WO2014074054A1

WO2014074054A1 - Sulphur content indicator for fuel, vehicle comprising such an indicator and a method for indicating sulphur content in fuel

Info

Publication number: WO2014074054A1
Application number: PCT/SE2013/051271
Authority: WO
Inventors: Marita Nilsson; Henrik Eriksson; Baohua ZHU; Hanna Lind; Maria CONDE; Ali SARAMAT
Original assignee: Scania Cv Ab
Priority date: 2012-11-06
Filing date: 2013-10-31
Publication date: 2014-05-15
Also published as: SE536739C2; SE1251258A1

Abstract

The invention concerns a sulphur content indicator (100) for fuel (14) intended for a combustion engine (2), comprising an indicating unit (101, 201, 301, 401, 501), which is adapted so as to be arranged so that the indicating unit (101, 201, 301, 401, 501) is, by means of a surface (102, 202, 302, 402, 502), in contact with the fuel (14) for which the sulphur content is to be indicated. The indicating unit (101, 201, 301, 401, 501) has a shape that allows the fuel (14) to diffuse into the indicating unit (101, 201, 301, 401, 501) for a predetermined period of time, so that the sulphur content of the fuel (14) in the indicating unit (101, 201, 301, 401, 501) at a given distance from the surface (102, 202, 302, 402, 502) indicates the sulphur content of the fuel (14), which is detected during said period of time. The invention also concerns a vehicle (1), which comprises such a sulphur content indicator (100, 200, 300, 400, 500), and a method for indicating the sulphur content of a fuel (14) intended for a combustion engine (2).

Description

Sulphur content indicator for fuel, vehicle comprising such an indicator and a method for indicating sulphur content in fuel

BACKGROUND OF THE INVENTION AND PRIOR ART

The invention concerns a sulphur content indicator for fuel, a vehicle that comprises such an indicator and a method for indicating the sulphur content of a fuel.

Diesel-powered motor vehicles are equipped with exhaust purification devices in order to reduce emissions of particles and chemicals that are found in diesel engine exhaust. There are also various standards and legal requirements that regulate permissible exhaust emissions from vehicles. Known exhaust purification devices are sensitive to high contents of sulphur in the fuel. A content exceeding lOppm sulphur in the fuel can result in deficient emissions reduction in the exhaust purification device. To reduce the risk and ensure that standards are met, a number of vehicle manufacturers will specify the maximum sulphur content for the fuel, e.g. that the sulphur content must be less than lOppm. However, it is difficult after the fact to detect and prove that the vehicle had been filled with fuel with a sulphur content in excess of lOppm. To reduce emissions of nitrous oxides (ΝΟχ), so-called ΝΟχ reducers are often used in the exhaust flows from combustion engines in, e.g. vehicles. The efficiency of such ΝΟχ reducers decreases in the presence of impurities that contain sulphur. Such sulphurous compounds (e.g. mercaptans, thiols, thiophenes, thioethers, thioesters, disulfides) and, in particular, sulphurous aromatic compounds "poison" or react irreversibly with the catalyst for the ΝΟχ reducer. ΝΟχ reducers that have been thus affected deliver decreased efficiency. As a result of this, the presence of sulphurous compounds in the fuel can have a negative effect on exhaust emissions, and particularly on emissions of nitrous oxides.

US-2002/0079236 concerns a sensor for measuring the concentration of sulphur compounds in a liquid. The sensor comprises two electrodes, i.e. an active electrode that stands in contact with the liquid to be measured and a reference electrode that is insulated from the liquid. A voltage is generated between the electrodes in dependence upon the concentration of sulphur compounds in the liquid, which can thereby be determined.

US-2009/0317299 concerns an optical sensor for determining the sulphur content of a fuel. This is achieved by illuminating the fuel 14 with a suitable wavelength spectrum, detecting reflected light and then analyzing it to derive an detection signal that indicates the sulphur content.

Both of these known sensors are to be viewed as active insofar as they require some form of current supply in connection with the sensing process, or when the signal processing is performed. The measurements described in both these published patents provide a direct measurement result, i.e. a measurement value that reflects the current sulphur content.

The need exists to gather information concerning the maximum sulphur content of the fuel to which the vehicle has been exposed, as a fuel with an overly high sulphur content poses the risk that the function of the catalytic converter will be degraded, with the result that the exhaust emissions requirements cannot be met. In the event that the function of the catalytic converter is degraded so that the emissions requirements are not met, and if the vehicle has not been fueled with a fuel having a sulphur content that exceeds lOppm, the result in the worst case may be that the vehicle manufacturer will have to recall and repair a large number of vehicles, which can be extremely costly. On the other hand, if it is possible to prove that the instructions were not followed insofar as fuel containing, for example, more than lOppm was used, such a campaign will not be relevant. One proposed alternative to an electrically powered sensor is an indicating unit with a number of capsules or layers that, in contact with the fuel, absorb sulphur. The capsules contain liquid with mutually different sulphur contents and the layers exhibit different mutual abilities to absorb sulphur. Upon analyzing the content of sulphur in the respect capsules/layers, a determination is made as to whether the content has increased and exceeds the original content. If such is the case, it is an indication that sulphur from the fuel has been added, and that the content of sulphur in the fuel exceeded the predetermined level for the capsule/layer in question. SUMMARY OF THE INVENTION

Despite known solutions, the need exists to further develop a sulphur content indicator that provides an indication, in a simple manner, as to whether the vehicle has been filled with fuel that exceeds predetermined sulphur content levels for the fuel, which indicator requires no maintenance and thus has a low cost.

The object of the present invention is thus to provide a sulphur content indicator that provides an indication, in a simple manner, as to whether the vehicle has been filled with fuel that ex- ceeds predetermined sulphur content levels for the fuel.

An additional object of the invention is to provide a sulphur content indicator that requires no maintenance. Another object of the invention is to provide a sulphur content indicator that has a low cost.

These objects are achieved by means of a sulphur content indicator of the type described above, which is characterized by the features specified in claim 1. The sulphur content indicator for fuel according to the invention is intended for a combustion engine and comprises an indicating unit, which is adapted so as to be arranged so that the indicating unit is, by means of a surface, in contact with the fuel for which the sulphur content is to be indicated. The indicating unit is made of a material that has a predetermined fuel- absorbing capacity. The indicating unit also has a shape that enables the fuel to diffuse into the indicating unit for a predetermined period of time, so that the sulphur content of the fuel in the indicating unit at a given distance from the surface indicates the sulphur content of the fuel, which is detected during said period of time.

With such a sulphur content indicator, it is possible to determine the sulphur content that the fuel contained. Using the sulphur content indicator according to the invention it is thus possible to obtain an indication of the reason why the exhaust purification device was rendered dysfunctional. In the event that fuel with a sulphur content exceeding specified levels was used and the exhaust purification device was rendered dysfunctional, the user obtains information as to whether to use fuel with the prescribed sulphur content in future. In the event that the user had not had knowledge of the high sulphur content of the fuel, the user can impose requirements on the fuel supplier, who must state the correct sulphur content of the fuel.

The foregoing objects are also achieved by means of a vehicle that comprises a sulphur content indicator according to the foregoing. Because there are also different standards and legal requirements that regulate permissible exhaust emissions from vehicles, it is of interest to both the vehicle manufacturer and the user of the vehicle for the exhaust purification device in the vehicle to function correctly. The sulphur content indicator according to the invention provides both the vehicle manufacturer and the user with an indication as to whether the fuel that is powering the combustion engine of the vehicle has too high a sulphur content.

The foregoing objects are also achieved by means of a method for indicating the sulphur con- tent of a fuel intended for a combustion engine according to the invention. The method is performed by means of the indicating unit as per the foregoing, and comprises the steps of:

a) allowing the fuel to diffuse into the indicating unit for a predetermined period of time, b) removing the indicating unit from the surrounding fuel after the predetermined period of time,

c) extracting the fuel diffused into the indicating unit, and

d) analyzing the sulphur content of the fuel extracted from the indicating unit.

The sulphur content of the fuel can be analyzed in a simpler manner by means of the method. Further properties and advantages of the invention are presented in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described for exemplary purposes below with reference to the accompanying drawings, in which: Fig. 1 shows a schematic side view of a vehicle with a sulphur content indicator for fuel according to the prevent invention,

Fig. 2 shows a perspective view of a first embodiment of a sulphur content indicator for fuel according to the present invention,

Fig. 3 shows a view in plane of a second embodiment of a sulphur content indicator for fuel according to the present invention,

Fig. 4 shows a cross-sectional view of the sulphur content indicator along the line IV-IV in Fig. 3,

Fig. 5 shows a cross-sectional view of a third embodiment of a sulphur content indicator for fuel according to the present invention,

Fig. 6 shows a cross-sectional view of the third embodiment with the sulphur content indicator arranged with a layer that is permeable to the fuel,

Fig. 7 shows a cross-sectional view of a fourth embodiment of a sulphur content indicator for fuel according to the present invention,

Fig. 8 shows a cross-sectional view of a fifth embodiment of a sulphur content indicator for fuel according to the present invention, and

Fig. 9 shows a flow diagram of a method for indicating the sulphur content of a fuel according to the present invention.

Fig. 10 shows test results from example 1.

DETAILED DESCRIPTION

The sulphur content indicator according to the present invention comprises an indicating unit, which comprises a surface that is arranged so as to be in contact with the fuel that is to be analyzed. The surface can be in direct contact with the fuel, or contact can occur via a layer of another fuel-permeable material. The size of the surface affects how much fuel comes in contact with the indicating unit. The sulphur content indicator functions as a sampling unit and is used to collect a sample over a defined period of time from a fuel with which it is in contact. Sample collection occurs in that molecules in the fuel, which is a mixture of various com- pounds, diffuse into the material that the indicating unit contains or of which it is made. The molecules in the fuel comprise mainly hydrogen with between 10 and 22 carbon atoms, e.g. alkanes, aromatic carbohydrates, naphthenes and olefins, although the fuel also contains sul- phur impurities and other inorganic compounds such as phosphorous compounds. After a predetermined sampling period, the content in the indicating unit is analyzed using a suitable method, which is described in greater detail below. The material of the indicating unit has a predetermined fuel-absorbing capacity. The fuel- absorbing capacity of the material refers to the fact that the material has properties than enable the fuel to diffuse into the material at a given rate and in a given quantity. The diffusion rate is determined by the diffusion coefficient of the material, while the quantity depends upon the capacity of the material to absorb fuel per unit of volume. That the fuel- absorbing capacity is predetermined means that the fuel-absorbing capacity of the material is known and has been determined by means of, for example, measurements and experimentation. The fuel- absorbing capacity differs for different materials; for example, for ceramic material or polymer material, and the material is selected based on the desired fuel-absorbing capacity. Diffusion refers to the mass transport of molecules in the fuel, wherein the transport occurs randomly from one part of a system to another, i.e. without mass flow. The transport occurs, for example, from the fuel tank to the indicating unit, which constitute a system, through the random migration of individual molecules from the fuel tank to the indicating unit. The system contains at least two different types of molecules. Diffusion occurs until a state of equi- librium arises, i.e. a state in which the concentration of the molecules and/or the particles is uniform between the two different parts of the system. The diffusion is a relatively slow process.

Different molecules, such as different organic molecules, have different diffusion rates in dif- ferent materials, e.g. in a polymer material. Parameters that determine the diffusion rate consist, for example, of the temperature, the sizes of the molecules that are diffusing, concentration, free volume in the polymeric material and the friction from the medium in which the diffusion occurs. The diffusion coefficient can be defined from these parameters. The diffusion coefficients for various materials are known, and studies exist within the field, such as in the published report "Journal of Applied Polymer Science, Vol. 82, 2422-2433 (2201)

Reynier et al., "Diffusion Coefficients of Additives in Polymers I. Correlation with Geometric Parameters." The surface of the indicating unit also affects how much fuel can come in contact with the indicating unit. The greater the volume of the indicating unit and the smaller its surface (which is in contact with the fuel), the longer the time it takes to exchange the fuel in the indi- eating unit. The fuel-absorbing capacity of the material also affects the time it takes to achieve equilibrium or a state of near equilibrium. Together these properties define the exchange rate of the indicating unit. The exchange rate is slower in those parts that are located farthest away from surface than on the surface. For example, the material, the shape, the surface area and the size of the indicating unit can be chosen so that the fuel in the central parts of the indicat- ing unit is exchanged after, e.g. 4 weeks. In this way the indicating unit "saves" a representation of molecules in the fuel over a given time. This provides an indication of what types of fuels have been used over an extended period, e.g. from 1 to 3 months. The exchange times can be determined experimentally or by using various calculation models. Suitable materials for the indicating unit comprise various solid porous materials or materials based on a fiber matrix. The molecules in the fuel can diffuse into the free volumes of the porous material, which can contain, e.g. hollow spaces or pores. These hollow spaces or pores can be present in a ceramic material, in a polymer matrix or a fiber matrix. The material for the indicating unit is preferably non- selective for molecules in the fuel, and does not react with the molecules in the fuel. This means, for instance, that the material does not bind to or reject certain molecules in the fuel. Furthermore, the fuel must be extractable from the material, so that further analysis of the fuel can be performed more easily. Extraction can be performed, for example, by means of a solvent that does not react with the fuel, such as cyclohexane for diesel, or by means of heat.

The material in the indicating unit can, for example, be a ceramic material such as cement, concrete, tile, porcelain, glass or various other heat-resistant materials. Natural rubber and polymer materials such as various types of synthetic rubber, e.g. EPDM (Ethylene Propylene Diene Monomer rubber) are suitable for use in the indicating unit. The sulphur content indicator can also comprise the indicating unit in the form of fiber material of natural and/or synthetic origin. The fiber material can be based on vegetable fibers such as fibers that contain cellulose, such as paper or cardboard. Fiber materials can also consist of, for example, cotton or yarn made of cotton fibers, so-called twist. Furthermore, the material can be fiberglass- or mineral wool-based. A preferred material is synthetic rubber and, in particular, EPDM. Such a rubber is easy to manage, and diffusion can be obtained. Furthermore, such a rubber is easy to process into various shapes.

Because the exchange of molecules in the indicating unit occurs relatively slowly, it is possible to determine the sulphur content over an extended period by means of the indicating unit. For example, the material in the indicating unit can be allowed to initially absorb a "pure" fuel with a low sulphur content, so that the indicating unit is saturated. A saturated indicating unit is then disposed in the indicator, which is disposed, for example, in the fuel tank. Fuel-to-fuel diffusion subsequently takes place in the indicating unit, which diffusion occurs relatively slowly and can thus indicate the sulphur content of the fuel over an extended period. If the sulphur content in the fuel that is filled over a period of time differs from the "pure" fuel, diffusion will occur between the fuels, and a state of near equilibrium will preferably be achieved in the surface layer of the indicating unit after 1 or 2 days. This means that diffusion will occur when the fuel in the tank is exchanged, which occurs roughly every third to fourth day, and if there is a difference in sulphur content between the new and old fuel. The fuel at least on the surface layer of the indicating will then be exchanged.

The indicating unit of the indicator can be at least partially surrounded by a layer that is permeable to the fuel, which layer has the purpose of controlling the passage rate for the fuel, and the permeability is adapted so that the fuel will pass through the layer at a predetermined rate. The layer can be shaped as a membrane, and the layer can be perforated. The layer can be of a polymer material, such as fluoropolymers or fluoroelastomers, metal, e.g. aluminum foil or another material that does not react with the fuel.

The indicating unit of the indicator can be arranged in a carrier part, which makes it easier to mount the indicator in the fuel system. The carrier part is arranged so as to partially surround the indicating unit, and in this way the indicating unit can be in contact with the fuel. The car- rier part can be made of a material that is impermeable to the fuel. In this way the diffusion rate can be further reduced, if it is desirable to do so.

The carrier part can also be made of a material that is permeable to the fuel. In this way the diffusion rate is not affected by the material of the carrier part. The indicating unit is preferably removably mounted in the carrier part, which facilitates the analysis and replacement of the indicating unit.

The indicating unit of the indicator can also be integrated in a component in a fuel system intended for a combustion engine. In this way, space can be saved.

According to the invention, a plurality of sulphur content indicators or a cluster of sulphur content indicators can be arranged in the system. The indicators can be different and contain indicating units that have different fuel-absorbing capacities, and thus different exchange rates for the fuel. The number of indicators can vary, and can be between, for example, 2 and 20. In this way, analyses of the sulphur content in the fuel can be performed over an extended period of time.

The sulphur content indicator or the indicating unit itself can have a plurality of designs. The area of the surface that is in contact with the fuel can be decreased or increased by means of different designs, depending on how rapid an exchange rate for the fuel sample in the indicating unit is desired.

The sulphur content indicator or the indicating unit itself can be designed as a plate with the shape of a cuboid, a cube or a parallelepiped, or it can be essentially circular, for example, a circular plate. Such an indicating unit is simple to fabricate with low fabrication costs, and can thus be replaced as often as needed. The shape can also be adapted so that the indicating unit can be adapted so as to be a component in the fuel system. The sulphur content indicator or the indicating unit itself can also have an extended cylindrical shape. This shape enables the fuel to diffuse slowly toward the end of the indicating unit that is not in contact with the fuel. During the analysis, the indicating unit can then easily be sliced into a number of thin disks that are analyzed separately. If the diffusion rate of the material is known, it is also possible to estimate when a fuel with a given sulphur content has been filled.

The sulphur content indicator or the indicating unit itself can also have a spherical shape. The contact surface with the fuel can be increased by means of this design. The fuel will diffuse slowly toward the center of the sphere. If the diffusion rate for the material is known, this shape can also make it possible to estimate when a fuel with a given sulphur content has been filled. The surface layer of the sphere indicates the sulphur content of recently filled fuel.

The sulphur content indicator or the indicating unit can also be in the form of a granulate. In this way the surface area of the indicating unit can be increased, and it becomes possible to analyze the fuel over an extended period of time.

The invention also concerns a vehicle that comprises the above sulphur content indicator. According to one embodiment, the vehicle contains at least two sulphur content indicators, which sulphur content indicators have different fuel-absorbing capacities, whereupon an improved analysis result can be achieved.

The invention also concerns a method for indicating the sulphur content of a fuel intended for a combustion engine by means of the foregoing indicating unit. The method comprises the steps of allowing the fuel to diffuse into the indicating unit for a predetermined period of time, after which the indicating unit is removed from the surrounding fuel. To analyze the fuel, the fuel diffused into the indicating unit is extracted and analyzed.

The sulphur content in the fuel extracted from the indicating unit can be analyzed using standard methods such as are described in, for example, Swedish Standard SS-EN ISO 20884 (Petroleum products - Determination of sulphur content of automotive fuels - Wavelength- dispersive X-ray fluorescence spectometry (ISO 20884:2011) and/or Swedish Standard SS- EN ISO 20846 (Petroleum products - Determination of sulphur content of automotive fuels - Ultraviolet fluorescence method (ISO 20846:2011). The method can further comprise the step, prior to extraction, of dividing the indicating unit so that the sulphur content at a given distance from the surface can be analyzed. In this way it is possible to obtain an indication for recently filled fuel from the surface of the indicating unit. It is possible, in a corresponding manner, to obtain an indication of what was filled over an extended period of time from parts that are located a greater distance from the surface.

The method can further comprise a step of extracting the fuel by means of, e.g. heating the indicating unit the fuel diffused into the indicating unit [sic]. Extraction can also occur through the use of a suitable solvent, such as cyclohexane.

The invention will now be clarified with reference to the accompanying drawings.

Fig. 1 shows a schematic side view of a vehicle 1, which vehicle 1 is equipped with a combustion engine 2, which powers the drive wheels 4 of the vehicle via a gearbox 6 and a driveshaft 8. The combustion engine 2 is equipped with an exhaust system 10 in which an exhaust purification device 12 containing a catalytic converter is arranged. The combustion engine 2 is powered by fuel 14, which is supplied to the combustion engine 2 by means of a fuel system 16 comprising a fuel tank 18. A sulphur content indicator 100 according to the present invention is arranged in the fuel system 16, which sulphur content indicator 100 is intended to indicate the sulphur content of the fuel 14.

Fig. 2 shows a perspective view of a first embodiment of a sulphur content indicator 100 for fuel 14 according to the present invention. The sulphur content indicator 100 comprises an indicating unit 101, which is adapted so as to be arranged so that the indicating unit 101 is, by means of a surface 102, in contact with the fuel 14 for which the sulphur content is to be indicated. The indicating unit 101 has a shape that enables the fuel 14 to diffuse into the indicating unit 101 for a predetermined period of time, so that the sulphur content in the indicating 101 at a given distance from the surface 102 indicates the sulphur content of the fuel 14, which is detected during said period of time. The indicating unit 101 is passive, which means that it is not powered by electricity or any other driving force. According to the embodiment shown in Fig. 2, the indicating unit 101 is designed as a cuboid, but it can also be designed as a cube or parallelepiped, or as an essentially circular plate. The indicating unit 101 can, for example, be applied to the inside of a fuel tank 18 by means of attaching means or provided with a carrier part 104 that is removably mounted in the fuel tank 18, wherein the carrier part 104 is adapted so that the indicating unit 101 is in contact with the fuel 14 for which the sulphur content is to be indicated and which is contained in the tank 18.

The indicating unit 101 can be at least partly surrounded by a layer 106 that is permeable to the fuel 14 in order to influence the time during which the fuel 14 diffuses into the indicating unit 101. The layer 106 can, for example, consist of a perforated or non-perforated layer 106 of polymerized material that impedes diffusion of the fuel 14 and thereby reduces the rate at which the fuel 14 migrates into and out of the indicating unit 101. The fuel 14 thus passes through the layer 106 at a predetermined rate.

As noted above, the indicating unit 101 preferably has a shape that enables the fuel 14 to dif- fuse into the indicating unit 101 for a predetermined period of time, so that the sulphur content in the indicating unit 101 at a given distance from the surface 102 indicates the sulphur content of the fuel 14, which is detected during said period of time. Making the indicating unit 101 of a material that entails a predetermined diffusion rate for the fuel 14 into the indicating unit 101 makes it possible to influence and determine the predetermined period of time during which the fuel 14 diffuses into the indicating unit.101. Examples of materials for the indicating unit 101 consist of polymer materials, rubber and ceramics. Designing the indicating unit 101 with a given geometry also makes it possible to predetermine the period of time during which the fuel 14 will diffuse into the indicating unit 101 at a given distance from the surface 102. It is also possible to design the indicating unit 101 so that its entirety is exposed to the surrounding fuel 14, and thus will indicate that fuel 14 with a given sulphur content has been used during a given period of time.

The indicating unit 201 can be designed integrated in a component 208 in the fuel system 16. Fig. 3 shows how the indicating unit 201 according to a second embodiment of the invention is designed as a single component in the form of a sealing washer 208. Making the indicating unit 201 out of a sealing material such as a polymer or rubber makes it possible to arrange the indicating unit 201 sealingly between two fuel lines 210 in the fuel system, so that at least one surface 202 of the indicating unit 201 lies in contact with the fuel 14 for which the sulphur content is to be indicated. Fig. 4 shows a cross-sectional view of the sealing washer 208 arranged between two fuel lines 210 in the fuel system 16. The fuel 14 that flows in the fuel lines 210 passes through and comes into contact with a surface 202 of the sealing washer 208, whereupon fuel diffuses into the sealing washer 208. The sealing washer 208 can be provided with a circumferential carrier part 204 on its outer periphery, and with a layer 206 on its inner periphery.

Fig. 5 shows a third embodiment of the invention, in which the indicating unit 301 has an extended cylindrical shape. The indicating unit 301 is arranged in a carrier part 304 that at least partly surrounds the indicating unit 301. The carrier part 304 is preferably made of a material that is impermeable to the fuel 14. An end surface 302 of the cylindrical indicating unit 301 is in contact with the fuel 14 for which the sulphur content is to be indicated. The material in the indicating unit 301 will influence the time for the fuel 14 to diffuse into the indicating unit 301. As shown in Fig. 6, the end surface 302 of the cylindrical indicating unit 301 can be equipped with a layer 306 that is permeable to the fuel 14 in order to influence the time during which the fuel 14 diffuses into the indicating unit 301.

It is necessary to analyze the indicating unit 301 in order to determine the sulphur content of the fuel 14. This occurs appropriately after the indicating unit 301 has been removed from the fuel system 16. The indicating unit 301 can then be separated from the carrier part 304 and analyzed in order to thereby obtain an indication of whether the detected fuel 14 exhibits a sulphur content that is higher than the recommended level for the fuel 14. The indicating unit 301 is preferably removably arranged in the carrier part 304, which makes it possible to re- move the indicating unit 301 from the carrier part 304 in order to be analyzed. The cylindrical indicating unit 301 can be sliced up into thin disks, whereupon each disk is analyzed separately for its sulphur content. Knowing the time it takes for the fuel 14 to diffuse into the cylindrical indicating unit 301 provides an indication as to when the fuel 14 with a given sulphur content was filled.

Fig. 7 shows a fourth embodiment of the invention in which the indicating unit 401 has a spherical shape. The indicating unit 401 can be arranged directly on a holder 412 or in a carri- er part 404 that at least partly surrounds the indicating unit 401. According to this embodiment, the carrier part 404 is preferably made of a material that is permeable to the fuel 14, such as a perforated or reticulated sphere of plastic or metal. The material in the indicating unit 401 will influence the time for the fuel 14 to diffuse into the indicating unit 401. As an alternative or supplement to the carrier part 404 that is permeable to the fuel 14, the spherical indicating unit 401 can be equipped with a layer 406 that is permeable to the fuel 14 in order to influence the time that the fuel 14 diffuses into the indicating unit 401. Removing the indicating unit 401 from the carrier part 404 and analyzing the center of the spherical indicating unit 401 provides an indication of the average sulphur content of the fuel 14 to which the in- dicating unit 401 has been exposed. Analyzing the surface layer of the indicating unit 401 provides an indication of the sulphur content of the fuel 14 to which the indicating unit 401 has been exposed more recently.

Fig. 8 shows a fifth embodiment of the invention wherein the indicating unit 501 consists of a granulate, which is contained in a carrier part 504, which is made of a material that is permeable to the fuel 14. The carrier part 504 can be designed as a cube, a cuboid or a parallelepiped, or it can be cylindrical. A plurality of granular bodies 514 are disposed together in the carrier part 504, so that the carrier part 504 is completely filled with granulate. Each individual granular body 514 is thus undisplaceable relative to the others in the carrier part 504. Each granu- lar body 514 can be surrounding by a layer 506 such that sulphur impurities can pass through the layer 506 and into the granular body 514. The layer 506 can be designed as a membrane and adapted so as to allow sulphur impurities into the granular body 514, so that the fuel 14 passes through the membrane at a predetermined rate. The layer 506 can also result in the granular bodies 514 not being attracted or adhering to one another, or in abrasive erosion of the bodies 514 against one another under vibration being impeded.

During the analysis, the sulphur content in the granulate is obtained, and a determination is made as to whether the content exceeds the prescribed sulphur content for the fuel 14 that is used when operating the combustion engine 2.

After the indicating unit 101, 201, 301, 401, 501 has been removed and analyzed, a new indicating unit 101, 201, 301, 401, 501 can be mounted by means of the carrier part 104, 304, 404, 504 for renewed and continued indication of the sulphur content in the fuel 14 filled subsequently. The carrier part 104, 304, 404, 504 and the indicating unit 101, 201, 301, 401, 501 can be lead-sealed for the purpose of avoiding and/or detecting unauthorized removal and replacement of the indicating unit 101, 201, 301, 401, 501.

It is also possible to arrange the sulphur content indicator 100, 200, 300, 400, 500 with a carrier part in the form of a bottom plug for mounting in the fuel tank 18.

Fig. 9 shows a flow diagram of a method for indicating the sulphur content of a fuel 14 in- tended for a combustion engine 2 by means of an indicating unit 101, 201, 301, 401, 501 that is adapted so as to be arranged so that the indicating unit 101, 201, 301, 401, 501 is, by means of a surface 102, 202, 302, 402, 502, in contact with the fuel 14 for which the sulphur content is to be indicated. The method is characterized by the steps of:

a) allowing the fuel 14 to diffuse into the indicating unit 101, 201, 301, 401, 501 for a prede- termined period of time,

b) removing the indicating unit 101, 201, 301, 401, 501 from the surrounding fuel 14 after the predetermined period of time,

c) extracting the fuel 14 diffused into the indicating unit 101, 201, 301, 401, 501, and d) analyzing the sulphur content of the fuel 14 extracted from the indicating unit 101, 201, 301, 401, 501.

It is also possible, prior to step c), to perform the additional step of e) dividing the indicating unit 101, 201, 301, 401, 501 so that the sulphur content in the indicating unit 101, 201, 301, 401, 501 at a given distance from the surface 102, 202, 302, 402, 502 can be analyzed.

The fuel 14 diffused into the indicating unit 101, 201, 301, 401, 501 can be extracted by heating the indicating unit 101, 201, 301, 401, 501.

Example 1

20 round washers made of PEDM material and having a diameter of 13.2 mm and thickness of 2 mm were stamped. The washers were given ID numbers and weighed. The washers were then placed in hexadecane (Ci₆H₃₄) 99% for one week until the weight increase was below 1 mg/ 30 minutes. The hexadecane is kept at 40°C. Once the washers were fully swollen, nine washers were exposed to diesel containing 10% FAME, while one was a reference washer, which was not exposed to the diesel. The washers then taken out in accordance with a sched- ule, after which they were weighed and sliced into three parts for storage in sealed storage vials.

Table 1. Sample-collecting schedule for diffusion in rubber Once the exposure was completed for all washers, cyclohexane was added to the storage vials to extract the diesel present in the washers. For the extraction, cyclohexane was added in a ratio of 1: 10 between the weight of the absorbed diesel and the added cyclohexane. Each vial was exposed to 80 Hz ultrasound for one minute and shaken in a vortex at 2500 rpm for 30 seconds. Otherwise the vials were left to stand for ca. 48 hours.

After 48 hours the samples were analyzed using gas chromatography. The extracted sample was diluted 1:2 sample: (5% decane). Gas chromatography settings appropriate for diesel are used. The results of the analysis are shown in Fig. 10. The results are presented as a concentration over a period of time, i.e. the y-axis shows the concentration and the x-axis the time in hours. The samples showed that EPDM is not selective for the molecules in the diesel, and consequently serves as a material for the indicating unit. They also show that a near-equilibrium state was achieved after 4 hours, which indicates that the diffusion rate and thus the fuel- absorbing capacity are suitable for use in the indicating unit according to the invention.

The invention has been described above in connection with a combustion engine-powered vehicle, but it is apparent that the invention can advantageously be used in any application in which combustion engines are present, such as engines for wheeled vehicles or marine or in- dustrial use. The invention can similarly be used not only for diesel-powered engines but also for other types of engines and fuels where analogous needs exist. The invention has been described in connection with ensuring the function of an exhaust purification system for an engine, but naturally the invention can also be used wherever there is a need to indicate the sulphur content of a fuel some other purpose.

The described components and features as specified above can be combined between different described embodiments within the framework of the invention.

Claims

1. A sulphur content indicator for fuel intended for a combustion engine (2), comprising an indicating unit (101, 201, 301, 401, 501), which is adapted so as to be arranged so that the indicating unit (101, 201, 301, 401, 501) is, by means of a surface (102, 202, 302, 402, 502), in contact with the fuel (14) for which the sulphur content is to be indicated, characterized in that the indicating unit (101, 201, 301, 401, 501) is made of a material that has a predetermined fuel-absorbing capacity, and in that the indicating unit (101, 201, 301, 401, 501) has a shape that allows the fuel (14) to diffuse into the indicating unit (101, 201, 301, 401, 501) for a predetermined period of time so that the sulphur content of the fuel (14) in the indicating unit (101, 201, 301, 401, 501) at a given distance from the surface (102, 202, 302, 402, 502) indicates the sulphur content of the fuel (14), which is detected during said period of time.

2. An indicator according to claim 1, characterized in that the indicating unit (101) is de- signed as a plate with the shape of a cuboid, a cube, a parallelepiped or an essentially circular shape.

3. An indicator according to claim 1, characterized in that the indicating unit (301) has an extended cylindrical shape.

4. An indicator according to claim 1, characterized in that the indicating unit (401) has a spherical shape.

5. An indicator according to claim 1, characterized in that the indicating unit (501) is a granulate.

6. An indicator according to any of the preceding claims, characterized in that the indicating unit (101, 201, 301, 401, 501) is at least partly surrounded by a layer (106, 206, 306, 406, 506) that is permeable to the fuel 14.

7. An indicator according to claim 6, characterized in that the permeability of the layer (106, 206, 306, 406, 506) is adapted so that the fuel will pass through the layer at a predetermined rate.

8. An indicator according to any of the preceding claims, characterized in that the indicating unit (101, 201, 301, 401, 501) is arranged in a carrier part (104, 204, 304, 404, 504).

9. An indicator according to claim 8, characterized in that the carrier part (104, 204, 304, 404, 504) is arranged so as to partly surround the indicating unit (101, 201, 301, 401, 501).

10. An indicator according to either of claims 8 or 9, characterized in that the carrier part (104, 204, 304, 404, 504) is made of a material that is impermeable to the fuel (14).

11. An indicator according to any of claims 8 or 9, characterized in that the carrier part (104, 204, 304, 404, 504) is made of a material that is permeable to the fuel 14.

12. An indicator according to any of claims 8 to 11, characterized in that the indicating unit (101, 201, 301, 401, 501) is removably mounted in the carrier part (104, 204, 304, 404, 504).

13. An indicator according to any of the preceding claims, characterized in that the indicating unit (201) is integrated in a component (208) in a fuel system (16) intended for the combustion engine (2).

14. An indicator according to any of the preceding claims, characterized in that the indicat- ing unit (101, 201, 301, 401, 501) is made of a ceramic material, polymer material or fiber material.

15. A vehicle 1, characterized in that it comprises a sulphur content indicator (100, 200, 300, 400, 500) according to any of claims 1-14.

16. A vehicle 1 according to claim 15, characterized in that it comprises at least two sulphur content indicators (100, 200, 300, 400, 500), which have different fuel-absorbing capacities.

17. A method for indicating the sulphur content of a fuel (14) intended for a combustion engine (2) by means of an indicating unit (101, 201, 301, 401, 501) according to any of claims 1-13, characterized by the steps of:

a) allowing the fuel (14) to diffuse into the indicating unit (101, 201, 301, 401, 501) for a pre- determined period of time,

b) removing the indicating unit (101, 201, 301, 401, 501) from the surrounding fuel (14) after the predetermined period of time,

c) extracting the fuel (14) diffused into the indicating unit (101, 201, 301, 401, 501), and d) analyzing the sulphur content of the fuel (14) extracted from the indicating unit (101, 201, 301, 401, 501).

18. A method according to claim 17, characterized by the additional step of:

e) prior to step c), dividing the indicating unit (101, 201, 301, 401, 501) so that the sulphur content in the indicating unit (101, 201, 301, 401, 501) can be analyzed at a given distance from the surface (102, 202, 302, 402, 502).

19. A method according to claim 17 or 18, characterized in that the fuel (14) diffused into the indicating unit (101, 201, 301, 401, 501) is extracted by heating the indicating unit (101, 201, 301, 401, 501).