GB2178736A

GB2178736A - Sensitized emulsion explosive

Info

Publication number: GB2178736A
Application number: GB08607293A
Authority: GB
Inventors: Helen Mcnamara
Original assignee: AECI Ltd
Current assignee: AECI Ltd
Priority date: 1985-08-07
Filing date: 1986-03-24
Publication date: 1987-02-18
Also published as: MW3786A1; GB8607293D0; ZW14786A1; NO863174L; BR8603500A; AU5618086A; NO863174D0

Abstract

The invention relates to a method for the manufacture of an emulsion explosive of the water-in-fuel type having as its discontinuous phase an oxidizing salt-containing component and as its continuous phase a fuel component which is immiscible with the discontinuous phase. In accordance with the method, the explosive is sensitized to detonation by admixing and dispersing in the emulsion a finely divided particulate metal and an acid, the metal and acid being selected to react together in the emulsion to produce gas bubbles therein.

Description

SPECIFICATION Sensitized emulsion explosive THIS INVENTION relates to an explosive. In particular the invention relates to the manufacture of an emulsion explosive having as its discontinuous phase an oxidizing salt-containing component and as its continuous phase a fuel component which is immiscible with the discontinuous phase.

Such explosives, where the oxidizing salt-containing component contains water and is in the form of an aqueous solution are known as "water-in-fuel" emulsions, and when the oxidizing salt component contains little or no water they can be regarded as "melt-in-fuel" emulsions.

According to the invention, in the manufacture of an emulsion explosive of the water-in-fuel type having as its discontinuous phase an oxidizing salt-containing component and as its continuous phase a fuel component which is immiscible with the discontinuous phase, the method of sensitizing the explosive to detonation which comprises dispersing in the emulsion a finely divided particulate metal and an acid, the metal and acid being selected to react together in the emulsion to produce gas bubbles therein.

The metal may be aluminium, and the aluminium may be added in a proportion of from 0,115% by mass of the emulsion into which it is dispersed.

The particles of the metal may be coated, the dispersing taking place in an environment wherein the coating is at least partially removed from the particles to expose metallic surfaces thereon to reaction with the acid. In this regard the Applicant has successfully employed a commercially available coated aluminium, ie "Supramex 2100", available from Metal Sales Company (Pty) Limited, which has, as impurities, manganese, magnesium, zinc, silicon, lead, nickel, copper and iron, and has a coating of aluminium stearate. In this case the dispersing should preferably take place at a temperature, eg at least 65"C, sufficient at least partially to remove the coating from the aluminium particles.

The acid may be dispersed in the emulsion by admixing it therein in the form of an aqueous solution, and may be incorporated into the discontinuous phase before the emulsion is formed.

The acid solution in the presence of the metal in the emulsion, acts as a sensitizing solution. In this case the acid may be a mineral acid, such as nitric acid, optionally buffered. The acid may be dispersed directly into the emulsion or it may be provided in the emulsion by dispersing an acid salt in the emulsion. Thus, an organic nitrate acid salt, such as hexamethylene tetramine dinitrate, may be dispersed in the emulsion by admixing hexamethylene tetramine into the emulsion together with an acid, such as nitric acid.

To obtain an aqueous acidic sensitizing solution in the form of an acid salt solution, acid may be added to a slurry formed from hexamethylene tetramine and water. Addition of the nitric acid to the hexamethylene tetramine in the form of a slurry is preferred to addition of nitric acid direct to the solid hexamethylene tetramine in the absence of water, because of the danger of undesirable side reactions in the absence of a slurry. The sensitizing solution is preferably saturated, to keep water addition to the eventual explosive product to a minimum, the amount and strength of the acid used on the one hand, and the amount of hexamethylene tetramine and proportion of water in the slurry on the other hand, preferably being selected in the stoichiometric proportions to produce hexamethylene tetramine dinitrate in the form of a saturated solution in the water present.

The addition of the nitric acid, which may for example be a 65% m/m aqueous solution, to the slurry may be at a temperature below 50"C, preferably below 40"C (to avoid formaldehyde production) to provide the acidic sensitizing solution. Instead, this addition can take place at substantially lower temperatures, eg 0 C, to provide a solid precipitate. After separation and washing, this precipitate can be dissolved in water at an elevated (eg 30-50"C) temperature to provide the acidic aqueous sensitizing solution.

As indicated above, hexamethylene tetramine dinitrate may be dispersed in the emulsion by admixing therein an aqueous solution which is saturated with regard to the hexamethylene tetramine dinitrate. A saturated solution of hexamethylene tetramine dinitrate in water contains about 37% by mass of water. The hexamethylene tetramine dinitrate may be dispersed in the emulsion in a proportion of from 3-20% by mass of the emulsion into which it is dispersed.

The sensitizing solution so obtained is safe, ie non-self-explosive, and can be admixed and dispersed into the emulsion as a final step in the manufacture of the eventual explosive, thereby enhancing safety.

As regards the addition of the metal and the sensitizing solution, an effective amount will in each case be added, effective to produce the desired increase in sensitivity to detonation. When the metal is Supramex 2100 aluminium, up to 15% by mass, and usually at least 2% may be used, based on the mass of the emulsion to which it is added. However, less metal, ie less than 2% by mass, can also be effective. Similarly, when the sensitizing solution is based on a theoretical stoichiometric yield of hexamethylene tetramine dinitrate as described above, the amount of sensitizing solution added is selected so that dinitrate is added in a proportion of up to 20% by mass, preferably at least 3% as indicated above, based on the mass of the emulsion (taken as 100%) to which it is added.

Instead, the acid may be an organic acid, such as oxalic acid. The organic acid may be dispersed in the emulsion by admixing therein an aqueous solution of the acid, optionally buffered. For example, the aqueous solution may comprise oxalic acid and potassium oxalate.

Whether a mineral acid, organic acid or acid salt is used, the proportion of acid used may be such as to provide the discontinuous phase of the emulsion with a pH of less than 3 at 90-100 C, preferably between 0,5 and 1,0 at 90-100 C.

If the acid is dispersed in the emulsion after formation of the emulsion, then the metal is preferably dispersed in the emulsion before the acid is dispersed in the emulsion, and the metal may be admixed into the emulsion at any convenient stage during the manufacture of the emulsion, which will typically be manufactured in conventional fashion. However, as mentioned above, the acid may be added to the discontinuous phase prior to the formation of the emulsion, the metal being dispersed in the emulsion after formation thereof.

The acid may be dispersed in the emulsion at an elevated temperature, the emulsion optionally being at a temperature of from 50-110"C, eg 90"C, and the acid being at a temperature of, for example, from 10-40"C, selected to resist high fume levels or acid decomposition. When the metal has a coating, such as when aluminium is coated with aluminium stearate, which can be removed by heat, this should be borne in mind when selecting the mixing temperature.

The metal and acid may be dispersed in the emulsion in proportions selected to produce sufficient gas bubbles therein so that its density is from 1,0-1,5 g/cm3 at 250C, preferably 1,10-1,35 g/cm3. As the production of gas bubbles is believed to be influenced by temperature, it may be desirable to store slow-reacting formulations at elevated temperatures, above the ambient temperature, for a suitable period, until the bubble-forming reaction is substantially complete.

The discontinuous phase may comprise at least one oxidizing salt selected from the group consisting in: ammonium nitrate alkali metal nitrates alkaline earth metal nitrates ammonium perchlorate urea alkali metal perchlorates and alkaline earth metal perchlorates.

When the discontinuous phase comprises a ammonium nitrate, it may comprise one or more further compounds such as sodium nitrate, calcium nitrate, urea or the like which, together with the ammonium nitrate, form a melt which has a melting point which is lower than that of the ammonium nitrate, the further compounds being capable of reacting as oxygen releasing salts or fuels. The discontinuous phase may in certain cases comprise water, which is kept to a minimum to avoid wasted energy arising from steam generation, but which is employed to facilitate melting/dissolving of the oxidizing salt component to avoid excessively high processing temperatures during formation of the base emulsion.When selecting the proportion of water used in the emulsion to which the sensitizing solution is added, the proportion of any water in such sensitizing solution as is used can be borne in mind, to determine the proportion of water which will be present in the final explosive product.

The fuel of the fuel component of the emulsion into which the metal and acid are admixed may form from 2-25% by mass of the emulsion, preferably about 3-12%.

The fuel of the fuel component of the emulsion will be immiscible with and insoluble in water, and may be non-self-explosive, comprising eg at least one member of the group consisting in hydrocarbons, halogenated hydrocarbons and nitrated hydrocarbons. Thus the fuel may comprise at least one member of the group consisting in mineral oils, fuel oils, lubricating oils, liquid paraffin, microcrystalline waxes, paraffin waxes, xylene, toluene, petrolatum, slack wax and dinitrotoluene.

The fuel component of the emulsion may comprise at least one emulsifier selected from the group consisting in sorbitan sesquioleate, sorbitan monooleate, sorbitan monopalmitate, sodium monostearate, sodium tristearate, the mono- and diglycerides of fat-forming fatty acids, soya bean lecithin, derivatives of lanolin, alkyl benzene sulphonates, oleyl acid phosphate, laurylamine acetate, decaglycerol decaoleate, decaglycerol decastearate, 2-oleyl-4,4'-bis(hydroxymethyl)-2-oxazoline, polymeric emulsifiers containing polyethylene glycol backbones with fatty acid side chains and polyisobutylene succinic anhydride derivatives.

The emulsifiers act as surfactants and stabilizers to promote the formation of the emulsion and to resist crystallization and/or coalescence of the discontinuous phase.

The method may include dispersing a density reducing agent therein to reduce the density of the emulsion to within the desired range of 1,0-1,5 g/cm3 mentioned above.

The eventual explosive may thus include micro-balloons micro-spheres or another form of density reducing agent, to provide the emulsion with the final desired density of eg 1.0-1.5 g/cm3 at 25"C. The emulsion may thus comprise up to about 10% by mass of the micro-balloons, which may be of glass (eg C15/250 glass micro-balloons available from 3M South Africa (Proprietary) Limited) or a polymeric material (which may be EXPANCEL 642 DE micro-spheres available from KemaNord AB, Sweden), which can further act to sensitize the explosive. Although the mass of micro-balloons included may be up to 10%, it is preferably less than 4.5% by mass based on the mass of emulsion to which they are added.When the explosive is however sufficiently sensitized by the gas bubbles formed by the reaction between the metal and acid, the additional density reducing agent can be omitted entirely.

The invention extends also to an emulsion explosive of the water-in-fuel type whenever sensitized in accordance with the method described above.

The invention will now be described, by way of non-limiting example, with reference to the following illustrative examples.

EXAMPLE 1 A standard control or base emulsion formulation was prepared, having the following composition: Constituent Percentage by mass (%m/m) Ammonium nitrate (oxidizing salt) 59,45 Sodium nitrate (oxidizing salt) 14.40 Calcium nitrate (oxidizing salt) 3,60 Water 12,30 P95 Mineral oil (fuel) 3,50 Sorbitan monooleate (emulsifier) 1,25 Soya lecithin (emulsifier) 0,50 Supramex 2100 aluminium 5,00 100,00 The P95 mineral oil was obtained from BP South Africa (Proprietary) Limited, and the sorbitan monooleate was obtained as CRILL-4 from Croda Chemicals SA (Proprietary) Limited.

This control or standard emulsion was found to have a critical density of 1,25 g/cm3 (obtained by a suitable addition of C15/250 micro-balloons or Expancel 642 DE micro-spheres) at which it detonated in 32 mm cartridges using a 6 D detonator containing 360 mg pentaerythritol tetranitrate (PETN) at a velocity of detonation of 4000 m/s.

EXAMPLE 2 An emulsion was prepared, essentially similar to the emulsion of Example 1, to which a sensitizing solution was added in accordance with the method of the present invention.

The sensitizing solution was prepared by mixing together particulate solid hexamethylene tetramine, a 65% by mass nitric acid solution and water. The water was added to the hexamethylene tetramine to form a slurry, to which the nitric acid was added. The addition of the nitric acid was at a rate, and the addition was controlled, so that the temperature did not exceed 40"C, and during the addition was between 30 and 40"C. The ratio between the hexamethylene tetramine, nitric acid and water employed was 1:1,4:0,6 on a mass basis, and this ratio was selected in accordance with the stoichiometric requirement to nitrate the hexamethylene tetramine to the dinitrate, and to provide a saturated solution of said dinitrate, containing about 37% by mass of water.

The emulsion similar to the emulsion of Example 1 was prepared having the following formulation: Constituent Percentage by mass (%m/m) Ammonium nitrate (oxidizing salt) 56,25 Sodium nitrate (oxidizing salt) 13,55 Calcium nitrate (oxidizing salt) 3,35 Water 9,70 P95 Mineral oil (fuel) 3,10 Emulsifier (Sorbitan monooleate/soya lecithin used together in the ratio of Example 1) 1,70 Supramax 2100 aluminium 4,55 Sensitizer solution (whose water content makes up 2,85% of the total formulation) 7,80 100,00 The total water in the emulsion accordingly was 2,85%+9,70%= 12,55% by mass.

Density reducing agent (C15/250 glass micro-balloons or Expancel 642 DE micro-spheres was added as required, in proportions of up to 3% by mass of the above formulation, to obtain varying densities. These formulations of different densities and containing density reducing agent were packaged into 32 mm cartridges, and were detonated using a 6 D detonator cap. Results are shown in the accompanying drawing, where velocity of detonation is plotted against density of the explosive composition. Density was measured using density liquids.

The above procedure was repeated, except that the aluminium in the above formulation was reduced so that it made up 3% by mass of the formulation set forth in the Table, the proportions of the other constituents remaining unchanged. Once again density reducing agent was added as required to obtain different densities, and these compositions were detonated by a 6 D cap in 32 mm cartridges. These results are also shown in the accompanying drawing, together with further similar results where the proportion in the Table of the aluminium was further reduced to 2% by mass.

EXAMPLE 3 A control emulsion substantially similar to that of Example 2 was prepared, but omitting the aluminium. This emulsion was found to have a critical density of 1,25 g/cm3.

EXAMPLE 4 An emulsion similar to that of Example 1 was prepared, but containing dispersed therein in addition, solid ammonium nitrate prills, and sensitizing solution as described above in Example 2.

This doped emulsion had the following formulation: Constituent Percentage by mass (%m/m) Ammonium nitrate (oxidizing salt) 44,80 Sodium nitrate (oxidizing salt) 10,80 Calcium nitrate (oxidizing salt) 2,65 Water 7,70 P95 Mineral oil (fuel) 2,90 Sorbitan monoolate (emulsifier) 0,95 Soya lecithin (emulsifier) 0,40 Ammonium nitrate prills (solid dopant) 20,00 Aluminium 3,60 Sensitizer solution (whose water content makes up 2,28% of the total formulation) 6,20 100,00 C15/250 glass micro-balloons used in proportions of up to 3% of the above formulation were used as density reducing agent. For various densities in 32 mm cartridges the minimum strength of detonating cap necessary for detonation was determined, and the velocity detonation was measured. These results are set out in the following Table.

TABLE Density (g/cm3) Velocity of detonation Minimum detonating (m/s) cap strength for detonation 1,40 2 626 6D 1,35 3 549 4D 1,25 4 167 4D 1,15 4 404 2D The 2D detonating cap used contained 22 mg PETN and the 4D detonating cap contained 90 mg of PETN. The bulk strength of the doped explosive was calculated, at a density of 1,4 gm/cm3, to be 174% ANFO (based on ammonium nitrate/fuel oil).

EXAMPLE 5 An emulsion was prepared having the following composition: Constituent Percentage by mass (%m/m) Ammonium nitrate (oxidizing salt) 66,73 Sodium nitrate (oxidizing salt) 12,5 Water 9,8 Microcrystalline wax (fuel) 1,4 Paraffin wax (fuel) 1,4 P95 Mineral Oil (fuel) 0,67 Sorbitan monooleate (emulsifier) 1,3 Supramex 2100 aluminium 6,2 100,00 To the above emulsion was added oxalic acid until the emulsion had a pH of 0,59 at 100"C.

The emulsion was cartridged in 32 mm sleeves and stored and cooled overnight in an insulated box. These cartridges had a final density of 1,22 g/cm3 and fired with a 2D detonating cap and had a velocity of detonation of 3 400 m/s. No density reducing agent such as micro-spheres or micro-balloons was added to this formulation. The microcrystalline wax and paraffin wax respectively were BE Square 175 obtained from Bareco Waxes, Tulsa, Oklahoma, USA and Sasolwaks M obtained from Sasol Marketing Co. (Pty) Ltd., Johannesburg.

EXAMPLE 6 A formulation similar to that of Example 5 was prepared except that it contained, in addition, 0,5% m/m potassium oxalate buffer. The discontinuous phase or melt (ie to ammonium nitrate, sodium nitrate and water) was accordingly reduced from 89,03% m/m of the formulation to 88,53% m/m with the constituents of the melt being present in the same proportions by mass as in Example 5. The pH was adjusted using oxalic acid to 0,72 at 90"C with the potassium oxalate and oxalic acid acting to buffer the discontinuous phase. This emulsion was loaded into cartridges as described above for Example 5 and were found to detonate with 2D a detonating cap at a velocity of detonation of 4 200 m/s. The addition of the oxalic acid was found to reduce, by bubble formation, the density of the formulation from 1,45 g/cm3 to 1,00 g/cm3.

EXAMPLE 7 A standard so-called Fall Hammer hazard test was carried out on a formulation essentially similar to that of Example 2, containing 5% by mass aluminium and containing 9,5% by mass of the sensitizing solution (ie about 6% active ingredient expressed as hexamethylene tetramine dinitrate). A 5 kg weight was used for the Fall Hammer test throughout. In some cases grit was mixed with the samples tested. No detonation occurred, for formulations having densities respectively of 1,45 g/cm3 and 1,25 g/cm3, in either in the presence or absence of grit, and from a fall height (the maximum fall height attainable on the apparatus) of 2 m.

Samples of these emulsions were dried to obtain a crystalline material which could show a different sensitivity. In each case, regardless of the density of the starting emulsion, and from a fall height of 2 m, there were for five tests in the presence of grit, and five tests in the absence of grit, again no detonations.

This compares with a standard nitroglycerin product, AG60, wherein the maximum fall height for no detonations was 16 cm.

Example 2 above demonstrated the utility of the sensitizing method and sensitizing solution of the present invention, when used with the SUPRAMAX 2100 aluminium. Detonation could be obtained in each case at substantially higher densities than the critical density of the control formulation of Example 1.

Example 3 demonstrated that sensitization does not occur unless the metal is dispersed in the emulsion.

Example 4 demonstrated that sensitization obtained with the present invention was sufficiently great to permit doping with ammonium nitrate prills to provide a doped explosive having a substantial bulk strength (174% ANFO) at a density of 1,4 g/cm3, and capable of detonation at densities up to 1,40 g/cm3 with a 6D detonator, and at lower densities with weaker detonators.

Example 5 demonstrated the utility of organic acids in the method of the present invention; and Example 6 demonstrated the use of an organic acid with a buffer in accordance with the method of the present invention, in making an explosive of reduced density which does not require micro-balloons or the like.

Example 7 demonstrated the substantial insensitivity of the explosive to detonation by impact.

The invention has a number of advantages. Thus, during formulation, the sensitizing solution can be the last component to be added, and can in principle be added after any density reducing agent has been added, thereby providing for enhanced safety during formulation. The sensitizing solution itself is explosively safe to handle, and is liquid, so that it can be handled easily.

There is substantial flexibility in the formulation steps, as regards the sequence of addition of the components. Indeed, if desired, the sensitizing solution can be added together with the oxidizing salt melt/solution, before making the emulsion.

A sensitized explosive is provided which can detonate at high densities, but which is extremely resistant to ignition/detonation by impact.

The present invention has the further advantage over other gassing systems, such as nitrite gassing, used for sensitizing and density reduction, in that, unlike the other systems, densities of less than 1,15 g/cm3 and high velocities of detonation greater than 4 000 m/s are obtainable in cartridge diameters down to 32 mm or possibly less, without the expense the inconvenience of high speed mixing. It is believed that, provided the metal and acid are uniformly mixed in the explosive, the bubbles will form in groups around or in the vicinity of the metal particles, so that each particle will be associated with a bubble or group of bubbles.It is also believed that further sensitization may arise from contact of the metal with hot spots in the explosive during detonation, although the reduction in density achieved should alone be sufficient to result in the elimination or at least a reduction in the use of relatively costly density reducing agents such as micro-balloons or the like.

Relatively high velocity of detonation explosives can be obtained with low densities, and velocity of detonation can be decreased by increasing the density, although there is a plateau with a relatively constant high velocity of detonation over a range of densities. If desired, the explosive can be detonated at low velocities of detonation and high densities, which is an unusual property which may be of use in certain mining applications. Furthermore, emulsions sensitized in accordance with the present invention may find application in cord-sensitive products such as secondary blasting agents, intermediate diameter (50-120 mm) products, or the like. Emulsions sensitized in such a manner and prepared to suitable sensitivities may also find application in small diameter, intermediate diameter and bulk emulsions, and may also be used in repumpable formulations.

Finally, doping with ammonium nitrate prills is possible, at levels of up to 20% by mass or more, for high energy and high bulk strength at high densities, coupled with reliable detonation.

Claims

1. In the manufacture of an emulsion explosive of the water-in-fuel type having as its discontinuous phase an oxidizing salt-containing component and as its continuous phase a fuel component which is immiscible with the discontinuous phase, the method of sensitizing the explosive to detonation comprising admixing and dispersing in the emulsion a finely divided particulate metal and an acid, the metal and acid being selected to react together in the emulsion to produce gas bubbles therein.

2. A method as claimed in Claim 1, in which the metal is aluminium.

3. A method as claimed in Claim 2, in which the aluminium is added in a proportion of from 0,1-15% by mass of the emulsion in which it is dispersed.

4. A method as claimed in any one of Claims 1 to 3 inclusive, in which the particles of the metal are coated and in which the dispersing takes place in an environment wherein the coating is at least partially removed from the particles to expose metallic surfaces thereon to reaction with the acid.

5. A method as claimed in any one of the preceding claims, in which the acid is dispersed in the emulsion by admixing it therein in the form of an aqueous solution.

6. A method as claimed in any one of the preceding claims, in which the acid is a mineral acid.

7. A method as claimed in Claim 6, in which the acid is nitric acid.

8. A method as claimed in any one of the preceding claims, in which the acid is provided in the emulsion by dispersing an acid salt in the emulsion.

9. A method as claimed in Claim 8, in which the acid salt is hexamethylene tetramine dinitrate, and is dispersed in the emulsion by admixing hexamethylene tetramine into the emulsion together with nitric acid.

10. A method as claimed in Claim 8, in which the hexamethylene tetramine dinitrate is dispersed in the emulsion by admixing therein an aqueous solution which is saturated with regard to the hexamethylene tetramine dinitrate.

11. A method as claimed in Claim 9 or Claim 10, in which the hexamethylene tetramine dinitrate is dispersed in the emulsion in a proportion of from 3-20% by mass of the emulsion in which it is dispersed.

12. A method as claimed in any one of Claims 1 to 5 inclusive, in which the acid is an organic acid.

13. A method as claimed in Claim 12, in which the organic acid is oxalic acid.

14. A method as claimed in Claim 12 or Claim 13, in which the organic acid is dispersed in the emulsion by admixing therein a buffered aqueous solution of the acid.

15. A method as claimed in Claim 14, in which the buffered aqueous solution comprises oxalic acid and potassium oxalate.

16. A method as claimed in any one of the preceding claims, in which the proportion of acid used is such as to provide the discontinuous phase of the emulsion with a pH of less than 3 at 90"C.

17. A method as claimed in Claim 16, in which the pH is between 0,5 and 1,0 at 90-100 C.

18. A method as claimed in any one of the preceding claims, in which the acid is dispersed in the emulsion after formation of the emulsion, metal being dispersed in the emulsion before the acid is dispersed in the emulsion.

19. A method as claimed in any one of Claims 1 to 17 inclusive, in which the acid is dispersed in the discontinuous phase prior to the formation of the emulsion, the metal being dispersed into the emulsion after formation thereof.

20. A method as claimed in any one of the preceding claims, in which the acid is dispersed in the emulsion at an elevated temperature, the emulsion being at a temperature of from 50-110"C and the acid being at a temperature of from 10-40"C.

21. A method as claimed in any one of the preceding claims, in which the metal and acid are dispersed in the emulsion in proportions selected to produce sufficient gas bubbles therein so that its density is from 1,0-1,5 g/cm3 at 25"C.

22. A method as claimed in any one of the preceding claims, in which the discontinuous phase comprises at least one oxidizing salt selected from the group consisting in: ammonium nitrate alkali metal nitrates alkaline earth metal nitrates ammonium perchlorate urea alkali metal perchlorates and alkaline earth metal perchlorates.

23. A method as claimed in any one of the preceding claims, in which the fuel of the fuel component of the emulsion into which the metal and acid are admixed forms from 2-2596 by mass of the emulsion.

24. A method as claimed in any one of the preceding claims, in which the fuel of the fuel component of the emulsion is non-self-explosive and comprises at least one member of the group consisting is hydrocarbons, halogenated hydrocarbons and nitrated hydrocarbons.

25. A method as claimed in Claim 24, in which said fuel comprises at least one member of the group consisting in mineral oils, fuel oils, lubricating oils, liquid paraffin, microcrystalline waxes, paraffin waxes, xylene, toluene, petrolatum, slack wax and dinitrotoluene.

26. A method as claimed in any one of the preceding claims, in which the fuel component of the emulsion comprises at least one emulsifier selected from the group consisting in sorbitan sesquioleate, sorbitan monooleate, sorbitan monopalmitate, sodium monostearate, sodium tristearate, the mono- and diglycerides of fat-forming fatty acids, soya beam lecithin, derivatives of lanolin, alkyl benzene sulphonates, oleyl acid phosphate, laurylamine acetate, decaglycerol decaoleate, decaglycerol decastearate, 2-oleyl-4,4'-bis-(hydroxymethyl)-2-oxazoline, polymeric emulsifiers containing polyethylene glycol backbones with fatty acid side chains and polyisobutylene succinic anhydride derivatives.

27. A method as claimed in any one of the preceding claims which includes dispersing a density reducing agent therein to reduce the density of the emulsion.

28. In the manufacture of an emulsion explosive of the water-in-fuel type having as its discontinuous phase an oxidizing salt-containing component and as its continuous phase a fuel component which is immiscible with the discontinuous phase, the method of sensitizing the explosive to detonation substantially as described herein.

29. An emulsion explosive of the water-in-fuel type whenever sensitized in accordance with the method of any of the preceding claims.

30. An emulsion explosive as claimed in Claim 29, substantially as described herein.