UUtilizing the unused energy flows inside the paper mills - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 16

UUtilizing the unused energy flows inside the paper mills - Paper Technology International 2023

PAPERTECHNOLOGYINTERNATIONAL Paper Technology International 2023
Cold Water – from 10 to 25°C
Cold water can be usually directly used in cooling of certain
areas of paper mills. Either E-rooms or halls, usually the fresh water
in Europe is cool enough that the cooling effect can be utilized in
certain branches.
With specially engineered climate cabinets the E-rooms can
be cooled with fresh water. The Paper Line of climate cabinets by
BM Green cooling is specifically designed to be able to use higher
water temperatures and still maintain the air temperature on the
level that is specified in the ASHRAE norms. The climate cabinets
can also be supplied with stainless steel piping if the water quality
demands it. Additionally, the stock Paper Line cabinets include
the Siemens S7 control unit for easy controlling with the existing
Process Control System (PCS) of the mill. Available are also
versions without their own control units, so they can be controlled
directly by the PCS.
Cold water can also be used in the summer to cool down
the hot halls in the mills, like the warehouses, roller halls or packing
halls.
After using the cold water in cooling, it is returned to
the flow it was taken from. This means that the overall water
consumption of the mill is not increased, and we get the additional
benefit of 100% heat recovery. As cooling the hall increases the
water temperature, this means that the water does not need to be
warmed as much later when used in the process.
This way the risk for Legionella and problems with steam is
prevented.
While cooling the affluent water is possible, it is not the
most efficient solution as the heat is dissipated into the surrounding
air and wasted. That is why using heat recovery would be the best
option for the overall efficiency of the mill.
The affluent water is mostly not warm enough to be used
directly in any heating applications, but it can be utilized as a heat
source for heat pump. With high temperature heat pump the water
temperature can be raised to up to 90°C, which allows versatile use
in various applications. In the winter the heated water can also be
used in heating the offices or other social parts of the building, or it
can be sold for district heating.
Figure 3: Heatpump “High temperature Heat Pump for heat
recovery”.
Figure 2: The Climate Cabinet: “Special Engineered Climate
cabinet for the paper industry, with Siemens S7 control unit and
A-shape coil to enable high natural cooling share for a year”.
Warm Water – from 25 to 55°C
Warm water is for example the affluent water that is going to
be given back to the water source. Usually, this water needs to be
cooled down before being released back into nature to minimize the
environmental impact. The water is however not warm enough to be
useful in heating applications.
During recent years we have faced increasing demand for
cooling of the affluent water. The regulation is getting tighter, and the
environmental questions are getting more important. Affluent water
can be cooled down with dry coolers, adiabatic dry coolers or closed
cooling towers. What is common in all these solutions is that they
are closed systems to prevent the affluent water from vaporizing.
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Hot water and steam – from 70 to >150°C
If there is hot water that cannot be used in the process and
needs to be cooled down, there are options to utilize this water. In
winter this could be used in the heating, but on paper mills there is
usually too much heat. This means that during the summer there are
not many great options to use this water in heating.
One option is an absorber chiller. An absorption chiller uses
the hot water to provide chilled water for the cooling applications. In
absorption process the heat energy from the hot water replaces the
electrical energy needed for the compressor in the traditional chiller
solution. This solves the problem of having too much heat in the
paper mill and can be used for example to cool the E-rooms in the
process.
While previously the absorption could be done with 100
to 90 °C water, the technique has matured and currently it is
possible to use as low as 70°C inlet water for the absorption chiller.
Possibility for using lower temperatures means that the technique
can be used more often on the mills.
Modern absorber chillers can also use gas and steam as a
heat source, enabling a very wide range of applications.
Normally the benefits of the absorption system are highest
in the summer when there is too much heat on the mill and the need
for heating is reduced.
With absorption and adsorption technic the needed electrical
energy is drastically reduced. To cool 1.000 kW the absorber needs
only 9 kW of electrical energy. Additionally, there is the electricity
needed for fans of the condensing unit, and this depends on the

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