COMPOSITION FOR FORMING A HYDROGEN PEROXIDE BASED EMULSION EXPLOSIVE

Abstract

A composition for forming a hydrogen peroxide-based emulsion explosive which composition comprises; an oxidizer-phase comprising at least 15% by weight of hydrogen peroxide and at least 15% by weight of water, a fuel-phase comprising at least one oil type fuel, a liquid emulsifier and at least one finely divided colloidal non-sensitizing solid adsorbent, wherein the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase. A method of preparing an emulsion type explosive composition is also disclosed.

Claims

1. A composition for forming a hydrogen peroxide-based emulsion explosive which composition comprises; an oxidizer-phase comprising at least 15% by weight of hydrogen peroxide and at least 15% by weight of water, a fuel-phase comprising at least one oil type fuel, a liquid emulsifier, at least one finely divided solid colloidal non-sensitizing adsorbent, wherein the oxidizer-phase is discontinuously dispersed throughout the continuous fuel-phase.

2. A composition according to claim 1, further comprising a sensitizer, whereby the composition forms a sensitized emulsion explosive.

3. A composition according to claim 2, wherein the sensitizer comprises enclosed gas bubbles or voids which are generated inside the explosive composition through a chemical reaction.

4. A composition according to claim 2 wherein the sensitizer comprises enclosed gas bubbles or voids which are mechanically added into the explosive composition.

5. A composition according to claim 1 wherein at least a portion of the finely divided solid adsorbent may be wetted by both the oxidizer and the fuel phase.

6. A composition according to claim 1 wherein the particles of the finely divided solid adsorbent are smaller than 10 micrometres in average size.

7. A composition according to claim 1 wherein the finely divided solid adsorbent is included and dispersed in the continuous fuel-phase.

8. A composition according to claim 1 wherein the finely divided solid adsorbent comprises at least one solid selected from the group consisting of acrylic polymer powders, wheat, potato, rice or corn starch powders, organic gum powders, alginate cross linking powders, fumed silica powder, colloidal silica, silica powder, polymer zein powder, gluten powder, and clay particles.

9. A composition according to claim 1 wherein the oil type fuel comprises at least one oil selected from the group consisting of mineral oils, aromatic oils, bio-oils, synthetic fuel oils, diesel oils, lubrication oils, kerosene oils, naphtha oils, paraffin oils, chlorinated paraffin oils, benzene, toluene, polymeric oils, rapeseed oils, coconut oils and fish oils.

10. A composition according to claim 1 further comprising a density modifying additive fuel comprising at least one of aluminium powder, silica powder, sugars, glycerol, cellulose or alcohols.

11. A composition according to claim 1, wherein the emulsifier comprises at least one of Polyisobutylene succinic anhydride (PIBSA), PIBSA amine derivatives, PIB-lactone or its amino derivatives, Sorbitan monooleate (SMO), sorbitan sesquioleate, lecithin, alkoxylates, esters combinations, fatty amines, alkyloxazolines, alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates orphosphate esters.

12. A composition according to claim 1, wherein the composition contains less than 1.5% nitrates by weight.

13. A composition according to claim 1 wherein the apparent viscosity of the unsensitized composition is greater than 35 000 centipoises [cP] at 25? C.

14. A composition according to claim 2 wherein the density of the sensitized explosive composition is between 0.4 to 1.25 g/cm.sup.3.

15. A method of preparing an emulsion type explosive composition, which method comprises; providing an oxidizer-phase comprising at least 15% by weight of hydrogen peroxide and at least 15% by weight of water, providing a fuel-phase comprising at least one oil type, providing at least one liquid emulsifier, providing at least one finely divided solid colloidal non-sensitizing adsorbent, forming an emulsion comprising the oxidizer-phase, the fuel-phase, the emulsifier and the solid absorbent, 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.

Description

DETAILED DESCRIPTION OF EXAMPLES

[0086] According to one aspect there is provided a composition for forming a hydrogen peroxide based emulsion explosive. The composition comprises an oxidizer-phase comprising at least 15% by weight of hydrogen peroxide and at least 15% by weight of water which oxidizer-phase is discontinuously dispersed throughout a continuous fuel-phase comprising at least one oil type fuel. The composition further comprises an emulsifier and at least one finely divided solid collodial adsorbent.

[0087] 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 and the solid absorbent should be added to the fuel phase prior to mixing. Alternatively, the emulsifier and/or the solid colloidal absorbent 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 an oil-based fuel with the emulsifier and the finely divided solid adsorbent, 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.

[0088] By adding a sensitizer, the so formed composition becomes detonation enabled and explosive though initiation with conventional means, such a detonator with or without an amplification charge (known as a primer or booster). The sensitizer may be chemically generated though a chemical reaction between 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 (CH.sub.3COOH) 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.

[0089] In another embodiment, the sensitizer in the form of solid compressible gas filled micro-balloons is added mechanically and mixed into the composition making the composition detonation enabled immediately.

[0090] It will be appreciated that the composition can be used for many purposes, but in particular to break and move rock in mining operations.

[0091] According to different embodiments of the composition it many comprise the types of functional components listed in Table 1;

TABLE-US-00001 TABLE 1 Typical types of functional components and ratios of exemplifying compositions Ratios in % by weight of Type of functional component the total composition HP (primary oxidizer) From 15 to 85 Water From 15 to 55 Fuels From 2 to 15 Liquid emulsifiers From 0.5 to 5 Solid colloidal adsorbents From 0.01 to 2 Secondary fuels From 0 to 15 Secondary oxidizers From 0 to 50 Additives From 0 to 5

[0092] Such compositions may have the properties listed in Table 2:

TABLE-US-00002 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 0.3 to 1.5 Viscosity From 35000 to 120 000 cP Preparation temperature From 5 to 25? C. Velocity of detonation 2800-5500 m/s

[0093] Exemplifying typical substances for each type of functional component are listed in Table 3:

TABLE-US-00003 TABLE 3 Exemplifying substances comprised in the compositions Functional component Substance Oxidizers(s) At least 15% Hydrogen peroxide by weight, optionally potassium peroxide/and, or sodium peroxide/and, or perchlorate salts/and, or chlorate salts. Fuel(s) Water immiscible fuels and optionally water miscible fuels Lidquid emulsifiers Emulsifiers containing simultaneously lipophilic and hydrophilic moieties (PIBSA, SMO or the like) in liquid form. Solid colloidal Finley divided colloidal solids which can be adsorbents adsorbed and wetted at the interface between the two liquid phases to form a film of particles around the dispersed phases. No limiting examples are gums, cross linkers, poly acrylic acids (tradenames Carbopol, carbomer, Utrez, Floset), starches (wheat, corn, rice, potato), polymer zein, fumed silica, colloidal silica, silica powder, titanium dioxide, clay particles. Additives pH adjusters, thickeners, rheology modifiers, phosphonic or tin based HP stabilizers. Sensitizer Gas filled voids or bubbles either chemically generated (delayed or instant) and/or gas entrapped compressible materials.

EXAMPLES

[0094] The present invention can be used for a variety of forms of emulsion type explosive compositions provided that the principles of the invention as described herein are observed. The invention is further illustrated with reference to the following examples.

Example 1

[0095] A hydrogen peroxide emulsion formulation containing an oil-based fuel phase was calculated and hand made at a preparation temperature of 14? C. using a bench drill driven mixer. The oil phase combined one PIBSA type emulsifier and one SMO type emulsifier with a HP and water solution of 49.9% by weight concentration. A mineral oil with density of 0.83 g/cm.sup.3 was selected and combined with the two emulsifiers. 4 attempts to emulsify the above was conducted, 2 attempts without any solid adsorbent and 2 attempts with addition of approximately 0.8% by weight of a finely divided solid adsorbent in the form of powdery wheat starch (wheat flour) with an estimated particle size of 10-40 microns. Phase separation (ps) and pH was monitored over a 5-day period. The samples were stored in room temperature (21? C.). Oxygen balance was calculated to ?4%. If phase separation was detected, no further test where done. Density of the samples day 1 was approximately 1.15 g/cm.sup.3.

TABLE-US-00004 TABLE 3 Phase separation and pH change during 5 days using compositions with and without solid adsorbent. Solid Ps/pH Ps/pH Ps/pH Ps/pH Ps/pH Sample adsorbent day 1 day 2 day 3 day 4 day 5 1 Yes No/3.7 No/3.67 No/3.4 No/3.3 No/3.27 2 Yes No/3.9 No/3.82 No/3.8 No/3.4 No/3.4 3 No No/3.3 No/3.1 Yes/ 4 No No/2.8 Yes/

[0096] The formulations with adsorbent where significantly easier to emulsify. The PH levels stayed significantly more stable of multiple days indicating less separation between HP and fuel.

Example 2

[0097] Gassing stability tests were performed using a chemical gassing agent in combination with an emulsion composition similar to example 1 including a solid adsorbent. The composition emulsified readily at 15? C. using a bench drill driven mixer resulting in a measured viscosity of 112 000 cP. The estimated oxygen balance was calculated to ?5.4%. 1% of gassing agent was incorporated. 3 samples of the gassed emulsion were placed in a density cup. Once gassing had finished, the excess emulsion which had risen over the cup was cut and discarded, remaining gassed emulsion inside the cup was checked for density over the following 5 days. The sensitized emulsion was stored in room temperature.

TABLE-US-00005 TABLE 4 Density change in gassed HP emulsion Un sensitized Gassed Day Day Day Day Day Sample density density 1 2 3 4 5 1 1.15 0.98 0.97 0.94 0.94 0.93 0.93 2 1.15 1.03 1.01 1.00 0.98 0.97 0.97 3 1.15 1.05 1.05 1.03 1.03 1.02 1.00

[0098] Attempts to gas emulsions without adsorbents were made, however, the gassing in these instances caused the emulsion to separate and destabilized within a few hours.

Example 3

[0099] Detonation testing of the above compositions comprising a solid adsorbent were performed where the compositions where chemically gassed and pumped into drilled holes in boulders. The holes were drilled to a diameter of 48 mm and charges of about 1 kg where used. Initiation was done with an 8 d electric detonator in combination with a 20 gram PETN primer. VOD was measured using the MREL microtrap copper probes. The charges were left to sleep in the holes for 48 hours at a temperature of 12-14? C. Detonation speeds from 4100 to 4300 m/s where measured and performance where deemed acceptable for mining applications.

[0100] 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.