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1
Fuel System
Technology
Off-Base Fuel Systems for Gas Turbines
Project Engineering Department 1
2
Fuel System
Technology
Gas Turbine fuels
and Fuel Flexibility
Project Engineering Department 2
3
Fuel System
Project Engineering Department
Need for Fuel Flexibility- Fuel Availability
- Cost of Fuel
- National Interest
3
Gas Turbine Fuels:Gaseous Fuels:
1) Natural Gas
2) Refinery Gases
(High Hydrogen content)
3) Liquified Petroleum Gas
(LPG) [wet gases]
Project Engineering Department4
Gas Turbine Fuels:Liquid Fuels:
1) Distillates
- Naphtha, Kerosene,
Diesel Oils
2) Heavy Oils (ash forming)
- Petroleum Crude Oils,
Petroleum Residual Oils
Project Engineering Department 5
Fuel Gas System:1) On-Base fuel gas system - to regulate gas fuel flow based
on load of gas turbine
2) Off-Base fuel gas system - provides necessary fuel gas
conditioning as required by
on-base system
Project Engineering Department 6
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On-Base Gas Fuel
System requirements:1) The fuel gases shall conform to
spec. GT 10197, fuel gas
supply specifications
Project Engineering Department 8
The fuel gas properties
Which are controlled in off-base fuel gas system, as required by
GT
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1) Removal of particulate matter
- sand and clay
- Rust
- Construction debris
Particulate matter to be removed
down to 10 microns
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2) Ensuring 28 Deg. C super heat of fuel
gas at GT inlet
- above hydrocarbon dew point
- above moisture dew point
thus ensuring no condensate will form
in the GT on-base system
3) Prevention of hydrate formation in
fuel gas treatment system
4) Maintaining fuel gas pressure within
the allowable limits of gas turbine.
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Effect of contaminants
on GT operation:1) Particulates:
- Plugging of nozzles
- Erosion
- Deposition
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Effect of contaminants
On GT Operation: 2) Liquid condensates:
- Rapid excursions in firing
temperature and GT load
- Melting of hot gas paths
- Blow out (liquid water)
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Effect of contaminants
On GT Operation:3) Gas Hydrates are crystalline materials that are formed when free water is present in the gas which combines with gas compounds.
Hydrates can plug stagnant areas like
orifice plates, valves,instrumentation
etc. Maintaining fuel gas above water
Dew point temperature ensures prevention of hydrates formation.
Project Engineering Department 14
Main Processing equipment
for Fuel Gas Conditioning:1) Dry Gas Scrubber
2) Particulate filter
3) Filter Separator
4) Fuel gas heater (Electric/Steam)
5) Pressure Control Station
6) Fuel gas compressors
(if fuel gas is available at a lower pressure
than required by GT)
7) On-off valves, vent header, drain tanks etc.
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Various configurations of fuel gas conditioning systems
Involving simple particulate filter to most complex systems are engineered to meet the specific requirements of a project.
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If a gas compressor is used, if incoming gas supply pressure is too low to meet the gas turbine pressure requirements, advantage can be taken of heat of compression to avoid the cost of a gas super heater.
A surge vessel is required for on-line
change over of GT to alternate fuel
in case of tripping of fuel gas
Compressor.
Project Engineering Department 26
Special Considerations for Refinery gases:
1) If Refinery gas contains more than 5% by
volume of Hydrogen
- alternate startup fuel is required
- No flanged connections are permitted
within GT Hall
- GT requires inert gas purge/blocking
system. Nitrogen shall be made
available at two pressure s 2 Bar (g)
Project Engineering Department 27
Special Considerations for Refinery gases: (contd.)
and 30 Bar (g) for the purpose of
purging.
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Fuel Oil System:1) On-Base fuel oil system - to regulate fuel oil flow based
on load of gas turbine
2) Off-Base fuel oil system - provides necessary fuel oil
conditioning as required by
on-base system
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On-Base Fuel Oil
System requirements:1) The fuel oils shall conform to
spec. GT 10505, Gas Turbine Liquid
fuel specification.
Project Engineering Department 31
Fuel Oil Properties and
Contaminants that affect
the operation of GT and
Fuel Handling System
System requirements:
Project Engineering Department 32
Concerned fuel oil properties: - specific gravity (separation of impurities)
- viscosity (pumping, heating, atomization,
lubrication)
allowable max. limit 10 cst for Distilates
20 Cst for heavy oils
(for proper atomization)
Min. allowable viscosity is 1.8 Cst for proper
lubrication.
- flash point (explosion proofing requirement,
floating roof requirement for tanks)
- wax (plugging of filters)
Project Engineering Department 33
Concerned fuel oil contaminants: - solids (sand, rust, metallic oxides which
cause fouling of filters, control
systems, fuel pumps, flow dividers,
and fuel nozzles)
- water (presence of water along with bacteria
in oil will degrade oil creating slimy substance
which can plug the filters and jam the flow
divider)
which can cuse viscosity (pumping, heating, atomization,
lubrication)
allowable limit 10 cst for Distilates
20 Cst for heavy oils
(for proper atomization)
- flash point (explosion proofing requirement,
floating roof requirement for tanks)
- wax (plugging of filters)
Project Engineering Department 34
Concerned fuel oil contaminants: (contd.) presence of water can create emulsions which
will plug the filters.
water can also cause corrosion if left in flow
dividers and pumps.
- Trace Metals (Na, K, Va, Ca, Lead)
(hot-temperature corrosion, deposits)
which can cuse viscosity (pumping, heating, atomization,
lubrication)
allowable limit 10 cst for Distilates
20 Cst for heavy oils
(for proper atomization)
- flash point (explosion proofing requirement,
floating roof requirement for tanks)
- wax (plugging of filters)
Project Engineering Department 35
- Distillate fuel oils such as Naphtha and
kerosene are generally pure fuels require only
proper maintenance of storage tank and fine
filtration.
- Diesel fuels generally confirm to IS-1460
which has filterable dirt as high as 4 mg/100
ml, thus require a centrifuge to reduce the load
on filtration equipment provided.
- Ash forming fuels contain trace metal
components in addition to impurities found in
distillates in higher proportions, calling for fuel
washing.
will plug the filters.
water can also cause corrosion if left in flow
dividers and pumps.
- Trace Metals (Na, K, Va, Ca, Lead)
(hot-temperature corrosion, deposits)
which can cuse viscosity (pumping, heating, atomization,
lubrication)
allowable limit 10 cst for Distilates
20 Cst for heavy oils
(for proper atomization)
- flash point (explosion proofing requirement,
floating roof requirement for tanks)
- wax (plugging of filters)
Project Engineering Department 36
- The minimum allowable viscosity for GT is
1.8 Cst. Viscosity of oil below 1.8 Cst requires
dosing of additive Hitec-580.
Normally Naphtha fuel oil requires above
dosing.
- Trace metal vanadium can not be removed
by washing which requires dosing of an
inhibitor.
- Lead cannot be removed by any process.
Hence, shall be limited in the fuel oil
specification.
Project Engineering Department 37
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Off-Base Liquid Fuel Handling Systems:
1) Fuel Oil Unloading System
2) Fuel Oil Storage System
3) Fuel Oil Treatment System
4) Fuel Oil Forwarding System
5) Fuel Oil Dosing System
6) Fuel Oil Filtration System
7) Fuel Oil Drain System
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Steps to ensure minimize chances of contaminated oil unloaded at site:
1) Cleaning the tank wagon before loading by
supplier
2) Dedicated unloading tankers (or) trucks
3) Providing Coarse filter at unloading inlet of
tank
Project Engineering Department 44
Recommendations on Fuel Oil Storage System:
1) Two Storage tanks are recommended for each fuel. One tank is in use. The other tank is settling. After filling a tank or after adding additional fuel to it, a minimum of 24 hours settling should occur before taking fuel from the tank.
2) Fixed roof tanks are preferred. For volatile fuels fixed cum floating roof tanks are to be provided to avoid ingress of rain water.
3) Water and other sediments should be drained on a regular basis.
2) Dedicated unloading tankers (or) trucks
3) Providing Coarse filter at unloading inlet of
tank
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Such steps as draining water and sediment from the tank regularly, letting a tank settle for 24 hours before use and making sure that the drain is at the lowest point in the tank - All these can reduce problems related to fuel pump, flow divider and check valve and short filter life etc..
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