Tackling dust from coal and iron ore trains
Communities are up in arms over dust from coal and iron ore trains. In turn, miners and rail companies are turning to solutions such as chemical dust suppressants. But questions remain over who should foot the bill. Charles Macdonald reports.
Across Australia, dust from trains carrying coal and iron ore is a persistent problem. For residents next to a rail track in the Bowen Basin or Hunter Valley it can, on the worst days, mean dust obscuring windows, dirtying washing and penetrating homes, while in the Pilbara some towns are literally coated red with dust.
The problem has received most attention in Queensland. There, the Department of Environment and Resource Management (DERM) issued an environmental evaluation notice to QR in July 2007. It asked the rail operator to investigate coal dust coming from wagons on the Goonyella, Blackwater and Moura networks, and to come up with solutions.
For QR, dust has been an issue for the organization since it first hauled coal in the early sixties. However, it was in the 1990’s as tightening environmental regulations gave voice to consumer complaints that the company stepped up its efforts to manage the issue.
Amongst other mitigation measures, it planted trees and grass, built fences, improved drainage and graded formations in different ways. It also looked at ways to better empty and profile coal wagons. More recently, following DERM’s notice, the company’s Coal Loss Management Project marked the start in 2007 of some serious research into dust, its causes, and possible mitigation measures.
Connell Hatch, on behalf of QR, calculated “total suspended particulates” from QR’s central Queensland systems, which carry around 160mtpa, at 0.0035% or around 5,600 tonnes. Estimates of broader coal loss and dust on QR’s network by other organizations vary widely, with DuPont (Australia) putting it as high as 3%, or an enormous 4.8 million tonnes per annum.
In a bid to add some objectivity to the debate, QR is currently installing opacity meters beside points on its rail network. These devices measure the amount of light going through the air, and will allow scientists to make calculations about the number of particles in the air, on both a background basis and when a coal train is passing the device.
“We’ll have some objective data about how much dust there is at these particular sites,” said Ian Dall, group general manager, QR Network Coal Systems.
One meter is up and running at Marmoor between Rockhampton and Gladstone on the Blackwater system, with another at Schillings Lane, just west of Gladstone on the Moura system. A third is planned for Mindi, west of Mackay, on the Goonyella system. QR expects to start releasing some data on its findings by mid-2010.
Besides quantifying the problem, QR’s Coal Loss Management Project researched the use of dust suppressing chemicals or veneers on dust emanating from the top of coal wagons. This involves the treatment of the coal surface in rail wagons with a chemical which effectively forms a spiders-web or crust over the coal surface, minimizing coal dust over the journey to the end customer.
The company used John Planner of Introspec Consulting to test chemicals from a number of suppliers. After being inundated with products, the studies, involving wind tunnel testing of samples, resulted in six products being endorsed by QR as being up to 75% effective in reducing coal dust.
The list of approved suppliers included Nalco, Applied Australia, Du Pont Australia, Cooee Products, Manildra Group, Polo Citrus Australia, RST – Dust Earth Water Solutions and Vital Chemical.
Chemical suppressants vary widely in their composition. Several suppliers use polymer-based formulae, while others use a starch-based product, and others tout green products with mystery natural glues. Nearly all products are diluted with water, the degree of dilution, and hence demand for scarce and expensive water, becoming another battleground for suppliers.
Crucially, the suppressants must not alter the burning properties of coal in subsequent applications, and any toxicity would be hazardous for workers and the environment. Manufacturers also vary their formulae to suit the particular characteristics of individual coals and ores.
“QR thinks that veneering is the best way to deal with dust from coal on top of wagons,” said Ian Dall, suggesting that an alternative, such as fitting lids to coal wagons, would be impractical and prohibitively expensive.
So far, QR has spent $4m on research in the dust area with more to come. Of 40 mines in Queensland, it has identified 14 dusty coal mine sites which are priorities for introducing veneering spray stations. Evidence so far suggests that it is the unwashed thermal coals that are the dustiest. QR is now crafting a dust management plan which DERM required it to produce by early 2010.
Currently, despite extensive research and trials by rail and mining companies, there are still only three fully-fledged installations of commercially-operated dust suppression systems at mines in Australia. Two of these are on the main rail heads of the Callide mine operated by Anglo Coal, where systems supplied by Dupont were installed at the start of 2008. The other is at the Ensham mine.
QR hopes to have spray stations in place at the 14 dusty coal mine sites “in the next 12 to 24 months” with five in the year following. The company estimates the capital cost of setting up a spraying station at between $65,000 and $100,000, and the ongoing cost of chemicals at between 2 and 4 cents per tonne plus “associated costs”. Water costs for mines in the drier and more distant westerly areas are likely to be significant.
With DERM putting on pressure, QR and the mining industry, via the Queensland Resources Council (QRC), are currently compared to those in Queensland which have a larger surface area at the top of the wagon.
Elsewhere, coal dust is an expensive problem for QR in terms of fouling of ballast and damage to clips on sleepers, signals and switching points.
“Coal fouling reduces the re-ballasting cycle from a normal 12 to 15 years down to around six years,” said Mr Dall. “As a result, we have to do around 100 kilometres of coal foul removal every year from our 1700kms of track.”
This costs QR around $30m directly per year, with derailments and delays further crimping export volumes and income.
Turning to iron ore, the Pilbara’s sparse population, of around 41,000 across a vast area, makes dust emissions from iron ore trains less of a contentious issue than in the comparatively densely populated Bowen Basin in Queensland. Conversely, far longer rail hauls – of 400kms versus 150kms in Queensland – and hotter, drier conditions create the potential for more dust.
Major companies like Rio Tinto, sensitive to their image and keen to act as good corporate citizens, are moving on the issue. Rio Tinto has formed a committee to examine dust control issues and add some scientific rigour to the dust control issue. The committee commissions consultants to do testwork – including wind tunnel studies – on different ore types and veneers.
“If testwork is done but not all the results are collected, then the testwork has effectively been wasted,” said John Visser, principal advisor – process, technology and innovation, Rio Tinto.
Currently, Rio Tinto is trialing dust suppression on ore trains at West Angeles, with either Tom Price or Brockman next to follow.
“In 2010 we hope that dusty trains will become a thing of the past on the Rio Tinto line,” said John Visser. Generally, more effective management of moisture at Pilbara mine sites has seen a marked drop in dust from iron ore trains.
“If the operation can control moisture, and if the mines can get the moisture in that they are supposed to get in, there’s no dust,” said John Visser. “But typically production pressures come along and the management of moisture of ores is not as good as it could be, so there are still dusty trains.
“However, there’s been an order of magnitude improvement. Certainly 10 years ago the majority of fines trains were dusty, but today it’s the exception rather than the rule.