WO2013082634A2

WO2013082634A2 - Base charge explosive formulation

Info

Publication number: WO2013082634A2
Application number: PCT/ZA2012/000087
Authority: WO
Inventors: Hendrik Cornelius Bezuidenhout; Etienne CLOETE
Original assignee: Ael Mining Services Limited
Priority date: 2011-11-30
Filing date: 2012-11-20
Publication date: 2013-06-06
Also published as: AR089046A1; WO2013082634A3; ZA201404062B

Abstract

A non-detonatable base charge explosive formulation for use in a detonator which includes a solution containing a plurality of salts and a binder.

Description

BASE CHARGE EXPLOSIVE FORMULATION

BACKGROUND OF THE INVENTION

[0001] This invention relates to a detonator base charge formulation.

[0002] In a detonator high energy performance requires maximum energy production per unit volume. Energy can be introduced into an explosive system through the use of strained rings. The nitro-or nitramine-groups are responsible for an appropriate oxygen balance and nitrogen content. This approach is currently applied in the manufacture of molecular explosives such as PETN, HMX, RDX and so on. Inorganic components such as perchlorates are also used as constituents in explosive formulations.

[0003] Molecular explosives are used as base charges in detonating systems and in main explosive charges. The molecular explosives are manufactured either to be in granular form (as a powder) or as biscuits i.e. in large chunks. The explosives are formed or loaded into specific shapes by means of press loading or cast loading. The choice of the explosive formulation which is used is primarily based on the sensitivity characteristics of the formulation.

[0004] The explosive formulations have distinct sensitivity characteristics towards physical factors such as impact, friction, electrostatic discharge and heat. These characteristics can be manipulated to some extent but fundamental changes are difficult to bring about. The characteristics also dictate the category and class into which an explosive formulation will be placed. The sensitivity of an explosive, particularly to impact or friction, constitutes a safety risk during manufacture, transport and usage, which must be addressed. [0005] An object of the present invention is to provide an alternative technique for applying an explosive system as a base charge.

SUMMARY OF INVENTION

[0006] The invention is based on the premise of incorporating a multicomponent non-energetic system into an initiator system. The required constituents are mixed in situ before being applied in accordance with design dictates.

[0007] The invention provides, in the first instance, a non-detonatable base charge explosive formulation for use in a detonator which includes a solution containing a plurality of salts and a binder.

[0008] Preferably the salts include sodium nitrate and calcium nitrate. [0009] The solution may be an aqueous solution.

[0010] The binder may be of any appropriate kind and may be an organic or inorganic system. The binder may be inert (i.e. non-energetic) or energetic.

[0011] The sodium nitrate and calcium nitrate can each have different particle size distributions. Alternatively, the sodium nitrate and calcium nitrate can have similar particle size distributions.

[0012] The invention further provides that the formulation can be used, in situ, to form an explosive composition by mixing the formulation with selected components or a mixture of components. Preferably the formulation is mixed with a combination of sodium perchlorate and nanoporous silicon. [0013] The sodium perchlorate may be in granular form with different particle sizes. Alternatively the particles may have similar sizes or the particles may have a bi- modular particle size distribution.

[0014] The nanoporous silicon may have a specific surface area produced from particles which have similar surface area distributions or from a mixture of particles which have different surface area distributions.

[0015] The nanoporous silicon may be treated, mixed or coated, with an oxidiser before being mixed with the sodium perchlorate.

[0016] The sodium perchlorate/nanoporous silicon mixture is a dry product. This product may include one or more inert or reactive additives that contribute to the explosive property of the formulation formed from a mixture of the wet and dry components. The additives may for example be selected from the following: aluminium powder, PETN, RDX and HMX. This list is exemplary only and is non- limiting.

[0017] Preferably a reaction between the wet and dry components, which form the explosive composition, is completed within a predetermined period which is not more than 30 minutes.

[0018] Preferably the chemical reaction is completed within a period which is greater than a predetermined minimum period e.g. 60 seconds.

DESCRIPTION OF PREFERRED EMBODIMENT

[0019] In one example of the invention measured quantities of sodium nitrate and calcium nitrate were mixed with water to form an aqueous solution to which guar gum was added. A dry mixture of measured quantities of sodium perchlorate and nanoporous silicon was prepared. Optionally the nanoporous silicon was treated with an oxidiser prior to being mixed with the sodium perchlorate. The nanoporous silicon had a specific surface area. The sodium perchlorate comprised particles with a particular size distribution or particles with a bi-modular size distribution.

[0020] Prior to usage the aqueous solution and the dry components are mixed to form an explosive formulation. This is done in situ. The reaction between the wet and dry components, to form the explosive formulation, is completed within controllable limits of exothermic temperature generation and within a reasonable time. The reaction time is preferably less than 30 minutes and is not shorter than, say 60 seconds. This represents a good compromise between safety and utility. ,

[0021] The resulting composition is sensitive to heat, friction and impact to such an extent that it can readily be initiated by any one of these stimuli at a suitable level. The chemical reaction does not produce excess quantities of gas.

[0022] Inert or reactive components can be added to the mixture to contribute to the explosive property of the end product. For example, components selected from aluminium powder and an energetic material, such as PETN, RDX and HMX, can be added, according to requirement, to the mixture.

[0023] It is noted that by-products generated during the mixing process do not affect the performance of the explosive formulation.

Claims

1. A non-detonatable base charge explosive formulation for use in a detonator which includes a solution containing a plurality of salts and a binder.

2. A formulation according to claim 1 wherein the salts include sodium nitrate and calcium nitrate.

3. A formulation according to claim 2 wherein the sodium nitrate and calcium nitrate have different particle size distributions.

4. A formulation according to claim 2 wherein the sodium nitrate and calcium nitrate have similar particle size distributions.

5. An explosive composition which comprises a mixture of a plurality of salts and a binder, and a combination of sodium perchlorate and nanoporous silicon.

6. A composition according to claim 5 wherein the salts include sodium nitrate and calcium nitrate.

7. A composition according to claim 5 or 6 wherein the sodium perchlorate is granular with particles of different sizes, similar sizes, or with a bi-modular particle size distribution.

8. A composition according to claim 5, 6 or 7 wherein the nanoporous silicon is mixed or coated with an oxidiser.

9. A composition according to any one of claims 5 to 8 wherein the combination of sodium perchlorate and nanoporous silicon includes at least one additive selected from the following: aluminium powder, PETN, RDX and HMX. A composition according to any one of claims 5 to 9 wherein a reaction between the salts and the combination of sodium perchlorate and nanoporous silicon is completed within a period which is greater than 60 seconds and which is less than 30 minutes.