UUtilizing the unused energy flows inside the paper mills - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 17

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

PAPER TECHNOLOGY INTERNATIONAL Paper Technology International 2023
outside temperature. Based on our existing projects the highest
consumption here is about 60 kW for cooling capacity of 1.000 kW.
The calculated EER (Energy Efficiency Ratio) of this solution for the
electrical energy needed here is then 14,5 (1.000 kW/69 kW) in the
worst scenario in the summer. Comparing this to the normal EER of
chillers which is on the level of 3-4, the efficiency is on another level.
We must not forget that absorption solution uses the heat energy
for the cooling effect, but if it is possible to use heat which would be
otherwise wasted, the efficiency is raised a lot.
Other not so commonly known option is to use a small
generator that uses the hot water to produce electricity. While this
might not be suitable for most of the mills, it could be the optimal
solution for some. By using the hot water in electricity production,
the water is cooled down, and the generated electricity can replace
the bought electrical energy, therefore saving costs and total energy
consumed.
Freecooling
Reducing of the energy needed for cooling can be done by
utilizing free cooling, where the cooling medium is outside air. With
purposefully designed climate cabinets for example the E-rooms
of paper mills can be cooled with indirect free cooling up to 14°C
outside temperatures. This means that during outside temperatures
under 14°C no mechanical cooling is needed. For example in
Düsseldorf, Germany, the temperature remains under 14°C for 64%
of the year.
When mechanical cooling is replaced with free cooling or
natural cooling (for example fresh water inside the plant) the savings
can be up to 95% in the electrical power consumed. On yearly
basis in Düsseldorf this would then mean roughly 60% saving in
the electricity consumption in the cooling system compared to a
traditional mechanical cooling solution.
Figure 4: Absorber chiller “Low Temperature Absorber that
uses 70°C water as a heat source”.
Reducing the electricity consumption in cooling
Reducing the energy consumption in cooling in the high heat
load areas such as papermills is also a crucial part of saving energy.
For example, the E-rooms require constant cooling when the paper
process is running. Yearly this equals to high energy consumption as
the heat loads are high and the need for cooling is constant.
Ways to reduce the energy needed include mostly simply
taking the most energy intensive part of the cooling out of the
equation. This would in most cases be the chiller compressor,
whether the cooling is done with DX (Direct Expansion) or water/air
cooled chillers.
Figure 5: Drycoolers “Drycoolers to provide freecooling up to
14°C Outside temperature”.
Natural cooling
If the cooling of the E-rooms can be done with the cold
water, the energy efficiency is even higher as we are taking the fans
of the dry coolers away from the equation. The only parts that use
energy are the pumps, but the pump using is comparable to other
liquid-based cooling solutions, whether it is with free cooling or
compressor cooling.
CONCLUSION
When considering the energy savings on the paper mill, utilizing the existing energy is a great way to go. Whether the flows
are hot or cold or something in between, usually there is a way to use it in a way that saves energy and the environment.
Problems can still arise from the material choices and compatibility of the different utilization solutions between each other,
and even availability of the said flows during the different times of the year. As the pioneer of natural cooling in the paper mill,
on top of engineering of the natural cooling solutions BM Green Cooling also provides study projects for plants to get a better
understanding of the usability of the different flows and how to better utilize them inside the paper mill. With the information the
customer has a better understanding of the possibilities, the needed investment, special requirements to take into consideration
and the savings potential of the solution.
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