Heavy Fuel Oil(HFO ) System in a HFO power Plant is the core system included fuel tank,fuel pump,booster module or boosting system . Heavy fuel oil system include feeding and boosting fuel system. The function of the Heavy fuel oil (HFO) system is to store and supply fuel through pipelines to the fuel combustion chamber where it can be mixed with air, vaporized, and burned to produce energy. Fuel pumps draws the fuel from the tanks through fuel lines and delivers it through a Fuel filter,Fuel pump and Fuel injector to the cylinder combustion chamber.
Component used in Heavy fuel system (HFO):
- HFO Storage tank
- Transfer Pump
- Buffer Tank
- HFO Separator
- day tank
- HFO Supply Pump
- Auto Backwash Filter
- Quick Shutoff Valve
- Flow Meter
- Booster Module
- To Engine
General Flow Chart :
HFO Storage Tank:
HFO Storage/Fuel storage tank used to store fuel from shipment. Steam circulates around the tank to keep the temperature around 50 degree Celsius. It ensue settling of water mixed with heavy fuel oil.
HFO Transfer Pump:
Screw type pump used (Normally twin screw pump) used to pump untreated high viscous heavy fuel oil into the buffer tank from storage tank.
HFO Buffer Tank:
Heavy fuel oil (HFO) from the storage tank pump into the buffer tank where it heated. Water and heavy impurities mixed with the fuel settling down to the bottom of buffer tank.
Usually rotary or centrifugal type purifier used. Purifier separate water and solid sludge usually Carbon deposit,Sulfur,ash etc. The separator should correctly adjusted for the specific gravity of the fuel.
All fuel oil separators available should be operated continuously. Fuel flow rate and temperature control also are important. Experience has shown that the correct temperature for centrifuging high viscosity fuels is in the region of 95 to 98 degrees Centigrade. If excessive sludging occur, it gives evidence of incompatibility, the fuel should be separated at the slowest possible rate using purifiers in parallel.
HFO Service Tank/Day tank:
To ensure fuel feed to the main engine, the separated heavy fuel oil (HFO) is pumped into the service tank (day tank. Heating coils in both tanks ensure an even temperature between 167°F and 194°F (75°C and 90°C) which keeps the oil pump-able.
Heavy Fuel Oil (HFO) Supply Pump:
A screw pump used as feed pump in a HFO power plant to ensure uniform pressure in the fuel supply line.
Heavy Fuel Oil (HFO) Automatic Filter:
Automatic backwash filter filtrated purified heavy fuel oil (HFO) to ensure there is no foreign particle in the fuel.
Quick Shut Off Valve:
A quick shut off valve installed in the heavy fuel oil supply line to ensure quick cut of fuel in an emergency period. Pressurized air used to operate quick shut off valve. Air torque 10Nm to 15Nm (5 to 7 bar) used.
Flow Meter (Common):
A common flow meter also installed to calculate the fuel flow to the booster module to calculate the fuel consumption. In return line also flow meter installed. From those flow meter reading fuel consumption calculated.
The fuel comes from day tank have a high viscosity. To inject the fuel in the cylinder need viscosity same as diesel. So there is a arrangement in viscosity module to reduce the viscosity in particular value by heating fuel(generally by steam). A set of equipment installed in a series ensure filtrated and desired viscosity. The equipment used are HFO & LFO changeover valve,Fuel mixing tank,Flow meter,Booster pump, Fuel duplex filter,Heater (Steam heater),Viscosity controller,Cooler etc.
From the booster module filtrated Heavy Fuel Oil (HFO) enter to the engine combustion chamber. During this path fuel passes through high pressure fuel pump and fuel injection valve/fuel injector.
A plunger type high-pressure fuel pump includes a plunger reciprocated in a cylinder. A fluid pressurizing chamber of the pump has a chamber with a capacity that changes with reciprocation of the plunger.
Fuel injector used to inject fuel into the combustion chamber. It measures the fuel, atomized, vaporized the fuel and mixed with compressed air. Fuel pump deliver fuel to the injector at high pressure. The needle lifted when the pressure reaches at setting value(MAN B&W Engine 650 bar) ,fuel injected to the combustion chamber.