BME takes a holistic approach to optimising its blasts to limit dust and fumes.
Though mine blasting may look like a chaotic explosion of rock, the reality is very different. The process is a delicate and highly engineered one that involves balancing factors such as dust, fumes, noise and vibration.
Explosives and dust go hand-in-hand, but the technical experts at BME have blast design down to an exact science to minimise the impact on workers and the surrounding environment.
“It is a given that dust will be generated during blasting,” BME technical manager Hennie Van Niekerk told Safe to Work.
“The goal is to limit the height to which dust particles rise, as well as the distance they travel before falling to the ground.”
Blast design is a key step in the explosive process and takes into consideration factors such as increased stemming length, which is the length of inert material at the top empty part of the blast hole, and minimising explosives’ energy exposure to open air.
By designing blasts to restrict vertical displacement, the likelihood of rocks and dust being ejected high into the air is reduced.
“When rocks are displaced vertically, they tend to break into finer particles that contribute to dust,” Van Niekerk said. “Since dust particles are heavier than air, they will gradually fall back to the earth.
“By limiting the height that dust particles reach during the blast, these particles will remain within the blast zone, thereby reducing dust contamination over a larger area.”
But no matter how well a blast is designed, conditions on the day play a major role in a blast’s outcome.
Van Niekerk said a key question BME technicians ask themselves is, “what needs to be protected from dust pollution?”
“On blast day, wind speed and direction play a major role when initiating a blast,” he said. “The direction and distance to sensitive areas needs to be considered.
“It is essential to avoid blasting when the wind will blow dust towards the sensitive area.”
Some other considerations when looking to minimise dust when using explosives include limiting the size of the blast and reducing the charge per hole by drilling a greater number of smaller holes, providing better explosives distribution.
Ultimately, however, there is a balance that needs to be struck to ensure an optimised blast is achieved.
“There is a trade-off between controlled blasting, optimal blast results, and total drill and blast cost,” Van Niekerk said. “The objective is to find the acceptable balance between the three to satisfy all stakeholders and produce the optimal result.
“The customer need and environmental concerns will be considered during the blast design phase to produce a result that conforms to operational requirements and minimising environmental impact.”
While dust is a key consideration in BME’s designs, NOx (nitrous oxide) fumes are another critical aspect of the blasting process to which the company’s technical experts are particularly attentive.
The release of fumes during blasting in mining operations primarily occurs due to the chemical reactions involved in detonating explosives.
The ideal detonation results in complete combustion, producing relatively harmless gases such as nitrogen, carbon dioxide, and water vapour. However, various factors can lead to incomplete combustion or partial detonation, resulting in the production of these harmful gases.
If the detonation environment lacks sufficient oxygen, not all fuel in the explosive may burn completely, leading to incomplete combustion.
In addition, improper mixing, the condition of the explosive, the method of initiation, temperature and pressure conditions, and varying geology characteristics and rock structures can all contribute to an incomplete combustion.
For BME, the key goal is to eliminate the risk of fumes before the explosion begins.
Typical explosives content includes ammonium nitrate and diesel in its make-up due to these being relatively safe to handle and transport compared to other explosive systems. But ammonium nitrate by itself is not waterproof, with moisture quickly breaking down its chemical composition, leading to a combustion imbalance.
The technical experts at BME developed a solution to this common issue – a dual-salt emulsion system containing ammonium nitrate and calcium nitrate. Together, these salts create an improved water and thermal resistance.
BME international systems and field services manager Tom Dermody said the company’s dual-salt emulsion is a powerful explosive that is less harmful to the environment and worker health.
“These emulsions create a more stable and efficient explosive material,” Dermody told Safe to Work.
“The combination of these salts provides high energy output and improves rock fragmentation during blasting, resulting in superior blast performance.”
Not only does this create a more powerful blast but BME is also able to increase the efficiency of its explosions, with benefits to health and the environment.
“As a dual-salt emulsion system, BME’s explosive is more environmentally friendly and produces fewer toxic by-products due to its efficient detonation properties,” Dermody said. “BME’s dual-salt emulsions offer enhanced performance and increased safety, making them suitable for challenging and diverse environments.”
Combined with BME’s extensive dust suppression measures and condition monitoring, the solution has been making waves in the mining industry.
Whether it is designing blasts down to the smallest of factors or developing solutions to material challenges, BME is helping operators extract the ore they seek while keeping workers and the environment safe.
This feature also appears in the September-October issue of Safe to Work.