cox reduction by ham

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Humid Air MotorTechnology for green profits



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



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



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”




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


Plant applications

Electricité De France, Lucciana plant

Power Plant

S.E.M.T. Pielstick 1x 18VPC3 HFO

12 MW


Diesel United, Japan, Tohoku Plant

Power Plant

S.E.M.T. Pielstick 1X 12VPC4.2 HFO

10.4 MW


(60% beforemodifications of engineparameters)

References




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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