FUEL TECHNOLOGY AS APPLICABLE IN MARINE ENGINEERING PRACTICE INCLUDING EMISSION CONTROL AREAS

1. CURRENT STATUS OF
FUEL TECHNOLOGY
DHIRENDRA BIHARI

2. Low NOx tuning, increased compression ratio,
delayed injection timing, changed exhaust
valve timing, and Exhaust gas recirculation

3. NOx reducing technology-Direct water injection, Humidification,
Emulsified fuel.
Selective catalytic reduction- abatement strategies for tackling
NOx and Sox. Technology for 2 stroke and 4 stroke engines.

4. Smoke reduction measures.
Common rail technology-advantages, Injection pressure factor in
smoke emission, Smoke Reduction Using Common Rail System,
Steam Injection to Reduce NOx,

5. COMMON RAIL DIRECT FUEL INJECTION IS A MODERN VARIANT OF
DIRECT FUEL INJECTION SYSTEM FOR PETROL AND DIESEL ENGINES.
ON DIESEL ENGINES, IT FEATURES A HIGH-PRESSURE (OVER
1,000 BAR OR 100 MPA OR 15,000 PSI) FUEL RAIL FEEDING
INDIVIDUALSOLENOID VALVES, AS OPPOSED TO LOW-PRESSURE FUEL
PUMP FEEDING UNIT INJECTORS (OR PUMP NOZZLES). THIRD-
GENERATION COMMON RAIL DIESELS NOW
FEATURE PIEZOELECTRIC INJECTORS FOR INCREASED PRECISION, WITH
FUEL PRESSURES UP TO 3,000 BAR (300 MPA; 44,000 PSI

6. Annex VI of MARPOL deals with restricting the amount of harmful emissions from
ships’ main propulsion system and provides guidelines for substances such as Sox
and NOx.
Several technologies have been introduced to reduce the level of harmful emissions
in ship’s exhaust system.
We have enumerated 10 such different technologies and systems used onboard
ships to comply with MARPOL for reducing marine pollution.
Reducing NOx emission
The presence of NOx in marine engine’s exhaust emission is due to high
combustion temperature which reacts with nitrogen in the air supplied for
combustion.
Following are the methods to reduce NOx emission from ship:
1. Humid Air Method: In this method, water vapour is mixed in the combustion air
before supplying it to the cylinder. Air from the T/C blower is passed through a cell
that humidifies and chills the hot air taking moisture from the cooling water until air
saturation is achieved. Generally saline sea water is utilized in this method by
heating it with jacket water and turbo charger heat, and the left over brine is
disposed back to the sea. This method can achieve reduction of NOx by 70-80%.

7. 2. Exhaust Gas Re circulation (EGR): As the name suggests, some amount of
engine exhaust gases are send back to the scavenge space to mix up with the air
to be supplied to cylinder for combustion. This reduces the oxygen content of the
air and hence reduces formation of NOx.
3. Water Injection and Water emulsion: In this method, water is added to
reduce the temperature of combustion leading to low NOx emission. In water
emulsion, fuel is blended with water and in water injection a separate fresh water
injector is mounted in the cylinder head which injects water. This method has a
drawback of increasing the specific fuel oil combustion with reduction in NOx by
only 20-45%.
4. High Scavenge Pressure and Compression Ratio: With high scavenge
pressure and compression ratio, large amount of air can be introduced inside the
cylinder to lower combustion temperature and NOx emission.
5. Selective Catalytic Reduction: The SCR is the most efficient method to
reduce NOx emissions from ships (up to 90-95% of reduction). In this method, low
sulphur fuel oil is used and exhaust temperature is maintained above 300 deg C.
The exhaust gas is mixed by water solution of urea and then it is passed through
catalytic reactor. The only disadvantage of SCR is its expansive installation and
operating cost.
6. Two Stage Turbocharger: ABB’s latest two stage turbocharger can reduce
the exhaust temperature in the intercoolers and also the NOx content in the
emitted exhaust. Read more about 2 stage turbochargers here.

8. 7. Engine Component Modification: It is better to design an engine which has a
property to reduce the NOx formation during combustion process rather than
investing on expensive secondary measures. Integration of slide valve type fuel
injector with almost zero sack volume eliminates any chance of fuel dripping and
after burning, leading to cylinder temperature and NOx formation.
New designs like Green Ultra long stroke engine from MAN (GME series) with
reduced mean piston speed gives more time for excess air and proper combustion
to lessen NOx formation.
Reducing SOx Emission
SOx or sulphur oxides are formed during combustion process in the engine
because of presence of sulphur content in the fuel.
Following are the methods and technologies used to reduce sulphur emission from
marine engines.
8. Use of Low sulphur fuel oil: It is expensive but most commonly used method
to comply with Annex VI of MARPOL while entering emission controlled Area or
ECA.
9. Exhaust Gas Scrubber Technology: The exhaust gas from the engine is
passed through the scrubber tower where a liquid is showered over it. Fresh water
blended with caustic soda (NaOH) is used as a scrubbing liquid which reduces the
SOx to 95%. The scrubbing water is then sent to a water treatment effluent
emulsion breaking plant after which it can be discharged overboard.

9. 10. Cylinder Lubrication: Good quality cylinder lubrication along with efficient
control systems such as Pulse or Alpha lubrication systems can neutralise the
sulphur in the fuel and reduce SOx emissions from the engine.
Water injection or water flooding refers to the method in the oil industry
where water is injected into the reservoir, usually to increase pressure and thereby
stimulate production. Water injection wells can be found both on- and offshore, to
increase oil recovery from an existing reservoir.
Water is injected (1) to support pressure of the reservoir (also known as voidage
replacement), and (2) to sweep or displace oil from the reservoir, and push it
towards a well.
Normally only 30% of the oil in a reservoir can be extracted, but water injection
increases that percentage (known as the recovery factor) and maintains the
production rate of a reservoir over a longer period.
Waterflooding began accidentally in Pithole, Pennsylvania by 1865.
Waterflooding became common in Pennsylvania in the 1880s.
Sources of injected water
Any and every source of bulk water can be, and has been, used for injection. The
following sources of water are used for recovery of oil:

10. Produced water is often used as an injection fluid. This reduces the potential of
causing formation damage due to incompatible fluids, although the risk of scaling
or corrosion in injection flowlines or tubing remains. Also, the produced water,
being contaminated with hydrocarbons and solids, must be disposed of in some
manner, and disposal to sea or river will require a certain level of clean-up of the
water stream first. However, the processing required to render produced water fit
for reinjection may be equally costly.
As the volumes of water being produced are never sufficient to replace all the
production volumes (oil and gas, in addition to water), additional "make-up" water
must be provided. Mixing waters from different sources exacerbates the risk of
scaling.
Seawater is obviously the most convenient source for offshore production facilities,
and it may be pumped inshore for use in land fields. Where possible, the water
intake is placed at sufficient depth to reduce the concentration of algae; however,
filtering, deoxygenation and biociding is generally required.
Aquifer water from water-bearing formations other than the oil reservoir, but in the
same structure, has the advantage of purity where available.
River water will always require filtration and biociding before injection.

11. Filters
The filters must clean the water and remove any impurities, such
as shells and algae. Typical filtration is to 2 micrometres, but really depends on
reservoir requirements. The filters are so fine so as not to block the pores of the
reservoir. Sand filters are a common used filtration technology to remove solid
impurities from the water. The sand filter has different beds with various sizes of
sand granules. The sea water traverses the first, coarsest, layer of sand down to
the finest and to clean the filter, the process is inverted. After the water is filtered it
continues on to fill the de-oxygenation tower. Sand filters are bulky, heavy, have
some spill over of sand particles and require chemicals to enhance water quality. A
more sophisticated approach is to use automatic selfcleaning backflushable screen
filters (suction scanning) because these do not have the disadvantages sand filters
have.
The importance of proper water treatment is often underestimated by oil companies
and engineering companies. Especially with river-, and seawater, intake water
quality can vary tremendously (algae blooming in spring time, storms and current
stirring up sediments from the seafloor) which will have significant impact on the
performance of the water treatment facilities. If not addressed correctly, water
injection may not be successful. This results in poor water quality, clogging of the
reservoir and loss of oil production.

12. De-oxygenation
Oxygen must be removed from the water because it promotes corrosion and
growth of certain bacteria. Bacterial growth in the reservoir can produce
toxic hydrogen sulfide, a source of serious production problems, and block the
pores in the rock.
A deoxygenation tower brings the injection water into contact with a dry gas
stream (gas is always readily available in the oilfield). The filtered water drops into
the de-oxygenation tower, splashing onto a series of trays, causing dissolved
oxygen to be lost to the gas stream.
An alternative method, also used as a backup to deoxygenation towers, is to add
an oxygen scavenging agent such as sodium bisulfite and ammonium bisulphite.
Water injection pumps
The high pressure, high flow water injection pumps are placed near to the de-
oxygenation tower and boosting pumps. They fill the bottom of the reservoir with
the filtered water to push the oil towards the wells like a piston. The result of the
injection is not quick, it needs time.
Water injection is used to prevent low pressure in the reservoir. The water replaces
the oil which has been taken, keeping the production rate and the pressure the
same over the long term.

13. The various options for noxious exhaust emission reduction,
Wärtsilä suggests:
1. The first choice is engine tuning modifications that can achieve up to 39 per cent
reductions in NOx emission levels compared with those of standard engines in 1990.
2. For further NOx reductions, separate water injection is considered the most
appropriate solution; the technique has proved its ability on the test bed to reduce
emission levels by some 60 per cent compared with today’s standard engines.
3. Exhaust gas after-treatment by SCR has proved an effective solution in reducing NOx
by 90 per cent or more, despite the special difficulties imposed by using high sulphur
fuel oils.
4. Requirements for lower emissions of SOx are most favourably met by using fuel oils
with reduced sulphur contents. Although SOx reduction by exhaust gas after-treatment is
technically feasible, the de-sulphurization process inevitably imposes a disposal problem,
which may not be acceptable for shipping.
5. Carbon monoxide and HC can, if necessary, be reduced by an oxidation catalyst
housed within an SCR reactor.
6. Particulate reduction, with the engine running on heavy fuel, poses a challenge.
Technical solutions are available (e.g. electrostatic precipitators) but involve either great
space requirements or great expense.
7. Particulate emissions are reduced by 50–90 per cent, however, through a switch to
distillate fuel oils.

14. LNG reliquifaction plant principle, Diesel engine with a reliquifaction
plant for LNG ships.

15. Introduction
Liquefied Natural Gas (LNG) is transported at near atmospheric pressure and low
temperatures (approx. -160 °C) in carriers over long distances. During the voyage a
proportion of the LNG is vaporized by heat ingress in the cargo containment system. The
cargo tanks are well insulated with, typically 270mm cryogenic insulation, but some heat
inleak producing boil-off gas (BOG) is inevitable. Typical values are about 0.1 to 0.15% of
the full contents per day, which over a 21 day voyage, becomes a significant amount.
Hitherto, ships have employed gas compression and use of the boil-off gas as fuel for the
propulsion systems. Until now LNG carriers have been equipped with steam turbines
powered by heavy fuel oil (HFO) and/or LNG BOG. However, designers of new larger ships
are seeking more economic propulsion solutions which offer further economic advantages
when combined with of a BOG re-liquefaction facility on-board LNG carriers.

16. Process Route Selection
For small liquefaction units and in particular, ship mounted units, several issues become
dominant in the decisions taken during process selection. These include:
-Previous experience in such technologies.
-Rapid start/stop and flexibility.
-Plant simplicity.
-Ability to operate during voyages with pitch and roll.
-Space on board may be limited.
-Low cost.
-Easy installation.
-Safe – low amounts of hazardous inventory in plant.
Each of these pushes the designer to a closed loop nitrogen cycle. In selecting optimum
process conditions, there are several parameters that are important including:
•BOG liquefaction pressure (the higher the better)
•BOG temperature (the lower the better)
•Gas composition.
Unfortunately, the more one compresses the BOG, the more expensive the compressor
capital cost, and the warmer the BOG gas becomes. So the first two parameters work
against each other. The third parameter, is determined by the cargo being transported.
Therefore, a simple, single stage BOG compressor was selected for the TGE process. The
refrigeration that must be provided to cool, condense and sub-cool the LNG is thus needed
at mostly below -50oC and down to -170 oC

17. . Since the BOG pressure is low, the condensing is done over a narrow temperature range
which makes the liquefaction cycle, thermodynamically, less efficient. This can be seen in
Figure (2), below, where the temperature differences are high at the cold end (bottom
left) of the heat exchangers carrying out the liquefaction, with 30 – 35 Oc differences near
the cold end.
Given the above, it becomes necessary to design a nitrogen cycle as efficiently as possible
in order to provide the most advantageous economics. Therefore, the experience of
nitrogen cycles of the 1970s and 1980s has been revisited and further optimized to
provide a modern solution to BOG re-liquefaction.

19. The combination of reliquefaction with dual-fuel engines offers a flexible system where it
is possible to switch between fuels depending on fuel prices. The state of the art
propulsion engines are efficient and not all BOG can be utilized in the engine in the
different operating modes. Instead of burning excessive gas in the gas combustion unit,
the gas can be liquefied and returned to the tanks.
Advantages:
•Flexible fuel system
•Optimized fuel costs
•Increased cargo quantity delivered
•More profitable freight contracts
The Laby®-GI will replace the conventional BOG compressor upstream the reliquefaction
plant. After the 1st or 2nd stage intercooler, at 5-6 bar, BOG can be partly – or fully
diverted to the reliquefaction system.
The remaining gas will be compressed in the last three compressor stages before being
injected into the engine.

20. The system covers the following operating modes:
1. Compress BOG for utilization in the engine
2. Compressor (low pressure) feed all the BOG to the reliquefaction system
3. Compressor feeding the engine and excessive gas is liquefied in the reliquefaction plant
When the ME-GI engine is running in gas mode, the required BOG is sent directly by the
compressor to the engine, thereby bypassing the reliquefaction system. If any, excessive
gas is liquefied in the reliquefaction mode. Alternatively the engine is running in HFO
mode and the BOG is liquefied in the reliquefaction plant. In ballast voyage the operator
can choose to run the vessel on HFO and liquefying the BOG in order to keep the cargo
tanks cold or utilize the BOG for fueling the engine. The reliquefaction plant can be
designed for full or reduced capacity.
Boil-off reliquefaction plant
The BOG with vapour header temperature is preheated in a heat exchanger upstream the
compressor to utilize the cold duty in the BOG. This configuration ensures that the heat of
compression can be rejected through cooling water in the intercoolers. The BOG is
preheated in heat exchanging with the high pressure nitrogen taken downstream the
nitrogen compander. Downstream the compressor the BOG is cooled at this pressure to
about minus 160°C in a cryogenic plate-fin heat exchanger. This ensures condensation of
hydrocarbonsto LNG.
A special feature of the Hamworthy Gas Systems reliquefaction processes are that not all
the nitrogen content has been condensed at minus 160°C for LNG with large content of
nitrogen. Nitrogen gas is compressed in a compander unit (3-stage centrifugal compressor
and single expander on a common gear box).

22. After the 3rd stage cooler the stream is split into two different streams. One stream is
used to preheat the BOG in a separate heat exchanger (preheater) and the other is led to
the “warm” part of the cryogenic heat exchanger. After heating the BOG, the two streams
are mixed together again, and reintroduced into the cold box core. In the cryogenic
heat exchanger the Nitrogen is pre-cooled and then expanded to almost compressor
suction pressure. The gas leaves the expander at temperature below minus 160°C and
returned to the “cold” part of the cryogenic heat exchanger. The cold nitrogen continues
through the “warm” part of the cryogenic heat exchanger.
Laby®-GI compressor
Handling of cryogenic natural gas with suction temperatures below minus 160°C in the
pressure range of 10 to 50 barg (1.0 to 5.0 MPa g) is a common application in many
onshore and offshore LNG or LPG facilities worldwide. The Laby®compressor design with
its unique labyrinth sealing technology has proven it’s second to none performance in this
field.
The Laby®-GI fuel gas compressor (see figure 3) is designed for the same low suction
temperatures as the Laby®. Only difference is the extension of the pressure range up to
300 bar. Therefore the three oil-free labyrinth sealed, low pressures stages are
complemented with two stages of piston ring sealing systems, comparable to the proven
API 618 design. All five stages are combined in a vertical crank gear and form the six-
crank Laby®-GI fuel gas compressor. As a result of mass balancing, the compressor will be
free from vibrations and moments - ideal for offshore installation. Careful thermal design
and material selection means that it is not necessary to pre-cool the compressor or to
heat the gas prior to start-up. The rugged design in combination with the well proven
equipment stands for longest meantime between overhaul (MTBO) for this and related
applications.

24. Electronically controlled camshaft-less low speed diesel engines, RT
flex and ME engines overview

37. Current version of ISO 8217 2010 fuel standards. Catfines,
Sodium/Vanadium presence-limitations in FO.

38. MARINE FUEL OIL, ITS ISO STANDARD, ANALYSIS AND CORRECTIVE
ACTION
ISO 8217 specifies the requirement for petroleum fuels for use in marine diesel
engines and boilers prior to appropriate treatment before use. The most widely
used specification is still ISO 8217:2005 i.e. the third edition. Fourth edition of ISO
8217 is ISO 8217:2010.
SALIENT FEATURES:-
•It provides for better fuel quality
•Improvement of the safety levels in shipboard operation
•Reduced engine damage and consequential risks
It specifies 4 categories of distillate fuel, one of which is for diesel engines for
emergency purpose, and 6 categories of residual fuel.
New features added in distillate fuel are:-
•Lubricity:- Fuel has to possess lubricity if the sulfur content is less than 0.05% to
avoid fuel pump wear down
•Oxidation stability:- This minimizes addition of bio-diesel to reduce storage risk
on board vessel.
New features added in Residual fuel are:-
•CCAI: - It avoids uncharacteristic density viscosity relationship leading to ignition
problem.

39. Sodium: - It limits any sea water contamination and restrict high temperature
corrosion.
New features added to both distillate and residue :-
•Acid number:- It minimizes damage to diesel engine fuel injection for high acidic
compounds.
•H2S :- Provides improvement margin for safety by reducing risk of exposure to
ship board crew.
THIS H2S FEATURE HAS COME IN FORCE FROM 1ST JULY 2012. AND THIS
BRINGS THE FIFTH EDITION OF ISO 8217 i.e. ISO 8217:2012. IT BECAME
AVAILABLE ON 15TH AUGUST 2012. IT ADDS TEST METHOD FOR H2S
CONTENT.
Changes in 2010 edition from 2005 edition:-
•Some new grades were added where as some old were removed
•Sulfur limit was excluded as now they are controlled by statutory requirement
•Ash limit value for residual fuels were reduced
•Vanadium limit for RMG 380 increased
•Vanadium for all other grades were reduced
•Cat-fines limit was reduced from 80 to 60 ppm

40. Fuel analysis is carried out in shore laboratories. They check for all the
characteristics as prescribed in the ISO standard. Following are some of the
properties which can be found outside the limit and their corrective action:-
1. Density:- Max limit is 991 kg/m3 ( for RMG grade) and 1010 kg/m ( for RMK
grade). Increased density will affect the centrifuge operation. It will be ineffective in
water separation. It will affect the engine performance.
If received bunker density is more than the specified limit inn RMG grade
then its better to de-bunker it unless vessel has ALCAP purification system.
2. Viscosity:- At 50 deg Celsius common viscosity for residual fuel is 180 cst or
380 cst, but it can go up to 700 cst. It affects pump ability, preheating,
settling/separation, atomization and combustion. Increased viscosity is not a
problem unless vessel has got sufficient heating arrangements. Analysis report will
state the correct amount of temperature to which the fuel should be heated to
maintain the viscosity as prescribed the engine manufacturers.
3. Sulfur:- It is now guided by the statutory requirements. If the value comes
more than maximum specified by the regulation, bunkers will need to be
debunkered. However if the sulfur content comes too low then correct grade of
CLO will have to be used to avoid cold corrosion or alkaline deposits on the piston
top land.

41. 4. Cat-fines:- Max limit is 60 ppm. The main problem with cat-fines are that they are not
always evenly distributed and sometimes are accumulated in sediments. They are very difficult
to remove as they are attracted to water droplets. To minimize the cat-fines key feature is to
remove them by separation in separators. For that always maintain the purifiers according to
manufacturer's recommendation. Ensure that separation is being carried out efficiently by
minimizing the feed and optimizing the temperature. Never ever by-pass the fine filters given
in the fuel line. It is better to keep one extra clean set and change them at regular interval.
Keep the fuel at above 70 deg in the settling tank and drain settling and service tanks at
regular intervals.
5. Water:- It is allowed up to 0.5% V/V for residual fuel and 0.3% for distillate fuel. Fresh
water contamination will lead to corrosion damage to fuel pumps and injectors. How ever
serious problems arises if the water content is sea water. It becomes more serious because of
sodium content in sea water. Sodium along with vanadium in 1:3 can cause high temperature
corrosion. It is recommended to remove the water content by centrifuge separation, giving
sufficient setting time in settling tanks, Sufficient heating in settling tanks and by frequent
draining of the settling/service tanks.
6. Ash:- Recommended value is 0.15% m/m for residual fuels. High ash content causes
deposits on the piston surface, exhaust valves, turbocharger blades and boiler tubes. During
combustion metal content is converted into solid ash which after certain temperature become
partly fluid thus adhering to the all parts stated above causing corrosion problems. Ash
removal is recommended by frequent cleaning of the parts. Turbochargers should be regularly
dry washed or wet washed. Boilers should be frequently soot blown and cleaned with water.

44. Catalytic Fines are Hard, abrasive crystalline particles of alumina, silica, and/or
alumina silica that can be carried over from the fluidic catalytic cracking process of
residual fuel stocks. Particle size can range from sub-micron to greater than sixty (60)
microns in size. These particles become more common in the higher viscosity
marine bunker fuels.
CATALYTIC HYDROCRACKING
Some refineries use catalytic hydro cracking as a supplementary operation to catalytic
cracking. Catalytic hydrocracking is similar to catalytic cracking because it uses a
catalyst, but the reactions take place under a high pressure of hydrogen.
Hydrocracking further upgrades heavy aromatic stocks to gasoline, jet fuel and gasoil
material. The heaviest aromatic fractions of a cat cracker and vacuum gasoil (VGO) are
the normal feedstocks for a hydrocracker. Hydrocracking requires a very high
investment, but makes the refinery yield pattern nearly independent from the crude
oil feed.
VISBREAKING
The feedstock of a visbreaker is the bottom product of the vacuum unit, which has an
extremely high viscosity. In order to reduce that viscosity and to produce a
marketable product, a relatively mild thermal cracking operation is performed. The
amount of cracking is limited by the overruling requirement to safeguard the heavy
fuel stability. The light product yield of the visbreaker (around 20%) increases the
blendstock pool for gasoil.

45. ALCAP
Fuel oils with densities above 991 kg/m3 at 15°C are available on the market and can be
purified, for example, with the ALCAP system, which allows fuel oil densities up to 1010
kg/m3 at 15°C. Fuel oil is continuously fed to the separator. The oil flow is not interrupted
when sludge is discharged.
The ALCAP basically operates as a clarifier. Clean oil is continuously discharged from the
clean oil outlet. Separated sludge and water accumulate at the periphery of the bowl.
Sludge (and water) is discharged after a pre-set time. If separated water approaches the
disc stack (before the pre-set time interval between two sludge discharges is reached),
some droplets of water start to escape with the cleaned oil. A water transducer,
installed in the clean oil outlet, immediately senses the small increase of the water content
in the clean oil. A signal from the water transducer is transmitted to a control unit and
changes in water content are measured. Increased water content in the cleaned oil is the
sign of reduced separation efficiency for not only water, but for the removal of solid
particles, as well. When the water content in the cleaned oil reaches the pre-set trigger
point, the control unit will initiate an automatic discharge of the water that has
accumulated in the bowl through the water drain valve.
In summary, water is discharged either with the sludge at the periphery of the bowl (Figure
6a): separated water does not reach the disc stack in the pre-set time between sludge
discharges, or through the water drain valve (Figure 6b): separated water reaches the
disc stack before the pre-set time between sludge discharges.