FLUID HANDLING
INDUSTRIAL PROCESSES
BURKERT
MINIMISING COSTS THROUGH
PROCESS OPTIMISATION
The control of industrial processes can be a
complex operation involving multiple valves,
sensors and controllers which means there
are many considerations when looking for
opportunities for process optimisation. Using
best practice and ensuring control protocols
are updated when process changes are
implemented however, ensures the process
remains efficient and effective.
Greg Wainhouse, UK Water Segment
Manager at Bürkert, looks at some examples
from different industries, where process
optimisation can deliver significant
improvements and reduce costs.
Process control engineers are constantly
aiming for perfection while all the time
tackling the challenges that stand in their
way. From variable inputs to changing
conditions and complex infrastructure, there
is always another obstacle to overcome, but
by taking advantage of expertise within the
industry, it is possible to make significant
practical improvements.
WASTE WATER PROCESSING
One of the major challenges in the water
treatment sector involves the sludge
dewatering process, which in many cases
involves high speed centrifuges that separate
the solid and liquid fractions. To assist this
process, a polymer is added to the sludge to
help bind the solid particles together. The
goal is to produce a final product that has
the right consistency that makes transport
efficient, without moving excess water to the
fields, where it is spread as agricultural soil
enhancer.
The process has a number of variables,
including the percentage solids of the
raw sludge, the flowrate of the sludge, the
amount of polymer being added and the
speed of the centrifuge. Of these, the solid
content of the sludge is crucial to determine
the settings for the rest of the process.
There are several ways in which this can be
determined, including a process where a
sludge sample is placed in a petri dish, and
the water is evaporated off to obtain the
mass of the solids. This is not a very efficient
process and can take 45 minutes to complete.
Once the results are available, the centrifuge
and polymer settings can be adjusted and
an improvement in the consistency of the
dewatered sludge should be apparent.
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PECM Issue 38
Precision control of cleaning processes in hygienic applications can improve productivity.
However, changes in the solids content can
occur frequently, which makes this process
quite ineffective and labour intensive. In
addition, it is a reactive process, more often
used when the consistency of the dried
sludge doesn’t meet expectations. During
the time taken to observe the change,
complete the test and alter the settings, the
centrifuge has continued to discharge a sub-
standard end product.
By creating a pro-active system that makes
adjustments based on data from the inlet, as
opposed to a reactive system that observes
the results before implementing a change,
process engineers will be following best
practice. Furthermore, this setup reduces the
amount of operator intervention and delivers
a more stable output.
BREWING PERFECTION
In the first instance, assessing the percentage
of solids using a turbidity sensor located on
the intake to the centrifuge will significantly
increase the response time to any changes.
These sensors look at refracted light to
provide an approximation of the solids
loading of the incoming sludge, but they
can suffer from fouling problems, and the
calibration process can be interpreted
differently by various operators. An important part of the brewing process is
adding oxygen to the wort to allow the yeast
to thrive and create the alcohol and carbon
dioxide. After the boiled wort has been
chilled to fermentation temperature, oxygen
is used to start the fermentation process.
If air, which contains 20% oxygen, is added,
then the process can only achieve an O2
concentration of eight parts per million
(ppm). For higher levels, around 10 ppm,
typically used by commercial breweries
for higher strength beers, pure oxygen is
required.
By constantly monitoring the inlet of the
process, adjustments can be made quickly
and the amount of processed sludge
that falls below the required standard is
minimised. Further improvements can be
made by adding a flowmeter, or better
still a device that provides a mass flow
measurement. However, the ability of the wort to absorb
oxygen is affected by its specific gravity,
which is measured on the Plato gravity scale.
This measures the concentration of dissolved
solids in the wort. Furthermore, each yeast
strain has an optimum oxygen level and if
this is not achieved precisely, the optimum
fermentation rate will not be achieved.
DEALING WITH SOLIDS IN
SUSPENSION