This article by Lee Gailer, RST Solutions, was first published in World Coal, Issue 1 2025. Republished with permission of the publisher.
Lee Gailer, RST Solutions, Australia, reveals the benefits of reducing water consumption with advanced spray and foaming systems.
As the global concern over water sustainability increases, mining companies are being called upon to take more responsibility in managing their environmental impact when it comes to dust control.
The use of water sprays to control dust is preferred in many mining environments, as it is highly effective and more economical, and with implementation is usually faster and more straightforward.
However, using only water for dust suppression activities is not always effective nor viable. Constant reapplication of water to suppress dust can lead to erosion and sediment issues, water wastage, and potentially pose health risks to workers each time the water evaporates and requires reapplication.
Water on its own evaporates fast, leaving dust particles loose again with constant reapplications needed. When water is sprayed to control dust, it can flow over the surface, disrupting aggregates and dispersing them in the flow.
Adding a surface active agent (surfactant) or wetting agent to the water used in spray systems offers both short and long-term solutions, and is more effective when the chemistry is designed to be compatible with materials being mined or moved. Using the right type of spray system will further increase effectiveness.
A wetting agent changes the characteristics of water for greater penetration, saturation, and coverage, reducing water usage by up to 50% and gaining as much as twice the penetration rates. Numerous field tests have shown that, when used at the correct doses and applied through the correct spray system, a wetting agent significantly reduces the amount of water required to achieve higher levels of dust control than water alone.
Latest technologies currently being trialled in Australia include an advanced polymer additive designed by fine particle specialist RST Solutions, called Total Fines Control. Applied to bulk material by spray at transfer points along any stage of the supply chain, the polymer additive is mixed into the material to increase water holding capacity for easier, longer-term dust control.
RST Solutions foaming solution applied in a chute.
The benefits of improving water with a wetting agent
- Improves wetting characteristics of water, allowing it to penetrate, saturate, and spread faster than plain water.
- Increases dust extinction moisture (DEM) levels.
- Improves dust suppression capabilities.
- Reduces the amount of water required.
- Increases water flow through minerals and ore.
Further benefits of using an advanced polymer additive
- Improves water holding capabilities.
- Requires only one application to bulk material.
- Easily applied through water sprays at transfer points at any stage of the supply chain.
- Remains active throughout storage and transportation.
- Easy and quick reactivation with a light spray of water.
Maintaining product quality
The challenge for a dust suppressant is to remain active in the material as it is being moved down the supply chain without altering the product’s chemistry, devaluing quality, and undermining end user processes.
With spray and foaming systems being the most common methods for suppressing mineral dust, companies along the material supply chain are being urged not to boost the dosage levels of surface active agents (surfactants) commonly used in these applications.
While regular dust control formulas contain chemical elements considered low enough at application strength to not cause any problems, increasing the amount applied to meet strict dust exposure limits can cause an adverse chemical reaction during processing and manufacturing.
Issues have also been raised about overwatering to suppress dust having a negative effect on the quality of material, with saturation and overweight issues at delivery.
Chemistry for water treatments should be tailored to suit specific mined material and be compatible with downstream processes, as well as dust control methods along the whole material supply chain, to provide a higher level of product quality and efficiency.
The advanced polymer additive being developed by RST Solutions aims to achieve these goals. Currently in the final stages of field testing, the polymer additive, called Total Fines Control, is mixed into water at specific doses and sprayed onto mined material as it is being transferred. By mixing into the bulk of the material, moisture holds for longer, with only one application needed, which can be reactivated with a light spray of water.
With the pressure on companies that mine, transport, and store coal to meet rigorous dust exposure standards, while continuing to supply high grade coal to steel manufacturers, RST Solutions is helping the industry achieve best practices in fine particle management.
Compatibility is critical
While reducing dust levels is a high priority, RST Solutions explains to companies the importance of making sure the dust control solutions they are using are compatible with the specific type of material being mined, dust control application systems being used, and the intended manufacturing processes.
For example, surfactants used in dust control water sprays contain levels of sulfur, sodium, and potassium, that, if accelerated, can alter a mineral’s chemistry. This can reduce product quality and undermine end-user processes. Elevated levels of these chemical elements can reduce the quality of coal to the point it is considered lower grade coal, unsuitable for steel manufacturing.
Maintaining product quality and compatibility with end-user expectations and processes, while increasing dust control levels, requires a depth of knowledge of mineralogy, processing, manufacturing, and chemistry to develop effective and cost-efficient dust suppression systems.
The best way to ensure optimal dust control in the short and long term is to work with an expert in all facets of spray and chemical technology, as there are many factors that can have a significant impact on performance.
Advanced spray systems for dust control
The type of spray system used for dust suppression is a major factor. These vary depending on the operation, from water carts and sprinkler irrigation sprays used at the dig face, to spray bars at transfer points, and fog cannons and misters to manage the dust underground.
Spray nozzle systems utilise fine water droplets, binding with the dust particles to form larger agglomerations that stop travelling in the air.
A wider nozzle of 2 mm should be implemented to reduce the opportunity for blockage, and air flow through the enclosure needs to be moderate.
If excessive air flows are present (air velocity greater than 1 m/sec.), both the dust and the water droplets will be carried out before bonding can take place.
Air control measures need to be implemented, with a highly concentrated wetting agent added to water at ultra-low dosage rates, to allow it to penetrate, saturate, and spread much faster than water on its own, improving wetting performance characteristics and overall performance.
RST Solutions dust suppression spray ring
Spray bars and rings: the right mounting and positioning
Advanced airborne dust suppression spray systems use spray bars and rings placed as close to the beginning of transfer points as possible.
Spray nozzles are generally placed at the end of transfer points, so the material load can settle and be in position, hence the spray is above the material and not on it.
However, advanced airborne dust suppression systems treat the air around the material rather than the material itself, and are more effective when the spray nozzles are positioned at the beginning of transfer points.
The force of the moving material helps the water penetrate the material as it moves through the transfer point.
Operating pressure
The ideal operating pressure is dependent on many application-specific variables, including nozzle spacing, boom height, spray quality, and total application volume.
Basic principles for selecting a level of pressure:
- Increasing pressure decreases droplet size.
- High pressure sprays are better suited for enclosed areas.
- Nozzles operating at higher pressures should be placed close to the dust source to minimise the amount of air set in motion along the spray path.
RST Solutions says the choice of spray nozzle is a major factor.
Advantages of using a foam dust suppression system
The use of a foam dust suppression system is increasingly recognised as being highly efficient for crushing operations, with several key advantages over alternative dust control systems such as extraction systems, water/surfactant spray systems, and fogging or misting systems.
Foam suppression systems with an advanced water treatment typically use up to 10 times less moisture than water-only systems. Used mostly in chutes, the foam provides greater dust control of fugitive dust emissions.
A mechanical foaming dust suppression system dispenses a solution through the controlled mixing of compressed air, water, and a foaming treatment. Large nozzle openings minimise blockages and contain liquid dispersion to the area required for treatment.
When the foam solution is applied through the foaming system, a robust, flowable foam that engulfs all the material and fine particles creates a ‘total dust blanket’ effect that prevents dust from becoming airborne.
Once treated, the dust remains with the material and should not release at subsequent transfer points, screens, stack outs, or load outs. A light spray of water is all that is required to reactivate the dust suppressant agent at a later stage.
Correct dosing
Quality wetting agents, surfactants, and foaming agents should need only low dosage rates and can be controlled with a small industrial metred dosing pump to achieve accurate dosing of wetting agents and other additives.
Dosage levels will need to be adjusted to suit site specific conditions (varying water types, pressures, and volumes) and correct dosing reduces buildup of calcium scale and grime to pipes and nozzles. If storage tanks are used, the additives can be directly dosed into water storage tanks.
Holistic approach to dust control
A holistic approach to dust control needs to be undertaken to solve a whole range of issues, many of which are unique to individual mine sites.
Material handling produces excessive fine particles across mining operations, from the mining processes through to haulage, storage, and transfer stations.
Fine particles become dust when dry, sediment or mud when wet, and are responsible for a wide variety of challenges. Excessive water use for dust control activities can be problematic, causing swelling and shrinkage issues, excess weight, and material handling issues such as stickiness.
Spray system applying a dust control treatment to coal at a processing plant
No matter where on the mining material supply chain, dust is a major concern. Without proper targeted treatment, resources required to control dust can significantly increase, wasting water and money.
Operational challenges and environmental conditions are different for every mine site, and it is highly recommended that spray and foaming equipment and compatible water treatments are tailored to meet specific requirements and mechanical devices for product application.
Material type, water quality, application equipment and processes, climatic conditions, among other unique factors should be heavily considered when planning an application system and water treatment for dust control.
Environmental managers at mine sites also need to take into account an operations’ key performance indexes, project site conditions, EPA regulations, and health and safety when deciding on a solution.
Growing level of commitment
Global fine particle specialist RST Solutions has observed that mining operations are showing a growing level of commitment to dust and erosion control activities.
Based in Australia, RST Solutions works with companies around the world seeking more project optimisation strategies on a range of raw material projects, from solutions for dust control at mine sites and throughout the supply chain, to haul road construction and agricultural operations.
Taking into consideration materials being mined or used on site, a project’s operation processes, application equipment and systems, budget perimeters, and local weather patterns, RST Solutions draws on 30 years specialising in the field of fine particulate matter to provide advanced solutions and mechanical application equipment tailored specifically for a project.