PuK - Process Technology & Components 2024

Leading article
Efficiency and quality
Prof. Dr.-Ing. Eberhard Schlücker
Electricity is going to be our preferred
form of energy in the future
since it directly or indirectly
replaces fossil fuels in everything
from electric cars to homes and the
chemical industry. CO 2
and hydrogen
are the magic bullets for indirect
replacement.
Hydrogen is universal in application
and produced using electricity,
while CO 2
is harmful to our climate
but will be an important raw material
in the future. However, this means
that we will need five to eight times
more electricity or 10 to 16 times
more electricity from wind and solar
than today. This would only be possible
if photovoltaic and wind power
plants become far more efficient.
Otherwise we will not have enough
room, and resistance from the population
is often encountered as well.
We therefore have to import energy.
Ammonia is no doubt the best
option since its hydrogen content is
high (110 Kg/m 3 ) and it only requires
positive pressure of about 10 bar
for transportation. The technology
for recovering the hydrogen is available
and relatively efficient. Australia
is promising $1.50 per kilogram of
hydrogen and the price is currently
$2.00. Presumably this will be stored
in ammonia. It will however cost
more than that by the time it gets to
us. Investments need to be made in
production abroad, the construction
of cargo ships, transportation, port
receiving systems and the pending
development of distribution structures
in Europe. Since ammonia is
toxic, one cannot expect to pump it
through pipelines or to use it in municipal
structures. Gas distribution
networks in Germany are therefore
being converted to hydrogen. Hydrogen
currently costs € 4.55/kg in Germany.
According to a publication of
the Wuppertal Institute, hydrogen
can be produced at lower cost in
Germany compared to importing it
in the form of ammonia. This is true
in particular when the required electricity
is produced domestically using
photovoltaics (currently approx.
8.5 cents/KWh, thus € 2.83/kg). We
should therefore produce as much
hydrogen as possible and sensible in
Europe. This should allow us to meet
our energy needs in conjunction
with imports. However, we still have
a long way to go and may experience
occasional electricity shortages until
we get there. There is at least some
doubt whether energy imports will
always proceed smoothly due to political
changes. We should therefore
turn this threat into an opportunity
by developing products that are better
than anything comparable in the
world. Efficiency in all facets and durability
are the keys to success. We
need to build machinery and equipment
that outperform all others in
terms of efficiency and service life.
In the examination of process
technology, heat suggests itself as
the focal point for assessing the efficiency
of machinery (pumps, compressors
etc.), equipment, electricity,
materials and overhead.
Heat energy and heating
equipment
Heat is a physical state that we need
for technical applications and in our
private life. Unfortunately, heat cannot
be transported – or only in mobile,
extremely well insulated heat
storage vessels (costly). Heat should
therefore be consumed where it is
produced and one should always
strive to maintain it at a high energy
level where it is used. This means
that heat dissipation losses should be
minimised by good insulation or that
waste heat should be utilised as far
as possible. Heat flows can also be
upgraded through compression, vapour
recompression or heat pumps,
thereby raising them to higher temperatures.
In process technology, this means
using heat cascades or heat upgrading
methods, for example:
1) The cold heat flow cools the warm
flow, the warm flow cools the hot
flow, and so forth! The hot flow
can either be transformed back
into electricity using a Carnot battery
or the residual heat can be
used for heating and returned to
upgrading.
2) If a flow of warm water is available
that cannot be used any more, this
could be provided to neighbours
for heating or upgraded to reach
a level that makes it usable again
(for example, reheating from this
level or, in case of gases or steam,
compression or vapour recompression).
3) If a hot flow is available that cannot
be used any more, it should
be stored in a mobile heat storage
vessel or transformed into electricity
using a Carnot battery
4) When heating as well as cooling
are required, both can be produced
using a heat pump or the
heat can be used for cooling generation,
producing a warmer flow.
Pumps and compressors
The choice of a pump depends on
the type of process used to produce
a certain product. A rotary pump is
the best choice when this meets the
project requirements since it is costeffective
and robust. However, its efficiency
factor is poor in case of low
flow rates or large control ranges.
This raises the question of costs. The
costs for a conveying task with a pressure
increase of 10 bar, a flow rate
of 10 m 3 /h and an efficiency factor of
10 % are €19,352 when an electricity
price of 0.285 cents/KWh is assumed
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PROCESS TECHNOLOGY & COMPONENTS 2024