Tag Archives: urea

BME promotes the use of dual salt blasting emulsions on ESG grounds

The safety and environmental advantages of dual salt emulsions are gaining more attention from the mining sector as companies pursue more ambitious environmental, social and governance (ESG) goals, according to BME Global Product Manager, Dr Rakhi Pathak.

Pathak says dual salt emulsions have proven themselves as less harmful in terms of potential nitrate contamination and greenhouse gas emissions. At the same time, they can be transported long distances and pumped multiple times before use, while still delivering the improved performance benefits, including high energy in a blast.

Pathak was delivering a technical paper at the 7th Drill & Blast Down Under conference in Queensland, hosted by the Australian chapter of the International Society of Explosives Engineers. She outlined the concept and constituents of emulsion explosives, its advantages over ammonium nitrate-fuel oil (ANFO) and the different types of emulsions.

“In a single salt emulsion, only ammonium nitrate is used, whereas a dual salt emulsion could contain calcium nitrate or sodium nitrate,” she explained. “Urea is an organic compound which is also used in certain applications, such as reactive ground.”

She described methods of determining the quality of an emulsion through microscopy, where large droplets indicate that the emulsion is ageing and showing signs of crystallisation. While ammonium nitrate salt can promote crystallisation, the use of calcium nitrate – which has crystals that are more cubic in shape – can reduce the potential for crystallisation and considerably extend the life of the emulsion.

“Cold emulsion is manufactured at just 65ºC – considerably lower than the 85ºC used for single salt emulsion,” she said. “This has energy-saving benefits as less heat is required.”

The lower temperatures mean that the emulsion does not require much time for cooling before it can be delivered to customers, which provides for an added efficiency benefit in the manufacturing and supply chain processes. Single salt emulsions produced at higher temperatures require extensive cooling periods which limit handling and transportation on demand, according to Dr Pathak.

Dr Rakhi Pathak - BME Global Product Manager
Dr Rakhi Pathak – BME Global Product Manager

Mines are also increasingly concerned about harmful gases that could be emitted during blasts. Dr Pathak highlighted how a careful balance of the oxidiser – the ammonium nitrate and calcium nitrate – and the fuel in an emulsion is necessary to ensure only harmless gases are generated. Where the balance is not optimal, oxides of nitrogen (NOx) fumes can be created. These toxic fumes can affect not just miners, but even communities in the proximity of mines where open-pit blasting is conducted.

“The chemical composition of dual salt emulsions can be easily optimised to minimise the generation of harmful gases,” she said.

Another important benefit of dual salt emulsions was in mitigating the risk of nitrate contamination from explosives. Mining companies have become more sensitive to this, as nitrates can leach into water and land, creating significant compliance risk in terms of mines’ environmental impact. Dual salt emulsions contain much lower levels of nitrate, Dr Pathak explained, reducing any harmful impact on surface or ground water.

Addressing a commonly held belief that single salt emulsions deliver greater energy in a blast, she explored the evidence to show that there was little if any difference between single and double salt emulsions in this respect.

“We studied the data produced by various alternative single salt emulsion systems in the market and found that it was in fact very difficult to compare results – as the software used is not common across users,” she told delegates. “The most effective way to test is in the field, using different suppliers’ products in the same blasting conditions.”

She also spoke about the challenges of blasting in reactive ground, where explosives can degrade in the blast hole or even detonate prematurely. Having only half the ammonium nitrate of a single salt product, she said a dual salt emulsion is more resistant to reactive ground conditions.

“Adding to this resistance is used oil as a fuel agent in emulsion – as well as BME’s specialised emulsifier,” Dr Pathak said. “Using this emulsion with added urea, blasters gain a safe window to load and shoot.”

She noted that the quantity of urea also needs to be determined with scientific accuracy, as too much urea can reduce the energy of a blast. Based on lab testing, she showed that adding 7.5% urea to the emulsion would reduce its energy values by about 6%.

In summary, she explained that the chemical benefits of double salt emulsions included its stability, its resistance to crystallisation, its oxygen balance and its lower risk of nitrate leaching. A useful case study to demonstrate these factors was BME’s shipping of 4,000 t of emulsion to the island of St Helena for use in a major civil engineering project. The emulsion faced up to 10 pumping cycles, extended periods of transportation on road and sea, and varied climatic conditions.

“Even after enduring these conditions, the product performed on site in line with customer expectations,” Dr Pathak concluded. “This showed that a double salt emulsion explosive can enhance the productivity of mining operations, including other sectors, while delivering the environmental benefits that miners are looking for.”

BME’s urea-inhibited bulk emulsion comes to the rescue at zinc mine

When a South African zinc mine experienced a premature detonation in one of its blast holes, BME says it was soon on site to investigate the incident and apply a safe strategy to proceed.

According to BME Technical Services Manager, Deon Pieterse, the cause of the detonation was the reactive ground being drilled for blasting. This was an example of the exothermic chemical reaction that can occur between sulphide-bearing rock and ammonium nitrate-based explosives in the blasthole.

“The mine was found to have geologically-bounded reactive zones within its rich zinc deposits,” Pieterse said. “Due to the natural process of weathering and leaching, the upper benches of the transition zone are more prone to reactivity – as these benches contain more exposed sulphide or sulphide bearing rock and soils.”

He noted that the area being blasted had previously been mined and did not have a history of ground reactivity. Where reactive ground is known to occur, reactive zone mapping of the geology of the mine can be used to mark out potential reactive ground areas in the current and future mining blocks.

“In this case, an unexpected detonation of three holes occurred after the loading process was completed and before blast firing,” he said. “There were no injuries associated with these events.”

The blast block was immediately evacuated and barricaded. For two days, other blast holes showed signs of reaction. This included the emission of smoke and yellow-orange reacted emulsion froth coming out of the blast holes. After signs of reaction ceased, and the pit was declared safe, an in-pit inspection was conducted. Ground samples were collected from the reactive areas and sent for ammonium nitrate and ground-reactivity analysis.

“During our inspection, 35 holes were found to have shown signs of reaction,” Pieterse said. “Other holes were temperature checked with in-hole readings of between 131°C and 170°C at one metre below the hole collar. South Africa National Standards require detonators to function nominally up to 85°C; anything above this increases the possibility of unplanned detonation.”

Ground samples were collected from the reactive areas and sent for testing at the BME’s Losberg laboratory. Here, extreme reactions were observed in two samples of reactive ground that had been loaded with uninhibited bulk ammonium nitrate explosives.

“We monitored the temperature of the samples during testing with a temperature data logger and measured temperatures exceeding 700°C within an hour of mixing the samples,” Pieterse said.

BME was then able to apply its urea-inhibited bulk emulsion – brand named INNOVEX™ RG – which is specially designed for use in reactive ground. Applying the same tests, this inhibited emulsion did not react, or cause any temperature spike.

“We then conducted ongoing characterisation work to understand the reactive ground at the mine,” Pieterse said. “As mining progresses, drill samples are analysed and tested, helping us to build reactive zone maps of the geology.”

In terms of safety practice associated with reactive ground, he explained that mines should conduct a risk assessment where they suspect reactive ground. This should include the monitoring of potential reactive ground indicators. If reactive ground is identified, he outlined a range of controls to manage this risk.

“Mines can use urea-inhibited bulk emulsion, as urea reduces the rate of reaction and slows heat build-up,” Pieterse said. “Blocks should then be kept small enough to be fully charged and fired the same day.”

He noted that, in some instances, holes may need to be sleeved with plastic liners before charging – to isolate the explosives from the blasthole walls. Drill assistants should then keep drill cuttings clear of the blast hole collars, to a radius of at least 0.5 m.

“Drill cuttings that mix in with explosives present a higher risk of rapid temperature build-up,” Pieterse said. “Clearing the hole collars of drill cuttings will prevent activity around the hole collar – such as charging and hole priming – from pushing cuttings back into the hole and onto the explosives column.”

As a rule, personnel on the block must be kept to a minimum during the priming and stemming activities. They should also be careful to check that all explosive and initiation products used to blast reactive ground are compatible; also, each product must be qualified to operate within the temperature range.

“It is important that imported stemming material must be tested to be free of reactive ground,” he said. “Unless stemming can be done rapidly using a stemming truck, blast holes should remain unstemmed.”

He warned, however, that with no stemming in the blast holes, there may be increased air blast and more fly rock from the surface cratering.

“If the holes need to be stemmed, then this must be done just before blasting time – so that all holes remain open for long as possible to release heat,”Pieterse said. “This reduces the risk of hole deflagration and unexpected detonation.”

He highlighted another benefit of having unstemmed holes: they can be observed more easily. For instance, reacting holes may emit visible fumes, in colours of yellow, orange, red and brown. If this occurs, then the blast area should be immediately evacuated and secured, and personnel moved to a safe distance.

This article was first presented as a white paper at the International Society of Explosives Engineers conference. You can download the white paper here.

thyssenkrupp to help build new Uzbekistan chemical complex, Ferkensco says

A new chemical complex aimed at increasing the production of fertilisers in Uzbekistan is to be built, with help from thyssenkrupp Industrial Solutions, lead investor Ferkensco Management Ltd reports.

The construction of the new facility is in line with the Presidential Decree of April 3, 2019 on reforms in the chemical industry and making it more attractive for foreign investment, and The Presidential Decree of February 1, 2019 on the development of cooperation between the Republic of Uzbekistan and Germany, according to Ferkensco.

It is expected that the new complex will be built in the Samarkand region (pictured), on territory owned by JSC Samarkandkimyo, and that potential output at the complex will include ammonium sulphate, urea, melamine and phosphorous-based fertilisers, with the output to be used domestically, but with the option for increased exports.

“The Presidential Initiatives support increased synergies between the oil and gas and agriculture sectors, and the use of a specific quality of domestic gas for fertiliser production,” Ferkensco said, adding: “The petrochemical industry and fertilisers have an important role to play in growing Uzbekistan’s economy in the upcoming years.”

thyssenkrupp wins EPC contract for Egypt fertiliser complex

thyssenkrupp’s plant engineering business says it has won a major order from Egypt chemical and fertiliser manufacturer NCIC (El Nasr Company for Intermediate Chemicals).

The order for the engineering, procurement and construction of the fertiliser complex will see thyssenkrupp realise the project in a consortium with the Egyptian company PETROJET. thyssenkrupp said the order value is in the “mid-three-digit million euro range”.

Marcel Fasswald, CEO of thyssenkrupp Industrial Solutions, said: “We have a particularly successful partnership with Egypt stretching back more than 160 years which offers great potential for the future. Our longstanding experience in plant construction, our strong local presence and close collaboration with our customers form the basis for our success and strong market position in the region.”

Ralf Richmann, CEO Fertilizer & Syngas Technologies, thyssenkrupp Industrial Solutions, said: “To date, we have planned and built 16 of the 17 existing nitrogen fertiliser plants in the country and are delighted that another state-of-the-art plant will now be added.”

The new fertiliser complex will be built in Ain El Sokhna, around 100 km southeast of Cairo, close to the existing NCIC phosphatic and compound fertiliser complex. It is expected to go into operation in 2022 and produce up to 440,000 t of ammonia, 380,000 t of urea and 300,000 t of calcium ammonium nitrate every year.

The new plants are part of NCIC’s plans to expand its current product portfolio to include high-quality nitrogen fertiliser for the local and export markets. Nitrogen is a key nutrient for plant growth and of critical importance for industrial agriculture.