How to save energy up to 30-70% in paper machine vacuum system? - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 41

How to save energy up to 30-70% in paper machine vacuum system? - Paper Technology International 2023

PAPERTECHNOLOGYINTERNATIONAL
How to save energy up to 30-70% in paper machine vacuum system? - Paper Technology International 2023
Anna-Riina Ahonen, Marketing Manager, Runtech Systems
INTRODUCTION:
Today, every mill is looking for ways to save energy – not only to cut down costs but also to reduce its carbon footprint. We at
Runtech Systems are happy to share with you some tips how to do it.
Say yes to lower energy consumption and costs
Using vacuum in various paper machine positions is
expensive. In fact, vacuum is one of the top three energy consumers
in a paper mill. By using vacuum only in the most critical positions,
you can fully benefit from a more efficient nip dewatering strategy
and save energy. And by measuring the water flow online accurately
enables you to optimize vacuum levels and not overdo them.
Heat recovery provides another excellent way to save
energy. Using recovered heat instead of primary energy sources, for
example, to warm up shower waters or dryer hoods allows you to
expect major cost savings.
By optimizing your papermaking process, you can save
energy up to 30-70% in vacuum system as well as improve
runnability and paper quality.
Ensure optimal operation of your vacuum system
There is vast potential for energy savings in vacuum
systems, as many paper machines suffer from poor energy
efficiency. Some machines would benefit from a complete
system rebuild. But in other cases, the required modifications
can be relatively small compared to the savings gained. One
often overlooked factor lowering efficiency can be the lack of
maintenance.
The benefits of regular and correctly timed vacuum
system maintenance are obvious. When properly maintained, the
operational efficiency of the vacuum system is kept at an optimum
level, and unexpected shutdowns are avoided. It is important to also
service the auxiliary equipment.
The cost of energy used by a vacuum system over its
lifetime exceeds its purchase price many times over. This means
that working at the optimum settings of a vacuum system is one
of the most important economic factors in mill operation. If left
untouched over long periods, the availability and efficiency of a
system will decrease, and operating costs will inevitably increase.
By maintaining your vacuum system, you can keep
efficiency at an optimal level and secure the stable operation of your
papermaking line.
Switch to an EP Turbo Blower
Did you know that the EP Turbo Blower is at least 15-30%
more efficient than a new liquid ring pump (LRP)? And as a LRP
wears down, this difference grows. In typical rebuild projects, 4060% energy savings have been achieved.
Process optimization and lower energy consumption start
with the EP Turbo Blower. This completely water-free vacuum
solution offers significant heat recovery potential for paper, board
and tissue machines. Mills have reported that vacuum system
optimization with variable speed and capacity turbo blowers have
saved them up to 2,000 kW.
Figure 1: RunEco EP Turbo Blowers are modern blowers with
integrated high-speed motor controlled by a frequency converter:
rotation speed and vacuum level can be adjusted according to the
process requirements.
A typical Runtech RunEco vacuum system consists
of several smaller size turbo blowers giving clear design and
operational advantages over the competition. In addition, as the only
company in the world we also offer liquid ring pump technology to
form a combination of both technologies – a hybrid system. With
this portfolio, we can always find a perfect fit for our customers’
demands, needs and budget.
Quite often a situation has been observed where a single, or
a few low air flow consumers (devices) are operating at high vacuum
levels, such as a high vac box or a press suction roll high vacuum
zone, while the rest use a considerably lower vacuum level. This
leads to a situation where the most economical option is to continue
the use of the existing LRP. Fully rebuilding a system with blower
technology is not always the most efficient solution, especially if
this means that different vacuum levels need to be combined in
one blower. It is proven that a well maintained LRP operating at
low speed to produce high vacuum level can perform at a good
efficiency level outperforming systems where a large single blower
experiences considerable expansion losses.
For example (see picture 2), a paper machine often has
multiple vacuum consumers and vacuum levels. By combining all
these together to a single large unit you inherently introduce losses
and lower your system’s efficiency. As is evident in this case, only
one consumer can operate at the blower vacuum and all the others
need throttling control that lead to significant energy losses. In
addition, as air is a compressible medium which changes volume
significantly with the surrounding pressure, a single large unit will
experience expansion losses.
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