Successfully tackling dust emissions from Callide mine coal trains
Anglo Coal Australia and DuPont (Australia) worked together to reduce dust from the former’s Callide mine in Queensland. Using DuPont’s Dusgon dust suppression agent, dust was reduced by between 50% and 90%.
By Dr Leong Mar, manager, Australia & NZ Technology Centre, DuPont Australia
Ever since trains have been used to transport coal, fugitive dust has been a source of complaints from communities near the rail lines. In Australia, the last 20 to 30 years has also seen suburbia creeping closer towards the mines, rail corridors and shipping ports and the world economic boom of recent years has seen coal production increase significantly. As a consequence, dust complaints from the community have also increased.
In Queensland, almost all coal produced (approximately 180 million tonnes according to 2007-2008 ABARE statistics) is transported by train to ports in the centre and north of the state, or to customer sites. Studies conducted in Canada and USA have shown that up to 3% of the coal load can potentially be lost from the top of open wagons during rail transportation (Cope et al and Canter). Given the total tonnage of coal transported, the potential for dust emissions is enormous.
In recent years, coal producing companies have progressively and successfully sought to recover as much fine coal as possible in an endeavor to maximise resources and profitability.
Figure 1. Rail Loadout at Callide Mine.
This further increases the potential for fugitive dust emissions during transportation.
While fugitive dust emissions are an inevitable consequence for the mining industry, airborne dust poses more than an aesthetic or nuisance problem for workers and nearby communities. It raises a plethora of issues ranging from health, safety and environmental concerns, to increased maintenance costs and down times, to loss of material and productivity as well as factors that affect regulatory compliance and license to operate.
Figure 2. Location of the rail wagon spray system.
Figure 3. Tank for holding the DuPont Dusgon dust suppression product.
In response to increasing community complaints and concerns, government departments and regulators like Environmental Protection Agency (EPA) are putting increasing pressure on mine operators and transporters to address the problem. Since 2007, Queensland Rail (QR) has been investigating the issue of coal dust emissions from trains and identifying potential solutions at the instruction of the Queensland EPA.
Anglo Coal Australia Pty Ltd (ACA), a wholly owned subsidiary of Anglo American Plc, is one of the major coal producers in Queensland with five mines in operation and a further mine in Drayton in New South Wales. ACA’s mines collectively produce more than 17 million tonnes per year.
Like DuPont, ACA places the highest priority on the safety and health of its employees and contractors, and the protection of the environment and communities in which they operate. ACA has also expanded its processing capacity by building and extending coal processing and handling facilities at its Queensland mines, such as the recent completion of the Lake Lindsay project at its Capcoal complex, and improving the recovery of fine coal, especially for metallurgical coal products.
Figure 4 & 5. Rail wagon spray system in action.
ACA is committed to minimising the amount of dust generated from its operations. In a proactive and industry leading initiative, ACA sought a solution to significantly reduce the more visible dust (larger than 10 microns in size) and the not normally visible but more hazardous (10 microns (PM10) or smaller) fugitive coal dust emissions coming from its coal during rail transportation, especially those that pass through populated areas. Its Callide Mine operation was identified as the first candidate for its Rail Dust Suppression Program. Callide is located in the South East Bowen Basin and utilises the QR Moura Rail line which runs through Gladstone. The thermal coal produced from the mines is transported about 120 km by rail to customers in Gladstone.
Coal dust emissions are normally influenced by a number of factors such as: coal type, particle size, moisture content, ambient temperature and humidity and wind speeds. Add to that issues stemming from rail transportation, and this makes the control of dust emissions from trains a complex problem.
The installation of covers over each rail wagon would represent the ultimate solution to dust emissions from the coal load. However, this would be very costly, both in capital and ongoing maintenance and require major operational changes which ultimately would add significantly to the cost of coal.
A simple, viable and cost effective solution to the problem of coal dust emissions during rail transportation is not only the objective of ACA but also of the coal industry in Queensland as a whole.
Figure 6. Watermark on the wagon wall showing the START of the spray treatment
Figure 7. Watermark on the wagon wall showing the end of the spraytreatment
Figure 8. Showing the formation of the 3 dimensional matrix (crust) on the surface of the coal load that binds the coal particles and prevents dust lift off.
The solution: an innovative surface treatment system
With a long successful history of innovations in science and technology and a proven record in particulate material management and dust control technologies, DuPont was a suitable partner for ACA. DuPont has a dust suppression business that provides integrated dust suppression solutions for the mining and construction industries.
The solution was to treat the surface of the coal after it is loaded in the rail wagon with DuPont Dusgon dust suppression agent to create a temporary but robust surface layer in which the smaller particles are bound together in a three dimensional matrix, thereby preventing them from being blown off. Once the three dimensional matrix is set, the surface layer is not further affected by water. This surface layer or crust remains essentially intact throughout the rail journey but disintegrates to become part of the coal when unloaded and does not interfere with the subsequent handling or the properties of the coal in its use.
DuPont, working with its local engineering partner ESS Engineering, designed a rail dust suppression system that was installed at two rail load-outs at the Callide Mine (see Figures 1-3). The system sprays the surface of the coal in every wagon after it is loaded with a Dusgon dust suppression agent, treating it for its journey (see Figures 4-8). The system is fully automated and integrated with the coal loading procedure and takes into account the different types of rolling stock, train loading speeds and other operational factors. The result is a ‘Set and Forget’ system that is seamlessly integrated with the train loading procedure and requires no operator involvement. The system was shown not to have over spraying onto the rolling stock and was approved by QR for use on their rail system.
The system was part of an integrated solution to ACA that covered the design, manufacture, installation and ongoing maintenance of rail wagon dust suppression systems utilizing DuPont Dusgon dust suppression agents. DuPont Dusgon products are proprietary aqueous polymer dispersions which have been specifically developed for mining applications and extensively tested under Australian conditions. They are water based, non hazardous and contain no solvents, salts, heavy metals, corrosives, acids, oils or organochlorides and as such do not create other OH&S or environmental issues.
The result: effective dust suppression system for trains
The DuPont dust suppression system for rail wagons has been installed and operated successfully at two of ACA’s Callide Mine load-outs since January 2008.
The performance of the system was verified by independent environmental consultants who monitored the dust emissions from the coal trains. The dust emissions from treated and untreated trains were monitored in hot and dry months of the year when the conditions are most conducive to excessive dust emissions. A number of qualitative and quantitative methods were used. Visual observations, together with photographs and video footage were taken and clearly showed the surface treatment in the form of a visible crust on the surface of the coal load (see Figure 9) and DUST CONTROL Figure 4 & 5. Rail wagon spray system in action. Figure 6. Watermark on the wagon wall showing the START of the spray treatment. Figure 7. Watermark on the wagon wall showing the end of the spray treatment Figure 8. Showing the formation of the 3 dimensional matrix (crust) on the surface of the coal load that binds the coal particles and prevents dust lift off. Australian Bulk Handling Review: November/December 2009 53 minimal dust emanating from the coal load. This crust was found to maintain its integrity over the 120 km journey into Gladstone with the train reaching speeds of 80km/hr (see Figure 10).
The ambient dust levels before, during and after the train passed different locations along the Moura Line between Callide Mine and Gladstone were measured using ambient air particulate monitors which provide quantitative data on the dust concentrations in the air. The results show that both the TSP and PM10 emissions from the Dusgon treated trains were reduced substantially compared to untreated trains. Depending on the coal properties, moisture content and ambient weather conditions, the average recorded TSP and PM10 was reduced by 50 to 90% for the Dusgon treated trains compared to the untreated trains (see Table 1).
|Near Callide mine||50 to 70% reduction||70 to 80% reduction|
|Entering Gladstone||50 to 90% reduction||50 to 90% reduction|
Table 1. Results showing the range of reductions in average TSP and PM10 readings obtained from the Dusgon treated trains compared to the untreated trains.
This represents a significant improvement in the amount of coal dust coming off the rail wagons and into the atmosphere during transportation. The results also showed that the product performed, irrespective of coal properties, particle size, moisture content and ambient weather conditions.
There have been no reports of any adverse effects on the coal handling or use by ACA’s customers further confirming that while the treatment has effectively reduced the amount of coal dust emissions from the trains, there are no adverse side effects to this process. There has also been positive feedback from the operators and community on the reduction in dust emissions from the trains.
Figure 9. Picture of moving coal train showing intact crust and minimal dust emissions.
Figure 10. Picture of the coal surface towards the end of its journey showing still intact crust.
This project demonstrates an innovative solution to the age old problem of coal dust emissions during transportation. The solution is simple to implement, cost effective and proven to be effective in significantly reducing the fugitive coal dust emissions and potential impact of coal dust on communities and the environment, while at the same time allowing coal producers to maximise the potential of their coal resources.
Based on the success of this program ACA will be looking to extend the rail dust suppression program to other Anglo Coal mines in Central QLD and in other regions.
Cope, D.L. and Kamal K. Bhattacharyya. A Study of Fugitive Coal Dust Emissions In Canada (November 2001) For The Canadian Council of Ministers of the Environment.
Contact: Leong Mar – email – Leong.Mar@aus.dupont.com