Paper Technology International 2024 - Journal - Page 58
However if the heat energy harvested from the waste water
could be utilized somewhere and reduce the need for providing
energy for that part of the process, we are not talking about wasting
the energy anymore, but an actual and viable heat recovery.
BM Green Cooling specializes in heat recovery solutions
utilizing the modernest heat pump technology. Heat pumps offer a
unique opportunity to not only cool waste water ef昀椀ciently but also
recover the heat for various bene昀椀cial applications within the paper
production process.
Heat pumps as the missing link between the temperature levels
During the last years heat pumps have been in the middle
of great attention as Europe is moving away from fossil fuels. Many
have installed a heat pump to their house or of昀椀ce, but the big
applications and the range of possibilities are less known for the
public.
In basic principle the heat pumps move energy between two
mediums with a compressor. Ef昀椀ciency of heat pumps is measured
in COP (Coef昀椀cienct of Performance), the relationship between the
power (kW) that is drawn out of the heat pump as cooling or heat,
and the power (kW) that is supplied to the compressor. For example
if the compressor uses 2 kW of power and heat pump gives out 10
kW of heat, the COP is 5 (10 kW / 2 kW).
The ef昀椀ciency is dependent on the temperature difference
between the two sides, as seen in the table:
The range of applications for the warm side is wide, as is
the temperature range that can be achieved with modern heat pump
technology. Applications include heating the halls, of昀椀ces or selling
the heat for the district heating. Inside paper mills the heat can also
be for example utilized in preheating the process water.
Expanding the range of possible consumer side
temperatures results to the applications for heat recovery becoming
more versatile.
Natural refrigerants
Refrigerant regulations are also a consideration when
designing a heat pump system. In Europe the regulations are
getting tighter as the upper limit of allowed GWP (Global Warming
Potential) of refrigerants is lowered. Natural refrigerant possess
good properties, but safety needs to be taken into consideration
when choosing the right refrigerant for an application. Many of the
natural refrigerants are 昀氀ammable, but there are also low-GWP
options for 昀氀ammability class A1 (not 昀氀ammable) to provide more
security. These include for example R513A and a more exotic choice
R744 (CO2).
Figure 1: Temperature
lift affects the COP.
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