Emulsion explosives with nanoparticles

Abstract

A fuel composition for producing an emulsion explosive composition comprises a mixture of a liquid fuel and an emulsifying agent, wherein the emulsifying agent comprises nanoparticles in a weight % that is from about 0.05% to about 2% of the weight of the fuel composition.

Description

[0001] EMULSION EXPLOSIVES

[0002] FIELD OF THE INVENTION

[0003] THIS INVENTION relates to emulsion explosives. The invention provides a fuel composition for producing an emulsion explosive composition, and extends to an emulsion explosive composition comprising the fuel composition. The invention further provides a method of producing an emulsion explosive fuel composition. The invention also provides a method of producing an emulsion explosive composition comprising the fuel composition. Further, the invention provides use of nanoparticles in producing an emulsion explosive fuel composition. Still further, the invention provides use of an emulsion explosive fuel composition comprising nanoparticles in producing an emulsion explosive composition. The invention also provides a method of blasting a body of earth.

[0004] BACKGROUND TO THE INVENTION

[0005] EMULSION EXPLOSIVE COMPOSITIONS generally comprise an oxidizer phase and a fuel phase, with one of these phases being dispersed in the other to form an emulsion explosive composition. Typically, emulsion explosive compositions are in the form of water-in-oil emulsions, and comprise a continuous fuel (oil) phase in which a discontinuous aqueous oxidizer (water) phase is dispersed. It is to these types of emulsion explosives that the present invention is primarily directed.

[0006] In order to stimulate emulsification of the oxidizer phase in the fuel phase and also to stabilize the resulting emulsion, an emulsifying agent in the form of a chemical surfactant is usually used.

[0007] In emulsion explosive compositions, a high degree of stability and robustness is required, in that an emulsion explosive composition must not be susceptible readily to separate into its oxidizer and fuel phases. Such explosive compositions must also not have physical properties which tend to change with changes in environmental conditions to which the compositions may be exposed. Emulsion explosive compositions employed in the mining industry, for example, are subjected to significant changes in environmental conditions, including acidity (pH), temperature, pressure, etc.

[0008] Of further, and most important from the perspective of the present invention, concern is that chemical surfactants contribute significantly toward the costs of producing emulsion explosive compositions. In the Applicant’s experience chemical surfactants are, in fact, the most expensive part of an emulsion explosive composition and could contribute up to 40% of the total cost, if not more.

[0009] The present invention therefore seeks to address the abovementioned difficulties associated with the use of chemical surfactants as emulsification agents in emulsion explosive compositions.

[0010] SUMMARY OF THE INVENTION

[0011] IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION is provided a fuel composition for producing an emulsion explosive composition, the fuel composition comprising a mixture of a liquid fuel; and an emulsifying agent, wherein the emulsifying agent comprises nanoparticles in a weight % that is from about 0.05% to about 2% of the weight of the fuel composition.

[0012] In other words, for example, of a fuel composition having a weight of 100g, from about 0.05g to about 2g would be nanoparticles, providing or provided by the emulsifying agent, with the difference being liquid fuel and, in some embodiments of the invention as described below, chemical surfactant.

[0013] As used herein, the term ‘about’ refers to a value or range that is approximate in the sense that provision is made for variations that can occur without materially affecting the function or outcome of the invention. Some such variations may typically occur in measurement, handling, or manufacturing. Unless otherwise indicated, ‘about’ therefore encompasses values within standard measurement, handling, or manufacturing errors or variations of the stated value, including incidental variations that do not materially affect the function or outcome of the invention.

[0014] Nanoparticles typically include particles of matter having at least one dimension in the nanometre range, typically less than 1000 nanometres (1 pm), and more preferably less than 100 nanometres. The term encompasses individual particles, aggregates or agglomerates thereof, and includes particles of spherical, rod-like, plate-like, tubular, irregular or other morphology. Unless otherwise indicated, particle size is defined by the longest characteristic dimension, as determined by standard measurement techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), atomic force microscopy (AFM), or equivalent methods.

[0015] In being provided for producing an emulsion explosive composition, the fuel composition may, in an embodiment of the invention, be a fuel composition of an emulsion explosive composition, i.e. a fuel composition comprised by an emulsion explosive composition.

[0016] In an embodiment of the invention, the fuel composition may however, alternatively, be a standalone fuel composition, for manufacturing an emulsion explosive composition as herein described.

[0017] The emulsifying agent may be free of a chemical surfactant.

[0018] In an embodiment of the invention, as also noted later on, the emulsifying agent may consist of nanoparticles, i.e. to the exclusion of other emulsifying substances e.g. chemical surfactants.

[0019] Alternatively, the emulsifying agent may comprise a chemical surfactant.

[0020] In an embodiment of the invention, as also noted later on, the emulsifying agent may consist of nanoparticles and chemical surfactant.

[0021] The liquid fuel may be free of a chemical surfactant.

[0022] Alternatively, the liquid fuel may comprise a chemical surfactant.

[0023] It will be appreciated that the invention therefore includes embodiments in which the fuel composition is free of a chemical surfactant, and embodiments in which the fuel composition comprises a chemical surfactant, whether it is present in the liquid fuel, or present in the emulsifying agent, or present in both.

[0024] A chemical surfactant is typically a synthetic or naturally derived chemical compound that, by virtue of its molecular structure containing both hydrophilic and hydrophobic moieties, reduces the interfacial tension between two immiscible phases (such as oil and water) or alters the surface properties of a gas-liquid interface. The chemical surfactant when present in emulsion at the concentration that is above critical micelle concentration forms surfactant micelles.

[0025] Chemical surfactants are typically distinguished from nanoparticles used in the present invention in that chemical surfactants are discrete amphiphilic molecules that are soluble in one of the emulsion phase (water or oil phase) that reduce interfacial tension via molecular adsorption, whereas nanoparticle surfactants are solid particles that are dispersed in the one of the emulsion’s phases and that stabilize interfaces through physical adsorption and barrier formation. Nanoparticles form a three dimensional network within the phase they are dispersed in or / and at the water / oil (gas / oil) interphase providing enhanced stabilisation.

[0026] The liquid fuel may be a liquid hydrocarbon fuel.

[0027] Preferably, the liquid hydrocarbon fuel is in the form of a fuel oil.

[0028] In the context of the invention, fuel oils typically include combustible liquid petroleum products derived from crude oil, including distillate and residual fractions thereof, as well as the gas-to- liquids (GTL) produced from natural gas through the Fischer-Tropsch process or thereof. Suitable fuel oils in the context of the present invention typically include light distillate hydrocarbons such as diesel fuel, kerosene, or light fuel oils, heavier refinery fractions such as residual fuel oils optionally blended to adjust viscosity, and refined hydrocarbon process oils such as paraffinic or naphthenic process oils (e.g., Parprol™, Escaid™, Isopar™). Suitable fuel oils are used engine oil (UEO), also referred to as waste lubricating oil or spent lubricating oil, which are petroleum-derived by-products collected after prolonged service in internal combustion engines. It is characterized by a high hydrocarbon content with residual additives, oxidation products, and trace metals. Suitable fuel oils are typically characterized by low water solubility, sufficient calorific content to sustain detonation, controlled viscosity for pumping and emulsification, and chemical inertness toward the oxidizer phase. The term encompasses both commercial petroleum-derived oils and blended or formulated hydrocarbon oils but excludes highly volatile low-viscosity fuels such as gasoline or petrol that do not meet these criteria.

[0029] The liquid fuel may be one, or a mixture of any two or more of, a commercial mining solvent, a low grade liquid fuel (such as used lubricating oil), and a higher grade liquid fuel (such as diesel).

[0030] The liquid fuel may desirably be characterised by any one or more, preferably a ll, of the following: a boiling point range of 150 °C to 500 °C (although not absolutely being limited to this range, since it would depend on feedstock composition and refining treatment); variable viscosity depending on pretreatment, but typically within the operational range of 2-350 cP at 20 °C; and density of <1 g / cm3, e.g. about 0.76-0.95 g / cm3at 20 °C.

[0031] Commercial mining solvents typically have a hydrocarbon-based or oxygenated organic solvent composition, produced and supplied at industrial scale, that is suitable for use in metallurgical or mineral-processing operations, particularly in solvent extraction or leaching processes. Such solvents typically comprise refined aliphatic, isoparaffinic, naphthenic, and / or aromatic hydrocarbons, optionally in combination with oxygenated species, and are characterised by low water solubility, controlled volatility, and chemical compatibility with metal-extractant compounds.

[0032] Commercial mining solvents marketed under established trade names are included, for example, ShellSol™ (by Shell Chemicals), Exxsol™ (by ExxonMobil Chemical), Isopar™ (by ExxonMobil Chemical), Escaid™ (by ExxonMobil Chemical), Parprol™ (by ExxonMobil Chemical / Engen Petroleum), and equivalent ranges, as are mixtures formulated as diluents or carriers for functional extractants such as hydroxyoximes, organophosphorus acids, amines, or related chelating agents employed in the recovery and purification of metals from aqueous process streams.

[0033] In an embodiment of the invention, the liquid fuel is, or includes, a commercial mining solvent such as Shellsol™ (by Shell Chemicals), Ash-H™ (by Wozil Refinery and Chemical Company), Mosspar-H™ (by Wozil Refinery and Chemical Company), Parprol 32™ (by ExxonMobil / Engen Petroleum), Parprol 20™ (by ExxonMobil / Engen Petroleum), recycled waste oil, pyrolysis oil, or non-hydrogenated, partially hydrogenated, or fully hydrogenated vegetable oil, such as sunflower oil. When low grade liquid fuel is used, it may be used in admixture with a higher grade liquid fuel, in which case the liquid fuel may comprise up to 75% or more preferably up to 90% low grade liquid fuel and the difference as higher grade fuel.

[0034] A low grade liquid fuel is typically a combustible hydrocarbon liquid composition having a lower heating value and / or higher impurity content than standard transportation or premium-grade fuels. Such fuels typically comprise refinery residues, heavy distillate fractions, off-specification petroleum products, used lubricating oils, or blends thereof, and are characterised by higher viscosity, higher sulphur or ash content, and reduced volatility relative to gasoline, automotive diesel, or kerosene. The term encompasses residual fuel oils (e.g., heavy fuel oil, bunker oil), industrial furnace oils, re-refined waste oils, used oils, and analogous compositions that are combustible but do not necessarily meeting the specification requirements of premium liquid fuels.

[0035] Higher grade liquid fuels would typically comprise combustible liquid hydrocarbons of composition that meets the quality, purity, and performance standards of refined transportation or industrial fuels, and which is characterised by a relatively high calorific value, low levels of ash, sulphur, metals, or other contaminants, and controlled volatility suitable for efficient combustion. Such fuels may include premium petroleum-derived fuels such as kerosene, automotive diesel, jet fuel, and liquefied petroleum gas, as well as bio-derived or synthetic fuels of comparable specification, and is distinguished from lower grade fuels such as residual fuel oils, heavy furnace oils, used oils, and off-specification refinery by-products.

[0036] The liquid fuel may comprise a chemical surfactant, as has also been indicated above. This means that a chemical surfactant may be added to the liquid fuel in producing the fuel composition or that chemical surfactant may have been pre-mixed with the liquid fuel.

[0037] One desirable chemical surfactant to use, when one is used, is a PIBSA (polyisobutylene succinic anhydride) surfactant, or any of the other chemical surfactants herein described.

[0038] Typically, from about 85% to about 97% by weight of the fuel composition may comprise the liquid fuel. In an embodiment of the invention, the difference, i.e. from about 15% to about 3% by weight, therefore, comprises the emulsifying agent. When a chemical surfactant is present, as herein described, these percentages, of the liquid fuel and the emulsifying agent respectively, would include the chemical surfactant comprised by either, or both.

[0039] In an embodiment of the invention, the fuel composition consists of the liquid fuel and the emulsifying agent.

[0040] In an embodiment of the invention, the liquid fuel consists of liquid fuel.

[0041] In an embodiment of the invention, the liquid fuel consists of liquid fuel and chemical surfactant.

[0042] In an embodiment of the invention, the emulsifying agent consists of nanoparticles.

[0043] In an embodiment of the invention, the emulsifying agent consists of nanoparticles and chemical surfactant.

[0044] The nanoparticles may in an embodiment of the invention be nanoparticles having a hydrophobicity (functional performance) characterized by a carbon content (%C) ~ 0.79-4.0% by weight, or / and a water / toluene contact angle of 14 to 75, or / and a hydrophobicity index (HI) from 0.60 to >3. The nanoparticles may therefore be characterised by any one or more or all of these properties.

[0045] By “hydrophobicity” is meant that, instead of being purely water-loving or purely oil-loving (or water-repelling), surfaces of the nanoparticles may have been chemically modified, e.g. by attaching / grafting hydrocarbon-based molecules or coating with surfactants, so that they can be dispersed with both in aqueous and organic media.

[0046] This “hydrophobicity” improves their stability and functionality in mixed-phase systems, such as in the emulsion explosive composition of the invention.

[0047] For example, the nanoparticles may be nanoparticles that have been treated with silinating agents, such as organosilanes, or other surface active agents to modify their interaction with organic and aqueous phases respectively. Preferably, the nanoparticles may be selected from one or a combination of two or more of ceramic oxides, inorganic oxides, silicates, carbon-based nanoparticles, organic nanoparticles, and lipid nanoparticles.

[0048] The nanoparticles may, in particular, be selected from, but are not necessarily limited to, one or a combination of two or more of alumina; fat crystals; magnesium oxide; magnesium trisilicate; titanium dioxide; carbon; carbon nano tubes; and silica.

[0049] In the case of titanium dioxide, silica, and carbon nanotubes, the titanium dioxide, silica, and carbon nano tubes may be coated / grafted.

[0050] Preferably, the nanoparticles may comprise silica, more preferably fumed silica.

[0051] As mentioned above, the nanoparticles may be treated nanoparticles, having been treated to adjust or alter their hydrophobicity or hydrophilicity.

[0052] Typically, the nanoparticles may have been treated by chemically or physically hydrophobizing (i.e. increasing the hydrophobicity) or hydrophilizing (i.e. increasing the hydrophilicity) the nanoparticles.

[0053] Such treatment may have been, for example, by coating or grafting the nanoparticles with any suitable surface activating substance capable of altering or adjusting the hydrophobicity or hydrophilicity of the nanoparticles, to provide nanoparticles of intermediate hydrophobicity. In the case of fumed silica, for example, treatment of the nanoparticles may have included treating, e.g. coating or grafting, the fumed silica with one or a combination of any of the following substances: octa methylcyclotetrasiloxane; hexadecylsilane; methacrylsilane; dimethydichlorosilane; hexamethyldisilazane; polyd i methylsiloxa ne; silicone oil; aminosilane; and any other suitable surface activating substances capable of altering or adjusting the hydrophobicity or hydrophilicity of the silica.

[0054] Alternatively, the treated nanoparticles may be commercially available pretreated nanoparticles.

[0055] When such commercially available treated nanoparticles comprise fumed silica, the fumed silica may be selected from the following commercially available treated fumed silica nanoparticles, which may be obtained from EVONIK Industries in Germany:

[0056] Aerosil’ R104 (pretreated with octamethylcyclotetrasiloxane);

[0057] Aerosil’ R816 (pretreated with hexadecylsilane);

[0058] Aerosil’ R711 (pretreated with methacrylsilane);

[0059] Aerosil’ R974 (pretreated with dimethydichlorosilane);

[0060] Aerosil’ R812 (pretreated with hexamethyldisilazane);

[0061] Aerosil’ RY200 (pretreated with silicone oil); and

[0062] Aerosil’ RNA200Y (pretreated with silicone oil and aminosilane).

[0063] It is envisaged that the following treated nanoparticles, obtainable from Chemiphos S.A. (Pty) Ltd, may also be employed

[0064] CAB-o-silTS610 (pretreated with dimethydichlorosilane);

[0065] CAB-o-silTS530 (pretreated with hexamethyldisilazane);

[0066] CAB-o-silTS720 (pretreated with polydimethylsiloxane);

[0067] CAB-o-silTS710 (pretreated with polydimethylsiloxane); CAB-o-sil M-5 (un-treated);

[0068] CAB-o-sil H-5 (un-treated);

[0069] CAB-o-sil LM-150 (un-treated); and

[0070] CAB-o-sil EH-5 (un-treated).

[0071] It is envisaged that the following treated nanoparticles, obtainable from HUBEI HUIFU NANOMATERIAL CO, LTD. may also be employed

[0072] HB-612 (pretreated with Hexamethyldisilazane)

[0073] HB-615 (pretreated with Hexamethyldisilazane)

[0074] HB-620 (pretreated with Hexamethyldisilazane)

[0075] HB-630 (pretreated with Hexamethyldisilazane)

[0076] HB-132 (pretreated with Hexamethyldisilazane)

[0077] HB-139 (pretreated with Polydimethylsiloxane)

[0078] HB-151 (pretreated with Dimethyldichlorosilane)

[0079] HB-152 (pretreated with Dimethyldichlorosilane)

[0080] HB-202N (pretreated with Special Silane)

[0081] HB-701 (pretreated with Special Selane)

[0082] HL-90 (untreated)

[0083] HL-150 (untreated)

[0084] HL-200 (untreated)

[0085] HL-260 (untreated)

[0086] HL-300 (untreated)

[0087] HL-380 (untreated)

[0088] HL-450 (untreated)

[0089] Another possibility is to use CAB-o-sil TS610 or CAB-o-sil TS720, also from the abovementioned supplier (Chemiphos S.A. (Pty) Ltd) (also, alternatively, Cabot Corporation).

[0090] Warrenchem also supplies suitable AEROSIL’ R202 and R208, which are also suitable nanoparticles.

[0091] Further options include those identified in table 1 :

[0092] Table 1 : Commercially available nanoparticles by manufacturer, type, and manufacturer reference

[0093] In an embodiment of the invention, as noted hereinbefore, the emulsifying agent may include a chemical surfactant. In addition, or alternatively, a chemical surfactant may be included in the liquid fuel.

[0094] Conventionally, a chemical surfactant, whether comprised by the emulsifying agent or comprised by the liquid fuel, or by both, is used in a weight that is from about 5% to about 25% of the weight of the fuel composition.

[0095] In the present case, however, the chemical surfactant, when present, may be present in a weight that is up to 75% less than the conventional weight.

[0096] In one case, the chemical surfactant may therefore be present in the fuel composition a weight % that is less than 10% of the weight of the fuel composition, even as low as 2.5% of the weight of the fuel composition, i.e. between 10% by weight to 2.5% by weight of the fuel composition, or even lower e.g. 1 .5% to 2.5% of the weight of the fuel composition.

[0097] As also noted before, suitable chemical surfactants may be Pibsa-based chemical surfactants. Such surfactants may particularly be selected from a Pibsa-amine, typically being selected from Pibsa-MEA, Pibsa-lmide, Pibsa-Urea, Pibsa-DEA, Pibsa-DEEA, and Pibsa-MMEA. More particularly, in preferred embodiments of the invention, the chemical surfactant may be selected from urea, mea, dea, and sorbitane esters.

[0098] THE INVENTION EXTENDS TO an emulsion explosive composition comprising an emulsion of a fuel composition as hereinbefore described; and an aqueous oxidizer composition.

[0099] The emulsion explosive composition may therefore comprise nanoparticles in a weight % that is from about 0.05% to about 2% of fuel composition.

[0100] In an embodiment of the invention, the emulsion explosive composition comprises nanoparticles in a weight % that is from about 0.002% to about 2% of the emulsion explosive composition.

[0101] In an embodiment of the invention, the emulsion explosive composition may be free of emulsifying agents other than that provided by the fuel composition.

[0102] The emulsion explosive composition may further comprise less than 10% chemical surfactant based on the weight of the liquid fuel.

[0103] The oxidizer composition may be emulsified, as a discontinuous phase, in the fuel composition, as a continuous phase.

[0104] The fuel composition may provide from about 3% to about 15%, by weight, of the emulsion explosive composition. Typically, the fuel composition provides from about 5.5% to about 8.0% by weight of the emulsion explosive composition.

[0105] Thus, the oxidizer composition may provide from about 97% to about 85%, more preferably from about 94.5% to about 92% by weight of the emulsion explosive composition.

[0106] The oxidizer composition will include an oxidizer dissolved in water.

[0107] The oxidizerwould typically be ammonium nitrate. The oxidizer composition may also, or alternatively, include mixed metal nitrates e.g. calcium nitrate, sodium nitrate, magnesium nitrate, as or as part of the oxidizer.

[0108] The oxidizer composition may also, or alternatively, comprise perchlorates e.g. sodium or potassium perchlorate, as or as part of the oxidizer.

[0109] The emulsion explosive composition may contain from about 85% to about 95%, by weight, typically from about 92% to about 93.5%, by weight, of the aqueous oxidizer composition.

[0110] In this regard, the emulsion explosive composition may comprise from about 60% to about 87%, by weight of the oxidizer (for example ammonium nitrate), and from about 10% to about 25%, by weight, water, while still providing for inclusion of from about 3% to about 15% of the fuel composition.

[0111] Typically, the emulsion explosive composition may comprise about 80%, by weight, of the oxidizer, and about 12%, by mass, water. This means that, typically, about 8% of the fuel composition is included.

[0112] As noted earlier, the oxidizer is preferably ammonium nitrate.

[0113] The oxidizer composition may comprise other additives, including sodium acetate, typically up to 0.2% by weight (based on the total weight of the oxidizer composition); and / or acetic acid, typically up to 0.2%, by weight (based on the total weight of the oxidizer composition); and / or thiourea, typically up to 0.1% by weight (based on the total weight of the oxidizer composition).

[0114] The emulsion explosive composition may be sensitized by admixing a sensitizer with it.

[0115] In an embodiment of the invention, such a sensitizer may, for example, be a sodium nitritecontaining solution. Thus, a sensitized emulsion explosive composition may be obtained. The emulsion explosive composition is, in such a case, sensitized by microscopic bubbles, e.g. nitrogen bubbles, that are dispersed in it, the bubbles forming as a result of a sensitization reaction. In the case of sodium nitrite as the sensitizer, the sensitizing reaction occurs through the addition of the sodium nitrite to the emulsion explosive composition and through which reaction nitrogen gas is released into the emulsion explosive composition.

[0116] In sensitizing the emulsion explosive composition, a buffer may be used to control the pH of the emulsion explosive composition, for the purpose of sensitization. For example, sodium acetate and acetic acid may be used to form a buffer solution which is then used to provide pH control for sensitization of the emulsion explosive. More particularly, the buffer solution may provide pH control for the sensitization reaction.

[0117] Thiourea typically acts as a catalyst for the above-mentioned sensitization reaction.

[0118] IN ACCORDANCE WITH ANOTHER ASPECT OF THE INVENTION is provided a method of producing a fuel composition for producing an emulsion explosive composition, the method including admixing an emulsifying agent comprising nanoparticles with a liquid fuel.

[0119] The emulsifying agent comprising nanoparticles and the liquid fuel, as well as the fuel composition, may be as hereinbefore described.

[0120] The method may also include admixing a chemical surfactant, as hereinbefore described, with the liquid fuel and / or with the nanoparticles to provide the emulsifying agent. In some embodiments, the liquid fuel and / or the emulsifying agent may comprise a chemical surfactant.

[0121] IN ACCORDANCE WITH A FURTHER ASPECT OF THE INVENTION is provided a method of producing an emulsion explosive composition, the method including forming an emulsion of a fuel composition as hereinbefore described and an aqueous oxidizer composition.

[0122] The emulsion may be an emulsion of the aqueous oxidizer composition, as a discontinuous phase, in the fuel composition, as a continuous phase.

[0123] Emulsification of the fuel composition and the aqueous oxidizer composition may include admixingthe fuel composition and the aqueous oxidizer composition. Admixing the fuel composition and aqueous oxidizer composition may be at high shear.

[0124] Alternatively, it may include stimulating dispersal of the aqueous phase in the fuel phase through the use of an ultrasonic shaker.

[0125] Preferably, emulsifyingthe aqueous oxidizer phase in the fuel phase includes mixingthe oxidizer phase and the fuel phase under high shear, using a suitable mixer, typically being selected from a homogenizer, a static mixer, a jet mixer, a stir pot, and mixers operating on pin mill technology. Alternatively, the mixer may be a Silverson™ mixer.

[0126] The emulsion explosive composition may be as hereinbefore described.

[0127] The method may therefore include admixing additional ingredients, as hereinbefore described, with the fuel composition and aqueous oxidizer composition in producing the emulsion explosive composition.

[0128] THE INVENTION FURTHER PROVIDES use of an emulsifying agent comprising nanoparticles, as hereinbefore described, in producing a fuel composition as hereinbefore described.

[0129] Such use may be to reduce or avoid the need for a chemical surfactant.

[0130] STILL FURTHER, THE INVENTION PROVIDES use of an emulsion explosive fuel composition as hereinbefore described in producing an emulsion explosive composition as hereinbefore described.

[0131] Such use may be to reduce or avoid the need for a chemical surfactant.

[0132] THE INVENTION ALSO PROVIDES a method of blasting a body of earth, the method including providing a volume of emulsion explosive composition according to the invention in a blast hole formed in a body of earth and detonating the emulsion explosive composition.

[0133] Detonating the emulsion explosive composition may be achieved by using a detonator and / or a booster. BRIEF DESCRIPTION OF THE DRAWINGS

[0134] THE INVENTION WILL NOW BE DESCRIBED IN MORE DETAIL with reference to the following examples and the accompanying drawings:

[0135] In the drawings:

[0136] FIGURE 1 (a) shows a photographic image of Sample A hereinafter described, taken after standing for two months at ambient conditions (5-10°C to 15-25°C) day / night temperature circulation) after its preparation;

[0137] FIGURES 1 (bl ) to (b3) show photographic images of Sample B hereinafter described, taken after standing for respectively two, four and six months at ambient conditions (5-10°C to 15-25°C) day / night temperature circulation) after its preparation;

[0138] FIGURE 2(a1 ) to (a3) show polarized microscopic images respectively of Samples D, E and F hereinafter described, taken after standing for one month at40°C, the samples not having been subjected to pumping; and

[0139] FIGURES 2(b1 ) to (b3) show polarized microscopic images respectively of Samples D, E and F hereinafter described, taken after standing for one month at 40°C, the samples having been re-pumped at a pressure of 2 bar through a 5mm orifice.

[0140] EXAMPLES

[0141] A first sample emulsion explosive composition, designated as Sample A and being a reference sample, was prepared.

[0142] An oxidizer composition, to serve as dispersed phase in Sample A, was prepared by mixing 17,906 kg of ammonium nitrate (AN) into 5,033 kg of water at 80°C such that the ammonium nitrate dissolves in the water. The oxidizer composition is therefore in the form of an oxidizer solution.

[0143] The oxidizer solution had a crystallization point 53°C. The pH of the oxidizer solution was tuned to 3.6 at 80°C by addition of 23 kg of sodium acetate (NaAc) and 7 kg of citric acid. Finally 46 kg of thiourea (TU) was added to, a final oxidizer solution. A fuel composition, to serve as continuous phase of Sample A, was prepared from 1440 kg of a mixture of liquid hydrocarbon fuels and PIBSA-based surfactant, and 160 kg of SMO emulsifier were added to the mixture.

[0144] The oxidizer composition was emulsified into the fuel composition. As emulsifying equipment, a stir pot mixer was used. After the stir pot mixer, the emulsion was passed through a homogenizer. In the homogenizer, the viscosity of the emulsion was tuned to 18,000 - 22,000 cP.

[0145] A second emulsion explosive composition, designated as Sample B and being a composition in accordance with the invention, was manufactured and its properties were compared against Sample A.

[0146] An oxidizer composition, to serve as dispersed phase of Sample B, was prepared in the same manner in which the oxidizer composition of Sample A was prepared.

[0147] A fuel composition, being a fuel composition in accordance with the invention, was prepared by mixing 1 ,573 kg of mixture of liquid hydrocarbon fuels including PIBSA-based surfactant, 24 kg of SMO emulsifier, and 3 kg of CAB-O-SILTS610 nanoparticles.

[0148] The oxidizer composition was emulsified into the fuel composition by using a stir pot mixer and a homogenizer in substantially the same manner as in the case of Sample A.

[0149] A further sample, designated as Sample C, was prepared. Sample C contained the same oxidizer composition as that of Samples A and B. Emulsification of the oxidizer composition in a fuel composition comprising 1 ,576 kg of a mixture of liquid hydrocarbon fuels including PIBSA- based surfactant, and 24 kg of SMO emulsifier was attempted. The formation of emulsion was not possible due to low content of emulsifier.

[0150] Improved stability was observed for Sample B in comparison to Sample A (Figure 1 (a) compared to Figures 1 (b1 ) to (b3)).

[0151] After 6 months of storage in 200 litre metal drums at ambient conditions, Sample B showed a low degree of degradation, whereas Sample A was significantly more degraded (crystallization of the dispersed phase) after 2 months of storage (Figure 1 ). There was no difference observed in the blasting properties of the emulsions, as observed after manufacturing and before degradation.

[0152] Both emulsions were sensitized with 12.5 g of 3% water solution of sodium nitrite per one kg of emulsion. This resulted in the sensitized emulsions density being 1.08±0.02 kg / l. Sensitized emulsion was loaded into 42mm inside diameter plastic pipes (PVC) of 1 m length. All pipes were fired using SASOL 15 g Pentolite Booster attached to AEL Mining Services Uni-Delay LP shock tubed non-electric detonator. The time taken for the shockwave to travel a distance of ~15cm was measured using an AECE VOD Timer (model VOD-3). The VOD was calculated based on the results of these measurements and equals 4000 ± 200 m / s.

[0153] Example 2

[0154] Water-in-oil explosive emulsion compositions were prepared from the components detailed in Table 1.

[0155] Preparation was in a Hobart mixer at 82°C. In each case, a fuel composition in accordance with the invention was prepared from those components designated by an “FC” superscript and an oxidizer composition from those components designated by an “OC” superscript.

[0156] The oxidizer compositions were then dispersed in the fuel compositions.

[0157] Table 1: Water-in-oil explosive emulsion compositions The crystallization point of the oxidizer composition was kept at 49 - 51 °C. The oxidizer composition, prior to emulsification, was adjusted to a pH of 3.55 - 3.60.

[0158] Sample G crystallized just after manufacturing while coolin down. It was therefore disregarded for further investigation. The other samples under investigation (D to F) showed similar stability of un-pumped emulsion (Figures 2(a1 ) to (a3).

[0159] Often, explosive emulsion compositions are pumped to storage tanks, charging units, blast holes, etc. Emulsion pumping stages can reach up to 7 times where emulsion subjected to internal deteriorations which affect emulsion stability. Therefore, Samples D to F were subjected to pumping.

[0160] An improvement was observed in the stability of Samples E and F when compared to Sample D (see Figures 2(b1 ) to (b3)).

[0161] Discussion

[0162] The Applicant has, unexpectedly, found thatthe inclusion of nanoparticles in a fuel composition, as hereinbefore described, allows for a stable emulsion explosive composition, also as hereinbefore described, to be produced using much lower concentrations of chemical surfactants and much higher concentrations of lower grade fuels / oils, without sacrificing explosive effectiveness and stability. This translates, at least, into a significant cost saving.

[0163] Furthermore, additional benefits that were found to be imparted upon the compositions included improved blast performance, compatibility with solid ammonium nitrate that is added to emulsion at lower grade diluent fuel, improved sleep time of emulsion explosives in a blast hole, tolerance limit to the volatile content in the fuel blend, allowing for a radical increase of used oil content in emulsion explosives, extended limits of tolerance to the solvents present in different grades of diesel, and tuning of stability in pumping.

Claims

CLAIMS1. A fuel composition for producing an emulsion explosive composition, the fuel composition comprising a mixture of a liquid fuel; and an emulsifying agent, wherein the emulsifying agent comprises nanoparticles in a weight % that is from about 0.05% to about 2% of the weight of the fuel composition.

2. The fuel composition according to claim 1 , wherein the nanoparticles are nanoparticles that have a hydrophobicity characterized by a ore or more of carbon content (%C) ~ 0.79-4.0% by weight, a water / toluene contact angle of 14 to 75, and a hydrophobicity index (HI) from 0.60 to >3.

3. The fuel composition according to claim 1 or claim 2, wherein the nanoparticles are selected from one or a combination of two or more of ceramic oxides, inorganic oxides, silicates, carbon-based nanoparticles, organic nanoparticles, and lipid nanoparticles.

4. The fuel composition according to any one of claims 1 to 3, wherein the nanoparticles are selected from one or a combination of two or more of alumina; fat crystals; magnesium oxide; magnesium trisilicate; titanium dioxide; carbon; and silica.

5. The fuel composition according to any one of claims 1 to 4, wherein the nanoparticles are of fumed silica.

6. The fuel composition according to claim 5, wherein the fumed silica is pretreated fumed silica, having been pretreated by coating or grafting with one or a combination of two or more of octa methylcyclotetrasiloxane; hexadecylsilane; methacrylsilane; dimethydichlorosilane; hexamethyldisilazane; polyd i methylsiloxa ne; silicone oil; and aminosilane.

7. The fuel composition according to any one of claims 1 to 6, wherein the liquid fuel comprises up to 75%, more preferably up to 90% of a low grade fuel and the difference as higher grade fuel.

8. The fuel composition according to any one of claims 1 to 7, which is free of a chemical surfactant.

9. The fuel composition according to any one of claims 1 to 7, which comprises a chemical surfactant.

10. The fuel composition according to claim 9, wherein the chemical surfactant is comprised by the liquid fuel.11 . The fuel composition according to claim 9 or claim 10, wherein the chemical surfactant is comprised by the emulsifying agent.

12. The fuel composition according to claim 10 or claim 11 , which comprises less than 10% chemical surfactant, more preferably between 10% and 2.5% chemical surfactant, based on the weight of the fuel composition.

13. The fuel composition according to any one of claims 1 to 12, which comprises from 85% to 97% by weight of the liquid fuel and comprises from 15% to 3% by weight of the emulsifying agent.

14. An emulsion explosive composition comprising a fuel composition according to any one of claims 1 to 13 and an aqueous oxidiser composition that is emulsified, as a discontinuous phase, in the fuel composition, as a continuous phase.

15. The emulsion explosive composition according to claim 14, which comprises nanoparticles in a weight that is from about 0.05% to about 2% of the weight of the fuel composition, optionally further comprising a chemical surfactant in a weight % that is less than 10% based on the weight of the fuel composition.

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