EP4086238B1

EP4086238B1 - Composition for forming an explosive comprising an emulsion of hydrogen peroxide and an oil type fuel

Info

Publication number: EP4086238B1
Application number: EP21172315.0A
Authority: EP
Inventors: Thomas GUSTAVSSON; Robert HÅKLAND; Stefan Nilsson
Original assignee: Hypex Bio Explosives Technology AB
Current assignee: Hypex Bio Explosives Technology AB
Priority date: 2021-05-05
Filing date: 2021-05-05
Publication date: 2024-01-03
Anticipated expiration: 2041-05-05
Also published as: WO2022233952A1; EP4086238C0; AU2022269827A1; EP4086238A1; CA3217779A1

Description

Field of invention

The present invention relates to a composition for forming an emulsion type hydrogen peroxide-based explosive which can reach steady detonation in small diameters. The invention also relates to a method of preparing such an emulsion type explosive. The composition may be used e.g. in mining, construction and similar applications for rock blasting. However, it will be appreciated that the invention is not limited to this particular field of use.

Background of the invention

The following background discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.
Civil explosives formulated as emulsions are well known and are commonly used in the mining- and civil construction blasting industry, both in bulk and cartridge form. Emulsion explosives are normally water-in-oil type dispersions consisting of a discontinuous aqueous oxidizer phase normally consisting of nitrate salts dissolved in water and a continuous fuel phase consisting of various water insoluble fuels (normally oils) and emulsifiers. The two phases are combined in a continuous or batch mixing process which normally implements pressurized high shear mixing.
In practice, all available civil explosives are based on nitrate salts where Ammonium nitrate (AN) is predominantly used. It is well known that AN is a strong oxidizer and have been used in the industry for at least 60 years in various forms.
Upon detonating nitrate based explosives, large quantities of toxic nitrogen oxide (commonly referred to as NO_x) gas is produced in the post detonation fumes. These gases are lethal to humans and must be removed before personnel may enter the blast site post blast. The gases linger for an extended amount of time which leads to downstream issues such as contamination of ecological systems and pollution. Further, nitrate residues in the blasted rock or un-detonated explosives forms nitrogen leaching which pollutes water based ecological systems and ground water. In addition, nitrated used in areas where concrete or cement products are used may cause an ammonia generating reaction. In underground tunnelling, shotcrete spray concrete is used for wall stabilization. Nitrate residues from blasting reacts with the shotcrete to form ammonia gas which is toxic and creates very hazardous working environments. These problems are well known in the mining and construction industry and are directly related to the use of ammonium nitrate. It is therefore desirable to investigate the use of alternative oxidizers which preferably should be nitrogen free. Ideally these oxidizers should exhibit good detonation performance comparable to status quo and improve on the environmental and health aspects of the explosive.
The toxic NO_x gas is predominantly an issue for underground blasting operations which are common in mining and tunnelling applications. The amount of explosive used per cubic meter rock is normally higher for these applications compared to surface blasting operations due to the confined nature of the rock. It is also commonplace that a significant amount of the explosives follows non-ideal detonation behaviour where some amounts of the explosive does not detonate. The undetonated explosive combined with the nitrate polluted rock mass leads to the leaching issue as discussed above.
Hydrogen peroxide (HP) is known to be a suitable candidate and prior art research proposes various explosive compositions. HP is nitrate free and decomposes to water and oxygen in the detonation process. The oxidizing properties of HP can also be used as a replacement for traditional nitrate salt oxidizers. The idea of using HP is not new; Baker & Groves where granted a patent ( US7491279B1 ) for an HP based explosive composition and another patent ( US4942800 ) was granted to Bouillet et. al in 1990. For clarity, the use of the term HP denotes hydrogen peroxide in combination with water in various concentrations combined with known hydrogen peroxide stabilizers such as phosphonic acid.
WO 2013/013272 (Araos ) and WO 2020/243788 A1 (Kettle ) represents some of the most recent research in the field and proposes various types of water gel and a few emulsion type explosives bases on hydrogen peroxide. Both Araos and Kettle focuses on water gel technology and argues that HP based compositions could be a relevant alternative to AN based mining explosives. Kettle builds on Araos work and argues that compositions proposed by Araos suffer from too short sleep time making them difficult to use practically. Kettle proposes the addition of density stabilizers which in the context are described as HP stabilizers (i.e., various types of phosphonate based compounds). These have shown to have a stabilizing effect on the density of the HP based explosive compositions.
Araos and Kettle predominantly focus on water gel compositions and does not give any insight nor results on emulsion formulations. In addition, it should be noted that commercially available HP is normally offered dissolved in water and stabilized with phosphonates or similar compounds included in the solution as the stabilizing effect is well known. As an example, US patent 8802613B2 (Bonislawski, Lovetro) from 2007 gives an example of the stabilizing characteristics of various phosponic and other compounds when added into the HP solution. HP solutions with varying concentration of such stabilizers are readily available which implies that the HP stabilizer, i.e. phosponic acid is de-facto added to the explosive via the HP solution.
T. Halme argues in Development of nitrogen free environmentally friendly blasting explosive (Helsinki EFEE Conference Proceedings 2019, R. Holmberg et al), that HP has been the main alternative to nitrates in explosives and shows detonation and performance data from water gel HP explosives which are comparable to ANE compositions.
The properties of HP are well known. Among the known risks is the peroxide's highly reactive behaviour in combination with many catalytic or reactive materials commonly found in the mining and construction industry. HP decomposes to water and oxygen in an exothermic reaction which may lead to explosive type events. This decomposition can be aggressive and occur if impurities with catalytic behaviour enters the solution, in particular, alkaline materials, metals and some organic compounds may cause such reaction. Risk of aggressive reactivity which may lead to explosive events increases with higher concentration HP solutions (over 60%) and in particular if the HP solution is combined with organic fuels such as sugars, alcohols or similar which is the case for water gel type explosives.
The decomposition process of Hydrogen peroxide follows the formula;

2H₂O₂ → H₂O + O₂ + E
This corresponds to approximately E=2900 kJ / kg (kilo joules per kilogram). Hence, the HP decomposition is exothermal, and reactivity is therefore associated with heat generation. This heat generating reactivity is the primary reason why HP is supplied dissolved in water including stabilizers (normally phosphonic acid or tin based compounds). A decomposing HP based explosive will therefore generate heat proportional to the decomposition rate and concentration of HP inside the explosive.
Water act as a coolant and suppressor for this reaction and it is therefore, from a reactivity and stability perspective desirable to include as much water as possible in the composition. However, from a detonability and blast performance perspective, a high water content will lower the detonation heat capacity leading to inability to reach steady state detonation and/or lower detonation velocity and performance. More particularly, it might counteract reliable and stable detonation in smaller diameters, at lower densities and/or when using smaller primer initiation charges.
Additional factors that affect the decomposition reaction are stabilizers in the HP, pH, reactants, catalysts and temperature. Normally, a 50% HP solution is stabilized to maintain a pH between 1,6-2,2. Higher pH levels makes the solution more unstable and prone to decomposition. HP solutions at these pH levels are normally very stable if pure, i.e. void of contaminants, and it is normal that when stored in suitable tanks in cool temperatures, the concentration in the solution decreases with no more than 1% annually.
Controlling temperature in the HP solution is imperative to safety as a rising temperature destabilizes the peroxide. As the decomposition is exothermic, an increasing temperature could be a sign of contamination which may, in a worst-case scenario, lead to an explosive type event. Therefore, it is important to maintain storage temperature ranges for HP from -20° C to +25° C.
Reactivity makes HP based explosives previously known in the art, in particular water gel type compositions, challenging to handle, use safely, and store. It has been shown that water gels with high HP concentrations can react aggressively with alkaline, sulfuric or mineral rock types commonly found in blast holes. These reactions of fuelled water gels may reach temperatures over 150 °C at which point conventional detonators initiates. The reactive behaviour of the HP itself and such compositions is the main reason why HP based explosives have been discarded as an unsafe alternative and not used in the industry.

Summary of the invention

An object of the invention is to offer an explosive composition which significantly improves on the environmental aspects of blasting compared to nitrate based explosives and lowers or eliminates the generation of toxic NO_x gas in the post detonation fumes and does not leach any nitrates. A further object is to offer an emulsion type explosive composition which allows for good detonation, rock blasting performance and stability in smaller diameter holes commonly used in tunnelling and underground blasting operations.
The present invention relates to explosives for use in the mining and civil construction industries and similar fields. These examples should not be considered limiting as it can be expected that other fields might be applicable such as underwater blasting, agriculture or oil well blasting.
According to one aspect of the invention, there is provided a composition for forming a hydrogen peroxide based emulsion explosive as set out in appended claim 1. The composition comprises a oxidizer-phase comprising at least 35% by weight of hydrogen peroxide and at least 25% by weight of water, a fuel-phase comprising at least one primary oil type fuel with a flash point below 100 °C, and at least one secondary oil type fuel with a flash point over 150° C and at least one emulsifier, wherein the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase.
It has been found that emulsion type HP explosives exhibits a greater resistance to HP decomposition catalysts and should be considered to be less reactive compared to water gel compositions. This is due to a range of factors such as separation of fuel and oxidizer (fuel oil is immiscible in the HP solution), the oil and emulsifier coating of the HP droplets disallowing for mass transfer of HP molecules and the significantly higher viscosities possible with emulsions compared to water gels which physically hinders impurities to migrate through the explosive column.
Emulsions should further be considered significantly more stable compared to water gels from a reactivity perspective due to the encapsulation of droplets and restriction of HP mass movement. This assumes stable consistency of the composition which must stay in an emulsified state to ensure the bond between the HP and the fuel oil droplets over the storage and use period.
Work has been conducted to investigate properties of emulsion type HP based explosives which are able to reliable detonate using lower concentrations of HP (<50%) combined with improvements in stability and non-reactivity.
HP emulsion explosives have been proven to deliver blast results comparable to AN based emulsion and could offer an attractive, nitrate-free and more environmentally friendly alternative.
Due to the health hazards associated with the toxic gases in the detonation post blast fumes of nitrate based explosives, ventilation must be in place to eliminate this risk. This is particularly important in underground operations where ventilation of the gases must occur after each blast. Normally, fresh air is fed from the surface down into the tunnel structures to eject the fumes. Such ventilation takes long periods of time and lead to significant energy and production loss and is commonplace in the underground industry as all explosives are principally based on nitrate bearing compounds. It is therefore of significant interest and importance to develop explosives which minimize or eliminate the toxic nitrate footprint but simultaneously also performs equally or better in the smaller diameter holes used in underground tunnel development. HP emulsions offers a solution to this problem.
For underground tunnelling and mining work, horizontal drill holes are predominantly (but not exclusively) used. The blast hole diameters range from 34-54 mm which should be contrasted to vertical surface production blast holes which normally ranges from diameters 64 mm and upwards. Surface blast holes are normally stemmed (i.e confined) using drill chippings, rock aggregate, plastic plugs or other confiners. This is usually not done in underground due to time aspects and challenges in charging horizontal holes.
In small diameter holes (under 54 mm) commonly used in underground blasting operations, various explosives densities are formulated to control the energy output of the explosive. For instance, in perimeter blasting (where the perimeter denotes the line formed by the blast holes closest to the remaining rock forming the edge of the post blast structure) it is desirable to apply small amounts of explosive per meter of drill hole to reduce over fracturing the hanging wall remaining after blasting.
In modern blasting operations, this is achieved by placing a small diameter string of emulsion explosive at the bottom of the hole, referred to as "string loading". The string could be as thin as 16 mm in diameter. When placed in a drill hole ranging from 48-41 mm, the disconnect factor defined as the distance from the emulsion string to the drill hole edge, lowers the so called over break and fracturing of the residing rock wall. This implies that the explosive must be sensitive enough to readily detonate in diameters as low as 16 mm. While possible with AN based explosive, it has been found that reliable detonation in this diameter using HP based emulsions with high water content (over 45%) poses a challenge. One reason for this is the cooling effect of the water component in the HP emulsion.
It is desirable to balance the heat energy capacity (given by the energy availability of the fuel) with the heat energy required to condense water into steam. The specific heat energy given by the selected fuel and the ability for the fuel to quickly release this energy has a direct effect on the ability for the explosive to reach a steady state detonation as a function of initiation temperature, initiation pressure and diameter.
Surprisingly, it has been discovered that the flash point of the oil type fuels selected plays a significant role in the detonation behaviour of the HP based emulsions consisting of more than 40% water. Emulsions made only from oil fuels with flash points over approximately 100° C have been found to be significantly harder to reliably detonate in smaller diameters (less than 40 mm) where emulsions made with at least one oil having a flashpoint below 100 ° C shows excellent detonation performance behaviour in diameters under 40 mm.
The fuel-phase further comprises at least one secondary one oil type fuel with a flash point over 150° C, preferably over 200° C. Preferably the secondary oil type fuel has a molecular structure comprising 20 to 40 carbon atoms. Such high flash point oil type fuels have been shown to supress exothermic reactions of the HP to some extent and to increase viscosity of the emulsion.
The composition may further comprise a sensitizer, whereby the composition forms a sensitized emulsion explosive. Such sensitized explosive may be formulated to become detonation enabled i.e. to be ready to be detonated with traditional initiation means such as a detonator of conventional strength with or without an amplification charge (booster or primer) such as normally used in blasting.
To reach detonability and to control performance factors such as density, critical diameter and velocity of detonation the composition must be sensitized. The sensitizer may be added as a part of a pumping and charging process where the sensitizer is added and dispersed throughout the composition just before the sensitized composition is pumped into a blast hole, or, the sensitizer may be added in a process where the sensitized composition is loaded into a package to be used at a later stage.
Keeping the sensitizer and emulsion composition separate just until the moment of charging ensures that the risk of accidental initiation during production, transporting and/or handling is minimized. It further allows the operator to control the exact sensitivity or density of the explosive needed for each particular application at the point of use.
Preferably, chemical sensitization should be used where an agent is incorporated into the emulsion explosive close to the point of insertion into the drill hole. The agent generates bubbles of gas as a result of a chemical reaction. The bubbles may e.g. be generated by hydrogen peroxide decomposition. The generation of gas bubbles may further be delayed such that the gas bubbles are generated in-situ of the drill hole.
The sensitizer may comprise gas bubbles or voids which are formed inside the explosive composition as a result of a chemical reaction. Such voids are generated by a chemical decomposition process which may be delayed to achieve sensitization of the composition in-situ.
Alternatively, the sensitizer may comprise enclosed gas bubbles or voids which are mechanically added into the composition. Such voids may be formed of hollow microspheres or-balloons of e.g. glass, plastic or cellulose. These balloons/bubbles are preferably made to resist high pressures and does not allow for coalescence and prohibit bubble collapse. Advantages of using pre-made microspheres are found in situations where an exact density must be maintained over longer periods of time or when handling, transport or other operational aspects may cause gas bubbles to migrate in the explosive or when high pressures are exercised on the explosive, for example, at the bottom of deep drill holes.
The size of the gas bubbles may preferably be between 5-200 micrometres (microns) and preferably larger than the dispersed droplets of the oxidizer phase. Bubbles larger than that may otherwise join, thereby forming instabilities in the emulsion matrix.
The at least one fuel with flash points under 100° C may comprise at least one oil selected from the group consisting of mineral oils, kerosene oils, synthetic kerosene oils, naphtha oils, synthetic oils, bio oils, gasoline oils, diesel oils, synthetic diesel oils, line seed oils and neatsfoot oils.
The first oil type fuel with flash point under 100 °C may constitute between 0.1 and 10% by weight of the total composition. The amount should be balanced depending on the water content of the composition. Preferably, the low flash point oil component constitutes 0.8-4.5% by weight of the total composition.
The composition may further comprise at least one oil type fuel with a viscosity of at least 50 cP at 15 °C to increase the emulsion composition viscosity. It has been discovered that incorporating oils with a high viscosity at low temperatures (15 °C) significantly improves emulsion stability, both pre and post sensitization. Further, it has been found that such compositions as proposed herein readily detonates after 3 days in a small diameter hole (48 mm) when sensitized chemically and initiated with a 25 gram PETN booster in combination with a standard detonator resulting in acceptable blast performance.
The secondary oil type fuel may be selected from the group of mineral oils, petroleum oils, aromatic oils, bio-oils, synthetic fuel oils, diesel oils, lubrication oils, kerosene oils, naphtha oils, paraffin oils, chlorinated paraffin oils, micro benzene oils, toluene oil, polymeric oils, rapeseed oils, coconut oils silicone oils, and fish oils or mixtures thereof.
Wax components may also be comprised in the fuel-phase, in order to increase viscosity and to improve texture of the composition which could be particularly important for packaged emulsions where significant manual handling is involved.
At such embodiments, the fuel phase may further comprise at least one wax selected from the group consisting of microcrystalline wax, paraffin wax, animal wax, plant wax, montan wax, polyethylene wax and polyethylene derivative wax.
The composition may further comprise a grease lubricant in the form of a solid or semifluid dispersion of a thickener in oil. It has been found that small amounts (1-3%) of solid or semi-solid greases normally consisting of oils with thickeners can decrease the compositions tendency to react and improve stability over time. The grease may also modify the compositions texture making it potentially stickier which could be beneficial in horizontal or upward facing holes. The grease should preferably be added post emulsification to not significantly disrupt the HP droplet turnover/connection area to the droplets of the low flash point oils.
Without wishing to be bound by any theory, the term "emulsifier" or "emulgent" employed in the present invention should represent chemicals which stabilize the oxidiser phase and fuel phase dispersion by increasing the kinetic stability of the composition by bonding the droplets and which comprise at least one lipophilic moiety and at least one hydrophilic moiety.
The at least one emulsifiers may be selected from the group consisting of Polyisobutylene succinic anhydride (PIBSA), PIBSA amine derivatives, Polyisobutenyl succinic acid anhydride (PIBDIBA), PIBDIBA derivates, PIB-lactone and its amino derivatives, Sorbitan monooleate (SMO), sorbitan sesquioleate, lecithin, alkoxylates, esters combinations, fatty amines, alkyloxazolines, alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates and phosphate esters and mixtures thereof.
The at least one emulsifier may constitute of 5-30% by weight of the fuel phase and/or 0.5-5% by weight of the total composition. The most preferred content of emulsifier used is in the range from Preferably, the at least one emulsifier constitutes 0.8-2.5% by weight of the total composition.
The viscosity of the HP emulsion composition will be discussed in terms of apparent viscosity. Where used herein the term "apparent viscosity" refers to a viscosity measure using a Brookfield RVT viscometer, #7 spindle at 20 r.p.m. It is preferred that the unsensitized composition has an apparent viscosity greater than 35 000 centipoise (cP).
The apparent viscosity of the composition may e.g. be between 35 000 and 120 000 centipoise (cP). Apparent viscosity is more preferably in the range 60 000 to 120 000 cP. Preferably the explosive composition can be pumped.
To reach higher viscosities, a thickener may be added to the fuel phase prior to mixing. Thickeners, which may be crosslinked, may be selected from a large array of available compounds such as gums (Xhantan, guar or alginates) or fumes silica but preferably are selected from the group of polymeric materials such as carbopol (polyacrylic acid or polyacrylamide) with the formula (C₃H₄O₂)_n. The optional thickener component may constitute 0.1-5% of the total weight of the composition. Preferably, the thickener component may constitute 0.5-1.5% by weight of the total weight of the composition. The density of the sensitized emulsion explosive may preferably be between 0.4 - 1.25 grams / cm³. By this means the desired detonability may be achieved. Preferably, gas bubbles should be added until the sensitized emulsion explosive reaches a density between 0,4-1,25 However, this density could be higher depending on the base density of the unsensitised emulsion explosive and also based on the density of potential additives such as other oxidizers or secondary fuels.
By this means, the density is maintained or stabilised as discussed above over an extended period of time, thereby increasing sleep time compared to the explosive composition not including a density stabiliser as discussed herein. The skilled person will appreciate that a mathematical conversion may be used to convert the required weight of mechanical sensitizers for yielding a certain density, into volume. Correspondingly, the required amount of the chemical substance to be decomposed into bubbles for yielding a certain density may be converted into volume by a mathematical conversion. Furthermore, the density of the unsensitised composition shall normally always be higher than the sensitized density of the same.
The oxidizer phase may exhibit a hydrogen peroxide concentration of 35-60% by weight, preferably between 40 and 49.5% by weight.
The oxidizer-phase may comprise a secondary oxidizer such as another peroxide oxidizers such as sodium or potassium peroxide or a perchlorate such as potassium perchlorate may be added to the oxidizer phase in combination with the hydrogen peroxide and water solution. Also at such embodiments, the concentration of hydrogen peroxide should be no less than 35%.
The fuel phase may comprise oil type fuels which are water immiscible in a concentration from 2.5 to 12% by weight, preferably 4.5-9% by weight comprising at least one oil with max 18 carbon atoms in the molecular structure, preferably 10 to 18 carbon atoms in the molecular structure with a flash point under 100°C, preferably a flash point between 50-85°C.
Preferably, all components comprised in the composition are free from nitrogen or comprise very small amounts of nitrogen so that the total nitrogen content of the explosive composition is less than 1%. According to a second aspect there is provided a method of preparing an emulsion type explosive composition. The method comprises;

providing an oxidizer-phase comprising at least 35% by weight of hydrogen peroxide and at least 25% by weight of water,
providing a fuel-phase comprising at least one primary oil type fuel with a flash point below 100 °C and at least one secondary oil type fuel with a flash point over 150° C,
providing at least one emulsifier,
forming an emulsion comprising the oxidizer-phase, the fuel-phase and the emulsifier, in which emulsion the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase, and
sensitizing the emulsion by adding gas filled compressible solid micro-balloons, and/or by generating gas bubbles by means of a gassing agent and/or by adding gas bubbles to the emulsion.

Further objects and advantages of the invention will be apparent from the following detailed description of examples and from the appended claims

Detailed description of examples

According to one aspect of the invention, there is provided a composition for forming a hydrogen peroxide based emulsion explosive as set out in appended claim 1. The composition comprise a oxidizer phase comprising at least 35% by weight of hydrogen peroxide and at least 25% by weight of water, a fuel phase comprising at least one oil type fuel with a flash point below 100 °C, at least one secondary oil type fuel with a flash point over 150 °C, and an emulsifier, wherein the oxidizer-phase is discontinuously dispersed throughout the continuous fuel phase.
In practice, the composition may be formed by mixing the hydrogen peroxide water solution forming the oxidiser-phase with the fuel-phase in a mixer to thereby create an emulsion with the oxidiser phase being dispersed in the fuel phase. Preferably the emulsifier should be added to the fuel phase prior to mixing. Alternatively, the emulsifier may be added during the mixing process for forming the emulsion. Typically, the temperature of the oxidiser-phase may be kept at approx. 10-20^≈C when added to the mixer. During preparation of the fuel-phase, which may comprise mixing the low flashpoint oil-based fuel with the, the temperature of the fuel-phase may be kept at room temperature. However, when oil fuels having lower viscosity are used it may be preferable to add heat during the formation of the fuel phase. Correspondingly, the fuel phase may be supplied to the emulsification mixer at room temperature or it may be somewhat pre-heated before being supplied to the mixer.
By adding a sensitizer, the composition becomes detonation enabled and explosive though initiation with conventional means such as a detonator with or without an amplification charge (known as a primer or booster).
The sensitizer bubbles may be chemically generated though a chemical reaction caused by a gassing agent added as a part of a pumping process whereby gas bubbles are formed slowly in-situ of the composition once placed in a blast hole. An example of gassing agents which may be used is carbon powder suspended in water. Another example is a mixture of vinegar (CH₃COOH) and bicarbonate solved in water. When carbon powder suspended in water is used, the suspension will react with the hydrogen peroxide to form oxygen bubbles which act as hot spots in the composition. When vinegar and bicarbonate is used, these two substances react with each other to form hot carbon dioxide bubbles acting as hot spots.
In another embodiment, a sensitizer comprising enclosed gas bubbles in the form of hollow microspheres formed of e.g. glass, ceramic, plastic or cellulose are added mechanically and mixed into the composition making the composition sensitized and thereby detonation enabled immediately. It will be appreciated that the composition of the invention can be used for many purposes, but in particular to break and move rock in mining operations.

According to different embodiments of the composition it comprises the types of functional components listed in Table 1; wherein the amount of secondary oil fuels with a flash point over 150 °C is more than 0% by weight;

Table 1: Typical types of functional components and ratios exemplifying compositions

Type of functional component	Ratios in % by weight of the total composition
HP (primary oxidizer)	From 35 to 60
Water	From 25 to 55
Primary oil fuels with flash point under 100°C	From 0.1 to 10
Secondary oil fuels with flash point over 150°C	From 0 to 5
Non-oil secondary fuels	From 0 to 10
Secondary oxidizers	From 0 to 30
Emulsifiers	From 0.8 to 5
Additives	From 0 to 5

Such compositions may have the properties listed in Table 2:

Table 2: Properties of the exemplifying compositions

Properties	Value
Oxygen balance	From -10 to +5
Un-sensitized density	From 0.8 to 1.8
Sensitized density	From 0.4 to 1.25
Viscosity	From 35 000 to 120 000 cP
Velocity of detonation	2200 - 5500 m/s

Exemplifying typical substances for each type of functional component are listed in Table 3:

Table 3: Exemplifying substances comprised in the compositions

Function	Component
Oxidizers(s)	At least 35% Hydrogen peroxide by weight, optionally potassium peroxide/and, or sodium peroxide/ and, or perchlorate salts/and, or chlorate salts.
Fuel(s)	Mineral oils, petroleum oils, aromatic oils, bio-oils, synthetic fuel oils, diesel oils, lubrication oils, kerosene oils, naphtha oils, paraffin oils, lubrication oils, chlorinated paraffin oils, micro benzene oils, toluene oil, polymeric oils, rapeseed oils, coconut oils and fish oils, metal powders, sugars, glycerol or alcohols.
Emulsifiers	Emulsifiers containing lipophilic and hydrophilic moieties (Polyisobutylene succinic anhydride (PIBSA), PIBSA amine derivatives, PIB-lactone and its amino derivatives, Sorbitan monooleate (SMO), sorbitan sesquioleate, lecithin, alkoxylates, esters combinations, fatty amines, alkyloxazolines, alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates, phosphate esters) able to bond the HP solution.
Additives	pH adjusters, thickeners, rheology modifiers, HP stabilizers (phosphonic acid or tin based compounds), lubricant greases
Sensitizer	Gas filled voids or bubbles either chemically generated (delayed or instant) and/or gas entrapped compressible materials.

Examples

The present invention can be used for a variety of forms of emulsion type explosive compositions provided of course that the principles of the invention as described herein are observed. The invention is further illustrated with reference to the following examples.

Example 1

Table 4: Composition rations used in example 1

Component	Function	Ratio (weight %)	Comment
Hydrogen peroxide (50%)	Oxidizer Discontinuous phase	92.6	50% HP solution
Synthetic paraffin oil	Fuel Continuous phase	2.7%	Flash point over 200° C
Synthetic kerosene	Fuel Continuous phase	2%	Flash point 70° C
PIBSA	Emulsifier/Fuel Continuous phase	1.3%
SMO	Emulsifier/Surfactant Continuous phase	1.4%

A hydrogen peroxide explosive composition was prepared according to Table 4;
The continuous phase was prepared separately and heated to approximately 50° C before adding the discontinuous oxidizer phase. Oxidizer phase was added slowly during high shear mixing ensuring emulsification. The formulation resulted in a thick emulsion with an apparent viscosity of approx. 85 000 cP and a pH level of 3.9. Cup density was measured to 1.15 g/cm³.
1.2% of a chemical gassing agent comprising a carbon powder suspended in water with a thickener was added and the density changed to 0.86 g/cm³. The composition was sensitized within approx. 40 minutes and the composition was left to sleep for approx. 5 hours. Thereafter, 3 samples with 1 kg each of the sensitized emulsion was placed in a plastic sleeve with an inner diameter of 38 mm and initiated unconfined with an 8d standard detonator. Velocity of detonation was done using the MREL microtrap system with a 1meter copper probe. VOD values was where measured to be over 4000 meters per second.

Comparative Example 2

A hydrogen peroxide explosive composition was prepared similar to the one illustrated in Table 4, however without the low flash point component (Synthetic Kerosene). The composition is presented in Table 5 below;

Table 5: Composition ratios used in example 2.

Component	Function	Ratio (weight %)	Comment
Hydrogen peroxide (50%)	Oxidizer Discontinuous phase	92.6	50% HP solution
Synthetic paraffin oil	Fuel Continuous phase	4.7%	Flash point over 200° C
PIBSA	Emulsifier/Fuel Continuous phase	1.3%
SMO	Surfactant Continuous phase	1.4%

The continuous phase was prepared separately and heated to approximately 50° C before adding the discontinuous oxidizer phase. Oxidizer phase was added slowly during high shear mixing ensuring emulsification. The formulation resulted in a thick emulsion with a higher apparent viscosity compared to example 1 of approx. 100 000 cP and a pH level of 4.1. Cup density was measured to 1.16 g/cm³.
1.2% of a same chemical sensitizer as example 1 was added and the density changed to 0.89 g/cm³. The composition was left to sleep for approx. 5 hours and thereafter, 3 samples with 1 Kg each of the gassed emulsion was placed in a plastic sleeve with inner diameter of 38 mm and initiated unconfined with an 8d standard detonator. Velocity of detonation was done using the MREL microtrap system with a 1-meter copper probe. None of the samples successfully detonated.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms within the scope of the appended claims. In particular features of any one of the various described examples may be provided in any combination in any of the other described examples.

Claims

A composition for forming a hydrogen peroxide based emulsion explosive which composition comprises;
- an oxidizer-phase comprising at least 35% by weight of hydrogen peroxide and at least 25% by weight of water,

- a fuel-phase comprising at least one primary oil type fuel with a flash point below 100 °C and at least one secondary oil type fuel with a flash point over 150° C, and

- at least one emulsifier, wherein
the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase.
A composition according to claim 1, further comprising a sensitizer, whereby the composition forms a sensitized emulsion explosive.
A composition according to claim 2, further comprising a gassing agent which is arranged to form the sensitizer in the form of gas bubbles through a chemical reaction.
A composition according to claim 2, wherein the sensitizer comprises mechanically added enclosed hollow microspheres or -balloons.
A composition according to any of claims 1-4 wherein the at least one primary oil type fuel comprises at least one oil selected from the group consisting of mineral oils, kerosene oils, synthetic kerosene oils, naphtha oils, synthetic oils, bio oils, gasoline oils, diesel oils, synthetic diesel oils, line seed oils and neatsfoot oils.
A composition according to any of claims 1-5 wherein the first oil type fuel with flash point under 100 °C constitutes between 0.1 to 10% by weight of the composition.
A composition to any of claims 1-6, wherein the fuel phase further comprises at least one oil type fuel with a viscosity of at least 50 cP at 15 °C to increase the emulsion composition viscosity.
A composition according to any of claims 1-7, wherein the secondary oil type fuel is selected from the group of mineral oils, petroleum oils, aromatic oils, bio-oils, synthetic fuel oils, diesel oils, lubrication oils, kerosene oils, naphtha oils, paraffin oils, lubrication oils, chlorinated paraffin oils, micro benzene oils, toluene oil, polymeric oils, rapeseed oils, coconut oils, silicone oils and fish oils.
A composition according to any of claims 1-8, wherein the fuel-phase further comprises at least one wax selected from the group consisting of microcrystalline wax, paraffin wax, animal wax, plant wax, montan wax, polyethylene wax and polyethylene derivative wax.
A composition according to any of claims 1-9, further comprising a grease lubricant in the form of a solid or semifluid dispersion of a thickener in oil.
A composition according to any of claims 1-10, wherein the at least one emulsifier is selected from the group consisting of; Polyisobutylene succinic anhydride (PIBSA), PIBSA amine derivatives, Polyisobutenyl succinic acid anhydride (PIBDIBA), PIBDIBA derivates, PIB-lactone and its amino derivatives, Sorbitan monooleate (SMO), sorbitan sesquioleate, lecithin, alkoxylates, esters combinations, fatty amines, alkyloxazolines, alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates, phosphate esters and mixtures thereof.
A composition according to any of claims 1-11 wherein the apparent viscosity of the composition is between 35 000 and 120 000 centipoise (cP).
A composition according to any of the claims 2-12 wherein the density of the sensitized emulsion explosive is between 0.4-1.25 grams per cm³.
A composition according to any of claims 1-13, wherein the fuel phase comprises at least one oil having no more than 18 carbon atoms in the molecular structure, preferably 10 to 18 carbon atoms.
A method of preparing an emulsion type explosive composition, which method comprises;
- providing an oxidizer-phase comprising at least 35% by weight of hydrogen peroxide and at least 25% by weight of water,

- providing a fuel-phase comprising at least one primary oil type fuel with a flash point below 100 °C and at least one secondary oil type fuel with a flash point over 150° C,

- providing at least one emulsifier,

- forming an emulsion comprising the oxidizer-phase, the fuel-phase and the emulsifier, in which emulsion the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase, and

- sensitizing the emulsion by adding gas filled compressible solid micro-balloons, and/or by generating gas bubbles by means of a gassing agent and/or by adding gas bubbles to the emulsion.