water properly and may entrap pockets of water that may affect the detonation of the HP-based gel explosive.

• HP is a good oxidiser but not very selective and therefore reacts with many of the rock types present in mines. These types of reaction cause a decomposition of the HP- based gel, which releases heat and it may cause an unwanted detonation of the blasthole where the gel is loaded.

Solution to the problem

This present relates to an explosive composition and its method of manufacture. The preferred objectives of the present invention is to disclose • A manufacturing system that eliminates the use of suspended gum in alcohol and therefore no settling of components from the starting phases takes place before preparing the HP-based gel.

• A simpler and better method for the incorporation and distribution of the sensitising material throughout the HP-based explosive gel.

• A system wherein the HP-based explosive gel sinks better in water.

• A method to delay or eliminate the HP-based explosive gel reactivity with rocks.

• A product that eliminates nitrate leaching

• A product that can be manufactured within a mining lease or, preferably, on the bench, near the blastholes.

According to a first aspect, the present invention provides an explosive composition to overcome or ameliorates one or more of the disadvantages of the prior art of explosives used in mining activities, or at least to provide a useful alternative. The present invention provides an explosive composition comprising an oxidiser solution containing HP, at least one water soluble fuel, at least one pH sensitive thickener, at least one sensitising material (to create hot spot) which is incorporated before the manufacture of the HP-based gel composition, optionally at least one HP stabiliser, optionally at least one surfactant to assist with the incorporation of solid sensitising material or produce homogeneous sized gas bubbles in the final gel, optionally at least one high-density material to increase the density of the product so it sinks easily in water when required.

According to a second aspect, the present invention provides a manufacture method for an explosive composition comprising an oxidiser solution containing HP, at least one water soluble fuel, at least one pH sensitive thickener, at least one sensitising material (to create hot spot) which is incorporated before the manufacture of the HP-based gel composition, optionally at least one HP stabiliser, optionally at least one surfactant to assist with the incorporation of solid sensitising material or produce homogeneous sized gas bubbles in the final gel, optionally at least one high-density material to increase the density of the product so it sinks easily in water when required.

According to a third aspect, the present invention provides a method of use for an explosive composition comprising an oxidiser solution containing HP, at least one water soluble fuel, at least one pH sensitive thickener, at least one sensitising material (to create hot spot) which is incorporated before the manufacture of the HP-based gel composition, optionally at least one HP stabiliser, optionally at least one surfactant to assist with the incorporation of solid sensitising material or produce homogeneous sized gas bubbles in the final gel, optionally at least one high-density material to increase the density of the product so it sinks easily in water when required. The present invention relates to explosives for use for blast rocks in mines.

Brief description of the drawings

Figs. 1-3 schematically illustrates embodiments of the present disclosure.

Fig. 4 schematically illustrates addition of sensitising materials.

Fig. 5 schematically illustrates the basic manufacturing method of the present disclosure.

Fig. 6 is a plot illustrating the VOD trace for an example of the present disclosure.

Detailed description

The drawings present the variants for the manufacturing methods. Drawings shows the equipment needed to manufacture the energetic composition. The manufacturing equipment could be either fix, in a building or mobile (on an electrically or diesel-powered truck).

The manufacturing method needs at least 1 tank with a fluid with the second and third tank optionally empty or containing formulation additives, valves, optionally flowmeters, hoses, mixing reactors and pumps. Temperature, pressure and other type of sensors can also be added to tanks, pipes, mixing reactor to control the overall process.

Tank 1, 2 and 3 contain fluids 1, 2 and 3 respectively. Fluids 1, 2 and 3 can have a viscosity from 1 Pa*s to 50,000 Pa*s. The transport of the fluid 1, 2 and 3 through pipes 4a, 4b and 4c to joint fitting 5 can be conducted with suitable pumps or by gravity. Pipe 4a, 4b and 4c can be made of rigid or flexible material, compatible with fluids 1, 2 and 3. The length of pipes 4a, 4b and 4c can be between 0.3 metre to 100 metres.

Joint fitting 5 is connected to reactor 7 by a flexible or rigid pipe 6. Reactor 7 may or may not have moving parts. A static mixer, which does not have moving part, is the preferred reaction. The volumetric rate of the mixed fluid in reactor 7 could be between 1 - 1000 L/minutes. At the end of the reactor 7, a flexible or rigid pipe 8 is attached. Pipe 8 could have a length of 0.05 metres to 100 metres.

At the end of pipe 7, a device 8 to produce either a stream of fluid (which is shown in figure 1) or produce droplets (like a shower head, figure 2) is attached. A schematic is shown in figure 3. The fluid or droplets can be discharged directly into a borehole 10 (located in a mine, quarry, UG mines or tunnel construction) or a tray 10 to provide a sheet-like shape. Once discharged, the fluid shapes into an elastic solid material (hard gel) or only flowable gel.

If a shower head-type device is used, the droplets can be discharged into either a borehole (located in a mine, quarry, UG mines or tunnel construction) or into a tank 11 on a truck. Then the spherical shaped energetic material becomes at least an elastic-solid material (hard gel). These spherical energetic products are then loaded into a borehole 9 (located in a mine, quarry, UG mines or tunnel construction).

An alternative for manufacturing is to separate the hoses 4a, 4b and 4c from the reactor 7.

In this case the reactor 7 is placed on top a borehole 10 (located in a mine, quarry, UG mines or tunnel construction) and the fluids 1, 2 and 3 are pumped in the right ratios into the top part of the reactor. The fluids mode downward due to gravity and at the same time the fluids are mixed. The mixed fluids exit the reactor 6 at the bottom and start filling the borehole 9. The fluid then becomes an elastic solid material (hard gel).

The elastic-solid elastic energetic material or gel placed in the borehole can be initiated by a booster and detonator as known in the art.

The elastic-solid elastic energetic material with a sheet-like shape can be initiated by a booster and detonator as known in the art. This sheet can be used to break oversized rock on the surface of the mines or used to create shockwaves in engineering applications

The elastic-solid elastic energetic material with a spherical-like shape can be initiated by a booster and detonator as known in the art. This sheet can be used to blast rocks in mines.

The tanks must contain the following components for the different method to work out properly. Table below provides the different combination in the tanks Figure 5 presents the basic manufacturing method. Solution A is prepared with H P, a pH sensitive thickener, sensitising materials and pH adjustment of the solution below 4.0, so the solution thickens to a viscosity below 5,000 cP and keeps the sensitising material homogeneously distributed in the solution. A solution B prepared with HP, water soluble fuels, and a pH modifier to adjust the pH of the solution above 5.0. Once prepared, both solutions can be conveyed through pipes using pumps. These two solutions, conveyed by two different pipes, merge in one pipe which in turn is connected to a static mixer (reactor). The mixing of the two solutions is conducted by the static mixer, and the solution that has a pH above 5.0 thickens the pH sensitive thickener present in the solution A. The static mixer can be near the pumps of up to 100 metres (near the blastholes). The final viscosity of the product, which is now an explosive (Solution A + Solution B have been mixed) is between 20 Pa*s to 100 Pa*s or even higher.

The major improvement in this manufacturing process is that

• The pH sensitive thickener does not settle.

• the sensitiser is included in one of the starting components of the HP-based explosive gel - in this case in solution A and due to the low viscosity of this solution, the sensitising material is homogeneously distributed and locked into position when the pH is adjusted. When mixed with solution B, the viscosity of the final HP explosive gel increases to 20 Pa*s - 100 Pa*s. In this way, the sensitising material is not added once the HP-gel is formed as it is currently done by the current technology for mining explosive (see figure 1). Furthermore, the solution where the solution where the sensitising material has been incorporated is still liquid or with a low viscosity, so it can be handled with pumps. No solid handling material equipment is required in this step.

The manufacturing system for the HP-based explosive gel can be placed on a platform which can be mobile or static. If mobile, the HP-explosive gel can be made next to the blasthole. If in a platform, the product can be made at a facility at the mine. Whichever option is selected, no energetic product is transported in public roads.

The present invention combines products that by itself are not explosives. However once mixed, the non-explosive components make an explosive suitable for mines. The HP-based explosive gel consists of the following components:

Oxidiser component. This component reacts with the fuel phase to release energy. In this case the oxidiser is hydrogen peroxide (see WO2013013272).

Fuel component. Fuel is an essential component of explosives as they react with the oxidising agent and release energy. Fuels that can be used are either soluble or insoluble in HP solution. Soluble fuels are sugar, urea, alcohol (ethanol, propylene glycol, glycerine, for example see patent US 3,367,805), organic acids (citric, oxalic, tartaric, etc.).

Thickening agents. Thickening agents are compounds able to hold the oxidiser, fuel and any other component (such as sensitising materials) together in the final gel product. The final gel formed from these thickener agents can have a flowable gel or semi rigid / hard gel structure. In the case of this invention, a pH sensitive thickener has been selected. These thickeners are pH dependent - they work in a pH range of 4 - 10. Example of these pH-sensitive thickening agents are carbomers / carbopol like the one described in document "Rheology Modification of Hydrogen Peroxide-Based Applications Using Cross-Linked Polyacrylic Acid Polymers" (Julie Schmucker-Castner and Dilip Desai; Presented at the Society of Cosmetic Chemists Conference, December 1997, New York) or US patent 4,288,048, or carbomer manufactured under the Flogel trade mark (manufactured by SNF). They need a pH modifier to swell and produce the thickening effect. These pH sensitive thickeners are based on polycrylica acids. Examples of pH modifiers to thicken carbomers / polyacrylic acids are triethanolamine, sodium or potassium hydroxide, or sodium bicarbonate or any other alkaline chemical, trimethamine, aminoethyl propanol, tetrahydroxypropyl ethylene diamine (See US Patent 6,555,020). The use of these pH sensitive thickeners is an improvement to the previous art (see patent WO Patent WO2013013272) because the pH sensitive thickener does not settle at the bottom if not stirred (like in the case of glycerine and gums). This pH sensitive thickener also allows to maintain a solution with a low viscosity, just enough to lock in the sensitising material.

Sensitising materials. These types of materials have low densities and can be compressed by the passing of a shock wave. When being compressed, the temperature inside of these materials increase above 500-C is a timeframe of less than 0.1 microseconds. This compression creates hot spots in the explosives composition which in turn decomposes it and creates a detonation shock. Depending on the amount of these sensitising material, the HP- based explosive gel can change its velocity of detonation (VOD).

The addition of these sensitising materials lowers the overall density of the energetic material. Furthermore, the different densities that can be achieved by the incorporation of these sensitising materials, can alter the velocity of detonation of the HP-based explosive gel. This alteration of the VOD is important as allow to tailor the explosive to the different tasks (higher or lower VOD for different rocks, different shock wave strength for welding, etc). Sensitising materials enclose a gas. They can be gas bubbles (chemically generated, like in US patent in situ or injected into the gel, like for example US patent 6,537,399), plastic or glass microballoons (see for example US 3,294,601), expanded polystyrene (see patent 4,995,925). Other materials like rice, popcorn can be used to drop the density of the gel. Solid density modifiers (GMB, PMB, extendospheres, perlite) and chemical to produce gas bubbles are added mostly after the gel has been formed.

Stabilisers. H P decomposes with time and also react with different compounds. Stabiliser are needed to delay or eliminate any secondary reaction between HP and other components of the final gel. Pat describe these a few of these stabilisers. Therefore, this invention differentiates from the previous art due to the fact that uses stabiliser to extend the shelf life of the HP-based product. Examples of these stabilisers are H EDP (British Patent 925,373), EDTA (British Patent 1,285,151), DMTPA (US patent 4,294,575), DMTPANa, EDTMPA (US Patent 3,701,825) or derivatives of phosphonates as those described in US Patent 4,304,762, sodium metaphosphate or sodium pyrophosphate (US Patent 4,320,102), SPHA (US Patent 4,380,482), HEEDTA, EDTA, DTPA or their sodium salts (US Patent 4,477,438), NTA, GEDTA, CDTA, CaNa2EDTA, Na2EDTA, Na4EDTA, H EDTA, Na3HEDTA (US patent 6,555,020); ATMP (US patent 7,169,743). Also, PHAS (sodium poly-a-hydroxyacrylate) can be used as stabiliser (Silicate-Free Peroxide Bleaching of Mechanical Pulps: Efficiency of Polymeric Stabilizers, Hannu Hamalainen et.al)

Surfactants. These chemicals are used to control the size of the gas bubble type sensitising material (see for example EP0161821B1). They can also be used to wet some other hydrophobic sensitising voids like expanded polystyrene. Examples of these surfactants are sodium laureth sulphate, caprylyl/capryl glucoside, coco betaine, lauryl myristl amine oxide, sodium cocoyl isenthionate, cocoamide, etc. High density material. These materials are inert - do not interfere with the detonation process. They have been used to increase the density of the energetic composition, so they can easily sink into water. Patent US 4959108 claims the use of glass beads as high-density material. In the case of this invention, the difference lies in the use of solid glass beads (with a size between 10 to 5000 mm), which can be metered and flow easily when incorporating them into one of the solutions used to prepare the HP gel, of after the gel has been manufactured. Example of these glass beads are supplied by Burwell Australia and have a particle size below 45 microns.

Manufacturing method description

Preparation of Solution A and Solution B. The potential compositions of Solution A and B displayed in Table 1.

Table 1

When manufacturing the explosive composition, two non-explosive solutions are used. They are described below:

• One solution (Solution A) contains HP, a pH sensitive thickener, a sensitising material (GMB, gas bubbles or EPS) and a pH modifier to adjust the pH of the solution. Solution A is prepared by placingthe HP (between 35 - 70% w/w) in a mixing tank, continuously stirred. The pH sensitive thickener is added until fully incorporated into the HP solution. Then the sensitising material is added (GMB or EPS) or generated in situ by bubble producer instruments. Once the sensitising material is incorporated, the pH of the Solution A is adjusted to 2.5 - 4.0. In this way the pH sensitive thickener present in Solution A thickens and locks into position the homogeneously distributed sensitising material (i.e. the sensitising material does not migrate to the surface of the solution). The density of Solution A drops due to the low density of the sensitising material. This solution is not explosive. Also, high density materials like solid glass beads could be added to this solution if the final product is to be used in blastholes with water. This high density makes the density of the solution to increase.

Similar principles, where the GMB are mixed with a pre-emulsified emulsion, are used by US patent 4,737,207 or WO Patent 201106045. However, in this invention, the sensitising material is locked in a thickened solution, not emulsified. No previous art has been found regarding suspending sensitising material in thickened liquid before making an explosive composition.

• The second solution (Solution B) contains HP, a water-soluble fuel, and a pH modifier.

Solution B is prepared by placing the HP (between 35 - 70% w/w) in a mixing tank, continuously stirred, then the water-soluble fuel is added, and pH adjusted to a value above 5.0. This solution is not explosive. Alternatives to this preparation consists of adding HP stabilisers to the solution.

• Once prepared, Solution A and B are pumped separately through pipes (in a predetermined ratio, so the final oxygen balance of the final HP gel is between -10 to 10), until the solution merge in a pipe connected to the inlet of a static mixer. Then the static mixer mixes (eamples of these devices are disclosed in US Patent 4,948,440) both solutions, the system thickens due to the high pH of Solution B and the sensitising material is locked into position, homogeneously distributed. The final viscosity of the HP explosive gel is above 20 Pa*s. The final density of the HP explosive is between 0.5 - 1.40 g/ml.

Combination of 1 and 2 have two important features: a. Because water soluble fuels and density modifiers are not to be in the same tank, the products in each tank are not explosives.

b. The pH sensitive thickener is not in the same tank as the pH modifier, so they remain as low viscosity liquid until mixed

Provided the above conditions are met, any combination of components in the tanks are possible.

The manufacturing method needs valves, flowmeters and pumps. Temperature, pressure and other type of sensors can also be added to tanks, pipes, mixing reactor to control the overall process.

Examples

Example 1

Solution A was a suspension of 12.6 grams of Carbomer 980 (Supplied by New Directions Australia Pty Ltd) in 814 grams of HP 50% w/w (from Solvay Australia). Carbomer 980 was added slowly to HP 50% w/w while stirring. Solution B was prepared by dissolving 338.3 grams of white sugar in 837.8 grams of HP 50% w/w. The pH of this solution was adjusted with 3.5 grams of TEA (Supplied by New Directions Australia Pty Ltd). The final pH of Solution B was 6.0. Solution B was then added onto Solution A and a thick gel was formed. Then 55.7 grams of QCel 5020 (Supplied by Barnes Australia Pty Ltd) were mixed into the gel. The final density of the gel was 1.07 g/ml. The gel was loaded into a PVC pipe of 1 metre in length. The sample was detonated using a 50-gram booster (from Beston Australia). The explosive detonated with a velocity of detonation of 5202 m/s and it was measured using an instrument made by Shottrack Australia Pty Ltd. The VOD trace for the charge is displayed in the plot shown in figure 6. This example demonstrated that the use of carbomer in the formulation is suitable as the product detonated.

Example 2

Solution A was prepared by adding 0.50 grams of Ultrez 10 to 199.9 grams of HP 50% w/w. Solid glass beads with a size of 45 microns were added to Solution A. TEA was added to Solution A until thickening took place. Glass beads from Burwell Australia, with a density of were suspended and locked into place. This test demonstrated that glass beads, and for extension, GM B, gas bubbles, EPS, etc, can be homogeneously distributed into a thickened HP solution.

Example 3

Solution A was prepared in a plastic tank by dissolving 64 grams of Carbomer in 3964 grams of HP 49.5% w/w (supplied by Swed Handling Sweden). Then 159 grams of K-15 GMB from 3M were added. This solution has a pH of 1.20. 0.9 grams of triethanolamine (TEA, supplied by Swed Handling Sweden) were added and the solution thickened to lock in place the homogeneously distributed GMB. The solution reached a pH of 3.6 - 3.8. The density of Solution A was 0.90 g/ml.

Solution B was prepared by dissolving in a plastic tank 1352 grams of sugar in 2643 grams of HP 49.5% w/w. Sugar was sourced from the local food store. Then 23 grams of TEA were added to increase the pH to around 6.0. The density of this solution was 1.31 g/ml. Tanks with the prepared solutions A and B were connected to two different magnetic gear pumps. Solutions A and B were joined by a "T" fitting before passing through the static mixer. Once Solution A and B were mixed, the final HP gel had a density of 1.04 g/ml. Five charges in plastic tubes of 51 mm were prepared and fired using a detonator surrounded by 8 short strings of detonating cord 3 g/m. All samples prepared by this method detonated.

Claims

1. An explosive composition comprising an oxidiser solution, with at least one water soluble fuel or at least one water insoluble fuel, with at least one pH sensitive thickener, with at least one pH modifier, with at least one sensitising material to create hot spots, optionally with at least one hydrogen peroxide stabiliser, optionally at least one surfactant to assist with the incorporation of solid sensitising material or produce homogeneous sized gas bubbles in the final gel, with at least one high-density material to increase the density of the product so it sinks easily in water and water.

2. An explosive composition according to claim 1 wherein the oxidiser is hydrogen peroxide in a concentration between 30% to 75% w/w.

3. An explosive composition according to claim 1 and any of the previous claims wherein the water-soluble fuel is sugar, glycerine, propylene glycol, urea, citric acid (or any organic acid), aromatic sulphonic acid or mixture thereof, in a concentration between 1 - 25%

4. An explosive composition according to claim 1 and any of the previous claims wherein the thickener is pH sensitive, from the family of poly acrylic acid, such as Carbomer 980, Ultrez 10 or Flogel 1000FV, or any polyacrylic acid of the Carbomer / Carbopol family, in a concentration between 0.01 - 10%.

5. An explosive composition according to claim 1 and any of the previous claims wherein the pH modifier is from the amine family, like triethanolamine (TEA), sodium or potassium hydroxide (NaOH or KOH), or sodium bicarbonate (NaHC03) or any other alkaline chemical, like trimethamine, aminoethyl propanol, tetrahydroxypropyl ethylene diamine, or mixtures thereof.

6. An explosive composition according to claim 1 and any of the previous claims wherein the sensitising material is hollow glass spheres (GMB), expanded polystyrene (EPS) or gas bubbles, or mixture thereof, in a concentration between 0.01 - 10% w/w.

7. An explosive composition according to claim 1 and any of the previous claims wherein the hydrogen peroxide stabiliser is HEDP, DMTPA, HEDP, DMTPA, DMTPANa, EDTMPA or derivatives of phosphonates such as sodium metaphosphate or sodium pyrophosphate, SPHA, HEEDTA, NTA, GEDTA, CDTA, CaNa2EDTA, Na2EDTA, Na4EDTA, HEDTA, Na3HEDTA, ATMP, PHAS or mixtures thereof in a concentration between 0.01 - 10%.

8. An explosive composition according to claim 1 and any of the previous claims wherein the surfactant is compatible with the thickening system, for example sodium laureth sulphate, caprylyl/capryl glucoside, coco betaine, lauryl myristl amine oxide, sodium cocoyl isenthionate, cocoamide, in a concentration between 0.01 - 10%.

9. An explosive composition according to claim 1 and any of the previous claims wherein the high-density material is solid glass beads with a size between 10 to 2000 microns of diameter and in a concentration between 0.01 to 30% w/w.

10. An explosive composition according to claim 1 and any of the previous claims wherein the oxygen balance is between -10 to +10.

11. A method to prepare an explosive composition according to claim 1 and any of the previous claims, wherein a solution is prepared with hydrogen peroxide, pH sensitive thickener, a pH modifier to adjust the pH to values between 2.5 - 4.0.

12. A method to prepare an explosive composition according to claim 1 and any of the previous claims, wherein a solution is prepared with hydrogen peroxide, water soluble fuel, and a pH modifier to adjust the pH to values above 5.0.

13. A method to prepare an explosive composition according to claim 11 and claim 12, wherein those two solutions are pumped though pipes and merged together using a "T" or Ύ" fitting before going through a static mixer, making an explosive gel.

14. A method to prepare an explosive composition according to claim 13 and any of the previous claims, wherein the explosive composition can be manufactured near the point of use, avoiding transport of an explosive in public roads.

15. A method to prepare an explosive composition according to claim 14 that can be manufactured within a mine site by an assembly on a truck, wherein said truck is operated by a person in inside the truck's cabin, or teleoperate the truck from another location or the truck is automated and does not need a person to operate the truck.

16. A method to prepare an explosive composition according to claim 15 that can be used as explosive in mining, construction or quarry blasting.

17. A method to prepare an explosive composition according to claim 16 and any of the previous claims where in the composition can be used to avoid nitrate leaching.