WO2004053035A1 - A method of purifying contaminated oil from particles suspended in the oil in a centnrifugal separator - Google Patents

A method of purifying contaminated oil from particles suspended in the oil in a centnrifugal separator Download PDF

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Publication number
WO2004053035A1
WO2004053035A1 PCT/SE2003/001925 SE0301925W WO2004053035A1 WO 2004053035 A1 WO2004053035 A1 WO 2004053035A1 SE 0301925 W SE0301925 W SE 0301925W WO 2004053035 A1 WO2004053035 A1 WO 2004053035A1
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WO
WIPO (PCT)
Prior art keywords
oil
liquid
particles
separation chamber
separation
Prior art date
Application number
PCT/SE2003/001925
Other languages
French (fr)
Inventor
Claes Wase
Original Assignee
Alfa Laval Corporate Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alfa Laval Corporate Ab filed Critical Alfa Laval Corporate Ab
Priority to AT03812745T priority Critical patent/ATE438700T1/en
Priority to AU2003302920A priority patent/AU2003302920A1/en
Priority to DE60328710T priority patent/DE60328710D1/en
Priority to JP2004558969A priority patent/JP4620470B2/en
Priority to EP03812745A priority patent/EP1570036B1/en
Priority to US10/538,295 priority patent/US7410456B2/en
Priority to DK03812745T priority patent/DK1570036T3/en
Publication of WO2004053035A1 publication Critical patent/WO2004053035A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M175/00—Working-up used lubricants to recover useful products ; Cleaning
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G31/00—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for
    • C10G31/10—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for with the aid of centrifugal force
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04B—CENTRIFUGES
    • B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
    • B04B1/04—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with inserted separating walls
    • B04B1/08—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles with inserted separating walls of conical shape
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M175/00—Working-up used lubricants to recover useful products ; Cleaning
    • C10M175/0008—Working-up used lubricants to recover useful products ; Cleaning with the use of adsorbentia
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M175/00—Working-up used lubricants to recover useful products ; Cleaning
    • C10M175/0058—Working-up used lubricants to recover useful products ; Cleaning by filtration and centrifugation processes; apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M175/00—Working-up used lubricants to recover useful products ; Cleaning
    • C10M175/02—Working-up used lubricants to recover useful products ; Cleaning mineral-oil based
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S494/00—Imperforate bowl: centrifugal separators
    • Y10S494/901—Imperforate bowl: centrifugal separators involving mixture containing oil

Definitions

  • the present invention relates to a method of purifying contaminated oil from particles suspended in the oil by means of a liquid separation aid, which has a density larger than that of the oil.
  • the separation aid is dispersed in the contaminated oil in order to make the particles more easily separable from the oil.
  • the contaminated oil and the liquid separation aid are supplied into a separation chamber of a rotating centrifugal rotor.
  • the liquid separation aid and the particles are separated from the oil by centrifugal force.
  • the purified oil is discharged from the separation chamber through a central light phase outlet.
  • the separated particles and the liquid separation aid are discharged from the separation chamber through a heayy phase outlet situated radially outside of the light phase outlet.
  • Mineral oils also half- and full-synthetic as well as animal oils and vegetable oils, with or without additives, are used widely in industry for various purposes, such as lubrication, cooling and insulation. During such use the oils commonly become contaminated by different kinds of particles. De- pending on the composition and the particular use different methods for regeneration of contaminated oils are used.
  • US 4 491 515 describes purification of lubricating oil which has been used in vehicles.
  • the oil which may contain many kinds of contaminants, is purified by addition of a compound containing a carbonyl group (keto- ne) mixed with a water-containing electrolyte, for example an inorganic or organic acid.
  • keto- ne a compound containing a carbonyl group
  • a water-containing electrolyte for example an inorganic or organic acid.
  • US 4 519 899 describes purification of rolling oil which has been contaminated with particles of the material which has been treated at the rolling operation.
  • a coagulating agent as for example a water-containing soda solution, is mixed with the oil in a carefully controlled amount. The particles coagulate and are found in the water phase, which may be removed by settling or in a centrifugal separator.
  • SE 512 750 there is described a method for gravimetric separation of an oil which is contaminated with particles and/or water.
  • a collection polymer or polymer mixture which is not soluble in oil, is added to the contaminated oil and mixed with the same, after which separation of the oil and the collection polymer occurs.
  • the collection po- lymer and the main part of the contaminants form a bottom phase, while the oil forms a top phase.
  • the bottom phase with the collection polymer and the contaminants is removed.
  • the separation may take place by centrifugation.
  • the contaminants in the shape of particles, which are to be removed from the oil may in many cases be very small and difficult to remove from the oil.
  • the amount of particles may also be small.
  • the amount of separating aid that must be added may therefore be comparatively small. To separa- te two liquid phases of different density from each other in a centrifugal separator may cause problem if one of the phases is present only in a small amount.
  • the present invention offers a solution to this problem.
  • the separation chamber of the centrifugal rotor is pre-charged with a starting liquid, which is heavier than the oil and insoluble therein, in an amount such that a layer of the starting liquid forms a liquid sea! in the centrifugal rotor, covering said heavy phase outlet. Only after such pre-charging of the separation chamber the contaminated oil and the liquid separation aid are supplied to the separation chamber, at least part of the starting liquid together with liquid separation aid and particles, separated from the oil, being discharged from the separation chamber through said heavy phase outlet.
  • the invention may with advantage be carried through in such a manner that an amount of the liquid separation aid is used as said starting liquid.
  • an amount of the liquid separation aid is used as said starting liquid.
  • it may be suitable to use a starting liquid of a different kind to form the liquid seal in order to restrict the amount of liquid separation aid needed.
  • a different kind of starting liquid may be water, for instance.
  • oils which may be cleaned by the proposed method, there can be mentioned oils used for insulation purpose in transformers and tap changers, rolling oils, hydraulic oils and lubricating oils.
  • the choice of the liquid separating aid depends on the oil, which is to be purified.
  • the oils mentioned above may be pure mineral oils, half- or full- synthetic oils, or animal or vegetable oils with or without additives giving the oils their desired properties.
  • the choice of separating aid is also dependent on the kind of contaminating particles, which are to be removed from the oil. As may be understood from the prior art mentioned above different combinations of separating aids are available.
  • the liquid separation aid may or may not contain water or be soluble in water. The used separation aid should however be insoluble in oil. Depending on the amount of contaminated particles a larger or smaller amount of separa- ting aid is added. -
  • the separating aid may contain substances causing flocculation of the particles, which gives heavier particles more easily removable by centrifugal separation.
  • the separating aid may also attract or bind the particles by way of chemical or surface chemical bonds.
  • liquid separation aid takes place together with the oil.
  • the liquid separation aid and the oil may, if so is considered suitable, be mixed in some kind of mixer connected to the inlet of the centrifugal separator or in a separate mixing ope- ration prior to the purification.
  • a desired holding time for the mixture of oil and liquid separating aid may be obtained prior to the purification.
  • the method according to the invention may advantageously be used for purification of mineral or synthetic oils containing additives in order to give the oil the desired properties for the intended application, at which the density of the oils lie in the interval of 0, 85 - 1 ,05 g/cm 3 at 40 °C.
  • the method of the invention may with advantage be used for mineral oils, which have been contaminated with very small particles, for example very small soot particles or metal. particles which are floating in the oil and therefore do not settle.
  • Mineral oils have usually a density of 0,85 - 0,90 g/cm 3 at 40 °C.
  • kieselguhr or bleaching clay filters which filter materials are expensive and create problems in connection with deposition of the used filter beds.
  • the separation aid with advantage may be a liquid polymer, Which binds the small soot particles that are present in the oil. Also rolling oil as well as chlorine-paraffin oil contaminated with very small metal particles may be cleaned in this way.
  • the oil to be purified may also be lubricating oil for Diesel engines, contaminated with small dispersed particles, the separation aid being a liquid polymer.
  • a suitable liquid polymer for purification of these kinds of oils is a polyhydroxy alkoxylate with a density of 1 ,0 - 1 , 1 g/cm 3 at 40 °C.
  • a mineral oil that has been used as an insulating agent in a tap changer and is contaminated with soot particles should be purified from the same.
  • the amount of oil in the tap changer may be 200 - 1500 litres.
  • a mobile centrifugal separator MIB303S-13 from Alfa Laval AB.
  • the oil contains 1 - 10% soot.
  • the rotor of the centrifugal separator is started and is brought to rotate at full speed. Separation aid in the form of a liquid polymer is added to the rotor in an amount of 0,7 1.
  • the polymer is forced to flow to the outer part of the separation chamber of the rotor by centrifugal force, where it forms a liquid layer rotating with the rotor and covers a heavy phase outlet of the separation chamber.
  • the amount of polymer that is needed to form the liquid layer depends on the size and construction of the centrifugal separator.
  • the oil that is to be purified is supplied, oil having then already been mixed with polymer.
  • the amount of polymer in the supplied mixture is around 4 %.
  • the polymer that is used for the purification consists of a polyhydroxy alkoxylate.
  • Rolling oil consisting of a chlorine-paraffin oil shall be purified by the method according to the invention.
  • the oil which may contain 1-17 % sludge, is mixed with liquid polymer, a polyhydroxy alkoxylate.
  • a mobile centrifugal separator of the same kind as used in example 1 is used for the purification. Polymer is added to the centrifugal separator when the separator has been started to form the rotating liquid layer.
  • the amount of oil that is to be purified may be between 3 - 15 m 3 . Previously, contaminated oil had to be deposited at extremely high costs. Purification ac- cording to the technology now suggested, therefore, has important advantages.
  • Lubricating oil used for lubrication of Diesel engines shall be purified ac- cording to the invention.
  • the oil contains a number of additives in order to give the oil the desired properties.
  • the oil is contaminated with 0,1 to 5 % of particles mainly consisting of soot, combustion rests and reaction products from some of the additives of the oil.
  • the main part of the contaminants is present as colloidal or sub micron particles, which are impossible to remove in centrifugal separators or filters.
  • the amount of contaminants in the oil had decreased by 82 %, from 0,96 % to 0,18 % insoluble matter.
  • the centrifugal separator shown in the drawing has a stationary housing 1 , in which there is arranged a centrifugal rotor 2 rotatable about a vertical centre axis R.
  • the rotor 2 is mounted on top of a vertical driving shaft 3 coupled to a driving device (not shown).
  • a connection device 4 carried by the housing 1 includes, among other things, a vertical inlet pipe 5 extending from above into the rotor 2 and forming an inlet channel that opens into a central inlet space in the rotor. Said inlet channel communicates at its upper end with an inlet 5a of the connection device 4.
  • the rotor 2 forms a separation chamber 6 and several inlet passages 7 leading from said central inlet space in the rotor to respective inlets 8 of the separation chamber 6.
  • the rotor 2 also forms a central light phase outlet 9 of the separation chamber 6 at a relatively small distance from the centre axis R and, at a greater distance from the centre axis R, a number of heavy phase outlets 10 of the separation chamber 6.
  • the light phase outlet 9 is in the form of an overflow outlet leading to an outlet chamber 11 in the upper part of the rotor 6.
  • a paring disc 12 which is supported by the connec- tion. device 4 and has at least one paring channel 13 communicating with an outlet 14 of the connection device.
  • the heavy phase outlets 10 of the separation chamber communicate through channels 15 with an overflow outlet 16 of the rotor, opening to a space 17 in the housing 1 below the rotor 2.
  • the centrifugal separator in the drawing operates in the following manner when used for cleaning oil from small particles suspended therein by means of a separation aid in liquid form, e.g. a liquid polymer.
  • the separation aid is insoluble in the oil to be cleaned and has a density larger than that of the oil.
  • a certain amount of separation aid, or another starting liquid heavier than the oil to be cleaned is supplied through the rotor inlet into the separation chamber 6.
  • This starting liquid forms, when the rotor is rotating, a liquid layer in the radially outermost part of the separation chamber, covering the heavy phase outlets 10 thereof.
  • a mixture of oil to be cleaned and said liquid separation aid is supplied into the separation chamber at any predetermined rate, preferably continuously.
  • the mixture enters the separation chamber though its inlets 8 and flows axially through aligned distribution holes in the separation discs 18 into the various interspaces between the discs. In these interspaces, or flow paths, the oil part of the mixture flows inwardly towards the centre axis R, whereas the dispersed separation aid, together with particles contaminating the oil, moves outwardly away from the centre axis R.
  • Oil having been freed from particles and separation aid leaves the separation chamber 6 through its central light phase outlet 9 and flows further on, via the outlet chamber 11 and through the paring disc 12, out through the outlet 14 of the connection device 4.
  • the dispersed separation aid and the particles move out into the aforementioned layer of starting liquid, which may also be liquid separation aid.
  • From the outer part of the separation chamber 6 at least part of the starting liquid, together with separation aid and particles, separated from the oil, leave the separation cham- ber through its heavy phase outlets 10 and flow further on, via the outlet channels 15, to and out through the overflow outlet 16 of the rotor 2 to the space 17 below the rotor.
  • the layer of starting liquid forms an inner cylindrical liquid surface at a first radial level in the separation chamber. Then, when oil to be cleaned is supplied, the cylindrical surface of the starting liquid is displaced radially outwardly to a second level. This second level should be situated radially inwardly of the heavy phase outlets 10.
  • the amount of starting liquid to be supplied must be accurately determined, so that this liquid can form a liquid seal in the rotor during the initial part of the separation process, preventing escape of oil through the outlets 10.
  • there is always an interface layer formed between oil and separation aid having been separated from the oil said interface layer being maintained at a level radially inside of the heavy phase outlets 10.
  • the centrifugal rotor 2 in the drawing has a solid wall surrounding the separation chamber 6.
  • a rotor having peripheral sludge outlets adapted to be intermittently openable during operation of the rotor, so that particles separated from the oil but not entrained by the liquid separation aid leaving through the heavy phase outlets 10 can be intermittently discharged during operation of the rotor.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Centrifugal Separators (AREA)
  • Lubricants (AREA)
  • Extraction Or Liquid Replacement (AREA)
  • Fats And Perfumes (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Abstract

For purifying contaminated oil from particles suspended in the oil by means of a centrifugal separator a liquid separation aid is used having a density higher than that of the oil. The liquid separation aid attracts/binds the contaminating particles. The contaminated oil is supplied to a separation chamber of a rotating centrifugal rotor. Purified oil is discharged through a central light phase outlet of the separation chamber, and the liquid separation aid and the separated particles are discharged through a heavy phase outlet of the separation chamber, situated radially outside of said central light phase outlet. According to the invention the purification is carried through in such a way that a starting liquid, heavier than the oil and insoluble therein, is supplied to the separation chamber in an amount such that a layer of the starting liquid forms a liquid seal in the rotating centrifugal rotor, covering said heavy phase outlet. Only after this, contaminated oil and the liquid separation aid are supplied to the separation chamber. While purified oil leaves the separation chamber through said light phase outlet, at least part of the starting liquid and the liquid separation aid together with particles, separated from the oil, are discharged through the heavy phase outlet.

Description

A method of purifying contaminated oil from particles suspended in the oil in a centrifugal separator
The present invention relates to a method of purifying contaminated oil from particles suspended in the oil by means of a liquid separation aid, which has a density larger than that of the oil. The separation aid is dispersed in the contaminated oil in order to make the particles more easily separable from the oil. The contaminated oil and the liquid separation aid are supplied into a separation chamber of a rotating centrifugal rotor. The liquid separation aid and the particles are separated from the oil by centrifugal force. The purified oil is discharged from the separation chamber through a central light phase outlet. The separated particles and the liquid separation aid are discharged from the separation chamber through a heayy phase outlet situated radially outside of the light phase outlet.
Mineral oils (also half- and full-synthetic) as well as animal oils and vegetable oils, with or without additives, are used widely in industry for various purposes, such as lubrication, cooling and insulation. During such use the oils commonly become contaminated by different kinds of particles. De- pending on the composition and the particular use different methods for regeneration of contaminated oils are used.
Since long contaminated oils have been filtered in filter beds containing clay, bleaching earth or kieselguhr.
Purification of mineral oils from suspended particles is described for example in US 4 094 770. According to this patent the particles that are not filtrated away are removed by addition of an agglomerating aid in the form of a mixture of acetone and 2-butanone. The agglomerated particles settle and may be removed from the oil. A finishing distillation step is necessary in order to purify the oil from the agglomerating aid.
US 4 491 515 describes purification of lubricating oil which has been used in vehicles. The oil, which may contain many kinds of contaminants, is purified by addition of a compound containing a carbonyl group (keto- ne) mixed with a water-containing electrolyte, for example an inorganic or organic acid. When this acid has been added to the oil, there is relatively rapidly obtained an agglomeration of particulate contaminants that may be removed by settling or centrifugation. The ketone is recovered in a distillation step.
US 4 519 899 describes purification of rolling oil which has been contaminated with particles of the material which has been treated at the rolling operation. A coagulating agent, as for example a water-containing soda solution, is mixed with the oil in a carefully controlled amount. The particles coagulate and are found in the water phase, which may be removed by settling or in a centrifugal separator.
In SE 512 750 there is described a method for gravimetric separation of an oil which is contaminated with particles and/or water. According to this method a collection polymer or polymer mixture, which is not soluble in oil, is added to the contaminated oil and mixed with the same, after which separation of the oil and the collection polymer occurs. The collection po- lymer and the main part of the contaminants form a bottom phase, while the oil forms a top phase. The bottom phase with the collection polymer and the contaminants is removed. According to this publication the separation may take place by centrifugation. The contaminants in the shape of particles, which are to be removed from the oil, may in many cases be very small and difficult to remove from the oil. The amount of particles may also be small. The amount of separating aid that must be added may therefore be comparatively small. To separa- te two liquid phases of different density from each other in a centrifugal separator may cause problem if one of the phases is present only in a small amount.
The present invention offers a solution to this problem.
According to the invention, in use of a method as initially defined, the separation chamber of the centrifugal rotor is pre-charged with a starting liquid, which is heavier than the oil and insoluble therein, in an amount such that a layer of the starting liquid forms a liquid sea! in the centrifugal rotor, covering said heavy phase outlet. Only after such pre-charging of the separation chamber the contaminated oil and the liquid separation aid are supplied to the separation chamber, at least part of the starting liquid together with liquid separation aid and particles, separated from the oil, being discharged from the separation chamber through said heavy phase outlet.
The invention may with advantage be carried through in such a manner that an amount of the liquid separation aid is used as said starting liquid. In this way only one kind of auxiliary liquid has to be used. On the other hand it may be suitable to use a starting liquid of a different kind to form the liquid seal in order to restrict the amount of liquid separation aid needed. Such a different kind of starting liquid may be water, for instance. Among the oils, which may be cleaned by the proposed method, there can be mentioned oils used for insulation purpose in transformers and tap changers, rolling oils, hydraulic oils and lubricating oils.
The choice of the liquid separating aid depends on the oil, which is to be purified. The oils mentioned above may be pure mineral oils, half- or full- synthetic oils, or animal or vegetable oils with or without additives giving the oils their desired properties. The choice of separating aid is also dependent on the kind of contaminating particles, which are to be removed from the oil. As may be understood from the prior art mentioned above different combinations of separating aids are available. The liquid separation aid may or may not contain water or be soluble in water. The used separation aid should however be insoluble in oil. Depending on the amount of contaminated particles a larger or smaller amount of separa- ting aid is added. -
The separating aid may contain substances causing flocculation of the particles, which gives heavier particles more easily removable by centrifugal separation. The separating aid may also attract or bind the particles by way of chemical or surface chemical bonds.
By filling a radially outer space in the aforementioned rotor with said starting liquid, e.g. liquid separation aid, before oil purification is started, an efficient purification can be obtained immediately. If, instead, conta- minated oil mixed with liquid separation aid had been supplied to the rotating rotor from the start, a considerable amount of oil would be discharged through the separation chamber outlet for heavy phase, before a liquid seal covering this outlet had been formed in the rotor by liquid separation aid separated from the contaminated oil. When the centrifugal rotor contains separation discs improving the separation, an interface level between oil and separation aid is maintained, in a steady state process, in the vicinity of the outer edges of the separation discs.
According to the invention a continuous addition of liquid separation aid takes place together with the oil. The liquid separation aid and the oil may, if so is considered suitable, be mixed in some kind of mixer connected to the inlet of the centrifugal separator or in a separate mixing ope- ration prior to the purification. In the last mentioned case a desired holding time for the mixture of oil and liquid separating aid may be obtained prior to the purification.
The method according to the invention may advantageously be used for purification of mineral or synthetic oils containing additives in order to give the oil the desired properties for the intended application, at which the density of the oils lie in the interval of 0, 85 - 1 ,05 g/cm3 at 40 °C.
The method of the invention may with advantage be used for mineral oils, which have been contaminated with very small particles, for example very small soot particles or metal. particles which are floating in the oil and therefore do not settle. Mineral oils have usually a density of 0,85 - 0,90 g/cm3 at 40 °C. Earlier the only possibility to purify oil containing this kind of contaminants have been to use kieselguhr or bleaching clay filters, which filter materials are expensive and create problems in connection with deposition of the used filter beds.
If the mineral oil has been used as an insulating agent in a transformer or tap changer and is free from additives apart from a necessary oxidation inhibitor, the separation aid with advantage may be a liquid polymer, Which binds the small soot particles that are present in the oil. Also rolling oil as well as chlorine-paraffin oil contaminated with very small metal particles may be cleaned in this way.
The oil to be purified may also be lubricating oil for Diesel engines, contaminated with small dispersed particles, the separation aid being a liquid polymer.
One example of a suitable liquid polymer for purification of these kinds of oils is a polyhydroxy alkoxylate with a density of 1 ,0 - 1 , 1 g/cm3 at 40 °C.
Example 1
A mineral oil that has been used as an insulating agent in a tap changer and is contaminated with soot particles should be purified from the same. The amount of oil in the tap changer may be 200 - 1500 litres. For the purification there is used a mobile centrifugal separator MIB303S-13 from Alfa Laval AB. Depending on the time interval between consecutive purification operations the oil contains 1 - 10% soot. The rotor of the centrifugal separator is started and is brought to rotate at full speed. Separation aid in the form of a liquid polymer is added to the rotor in an amount of 0,7 1. The polymer is forced to flow to the outer part of the separation chamber of the rotor by centrifugal force, where it forms a liquid layer rotating with the rotor and covers a heavy phase outlet of the separation chamber. The amount of polymer that is needed to form the liquid layer depends on the size and construction of the centrifugal separator. When the layer has been formed the oil that is to be purified, is supplied, oil having then already been mixed with polymer. The amount of polymer in the supplied mixture is around 4 %. The polymer that is used for the purification consists of a polyhydroxy alkoxylate. Example 2
Rolling oil consisting of a chlorine-paraffin oil shall be purified by the method according to the invention. The oil, which may contain 1-17 % sludge, is mixed with liquid polymer, a polyhydroxy alkoxylate. A mobile centrifugal separator of the same kind as used in example 1 is used for the purification. Polymer is added to the centrifugal separator when the separator has been started to form the rotating liquid layer. The amount of oil that is to be purified may be between 3 - 15 m3. Previously, contaminated oil had to be deposited at extremely high costs. Purification ac- cording to the technology now suggested, therefore, has important advantages.
Example 3
Lubricating oil used for lubrication of Diesel engines shall be purified ac- cording to the invention. The oil contains a number of additives in order to give the oil the desired properties.
The oil is contaminated with 0,1 to 5 % of particles mainly consisting of soot, combustion rests and reaction products from some of the additives of the oil. The main part of the contaminants is present as colloidal or sub micron particles, which are impossible to remove in centrifugal separators or filters.
50 litres of the contaminated lubricating oil is mixed by stirring with about 4 % liquid polymers, a polyhydroxy alkoxylate. The mixture is heated to a temperature of 95 °C. In order to separate the polymer entraining the contaminants use is made of a centrifugal rotor of the same kind as in example 1 , which is pre-charged with a polymer layer before the oil/polymer mixture is supplied into it. The result of the extraction was measured by analysis of the oil prior to and after the purification in respect of insoluble matter in n-pentan (ASTM D 893-892).
The amount of contaminants in the oil had decreased by 82 %, from 0,96 % to 0,18 % insoluble matter.
The method according to the invention is further described below with reference to the attached drawing, which shows a centrifugal separator suitable for carrying through the method of the invention.
The centrifugal separator shown in the drawing has a stationary housing 1 , in which there is arranged a centrifugal rotor 2 rotatable about a vertical centre axis R. The rotor 2 is mounted on top of a vertical driving shaft 3 coupled to a driving device (not shown). A connection device 4 carried by the housing 1 includes, among other things, a vertical inlet pipe 5 extending from above into the rotor 2 and forming an inlet channel that opens into a central inlet space in the rotor. Said inlet channel communicates at its upper end with an inlet 5a of the connection device 4.
The rotor 2 forms a separation chamber 6 and several inlet passages 7 leading from said central inlet space in the rotor to respective inlets 8 of the separation chamber 6. The rotor 2 also forms a central light phase outlet 9 of the separation chamber 6 at a relatively small distance from the centre axis R and, at a greater distance from the centre axis R, a number of heavy phase outlets 10 of the separation chamber 6.
The light phase outlet 9 is in the form of an overflow outlet leading to an outlet chamber 11 in the upper part of the rotor 6. In this outlet chamber 11 there is arranged a paring disc 12, which is supported by the connec- tion. device 4 and has at least one paring channel 13 communicating with an outlet 14 of the connection device.
The heavy phase outlets 10 of the separation chamber communicate through channels 15 with an overflow outlet 16 of the rotor, opening to a space 17 in the housing 1 below the rotor 2.
Within the separation chamber 6 there is a stack of conical separation discs 18, which are arranged coaxially with the centre axis R and delimit between themselves thin passages for through flow of liquid under treatment in the rotor.
The centrifugal separator in the drawing operates in the following manner when used for cleaning oil from small particles suspended therein by means of a separation aid in liquid form, e.g. a liquid polymer. The separation aid is insoluble in the oil to be cleaned and has a density larger than that of the oil.
Either before or after the rotor has been brought in rotation about the centre axis R, a certain amount of separation aid, or another starting liquid heavier than the oil to be cleaned, is supplied through the rotor inlet into the separation chamber 6. This starting liquid forms, when the rotor is rotating, a liquid layer in the radially outermost part of the separation chamber, covering the heavy phase outlets 10 thereof.
After the separation chamber 6 has been pre-charged with said amount of a starting liquid, a mixture of oil to be cleaned and said liquid separation aid is supplied into the separation chamber at any predetermined rate, preferably continuously. The mixture enters the separation chamber though its inlets 8 and flows axially through aligned distribution holes in the separation discs 18 into the various interspaces between the discs. In these interspaces, or flow paths, the oil part of the mixture flows inwardly towards the centre axis R, whereas the dispersed separation aid, together with particles contaminating the oil, moves outwardly away from the centre axis R.
Oil having been freed from particles and separation aid leaves the separation chamber 6 through its central light phase outlet 9 and flows further on, via the outlet chamber 11 and through the paring disc 12, out through the outlet 14 of the connection device 4. The dispersed separation aid and the particles move out into the aforementioned layer of starting liquid, which may also be liquid separation aid. From the outer part of the separation chamber 6 at least part of the starting liquid, together with separation aid and particles, separated from the oil, leave the separation cham- ber through its heavy phase outlets 10 and flow further on, via the outlet channels 15, to and out through the overflow outlet 16 of the rotor 2 to the space 17 below the rotor.
At the time when said starting liquid has been supplied into the separation chamber 6, but before any oil to be cleaned has been supplied, the layer of starting liquid forms an inner cylindrical liquid surface at a first radial level in the separation chamber. Then, when oil to be cleaned is supplied, the cylindrical surface of the starting liquid is displaced radially outwardly to a second level. This second level should be situated radially inwardly of the heavy phase outlets 10. Thus, the amount of starting liquid to be supplied must be accurately determined, so that this liquid can form a liquid seal in the rotor during the initial part of the separation process, preventing escape of oil through the outlets 10. In a steady state separation process there is always an interface layer formed between oil and separation aid having been separated from the oil, said interface layer being maintained at a level radially inside of the heavy phase outlets 10.
The centrifugal rotor 2 in the drawing has a solid wall surrounding the separation chamber 6. However, it may be desirable sometimes to use, instead, a rotor having peripheral sludge outlets adapted to be intermittently openable during operation of the rotor, so that particles separated from the oil but not entrained by the liquid separation aid leaving through the heavy phase outlets 10 can be intermittently discharged during operation of the rotor.

Claims

Claims
1. A method of purifying contaminated oil from particles suspended there in by means of a liquid separation aid having a density larger than that of the oil and being dispersed in the contaminated oil in order to make the particles more easily separable from the oil, the method comprising
- supplying said contaminated oil and said liquid separation aid into a separation chamber of a rotating centrifugal rotor,
- separating in said separation chamber the particles and the liquid separation aid from the oil by centrifugal force,
- discharging purified oil from the separation chamber through a central light phase outlet thereof and
- discharging separated particles together with separated liquid separation aid from the separation chamber through a heavy phase outlet of the separation chamber, situated radially outside said central light phase outlet,
c h a r a c t e r i z e d b y
- pre-charging the separation chamber, before supplying a substantial amount of contaminated oil thereinto, with a starting liquid, which is heavier than the oil and insoluble therein, in an amount such that a layer of the starting liquid forms a liquid seal in the centrifugal rotor, covering said heavy phase outlet, - supplying thereafter said contaminated oil and said liquid separation aid into the separation chamber, and
- discharging from the separation chamber through said heavy phase outlet at least part of said starting liquid and particles together with liquid separation aid, separated from the oil.
2. A method according to claim 1, characterized by using as said starting liquid an amount of said liquid separation aid.
3. A method according to claim 1, characterized in that the oil is a mineral or synthetic oil containing additives giving the oil desired properties for its intended use, the density of the oil being in the interval 0,85 -
1 ,05 g/cm3 at 40°C.
4. A method according to claim 3, characterized in that the oil is a pure mineral oil having a density of 0,85 - 0,90 g/cm3 at 40 °C.
5. A method according to claim 4, characterized in that the mine- ral oil is one that has been used as an insulating agent in a transformer or tap changer, is free from additives, apart from necessary oxidation inhibitor, and is contaminated with very small soot particles, the separation aid being a liquid polymer.
6. A method according to claim 3, characterized in that the oil is one that has been used as a lubrication oil for Diesel engines and is contaminated with small dispersed particles, the separation aid being a liquid polymer.
7. A method according to claim 5 or 6, characterized in that the polymer is a polyhydroxy alkoxylate having a density of 1 ,0-1,1 g/cm3 at 0 °C.
PCT/SE2003/001925 2002-12-12 2003-12-10 A method of purifying contaminated oil from particles suspended in the oil in a centnrifugal separator WO2004053035A1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
AT03812745T ATE438700T1 (en) 2002-12-12 2003-12-10 METHOD FOR CLEANING CONTAMINATED OIL BY SEPARATING PARTICLES SUSPENDED IN THE OIL IN A CENTRIFUGAL SEPARATOR
AU2003302920A AU2003302920A1 (en) 2002-12-12 2003-12-10 A method of purifying contaminated oil from particles suspended in the oil in a centnrifugal separator
DE60328710T DE60328710D1 (en) 2002-12-12 2003-12-10 PROCESS FOR CLEANING CONTAMINATED OIL BY SEPARATION OF PARTICLES SUSPENDED IN THE OIL IN A CENTRIFUGAL SEPARATOR
JP2004558969A JP4620470B2 (en) 2002-12-12 2003-12-10 How to remove particles suspended in oil in a centrifuge from contaminated oil
EP03812745A EP1570036B1 (en) 2002-12-12 2003-12-10 A method of purifying contaminated oil from particles suspended in the oil in a centrifugal separator
US10/538,295 US7410456B2 (en) 2002-12-12 2003-12-10 Method of purifying contaminated oil in a centrifugal separator using a separation aid and starting liquid
DK03812745T DK1570036T3 (en) 2002-12-12 2003-12-10 Process for cleaning contaminated oil from articles suspended in the oil in a centrifugal separator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0203699A SE524469C2 (en) 2002-12-12 2002-12-12 When cleaning oil from polluting particles, put in a centrifugal separator
SE0203699-4 2002-12-12

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WO2004053035A1 true WO2004053035A1 (en) 2004-06-24

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AT (1) ATE438700T1 (en)
AU (1) AU2003302920A1 (en)
DE (1) DE60328710D1 (en)
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WO2008140378A1 (en) * 2007-05-10 2008-11-20 Alfa Laval Corporate Ab Method and device for cleaning of a fluid in a centrifugal separator
GB2487967A (en) * 2011-02-11 2012-08-15 Michael Taylor Removing particles from oil
RU2505360C1 (en) * 2012-07-26 2014-01-27 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Оренбургский государственный университет" Radial flow separator-cleaner
EP2712912A1 (en) * 2012-09-27 2014-04-02 Alfa Laval Corporate AB Continuous purification of motor oils
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EP2155399A4 (en) * 2007-05-10 2017-03-08 Alfa Laval Corporate AB Method and device for cleaning of a fluid in a centrifugal separator
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US8790233B2 (en) 2007-05-10 2014-07-29 Alfa Laval Corporate Ab Method and device for cleaning of a fluid in a centrifugal separator
GB2487967A (en) * 2011-02-11 2012-08-15 Michael Taylor Removing particles from oil
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SE0203699D0 (en) 2002-12-12
SE0203699L (en) 2004-06-13
JP2011032477A (en) 2011-02-17
DK1570036T3 (en) 2009-10-26
KR20050085497A (en) 2005-08-29
AU2003302920A1 (en) 2004-06-30
CN100354400C (en) 2007-12-12
DE60328710D1 (en) 2009-09-17
EP1570036B1 (en) 2009-08-05
EP1570036A1 (en) 2005-09-07
US7410456B2 (en) 2008-08-12
CN1726273A (en) 2006-01-25
SE524469C2 (en) 2004-08-10
JP2006509857A (en) 2006-03-23
JP4620470B2 (en) 2011-01-26
RU2330873C2 (en) 2008-08-10
KR101066748B1 (en) 2011-09-21
US20060217254A1 (en) 2006-09-28
JP5139484B2 (en) 2013-02-06
RU2005121899A (en) 2006-01-20
ATE438700T1 (en) 2009-08-15

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