Green Explosives | No Nitrate Explosives | AN-Free Industrial Explosives For Rock Blasting

AIM OF THE PROJECT:

One of the top motivations for the development of NoNitrateExplosives (NoNEx) has been the elimination of NOx gas. By removing all nitrate sources in the NoNEx, no nitrous gasses can be formed in the post-blast fumes.

The detonation process has been studied for ideal explosives and the reaction zone length has been measured. However, for non-ideal explosives, that type of information is not available. Therefore, the primary aim of this work was to capture the thermodynamic properties of some non-ideal explosives through the use of a thermodynamic simulation model.

The non-ideal explosives taken into consideration are (a) Site Mix Emulsion SME, (b) Site Mix Slurry SMS, (c) small and large diameter emulsion explosives, and (d) small and large diameter water gel slurry explosives.

As part of a project to develop alternative explosive formulations, it was decided to investigate the thermodynamic parameters of these new AN-free explosive mixtures (NoNEx) that use an oxidizer instead of AN as the oxidizer. The thermodynamic parameters of these mixtures were quantified by a simulation model.

In addition to observations of the thermodynamic parameters, the regression equation obtained from lead block values is another interesting characteristic observed and analyzed.

NoNEx EASES & CHALLENGES:

The NoNEx gel/emulsion formulation is easy to prepare oxygen balanced because it is homogenous except for hot spots.

The formulation can be done even oxygen positive to minimize CO formation without the risk of getting additional toxic detonation gases because there is no nitrogen. In AN-based explosives, positive oxygen balance leads to the formation of NOx.

Sensitization of NoNEx gel needs to be done with gas voids or microspheres.

Hot spot sensitization defines the density range of the product.

According to VOD and sensitivity test results, the upper limit for the density range of the used formulation is 1.16 g/cm3.

The hydrostatic pressure of the explosive column itself will press the gassed product into the density of 1.16 g/cm3 in an approximately 20 m vertical borehole if the free density is 1.0 g/cm3.

The work (theoretical, mostly) so far has demonstrated that based on technical properties such as energy, gas volume, and VOD, NoNEx explosive has the potential of becoming a nitrogen-free alternative to AN-based products on the market.

The open questions regarding chemical stability and resistance to water do not give higher expectations than on-site manufactured load and shoot products. Increased sleep time is a task for further development.

Strong emphasis must be put on safety at every step of development. Field test results will eventually show if the product and loading method fulfill requirements for safe use and are economically and technically feasible.

THE OXIDIZER(S) IN NoNEx:

As of now, one of the oxidizers for NoNEx is already in use in Sweden. The oxidizer also is used as a rocket mono-propellant oxidizer in the aerospace industry. So, its application in the field of industrial explosives is only an extension of the proven track elsewhere.

This oxidizer is a crystalline solid at low temperatures. It is used in the textiles, wood pulp, paper industry; plasticizers; rocket fuel; foam rubber; glycerol; electroplating; antiseptic; laboratory reagent; epoxidation; hydroxylation; oxidation and reduction; viscosity control for starch and cellulose derivatives; refining and cleaning metals; bleaching and oxidizing agent in foods; neutralizing agent in wine distillation; seed disinfectant; substitute for chlorine in water and sewage treatment.

However, we have found out its use in the novel formulations of base high explosives for use in mining as a kind of industrial “green explosive”.

The authors explain the facts and dispel some of the myths concerning both the medium and the potentially explosive mixtures based on it. The method of preparation and safe handling of this oxidizer is briefly presented and advocated by some of the experimental and literature examples. Such papers contain both historical and modern approaches to undergoing detonation.

The safety concerns, especially those related to their potential explosiveness during preparation, handling, or utilization are analyzed as well.

The potential of the medium as a “green” and easy-to-handle oxidizing compound that may replace ammonium nitrate in a variety of emulsion and blended ANFO-emulsion commercial explosives that currently constitute the majority of explosives used in the mining industry, is underlined.

Mining explosives based on ammonium nitrate are safe and effective; however, the risk of NOx fume production during blasting is still present. In 2013, a project to eliminate NOx fumes from blasting began and this oxidizer was chosen to replace ammonium nitrate as the oxidizer. Previous work in this area demonstrated that “this + selective fuel mixtures” were able to detonate.

A comprehensive study was conducted to determine the detonation properties of NoNEx that used this oxidizer at lower concentrations (below 50 wt.%), detonated in unconfined conditions, and used void sensitization to achieve an efficient detonation reaction.

The results indicate that the mixtures can achieve a different VOD which depends on the size of the sensitizing voids and more importantly, the mixtures behave as non-ideal explosives, similar to ammonium nitrate-based explosives, but with the advantage of being NOx-free explosives.

In an attempt to eliminate ammonium nitrate from explosives formulations, the initial work identified calcium ammonium nitrate (CAN), and sodium nitrate (SN). Then came the present new oxidizer into the picture.

Although more studies need to be conducted to fully understand these explosives, if successful, these explosives would be able to offer an alternative to the AN-based explosives in the mining industry.

CASE STUDIES

In one of the practical application studies for one of the NoNEx, instrumented detonation trials were conducted at the Mining Blast chamber, Pinjarra Hills, and the RUREX testing range.?The detonation trials, conducted over 12 months, have characterized the sleep-time formula and summarized in this report are:

????Detonation performance over a variety of densities;

????Detonation performance at surface mine-site blast hole diameter (~240mm);

????29-day product sleep-time and detonation;

????Prevention of auto-sensitisation over 22 days, and denial of detonation functionality in unsensitised material;

????Theoretical modeling of the explosive performance of varying Oxygen Balance (OB) formulations;

????Laboratory density stability tests of numerous formulations;

????Thermal stability tests (UN test Series 3 (c)) of a water-diluted oxidizer formula.

A review of the published article titled – Green explosives solutions for the sustainable mining, constructions, and civil explosives industries – talks about products of NoNEx. NoNEx is a nitrate-free emulsion explosive developed for use in civil underground and surface mining and construction rock blasting operations.

By replacing nitrate-based explosives with NoNEx significant savings in ventilation and water treatment infrastructure may be achieved in combination with improved production cycles. Further, tremendous CO2?emission savings can be achieved by migrating to NoNEx.

The NoNEx technology and product have been developed and extensively tested by a competent team based in Stockholm Sweden. Testing has been done in partnership with strong mining, chemical, and production partners.

The NoNEx emulsion may be pumped and charged using similar or identical procedures used for AN-based emulsions (i.e. bulk loading using a charging hose with chemical, delayed, in-situ sensitization) in identical or very similar drill patterns commonly used in the underground or surface extractive industries.

Similarly, to the status quo, NoNEx emulsion is fully waterproof and is not an explosive until sensitization is achieved. This can be achieved either by the mechanical addition of micro balloons or by chemical sensitization. This allows for a wide array of?in situ?(in-hole) densities and sensitivity ranges.

Production can be done in a cold emulsification process, functional down to +5 °C, and does not exhibit any crystallization issues.

The emulsion is stable in moderate temperatures for significant periods and is comparable, or better, to AN-based emulsions in detonation speeds, fragmentation, and texture.

CONCLUSION FOR THIS ARTICLE:

The present note is for general information and awareness. We have the complete set of exhaustive information on (a) technology, (b) lab batch manufacturing, (c) HAZOP, (d) HIRA, (e) availability of materials IN India, (f) SOP, and other relevant details.