A fundamental consideration for handling and discharge arrangements for cereal products in the chain from field to end of process is that of controlling the generation of fugitive material (dust) into the atmosphere. The need to control dust levels is driven by a number of factors such as the long term health of operators, plant hygiene or plant operational safety (ATEX/DSEAR).

1. DUST SUPPRESSION
A
fundamental consideration
for handling and discharge
arrangements for cereal products
in the chain from field to end of
process is that of controlling the
generation of fugitive material
(dust) into the atmosphere. The
need to control dust levels is driven
by a number of factors such as the
long term health of operators, plant hygiene or plant operational
safety (ATEX/DSEAR).
High dust levels can result from the stripping away of ‘piggy
back’ fines (i.e. dust that has attached to the outside of larger
particles and is transported with them through the process) by
impact or counter directional air flows. Alternatively, dust can be
generated through the breakage of larger particles (i.e. impact or
shear plane damage).
Handling operations that deliver the former set of condition
for removal and transportation of ‘piggy back’ fines would
typically include the filling of bulk storage units by either gravity
of pneumatically – where significant distances for free-fall
conditions or trajectory establishment exist.
The direct generation of dust through particle damage can
occur in large stores where the discharging flow channel expands
and flows through static regions of product (often referred to as
internal mass flow [1]) or where constant capacity feeders such
as augers, drag links or belts extract from long outlets without
optimised design or interface considerations – in which case
the feeder will tend to drag conveyed product beneath a non-
activated region of product.
Any fines/dust generated through either of these common
handling operations may not necessarily become a problem
in later stages of operations. For example if fines/dust are
generically considered to be represented by sub 3.15mm (for
example) and constitutes 2 percent by weight per cubic metre of
product, there may be no issues of excessive dust mobilisation
through subsequent handling provided that that size fraction
remains homogenously distributed within each volume of
product.
However, problems often result when products are loaded into
storage schemes where many cubic metres are stored. In such
instances the simple operation of filling the store has a strong
likelihood of mobilising the resident fines and redistributing
them within the bulk – with the result that some volumes of
material may contain less than our nominal 2 percent wt, whilst
others could contain in excess of 10 percent wt. Thus during
the discharge or load out operations that the store may provide,
the dust levels may fluctuate considerably depending upon the
severity of the redistribution of fines, the method of extraction
and the inventory level within the store.
The implication of this variance in dust content lies in how the
specification for any locally applied dust extraction system has
been developed. Using the 2 percent wt fines model again, it can
be understood that this value should be used to size the filter area
for an extraction system and the type of filter operation.
On first consideration, the use of the ‘specification’ fines content
would seem a prudent basis for design. Economic considerations
tend to dictate that the specification of the filter would be closely
matched to the application requirement. However, once installed
and commissioned the intermitted fluctuations in fines/dust
content are likely to overwhelm the ability of the dust extraction
system.
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3. KAHL Crown Expander
Flexible production of shaped products.
Preconditioning of pellet mixtures.
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Stand B 099
Such overload conditions would result in blinding of the filters
(assuming that the cleaning method was configured to operate
on a timed interval) or excessive air consumption (in the case of
a reverse jet pulse system triggered by a pre-defined maximum
pressure drop value).
An assessment of the potential dustiness or brittleness of
the material being handled can provide the first element of a
structured approach to pre-empting dust levels or the scope for
variations in fines/dust released in handling operations and, in
turn, developing an effective specification for associated plant.
The assessment to characterise bulk particulate materials for
dustiness or breakage behaviour can be undertaken at laboratory
scale. The evaluation of dustiness (i.e. surface attached ‘piggy
back’ particles) can be effected through the use of a Warren
Spring type tester which takes the form of a closed drum that
has internal ‘lifting’ slats attached at six points around its
circumference that extend down the length of the chamber.
The test sample is tumbled inside the drum whilst an air flow
is allowed to pass from one end of the chamber to an exhaust
port at the opposite end which delivers dust laden air onto a filter
element. The gain weight of the filter is taken as a benchmark
indication of the ease with which dust can be liberated from the
parent particles.
Breakage tests can be undertaken that project particulate
material at controlled velocity against steel targets that are
arranged around a centrifugal accelerator. Assessment of
breakage is simply undertaken by the comparison of particle
size distribution shifts (towards increasing fines) in response to
increasing impact velocities.
Both of these methods represent useful techniques for obtaining
information for comparison of the likely dust and breakage
behaviour for different cereal crops, seasonally sourced crops or
pelletised products. The tests can also accommodate variables
such as temperature or moisture content variation (both of which
can be influential factors relating to dustiness).
In terms of counter measures to deal with excessive dust
mobility, one of the key aspects of best practice is to avoid
the establishment of high velocity movement of particles or
dispersion at transfer points – both being factors that facilitate
the penetration of air into the bulk material and the stripping
out of fines/dust. Finer material having a lower mass and
correspondingly relatively large surface area, have a high drag
factor – which endows them with a substantially higher mobility
in air compared to coarser particles.
Belt transfer points are a prime example of where dispersed
particulate movements occur, which means that not only can a
degree of breakage occur, but also that an existing or additional
fines can be easily dispersed to atmosphere or dragged by air flows
along transport tunnels. The application of ‘hood and spoon’
transfer point design can help considerably in delivering a focussed
flow of material sympathetically to the direction of belt travel.
This is a technique that has found a high level of utility in pellet
handling operations where breakage must be minimised.
In conclusion, it is hoped that it can be appreciated that a
problem such as dust emissions at certain points in a process is
usually the end result of a cumulative breakage and concentrating
of fines/dust that has occurred through the plant. Methods exist
to design out a wide range of the causes of dust and variable dust
loading, but also to reduce the magnitude of problem caused by
inherently dusty materials.
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4. Low-dust flours prove their health protection
properties GoodMills Innovation: finalist in German Health and Safety Prize
GoodMills Innovation has enjoyed
success in the German Health and
Safety Prize 2015. The company’s
low-dust technical processing
flours achieved second place in the
category “technological solutions
for small and midsized companies”.
Its processing flours create
significantly less dust than
comparable products from other
suppliers and can help to prevent
or reduce problems associated with
job-related respiratory diseases.
Prior to the award, a four-person
expert panel examined the science
behind the flours, as well as their
technical aspects and methods of
production.
The philosophy
The philosophy of the company
is always to provide the baking
industry and also craft bakers with
value-added products that meet
current demands. Be it by offering
appealing product concepts that
convince due to clean labels or
nutritional benefits of the end
products which can be claimed,
or by simplifying processing
parameters for the bakers.
The latter is a good example
for the idea behind GoodMills
Innovation process flours; working
with most modern refining
methods, the grain experts were
confident to find an approach to
reduce the health risk for bakers by
adjusting defined properties to the
flour. With regards to job-related
diseases, baker’s asthma is still one
of the most occurring health issues.
Once suffering, many employees
are not able to maintain their work.
The German employer’s liability
insurance association spent 37,5
Mio. € in 2003 .
The Flour
The particular properties of the
flours are attributable to the special
hydrothermic processes used in
their production. These reduce dust
development by up to 85 percent
compared with all-purpose flour.
Thus, significant improvements
in room air can be achieved, with
positive health benefits for bakery
employees.
The flours also score when it
comes to hygiene – thanks to
their antistatic effect and the fact
that enzymes are deactivated
by the thermal treatment.
Cleaning production plants and
machinery becomes simpler and
microorganisms, which cause
mould growth and mildew spots,
are significantly reduced.
Additionally, dough pieces don’t
stick to process surfaces such as
conveyor belts and proofing trays.
Experience has also shown that
technical equipment and filter
systems require less maintenance.
Health problems solved
GoodMills Innovation have been
able to reduce the respirable dust
component (the fine dust that is able
to reach the cells of the lung) of
their process flours significantly (up
to 85 percent) compared with all-
purpose wheat flour. With low dust
load in the air, several advantages
are obvious:
• The amount of inhaled dust is
significantly reduced.
• Less dust means significantly less
cleaning.
In addition, the flour has an anti-
static effect, which makes it easy to
sweep and remove. And, thanks to
its excellent releasing effect, dough
residues and encrustations are a
thing of the past. Exhaust systems
and sensitive electronic engineering
need less maintenance, and product
waste and breakdowns can be
minimised as the dough doesn’t
stick, ensuring smooth production.
Additionally, thanks to the
specific refinement process, the
enzymes inherent to flour can be
deactivated. For employee’s health
that means a preventive approach
against skin irritations and allergies;
from a hygienic point of view, mold
growth and on trays and belts and
mold stains on proofing linens are
prevented.
The Portfolio
The GoodMills Innovation
portfolio of processing flours
includes three flagship brands: Ping-
Pong 500, Tip-Top Ultra Clean and
Tip-Top Ultra Clean Spezial.
Ping-Pong 500 has already
won awards. In 2010, a German
employer’s liability insurance
association honoured it with an
award for its disease-preventing
properties.
In addition, in a comparable test
of nine different low-dust products
conducted by the German institute
for grain processing (IGV), Ping-
Pong 500 came out on top.
“Baker’s asthma is still one of
the most common job-related
respiratory diseases,” says Kai
Wörzler, Product Manager Bakery
at GoodMills Innovation GmbH.
“Our products make working life
easier for many bakers and can
contribute to improved health. We
are proud to have been recognised
with this award, as it confirms
that our investment in R&D is
worthwhile.”
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