Method of operating a system including a centrifuge

Abstract

The present invention provides a method (100) for operating a system (1) including a centrifuge (2) for separating at least one liquid phase and a sludge phase from a liquid feed mixture. The method (100) includes alternating between a first and a second operating mode. The first operating mode includes step a) feeding (101) the liquid feed mixture to be cleaned to the centrifuge (2), the liquid feed mixture having a first temperature, and step b) discharging (102) at least one separated liquid phase from the centrifuge (2). The second operating mode includes step c) stopping (103) the supply of the liquid feed mixture to the centrifuge (2) and step d) reducing (104) the temperature of the liquid feed mixture to a second temperature and / or reducing (105) the flow rate of the liquid feed mixture. The present invention also provides a system (1) for separating at least one liquid phase and a sludge phase from a liquid feed mixture.

Description

[Technical Field]

[0001] The present invention relates to the field of centrifuges, such as centrifuges for purifying fuel oil on ships, and more particularly to reducing the power consumption of systems including centrifuges. [Background technology]

[0002] Centrifuges are commonly used to separate liquids and / or solids from a liquid or gas mixture. During operation, the fluid mixture to be separated is introduced into a rotating bowl, and centrifugal force causes heavy particles or denser liquids, such as water, to accumulate at the periphery of the rotating bowl, while less dense liquids accumulate near the central axis of rotation. This allows the separated fractions to be collected, for example, by different outlets located at the periphery and near the axis of rotation, respectively.

[0003] Fuel supplied to ships is typically treated on board before use in the engine to remove solid contaminants, such as particles of silicon and aluminum compounds called catalytic fines (e.g., aluminosilicates known as microporous aluminum silicates or zeolites), and liquid contaminants, such as water. Marine diesel engines can typically use multiple types of commercially available fuel oil, as long as the oil is properly treated on board. Furthermore, engine lubricating oil may also contain solid and liquid impurities, such as water, which must be separated before use.

[0004] Separation of fuel oil from lubricating oil is a very energy-intensive application. For example, when separating heavy fuel oil (HFO) used as fuel for ships, the oil is typically heated from 50 to 98°C. Approximately 5 m 3 To operate a typical separator with a capacity of 10000 / h, the energy required to heat the feed is approximately 130 kW.

[0005] Therefore, there is a need in the art for improved separation protocols to reduce the overall energy consumption of separation systems. Summary of the Invention [Problem to be solved by the invention]

[0006] A primary object of the present invention is to provide a system and method for reducing the overall energy consumption of separation processes, such as fuel oil and lubricating oil separation, on board ships. [Means for solving the problem]

[0007] In a first aspect of the present invention, there is provided a method of operating a system including a centrifuge for separating at least one liquid phase and a sludge phase from a liquid feed mixture, the method comprising alternating between a first mode of operation and a second mode of operation, The first mode of operation comprises: step a) feeding the liquid feed mixture to be washed into the centrifuge, the liquid feed mixture having a first temperature; Step b) discharging at least one separated liquid phase from said centrifuge; Including, The second mode of operation comprises: step c) stopping the supply of the liquid feed mixture to the centrifuge; step d) reducing the temperature of the liquid feed mixture to a second temperature and / or reducing the flow rate of the liquid feed mixture; Includes.

[0008] The system may include a centrifuge and associated equipment that affects process parameters of the liquid feed mixture being separated, such as the flow rate and temperature of the liquid feed mixture.

[0009] The method includes two different operation modes: a first operation mode in which at least steps a) and b) are performed, and a second operation mode in which at least steps c) and d) are performed.

[0010] The method includes the step of cyclically alternating between the first mode and the second mode, i.e., performing the first mode, then performing the second mode, then performing the first mode again, etc. Thus, steps a) and b) can be performed after steps c) and d) in a further cycle performing all steps a) through d), and thus the second mode can be performed immediately after the first mode, or vice versa.

[0011] However, the two modes may be operated at different time intervals, for example, the first mode, which feeds the liquid feed mixture to the centrifuge for separation, may be operated for the majority of the operating time, and the second mode may be operated during intermittent periods, such as short breaks during operation in the first mode.

[0012] The centrifuge is for separating at least one liquid phase and a sludge phase from a liquid feed mixture. Accordingly, the centrifuge may be configured to separate the liquid feed mixture into a single liquid phase and a sludge phase, or into two liquid and sludge phases. The centrifuge may comprise a stationary frame and a drive member for rotating a centrifuge bowl within the frame. The centrifuge bowl encloses a separation space. The separation space may comprise a stack of separation discs centrally arranged around the axis of rotation. Such separation discs form inserts that increase the surface area in the separation space. The separation discs may have a frustoconical shape, i.e., the stack may comprise a stack of frustoconical separation discs.

[0013] Thus, step a) of feeding the liquid feed mixture to be washed into the centrifuge may comprise, for example, feeding the liquid feed mixture into the separation space of the centrifuge from a tank storing the liquid feed mixture via an inlet pipe leading to the separation space. The liquid feed mixture in step a) has a first temperature, which may be above room temperature, for example above 50°C, for example above 90°C.

[0014] The step b) of discharging at least one separated liquid phase may be a step of continuously discharging at least one separated liquid phase, for example a step of continuously discharging only the first separated liquid phase, or a step of continuously discharging the first and second separated liquid phases.

[0015] In the second operating mode, step c) is performed, i.e., the supply of the liquid feed mixture to the centrifuge is stopped. However, the separated liquid feed mixture may continue to flow to other parts of the system, for example, it may be recycled to the tank that supplies the centrifuge. Thus, during step c), the flow rate of the liquid feed mixture may still be greater than zero.

[0016] Furthermore, during the second mode, during step d), the temperature of the liquid feed mixture is reduced to a second temperature lower than the first temperature, or the flow rate of the liquid feed mixture is reduced, or alternatively both of these measures are performed, i.e., the temperature of the liquid feed mixture is reduced to a second temperature lower than the first temperature and the flow rate of the liquid feed mixture is reduced.

[0017] Step d) is carried out during step c), ie during the time when no liquid feed mixture is being fed and therefore does not enter the centrifuge.

[0018] Thus, step d) may include reducing the temperature of the liquid feed mixture to a second temperature and / or reducing the flow rate of the liquid feed mixture when the liquid feed mixture is not being fed to the centrifuge.

[0019] The first aspect of the present invention is based on the insight that power-saving measures can be implemented on the liquid feed mixture to be separated during the second operating mode, i.e., during the entire process when no actual separation is taking place within the separator. This is the case, for example, during centrifuge shutdown or sludge phase discharge. It has been found that such power-saving measures maintain good process and separation even when the first operating mode is continued after the second operating mode. This has been found to be advantageous during the separation of marine fuel oil, where the oil feed to be separated is stopped or redirected away from the separator during the discharge of the separated sludge. Such a discharge sequence takes approximately 60 to 200 seconds, e.g., 90 to 150 seconds, during which the pre-separated oil feed is run in a recirculating state and is still heated to 98°C. The inventors have discovered that, for example, by reducing the heating during such a discharge sequence (second operating mode), good separation performance can still be achieved when the feed is sent back to the separator (first operating mode).

[0020] Thus, in an embodiment of the first aspect of the present invention, the second mode of operation further comprises step e) discharging the separated sludge phase from the centrifuge.

[0021] Thus, the second operating mode may include an actual discharge sequence. Such a discharge sequence, i.e., the second operating mode, may be less than 3 minutes and may be performed, for example, less than 5 times per hour, e.g., less than 3 times per hour during normal separation of marine fuel oil.

[0022] Step e) may further include supplying a displacement liquid to the centrifuge. As is well known in the art, a so-called displacement liquid, such as water, is typically supplied to the centrifuge bowl immediately before the sludge is discharged. The purpose of supplying the displacement liquid is to reduce the amount of separated liquid phase in the separation space and prevent the separated liquid phase from flowing out of the separation space through the sludge outlet during discharge. For example, when water is the heavier liquid to be separated from the liquid feed mixture, water is typically used as the displacement liquid.

[0023] However, the centrifuge may also be placed in a standby mode during the second operating mode. Such a standby mode may, for example, include reducing the rotation speed before the centrifuge is stopped. For example, the centrifuge may be placed in a standby mode for 10 minutes before being stopped. Thus, to save energy, during standby of the centrifuge, a step d) of reducing the temperature of the feed to a second temperature that reduces the flow rate of the liquid feed mixture may also be performed.

[0024] In an embodiment of the first aspect, the method is a method for treating fuel oil on board a ship, i.e. a method for use on board a ship.

[0025] In an embodiment of the first aspect, step a) comprises supplying the liquid feed mixture from a tank, and step c) further comprises recirculating the liquid feed mixture to the tank. Thus, the second mode of operation may comprise recirculating the liquid feed mixture.

[0026] However, a second mode of operation may involve actually stopping the flow of the liquid feed mixture.

[0027] In an embodiment of the first aspect, step a) comprises heating said liquid feed mixture to said first temperature using a heating device.

[0028] The heating device may be an electric heater. However, the heating device may also be a steam / hot water / thermal oil heat exchanger. The first temperature may be above room temperature, for example, above 50°C, for example, above 90°C.

[0029] Step d) may comprise reducing the temperature by at least 10°C, such as at least 20°C, such as at least 30°C, such as at least 40°C.

[0030] Step d) of reducing the temperature of the liquid feed mixture to a second temperature may comprise reducing the setpoint temperature of a heating device to said second temperature. Thus, the actual measured temperature of the liquid feed mixture during step d) may be higher than said second temperature. Thus, setting the setpoint temperature of the heating device lower may save energy.

[0031] As an example, step d) may include turning off a heating device.

[0032] In an embodiment of the first aspect, step a) comprises supplying said liquid feed mixture using a liquid feed pump.

[0033] To reduce the flow rate of the liquid feed mixture during step d), the set flow rate of such feed pump may be reduced.

[0034] As an example, step d) may include turning off the liquid supply pump.

[0035] In an embodiment of the first aspect, the liquid feed mixture is an oil and said first temperature in step a) is at least 50°C.

[0036] The separation temperature is often determined by the viscosity of the oil: the lower the viscosity of the oil being processed in the separator, the higher the separation efficiency.

[0037] The oil may be a lubricating oil or may be a fuel oil, such as a fuel oil for a diesel engine.

[0038] As used herein, the term "diesel engine fuel oil" refers to oil intended for use in marine engines or power generation engines, such as power plant engines. The term "fuel oil" refers to oils as defined in ISO 8217, Petroleum Products - Fuels (Class F) - Specification for Marine Fuels, 2005 and 2012 editions, or oil components / phases obtained by pre-treating such oils prior to use in marine engines or power plants. Diesel is considered a fuel oil herein. Thus, fuel oil can be either marine (residual) fuel oil (MFO) or bunker C oil.

[0039] "Diesel engine fuel oil" may consist of several types of fuel oil with different viscosities that are typically stored in tanks, which means that the type of fuel oil sent to the separator for cleaning may change over time.

[0040] For example, diesel engine fuel oil is composed of heavy fuel oil (HFO), which is the oil remaining from the cracking process in distillation or mineral oil processing. Step a) may therefore involve washing the fuel oil in a centrifuge to obtain a clean oil phase and, optionally, a sludge phase and an aqueous phase. The sludge phase may contain solid impurities such as catalyst fines. Catalyst fines are residues from a crude oil refining process called catalytic cracking, in which long hydrocarbon molecules are broken down into shorter molecules.

[0041] In one example, the liquid feed mixture is a fuel oil and the first temperature in step a) is at least 50°C, such as at least 70°C, for example at least 95°C, such as about 98°C.

[0042] Furthermore, when the liquid feed mixture is an oil and the first temperature in step a) is at least 50°C, step d) may comprise reducing the temperature of the oil to a second temperature that is at least 10°C lower than the first temperature.

[0043] In one example, the liquid feed mixture is a fuel oil for a diesel engine, said first temperature is at least 97°C, and step d) comprises reducing the temperature of said oil to below 80°C, for example below 70°C.

[0044] Thus, in an embodiment of a first aspect, there is provided a method of operating a system comprising a centrifuge for separating a clean oil phase and a sludge phase from a fuel oil, said method comprising switching between a first mode of operation and a second mode of operation, said first mode of operation comprising: Step a) feeding fuel oil to be purified, having a first temperature of at least 95°C, into the centrifuge; Step b) Discharging at least the clean oil phase from the centrifuge; Including, The second mode of operation comprises: step c) stopping the supply of fuel oil to the centrifuge; Step d) reducing the temperature of the fuel oil to a second temperature below 70°C and / or reducing the flow rate of the fuel oil; Includes.

[0045] As previously mentioned, the liquid feed mixture can be lubricating oil. The lubricating oil can be lubricating oil for an engine, such as a diesel engine. In an embodiment of the first aspect, the method is a method for treating lubricating oil on board a ship, i.e., for use on a ship.

[0046] The separation temperature of the lubricating oil is often above 70°C, for example at least 95°C. The separated lubricating oil is sent to an oil tank, such as an oil tank or oil pan, located below the engine, from where it is supplied to the engine. However, the lubricating oil is usually cooled to around 55°C before being supplied to the engine. As a result, when the method of the present invention is applied, the lubricating oil does not need to be fully heated during the second operating mode, but is instead circulated back to the oil tank, so the temperature of the oil in the oil tank is lower and therefore less energy is needed to cool the oil to the required temperature while it is being supplied to the engine.

[0047] Thus, in an embodiment of a first aspect, there is provided a method of operating a system comprising a centrifuge for separating a clean oil phase and a sludge phase from a lubricating oil, said method comprising alternating between a first mode of operation and a second mode of operation, said first mode of operation comprising: step a) supplying lubricating oil to be washed to the centrifuge, the lubricating oil having a first temperature of at least 95°C; Step b) Discharging at least the clean oil phase from the centrifuge; Including, The second mode of operation comprises: step c) stopping the supply of lubricating oil to the centrifuge; Step d) reducing the temperature of the lubricating oil to a second temperature less than 70°C and / or reducing the flow rate of the lubricating oil; Includes.

[0048] In a second aspect of the present invention, there is provided a system for separating at least one liquid phase and a sludge phase from a liquid feed mixture, said system comprising: - a centrifuge configured to separate at least one liquid phase and a sludge phase from said liquid feed mixture, and further arranged to continuously discharge said at least one separated liquid phase and to intermittently discharge said sludge phase; a liquid feed pump for supplying the liquid feed mixture to the centrifuge; a heating device for heating the liquid feed mixture; a control device configured to regulate the supply of a liquid feed mixture to the centrifuge via the liquid feed pump and / or to regulate the temperature of the liquid feed mixture using the heating device; Equipped with and further configured to initiate discharge of the sludge phase from the centrifuge, and further configured to alternate between the first and second operation modes in accordance with the first aspect of the invention described herein above.

[0049] The terms and definitions used in relation to the second aspect are the same as those explained in relation to the first aspect above.

[0050] The centrifuge may thus be as described in relation to the first aspect above. The centrifuge may be configured to separate two liquid phases and a sludge phase from the liquid feed mixture. The two liquid phases may be discharged continuously, or one may be discharged continuously and the other may be discharged intermittently, for example by a valve located downstream of the liquid outlet of the centrifuge.

[0051] The liquid feed pump may be located upstream of the heating device and therefore upstream of the centrifuge.

[0052] The heating device can be an electric heater, but can also be a steam / hot water / heat transfer oil heat exchanger.

[0053] The controller is configured to regulate the amount of liquid supply mixture dispensed and / or the temperature of the liquid supply mixture to be cleaned. Accordingly, the controller may include a processor and input / output interfaces for communicating with the liquid supply pump and / or the heating device. Accordingly, the controller may include any suitable type of programmable logic circuit, processor circuit, or microcomputer, such as a digital signal processing circuit (Digital Signal Processor, DSP), a central processing unit (CPU), a processing unit, processing circuit, processor, application specific integrated circuit (ASIC), FPGA (Field Programmable Gate Array), microprocessor, or other processing logic capable of interpreting and executing instructions.

[0054] The controller may be the same controller used to regulate and control parameters such as the rotation speed of the centrifuge, so the software used to control the centrifuge may also be used to control the liquid feed pumps and / or heating devices.

[0055] In an embodiment of the second aspect, the control device is configured to perform steps a), c) and d) of the method according to the first aspect described above.

[0056] Furthermore, the control device may be configured to initiate step e) of discharging the separated sludge phase from the centrifuge.

[0057] Thus, the controller may be configured to initiate an intermittent discharge sequence of the centrifuge by sending instructions to an operating water module (OWM) used in the art to supply a constant amount of water to an intermittent discharge system of the centrifuge, and to intermittently open the sludge outlet of the centrifuge.

[0058] In an embodiment of the second aspect, the system may further comprise a tank for storing the liquid feed mixture to be separated, and a liquid feed pump may be arranged to supply the liquid feed mixture from the tank to the centrifuge.

[0059] Thus, the system may further comprise a bunker tank or the like for storing the washed liquid feed mixture before it is fed to the centrifuge.

[0060] Additionally, the system may include a valve member positioned upstream of the centrifuge and configured to direct the supply of liquid feed mixture to the centrifuge during a first mode of operation and to return the supply of liquid feed mixture to the tank during a second mode of operation.

[0061] Thus, a valve member, such as a three-way valve, may be used to alternately route the liquid feed mixture to the centrifuge and back to the tank during recirculation, and the controller may be configured to control such a valve member, i.e., to send instructions to the valve member to switch between routing the liquid feed mixture to the centrifuge and back to the tank.

[0062] According to a third aspect of the present invention, there is provided a computer program comprising instructions for causing a control device to perform steps a), c), and d) of the method of the first aspect described above. For example, the computer program may comprise instructions for causing the control device to perform steps a), c), d), and e) of the method of the first aspect described above.

[0063] Furthermore, the computer program may include instructions to cause the control device to also perform step b) of the method of the first aspect described above. Thus, the instructions may be, for example, instructions to open a valve arranged downstream of the separated liquid phase outlet and to discharge the separated liquid phase from the centrifuge.

[0064] In a fourth aspect of the present invention, there is provided a computer readable medium storing the computer program of the third aspect of the present invention. [Brief explanation of the drawings]

[0065] [Figure 1]1 shows a schematic diagram of an embodiment of a system of the present invention in a first mode of operation. [Figure 2] 1 shows a schematic diagram of an embodiment of a system of the present invention in a second mode of operation. [Figure 3] 1 shows a schematic diagram of the centrifuge of the system. [Figure 4] 1 illustrates a schematic diagram of a method of operating a system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0066] The methods and systems according to the present disclosure are explained in more detail below with reference to the accompanying drawings, in which: These examples describe a system for purifying diesel engine fuel oil and a method of operating such a system, but the teachings are of course applicable to other applications, i.e., when using other types of liquid feed mixtures.

[0067] 1 is a schematic diagram of one embodiment of a system 1 for purifying diesel engine fuel oil. The system 1 includes a centrifuge 2 for separating at least a clean oil phase and a sludge phase from fuel oil stored in a bunker tank (or settling tank) 20. The fuel oil to be purified is supplied to the centrifuge 2 via a liquid supply pump 21 of the system 1 and a pipe 26. The system further includes a heating device 22 for heating the fuel oil to be purified. In this embodiment, the fuel oil is first heated to approximately 98°C by the heating device 22.

[0068] The system also comprises a three-way valve 23 arranged upstream of the centrifuge 2 and configured to direct the supply of fuel oil to be cleaned either to the centrifuge 1 or back to the bunker tank (or settling tank) 20, for example during circulation.

[0069] As shown in Figure 1, in a first operating mode of the disclosed method, the three-way valve 23 is set to direct the fuel oil to be purified into the centrifuge via the inlet pipe 8. In this example, the centrifuge is configured to continuously discharge the purified oil phase via the liquid light phase outlet 13 and the separated aqueous phase via the liquid heavy phase outlet 14. During oil cleaning, a sludge phase accumulates in the centrifuge. This sludge must be discharged from the centrifuge 1 some time after separation. Therefore, the centrifuge is also equipped with the function of intermittently discharging the sludge phase.

[0070] 2, in a second operating mode, the supply of fuel oil to be cleaned to the centrifuge 1 is stopped. This is done by using a three-way valve to return the fuel oil to the bunker tank 20, i.e. the fuel oil is recirculated to the tank 22.

[0071] The intermittent discharge sequence involves supplying a displacement liquid, such as water, to the centrifuge via inlet 8. The displacement water is supplied from tank 30, from which it is fed via piping 31 to inlet pipe 8. Operational water is then supplied to the centrifuge using operation water module (OWM) 41 to open the sludge outlets. These outlets are opened only momentarily to discharge sludge that has accumulated in the centrifuge bowl of separator 1. During this intermittent discharge sequence, no clean oil or water phase is discharged from outlets 13 or 14.

[0072] During this second mode of operation, when the purified fuel oil is recirculated to the tank 20, the temperature of the fuel oil is reduced, for example to below 60°C, for example to 50°C. This is done by lowering the set temperature of the heating device 22 or by turning off the power to the heating device 22. Alternatively or complementary, the flow rate of the fuel oil circulated to the tank 20 is reduced by lowering the set flow rate of the liquid feed pump 21 or by turning off the liquid feed pump.

[0073] As a result, as shown by the method steps of Figure 4, the disclosed method includes a first mode of operation in which continuous cleaning of the fuel oil occurs, and a second mode of operation in which the cleaned fuel oil is not fed to the centrifuge 1 and energy is saved by reducing the temperature and / or flow rate of the recirculated fuel oil. Thus, in this example, the first mode of operation includes: Step a) supplying fuel oil to be cleaned from a tank to a centrifugal separator (2) (101) and heating the fuel oil to be cleaned to a first temperature of about 98°C (101); Step b) Discharging the clean oil and water phases from the centrifuge 2 (102); Includes.

[0074] The second mode of operation is Step c) stopping the supply of fuel oil to the centrifugal separator 2 and recirculating the fuel oil to be purified back into the tank (103); Step d) reducing the temperature of the recirculated fuel oil to a second temperature below 70°C (104) and / or reducing the flow rate of the liquid feed mixture (105); Step e) Discharging the separated sludge phase from the centrifuge (106); Includes.

[0075] Furthermore, after step e) has been carried out, the system 1 may again be operated in the first operating mode until further sludge discharge needs to be carried out.

[0076] 1 and 2, the system also includes a controller 50 configured to regulate the supply (e.g., flow rate) of fuel oil to the centrifuge 2 via a liquid feed pump 21, as indicated by dotted arrow "A." The controller 21 is further configured to regulate the temperature of the fuel oil mixture using a heating device 22, as indicated by dotted arrow "B," and to control whether the fuel oil is supplied to the separator 1 or recirculated to the tank 22 using a three-way valve 23, as indicated by arrow "E." Thus, the controller 50 is configured to alternate between a first mode of operation and a second mode of operation in accordance with the method of the present disclosure.

[0077] For regulation purposes, the control device 50 may include a processing unit, such as a central processing unit configured to execute computer code instructions stored in 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 component, such as an application-specific integrated circuit, a field-programmable gate array, or the like. The control device 50 may therefore include a communication interface, such as a transmitter / receiver, through which it can receive data from the liquid supply pump 21 and the heating device 22 and transmit data, including operation requests, to the liquid supply pump 21 and the heating device 22.

[0078] Therefore, the present invention also provides a computer program comprising instructions for causing a control device to carry out steps a), c) and d) of the disclosed method.

[0079] The control unit 50 may be the same control unit that is used to control the centrifuge 2 itself. The control unit may therefore be configured to control the speed of the centrifuge, as indicated by arrow "C". The control unit may further be configured to initiate the discharge of the sludge phase from the centrifuge 2. To this end, the control unit 50 may be configured to control the operating water module (OWM) 41, as indicated by arrow "D".

[0080] Therefore, the present invention also provides a computer program comprising instructions for causing a control device to carry out steps a), c), d) and e) of the disclosed method.

[0081] The method and system 1 of the present invention is advantageous in that it reduces the overall power consumption of the system 1. As an example, during fuel oil washing on a ship, the fuel oil supply is typically heated to between 50°C and 98°C. A typical size separator (with a capacity of about 5m) 3 To operate the separator at a rate of up to 1000 kJ / h, approximately 130 kW of energy is required to heat the feedstock. During sludge discharge, the fuel oil supply to the separator is almost always stopped. The sludge discharge sequence, including the supply of operating water, can take a total of 150 seconds. During this 150-second period, the fuel oil continues to circulate. This invention thus achieves intelligent heating control, changing the temperature setpoint to no heating or only a slight heating, such as 60°C, when recirculation begins. Assuming a typical discharge interval of one hour, the operating time in the second mode per 24 hours is approximately one hour. This means that the system can save up to 130 kWh of electricity per day, a significant savings.

[0082] FIG. 3 shows and explains in more detail the centrifuge 2 that can be used in the system 1 shown in FIGS.

[0083] The centrifuge 2 comprises a rotatable centrifuge bowl 9 which itself defines a separation chamber 10 within which the fuel oil is centrifuged during operation.

[0084] The separation chamber 10 is provided with a stack of frustoconical separation discs 11 for effective separation of the fuel oil. The stack of frustoconical separation discs 11 is an example of a surface-enhancing insert. These discs 11 are mounted coaxially in the center of the centrifuge bowl and may include holes that form channels 12 for axial flow of liquid when the separation discs 11 are mounted in the centrifuge 2. An inlet pipe 8 forms a central duct and is configured to introduce the fuel oil for centrifugation in the separation chamber 10. In this embodiment, the fuel oil is fed from the top, but bottom-feed separators may also be used in the system 1.

[0085] Extending from the centrifuge 2 are a liquid light phase outlet 13 for the low density components separated from the fuel oil, and a liquid heavy phase outlet 14 for the high density components, i.e., the heavy phase, separated from the fuel oil. Thus, the liquid light phase outlet 13 is for discharging the clean oil phase, and the liquid heavy phase outlet 14 is for discharging the separated water phase. The outlets 13, 14 extend through the frame 15.

[0086] Centrifuge bowl 9 is further provided with a set of radial sludge outlets 16 at its periphery, which are configured as intermittently openable outlets for discharging dense components such as sludge and other solids. This material is discharged from the radially outer portion of separation chamber 10 into the space surrounding centrifuge bowl 9. For example, a phase containing catalyst fines may be discharged through outlets 16.

[0087] The centrifuge 2 further includes a spindle 4 and a drive motor 7 for rotating a centrifuge bowl 9 attached to the spindle at a predetermined speed. The spindle 4 and centrifuge bowl 9 are suspended in a stationary frame 15 by upper and lower bearings 5 ​​and 6.

[0088] During operation of the separator shown in Figure 3, the centrifuge bowl 9 is rotated by a drive motor 7. The fuel oil to be separated is introduced into the separation space 10 via an inlet pipe 8. Different phases within the fuel oil are separated between the separation disks 11 according to their densities. While heavier components, such as the aqueous and sludge phases, move radially outward between the separation disks, the least dense phase, such as the clean oil phase, moves radially inward between the separation disks and is forced out through an outlet 13 located at the innermost radial level within the separator. Instead, the denser liquid is forced out through an outlet 14, located at a radial distance greater than the radial level of the outlet 13. Thus, during separation, an interface between the low-density liquid and the high-density liquid is formed within the separation space 10. The solids, i.e., the sludge, accumulate around the periphery of the separation chamber 10 and are intermittently discharged from the separation space by opening the sludge outlet 16, resulting in the sludge and a certain amount of fluid being centrifuged out of the separation space.

[0089] In certain applications, the separator 1 includes only a single liquid outlet, such as only a liquid outlet 13 and only a sludge outlet 16. This will depend on the fuel oil being treated.

[0090] The invention is not limited to the disclosed embodiments, but may be varied and modified within the scope of the claims. Furthermore, the invention is not limited to the type of separator shown in the drawings. The term "centrifuge" also includes centrifuges with a substantially horizontally oriented rotation axis and separators with a single liquid outlet. [Explanation of symbols]

[0091] 1 System 2. Centrifuge 4 spindles 5 Upper bearing 6 Lower Bearing 7 Drive motor 8 inlet pipe 9 Centrifugal Bowl 10 Separation room 11 Separation disc 13 Liquid light phase outlet, liquid outlet 14 Liquid heavy phase outlet 15 Fixed Frame 16 Sludge outlet 20 Bunker tank (or settling tank) 21 Liquid supply pump 22 Heating device 23 Three-way valve 41 Operated Water Module (OWM) 50 Control device

Claims

1. A method (100) of operating a system (1) comprising a centrifuge (2) for separating at least one liquid phase and a sludge phase from a liquid feed mixture, the method (100) comprising alternating between a first mode of operation and a second mode of operation; The first mode of operation comprises: Step a) feeding (101) the liquid feed mixture to be washed into the centrifuge (2), the liquid feed mixture having a first temperature; Step b) Discharging (102) at least one separated liquid phase from said centrifuge (2); Including, The second mode of operation comprises: Step c) stopping (103) the supply of said liquid feed mixture to said centrifuge (2); Step d) reducing the temperature of the liquid feed mixture to a second temperature (104) and / or reducing the flow rate of the liquid feed mixture (105); A method (100) comprising:

2. The second mode of operation comprises:

10. The method (100) of claim 1, further comprising step e) discharging (106) the separated sludge phase from the centrifuge (2).

3. 2. The method (100) of claim 1, wherein step a) comprises supplying (101) the liquid feed mixture from a tank (20), and wherein step c) comprises recirculating the liquid feed mixture to the tank (20).

4. The method (100) of any one of claims 1 to 3, wherein step a) further comprises heating the liquid feed mixture to the first temperature using a heating device (22).

5. The method (100) of claim 4, wherein step d) comprises turning off the heating device (22).

6. The method (100) of any one of claims 1 to 5, wherein step a) comprises the step of supplying (101) the liquid feed mixture using a liquid feed pump (21).

7. 7. The method (100) of claim 6, wherein step d) comprises turning off the liquid supply pump (21).

8. The method (100) of any one of claims 1 to 7, wherein the liquid feed mixture is an oil and the first temperature in step a) is at least 50°C.

9. 9. The method (100) of claim 8, wherein step d) comprises reducing the temperature of the oil to a second temperature that is at least 10 degrees Celsius lower than the first temperature.

10. 10. The method (100) of claim 9, wherein the liquid feed mixture is fuel oil for a diesel engine, the first temperature is at least 97°C, and step d) comprises reducing the temperature of the oil to below 80°C, such as below 70°C.

11. 1. A system (1) for separating at least one liquid phase and a sludge phase from a liquid feed mixture, the system (1) comprising: a centrifuge (2) configured to separate at least one liquid phase and a sludge phase from said liquid feed mixture and further configured to continuously discharge said at least one separated liquid phase and to intermittently discharge said sludge phase; a liquid feed pump (21) for feeding said liquid feed mixture to said centrifuge (2); a heating device (22) for heating said liquid feed mixture; a control device (50) configured to regulate the supply of said liquid feed mixture to said centrifuge (2) via said liquid feed pump (21) and / or to regulate the temperature of said liquid feed mixture by means of said heating device (22); and configured to initiate discharge of the sludge phase from the centrifuge (2), Furthermore, the control device (50) is configured to alternate between the first and second operating modes by a method (100) according to any one of claims 1 to 10.

12. The system (1) according to claim 11, wherein the control device (50) is configured to perform steps a), c), and d) of the method (100) according to any one of claims 1 to 10.

13. 13. The system (1) according to claim 12, wherein the control device (50) is further configured to initiate step e) of discharging the separated sludge phase from the centrifuge (2).

14. 14. The system (1) according to any one of claims 11 to 13, further comprising a tank (20) for storing the liquid feed mixture to be separated, wherein the liquid feed pump (21) is configured to supply the liquid feed mixture from the tank (20) to the centrifuge (2).

15. 15. The system (1) of claim 14, further comprising a valve member (23) arranged upstream of the centrifuge (2), the valve member (23) configured to direct the supply of liquid feed mixture to the centrifuge (1) during the first mode of operation and to return the supply of liquid feed mixture to the tank (20) during the second mode of operation.

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