2.3 Pre-treatment of marine fuels
? Learning Objectives The main objectives of
this section are to make all engineers familiar
with,
?Pre-treatment of marine fuels,
?Design criteria,or problems related to settling
and service tanks,
?Draining of settling tanks,
?Preheating,Separation,purifier and clarifier.
? Sludge and sludge handling.
2.3 Pre-treatment of marine fuels
? Design criteria,or problems related to
settling and service tanks.
– Draining and cleaning,It is most important
to examine and clean settling and service
tanks regularly for sludge,If satisfactory
fuel is transferred into a tank containing
sludge,waxy sludge may be thrown down
from it as a result of a seeding action by the
micro-crystals already present,
2.3 Pre-treatment of marine fuels
– Draining and ventilation,Tanks containing
heated fuel oil should be vented to a safe position
outside the engine room and as in the case of all fuel
oil tanks,the end of the vent pipes should be fitted
with wire gauze diaphragms,Openings in the
drainage systems of tanks containing heated fuel oil,
should be located in spaces where no accumulation of
fuel vapors at temperatures close to the flash point
can occur,There should be no source of ignition in
the vicinity of these vent pipes or near the openings in
the drainage systems
2.3 Pre-treatment of marine fuels
– Settling tanks,Normally,two settling tanks should be
fitted,each having sufficient capacity of 24 hours
normal service consumption,The 24 hours capacity is
provided to enable some natural gravitational
separation of free water to take place,and to enable
the temperature of the fuel to stabilize prior to pre-
combustion treatment,Both settling and service tanks
should have sloping bottoms,to enable easy draining
from the tanks,In addition it is preferable with
perforated plates fitted parallel to the tank bottoms to
keep possible sediment in place,
2.3 Pre-treatment of marine fuels
– Remember,It is of great importance to establish
routines for draining the settling tanks to prevent
build up of water and sludge,which may cause
problems due to the separation process.
– Service tank,Design features of the service tanks
should be similar to those of settling tanks,
Overflow from the service tanks should be led to
the bottom of the settling tanks,or preferable,
300mm above the bottom and away from the
outlets,High and low suction pipes in service tanks
should be located above water and sludge drains,
Figure 2.1
Preheating
2.3 Pre-treatment of marine fuels
– Service systems,Service systems provide the final
supply to the engine and should be designed to give
a flow rate proportionate to the maximum fuel
consumption,Pumps for purification and engine
fuel oil service systems must be capable of
operating with the highest temperature of the fuel
to be handled,Pressurized fuel systems are
preferable when operating diesel engines on high
viscosity fuels,When using high viscosity fuels
requiring a preheat temperature far above 100℃,
there is a risk of boiling or foaming if an open
return pipe is used,and especially if there is water
present in the fuel,
2.3 Pre-treatment of marine fuels
– Pressurized fuel system,In a pressurized fuel system,
the fuel oil is gravity fed,or drawn by a feed pump,
from the daily service tank,through a course strainer
and a flowmeter to a mixing or return tank or pipe,
From this tank a booster pump is delivering the fuel
through preheater,viscosity controller and a fine filter
to the engine fuel racks,About 30% of the fuel
supplied by the booster pumps are consumed by the
engine,while the rest is circulated back to the return
tank or pipe,through a return line,Normally there are
two of each pump types and duplex strainers.
2.3 Pre-treatment of marine fuels
– Return tank/pipe:
?Has a dual purpose,First,to ventilate vapors
from the oil,Second,to serve as a reservoir when
or if,switching from operation on heavy fuel oil to
operate on diesel oil.
?Should have a capacity of 10 to 15 minutes of
normal fuel consumption.
?Normal temperature range would be 110 to 140℃
?Pressure in order of 3 to 4 bars,
2.3 Pre-treatment of marine fuels
– Fuel oil preheaters:
Each preheater should be capable of
heating the fuel oil from the service tank
temperature to 150℃ at full flow rate,
This is considered sufficient for fuels
with viscosities up to 700 cst at 50℃,
Steam preheaters are preferred to
electrical,which have a tendency to give
carbonation,
2.3 Pre-treatment of marine fuels
? Heating elements and their thermostats must never
become uncovered under normal operation and should
be situated below the tank outlets,Heating arrangements
demand careful attention to avoid operational problems,
because failure to provide heating surfaces of correct
capacity can result in inadequate fuel temperatures and
inability to pump the fuel,The line heater output should
not exceed 1.5 Watt/cm,but to avoid local cracking of the
fuel,metal surfaces should not exceed 220℃, These
requirements clearly stress the need for large heating
surfaces,
Figure 2.2 Separation
2.3 Pre-treatment of marine fuels
? The fuel to be separated in a separator is a
mixture of two or more phases,The dispersed
phase may be solids or a liquid,To enable
separation,the phases must not be completely
soluble in each other,The phases must be of
different density to enable separation,Choice
of equipment depends on the concentration of
solids and particle size of the feed.
Table 2.3 Component affection by separation:
Components
Not affected,
Components
Slightly
affected,
Components
Strongly
reduced,
Density Nickel
Viscosity CCAI
Flash point Pour
point
Micro carbon
Residue Sulphur
Vanadium
Asphaltenes
Total sediment
Ash
Calcium
Water
Sodium
Aluminum
Silicon
Iron
Magnesium
2.3 Pre-treatment of marine fuels
? Purifiers,Multiple disc type of purifiers,as
made by Alfa Laval,Westfalia is the most
common on vessels of today,It is self cleaning
and fitted with 50 to 150 thin cone shaped,
pressed steel discs,carried on a central conical
distributor.
At least two purifiers should be installed in the
fuel oil pre-treatment system,Due to the recent
tendency to increase the density of fuel oils,it is
advisable to install purifiers able to cope with
fuels having a density above 1000kg/m2 at 15℃.
Figure 2.2
2.3 Pre-treatment of marine fuels
? Traditional purifier:
Traditional purifiers are designed for fuel oil
densities of up to 991 kg/m at 15℃,with fuel oil
temperature at inlet of purifier at 98℃, These
types of purifiers have a gravity disc for the
important purpose of removing possible water
from the fuel,A number of gravity discs are
supplied with the purifiers,Each of these discs
have different internal diameters,all correctly
identified by the relative density clearly marked
on the disc.
2.3 Pre-treatment of marine fuels
? The density of the fuels decides which
gravity disc should be used,Generally the
gravity disc with the largest internal
diameter,which does not cause a broken
water seal,is the most suitable one.
? The importance of fitting the right gravity
disc can not be overstressed,This has
become increasingly important,with the
higher fuel densities now a reality.
2.3 Pre-treatment of marine fuels
? Latest generation purifier:
The new type of purifiers are specifically
designed to deal with fuel oil densities of up to
1010 kg/m2 at 15℃ and viscosities up to 700
cst at 50℃, Instead of using the gravity disc,
the new purifiers use a water transducer
which responds to changes in the water
content of the cleaned oil,This causes stop in
the fuel supply to the purifiers and the water
to be discharged from the purifier bowl,
2.3 Pre-treatment of marine fuels
? Purifier/clarifier,The main difference between
purifiers and clarifiers is that clarifiers do not have
the water seal,If traditional purifiers are used,they
should be designed so that they can be operated
independently of each other as purifier and clarifier,
All purifiers should be of the same size and be capable
of individually handling the maximum quantity of fuel
oil,The clarifier following the purifier in series
operation,will give an additional improvement to the
separation result and also act as a safety net,If the
interface of the preceding purifier,for any reason,has
moved into the disc stack,It will not act as a safety net
or any water present,
Figure 2.4
Figure 2.5
2.3 Pre-treatment of marine fuels
?Mspx303 features:
? Separation of oil,water and solids
simultaneously from oil sludges of varying
composition and density without adjustment.
? Integral paring disc pumps,for continuous
discharge of separated oil and water,
? Separate outlets for oil,water and sludge.
Figure 2.6
2.3 Pre-treatment of marine fuels
?MSPX303 benefits:
? Substantial savings in total sludge
handling costs.
? Maximum separation of water prior to
discharge to the collecting tank.
? Maximum recovery of oil for direct use
in boiler or for incinerator disposal.
? Automatic start and stop sequence.
? Learning Objectives The main objectives of
this section are to make all engineers familiar
with,
?Pre-treatment of marine fuels,
?Design criteria,or problems related to settling
and service tanks,
?Draining of settling tanks,
?Preheating,Separation,purifier and clarifier.
? Sludge and sludge handling.
2.3 Pre-treatment of marine fuels
? Design criteria,or problems related to
settling and service tanks.
– Draining and cleaning,It is most important
to examine and clean settling and service
tanks regularly for sludge,If satisfactory
fuel is transferred into a tank containing
sludge,waxy sludge may be thrown down
from it as a result of a seeding action by the
micro-crystals already present,
2.3 Pre-treatment of marine fuels
– Draining and ventilation,Tanks containing
heated fuel oil should be vented to a safe position
outside the engine room and as in the case of all fuel
oil tanks,the end of the vent pipes should be fitted
with wire gauze diaphragms,Openings in the
drainage systems of tanks containing heated fuel oil,
should be located in spaces where no accumulation of
fuel vapors at temperatures close to the flash point
can occur,There should be no source of ignition in
the vicinity of these vent pipes or near the openings in
the drainage systems
2.3 Pre-treatment of marine fuels
– Settling tanks,Normally,two settling tanks should be
fitted,each having sufficient capacity of 24 hours
normal service consumption,The 24 hours capacity is
provided to enable some natural gravitational
separation of free water to take place,and to enable
the temperature of the fuel to stabilize prior to pre-
combustion treatment,Both settling and service tanks
should have sloping bottoms,to enable easy draining
from the tanks,In addition it is preferable with
perforated plates fitted parallel to the tank bottoms to
keep possible sediment in place,
2.3 Pre-treatment of marine fuels
– Remember,It is of great importance to establish
routines for draining the settling tanks to prevent
build up of water and sludge,which may cause
problems due to the separation process.
– Service tank,Design features of the service tanks
should be similar to those of settling tanks,
Overflow from the service tanks should be led to
the bottom of the settling tanks,or preferable,
300mm above the bottom and away from the
outlets,High and low suction pipes in service tanks
should be located above water and sludge drains,
Figure 2.1
Preheating
2.3 Pre-treatment of marine fuels
– Service systems,Service systems provide the final
supply to the engine and should be designed to give
a flow rate proportionate to the maximum fuel
consumption,Pumps for purification and engine
fuel oil service systems must be capable of
operating with the highest temperature of the fuel
to be handled,Pressurized fuel systems are
preferable when operating diesel engines on high
viscosity fuels,When using high viscosity fuels
requiring a preheat temperature far above 100℃,
there is a risk of boiling or foaming if an open
return pipe is used,and especially if there is water
present in the fuel,
2.3 Pre-treatment of marine fuels
– Pressurized fuel system,In a pressurized fuel system,
the fuel oil is gravity fed,or drawn by a feed pump,
from the daily service tank,through a course strainer
and a flowmeter to a mixing or return tank or pipe,
From this tank a booster pump is delivering the fuel
through preheater,viscosity controller and a fine filter
to the engine fuel racks,About 30% of the fuel
supplied by the booster pumps are consumed by the
engine,while the rest is circulated back to the return
tank or pipe,through a return line,Normally there are
two of each pump types and duplex strainers.
2.3 Pre-treatment of marine fuels
– Return tank/pipe:
?Has a dual purpose,First,to ventilate vapors
from the oil,Second,to serve as a reservoir when
or if,switching from operation on heavy fuel oil to
operate on diesel oil.
?Should have a capacity of 10 to 15 minutes of
normal fuel consumption.
?Normal temperature range would be 110 to 140℃
?Pressure in order of 3 to 4 bars,
2.3 Pre-treatment of marine fuels
– Fuel oil preheaters:
Each preheater should be capable of
heating the fuel oil from the service tank
temperature to 150℃ at full flow rate,
This is considered sufficient for fuels
with viscosities up to 700 cst at 50℃,
Steam preheaters are preferred to
electrical,which have a tendency to give
carbonation,
2.3 Pre-treatment of marine fuels
? Heating elements and their thermostats must never
become uncovered under normal operation and should
be situated below the tank outlets,Heating arrangements
demand careful attention to avoid operational problems,
because failure to provide heating surfaces of correct
capacity can result in inadequate fuel temperatures and
inability to pump the fuel,The line heater output should
not exceed 1.5 Watt/cm,but to avoid local cracking of the
fuel,metal surfaces should not exceed 220℃, These
requirements clearly stress the need for large heating
surfaces,
Figure 2.2 Separation
2.3 Pre-treatment of marine fuels
? The fuel to be separated in a separator is a
mixture of two or more phases,The dispersed
phase may be solids or a liquid,To enable
separation,the phases must not be completely
soluble in each other,The phases must be of
different density to enable separation,Choice
of equipment depends on the concentration of
solids and particle size of the feed.
Table 2.3 Component affection by separation:
Components
Not affected,
Components
Slightly
affected,
Components
Strongly
reduced,
Density Nickel
Viscosity CCAI
Flash point Pour
point
Micro carbon
Residue Sulphur
Vanadium
Asphaltenes
Total sediment
Ash
Calcium
Water
Sodium
Aluminum
Silicon
Iron
Magnesium
2.3 Pre-treatment of marine fuels
? Purifiers,Multiple disc type of purifiers,as
made by Alfa Laval,Westfalia is the most
common on vessels of today,It is self cleaning
and fitted with 50 to 150 thin cone shaped,
pressed steel discs,carried on a central conical
distributor.
At least two purifiers should be installed in the
fuel oil pre-treatment system,Due to the recent
tendency to increase the density of fuel oils,it is
advisable to install purifiers able to cope with
fuels having a density above 1000kg/m2 at 15℃.
Figure 2.2
2.3 Pre-treatment of marine fuels
? Traditional purifier:
Traditional purifiers are designed for fuel oil
densities of up to 991 kg/m at 15℃,with fuel oil
temperature at inlet of purifier at 98℃, These
types of purifiers have a gravity disc for the
important purpose of removing possible water
from the fuel,A number of gravity discs are
supplied with the purifiers,Each of these discs
have different internal diameters,all correctly
identified by the relative density clearly marked
on the disc.
2.3 Pre-treatment of marine fuels
? The density of the fuels decides which
gravity disc should be used,Generally the
gravity disc with the largest internal
diameter,which does not cause a broken
water seal,is the most suitable one.
? The importance of fitting the right gravity
disc can not be overstressed,This has
become increasingly important,with the
higher fuel densities now a reality.
2.3 Pre-treatment of marine fuels
? Latest generation purifier:
The new type of purifiers are specifically
designed to deal with fuel oil densities of up to
1010 kg/m2 at 15℃ and viscosities up to 700
cst at 50℃, Instead of using the gravity disc,
the new purifiers use a water transducer
which responds to changes in the water
content of the cleaned oil,This causes stop in
the fuel supply to the purifiers and the water
to be discharged from the purifier bowl,
2.3 Pre-treatment of marine fuels
? Purifier/clarifier,The main difference between
purifiers and clarifiers is that clarifiers do not have
the water seal,If traditional purifiers are used,they
should be designed so that they can be operated
independently of each other as purifier and clarifier,
All purifiers should be of the same size and be capable
of individually handling the maximum quantity of fuel
oil,The clarifier following the purifier in series
operation,will give an additional improvement to the
separation result and also act as a safety net,If the
interface of the preceding purifier,for any reason,has
moved into the disc stack,It will not act as a safety net
or any water present,
Figure 2.4
Figure 2.5
2.3 Pre-treatment of marine fuels
?Mspx303 features:
? Separation of oil,water and solids
simultaneously from oil sludges of varying
composition and density without adjustment.
? Integral paring disc pumps,for continuous
discharge of separated oil and water,
? Separate outlets for oil,water and sludge.
Figure 2.6
2.3 Pre-treatment of marine fuels
?MSPX303 benefits:
? Substantial savings in total sludge
handling costs.
? Maximum separation of water prior to
discharge to the collecting tank.
? Maximum recovery of oil for direct use
in boiler or for incinerator disposal.
? Automatic start and stop sequence.
