Dust Public Enemy Number One
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| Coal Dust! |
When material falls or is blown from conveyors or is stripped from
dockside stockpiles by the wind, that's profit falling out of the operation.
Worse still, the material that's lost is likely fall to earth somewhere from
where it can come back to haunt you in the form of increased costs in a number
of ways, such as by hastening the need for maintenance, fines from the
authorities, Environment Agency enforcement notices or even 'stop' notices.
In some countries site owners and
operators are required to take whatever steps are necessary to minimise the
impact of operations on their surroundings. In others, like China, which have
traditionally had a more relaxed attitude to such issues, there is an awakening
that standards have to change, and that's reflected in the plans for new
developments like the Qinhuangdao Port.
It's China's biggest coal transhipment
port, and had a throughput of 200m tonnes last year. By 2015, by when its
throughput is expected to have doubled, the port is predicted to have spent
more than $127m on environmental protection.
Defining dust as particles emitted to
air that constitute visual, physical, chemical or health hazards for employees
or the public offers a feel for the importance of the issue to anyone moving
dust-generating material.
The actual transfer of material from
ship-to-shore and vice-versa is well catered for and controlled by the
sophisticated filtration systems in use, but these often fail to extend as far
as stockpiles or road and rail vehicles during other parts of a load's journey.
The most common sources of dust in the
port industry are therefore the same as many others - any open storage,
handling and spillages of dry bulk cargoes.
And port operators can be at the wrong
end of it because of the physical properties of some bulk cargoes. The
brittleness of coal, for example, means that repeated handling causes it to
break into ever finer and finer pieces, simultaneously increasing the potential
for dispersal on lighter and lighter winds.
Particles smaller than 10 microns can
cause respiratory problems for employees. Larger particles need to be
controlled because of their economic value, their visual and environmental
impact, and their influence on maintenance frequency.
Canadian company Weathersolve
Structures has done considerable research into the way material of varying
sizes is moved. Movement can be caused by winds of varying speeds and by
mechanical influences, including falling from a conveyor, being disturbed by
conveyor transfers or discharges, or by vehicle tyres.
In all cases, says the company's design
engineer Mike Robinson, the distance particles move each day depends on the
vagaries of the wind and the size and weight of the particle. The lightest,
smallest dust particles can get caught in wind up draughts like a glider, and
can be carried thousands of miles as a result. Larger particles will be blown a
distance as they fall from a conveyor.
"After they hit the ground they
then move along the ground in a skipping motion (like a rock thrown across the
surface of a pond). The movement across the ground (called saltation) depends
on the wind speed, the roughness of the ground and the size and weight of the
particle," says Mr Robinson.
"Particles too heavy to saltate in
a given wind may still be moving by rolling. As the wind speed increases,
larger and larger particles begin moving, and the smaller, saltating particles
start getting lifted into the general airflow.
So how can dust be brought under
control? Putting stockpiles inside is one solution, but is not always
practical.
Windbreaks can be another answer, and
that's the one promoted by Weathersolve. With expertise built over 20 years
developing windbreak and fencing technology to protect kiwi fruit from the
worst of the weather on behalf of New Zealand's Ministry of Agriculture, Mr
Robinson is an expert in porous fabric structures.
He says a windbreak can reduce the
speed of the incoming wind, and its ability to pick up the material being
protected, by three quarters; if the windbreak is 50 feet high, then the
reduced wind speed area will extend for about 250 feet downwind. For 250 feet
beyond that, the wind will be half that of the incoming wind. Taller windbreaks
will naturally create larger wind shadows.
Trees can form an effective windbreak,
but can take far too long to grown to an effective size. They nevertheless
share the benefit of porous fabric structures in that air can pass through
them, and in doing so act as a buffer to prevent the air that flowed over the
top crashing down on the material being protected.
But slowing the wind is only part of
the story. Still more control can be achieved by the application of water and
dust suppression agents, each with a specific role.
Identifying which one will suit your
site is a matter for experts, but they fall into broad categories, such as open
areas and stockpiles, roadways and smaller handling yards, loading bays and
vehicle exit points.
With ever-tightening environmental
controls, particularly in Europe, it remain clear that more positive steps will
continue to be required to keep ahead of the legislation, probably involving
several methods of control for each material with the potential to be turned
into dust on its journey through a port's handling and storage systems.
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| Unprotected areas open to dust erosion |
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| Protected stockpile |
If you’re under of pressure
to find solutions for dust control problems – in addition to all the other
pressures you face – you might want to consider the unique advantages of
WeatherSolve wind shelters.
WeatherSolve wind shelters can be designed to heights of 100 feet (30 meters) for greater control of dust over larger areas. With poles up to 120 feet apart (36 meters) they also make it easy to accommodate conveyors and buildings and to cross roadways. They can even include doors for trucks to pass through.
Of course, the requirement for fewer poles also means lower structural costs and far less disruption during construction. Self-cleaning, and needing no daily consumables like oil, gas, electricity or water, WeatherSolve wind shelters are exceedingly low maintenance.
WeatherSolve designs have been thoroughly proven in every extreme from Hurricane Andrew (Florida 1992) and South Pacific cyclones to the unrelenting heat of Oman and Bahrain, the severe cold of Canadian winters in Northern B.C. and the South American Andes at 16,000 feet. We know of no other company anywhere near close to such experience.
Worldwide, total area under WeatherSolve protection exceeds 1,000 acres.
Tell us the problem. We’ll show you the solution!
WeatherSolve wind shelters can be designed to heights of 100 feet (30 meters) for greater control of dust over larger areas. With poles up to 120 feet apart (36 meters) they also make it easy to accommodate conveyors and buildings and to cross roadways. They can even include doors for trucks to pass through.
Of course, the requirement for fewer poles also means lower structural costs and far less disruption during construction. Self-cleaning, and needing no daily consumables like oil, gas, electricity or water, WeatherSolve wind shelters are exceedingly low maintenance.
WeatherSolve designs have been thoroughly proven in every extreme from Hurricane Andrew (Florida 1992) and South Pacific cyclones to the unrelenting heat of Oman and Bahrain, the severe cold of Canadian winters in Northern B.C. and the South American Andes at 16,000 feet. We know of no other company anywhere near close to such experience.
Worldwide, total area under WeatherSolve protection exceeds 1,000 acres.
Tell us the problem. We’ll show you the solution!
