Spring cleaning the dust away

Dust remains an ever present menace in dry bulk terminals. This is, of course, hardly surprising, given that the potential for fugitive dust emissions occurs along virtually every step of the terminal process, from vessel loading and discharge, through material transfer to stockpiling.
 
Modern bulk terminals have years of experience in minimising dust emissions, and an industry has developed to supply various technologies to help. But complacency can never be allowed to set in. 
 
It is interesting to note that dust is one environmental concern that has consistently appeared in the priority list of the European port sector over the past 20 years, according to the 2016 environmental review conducted by the European Seaports Organisation (ESPO). 
 
It may have slipped in the priority ranking – from fourth place in 2004 to ninth in 2016 – but ESPO points out that the precise ranking is less relevant than the fact that controlling dust stands alongside dredging and land as one of three potential environmental headaches that simply won’t go away.
In fact, the 2016 survey highlighted air quality as the number one priority for European ports, as it was in 2013. While much of the concern is over emissions from vessel and terminal operations, dust levels are clearly an important component of overall air quality.
Wild West
 
Even in more remote locations, the management of dust from dry bulk handling has become a critical concern. In August this year, the government of Western Australia (WA) released its latest report on dust management at the huge Port Hedland dry bulk facility, which is located in WA’s Pilbara region, a vast and scarcely populated corner of the state. 
The latest report is part of a long running effort by the WA authorities to arrive at a sensible compromise between cleaning up the port’s environmental impact, and allowing it to function effectively. 
 
Port Hedland is the largest bulk handling port in the world, and makes a major contribution to the WA and Australian economies. In 2014-15, the value of exports through the port was almost A$30B, accounting for 27% of WA’s merchandise exports, and 12% of Australia’s as a whole. Its users generated about half of the WA government’s royalty income – A$2.4B in 2014-15.
But the port and town of Port Hedland, which has just 4,500 or so residents, grew up in an era before modern planning principles on buffers and the separation of industrial, residential and commercial activities. The health risks of exposure to dust were also not well known. The port’s industrial facilities are close to homes and businesses in Port Hedland’s West End. Areas close to the port sometimes record elevated dust levels due to port activity. 
In 2009, the Environmental Protection Authority raised concerns about the possible effects of dust on the health of Port Hedland residents, prompted by reports of high dust levels, mounting scientific evidence that high dust  concentrations can harm human health, and worries that projected growth in throughput at the port could result in rising dust emissions.
In 2009, the state’s premier established the Port Hedland Dust Management Taskforce to coordinate and plan for dust management there. The taskforce produced the Port Hedland Air Quality and Noise Management Plan, which included interim measures to limit exposure to dust by groups considered most at risk of health effects.
Since 2010, the port’s governing body, Pilbara Ports Authority, has relocated all external stockpiles from the eastern side of the harbour to the Utah Point facility. All bulk materials handling on the eastern side under the management of the authority is now undertaken within closed sheds or by using containers. The authority monitors dust at Utah Point and its eastern operations using what it considers are best practice technologies and processes.
Mitigation measures
Dust control measures include water cannons and misting sprays, and the requirement for all materials delivered to the site to be at the correct moisture levels to limit dust generation. Conveyor systems and transfer stations are all sealed to limit dust emissions on site. The condition and quality of materials delivered to Utah Point and eastern operations is the responsibility of the shippers using these facilities. However, if this is not done properly, the port authority takes action to limit (and in some cases refuse) delivery of materials until the correct quality objectives can be met. 
Major port users, too, have implemented dust mitigation measures for their operations. In 2010, BHP Billiton Iron Ore relocated its crushing and screening facilities, which historically were some of the larger dust contributors, to its mines. It has also increased the use of direct-toship loading, reducing the need to double-handle materials at the port. Fortescue Metals Group’s dust management plan covers a range of construction and operational stage dust mitigation measures. Dust mitigation for construction includes measures affecting vegetation clearing, for example, use of water carts, and staged clearing, as well as earthworks, such as minimising areas to be cleared.
Operational dust mitigation measures cover railcars, like enclosing key components of car dumpers, conveyors and transfer points (moisture control and enclosing them), stackers (spray heads), reclaimers (water sprayers), stockpiles (using coarse stockpiles to protect fines stockpiles) and shiploading (water sprayers). 
 
But, while industry has achieved significant improvements in dust management in recent years, further improvements are required to ensure dust emissions do not increase, and, where practicable, are reduced, if increases in port throughput occur, the report states. 
Data monitoring
In response to the taskforce’s initial recommendations, the Port Hedland Industries Council (PHIC), which represents big mining interests like BHP and Fortescue, as well as Pilbara Ports Authority, established a network of dust monitors to collect data on dust types and levels. In addition, PHIC, along with the Department of Environment Regulation, commissioned modelling to improve understanding of dust impacts arising from the port’s development, while the Department of Health commissioned a Health Risk Assessment to evaluate health effects of the types of dust found.
Having spent years completing all these studies the taskforce is now making final recommendations to government. The health risk assessment concluded that there is sufficient evidence of possible negative effects on human health from dust to warrant further controls and landuse planning to reduce community exposure. Air quality monitoring data indicates that dust levels regularly exceed the taskforce’s interim guideline levels in the far West End of the town.
Dust levels have remained relatively stable in recent years, despite much higher export tonnages through the port, however. But, while port users have made substantial progress in reducing the intensity of dust emissions, these measures have not been enough to reduce them to “acceptable levels” in the West End, the taskforce says. If levels increase further, they will affect areas further east.
In short, the taskforce sets out three main recommendations. Exporters should continue to be required to reduce the dust emissions arising from port activities, and should be subject to more stringent risk-based regulation aimed at reducing the number of days when standards are exceeded. 
A Special Control Area should apply over the West End of Port Hedland, aimed at preventing further residential population growth west of Taplin Street, and limiting sensitive uses between Taplin Street and McGregor Street. 
 
Finally, the state government and the town will work with the community to improve Port Hedland’s amenity, including identifying and addressing dust sources other than the port. 

Since 2010, Pilbara Ports Authority has relocated external stockpiles from the east of Port Hedland

Hop to it 
 
In more highly densely populated areas, the scope for large-scale displacement of stockpiles, or even the careful land-use planning measure that Port Hedland has implemented, might not be possible. 
 
In this case, smaller scale  solutions are required. One such is the use of quayside hoppers to contain fugitive dust during vessels operations before it has a chance to spread more widely across the port. 
 
Earlier this year, Samson Materials Handling won an order from TradeMark East Africa for four Eco Hoppers with ATEX to be used at Port of Mombasa, Kenya. The engineering design was the result of collaboration between Samson, based in Ely, UK, and Germany’s Schade Lagertechnik. Both firms are part of the Aumund Group.
The hoppers will be used for the import of clinker, coal and gypsum. Management of air quality and fugitive dust is very important, as the operation takes place in a dusty atmosphere with high levels of humidity, and in temperatures as high as 40 degC.
Additional tools
A variety of dust suppression measures will be employed both at the intake area of the Eco Hopper itself, as well as on a dusting system situated between the hopper and truck. The dust reduction measures include an automatic reverse-jet cleaning system, air compressors, inlet grill with suction capacity, a flex-flap creating a pressure differential, and a dust filter unit on three sides of the hopper.
Each hopper’s inlet grill measures 6m x 6m, and is topped by a 2m-high shroud that creates an aperture of 8.2m x 8.2m for grab discharge, thus mitigating the effects of high winds. Mounted on a chassis, the total height of the configuration is 15.7m, allowing a truck clearance height of over 4m. The Eco Hoppers are mobile with powered travel, and have crabbing ability to position them at specific points along the vessel. The throughput of each Eco Hopper is designed to operate at a peak rate of 700 tph.
Ivorian order
The Mombasa order followed another deal in Africa. Belgium-based SEA-Invest placed an order for an Eco Hopper for operation in the Ivory Coast. This hopper will discharge onto a high-level quayside conveyor at a rate of 1,200 tph, or via a dedicated outlet direct to trucks at 700 tph. Designed to withstand crosswinds and grab impact damage, SEA-Invest chose the Eco Hopper for its flexibility.
In addition to being able to handle a variety of different materials, the equipment can be configured at a later stage to suit evolving port operations. SEA-Invest emphasised the importance of this last point, as port operators need to  make sure that logistics costs are compatible with the market price of the materials being transported, and their equipment must be able to respond to changes in market conditions.