USE OF A PARAFFIN GAS OIL

Description

Field of the Invention

[0001] The present invention relates to the use of a paraffinic gasoil for providing certain benefits in an Exhaust Gas Recirculation (EGR) system in a compression ignition engine. In particular, the present invention relates to the use of a paraffinic gasoil for reducing the build up of deposits in an Exhaust Gas Recirculation system in a compression ignition engine.Background of the Invention

[0002] Exhaust Gas Recirculation (EGR) is a NOx emission control technique applicable to a wide range of diesel engines from light-, medium- and heavy-duty diesel engines systems right up to two-stroke low-speed marine engines. The configuration of an EGR system depends on the required EGR rate and other demands of the particular application. Most EGR systems include the following main hardware components: one or more EGR control valves, one or more EGR coolers, piping, flanges and gaskets.

[0003] It has been found that EGR systems have a tendency to become fouled by deposits that build up on the various EGR hardware components. This is a particular problem with high pressure EGR systems. Deposits forming in the system can cause increased NOx emissions and fuel consumption and can cause the system to fail by jamming the EGR valve in severe cases. Oxidation catalysts and / or particulate filters can be fitted before the EGR system to reduce hydrocarbons and particulates from the exhaust gas which cause EGR fouling, but this adds cost and complexity and therefore isn't widely employed by manufacturers. In the case of low pressure EGR, the DPF is situated between the engine and the low pressure EGR system, therefore deposits are not such a problem in these configurations. US2003233785A1 discloses a fuel for a compression ignition engine having a particulate emission index PEI of less than about 100, said fuel being characterized as: a) having a cetane number ranging from about 45 to about 65, and a T95 less than about 370[deg.] C; b) having a value of NR and AR, cetane number and T95 in [deg.] C according to the Formula: PEI ≤ 100 = 156 + Z 1 * Cetane # − 49 + Z 2 * NR − 14 + Z 3 * AR − 25 + Z 4 * T 95 − 35 deg . C.) Where: Z1 ranges from 0.67 to about 1.06, Z2 ranges from about 0.9 to about 1.28, Z3 ranges from about 2.54 to about 2.80, Z4 ranges from about 0.1 to about 0.4.

[0004] It would therefore be desirable to provide a fuel based solution that prevents the formation of deposits in the first instance, and is applicable to all EGR systems, irrespective of the equipment that the manufacturer has employed.

[0005] It has now been surprisingly found that by using a paraffinic gasoil in a diesel fuel composition, a surprising and hitherto unrecognised reduction in the build up of EGR deposits can be achieved.Summary of the Invention

[0006] According to the present invention there is provided the use of a paraffinic gasoil in a diesel fuel composition for reducing the build up of deposits in an Exhaust Gas Recirculation (EGR) system of a compression ignition internal combustion engine, wherein the paraffinic gasoil is a hydrotreated vegetable oil (HVO) derived gasoil and wherein the paraffinic gasoil comprises greater than 95 wt% paraffins, based on the total weight of the paraffinic gasoil.

[0007] According to another aspect of the present invention there is provided a method for reducing the build up of deposits in an Exhaust Gas Recirculation (EGR) system of a compression ignition internal combustion engine, which method comprises a step of introducing into said engine a diesel fuel composition which comprises a paraffinic gasoil, , wherein the paraffinic gasoil is a hydrotreated vegetable oil (HVO) derived gasoil and wherein the paraffinic gasoil comprises greater than 95 wt% paraffins, based on the total weight of the paraffinic gasoil.

[0008] It has been found that use of a paraffinic gasoil in a diesel fuel composition can provide reduced build up of deposits in the EGR system of a compression ignition internal combustion engine.

[0009] It has also been found that use of a paraffinic gasoil in a diesel fuel composition can prevent the formation of deposits in the EGR system in the first place and is applicable to all EGR systems, irrespective of the equipment that the manufacturer has employed.Brief Description of the Drawings

[0010] Figure 1 is a graphical representation of the results shown in Table 3 below.Detailed Description of the Invention

[0011] As used herein there is provided the use of a paraffinic gasoil in a diesel fuel composition for the purpose of reducing the build up of deposits in an EGR system of a compression ignition engine. In the context of this aspect of the invention, the term "reducing the build up of deposits" embraces any degree of reduction in the build up of deposits. The reduction in the build up of deposits may be of the order of 10% or more, preferably 20% or more, more preferably 50% or more, and especially 70% or more compared to the build up of deposits in an EGR system caused by an analogous fuel formulation which does not contain a paraffinic gasoil. As used herein, the term "reducing the build up" also encompasses the prevention of EGR deposit formation in the first place.

[0012] It has been found that the present invention is particularly useful in the case of high pressure EGR systems because these systems are more susceptible to deposit build up than low pressure EGR systems.

[0013] It is also envisaged that the present invention may be used for the purpose of clean up of existing EGR deposits formed with conventional diesel fuel.

[0014] A first essential component herein is a paraffinic gasoil. The paraffinic gasoil is a hydrotreated vegetable oil (HVO) derived gasoil and comprises greater than 95 wt% paraffins, based on the total weight of the paraffinic gasoil.

[0015] The paraffinic gasoil fuel is preferably present in the diesel fuel composition herein at a level in the range from 20% v / v to 100% m / m, preferably from 50% v / v to 100% v / v, more preferably from 80% v / v to 100%v / v, even more preferably from 90% v / v to 100% v / v, based on the total diesel fuel composition.

[0016] A paraffinic gasoil can be derived from any suitable source as long as it is suitable for use in a diesel fuel composition.

[0017] Paraffinic gasoils include, for example, Fischer-Tropsch derived gasoils, and gasoils derived from hydrogenated vegetable oil (HVO), and mixtures thereof.

[0018] From the viewpoint of preventing and reducing EGR deposits, while ensuring other properties such as viscosity, density and distillation properties stay within the requirements of diesel specifications, the paraffinic gasoil is preferably a Fischer-Tropsch derived gasoil fuel. The paraffinic nature of Fischer-Tropsch derived gasoil means that diesel fuel compositions containing it will have high cetane numbers compared to conventional diesel.

[0019] Fischer-Tropsch derived gasoil is not according the present invention, the term "paraffinic gasoil" as used herein includes those paraffinic gasoils derived from the hydrotreating of vegetable oils (HVO). The HVO process is based on an oil refining technology. In the process, hydrogen is used to remove oxygen from the triglyceride vegetable oil molecules and to split the triglyceride into three separate chains thus creating paraffinic hydrocarbons.

[0020] In accordance with the presence invention, the paraffinic gasoil for use herein, (i.e. the hydrogenated vegetable oil derived gasoil) consists of at least 95% w / w, more preferably at least 98% w / w, even more preferably at least 99.5% w / w, and most preferably up to 100% w / w of paraffinic components, preferably iso- and normal paraffins.

[0021] By "Fischer-Tropsch derived" is meant that a fuel or base oil is, or derives from, a synthesis product of a Fischer-Tropsch condensation process. The term "non-Fischer-Tropsch derived" may be interpreted accordingly. A Fischer-Tropsch derived fuel may also be referred to as a GTL (gas-to-liquid) fuel.

[0022] The diesel fuel compositions described herein of the present invention are particularly suitable for use as a diesel fuel, and can be used for arctic applications, as winter grade diesel fuel due to the excellent cold flow properties.

[0023] For example, a cloud point of -10°C or lower (EN 23015) or a cold filter plugging point (CFPP) of -20°C or lower (as measured by EN 116) may be possible with fuel compositions herein.

[0024] The diesel fuel compositions described herein may comprise a diesel base fuel in addition to a paraffinic gasoil.

[0025] The diesel base fuel may be any petroleum derived diesel suitable for use in an internal combustion engine, such as a petroleum derived low sulphur diesel comprising <50 ppm of sulphur, for example, an ultra low sulphur diesel (ULSD) or a zero sulphur diesel (ZSD). Preferably, the low sulphur diesel comprises <10 ppm of sulphur.

[0026] The petroleum derived low sulphur diesel preferred for use in the present invention will typically have a density from 0.81 to 0.865, preferably 0.82 to 0.85, more preferably 0.825 to 0.845 g / cm 3< at 15°C; a cetane number (ASTM D613) at least 51; and a kinematic viscosity (ASTM D445) from 1.5 to 4.5, preferably 2.0 to 4.0, more preferably from 2.2 to 3.7 mm 2< / s at 40°C.

[0027] In one embodiment, the diesel base fuel is a conventional petroleum-derived diesel.

[0028] Generally speaking, in the context of the present invention the fuel composition may be additivated with fuel additives. Unless otherwise stated, the (active matter) concentration of each such additive in a fuel composition is preferably up to 10000 ppmw, more preferably in the range from 5 to 1000 ppmw, advantageously from 75 to 300 ppmw, such as from 95 to 150 ppmw. Such additives may be added at various stages during the production of a fuel composition; those added to a base fuel at the refinery for example might be selected from anti-static agents, pipeline drag reducers, middle distillate flow improvers (MDFI) (e.g., ethylene / vinyl acetate copolymers or acrylate / maleic anhydride copolymers), lubricity enhancers, anti-oxidants and wax anti-settling agents.

[0029] The fuel composition may include a detergent, by which is meant an agent (suitably a surfactant) which can act to remove, and / or to prevent the build-up of, combustion related deposits within an engine, in particular in the fuel injection system such as in the injector nozzles. Such materials are sometimes referred to as dispersant additives. Where the fuel composition includes a detergent, preferred concentrations are in the range 20 to 500 ppmw active matter detergent based on the overall fuel composition, more preferably 40 to 500 ppmw, most preferably 40 to 300 ppmw or 100 to 300 ppmw or 150 to 300 ppmw. Detergent-containing diesel fuel additives are known and commercially available. Examples of suitable detergent additives include polyolefin substituted succinimides or succinamides of polyamines, for instance polyisobutylene succinimides or polyisobutylene amine succinamides, aliphatic amines, Mannich bases or amines and polyolefin (e.g. polyisobutylene) maleic anhydrides. Particularly preferred are polyolefin substituted succinimides such as polyisobutylene succinimides.

[0030] Other components which may be incorporated as fuel additives, for instance in combination with a detergent, include lubricity enhancers; dehazers, e.g. alkoxylated phenol formaldehyde polymers; anti-foaming agents (e.g. commercially available polyether-modified polysiloxanes); ignition improvers (cetane improvers) (e.g. 2-ethylhexyl nitrate (EHN), cyclohexyl nitrate, di-tert-butyl peroxide and those disclosed in US4208190 at column 2, line 27 to column 3, line 21); anti-rust agents (e.g. a propane-1,2-diol semi-ester of tetrapropenyl succinic acid, or polyhydric alcohol esters of a succinic acid derivative, the succinic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group containing from 20 to 500 carbon atoms, e.g. the pentaerythritol diester of polyisobutylene-substituted succinic acid); corrosion inhibitors; reodorants; anti-wear additives; anti-oxidants (e.g. phenolics such as 2,6-di-tert-butylphenol, or phenylenediamines such as N,N'-di-sec-butyl-p-phenylenediamine); metal deactivators; static dissipator additives; and mixtures thereof.

[0031] It is preferred that the additive contain an anti-foaming agent, more preferably in combination with an anti-rust agent and / or a corrosion inhibitor and / or a lubricity additive.

[0032] It is particularly preferred that a lubricity enhancer be included in the fuel composition, especially when it has a low (e.g. 500 ppmw or less) sulfur content. The lubricity enhancer is conveniently present at a concentration from 50 to 1000 ppmw, preferably from 100 to 1000 ppmw, based on the overall fuel composition.

[0033] The (active matter) concentration of any dehazer in the fuel composition will preferably be in the range from 1 to 20 ppmw, more preferably from 1 to 15 ppmw, still more preferably from 1 to 10 ppmw and advantageously from 1 to 5 ppmw. The (active matter) concentration of any ignition improver present will preferably be 600 ppmw or less, more preferably 500 ppmw or less, conveniently from 300 to 500 ppmw.

[0034] The present invention may in particular be applicable where the fuel composition is used or intended to be used in a direct injection diesel engine, for example of the rotary pump, in-line pump, unit pump, electronic unit injector or common rail type, or in an indirect injection diesel engine. The fuel composition may be suitable for use in heavy-and / or light-duty diesel engines, and in engines designed for on-road use or off-road use.

[0035] In order to be suitable for at least the above uses, the diesel fuel composition of the present invention preferably has one or more of the following characteristics: a kinematic viscosity at 40°C of 1.9 mm 2< / s or greater, more preferably in the range from 1.9 to 4.5 mm 2< / s; a density of 800 kg / m 3< or greater, more preferably in the range from 800 to 860, even more preferably 800 to 845 kg / m 3< ; a T95 of 360°C or less; a cloud point in the range from 0°C to -13°C, more preferably from -5°C to -8°C; a CFPP in the range of from -8°C to -30°C, more preferably from -15°C to -20°C.

[0036] The invention is illustrated by the following nonlimiting examples.Examples

[0037] Two different fuels were used in the examples herein. One fuel was a GTL gasoil containing 10 ppm of a hindered phenol antioxidant (2,6-di-tert-butyl-4-methylphenol otherwise known as BHT).

[0038] Table 1 shows the physical and compositional characteristics of the GTL gasoil used in the examples herein. The GTL gasoil was obtained from Pearl GTL, Ras Laffan and is commercially available from the Shell / Royal Dutch Group of Companies. The second fuel was a conventional diesel fuel (Diesel B7). The physical characteristics of the conventional diesel fuel (Diesel B7) used in the examples is shown in Table 2. As used herein "Diesel B7" means diesel base fuel containing 7% biofuel components. Table 1Test ParameterTest MethodUnitsVisual AppearanceVisualClear and brightDensity at 15°CDIN EN ISO 12185kg / m 3< 777.9DistillationDIN EN ISO 3405IBPDIN EN ISO 3405°C179.65% v / vDIN EN ISO 3405°C204.910% v / vDIN EN ISO 3405°C213.520% v / vDIN EN ISO 3405°C231.030% v / vDIN EN ISO 3405°C248.740% v / vDIN EN ISO 3405°C263.550% v / vDIN EN ISO 3405°C275.660% v / vDIN EN ISO 3405°C287.470% v / vDIN EN ISO 3405°C299.580% v / vDIN EN ISO 3405°C312.690% v / vDIN EN ISO 3405°C327.695% v / vDIN EN ISO 3405°C337.7FBPDIN EN ISO 3405°C344.2Residue & LossDIN EN ISO 3405%vol2.0E250DIN EN ISO 3405%vol31.4E300DIN EN ISO 3405%vol71.0Kinematic Viscosity at 40°CDIN EN ISO 3104mm 2< / s2.6881FlashpointDIN EN ISO 2719°C74.3SDIN EN ISO 20884mg / kg<5 Table 2 Test parameterTest MethodUnitLimitResultMinMaxAppearanceVisualReportC&BCetane NumberEN ISO 516551.054.052.2Cetane IndexEN ISO 426446.0-49.8Density @ 15°CEN ISO 12185Kg / L0.83500.84500.8364Cloud PointEN ISO 23015°C--10-11CFPPEN 116°C--25-30Carbon Residue (10% Dis. Res.)EN ISO 10370% m / m-0.30<0.01Flash PointEN ISO 2719°C55.0-72.0Lubricity, wear scar diameter @ 60°CEN ISO 12156-1µm-460190SulfurEN ISO 20846mg / kg5.09.06.1Viscosity @ 40°CEN ISO 3104mm 2< / s2.0004.5002.459Water ContentEN ISO 12937mg / kg-20060FAME ContentEN 14078%v / v6.07.06.6Mono Aromatics ContentIP 391 mod%m / mReport21.7Polycyclic Aromatics ContentIP 391 mod%m / m-8.03.3Total AromaticsIP 391 mod%m / m25.029.025.0Oxidation StabilityEN 15751H20.0->20.0Oxidation Stability (16h)EN ISO 12205g / m3-252Ash ContentEN ISO 6245%m / m-0.010<0.001Copper Corrosion (3h at 50°C)EN ISO 2160RatingReport1ATotal ContaminationEN 12662Mg / kg-248CarbonASTM D3343 mod%m / mReport86.00HydrogenASTM D3343 mod%m / mReport13.34OxygenEN 14078%m / mReport0.66Gross Calorific ValueASTM D3338 modMJ / kgReport45.61Net Calorific ValueASTM D3338MJ / kgReport42.78Distillation (Evaporated)E250EN ISO 3405%v / v-65.046.3E350EN ISO 3405%v / v85.0-98.0E370EN ISO 3405%v / vReport98.0IBPEN ISO 3405°CReport174.695%vEN ISO 3405°C-360.0343.1FBPEN ISO 3405°CReport349.4 Test Method

[0039] The engine used in the examples was a standard PSA DV6 1.6L Euro 5 engine. A clean EGR system was weighed, then fitted to the engine.

[0040] The test was run for 24 hours continuously, at 2500 rpm and 5kW (19Nm) test condition. The engine coolant temperature was controlled to 37°C for the entire test duration. When the test was completed, the engine was dismantled, and all EGR components weighed. All EGR components were then photographed, before the entire EGR system was cleaned using solvents and a sonic bath, to remove the deposits. The clean EGR system was then reweighed before being fitted to the engine to run the next test. The tests toggled between B7 and GTL fuel. Two tests were run on each fuel.

[0041] The results of these experiments are shown in Table 3 below. Table 3Mass of deposit gEGR intake plastic pipeEGR outlet pipeEGR valveEGR coolerEGR housingTotalB7 Test 10.350.580.187.32.2110.62GTL Test 20.370.20.151.570.622.91B7 Test 30.280.980.237.22.18010.87GTL Test 40.430.290.151.630.583.08

[0042] Figure 1 is a graph of the Results set out in Table 3.Discussion

[0043] As can be seen from the results in Table 3 and the graph in Figure 1, there is a significant reduction in the amount of deposits formed on the EGR components in the case of the GTL fuel compared with the conventional diesel B7 fuel.

Claims

1. Use of a paraffinic gasoil in a diesel fuel composition for reducing the build up of deposits in an Exhaust Gas Recirculation (EGR) system of a compression ignition internal combustion engine, wherein the paraffinic gasoil is a hydrotreated vegetable oil (HVO) derived gasoil and wherein the paraffinic gasoil comprises greater than 95 wt% paraffins, based on the total weight of the paraffinic gasoil.

2. Use according to Claim 1 wherein the paraffinic gasoil comprises greater than 98 wt% paraffins, based on the total weight of the paraffinic gasoil.

3. Use according to Claim 1 or 2 wherein the paraffinic gasoil comprises at least 99.5% w / w of paraffinic components, preferably iso- and normal paraffins.

4. Use according to any of Claims 1 to 3 wherein the paraffinic gas oil is present at a level of from 20 %v / v to 100 %v / v, based on the total diesel fuel composition.

5. Use according to any of Claims 1 to 4 wherein the paraffinic gas oil is present at a level of from 50 %v / v to 100 %v / v, based on the total diesel fuel composition.

6. Use according to any of Claims 1 to 5 wherein the paraffinic gas oil is present at a level from 80% v / v to 100% v / v, based on the total diesel fuel composition.

7. Use according to any of Claims 1 to 6 wherein the diesel fuel composition additionally comprises a diesel base fuel.

8. Method for reducing the build up of deposits in an Exhaust Gas Recirculation (EGR) system of a compression ignition internal combustion engine, which method comprises a step of introducing into said engine a diesel fuel composition which comprises a paraffinic gasoil, wherein the paraffinic gasoil is a hydrotreated vegetable oil (HVO) derived gasoil and wherein the paraffinic gasoil comprises greater than 95wt% paraffins, based on the total weight of the paraffinic gasoil.