FUEL TREATMENT SYSTEM FOR AN ENGINE AND A METHOD USING THE SYSTEM

Abstract

A fuel treatment system for an engine includes at least two centrifugal separators for cleaning fuel oil for an engine, at least two variable feed pumps for supplying fuel oil to be cleaned to the centrifugal separators, respectively, and at least two separator control units configured to control the operation of the centrifugal separators and the speed of the variable feed pumps, thereby controlling the flow rate of fuel oil to be cleaned to the separators. The system further includes a system control unit, other than the separator control units, configured for receiving information from a unit in the fuel treatment system that is arranged downstream of the centrifugal separators or from an engine arranged to use the fuel that is treated by the system, and for sending operational requests to the separator control units based on the received information.

Claims

1. A fuel treatment system for an engine comprising: at least a first and a second centrifugal separator for cleaning fuel oil for an engine; at least a first and a second variable feed pump, wherein the first feed pump is arranged for supplying fuel oil to be cleaned to said first centrifugal separator and the second feed pump is arranged for supplying fuel oil to be cleaned to said second centrifugal separator; a first separator control unit configured to control the operation of the first centrifugal separator and the speed of the first variable feed pump to control the flow rate of fuel oil to be cleaned to the first centrifugal separator; a second separator control unit configured to control the operation of the second centrifugal separator and the speed of the second variable feed pump to control the flow rate of fuel oil to be cleaned to the second centrifugal separator; and a system control unit, other than the first and second separator control units, configured for receiving information from a unit in the fuel treatment system that is arranged downstream of said centrifugal separators, or from an engine arranged to use the fuel that is treated by the fuel treatment system, and for sending operational requests to the first and second separator control units based on said received information.

2. The fuel treatment system according to claim 1, wherein the operational requests to the separator control units comprise instructions on how to operate said first and second variable feed pumps and instructions on how to operate said centrifugal separators.

3. The fuel treatment system according to claim 1, wherein the operational requests comprise at least one request selected from requesting a specific separator throughput, requesting start of at least one of said centrifugal separators, requesting stop of at least one of said centrifugal separators or requesting discharge of at least one of said centrifugal separators.

4. The fuel treatment system according to claim 1, wherein the system control unit is further configured to receive return information from said first and second separator control units related to the operational status of the centrifugal separators.

5. The fuel treatment system according to claim 4, wherein said return information comprises information on the operational status of the centrifugal separators, the maximum capacity of centrifugal separators, the current throughput of the centrifugal separators, the temperature of the separator rotor and/or vibrations of the separator frame of each of said centrifugal separators.

6. The fuel treatment system according to claim 1, wherein at least one unit in the fuel treatment system that is arranged downstream of one or more of said centrifugal separators comprises a tank to which the fuel treated by at least one of the centrifugal separators is sent.

7. The fuel treatment system according to claim 1, wherein at least one unit in the fuel treatment system that is arranged downstream of said centrifugal separators comprises a fuel conditioning module arranged to boost the properties of the fuel in terms of temperature, viscosity and/or flow rate just prior to injection into the engine.

8. The fuel treatment system according to claim 1, wherein the system control unit is further configured to receive information from at least a unit in the fuel treatment system upstream at least one of said centrifugal separators and for sending operational requests to the separator control units based on said received information.

9. The fuel treatment system according to claim 1, wherein said engine is located on a ship for propulsion of the ship.

10. The fuel treatment system according to claim 1, wherein said information is the fuel consumption of the engine, said fuel consumption is an actual fuel consumption measured with a flow meter, or said fuel consumption is an assumed fuel consumption based on a set value.

11. A method for treating fuel oil for an engine comprising the steps of: providing a fuel treatment system for an engine and a fuel oil to be cleaned; supplying said fuel oil to be cleaned to at least a first and a second centrifugal separator using at least a first and a second variable feed pump, respectively; cleaning said fuel oil in the centrifugal separators to provide a clean oil phase; controlling the operation of the centrifugal separators and the speed of the variable feed pumps using at least a first and a second separator control unit, respectively; and sending information from at least one unit in the fuel treatment system downstream of said centrifugal separators to a system control unit or from an engine arranged to use the fuel that is treated by the system; and sending operational requests to the separator control units based on said received information using said system control unit.

12. The method according to claim 11, further comprising sending return information from said separator control units related to the operational status of the centrifugal separators to said system control unit.

13. The method according to claim 11, further comprising sending information from at least a unit in the fuel treatment system upstream of said centrifugal separators, and wherein the operational requests to the separator control units are further based on said received information.

14. A method for controlling a process for treating fuel oil for a diesel engine comprising the steps of: receiving information at least from a unit in a fuel treatment system that is downstream of at least one separator for cleaning said fuel oil; sending operational requests to at least two separator control units based on said received information, said operational request comprising instructions on how to operate at least two variable feed pumps for supplying fuel oil to be cleaned to at least two centrifugal separators and instructions on how to operate the centrifugal separators.

15. The method according to claim 14, further comprising receiving information from at least a unit in the fuel treatment system upstream of said centrifugal separators and wherein the operational requests sent to said separator control units are also based on such received information.

16. The fuel treatment system according to claim 2, wherein the operational requests comprise at least one request selected from requesting a specific separator throughput, requesting start of at least one of said centrifugal separators, requesting stop of at least one of said centrifugal separators or requesting discharge of at least one of said centrifugal separators.

17. The fuel treatment system according to claim 2, wherein the system control unit is further configured to receive return information from said separator control units related to the operational status of the centrifugal separators.

18. The fuel treatment system according to claim 3, wherein the system control unit is further configured to receive return information from said separator control units related to the operational status of the centrifugal separators.

19. The fuel treatment system according to claim 2, wherein at least one unit in the fuel treatment system that is arranged downstream of one or more of said centrifugal separators comprises a tank to which the fuel treated by at least one of the centrifugal separators is sent.

20. The fuel treatment system according to claim 3, wherein at least one unit in the fuel treatment system that is arranged downstream of one or more of said centrifugal separators comprises a tank to which the fuel treated by at least one of the centrifugal separators is sent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] FIG. 1 shows a schematic drawing of an embodiment of a system comprising one centrifugal separator.

[0078] FIG. 2 shows a schematic drawing of a further embodiment of a system comprising two separators.

[0079] FIG. 3 shows a schematic drawing of a further embodiment of a system comprising two separators and also two settling tanks.

DETAILED DESCRIPTION

[0080] The method and the system according to the present disclosure will be further illustrated by the following description with reference to the accompanying drawings. For ease of description and facilitating understanding, although the invention relates to a fuel treatment system comprising a plurality of centrifugal separators, description is first made with reference to FIG. 1 of a fuel treatment system comprising a single centrifugal separator. The various system components and their functions are the same for a single separator and a plural separator system, except as required adaptation to a plural centrifugal separator fuel treatment system, e.g. the control unit receiving information and sending operational request to two or more separators instead of one. Thus, the features, functions and configurations described with reference to FIG. 1 for a first separator, a first variable feed pump and a first separator control unit, etc., are the same as for a second separator, a second variable feed pump, a second separator control unit, etc.

[0081] FIG. 1 shows a schematic drawing of an embodiment of a fuel treatment system 1 consisting of a settling tank 2, a first feed pump 3, pre-heater 4, separator 5, service tank 6, an additional feed pump 7, a fuel conditioning module (FCM) 9 and one engine 10.

[0082] Fuel for the engine in bunkered in settling tank 2. This fuel may be heavy fuel oil (HFO) or any other fuel suitable for a diesel engine. The tank 2 may have a slanted tank bottom that facilitates the collection and removal of cat fines and prevent them from being stirred up in rough weather. Fuel oil to be cleaned is supplied to a centrifugal separator 5 by means of variable feed pump 3. The system further comprises a pre-heater 4 for regulating the temperature of the fuel oil to be cleaned. The fuel oil is in this embodiment initially heated to about 98 C. by heater 4. The centrifugal separator 5 is of a kind known in the art for cleaning fuel oil on board a ship. The separator 5 may thus comprise a rotor that forms within itself a separation chamber in which centrifugal separation of the fuel oil takes place during operation. The separation chamber is provided with a stack of frusto-conical separation discs to facilitate effective separation of the fuel oil. The stack of truncated conical separation discs are examples of surface-enlarging inserts and are fitted centrally and coaxially with the rotor. During operation of the separator 5, fuel oil to be separated is brought into the separation space. Depending on the density, different phases in the fuel oil is separated between the separation discs 1. Heavier component, such as a water phase and a sludge phase, move radially outwards between the separation discs, whereas the phase of lowest density, such as the clean oil phase, moves radially inwards between the separation discs and is forced through an outlet arranged at the radial innermost level in the separator. The liquid of higher density is instead forced out through an outlet that is at a larger radial distance. Solids, or sludge, accumulate at the periphery of the separation chamber and is emptied intermittently from the separation space by a set of radially sludge outlets being opened, whereupon sludge and a certain amount of fluid is discharged from the separation space by means of centrifugal force.

[0083] The clean oil phase is brought to service tank 6. When needed by the engine 10, oil is transferred from the service tank using variable speed pump 7 through oil filter 8. This may be an automatic filter positioned before fuel conditioning module 9 to capture and remove particles and impurities before they can enter the engine 10.

[0084] The fuel conditioning module 9, or booster system, optimizes the properties of the fuel oil before it is injected to engine 10 in terms of cleanliness, pressure, temperature, viscosity and flow rate depending on the specification of the engine's combustion performance. This further increase energy efficiency and reduces emissions. As a part of the FCM 9, a fuel changeover system (ACS) 9a may be used. The ACS 9a is for maintaining the right fuel parameters at injection to the engine 10 at fuel changeover, i.e. when switching from a first fuel such as HFO to a distillate fuel. Since the injection temperature of distillate fuel is much lower than that of HFO, thermal shocks may arise in the injection system. An ACS manages fuel changeover e.g. by controlling temperature gradient inside the injection system and maintains the correct temperature and viscosity of the fuel at injection to engine 10. Further, the fuel conditioning module 9 also controls the flow rate of cleaned fuel oil from service tank 6.

[0085] The first feed pump 3 is regulated by a VFD 15 which is controlled by the separator control unit 12. The separator control unit 12 further controls the operation of the separator 5, e.g. when the separator is turned on and off, and thus also the flow rate of fuel oil from settling tank 2 to separator 5.

[0086] For this purpose the system control unit 13 and/or the separator control unit 12 may comprise a communication interface, such as a transmitter/receiver, via which it may receive and transmit data. The system control unit 13 and/or the separator control unit 12 may comprise a processing unit, such as a central processing unit, which is configured to execute computer code instructions which for instance may be stored on a memory. The memory may thus form a (non-transitory) computer-readable medium for storing such computer code instructions. The processing unit may alternatively be in the form of a hardware unit, such as an application specific integrated circuit, a field-programmable gate array or the like.

[0087] In this embodiment, in order to execute the requests sent by the system control unit 13, the separator control unit 12 is configured to receive an analog signal (4-20 mA or through Ethernet) which tells the separator control unit 12 which speed the feed pump 3 should run on, such as in the range 25-100% of the maximum capacity. The separator control unit 12 is further configured to receive a request signal for discharge and a request signal to turn on/off the separator, or rather, put it in standby.

[0088] The separator control unit 12 is further configured to send information to the system control unit 13, such as a status signal, i.e. if the separator 5 is in production or not. The separator 5 could be closed due to discharge, or in start-up or recirculation. Further information sent from separator control unit 5 to system control unit 13 may include the separators maximum throughput capacity, its current throughput (estimated from pump curve, or measured) and temperature, vibration and other sensor data that the separator is equipped with.

[0089] The system control unit 13, independent from the separator control unit 12, communicates with the separator control unit 12 and also the FCM 9, and collects information from the tanks 2 and 3, as indicated by the dotted lines in FIG. 1. In this embodiment, the system controll3 unit is configured to receive information about the fuel in the service or day tank 6, such as density, viscosity and temperature of the fuel in tank 6. This information may be used by the system control unit 13 to determine compatibility between different fuels.

[0090] The system control unit 13 is further configured to receive information from the FCM 9, such as the actual flow rate to the engine 10, information about fuel changeover, requests to the system control unit 13 to process another fuel. The FCM 9 may also inform the system control unit 13 about time until fuel will be taken out of operation and other readings from sensors and units in the FCM 9, e.g. sludge build-up in filters, temperatures, densities, etc.

[0091] During operation of the engine 10, the fuel consumption of the engine 10 is measured by a flow meter (not shown) at the FCM 9. This information is sent to the system control unit 13. System control unit 13 sends a requested throughput to the separator control unit 12, which will then regulate the speed of the feed pump 3 via the VFD. By lowering the flow through the separator 5, the separation efficiency will increase. The energy consumption of the feed pump 3 will be reduced, as will the heat demand of the pre-heater 4.

[0092] Further, the fuel level in the service tank 6 is be monitored by the system control unit 13. If, for some reason, the level drops below a lower-limit, the system control 13 may trigger an alarm and request 100% throughput of the separator 5. When the alarm has been acknowledged and the reason of the alarm fixed, the flow control of the separator 5 can be started again.

[0093] The tanks 2 and 6 could also be equipped with other types of sensors so that temperature, density, viscosity, sulphur level etc. could be measured and information sent to the system control unit 13. The sensors could be installed in both the day tank 6 and the settling tank 2. The separator 5 could then be requested by the system control unit 13 operate in different ways if it cleans a low density/viscosity distillate or a sluggish heavy fuel oil. The booster, i.e. the FCM 9, may treat the fuel in different ways depending on its properties.

[0094] FIG. 2 shows a further embodiment of a fuel treatment system 1 on board a ship. The system 1 and the units of the system function as discussed for the system in FIG. 1 above, but the system 1 in FIG. 2 comprises a second separator 5a for cleaning the oil in the settling tank 2. For this purpose, there is a second feed pump 3a is regulated by a VFD 15a that is controlled by a second separator control unit 12a. The operation of the separator 5a is controlled by the separator control unit 12a in similar ways as the first separator control unit 5 controls the first separator 5. The fuel cleaned by both separators 5 and 5a are sent to the same service tank 6.

[0095] In the system of FIG. 2, there is also an auxiliary engine 11 to which the cleaned fuel oil may be directed by the FCM 9. Further, in this example, the fuel conditioning module 9 controls the flow rate of cleaned fuel oil from service tank 6 by means of a Variable Frequency Drive 15 connected to the variable feed pump 7.

[0096] When a second separator 5a is added to the system 1, as illustrated in FIG. 2, the system control unit 13 may coordinate the flow through the separators 5 and 5a to match the total consumption of the engines 10 and 11. When the consumption goes below an efficiency breakpoint, the system control unit 13 may request that one off the separators is turned off. When the fuel consumption increases above the efficiency breakpoint, the other separator will be requested to start up again. The efficiency breakpoint may be pre-set manually by an operator.

[0097] Further, in the system shown in FIG. 2, the first separator control unit 12 also controls the pre-heater 4 for heating the oil supplied to the first separator 5 and the second separator control unit 12a also controls the pre-heater 4a for heating the oil supplied to the second separator 5a. Thus, the system control unit 13 may send operational requests to the separator control units to change the temperature and therefore the viscosity of the fuel oil to be cleaned based on information from e.g. the service tank 6 or the FCM 9.

[0098] The system 1 may comprise further centrifugal separators, such as three or more separators, which are all controlled by separator control units, and the system control unit 13 may thus be configured to send requests to all separators in the fuel treatment system 1.

[0099] FIG. 3 shows a further embodiment of a fuel treatment system 1 on board a ship. The system 1 and the units of the system function as discussed for the system in FIG. 2 above, but the system 1 in FIG. 3 contains a first tank 2 as well as a second settling tank 2a having a different type of fuel than settling tank 2. For example, settling tank 2 may contain HFO whereas settling tank 2a may contain a distillate fuel, or the tanks 2 and 2a may have different types of distillate fuels.

[0100] The oil cleaned by the separators 5 and 5a are sent to two different service tanks 6 and 6a, and the FCM 9 may control which fuel and how much fuel is to be supplied from each tank. This is performed by using feed pump 7 for supplying cleaned oil from tank 6 and by using feed pump 7a for supplying cleaned oil from tank 6a. Information on the supply of oil from each tank 6 and 6a may be sent by the system control unit 13.

[0101] Further, as discussed in relation to FIG. 1 above, information of the fuel properties of the bunkered fuels in the settling tank 2 and 2a may be measured by sensors on board and be sent to the system control unit 13. As an alternative, information of the fuel properties may be inserted in the software of the system control unit 13 manually when bunkering. The relevant fuel properties will thus be assigned to each settling tank 2 and 2a. The system control unit 13 may then calculate the blended properties of the fuels in the settling tanks 2 and 2a and send such information to the FCM 9, or if the cleaned fuels from both tanks 2 and 2a are sent to the same service tank, i.e. if there were only a single service tank 6 in the system of FIG. 3, then the system control unit 13 may calculate the actual fuel property of the blend in such a single service tanks.

[0102] Information of the fuel property of a blended fuel may comprise information of sulphur levels, since these are of interest regarding emission regulation in Sulphur Emission Control Areas (SECAs) or Emission Control Areas (ECAs) sea areas.

[0103] Also, the fuel properties could be of interest in compatibility evaluations of the FCM. If statistical data on the incompatibility of fuels is gathered by the system control unit 13, the FCM could avoid those blends in a fuel switch.

[0104] Furthermore, whereas FIGS. 2 and 3 illustrate embodiments of fuel treatment systems arranged for treating fuel to be provided for two engines, the fuel treatment systems illustrated in FIGS. 2 and 3 are also applicable for one engine, or for more than two engines.

[0105] The invention is not limited to the embodiment disclosed but may be varied and modified within the scope of the claims set out below. The invention is not limited to the type of separator as shown in the FIGS. The term centrifugal separator also comprises centrifugal separators with a substantially horizontally oriented axis of rotation and separator having a single liquid outlet.