CIMAC Congress - Schiff & Hafen

Monday, 14 June
Tuesday, 15 June
Thursday, 17 June
Wednesday, 16 June
by developing a foresighted calculation and by practical tests onboard
ships. The presented investigation of the deposit formation is, in
part, described as initiating with an induction phase. This phase is
immediately followed by continual deposit growth until it reaches
an equilibrium phase of growth and decay. Deposit growth is
influenced by numerous factors. These factors include but are not
limited to time, combustion environment, composition of the
materials that form the deposits, and physical conditions at the
location of formation. Engine efficiency can only be restored by
removal of existing deposits, or more preferably by avoiding the
induction phase itself. Avoiding the induction phase is best
accomplished by precluding the initial formation of a liquid surface
layer of deposit precursor material. The simulation as well as the field
trials will show that keeping the exhaust gas system clean will avoid
efficiency losses of the turbocharger system and improve
environmental sustainability. A more complete combustion achieved
by chemical fuel treatments will reduce deposit formation
significantly. By example, only a clean turbocharger will avoid
efficiency losses, which result into a fuel benefit of approximately 2
% or more depending on the equipment. These concepts will be
proven by new innovative theoretical calculations and substantial
field evidence. There are several known cleaning procedures for the
turbocharger equipment. However, the optimum, most cost effective
and most convenient method of protecting the equipment is to
avoid fouling.
Exhaust gas heat recovery on large engines
– potential, opportunities, limitations
I. Vlaskos, P. Feulner, A. Alizadeh, I. Kraljevic,
Ricardo Deutschland, Germany
Improving efficiency is a major development trend in all applications
of energy conversion. This applies to large engines especially, since
the ecological benefit of reduced greenhouse gas emissions is going
hand in hand with the economic advantage of reduced fuel cost. In
recent years conversion of exhaust gas heat to useful work has become
a focus of development efforts in many branches of combustion
engine work. This paper looks at the potential, which can be realised
by staged processes, the opportunities for utilisation on large engines
and some pertinent limitations. To this end a hypothetical large
engine is conceived and some options for exhaust heat recovery
systems are calculated for application on this engine. Analysis is
limited to operation at full load and rated speed since the positive
impact of any improvement of efficiency is greatest there and
furthermore many large engines in energetic installations (power
stations) are routinely operating at these conditions. Since steam and
ORC systems are currently en vogue and widely covered in a great
number of publications this paper will concentrate on gas cycles.
Next generation of flexible and reliable
SCR-systems
C. Gerhart, H.-P. Krimmer, Alzchem Trostberg GmbH,
Germany,
B. Schulz, NIGU Chemie GmbH, Germany,
O. Kroecher, Paul Scherrer Institute, Switzerland, D.
Peitz, Paul Scherrer Institute, Germany,
Th. Sattelmayer, P. Toshev, Lehrstuhl fuer Thermodynamik,
Technical University of Munich, Germany,
G. Wachtmeister, A. Heubuch, Lehrstuhl fuer Verbrennungskraftmaschinen,
Technical University of
Munich, Germany
Driven by upcoming tighter emission regulations for internal
combustion engines selective catalytic reduction (SCR) technology
had become state of the art. With SCR lowest NOx levels could be
reached. SCR had been adapted to mobile onroad applications from
heavy duty [1] down to smaller engines in passengers cars. Now first
installations also for larger, nonroad or stationary engines have been
realized. The integration of SCR with AdBlue R as standardized
aqueous urea solution is already in operation in a variety of onroad
applications [2]. Still there are reliability and operation problems to
overcome concerning solid residues, mixing into the exhaust gas
flow and efficient decomposition upstream or directly on the SCRcatalyst.
Also for nonroad engines in many cases standard AdBlue R
as ammonia precursor does not fulfil requirements in the various
applications. Of interest would be a better ammonia release potential
per litre, less water in the liquid solution and in some cases an
improved stability concerning freezing at the lower end and less
decomposition and consequently less vapour pressure at the higher
end of the ambient temperature conditions. The direct use of
ammonia gas from pressure vessels has already been banned in
mobile onroad applications due to critical safety issues while
handling and in the supply chain. Throughout the search of a safe,
liquid ammonia precursor, guanidinium salts came into the focus
of further investigations [3]. These high-N containing and non-toxic
substances could become a new class of molecules as ammonia
precursor in a variety of formulations depending on the application.
Especially guanidinium formate has a extremely high solubility of
more than 6 kg in 1 litre water (equal to > 0,52 kg NH 3
/l compared
to 0,2 kg NH 3
/l of AdBlue R ). Guanidinium formate could be used
in formulations with urea and water depending on the application:
without urea as highly concentrated solution with an elevated
freezing point but high stability up to 100°C or as an eutectic
mixture with urea (e.g. 41% guanidinium formate, 16% urea)
resulting in a freezing point below -30°C. Investigations on the
hydrolysis have shown that this guanidinium salt can be completely
decomposed to ammonia on a titania hydrolysis catalyst above
200°C. Due to the low water content of the liquid solution about
50% less energy is required for complete heating, evaporation and
decomposition to ammonia compared to AdBlue R . The main
difference compared to aqueous urea is the slightly elevated
optimum temperature for complete decomposition. A complete,
reliable and independently working system of such a next generation
SCR should include a small and compact ammonia generator
containing a hydrolysis catalyst operating under well defined
conditions. A simple bypass reactor unit for the decomposition of
the liquid precursor to ammonia gas could have advantages e.g. in
availability of ammonia and be more independent of the exhaust or
engine conditions. The complete decomposition to ammonia
would occur under controlled conditions. Specifications and
investigations on such a type of ammonia generator will be
presented.
Attenuation of low-frequency exhaust
noise from combustion engines
S. Frederiksen, C. Ammitzbo, Silentor A/S, Denmark,
B. B. Jessen, Delta, Denmark
There is an increased awareness about disturbance caused by lowfrequency
exhaust noise from all types of combustion engines.
Especially large, 2-stroke engines are characterized by a low ignition
frequency which increases the risk of prominent noise at this
frequency and at higher harmonics. When the frequency of a sound
wave is low, there will be less attenuation at transmission through
walls, windows, etc. In addition, low frequencies are associated with
relatively long wavelengths that may coincide with distances between
walls, whereby strong, standing waves can be set up. This increased
awareness includes, not only audible sound of low frequency, but
also infra-sound (below around 20 Hz), which cannot be heard, but
No. 3 | 2010 | Ship & Offshore
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