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8/20/2019 Cox Reduction by HAM
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Humid Air MotorTechnology for green profits
8/20/2019 Cox Reduction by HAM
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2 Humid Air Motor – Technology for green profits 3Humid Air Motor – Technology for green profits
Adding Ecology to Economy
In general today, modern marine diesel engines are
capable of meeting the requirements of the first and
second stages of the MARPOL 73/78 Annex VI
regulations – commonly called IMO Tiers I and II –
using only on-engine and in-cylinder modifications.
On the 1st january 2016, however, the NOx limitation of
IMO Tier III will come into force and is so stringent that
additional devices will be needed (see figure 1).
Moreover, there are already regional regulation such
as those in Norway and Sweden which reward
every kg of NOx not emitted. In response to these
regulations, ship owners have an incentive to adopt
NOx reduction systems on their fleets.
operating costs due to sea water usage, decreased
lube oil consumption, very low maintenance costs and
a very high availability factor.
Consequently, following its philosophy of environment-
ally friendly engine development, MAN Diesel & Turbo
now offers the HAM system. The company’s decision
to offer this technology is based, in particular, on the
economics of the HAM system, which create favourable
conditions for profitable engine operation.
In recent years, global and local regulations covering
exhaust gas emissions from heavy duty medium
speed diesel engines have become progressively more
stringent. They cover all applications i.e. power gene-
ration and propulsion systems on land and at sea.
In particular, emissions of oxides of nitrogen (NOx ) have
become a major issue.
Since the 1980s, emissions reduction has been a major
development aim at MAN Diesel & Turbo and has
resulted in the progressive introduction of exhaust gas
optimised engines.
HAM
A widely acclaimed technology for reducing NOx
pollution from diesel engines is the “Humid Air Motor”
(HAM). This technology is able to reduce NOx formation
by up to 65%. In the HAM system the turbocharged
combustion air is saturated with water vapour produced
aboard the ship using sea water and engine heat.
This lowers the temperature peaks in the combustion
chamber, which are normally the main reason for NO x
formation. HAM is characterised by extremely low
Throughout its history the diesel engine has always maintained its status as
the most efficient system for converting fuels into mechanical energy, and this
situation is expected to continue for the foreseeable future. This assertion applies
in all areas of application:the automotive sector, off-highway equipment, and in
marine propulsion and electrical power generation.
rpm [1/min]
Figure 1: NO x limit curve of IMO
Figure 2: Cutting NO x with humid air – schematic heat release diagram
N O
x [ g / k W h ]
18
16
14
12
10
8
6
4
2
0
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200
Cutting NOx with humid air
NOx generating peak
No HAM
Temperature
increaseinside the
cylinderwithout HAM
HAM
Temperature increaseinside the cylinder
with HAM
NOx forms exponentionallyover this
temperature
Crank angle
IMO Tier 1 IMO Tier 2 IMO Tier 3
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4 Humid Air Motor – Technology for green profits
MAN B&W Diesel
5Humid Air Motor – Technology for green profits
Humid Air Motor Technology
When the water vapour is mixed with the compressed
charge air, two mechanisms can be identified:
n Increase of the specific heat capacity of th e mixture
n Dilution of the charge air: water vapour replaces air
The quantity of water (in g/kg dry air) which can be
injected into the inlet air depends on the temperature
and the pressure of the mixtu re.
As shown in the diagram in figure 3, when the air tempe-
rature rises so does the quantity of water it i s possible to
vaporise.
In this area HAM has an outstanding advantage, since
it uses the heat of the engine to bring the saltwaterup
to temperature. No external energy source is needed.
In addition to the heat of the charge air after the
turbocharger, in many applications heat from the engine
coolant and exhaust gases can be introduced into the
charge-air to increase its capacity to absorb moisture.
With the HAM method a NOx reduction level of 40%
is achieveable without using additional heating of the
intake air and a level of 65% when additional heat is
introduced from the engine coolant or exhaust gases.
H2O against NOx
It is well known that the cooling effect of water can
prevent NOx formation during the combustion process.
Well proven methods employing water to reduce NOx
are fuel-water emulsification and humidification of inlet
air (HAM principle).
HAM principle
Over 90% of NOx formation results from combustion
temperature peaks. The principl e of HAM is to humidify
the inlet air in order to lower these temperature peaks.
The HAM system hu midifier produces saturated air.
The ability of water to decrease the formation of
NOx is exploited in the same way as with fuel water
emulsification, but the quantity of water added is much
higher and the heat for water vaporisation is taken
from the compressed air after the turbocharger or
other engine-related heat sources.
XH2O [g/kg dry air]
R e
l a t i v N O
x E m
i s s
i o n
[ % ]
C h a r g e
A i r T e m p e r a
t u r e
[ ° C ]
Figure 3: NO x -Humidity Trend
100
80
60
40
20
0
100
80
60
40
20
0
0 20 40 60 80 100 120
NOx-Humidity Trend
Adiabatic With additional heat
Satura tion L in e ( 2, 5 b ar) N Ox-H um id i ty Trend
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6 Humid Air Motor – Technology for green profits
MAN B&W Diesel
7Humid Air Motor – Technology for green profits
Compressor
Water Filling
Humidification
tower
Water circuit
Catch Tank Heat exchanger
Engine
Bleed-off
TurbineHot compressed air
Humidified
and cooled air
How HAM works
The functional principle of HAM is quite simple.
Figure 4 illustrates the HAM Process:
Filtered saltwater is pumped to the catch tank
to replace evaporated and purged loop water.
The HAM system itself cycles water in a loop
between the catch tank and the Humidification tower
(“HAM vessel”)
A heat exchanger between the catch tank and the
HAM vessel heats the saltwater using an on-engine
heat source.
Three injection stages spray the heated saltwater
into the charge air.
At the same time the compressed charge air
from the exhaust turbocharger bypasses the
charge air cooler and is piped into the HAM
vessel air inlet. Flowing through the HAM vessel,
the charge air absorbs the water. Due to the high
loop capacity of the water all particles (incl. salt)
fall back into the catch tank and, over a certain
salinity level, are purged. Thus no salt from the
saltwater can enter the engine.
To avoid tiny droplets reaching the combustion
chamber, the humidified charge air passes through
a high-performance mist catcher at the end of the
humidification tower.
This humidification leads to saturated charge air
which is fed into the engine.
1
2
5
6
4
3
7
Humid Air Motor Technology
Figure 4: Engine with HAM principle
1
2
3
4
5
6
7
Proven in Practice
To prove the theoretical results of HAM technology,
field tests under real conditions were carried out.
Marine
Viking Line took the decision to equip all four engines
aboard its vessel “Mariella” with the HAM system. This
car ferry crosses daily between Helsinki and Stockholm.
The main characteristics of the vessel are:
n Length: 177 m, Breadth: 29 m, Weight: 37,800 t
n 2200 passengers, 540 vehicles
n 4 engines: 12 PC2-6.2 each rated 5,750 kW
at 500 rpm
The system was installed on main engine number one
in July 1999 (all engines were subsequently equipped
with HAM) and since then it has been operating with
seawater. The installation was carried out without inter-
rupting vessel operation.
One of Viking Line’s requirements was to be able
to switch from the standard intake air system with
charge air cooler to HAM with the engine running. This
requirement was met by using butterfly valves.
The ship-owner now considers that this condition
is no longer required since the charge air cooler is
no longer necessary. In case of emergency, without
HAM and without charge air cooling, it has been
verified that available power is still 50% to 60%.
System installation in the engine room is illustrated in
figure 5.
References
Figure 5: HAM Installation on “Mariella”
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8 Humid Air Motor – Technology for green profits 9Humid Air Motor – Technology for green profits
Since July 1999 the systems have logged about
100,000 operating hours without any major problems.
The following list presents the results over that time:
n Low operating & maintenance costs confirmed
n Extended service intervals
n No trace of water in lubeoil
n Decreased lube oil consumption
n No corrosion
n Cleaner engine (deposits are “washed” away)
n No need for turbocharger washing
n Decrease of cylinder and valve temperatures
Stationary
On Corsica, one PC3 engine (12 MW) was equipped
with HAM to test it under power plant conditions.
The following data are available on this configuration:
n Specific fresh water consumption: 410 g/kWh
The following results were confirmed during the test:
n NOx = – 65% is confirmed
n 650 mg/Nm3 CO limit
Figure 6: NO x decrease on engine number 1 on board “Mariella”
N
O x
[ p p m
]
1600
1400
1200
1000
800
600
400
200
0
40% 50% 60% 70% 80% 90% 100%
NOx decrease
Load
With HAM Without HAM
Field Experience
Marine applications
Viking Li ne, M/S M ariella
Passenger ferry
S.E.M.T. Pielstick 4x12VPC 2.6 HFO
5,7 MW per engine
68% emissions reduction
Nyholmen AS M/V Kvannoy
Purser Trailer
MAN 1X 16V28/32A MDO 3.9 MW
62% emissions reduction
Plant applications
Electricité De France, Lucciana plant
Power Plant
S.E.M.T. Pielstick 1x 18VPC3 HFO
12 MW
65% emissions reduction
Diesel United, Japan, Tohoku Plant
Power Plant
S.E.M.T. Pielstick 1X 12VPC4.2 HFO
10.4 MW
45% emissions reduction
(60% beforemodifications of engineparameters)
References
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10 Humid Air Motor – Technology for green profits 11Humid Air Motor – Technology for green profits
Conclusion
Engine operation optimisation
Addition of water vapour to the charge air has a
beneficial effect:
n Exhaust gas temperatures and valve temperatures
are lower, leading to a decrease in thermal loading.
Simple operation
The use of HAM is simple as shown by experience
on the “Mariella”:
n Simultaneous start for both HAM and engine.
n 15 minutes before stopping the engine: engine at
idle speed and water circulation shut off in order to
dry the air system.
System reliability
The system is intrinsically self-controlled without any
need of a load-related control loop. The system is
stable and responsive.
n Longevity: Even after 100,000 hours of operation,
HAM has demonstrated consistently high effective-
ness in NOx reduction.
n Stable: No abrupt changes in engine operating
parameters if water circulation is shut-off.
n Responsive: favourable response to load varia-
tions.
The HAM s ystem is thus an economically and eco-
logically viable way to effectively reduce NO x while
optimising engine operation.
To meet the challenge of reducing oxides of nitrogen
during diesel engine combustion, the HAM system is
an efficient solution with the following advantages:
Efficient NOx reduction
The targeted NOx reduction of 65% was confirmed
during HAM usage on the car ferry “Mariella” and a
power station on Corsica.
Very low operating costs
Seawater may be used as the consumable for the
HAM system, meaning operating costs are very low.
The use of an additive to prevent calcium deposit does
not significantly increase operating costs. The heat
to vaporise the water can be taken from on-engine
sources i.e. engine coolant and exhaust gases, without
affecting the ship’s overall energy recovery levels. Even
with no additional input of heat, a NO x reduction level
of 40% is achieved at nominal load.
Best practice to fulfill regulations from an economic
standpoint
All three case studies showed that under the specific
conditions of existing regulations, and taking account
of the balance of investment to operating costs, HAM
always demonstrated extremely short amortisation
periods.
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