Oxidizer solution

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

BACKGROUND OF THE INVENTION[0001]In most countries where bulk explosives are used they fall in a category defined in the United Nations Handbook on the Transportation of Dangerous Goods as ammonium nitrate emulsions 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 in the form of emulsions or watergels (or slurries). Because they are not classified as explosives the regulations regarding transportation and storage are considerably less stringent than they would be if they were classified 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 pumping process.[0002]One of the problems with existing bulk explosives formulations (whether they are of the watergel or emulsion type) are that they are extremely viscous fluids and are difficult to pump or tra...

AI Technical Summary

Benefits of technology

The present invention provides an aqueous oxidizer solution containing a mixture of dissolved oxidizing salts, which has a low crystallization point and can be used in the preparation of explosives formulations. The solution has a water content of 25% or less, and contains ammonium nitrate, calcium nitrate or a mixture of calcium nitrate and magnesium nitrate. The molar concentration of ammonium nitrate to calcium nitrate or magnesium nitrate is between 0.25:1 and 2:1. The solution has a crystallization point of below 30°C, preferably below 25°C, and even more preferably below 10°C or 0°C. The ratio of the molar concentrations of calcium nitrate to magnesium nitrate should not be less than about 4:1. The solution can be used for the manufacture of watergel, emulsion or ANE explosives formulations, which can be used with various fuels such as diesel fuel, paraffin, oil, water soluble alcohols or polyols, water soluble carbohydrates, or even recovered lubricating or other oil.

Problems solved by technology

One of the problems with existing bulk explosives formulations (whether they are of the watergel or emulsion type) are that they are extremely viscous fluids and are difficult to pump or transport in pipelines over long distances.

A second problem is the problem 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.

Here again the viscosity is a problem as there is a finite limit 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.

The physical nature of the ANE's is another limitation as to the distance that it can be transported in a pipeline.

When pumping such a suspension through a very long line one runs the risk of the solids blocking the line entirely and stopping the pumping process entirely.

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.

Due to the very small size of the emulsion micelles the salts are incapable of recrystallizing.

This means that the cell walls around the oxidizer solution droplets is extremely thin and stretched and that if these cell walls should fail for any reason the oxidizer solution droplets would agglomerate together and once the micelles get big enough the salts will then start crystallizing out of solution.

If one is contemplating transporting the emulsion from surface to underground through a long pipeline the risk of the emulsion breaking down during transportation must be considered and if this happens the pipeline would block completely with severe economic and production consequences.

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 criminals or terrorists and are a major threat to the public.