Page 61 - HUB-4 Issue 98

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Sealing the Deal: Recycling Conveyor Dust Control
By Oliver Kämpfer – Martin Engineering DACH
Recycling commercial wastes, industrial
byproducts, metals, electronics, biomass,
cardboard, paper, and plastics is now firmly at
the heart of the raw material supply chain
Within these waste streams, fine materials can account for a
substantial share of the total output, requiring spillage and
dust control. Fugitive dust emissions create an unhealthy
work environment both inside and outside the plant. To make
matters worse, certain wastes emit toxic particulates during
processing, especially materials with corrosive properties,
adhesives, coatings, and other hazardous substances. [Fig.1]
Particulates also clog equipment air intakes, necessitating
additional maintenance and downtime.
Aside from crushing, grinding, and shredding, the most
common sources of dust in any recycling plant are conveyor
transfer points. As loose material drops onto a conveyor belt,
particulates disperse into the air. [Fig.3]
Figure 1 - Materials in the recycling process can contain
a significant proportion of fines.
Particulates matter
Although most of this particulate matter (PM) is considered
little more than a nuisance, particles ≤100 microns (µm) in
size are considered ‘inhalable,’ and particles smaller than
PM40 (≤40 µm) are usually invisible to the naked eye. Many
recycling processes emit particles smaller than PM10 (≤10
µm), which are considered ‘respirable.’ PM2.5 (≤2.5 µm),
known as fine particles, can penetrate deeply into the lungs.
At this level, some particles cross into the bloodstream. [Fig.2]
Figure 3 - Dust can create serious issues at transfer points.
Containment is key
Poor transfer point design is among the main causes of dust
emissions. Turbulence in the loading zone creates pressure in
the transfer point enclosure, which forces airborne dust out of
any available opening. Operators generally find that passive
dust control through retrofitted transfer-point design changes
is more practical and cost-effective than misting systems or
HVAC solutions.
Well-designed transfer chutes have several key features that
minimise the dispersal of fine material as it drops and settles
onto a conveyor belt. Firstly, the length, angle, size, and
shape of a chute dictate precisely how material arrives onto
the belt below. For example, with centered, sloped, and
spoon-shaped chute configurations, material is eased onto the
belt with less impact and little or no rebounding. This design
reduces air turbulence and minimizes load shifting. [Fig.4]
Figure 2 - Comparison of particle sizes.
Maintenance teams often struggle to stay on top of cleanup,
leading to workplace safety violations. Additionally, dust is
known to foul exposed machine components, causing them to
wear faster and require servicing and replacement sooner.
Figure 4 - A well-designed transfer point can address
the root causes of dust emissions.
www.hub-4.com May/June - Issue 98
| p61 |