CA2260467A1 - Anfo explosives using an emulsified fuel phase - Google Patents

Abstract

The present invention is directed to the manufacture of an ANFO
explosive wherein the fuel phase is added to an oxidizer salt in the form of an emulsified fuel blend. A preferred fuel blend includes the use of a glycol, polyglycol and/or glycol ether in combination with a fuel oil. The emulsified fuel blend can be used to prepare ANFO explosives with modified performance properties.

Description

ANFO Explosives Using an Emulsified Fuel Phase Field of the Invention The present invention is related to the explosives art, and in particular, is related to the production of an ANFO explosive.
Descr~tion of the Related Art Industrial blasting agents form an important component of the mining industry. An important form of the explosives used in this industry is in the form of a mixture of about 94%, by weight, ammonium nitrate (AN) and about 6%
fuel oil (FO). This material is widely used in the explosives industry as a safe, low cost blasting agent, and is generally referred to, in the industry, as an ANFO explosive.
While ANFO is commonly used in the industry, variations of this product are also used to provide modified performance properties. These variations include ANFO products wherein either the ammonium nitrate has been at least partially replaced by other nitrate salt oxidizers, or wherein the fuel oil has been at least partially replaced by other fuel oil-like materials. These other fuel oil-like materials include materials such as other organic fuels which may be chosen from diesel oil, distillate, furnace oil, kerosene, naphtha, waxes, (e.g.
microcrystalline wax, paraffin wax and slack wax), paraffin oils, benzene, toluene, xylenes, asphaltic materials, polymeric oils such as the low molecular weight polymers of olefins, animal oils, fish oils, vegetable oils, and other mineral, hydrocarbon or fatty oils, and mixtures thereof. Further, these other organic fuels may include liquid hydrocarbons which may be generally referred to as petroleum distillate and include materials such as gasoline, kerosene, and paraffin oils.

_2_ These ANFO explosives with modified fuel phases may be referred to as ANFOR explosives wherein ANFOR means ammonium nitrate - fuel oil replacement. However, for the purposes of this document, the term ANFO is meant to include ANFO her se, and ANFOR explosives.
ANFO explosives may also be modified by the addition of materials such as emulsion explosives to provide a material termed as a Heavy ANFO, or by the addition of thickening materials or chemical cross-linking materials to provide improved water resistance.
Generally, the production and use of these ANFO explosives is well known in the industry. However, while these ANFO explosives are widely used, there remains a need in the industry for improved ANFO formulations which have improved properties over the prior art formulations.
In one known variation of interest in the present application, Stromquest et al., in U.S. Patent No. 5,531,843, describe an ANFO explosive wherein the fuel oil component is at least partially replaced by a material described as a "glycol still bottom". These glycol still bottoms are described further and in more detail, hereinbelow.
In a further variation, McNicol in U.S. Patent No. 5700970 describes an ANFO explosive wherein the "fuel oil" component is comprised of a homogeneous mixture of glycol still bottoms and a waste emulsion explosive.
This homogeneous mixture is then used in a conventional manner as a liquid component in the production of an ANFO explosive.
While these formulations have some improved properties, there continues to be further interest in developing new ANFO formulations.
Summary of the Invention Accordingly, the present invention provides a process for the production of an ANFO-type explosive comprising mixing an oxidizer salt, and preferably, a nitrate oxidizer salt, with a fuel phase, characterized in that said fuel phase is an emulsified fuel blend which comprises an emulsified mixture of an organic fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof.

A preferred form of a mixture of the glycol, polyglycol and/or glycol ether is available as polyglycol still bottoms.
The present invention also provides for an ANFO-type explosive comprising an oxidizer salt and a fuel phase, characterized in that said fuel phase is an emulsified fuel blend which comprises an emulsified mixture of an organic fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof.
Detailed Description of the Preferred Embodiments The glycol, polyglycol or glycol ether materials utilized in the practise of the present invention are preferably commonly occurring materials which can be readily, and inexpensively obtained. These include materials having the formula:
HO-[CR,Rz-CRsR4-OJ"-H
wherein R, to R, are each independently hydrogen or C, to C,o alkyl, and more preferably hydrogen or C, to Cs alkyl, and 'n' is from 1 to 30 and more preferably, from 1 to 6; or mixtures thereof and therebetween. Most preferably, no more than one of R, to R4 is other than hydrogen.
Accordingly, the glycol, polyglycol or glycol ether materials are preferably a mono-, bi-, tri- etc. ethylene glycol and their methyl, ethyl, propyl etc. ethers. These glycol, polyglycol or glycol ether materials are readily available from commercial suppliers. However, it is also possible to use waste glycols or polyglycol materials, such as for example, waste automotive antifreeze glycols, which are primarily ethylene glycol.
Also, preferably, the glycol, polyglycol or glycol ether materials utilized is a polyglycol which contains ether and hydroxyl functionality, or is a mixture of both glycols and polyglycols containing a variety of ether and hydroxyl groups. A most preferred material for this application is a "polyglycol still bottom" material as previously described. One preferred material of the s~ 2ooa polyglycol bottom type is commercially available from, for example, KMCO Inc.
of the United States, under the trade name of PGB-90. This material is described by the supplier as a mixture of glycols and polyglycols which are available as a black liquid having a boiling point of (about) 245°C, a pH of 6.5-9.0, a density of 1.125-1.200 and a freezing point of less than -45°C.
These polyglycol bottoms are generally supplied containing some water which is generally not detrimental to the process of the present invention.
These glycol still bottoms are the waste product remaining in distillation units during the process for making marketable glycol products. Commercial glycol producers extract ethylene glycol, diethylene glycol, triethylene glycol and other lower glycols from a mixed glycol starting material. The remaining material in the distillation tower is used to extract additional lower glycols. The material remaining after extraction of the lower glycols is a still more concentrated form of a waste material and is known in the industry as "glycol still bottoms" (or polyglycol still bottoms).
A typical sample of commercially available polyglycol still bottoms generally comprises a mixture of lower and higher glycols, polyglycols, glycol-ethers as well as various derivatives, and may have the general composition as set out in Table 1. However, this composition may vary from sample to sample.

Table 1 - Typical Polyglycol Still Bottoms Organic Component Composition' Com onent % b wei ht Dieth lene 3.71 I col Dieth lene 2.41 I col but I ether Trieth lenecol 22.68 I

Trieth lenecol eth I ether 3.43 I

Tetraeth I col 26.66 lene Tetraeth I col eth I ether 2.08 lene Tetraeth I col but I ether 1.62 lens Pentaeth I col 13.03 lene Pentaeth I col eth I ether 2.85 lene Pentaeth I col hex I ether 1.08 lene Pentaeth I col but I ether 6.24 lene Hexaeth I col 2.5 lene Hexaeth I col but I ether 6.56 lane He taeth I col but I ether 4.34 lene Octaeth I col but I ether 0.8 lene * - Polyglycol still bottoms, as received, typically comprise a mixture of about 80°r6 organic material and about 20% by weight of water. The amount of water can vary.
In the practise of the present invention, the polyglycol still bottoms may be emulsified with any of the fuel phases used in the production of ANFO-type explosives. This includes the fuel phase materials described hereinabove with reference to the prior art, and, in particular, includes materials such as fuel oil, diesel fuel, vegetable oil, tall oil, motor oil, waste oils (comprising waste motor oil, hydraulic oil and the like), and waste emulsion explosive materials.
The level of "fuel" phase in the emulsified fuel blend may vary from 5 to 95%, by weight, more preferably from 10 to 50%, and most preferably, from 15 to 30% by weight, fuel.

The emulsified blend is manufactured by mixing the fuel phase with the glycol, polyglycol and/or glycol ether, optionally, in combination with an emulsifying agent.
Suitable emulsifying agents may be chosen from the wide range of emulsifying agents, but can include emulsifying agents such as alcohol alkoxylates, phenol alkoxylates, poly(oxyalkylene) glycols, poly(oxyalkylene) fatty acid esters, amine alkoxylates, fatty acid esters of sorbitol and glycerol, fatty acid salts, sorbitan esters, poly(oxyalkylene) sorbitan esters, fatty amine alkoxylates, poly(oxyalkylene)glycol esters, fatty acid amides, fatty acid amide alkoxylates, fatty amine, quaternary amines, alkyloxazolines, alkenyloxazolines, imidazolines, alkyl-sulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkylphosphates, alkenylphosphates, phosphate esters, lecithin, copolymers of poly(oxyalkylene) glycols and poly(12-hydroxystearic acid), condensation products of compounds comprising at least one primary amine and poly[alk(en)yl]succinic acid or anhydride, and mixtures thereof.
Among the preferred emulsifying agents are the 2-alkyl- and 2-alkenyl-4,4'-bis(hydroxymethyl)oxazolines, the fatty acid esters of sorbitol, lecithin, copolymers of poly(oxyalkylene)glycols and poly(12-hydroxystearic acid), condensation products of compounds comprising at least one primary amine and poly[alk(en)yl]succinic acid or anhydride, and mixtures thereof.
More preferably the emulsifier component comprises a condensation product of a compound comprising at least one primary amine and a poly[alk(en)yl]succinic acid or anhydride. A preferred emulsifier is a polyisobutylene succinic anhydride (PIBSA) based surfactant, which are known in the emulsion explosives industry. As an example, suitable PIBSA-based surfactants can include the condensation product of a poly[alk(en)yl]succinic anhydride and an amine such as ethylene diamine, diethylene triamine and ethanolamine. Further examples of preferred condensation products may be found in the emulsion explosive prior art.
The level of emulsifying agent is preferably from 0 to 5%, by weight of the emulsified fuel blend. Higher levels of the emulsifier agent may be used and may serve as a supplemental fuel for the composition, but in general it is s~ 2oos not necessary to add more than 5% by weight of emulsifier component to achieve the desired effect. Stable emulsions can be formed using relatively low levels of emulsifier component and for reasons of economy, it is preferable to keep to the minimum amounts of emulsifier necessary to achieve the desired effect. The preferred level of emulsifier component used is in the range of from 0.1 to 3.0% by weight of the emulsion explosive.
In a particularly preferred method, however, the glycol, polyglycol, or glycol ether and fuel mixture is self-emulsifying (that is, that no added emulsifying agent is required). Further, it has been found that use of a standard polyglycol still bottom material provides such a self-emulsifying mixture. The emulsions formed using polyglycol still bottoms are generally stable over time.
It is believed that the glycol ethers assist in the emulsification process.
Accordingly, it is preferred that the emulsified fuel blend comprise between 0.1 and 50°r6 glycol ether, more preferably between 1 and 30% glycol ether, and most preferably, between 3 and 15°~ glycol ether. Suitable glycol ethers include any of the glycol ethers listed in Table 1, or mixtures thereof. Most preferably, the glycol ether is a methyl ether.
Emulsification of the fuel blend is achieved by standard emulsification techniques, which can include rapidly mixing the two components until an emulsion forms in the presence of an added emulsifying agent (when added).
The emulsification is generally conducted at ambient temperatures but can be prepared at any suitable temperature where the polyglycol still bottoms and/or the fuel phase remains liquid or liquifiable.
Not to be bound by theory, it is believed that polyglycol still bottoms have improved absorption into the oxidizer salt. It is believed that this occurs because of their generally lower surface tension, and because, the oxidizer salts are slightly soluble in the polyglycol still bottoms. These features tend to allow the emulsified fuel blend to be absorbed into the oxidizer salt more effectively than traditional fuel oil only materials.

~L 2008 _g_ It should also be noted that, typically, the emulsified fuel blend is not an explosive, or in particular, a sensitized explosive, and thus may be safely and readily handled and transported.
The level of the emulsified fuel blend used in the preparation of the ANFO explosive is dependent on the oxidizer salt chosen and the desired properties of the explosive to be produced. If possible, it is preferable that the ANFO be oxygen balanced in order to minimize or avoid the generation of noxious, gaseous by-products. Additional components may be added to the explosive composition to control the oxygen balance of the explosive composition.
Any one of a variety of solid oxidizer salts may be utilized in this application. Preferred oxidizer salts in this application include alkali and alkaline earth metal nitrates, chlorates and perchlorate, and included materials such as ammonium nitrate, calcium nitrate, ammonium chlorate, ammonium perchlorate and mixtures thereof. Most preferably, the oxidizer salt is ammonium nitrate or a mixture of ammonium nitrate with less than 25%, by weight, of a second oxidizer salt. Further, it is preferred that the ammonium nitrate is in grill form. It is also preferable that the ammonium nitrate grill be an explosive grade ammonium nitrate (EGAN), which thus, provides sufficient oil absorption to provide an ANFO-type explosive. However, fertilizer grade ammonium nitrate may also be used.
In particular, because of the ability of the polyglycol still bottoms-containing emulsified fuel blend to be more effectively absorbed into the oxidizer salt, it is possible to use higher density oxidizer salts (and higher density ammonium nitrate in particular) to form a higher density ANFO-type material. Achievement of this higher density provides a method for those skilled in the art to control the performance of the ANFO explosive.
Additionally, in order to raise the density further, it is possible to add oxidizer salt "fines" to the mixture to replace some of the grilled material.
These "fines" are small sized particles of the oxidizer salt. Generally, their particle size is less than 1 mm while the size of an oxidizer salt grill is 5mm or more. Up to 50% of the oxidizer salt may be present as fines. However, more _g_ preferably up to 35%, and more preferably, up to 30% of the oxidizer salt is present as "fines".
In a preferred feature, the ANFO produced according to the present invention is produced on site and may be loaded directly into the borehole.
However, the product may also be prepared off-site, and may be shipped in bulk, or as a packaged product, so long as the stability of the individual composition is satisfactory for the intended use.
Further, the product prepared may then be used as part of various known explosive compositions utilizing ANFO-type explosives. These include, for example, Heavy ANFO, doped emulsions, and the like, which are known within the industry.
The ANFO explosive composition may be used in combination with other materials to vary the explosive output of the formulation. This includes, for example, the addition of materials such as emulsion explosives to produce Heavy ANFO, or the addition of low weight materials such as polystyrene in order to lower the density of the ANFO material. These materials are commonly used in the explosives industry to vary the density and/or the sensitivity of the explosive composition.
Examples In the following examples, all percentages are by weight unless otherwise stated. The primers used for detonation included P-8 and P-16 Pentalite primers containing 8 oz. (227 g) or 16 oz. (454 g) Pentalite respectively.
Example 1 An ANFO-type explosive was prepared having the following formulation:
Ammonium nitrate (AN) 90%
Polyglycol still bottoms (PGSB) 8%
Diesel Oil 2%

The diesel oil and polyglycol still bottoms were mixed at high speed until a stable emulsion formed. The emulsion was then slowly added to the EGAN
prills with stirring. The resulting product was a slightly wet prill.
The product had a density of about 0.95 to 1.00 g/cc. and was essentially oxygen balanced. The product detonated in an unconfined 75 mm tube using a P-16 primer. It had a velocity of detonation of 1.9 km/second.
The product was not cap-sensitive.
Example 2 A second explosive was prepared using the same procedures as in Example 1. The explosive had the following formulation:
Ex. 2A Ex. 2B
Ammonium nitrate 85% 90%
PGSB 12% 8%
Waste Motor Oil 3% 2%
The product from example 2A had a tapped density of 1.00 g/cc and had a velocity of detonation of 2.0 km/second in a 1 OOmm diameter container with a P-16 primer. The product from example 2B had a tapped density of 0.97 glcc and had a velocity of detonation of 2.0 kmlsecond in a 88mm diameter container with a P-16 primer, 2.7 km/second in a 1 OOmm container with a P-8 primer, 2.7 kmlsecond in a 125mm container with a P-8 primer, and 1.9 km/second in a 75mm container with a P-16 primer.
Example 3 A product was prepared having the same formulation as in Example 1 with the exception that the diesel oil was replaced by tall oil. The product had a loose density of 0.89 g/cc and a tapped density of 0.99 g/cc. In a 75mm container, the product detonated at 1.9 km/second using a P-16 primer.
Example 4 Various products prepared according to the present invention were compared to a standard ANFO product (94% ammonium nitrate with 6% fuel oil) and to a ANFO-type product prepared using only polyglycol still bottoms (85°~ AN with 15°~ PGSB). The products of the present invention had a formulation of 90% ammonium nitrate, 8% PGSB and 2% oil. The oil was selected from vegetable oil, waste oil, diesel oil or tall oil as indicated below.
The performance of each was compared using a P-8 primer 1 day after preparation and 2 months after preparation.

Product Container Diameter VOD (km/secl mm After 1 da O 65 1.4 PGSB 65 Failed PGSB 75 Failed Ve etable Oil 65 Failed Ve etable Oil 75 1.2 Waste Oil 65 Failed Waste Oil 75 Burned Diesel Oil 65 1.1 Diesel Oil 75 1.6 Tall Oil 65 1.5 Tall Oil 75 1.9 After 2 months:

ANFO 65 1.7 Ve etable Oil 65 Burned Ve etable Oil 75 2 Waste Oil 65 1.8 Diesel Oil 65 1.8 Tall Oil 65 1.2 Tall Oil 75 1.8 Example 5 Products having a formulation as in Example 1 were prepared using different oils in place of the diesel oil. The densities of the product when poured loosely into a container, and after being tapped down were compared.
Product Density in a/cc Fuel Oil Tall Oil Waste Oil Corn Oil Loose Packed0.92 0.93 0.89 0.89 Ta ed Down 0.98 0.97 0.94 0.94 . SL 2008 Example 6 The effect of replacing some of the ammonium nitrate prills with ammonium nitrate fines was investigated using the following formulations. The products were prepared by the method of Example 1.
Ex.6A Ex.6B Ex.6 Ammonium nitrate prills 60% 70% 65%

Ammonium nitrate fines 30 20 25 Fuel Oil 2 2 2 Density - loose (g/cc) 0.89 0.87 0.86 Density - tapped (g/cc) 1.09 1.05 1.06 VOD(km/sec) - 75mm 2.4 (P-16) - -- 65mm 1.3 (P-8) - -Having described specific embodiments of the present invention, it will be understood that modifications thereof may be suggested to those skilled in the art, and it is intended to cover all such modifications as fall within the scope of the appended claims. Additionally, for clarity and unless otherwise stated, the word "comprise" and variations of the word such as "comprising"
and °comprises", when used in the description and claims of the present specification, is not intended to exclude other additives, components, integers or steps.

Claims (31)

1. A process for the production of an ANFO-type explosive comprising mixing an oxidizer salt with a fuel phase, characterized in that said fuel phase is an emulsified fuel blend which comprises an emulsified mixture of an organic fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof.

2. A process as claimed in Claim 1 wherein said glycol, polyglycol or glycol ether material has the formula:
HO-[CR1R2-CR3R4-O]n-H
wherein R1 to R4 are each independently hydrogen or C1 to C10 alkyl, and 'n' is from 1 to 30; or mixtures thereof and therebetween.

3. A process as claimed in Claim 2 wherein no more than one of R1 to R4 is other than hydrogen

4. A process as claimed in Claim 2 wherein R1 to R4 are each independently hydrogen or C1 to C6 alkyl.

5. A process as claimed in Claim 2 wherein 'n' is from 1 to 6.

6. A process as claimed in Claim 1 wherein the glycol, polyglycol or glycol ether is a mono-, bi-, tri-ethylene glycol or their methyl, ethyl, propyl ethers.

7. A process as claimed in Claim 1 wherein said glycol, polyglycol or glycol ether is a polyglycol still bottoms.

8. A process as claimed in Claim 1 wherein said glycol, polyglycol or glycol ether is an automotive antifreeze, or a waste automotive antifreeze.

9. A process as claimed in Claim 1 wherein said organic fuel is fuel oil, diesel fuel, vegetable oil, tall oil, motor oil, and or a waste oil.

10. A process as claimed in Claim 1 wherein said emulsified fuel blend comprises between 5 to 95%, by weight of said organic fuel.

11. A process as claimed in Claim 10 wherein said emulsified fuel blend comprises between 10 to 50%, by weight of said organic fuel.

12. A process as claimed in Claim 10 wherein said emulsified fuel blend comprises between 15 to 30%, by weight of said organic fuel.

13. A process as claimed in Claim 1 additionally comprising an emulsifying agent.

14. A process as claimed in Claim 13 comprising up to 5%, by weight of the emulsified fuel blend, of an emulsifying agent.

15. A process as claimed in Claim 14 comprising 0.1 to 3% of an emulsifying agent.

16. A process as claimed in Claim 1 wherein the mixture of the glycol, polyglycol, or glycol ether and the organic fuel, is self-emulsifying.

17. A process as claimed in Claim 1 wherein the emulsified fuel blend comprises between 0.1 and 50% glycol ether.

18. A process as claimed in Claim 17 wherein the emulsified fuel blend comprises between 1 and 30% glycol ether.

19. A process as claimed in Claim 17 wherein the emulsified fuel blend comprises between 3 and 15% glycol ether.

20. A process as claimed in Claim 17 wherein said glycol ether is a methyl ether.

21. A process as claimed in Claim 1 wherein said ANFO-type explosive is oxygen balanced.

22. A process as claimed in Claim 1 wherein said oxidizer salt is an alkali or alkaline earth metal nitrates, chlorates and perchlorate.

23. A process as claimed in Claim 22 wherein said oxidizer salt is ammonium nitrate, calcium nitrate, ammonium chlorate, ammonium perchlorate or mixtures thereof.

24. A process as claimed in Claim 22 wherein said oxidizer salt is a mixture of greater than 75% ammonium nitrate and up to 25% of a second oxidizer salt.

25. A process as claimed in Claim 22 wherein said oxidizer salt is ammonium nitrate.

26. A process as claimed in any one of Claims 23 to 25 wherein said ammonium nitrate is in prill form.

27. A process as claimed in Claim 26 wherein up to 50% of said ammonium nitrate is in the form of 'fines'.

28. A process as claimed in Claim 27 wherein up to 35% of said ammonium nitrate is in the form of 'fines'.

29. A process as claimed in Claim 28 wherein between 1 and 30% of said ammonium nitrate is in the form of "fines".

30. An ANFO-type explosive comprising an oxidizer salt and a fuel phase, characterized in that said fuel phase is an emulsified fuel blend which comprises an emulsified mixture of an organic fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof.

31. An ANFO-type explosive comprising an oxidizer salt and a fuel phase, characterized in that said fuel phase is an emulsified fuel blend which comprises an emulsified mixture of an organic fuel and a glycol, polyglycol or glycol ether material, or a mixture thereof, manufactured by a process as claimed in any one of Claims 1 to 30.