OA17077A

OA17077A - Oxidizer solution.

Info

Publication number: OA17077A
Application number: OA1201400366
Authority: OA
Inventors: Leon Michael Zimmermann
Original assignee: Maxam Dantex South Africa (Proprietary) Limited
Priority date: 2012-02-10
Filing date: 2013-02-11
Publication date: 2016-03-23

Abstract

According to this invention there is provided an aqueous oxidizer solution containing a mixture of dissolved oxidizing salts, for use in the preparation of explosives formulations, which a crystallization point as low as below 0°C. The solution has a water content of 25% by mass or less and contains ammonium nitrate and calcium nitrate wherein the ratio of the molar concentration of ammonium nitrate to calcium nitrate is preferably approximately 1. When the water content of the solution is 24% by mass or less, the solution further contains monomethylammonium nitrate. This solution can be used for manufacturing watergel explosives, or emulsion explosives or ANE's (ammonium nitrate emulsion suspension or gel explosives). It can be easily transported underground in deep level mines through relatively small diameter pipelines, using existing access ways and shafts, to the working places at which point it can then be converted into a watergel or emulsion explosive or an ANE.

Description

OXIDIZER SOLUTION

BACKGROUND OF THE INVENTION ln most countrles where bulk explosives are used they fall ln a category defined in the United Nations Handbook on the Transportation of Dangerous Goods as ammonium nitrate émulsions suspensions or gels (abbreviated ANE) and are transported and stored as oxidizers 5.1 with U.N. number 3375. As the name Implies these are either ln the form of émulsions or watergels (or k

s lûmes). Because they are not dassified as explosives the régulations regarding transportation and storage are considerably less stringent than they would be If they were dassified as explosives. These ANE's are sensitized to become explosives as they are pumped into the blast hole ether by mechanical gas entrainment or by the addition of a chemical blowing agent during the pumplng process.

One of the problème with existing buik explosives formulations (whether they are of the watergel or émulsion type) are that they are extremely viscous fluids and are difficult to pump or transport ln pipelines over long distances. This is not normally a probiem in surface mining where vehide access is simpiy a marier of driving to the hole to be charged and lowering the charging hose down the hole and then pumping the explosive into the hole. However when using bulk products in underground applications It would be very convenient if one could place the pumplng unit at a point some distance from the working face to be charged and simpiy run a long length of hose to the hole to be charged. This is especially true ln narrow reef stoping as encountered ln many gold and platinum mines.

A second probiem Is the probiem of getting the explosive underground in the first place. Since this must be done by transporting it in containers using the same lifting equipment or access ways used for men, equipment and ore, this can seriously hamper production. Since they are non-explosive until they are pumped Into the shot hole It Is at least theoretically possible to pump them through a long pipeline to the point where they are needed underground. Here again the viscosity is a probiem as there is a finite iimit on how far a viscous fluid can be pumped bearing in mind the energetic nature of the material being pumped and therefore the limitation on maximum pumping pressure to which it can be exposed.

-2The physicai nature of the ANE’s Is another limitation as to the distance that it can be transported in a pipeline, in the case of a watergel or a slurry type ANE the product is In the form of a saturated solution of oxidizer saits and soluble fuels thickened with a thickener of some sort (normally guar gum) Into which is mixed further quantities of oxidizer salts and (possibly) Insoluble fuels. When pumping such a suspension through a very long line one runs the risk of the solids blocking the line entirely and stopplng the pumping process entireiy. If one were considering dropping or pumping such a suspension through a long vertical (or Inclined) pipe In order to get It underground the risk of the pipeline blocking would be so great as to make this a foolhardy exercise indeed. In the case of an émulsion type ANE these are made by preparing a solution of oxidizer saits In water at an elevated température and then emulsifying this solution Into a fuel phase consisting of oil and emulslfier and then allowing the émulsion to cool down to ambient température. Due to the very small size of the émulsion miceiles the salts are Incapable of recrystallizing. It must be remembered that the fuel phase of the émulsion only makes up about 6% or 7% of the product and that this Is the continuous phase. The oxidizer sait solution makes up In excess of 90% of the émulsion and this is the disperse phase. This means that the cell walls around the oxidizer solution droplets is extremely thln and stretched and that If these cell walls should fait for any reason the oxidizer solution droplets would agglomerate together and once the miceiles get big enough the salts will then start crystallizing out of solution. When this happens the growing crystals start pierdng further mlcelle walls and the émulsion rapldly breaks down and the salts crystallize because they are so far below their crystallization température. When this happens the entire mass solidifies and ceases to be a pumpabie fluid. If one is contemplatlng transporting the émulsion from surface to underground through a long pipeline the risk of the émulsion breaklng down during transportation must be considered and If this happens the pipeline would block completely with severe économie and production conséquences.

Theft is also a major problem both of packaged explosive and of bulk explosives used in the mining industry. Stolen explosives can find their way Into the hands of crimlnals or terroriste and are a major threat to the public.

It Is an object of this invention to address these problems.

SUMMARY OF THE INVENTION

-3According to the présent invention there is provided an aqueous oxidizer solution consisting essentially of a mixture of dissolved oxidizing nitrate salts with less than 25% by mass water, for use in the préparation of explosives formulations, which has a crystallization point of 10°C or less, as low as 5°C or less, even as low 0°C or less, said solution containing:

ammonium nitrate; and caldum nitrate or mixture of caldum nitrate and magnésium nitrate, preferably caldum nitrate;

wherein the molar concentration of ammonium nitrate to caldum nitrate or mixture of caldum nitrate and magnésium nitrate is between 0.5:1 and 1.5:1, more preferably between 0.75:1 and 1.25:1 and most preferably approximately 1; and an alkyiamine nitrate or monoethanolamine nitrate présent in an amount of 1% to 20% by mass.

By crystallization point* is meant the température at which one or more of the dissolved oxidizing salt/s begin to predpitate from the oxidizer solution.

When the solution comprises a mixture of caldum nitrate and magnésium nitrate, the ratio of the molar concentrations of the calcium nitrate to the magnésium nitrate should not be less than about 4:1 and preferably not less than about 4.5:1.

Typically, the oxidizer solution has a water content of between 10% and 25%, between 12% and 24%, preferably between 17% and 22%, by mass.

The alkyiamine nitrate or monoethanolamine nitrate may be présent ln an amount of 1% to 20% by mass, typically in an amount of 10% to 18% by mass, or from 12% to 17% by mass.

For every 1% réduction in the water content below 24%, the solution preferably contains at least an additional 1.67% alkyiamine nitrate or monoethanolamine nitrate in order to retain a low crystallization point for the solution. Put ln another way, the alkyiamine nitrate or monoethanolamine nitrate is preferably présent in at least a quantity to satisfy the équation: M > 5(24-W)/3 (where W = the percentage water in the solution and M = the percentage alkyiamine nitrate or monoethanolamine nitrate in the solution).

-4The alkylamine nitrate may be methylamine nitrate (also called monomethylammonium nitrate), dimethylamine nitrate or trimethyiamine nitrate, preferably methylamine nitrate.

This solution can be used for the manufacture of either a watergel or an émulsion explosives or an ANE. Other nitrates, such as magnésium nitrate, sodium nitrate and potassium nitrate can be Introduced but these must be at molar concentrations significantly lower than the calcium nitrate.

The Invention also covers a method of manufacturing an explosives formulation by mixing the oxidizer solution described above with a fuel.

The Invention further covers an explosives formulation comprising a mixture of the oxidizer solution described above with a fuel.

The fuel may be a hydrocarbon fuel such as diesel fuel, paraffin, oil etc, a water soluble alcohol or polyol (e.g. monoethylene glycol, glycerol, éthanol, methanol, propanol) a water soluble carbohydrate such as sugar. In general if one were maklng a watergel type ANE one might weil choose a water soluble fuel, however immiscible fuels can also be used with great success to make a watergel. If one were maklng an émulsion type ANE then the choice would be for one of the hydrocarbon fuels mentioned above or even recovered lubricating or other oil such as vegetable oil.

DESCRIPTION OF PREFERRED EMBODIMENTS

This patent application daims priority from United Kingdom provisional patent application no. GB 1202402.2, the content of which is incorporated herein by référencé.

I hâve Invented an aqueous oxidizer solution containing a mixture of dissolved oxidizing salts with less than 25% water that does not crystallize below 10°C, and even as low as 0°C or less (as low as -7°C), and that can be used to make a watergel or an émulsion explosive or an ANE (ammonium nitrate émulsion suspension or gel) provided that it meets the following criteria:

) The solution contains less than 25% water;

-52) The solution contains ammonium nitrate (NH₄NO₃) and calcium nitrate (Ca(NO₃)₂) in a molar ratio of ammonium nitrate to calcium nitrate of between 0.5:1 and 1.5:1 and preferably between 0.75:1 and 1.25:1 and most preferably as close to 1:1 as possible; and

3) When the water content of the solution drops below 24%, for every 1% of water removed from the solution one adds at least 1.67% of monomethylammonium nitrate (CH₃NH₃NO₃, also known as methylamine nitrate). Put differently, the content of monomethylammonium nitrate should satisfy the équation: M > 5(24-W)/3 (where W = the percentage water in the solution and M » the percentage monomethylammonium nitrate in the solution).

Since the molecular mass of ammonium nitrate is 80.043 and the molecular mass of calcium nitrate is 164.086, condition 2) can be restated as (for example): The solution contains ammonium nitrate and calcium nitrate in a percentage ratio of calcium nitrate to ammonium nitrate of between 4.1:1 and 1.37:1 and preferably between 2.73:1 and 1.64:1 and ideally as close to 2.05:1 as possible.

If it ls desired one can replace some of the calcium nitrate with magnésium nitrate (i.e. hâve a calcium nitrate/magnesium nitrate mixture), provided that the ratio of the molar concentration of ammonium nitrate to the sum of the molar concentrations of the calcium nitrate and the magnésium nitrate should be between 0.5:1 and 1.5:1 and preferably between 0.75:1 and 1.25:1 and most preferably as close to 1:1 as possible. Furthermore the ratio of the molar concentrations of the calcium nitrate to the magnésium nitrate should not be less than about 4:1 and preferably not less than about 4.5:1. Sodium nitrate and/or potassium nitrate can be introduced as well but In this case, in order to obtain a sub-zero crystallization point, the controlling factor is the ratio of molar concentrations of the ammonium nitrate and the calcium nitrate as well as the relative water and monomethylammonium nitrate percentages and the quantity of sodium or potassium nitrate that can be introduced is determined mainly by their solubility in the available water.

This solution can then be used for manufacturing (among other things) watergel or émulsion explosives or ANE’s. It can be most advantageously easily transportée! underground In deep level mines through relatively small diameter pipelines, using existing access ways and shafts, to the working places at which point it can then be converted into a watergel or émulsion explosive or an ANE.

When using the oxidizer solutions according to the présent invention for making émulsion

-6explosives, it is possible to transport the oxidizer solution and the fuel/emulsifier mixture separately and croate the émulsion at the point of use in such a way that if the explosive is left without being used for more than a few days (for example) then the émulsion would separate and render it nonexplosive due to the Inherentfy unstable nature of any émulsion. This new System can provide a major step forward In the fight against criminal activity and terrorism, since It makes the theft of the explosives unattractive due to the extremely short shelf life of the final explosive. Obviously, since the two components of the émulsion are liquids, there is no practical limit to how far they can be transported in a pipeline and what Is more the pipeline could be of a very small diameter and therefore of very low cost which fs not the case with a normal émulsion type ANE.

In addition the free flowing characteristics of this product is such that pumping through a long hose présents no difficulties whatsoever. In a narrow reef mining situation one could place the pumping unit in a safe location and run a hose from there to the working face. Once the charging up Is complété the miner would wind the hose up and the next day, once the face has been cleaned he would unreel the hose to the new working face and charge up once more. It would probably not be necessary to move the pumping unit more than once per mont h making a huge saving In time and manpower.

The Invention will be described in more detail with référencé to the following non-limiting Examples.

In the Examples described below the solutions were made from 80% monomethylammonium nitrate solution and either solid ammonium nitrate or 88% ammonium nitrate solution as well as agriculture! calcium nitrate manufactured by South African company OMNIA Fertilizer Ltd and sold under the trade name OMNICAL™ which contains about 80% calcium nitrate and about 15% water with the balance being ammonium nitrate. The reason for using this and not chemically pure material is that the standard chemically pure calcium nitrate contains 30.5% water in the form of water of crystallization and by using the agriculture! material I was able to prépare solutions containing high levels of calcium nitrate while still maintalning relatively low levels of water. The mixture was then heated to prépare a clear solution which was then cooled while stirring and the crystallization point was measured and reported as being the point at which the first crystals appeared.

The Invention will now be demonstrated by means of some examples shown in Table 1 below:

-7Table 1:

Mlx number	A1	A2	A3	A4	A5	A6	A7	A8
Ammonium nitrate (AN) (%)	6.6	12.0	16.3	20.0	23.1	25.8	28.1	30.1
Calcium nitrate (CN) (%)	54.4	49.0	44.7	41.0	37.9	35.2	32.9	30.9
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0
Monomethylammonium nitrate (%)	17.0	17.0	17.0	17.0	17.0	17.0	17.0	17.0
Crystallizatîon point (°C)	16	4	-7	-6	3	6	11	14

Mlx number	B1	B2	B3	B4	B5	B6	B7	B8
Ammonium nitrate (AN) (%)	7.0	12.5	17.1	21.0	24.2	27.0	29.5	31.6
Calcium nitrate (CN) (%)	57.0	51.5	46.9	43.0	39.8	37.0	34.5	32.4
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0
Monomethylammonium nitrate (%)	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystaliization point (°C)	6	3	-4	-4	3	8	13	17

Mlx number	C1	C2	C3	C4	C5	C6	C7	C8
Ammonium nitrate (AN) (%)	7.3	13.1	17.9	22.0	25.4	28.3	30.9	33.1
Calcium nitrate (CN) (%)	59.7	53.9	49.1	45.0	41.6	38.7	36.1	33.9
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0
Monomethylammonium nitrate (%)	11.0	11.0	11.0	11.0	11.0	11.0	11.0	11.0
Crystailizafion point (°C)	38.8	20.5	-6	-5	3	9	15	18

These results demonstrate that at constant quantifies of water, even when the water content is relatively high (22%) the crystallizatîon point is well above 0°C when the molar ratio of ammonium

-8nitrate to calcium nitrate is outside the range 0,5:1 to 1.5:1 and is always below 0°C when the molar ratio of ammonium nitrate to calcium nitrate is 1:1.

Table 2:

Mlx number	G1	G2	G3	G4	G5	G6	G7	G8
Ammonium nitrate (AN) (%)	7.3	13.3	18.2	22.3	25.8	28.7	31.3	33.6
Calcium nitrate (CN) (%)	59.5	54.7	49.8	45.7	42.2	39.3	36.7	34.4
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	15.6	15.0	15.0	15.0	15.0	15.0	15.0	15.0
Monomethylammonium nitrate (%)	17.6	17.0	17.0	17.0	17.0	17.0	17.0	17.0
Crystallization point (°C)	27	18	-4	-4	8	19	22	28

Mlx number	H1	H2	H3	H4	H5	H6	H7	H8
Ammonium nitrate (AN) (%)	7.6	13.9	19.0	23.3	26.9	30.0	32.7	35.1
Calcium nitrate (CN) (%)	62.7	57.1	52.0	47.7	44.1	41.0	38.3	35.9
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	15.4	15.0	15.0	15.0	15.0	15.0	15.0	15.0
Monomethylammonium nitrate (%)	14.3	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystallization point (°C)	54.5	37.5	17.6	4	10	18	25	28

Mlx number	J1	J2	J3	J4	J5	J6	J7	J8
Ammonium nitrate (AN) (%)	8.0	14.5	19.8	24.3	28.0	31.3	34.1	36.5
Calcium nitrate (CN) (%)	65.8	59.5	54.2	49.7	46.0	42.7	39.9	37.5
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
Water (%)	15.1	15.0	15.0	15.0	15.0	15.0	15.0	15.0
Monomethylammonium nitrate (%)	11.1	11.0	11.0	11.0	11.0	11.0	11.0	11.0
Crystallization point (°C)	53	48	25	17	9	17	27	32

-9These results show that with solutions having a low water content if the content of monomethylammonium nitrate drops below a certain level the solution, while still having a minimum crystallization point when the molar ratio of ammonium nitrate to calcium nitrate is In the range 0.75:1 to 1.25:1, this minimum is no longer below 0^eC. While a sub-zero crystallization point Is 5 almost certalnly not needed for handling and use underground it is certainly of great benefit during transport to the mine as well as for storage both at the point of manufacture and at the mine. The point is that what has been discovered is a method of minimizing the crystallization point of an oxidizer solution while maintalning relatively low water levels which In tum allows one to produce an explosive at the point of end use which has suffident energy to perform well when breaking rock.

Table 3:

Mlx number	Z1	Z2	Z3
Ammonium nitrate (AN) (%)	26.2	25.6	24.9
Calcium nitrate (CN) (%)	53.8	52.4	51.1
Moles AN/Moles CN	1.00	1.00	1.00
Water (%)	20.0	22.0	24.0
Monomethylammonium nitrate (%)	0	0	0
Crystallization point (°C)	18	11	-3

Here the results show that when the molar ratio of ammonium nitrate to calcium nitrate Is 1:1, if the water content of the solution is 24% or higher no monomethylammonium nitrate Is needed in order 15 to achleve a sub-zero crystallization point.

Table 4:

Mlx number	G4	G4A	G4B	H4
Ammonium nitrate (AN) (%)	22.3	22.6	23.0	23.3
Calcium nitrate (CN) (%)	45.7	46.4	47.0	47.7
Moles AN/Moles CN	1.00	1.00	1.00	1.00
Water (%)	15.0	15.0	15.0	15.0

Monomethyîammonium nitrate (%)	17.0	16.0	15.0	14.0
Crystallization point (°C)	-4	-4	-1	4

These results Indicate that at a water content of 15% if the monomethyîammonium nitrate content is 15% then one can still achieve a sub-zero crystallization point provided that the molar ratio of ammonium nitrate to calcium nitrate is 1:1.

Table 5 below looks at a sériés of results for solutions where the molar ratio of ammonium nitrate (AN) to calcium nitrate (CN) was held at 1:1 while the water content was reduced in 1% steps from 24% to 14% while the monomethyîammonium nitrate (MMAN) content was increased from 0 to 16.67% in steps of 1.67%. ln every single case the crystallization point remained below 0°C.

Table 5:

Mlx number	K1	K2	K3	K4	K5	K6	K8	K9	K10	K11	K1 2
%AN	24. 9	24. 7	24. 5	24. 3	24. 0	23. 8	23.6	23.4	23.2	23.0	22. 7
% CN	51. 1	50. 6	50. 2	49. 7	49. 3	48. 8	48.4	47.9	47.5	47.0	46. 6
Moles AN/Moles CN	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
% Water	24. 0	23. 0	22. 0	21. 0	20. 0	19. 0	18.0	17.0	16.0	15.0	14. 0
% MMAN	0.0 0	1.6 7	3.3 3	5.0 0	6.6 7	8.3 3	10.0 0	11.6 7	13.3 3	15.0 0	16. 67
Crystallizat ion point (°C)	-3	-3	-4	-4	-2	-5	-3	-2	-2	-1	-5

Table 6 below looks at a sériés of results for solutions where the molar ratio of ammonium nitrate

-11 (AN) to calcium nitrate (CN) was once more held at 1:1 while the water content was again reduced in 1% steps from 24% to 14% while the monomethylammonium nitrate (MMAN) content was increased from 0 to 20% in steps of 2%. In every single case the crystallization point remained below 0°C.

Table 6:

Mix number	L1	L2	L3	L4	L5	L6	L7	L8	L9	L10	L11
% AN	24.9	24.6	24.3	23.9	23.6	23.3	23.0	22.6	22.3	22.0	21.6
% CN	51.1	50.4	49.7	49.1	48.4	47.7	47.0	46.4	45.7	45.0	44.4
Moles AN/Moles CN	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
% Water	24.0	23.0	22.0	21.0	20.0	19.0	18.0	17.0	16.0	15.0	14.0
% MMAN	0.0	2.0	4.0	6.0	8.0	10.0	12.0	14.0	16.0	18.0	20.0
Crystallization point (°C)	-6	-6	-5	-7	-6	-6	-5	-6	-6	-5	-4

The above two sets of results show that maintaintng these constant proportions yields remarkably consistent crystallization points.

One can introduce magnésium nitrate into the solution and still maintain a sub-zero crystallization point provided that the molar ratio of calcium nitrate to magnésium nitrate does not drop below about 4.0:1 and preferably that this ratio does not drop below about 4.25:1 and most preferably that this ratio does not drop below 4.5:1 in addition the ratio of the molar concentration of ammonium nitrate to the sum of the molar concentrations of calcium nitrate and magnésium nitrate must be as close to 1:1 as possible.

This is demonstrated in the results shown in Table 7 below where MN refers to magnésium nitrate:

Table 7:

Mix number	N1	N2	N3	N4	N5	N6	N7	N8	N9
% AN	13.5	18.3	22.4	25.8	28.8	18	22.5	25.9	22.5

%CN	45	41.0	37.6	34.7	32.2	39	35.5	32.8	32.9
%MN	9	8.2	7.5	6.9	6.4	10.5	9.6	8.8	12.1
Moles CN/Moles MN	4.5	4.5	4.5	4.5	4.5	3.4	3.4	3.4	2.46
Moles AN/( Moles CN + Moles MN)	0.50	0.75	1.00	1.25	1.50	0.73	1.00	1.25	1.00
Moles AN/Moles CN	0.61	0.92	1.22	1.53	1.83	0.95	1.30	1.62	1.40
% Water	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5
% MMAN	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystallization point (°C)	6	1	-2	11	20	11	7	9	11

In Table 8 below we show results for solutions made with identical quantités of water and MMAN but without the presence on magnésium nitrate.

Table 8:

Mix number	E1	E2	E3	E4	E5	E6	E7	E8
%AN	7.3	13.2	18.1	22.1	25.6	28.5	31.1	33.3
%CN	60.2	54.3	49.4	45.4	41.9	39.0	36.4	34.2
Moles AN/Moles CN	0.25	0.50	0.75	1.00	1.25	1.50	1.75	2.00
% Water	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5
% MMAN	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystallization point (°C)	6	4	-3	-7	7	14	18	22

This demonstrates that with relatively low concentrations of magnésium nitrate, at a molar ratio of calcium nitrate to magnésium nitrate of about 4,5:1 or greater, one can still achieve a sub-zero crystallization point provided that the molar ratio of ammonium nitrate to the sum of calcium and 10 magnésium nitrate Is about 1:1. It Is clear that where there Is magnésium nitrate présent the molar ratio Is between ammonium nitrate and the sum of calcium and magnésium nitrate and not between ammonium nitrate and calcium nitrate alone.

Solutions were then prepared with varying quantifies of sodium nitrate (SN) together with the same

-13quantities of monomethylammonium nitrate and water as those used in mixes A1 to ΑΘ in Table 1 above but now without the calcium nitrate. The results are shown In Table 9 beiow:

Table 9:

MIx number	SN1	SN2	SN3	SN4	SN5	SN6	SN7	SN8	SN9	SN10
%AN	61	59	57	55	53	51	49	47	45	43
%SN	0	2	4	6	8	10	12	14	16	18
Moles AN/Moles SN	-	31.3	15.1	9.7	7.0	5.4	4.3	3.6	3.0	2.5
% Water	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0	22.0
% MMAN	17.0	17.0	17.0	17.0	17.0	17.0	17.0	17.0	17.0	17.0
Crystallization point (°C)	35	33	32	31	30	30	31	30	33	47

This shows clearly that while there Is a slight crystallization point depressing effect with addition of sodium nitrate up to about 16% the effect 1s aimost negligible when compared to the System containing only ammonium nitrate, monomethylammonium nitrate and water, unlike the System when calcium nitrate is used where the crystallization point dépréssion is dramatic when the ratio of 10 the molar concentration of ammonium nitrate to calcium nitrate is close to 1:1.

Solutions were prepared with sodium nitrate (SN) together with calcium nitrate, ammonium nitrate, monomethylammonium nitrate and water. The results are shown In table 10 below.

Table 10:

MIx number	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10
%AN	14.6	20.0	24.6	28.4	31.7	14.2	19.4	23.8	27.5	30.7
%CN	44.9	39.5	34.9	31.1	27.8	47.8	42.6	38.2	34.5	31.3
%SN	8	8	8	8	8	5.5	5.5	5.5	5.5	5.5
Moles AN/Moles CN	0.67	1.04	1.44	1.87	2.34	0.61	0.93	1.28	1.63	2.01
% Water	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5
% MMAN	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0

Crystallization point (°C)

25

19

16

18

20

6

5

-1

9

16

It is clear that in the presence of sodium nitrate as long as the ratio of the molar concentration of ammonium nitrate to calcium nitrate Is in the range specified for the System without sodium nitrate then smai! amounts of sodium nitrate can be introduced, but even at these low levels it has the 5 effect of raising the crystallization point. A similar effect is seen with potassium nitrate as shown in the Table 11a and Table 11 b below*.

Table 11a:

Mlx number	KN1	KN2	KN3	KN4	KN5	KN6	KN7	KN8	KN9	KN10
%AN	14.4	15.5	19.6	24.1	27.8	31.0	14.0	16.4	19.2	23.5
%CN	43.6	42.5	38.4	33.9	30.2	27.0	47.0	44.6	41.8	37.5
% Potassium nitrate	9.5	9.5	9.5	9.5	9.5	9.5	6.5	6.5	6.5	6.5
Moles AN/Moles CN	0.68	0.75	1.05	1.46	1.89	2.35	0.61	0.75	0.94	1.28
% Water	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5
% MMAN	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystallization point (°C)	0	<-6	-4	2	12	21	1	<-6	<-6	-3

Table 11b:

Mlx number	KN11	KN12	KN13	KN14	KN15	KN16	KN17	KN18	KN19
%AN	27.1	30.2	14.0	15.0	17.1	20.6	25.2	29.1	32.5
%CN	33.9	30.8	38.3	37.3	35.2	31.7	27.1	23.3	19.8
% Potassium nitrate	6.5	6.5	15.2	15.2	15.2	15.2	15.2	15.2	15.2
Moles AN/Moles CN	1.64	2.01	0.75	0.82	1.00	1.33	1.91	2.57	3.36
% Water	18.5	16.5	18.5	18.5	18.5	18.5	18.5	18.5	18.5
% MMAN	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0	14.0
Crystallization point (°C)	8	18	12	10	11	20	26	32	36

-15Emulsion products were then prepared from solutions B4 and K3 In order to investigate their effectiveness as an explosive. These two solutions were chosen slnce they both crystallized at -4°C and both contained the same quantity of water but differing quantifies of monomethylammonium nitrate in order to check the effect of the monomethylammonium nitrate on the explosive properties 5 of the resulting émulsion explosive. The final products had the following analyses.

Table 12:

Mlx number	Emulsion B4	Emulsion K3
%AN	18.9%	21.6%
%CN	38.8%	44.2%
% MMAN	12.6%	2.9%
% Water	19.8%	19.4%
PI BSA Emulsifier	1.0%	1.0%
Soya bean oil	5.8%	7.8%
Glass microspheres*	3.1%	3.1%
Oxygen balance	-0.75%	-0.04%
Theoretical net explosive energy	2.874 MJ/kg	2.950 MJ/kg
Product density	1.19 g/cm3	1.19g/cm3

* K20 mlcrospheres made by 3M

The émulsions were each made Into 50mm diameter cartridges, 600mm long, by loading Into plastic lay-flat tubing (100 micron thlck) and initiated with a 15g pentolite booster. Emulsion B4 initiated and detonated over its entire length at constant veiodty as demonstrated by a witness pipe placed in contact with the cartridge which was flattened completely over the full length of the 15 cartridge. Emulsion K3 failed to maintain détonation and most of the product was recovered. This trial indlcates that the monomethylammonium nitrate not only Improves the solubility of the salts at progressive^ lower water levels it also assists in the sensitivity of the final émulsion.

This Invention opens the way to transporting the aqueous oxidizer solution, the oil and emulsifier

-16mixture and the gassing reagent separately to the mine. And then transporting them from surface to the underground workings through reiatively small diameter pipelines, over any desired length, directiy to the face to be blasted and then only mixing the three liqulds (oxidiser solution, oil/emulslfier solution and gassing reagent) to form an explosive émulsion as they are pumped into 5 the hole. It might also be feasible to emulsify the gassing reagent into the oil/emuisifier mixture and

In this way only transport two liqulds underground for mixing at the blast face. The point Is that throughout there would be no need to keep the solution heated In heated storage vessels or heated and jacketed pipelines as would be needed with oxidizer solutions of the prior art.

Claims

1. An aqueous oxidizer solution consisting of a mixture of dissolved oxidizing nitrate salts and water, for use in the préparation of explosives formulations, which has a crystallization point of 10°C or less; said solution consisting of:

between 12% and 24% by mass water;

an alkylamine nitrate or monoethanolamlne nitrate in an amount of 10% to 16% by mass; and ammonium nitrate and calcium nitrate or mixture of calcium nitrate and magnésium nitrate; wherein the molar concentration of ammonium nitrate to calcium nitrate or mixture of calcium nitrate and magnésium nitrate is between 0.75:1 and 1.25:1.

2. The aqueous oxidizer solution claimed in daim 1, wherein the crystallization point is 0°C or iess.

3. The aqueous oxidizer solution daimed in daim 2, wherein the molar concentration of ammonium nitrate to caldum nitrate Is approximately 1.

4. The aqueous oxidizer solution daimed in daim 2, wherein the molar concentration of ammonium nitrate to mixture of caldum nitrate and magnésium nitrate is approximately 1.

5. The aqueous oxidizer solution daimed in daim 4, wherein the ratio of the molar concentration of the caldum nitrate to the magnésium nitrate is not less than about 4:1.

6. The aqueous oxidizer solution daimed in daim 5, wherein the ratio of the molar concentration of the caldum nitrate to the magnésium nitrate Is not iess than about 4.5:1.

7. The aqueous oxidizer solution claimed ln any one of the preceding daims, wherein the aqueous oxidizer solution has a water content of between 17% and 22%, by mass.

8. The aqueous oxidizer solution daimed in any one of the preceding daims, wherein the alkyiamine nitrate or monoethanolamine nitrate is présent In an amount of 12% to 17% by mass.

9. The aqueous oxidizer solution daimed in daim 8, wherein, for every 1% réduction In the water content below 24%, the solution contains at least an additional 1.67% alkyiamine nitrate or monoethanolamine nitrate.

10. The aqueous oxidizer solution daimed ln daim 8, wherein the alkyiamine nitrate or monoethanolamine nitrate is présent in the solution in at least a quantity to satisfy the équation: M > 5(24-W)/3 (where W = the percentage water ln the solution and M = the percentage alkyiamine nitrate or monoethanolamine nitrate in the solution).

11. The aqueous oxidizer solution daimed In any one of the preceding daims, wherein the alkyiamine nitrate Is monomethylamine nitrate, dimethylamine nitrate or trimethylamlne nitrate.

12. The aqueous oxidizer solution daimed ln daim 11, wherein the alkyiamine nitrate is monomethylamine nitrate (CH3NH3NO3).

13. A method of manufacturing an explosives formulation, the method Induding the step of mixing the aqueous oxidizer solution defined ln any one of daims 1 to 12 with a fuel.

14. An explosives formulation comprising a mixture of the oxidizer solution defined in any one of daims 1 to 12 with a fuel.

15. An explosives formulation as claimed In 14, substantialiy as herein described with référencé to any one of the Examples.