Friday 25th Sep, 2020

Water on dust control is water lost

Reducing water use has both economic and environmental benefits, which is why Perth-based company Rainstorm has made its mission to fight water waste in dust control.

Reducing water use has both economic and environmental benefits, which is why Perth-based company Rainstorm has made its mission to fight water waste in dust control.

Australia is the driest inhabited continent on the planet, suffering through a number of protracted droughts and water restrictions.

On top of water’s role for sustaining life, it is also used in a number of heavy industry applications. One such role is in dust suppression systems to ensure workers and the nearby environment aren’t harmed by hazards in the air.

However, Mason Trouchet, Group Technical Sales and Marketing Manager at Rainstorm Dust Control argues that every drop of water spent on dust control is a drop of water lost.

“I am a firm believer in effective dust control treatments to conserve water and improve health and safety measures, especially for large-scale mining applications,” he says.

Trouchet is part of the product development team for Rainstorm and is involved in establishing dust control services and procurement technology transfer in international markets.

He adds that recent advancements in dust monitoring and modelling are transforming Rainstorm’s clients’ ability to implement effective control measures.

One such system is the Point of Dust Extinction or PDX. PDX is the result of more than 25 years of research into non-standard ore and soil stabilising agents, developed by combining surfactant wetting agent formulations with novel, biological-based (rather than chemical), active ingredients. This highly-concentrated liquid biochemical is biodegradeable and non-toxic.

It aids wettability and friability, helping lower ultra-fine ore dust extinction moisture (DEM) and improving material handling of ore movements. When added into the mining ore stream, PDX significantly reduces dust, lowers the water levels required for DEM and minimises the environmental impact in comparison with petroleum-based water extenders.

How it works

PDX is made up of three components: Dispersants, trace elements and organic compounds. Dispersants in PDX help reduce the surface tension of water and promotes the uniform transmission of moisture throughout the ore. Water adhered to the fine particles is released, which can result in a significant reduction in the volume of water required for DEM.

Trace elements in PDX assist ionic exchange reactions between fine particles in the ore. Ionic bonds are formed as a result of the attraction between oppositely-charged ions and ionic exchange is the capacity of ions to exchange with other ions which have a smaller charge net. In addition, much of the adsorbed water at the interface of the clay particles is altered to improve moisture-to-surface-area wetting ability for the long term.

Organic compounds in PDX serve primarily to modify excess ion exchange points in the ore lattice and alter the behaviour of adsorbed water.

PDX is more effective when added to an ore body early in the materials handling process, with immediate chemical changes to fine particles becoming apparent. Mechanical mixing through the material handling process creates a uniform moisture content within the ore, minimising the amount of additional water required in the process stream.

It also generates permanent physical and chemical changes in ore without affecting downstream processing.

Rainstorm recommends injecting PDX alongside deluge water sprays at bin loading areas, at the primary and secondary crushers and at transfer points.

PDX is only effective on the fines components of the ore, with application rates capable of being finetuned to suit fines and lump ratios. An application rate of one litre of PDX for 10 to 25 tonnes of ore fines is recommended, depending on the site conditions.

Bulk supply of the product is available throughout Australia, with an extensive distribution network in the Pilbara, Western Australia, currently in place.

Fighting dust with fog

Rainstorm also helps reduce dust emissions through fog systems, which deliver a smaller water particle under pressure to match the dust particle’s size. The dust particles increase in molecule weight, meaning it drops to the ground faster using less water and without affecting the ore’s moisture content.

Fog systems come in modular size power packs for industrial applications in mining and shiploading activities. Positive displacement pumps deliver the fog through a multi-line manifold system along a flexible high-pressure hose close to the source of dust. Adjustments to pressure can fine tune the fog to match the required conditions and lines can be attached via a cable extension close to the dust generation area, minimising the impact from air velocity.

Defeating dust

Rainstorm has been in operation in Australia for more than 29 years and has since become a major player in the dust control space.

Trouchet says data has driven the development of new innovations in dust control, along with strategic partnerships.

An example of this can be seen in Rainstorm’s partnership with Pressure Wave Systems (PWS), which has developed a way of tackling the difficult problem of dust being generated by blasting.

The solution was to replace rock stem with a specialised Stem Gel LR2, which provides major containment impacts on blasting efficiency. Pressure waves contained in the rock help bring about greater fragmentation and a number of downstream benefits.

“The subsequent benefit of that powerful containment is a sizeable reduction in noise and dust,” Trouchet says.

“As the gel is expressed from the blast and becomes airborne, dust particles flocculate in mid-air and fall to the ground.

“In the past, drill and blast technologies have focused on explosives, detonation timing hole stability and moisture. Very little attention has been given to containment. It’s that unique characteristic of Stem Gel to measurably reduce noise and dust output from blasting that makes it such a massive game-changer.”