GB2471086A

GB2471086A - Extending engine lubricant life

Info

Publication number: GB2471086A
Application number: GB0910292A
Authority: GB
Inventors: John Mcneil
Original assignee: Aquafuel Research Ltd
Current assignee: Aquafuel Research Ltd
Priority date: 2009-06-16
Filing date: 2009-06-16
Publication date: 2010-12-22
Also published as: GB0910292D0

Abstract

The present invention relates to a system and method for extending lubricant life in an engine fuelled by glycerine or other polyol-containingfuels. The system 6 is arranged to draw off a fraction of the lubricating oil from the engine 1, process this oil to remove the contaminants and then return the oil to the engine. In this process, the lubricating oil that is removed from the engine is passed over a heated surface under reduced pressure to vaporize the contaminants and remove them from the lubricating oil. The system 6 may be used to continuously remove contaminants from the lubricating oil without disrupting the running of the engine 1.

Description

ENGINE LUBRICATION

BACKGROUND

a. Field of the Invention

The present invention relates to a system and method for extending lubricant life in an internal combustion engine fuelled by glycerine or other polyol-containing fuels.

b. Related Art Biodiesel is a fuel made by the transesterification of vegetable oil or animal fat (tallow) which can be used in unmodified diesel engines. The process of making biodiesel involves the reaction of these oils or fats with short-chain aliphatic alcohols. Because animal fats and oils are typically made of triglycerides which are esters of fatty acids with glycerol, a by-product of the transesterification process is glycerol. Therefore, biodeisel manufactured in this way inevitably contains some glycerol as a contaminant.

In addition to biodiesel, other fuels are known that comprise glycerol. For example, WO 2008075003 discloses a fuel composition comprising glycerol and a combustion improving agent. Furthermore it is also known to use tallow as a fuel, and WO 0005492 describes a method of combusting tallow in an internal combustion engine. !n this case, glycerol may also be present due to partial hydrolysis of the tallow.

It is often found that some fuel gets entrained into the lubricating oil of the engine.

This is generally undesirable; however, if the fuel contains hydroxyl-containing contaminants this can be extremely detrimental to the lifetime of the lubricant, and may lead to engine failure.

In an article by Jim Fitch entitled "Four Lethal Diesel Engine Oil Contaminants" (Machinery lubrication, May 2007), glycol was listed as one of the four lethal contaminants. The article stated that glycol contamination greatly increases wear rates, increases oil viscosity which impairs lubrication and oil cooling and can lead to cold seizure of engines.

These same problems will a'so occur with other hydroxyl-containing contaminants such as glycerol or other polyols.

Several methods are already known for the removal of various contaminants from lubricants. WO 2004011784 describes a system and method to extend lubricant life in an internal combustion exhaust gas recirculation (EGR) system, by using a chemical filter to remove acidic contaminants. However, this system and method is not applicable to polyol contamination.

A number of patents disclose the use of centrifugal separators to remove contaminants from lubricating oil, in particular, KR 920004202, KR 920004201, IN 192867, DE 10350562, GB 2297505, DE 4300731 and EP 0606578. However, these methods would be difficult to use to remove glycerol or other polyols, which may have a density very close to that of the lubricating oil itself. Furthermore, it is imperative that polyols remain dispersed in the lubricant to prevent them forming polymers that would block the lines and may lead to engine seizure. The surfactants and dispersants in the system required to do this then make it very difficult to separate the polyols by centrifugation.

US patent 6083406 describes a method for improved in-line contaminant removal from engine lubricating oil which uses gravity to achieve a desired flow rate of oil.

The invention is adapted for use with an existing engine oil lubrication system and continuously processes a side stream of oil that, after processing, is returned to the main flow of engine oil. During processing, the oil is first filtered and then drained and deposited upon the upper central surface portions of a heated dome whereon the oil forms a thin film from which relatively low boiling volatile impurities (especially water) are rapidly separated in a gaseous state. The gas is vented through a pressure relief valve to the manifold while the recovered reconditioned oil is collected and recycled. The surface of the dome is heated to about 160 to °F (71 -93 °C) and evaporation proceeds at ambient pressure. However, this method is not applicable to the removal of polyols such as glycols and glycerine as these have high boiling points.

Therefore, there is a need to provide a system and method for removing higher boiling point contaminants such as polyols from lubricating oils in order to extend the life of the lubricant.

SUMMARY OF THE INVENTION

Aspects of the invention are specified in the independent claims. Preferred features are specified in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be further described, by way of example only, and with reference to Figure 1 which is a schematic drawing of a system for removing contaminants according to a preferred embodiment of the invention.

DETAILED DESCRIPTION

In an internal combustion engine 1 lubricating oil is generally held in an oil sump 2 or oil pan below the crankshaft 4. The lubricating oil is then pumped, through an oil filter, to the required parts of the engine, for example the bearings. The oil then drains back to the sump 2 and is continually recirculated.

Figure 1 shows a schematic of a system 6 used to remove contaminants from the lubricating oil. Typically these contaminants will include organic and high boiling point substances, for example polyols. In a preferred embodiment, the system 6 is used to remove glycerol from the lubricating oil. The system 6 is arranged to draw off a fraction of the lubricating oil from the engine 1, process this oil to remove the contaminants and then return the oil to the engine. In this way the system 6 may be used to continuously remove contaminants from the lubricating oil whilst the engine I is used, without the need to drain the engine.

In this system, the fraction of oil to be processed is removed from a collection zone 2 of the engine. In a preferred embodiment, the collection zone is in the oil sump 2. In this embodiment the oil is pumped from the oil sump 2 using any suitable pump 8 and is fed into a contaminant removal assembly 10. The oil could alternatively be transferred by other means, for example by gravity feed.

The contaminant removal assembly 10 includes an evaporator 12 which has a heat exchange surface held at an elevated temperature. The heat exchange surface is typically the hot walls of the chamber of the evaporator 12. The contaminant removal assembly 10 also comprises means 14 for generating reduced pressures in the evaporator. Typically the reduced pressure will be generated by a suitable vacuum pump 14. Preferably the reduced pressure in the chamber of the evaporator 12 is a few millibar, notably less than 20 millibar; more preferably the pressure is less than 10 millibar. The lubricating oil to be treated is discharged into the evaporator 12 under this reduced pressure and this causes the stream of oil to spread out into a thin film over the heat exchange surface.

The reduced operating pressure of the evaporator causes the boiling points of the contaminants to decrease. Therefore, higher boiling point contaminants such as polyols, and in particular glycerol, that would otherwise have too high a boiling point under normal or ambient pressure, are vaporized when they come into contact with the hot surface of the heat exchanger. Furthermore, because the oil is spread into a thin film, a large amount of the oil is in contact with or in close proximity to the hot surface of the heat exchanger. Therefore, the residence time of the lubricating oil in the evaporator 12 may be reduced. In a preferred embodiment of the invention, the evaporator 12 is a thin (falling-film short path) evaporator. More preferably the evaporator 12 is a wiped-film (short path) evaporator in which the thin film of lubricating oil is created by wiper blades that move over the surface of the heated walls of the evaporator 12. The wipers pump the liquid through the chamber of the evaporator 12 and are particularly advantageous when processing viscous fluids.

The contaminant vapours that are formed then pass to a condenser 16. The vapours condense on the cold surfaces within the condenser 16 and the resultant liquid is removed. The condenser 16 may be external to the evaporator, as shown for clarity in Figure 1, or more preferably the condenser 16 is an internal condenser. In this case, the evaporator 12 may be a short-path evaporator. This has the advantage that higher vacuums may be achieved in the evaporator 12 (and the heavy vapour has less distance to travel before condensing), further lowering the boiling point of glycerol or other contaminants. Importantly, the residence time of the lubricating oil in the evaporator 12 should be kept as short as possible to prevent unwanted degradation of the oil.

The recovered oil that has passed through the evaporator 12, and which is now substantially free of contaminants, is then returned to the engine 1. In this embodiment the oil flows back into a return zone 2 of the engine, which is preferably the same as the collection zone 2, and in this case is the oil sump 2.

The treated oil could optionally be returned to the engine by other means, for

example by pumping.

Removing the oil from and returning the oil to the same zone of the engine 1, in this case the oil sump 2, allows the processed lubricating oil to mix quickly and efficiently with the rest of the oil in the engine 1 as this zone is continually agitated by the pump 8 removing a fraction of the oil to the contaminant removal assembly 10.

This process has the advantage that the lubricating oil can be cleaned quickly.

Furthermore, by drawing off a fraction of the lubricating oil from the engine in the way described, the process can be continuous and does not interrupt the running of the engine.

Claims

CLAIMS1. A method of removing contaminants from lubricating oil in an internal combustion engine fuelled by glycerine or other polyol-containing fuels, the method comprising: -transferring lubricating oil from said engine into a reduced pressure chamber having a heated surface, so that the transferred oil spreads over the heated surface to vaporize at least some of the contaminants; and -returning the lubricating oil to the engine.
2. A method as claimed in Claim 1, further comprising condensing the contaminant vapour such that the contaminants are removed from the lubricating oil.
3. A method as claimed in any preceding claim, wherein the method comprises removing the lubricating oil from the oil sump of the engine.
4. A method as claimed in any preceding claim, wherein the treated lubricating oil is returned to the oil sump of the engine.
5. A method as claimed in any preceding claim, wherein the contaminants include polyols.
6. A method as claimed in Claim 5, wherein the contaminants include glycerol.
7. A system for removing contaminants from lubricating oil in an engine, the system comprising: -an inlet for connection to a collection zone of the engine for transferring lubricating oil from the engine; -an evaporator for receiving oil from the inlet, the evaporator having an internal surface and heating means for heating said surface; and -means for generating reduced pressure in the evaporator; wherein when the system is connected to the engine, lubricating oil that is transferred from the engine will be passed over the heated surface under reduced pressure to vaporize the contaminants, thereby removing them from the oil.
8. A system as claimed in Claim 7, further comprising means for transferring treated lubricating oil from the evaporator to the engine.
9. A system as claimed in Claim 7 or Claim 8, further comprising a condenser for condensing vaporised contaminants.
10. A system as claimed in any one of Claims 7-9, wherein the evaporator is a thin-film evaporator.
11. A system as claimed in Claim 10, wherein the evaporator is a wiped-film evaporator.
12. A system as claimed in Claim 11, wherein the wiped-film evaporator is a short-path wiped-film evaporator.
13. A system as claimed in any one of Claims 7-12, further comprising at least one pump for pumping oil from the engine to the condenser or from the condenser to the engine.
14. A method substantially as herein described with reference to the accompanying drawing.
15. A system substantially as herein described with reference to the accompanying drawing.