Paper Technology International 2020 - Journal - Page 64

PAPERTECHNOLOGYINTERNATIONAL
The future of charge measurement and control
All this has been known for some time (the original article
was 2011 and the science predates that by many years) but the
future lies in automating both the measurements and control
functions. The driver here is the scarcity of trained and experienced
lab staff at many mills to constantly monitor and control system
charge.
The latest innovation is to take the PCD measurement online in a straightforward single point measurement to continuously
read out the particulate charge. Combined with a thorough
understanding of system charge chemistry via charge mapping
as described above, this would ideally allow direct control of
appropriate chemistry, most typically a cationic polymer used as a
‘trash collector’ or retention aid.
Here is as example of a control loop on a tissue machine
going into action. The result of this control: higher machine speed,
long blade life, better crepe ratio and fewer web breaks.
This has proved a successful approach in classic closed
control loops for stable systems but the promise for the future is to
combine multiple and complex process inputs into a multi-variate
model of the system chemistry, and then use this model to control
critical process inputs, including chemistry. This should allow us
to extend the benefits of charge control to more challenging and
complex systems.
40% Chemical savings and more stable quality
Back to our opening story. In fact, this describes the case
in a Middle East tissue mill which ended up with a typical chemical
soup. Trained experts patiently mapped this and suggested the
appropriate actions to change addition points and control trash and
retention. Not only was this client able to reduce their chemical
spend by a staggering 40%, they also were able to achieve much
improved tissue machine operation with stable quality and fewer
web breaks, thus reducing to just weeks the payback time for
the initial investment in instrumentation and training. This story is
repeated many times for customers who decided to stop guessing
and start to measure their chemistry and ‘get out of the soup’.
Figure 8: Here is an example of a control loop on a tissue
machine going into action.
For many more details on how to use charge control to improve paper machine operating efficiency including information on lab
measurement and mill-proven on-line measurements, please visit BTG at www.btg.com, and check out our animated guide to
charge control on the PTI web platform ().
About BTG
The BTG Group is a multinational provider of integrated, highly specialized process solutions for the global pulp and paper
industry. Every day our people help customers achieve sustainable gains in business performance through our application
know-how and industry-leading technologies. This includes world-leading rods and beds for film-metering size presses; highperformance ceramic and cermet coating blades; high-performance tissue creping doctors and doctor holders, specialty doctor
blades and pulp and paper process control sensors and laboratory instruments. All of these technologies are supported with
expert services and application support.
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