武汉理工大学：《船舶辅机》课程教学资源（PPT课件，英文版）2.3 Pre-treatment of marine fuels

.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 e and service tanks Draining of settling tanks .B Preheating Separation, purifier and clarifier. o Sludge and sludge handling

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 • 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 – 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 he 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 – 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 tanke: 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

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 Pre-treatment of marine fuels Preheating HEATING 怪 →|→

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 100C 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 – 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

e.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 – 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: o 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 be110to140℃ Pressure in order of 3 to 4 bars

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'C at full flow rate This is considered sufficient for fuels with viscosities up to 700 cst at 50C Steam preheaters are preferred to electrical, which have a tendency to give carbonation

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