Use of a renewable fuel composition for pilot injection in a dual-fuel engine

Abstract

The present invention relates to the use, for pilot injection in a dual-fuel engine, of a fuel composition comprising: a) at least 30% by mass of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and derived from a process for hydrotreating fatty acids and / or fatty acid esters, from a Fischer-Tropsch process or from a process for producing fuel bases from alcohols; and b) at least one base consisting of one or more esters selected from methyl esters and ethyl esters of fatty acids. The present invention also relates to a method for operating a dual-fuel engine and to a novel fuel composition.

Description

[0001] DESCRIPTION

[0002] TITLE: Use of a renewable fuel composition for pilot injection in a mixed fuel engine

[0003] The present invention relates to the use of a fuel composition comprising the combination of at least two bases, including at least one paraffinic base (a) derived from a process for hydrotreating fatty acids and / or fatty acid esters, from a Fischer-Tropsch process or from a process for producing fuel bases from alcohols and at least one base (b) consisting of methyl and / or ethyl esters of fatty acids, for pilot injection in a mixed-fuel engine.

[0004] The present application also describes a particular fuel composition, comprising the combination of these two types of bases in specific proportions.

[0005] STATE OF THE PRIOR ART

[0006] In order to reduce greenhouse gas emissions generated by the combustion of traditional fossil-based hydrocarbon fuels, the use of mixed fuel engines (also known as "dual fuel" engines) has grown, particularly in certain sectors such as maritime transport. Mixed fuel engines have the particularity of being powered by two fuels, including a main fuel and a pilot fuel, i.e. intended for pilot injection.

[0007] It is particularly beneficial to be able to use as the main fuel light fuels such as ammonia, methanol and liquefied natural gas, the combustion of which generates much lower emissions of carbon dioxide (CO2), sulfur gases (SOx), unburned hydrocarbons and particulate matter than the combustion of heavier fuels such as diesel and heavy fuel oils.

[0008] However, as things stand, these engines cannot operate properly if powered by these fuels alone. They require the injection of a smaller quantity of a second fuel to initiate combustion by self-ignition in a mixture with air. This injection is called pilot injection. The main fuel is also injected in a mixture with air, to fuel combustion once it has started.

[0009] In the prior art, pilot injection of mixed fuel engines is typically carried out using traditional fuels of fossil origin such as diesel fuels. In the case of a marine engine, the supply of mixed fuel engines is for example carried out using the following pilot fuel / main fuel combinations:

[0010] - marine diesel or MGO (from the English “Marine GasOil”) / natural gas;

[0011] - MGO / methanol;

[0012] - MGO / ammonia.

[0013] The use of these fossil fuels for pilot injection reduces the environmental benefit and the emission savings provided by the mixed fuel engine.

[0014] Furthermore, for environmental reasons and / or resource availability, regulations in many countries encourage the introduction of increasing quantities of renewable bases into fuels, particularly those of biological origin.

[0015] SUBJECT OF THE INVENTION

[0016] Continuing its research into the development of new decarbonized fuels with reduced environmental impact, usable in particular in mixed fuel engines, the Applicant has now discovered that the use as pilot fuel of a composition comprising at least two types of specific bases, in particular of biological origin, provides unexpected advantages.

[0017] The present invention thus relates to the use, for pilot injection in a mixed-fuel engine, of a fuel composition comprising: a) at least 30% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and resulting from a process for hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols; and b) at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0018] The use of such a fuel for pilot injection of a mixed fuel engine has proven to be more efficient than that of a traditional fuel such as fossil diesel. In particular, it allows, for identical combustion performance, to reduce the pilot injection quantity, i.e. the quantity of fuel to be injected to initiate combustion in the mixed fuel engine.

[0019] Compared to the use of a traditional pilot fuel, and moreover by the use of a reduced quantity of pilot injection, the invention further makes it possible to reduce undesirable emissions such as emissions of carbon dioxide, nitrogen oxides, sulfur gases, unburned hydrocarbons and particles.

[0020] The environmental benefit of the mixed fuel engine is thus improved, even more so when this engine is powered by a main fuel based on ammonia, methanol or liquefied natural gas.

[0021] The invention thus makes it possible to reduce the total energy balance of the engine, from well-to-wake, assessed by life cycle analysis.

[0022] The present invention also relates to a method of operating a mixed fuel engine, in which this fuel composition is injected to initiate combustion.

[0023] The present invention implements a particular fuel composition, which is suitable for pilot injection in a mixed-fuel engine.

[0024] This composition preferably comprises: a) at least 30% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and resulting from a process for hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols; and b) at least 15% by mass, relative to the total mass of the composition, of at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0025] The bases (a) and (b) used are renewable bases which can advantageously be derived from biological matter.

[0026] Thus, the composition according to the invention comprises a significant quantity of bio-sourced materials. It therefore has a high eco-material content. The mass content of eco-material in the composition is defined by the following equation:

[0027] Eco-material content in % = 100 - (percentage of non-biosourced, non-biodegradable, non-recycled materials).

[0028] According to an advantageous embodiment, the composition has an eco-material content of at least 50% by mass, preferably at least 60% by mass, more preferably at least 70% by mass, relative to the total mass of the composition.

[0029] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the description and examples which follow.

[0030] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, notably in the expressions "between" and "ranging from ... to ..."

[0031] Furthermore, the expressions "at least one" and "at least" used in this description are respectively equivalent to the expressions "one or more" and "greater than or equal to".

[0032] Finally, in a manner known per se, the term CN compound or group refers to a compound or group containing N carbon atoms in its chemical structure.

[0033] DETAILED DESCRIPTION

[0034] The paraffinic hydrocarbon base (a) The fuel composition comprises at least 30% by mass, relative to the total mass of the composition, of one or more paraffinic hydrocarbon bases which are characterized in that:

[0035] - they comprise at least 90% by mass of paraffins relative to the mass of said base; and

[0036] - they are produced from a process of hydrotreatment of fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process of production of fuel bases from alcohols.

[0037] The paraffinic base(s) used in the invention are advantageously derived from the transformation of raw materials of non-petroleum origin (i.e. non-fossil), and in particular biological raw materials.

[0038] According to a first embodiment, the composition comprises at least one base a) resulting from a process for hydrotreatment of fatty acids and / or fatty acid esters.

[0039] In this embodiment, the base a) consists of hydrogenated fatty acids and / or hydrogenated fatty acid esters, also called “HEFA” base.

[0040] As is well known, the term HEFA (from the English Hydrogenated Esters and Fatty Acids) refers to a base obtained by hydrogenation of fatty acids and / or fatty acid esters. The corresponding hydrogenation processes are well known and allow fatty acids and fatty acid esters to be transformed into paraffins. HEFA bases are thus essentially made up of linear and branched paraffins (alkanes).

[0041] Fatty acids and fatty acid esters can come from many sources, including vegetable oils and fats, animal oils and fats, and recycled oils (e.g., edible oils, cooking oils).

[0042] The paraffinic hydrocarbon base(s) (a) may advantageously consist of hydrotreated vegetable oils, also known as HVO (from the English “hydrotreated vegetable oils”). These are oils of vegetable origin which have undergone successive treatments including hydrotreatment and possible isomerization. The processes for preparing such hydrotreated vegetable oils are also known per se.

[0043] The HEFA-type bases (a) may in particular be produced from oil(s) of natural origin by a process comprising a hydrogenation and deoxygenation treatment of fatty acid esters and free fatty acids and a further treatment of the product comprising hydrocracking, or hydroisomerization, or isomerization, or a combination of these steps, and which may include other conventional refining processes. In other words, the renewable paraffinic synthetic HEFA base is produced from the hydrotreatment of esters and fatty acids contained in an oil of natural origin.

[0044] An oil of natural origin is defined as an oil of biomass origin and containing no mineral oil. In the present description, the expression "oil(s) of natural origin" refers indifferently to oils, fats and their mixtures. Said oil(s) of natural origin may contain one or more oils chosen from vegetable oils, animal fats, preferably non-edible highly saturated oils, used oils, by-products of the refining of vegetable oil(s) or animal oil(s) containing free fatty acids, tall oils and oils produced by bacteria, yeasts, algae, prokaryotes or eukaryotes.Suitable vegetable oils include palm oil, palm kernel oil, soybean oil, rapeseed oil (colza or canola), sunflower oil, linseed oil, bran oil, rice oil, corn oil, olive oil, castor oil, sesame oil, pine oil, peanut oil, mustard oil, carinata oil, hemp oil, coconut oil, babasu oil, cottonseed oil, linola oil, j atropha oil. Animal fats include tallow, lard, fat (yellow and brown fat), fish oil / fat, butterfat, milk fats.

[0045] By-products of vegetable or animal oil refining are by-products containing free fatty acids that are removed from crude fats and oils by neutralization or distillation under vacuum or steam. A typical example is known as PFAD (Palm Fatty Acid Distillate). Waste oils include used cooking oils (used edible oils) and oils recovered from wastewater, such as grease / drainage oils, gutter oils, sewage oils, e.g., from water treatment plants, and waste fats from the food industry. Tall oils, including crude tall oils, distilled tall oils (DTOs) and tall oil fatty acids (TOFAs), preferably DTO and TOFA, may also be used in the present invention.Tall oil, or otherwise known as tallol, is a liquid by-product of the Kraft wood processing process, used to isolate wood pulp useful for the paper industry. Tall oil is essentially obtained when conifers are used in the Kraft process. After treating the wood chips with sodium sulfide in aqueous solution, the isolated tall oil is alkaline. The latter is then acidified with sulfuric acid to produce crude tall oil. The oil(s) of natural origin used in the present invention also include oils produced by microorganisms, either natural microorganisms or genetically modified microorganisms, such as bacteria, yeasts, algae, prokaryotes or eukaryotes. In particular, such oils can be recovered by well-known mechanical or chemical extraction methods.

[0046] According to a second embodiment, the composition comprises at least one base a) resulting from a Fischer-Tropsch process, which is a well-known process for synthesizing hydrocarbons from synthesis gas containing carbon monoxide (CO) and hydrogen (H2).

[0047] In this embodiment, the base a) is advantageously produced from solid biomass. The thermochemical conversion of biomass (gasification and Fisher-Tropsch synthesis), also called BtL (Biomass to Liquid), comprises the following steps: conditioning of the biomass (preparation, crushing, roasting), gasification of the biomass (obtaining a synthesis gas), purification of the synthesis gas, Fisher-Tropsch synthesis to transform the gas into synthetic biofuel.

[0048] According to a third embodiment, the composition comprises at least one base a) resulting from a process for producing fuel bases from alcohols. Such a process is also well known.

[0049] The starting alcohol(s) may be chosen from monoalcohols containing from 1 to 6 carbon atoms.

[0050] The production process includes a step of dehydration of the alcohol(s) to produce the corresponding olefins, then a step of oligomerization of the olefins to obtain unsaturated hydrocarbons, and finally a step of hydrogenation of the unsaturated hydrocarbons to produce the paraffinic base.

[0051] The first embodiment is preferred.

[0052] Whatever the embodiment, the paraffinic hydrocarbon base (a) may also have undergone an isomerization step and / or a distillation step before its incorporation into the composition according to the invention.

[0053] Generally, the paraffinic hydrocarbon base(s) (a) have a distillation range at atmospheric pressure advantageously in the range from 100 to 400°C, preferably from 130 to 390°C.

[0054] The distillation range of said paraffinic hydrocarbon base is determined in accordance with ASTM D86 or ASTM D7169.

[0055] The paraffinic hydrocarbon base(s) (a) have a paraffin content greater than or equal to 90% by mass, preferably greater than or equal to 95% by mass, and better still greater than or equal to 96% by mass, relative to the total mass of the base(s) (a).

[0056] The term "paraffins" refers, in a manner known per se, to branched alkanes (also called iso-paraffins or iso-alkanes) and unbranched alkanes (also called n-paraffins or n-alkanes).

[0057] The paraffins present in the paraffinic hydrocarbon base(s) advantageously comprise from 10 to 20 carbon atoms. Preferably, they consist of at least 60% by mass, more preferably at least 80% by mass and better still at least 85% by mass of paraffins comprising from 12 to 18 carbon atoms, preferably from 14 to 18 carbon atoms, and even more preferably from 15 to 18 carbon atoms.

[0058] According to a preferred embodiment, the paraffinic hydrocarbon base(s) (a) contain at least 60% by mass of iso-paraffins, preferably at least 70% by mass of iso-paraffins, relative to the total mass of the base(s) (a). According to a particularly preferred embodiment, they contain at least 80% by mass of iso-paraffins, relative to the total mass of the base(s) (a).

[0059] The paraffinic hydrocarbon base(s) (a) have an aromatic compound content preferably less than or equal to 10,000 ppm by mass, more preferably less than or equal to 1,500 ppm by mass, even more preferably less than or equal to 1,000 ppm by mass.

[0060] Their content of naphthenic compounds (cycloparaffins or cycloalkanes) is advantageously less than or equal to 100,000 ppm by mass (10% by mass), preferably less than or equal to 40,000 ppm by mass (4% by mass), more preferably less than or equal to 30,000 ppm by mass (3% by mass), better still less than or equal to 20,000 ppm by mass (2% by mass), and better still less than or equal to 10,000 ppm by mass (1% by mass).

[0061] Their sulfur content is advantageously less than or equal to 10 ppm by mass, preferably less than or equal to 5 ppm by mass. In a particularly preferred manner, the paraffinic hydrocarbon base(s) (a) are completely free of sulfur.

[0062] The composition according to the invention preferably comprises at least 40% by mass, and more preferably at least 50% by mass, relative to the total mass of the composition, of one or more paraffinic hydrocarbon bases (a) as described above.

[0063] Said composition preferably comprises the base(s) (a) in a content within the range of 30 to 85% by mass, preferably 30 to 80% by mass, more preferably 40 to 70% by mass, better still 40 to 60% by mass, and better still 50 to 60% by mass, relative to the total mass of the composition.

[0064] Methyl and ethyl esters of fatty acids (b)

[0065] The composition used in the invention comprises one or more bases consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0066] By fatty acid is meant a carboxylic acid comprising a saturated or unsaturated hydrocarbon chain having from 6 to 30 carbon atoms, preferably from 7 to 24 carbon atoms, and more preferably from 8 to 20 carbon atoms.

[0067] The esters present in the base(s) (b) are therefore chosen from esters of ethyl alcohol or methyl alcohol and one or more fatty acids as defined above.

[0068] These esters are products known per se. They can be advantageously obtained by reacting at least one oil chosen from vegetable oils, animal oils and used oils with methanol or ethanol, so as to obtain the corresponding esters by a chemical process called transesterification.

[0069] When the alcohol is methanol, we obtain a mixture of fatty acid methyl esters also called EMAG.

[0070] When the alcohol is ethanol, we obtain a mixture of fatty acid ethyl esters also called EEAG.

[0071] According to a preferred embodiment, the ester(s) are chosen from fatty acid methyl esters. Preferably, the composition according to the invention comprises at least one base (b) consisting of a mixture of fatty acid methyl esters (FAME).

[0072] The composition used in the context of the invention advantageously comprises the base(s) (b) in a content within the range of 15 to 70% by mass, relative to the total mass of the composition.

[0073] Said composition preferably comprises the base(s) (b) in a content in the range from 20 to 70% by mass, preferably from 30 to 60% by mass, better still from 40 to 60% by mass, and better still from 50 to 60% by mass, relative to the total mass of the composition.

[0074] According to a preferred embodiment, the composition comprises at least one base (b) consisting of a mixture of fatty acid methyl esters (FAME) in a content ranging from 15 to 70% by mass, preferably from 20 to 70% by mass, preferably from 30 to 60% by mass, better still from 40 to 60% by mass, and better still from 50 to 60% by mass, relative to the total mass of the composition.

[0075] Fuel composition

[0076] The composition used in the present invention may further comprise one or more additional bases, different from the paraffinic hydrocarbon bases a) and the bases b) consisting of methyl esters and / or ethyl esters of fatty acids described above.

[0077] These additional bases may consist of any liquid hydrocarbon fractions from one or more sources chosen from mineral, animal, vegetable and synthetic sources.

[0078] The fuel composition may thus further comprise at least one additional base consisting of a cut of liquid hydrocarbons of petroleum origin, chosen from middle distillates whose distillation interval at atmospheric pressure is in the range from 100 to 500°C, preferably from 120 to 450°C, preferably from 190 to 400°C, preferably from 210 to 350°C, more preferably from 220 to 330°C. In a manner known per se, the distillation intervals are expressed with reference to the ADTM D86 standard or to the ASTM D7169 standard.

[0079] These middle distillates may, for example, be chosen from distillates obtained by direct distillation of crude oils, vacuum distillates, hydrotreated distillates, distillates resulting from catalytic cracking and / or hydrocracking of vacuum distillates, distillates resulting from ARDS type conversion processes (by atmospheric residue desulfurization). The fuel composition may thus comprise at least one fuel base of petroleum origin (i.e. of fossil origin) chosen from diesel oils, domestic fuel oils (DFO) and heavy fuel oils, preferably diesel oils.

[0080] Diesel fuel bases can include any commercially available diesel engine fuel compositions. Representative examples include diesel fuels meeting the NF EN 590 standard or marine distillates meeting the ISO 8217 standard.

[0081] According to a first preferred embodiment, the composition comprises at least one additional base consisting of a cut of liquid hydrocarbons of petroleum origin chosen from middle distillates as described above, more preferably at least one fuel base of petroleum origin chosen from diesel fuels.

[0082] In this embodiment, said additional base preferably represents from 5 to 50% by mass, more preferably from 10 to 40% by mass, and even more preferably from 20 to 30% by mass, relative to the total mass of the composition.

[0083] More preferably, the composition comprises at least one fuel base of petroleum origin chosen from diesel fuels in a content ranging from 5 to 50% by mass, more preferably from 10 to 40% by mass, and even more preferably from 20 to 30% by mass, relative to the total mass of the composition.

[0084] According to a second embodiment, the composition used in the present invention does not comprise additional bases as described above, different from the paraffinic bases a) and the bases b) consisting of methyl esters and / or ethyl esters of fatty acids.

[0085] Thus in this second embodiment, the composition comprises as sole bases the base(s) a) of paraffinic hydrocarbons in a minimum content of at least 30% by mass and the base(s) b) consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0086] In this embodiment, the composition preferably comprises: a) from 30% to 70% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base as described above; and b) from 30% to 70% by mass, relative to the total mass of the composition, of at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0087] More preferably, the composition comprises: a) from 40% to 60% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base as described above; and b) from 40% to 60% by mass, relative to the total mass of the composition, of at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0088] Optional additives

[0089] The composition according to the invention may further comprise one or more additional additives, other than the methyl and ethyl esters of fatty acids (b) as described above.

[0090] The composition can thus include:

[0091] - one or more additives increasing the cetane index, which may be chosen, for example, from alkyl nitrates such as 2-ethylhexyl nitrate;

[0092] - one or more detergent additives which may, by way of non-limiting examples, be chosen from amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, triazole derivatives; quaternary ammonium salts, amido alkyl betaines and mixtures thereof;

[0093] - one or more anti-foam additives which may, for example, be chosen from polysiloxanes and oxyalkylenated polysiloxanes;

[0094] - one or more demulsifying additives which may, by way of non-limiting examples, be chosen from condensation resins of at least one alkyl-phenol with at least one aldehyde, polyoxyalkylenated;

[0095] - one or more antioxidant agents which may be chosen in particular from phenolic antioxidants and amine antioxidants;

[0096] - one or more metal passivating agents, which may be chosen from triazole derivatives, alone or in a mixture;

[0097] - one or more chelating agents (or metal sequestering agents), which may in particular be chosen from amines substituted by N,N'-disalicylidene groups, such as N,N'-disalicylidene 1,2-diaminopropane (DMD).

[0098] The composition according to the invention may also comprise one or more other additives commonly used in fuels, different from the additives described previously.

[0099] The composition may typically comprise one or more other additives selected from anti-corrosion agents, dispersants, tracers, biocides, reodorants, friction modifiers, lubricity additives or smoothness additives, anti-wear agents and / or conductivity modifying agents.

[0100] According to a particularly advantageous embodiment, the composition according to the invention does not contain any additives, in particular no additives chosen from those indicated above.

[0101] In particular when used for pilot injection in a mixed-fuel engine, the composition according to the invention has proven to be sufficiently effective, without it being necessary to incorporate additives.

[0102] The use

[0103] According to the invention, a fuel composition as described above is used for pilot injection in a mixed fuel engine or "dual fuel" engine. In other words, the composition is used to initiate combustion in the mixed fuel engine, in combination with another fuel (main fuel) different from it and which feeds the combustion.

[0104] According to a preferred embodiment, the composition is used in a mixed fuel engine in combination with another fuel (mainly fueling the combustion) chosen from ammonia, methanol and liquefied natural gas, preferably from ammonia and methanol. The two fuels are injected in different proportions depending on the power required from the engine. The composition according to the invention is typically injected in a small quantity, less than that of the main fuel.

[0105] According to an advantageous embodiment, the composition according to the invention is used in an amount in the range from 0.8% to 7% by mass, relative to the total mass of fuel (i.e. the mass of main fuel and pilot fuel) supplying the engine.

[0106] The mixed fuel engine can be of any type, including a spark-ignition engine (also called a gasoline engine) or a compression-ignition engine (also called a diesel engine). Preferably, the engine is a compression-ignition engine or diesel engine.

[0107] Preferably, the composition according to the invention is used for pilot injection in a mixed-fuel compression-ignition engine fitted to a ship, i.e. a mixed-fuel compression-ignition marine engine (or mixed-fuel marine diesel engine).

[0108] The method

[0109] The present invention also relates to a method for operating a mixed fuel engine or "dual fuel" engine, consisting of: i) initiating combustion by injecting into the engine a pilot fuel composition comprising: a) at least 30% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and resulting from a process for hydrotreating fatty acids and / or acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols; and b) at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; and ii) fueling the combustion by injecting into the engine a main fuel composition, different from the pilot fuel.

[0110] According to a preferred embodiment, the main fuel is chosen from ammonia, methanol and liquefied natural gas, preferably from ammonia and methanol.

[0111] The two fuels are injected in different proportions depending on the power required from the engine. The composition according to the invention is typically injected in a small quantity, less than that of the main fuel, in particular an amount in the range from 0.8% to 7% by mass, relative to the total mass of fuel (mass of main fuel + mass of pilot fuel) injected into the engine.

[0112] The following examples are given by way of illustration of the invention, and should not be interpreted in such a way as to limit its scope.

[0113] EXAMPLES

[0114] The following examples were made from:

[0115] - a base A of paraffinic hydrocarbons consisting of a hydrotreated vegetable oil (HVO);

[0116] - a base B consisting of methyl esters of fatty acids from used cooking oil (or EMAG); and

[0117] - a base C consisting of a diesel of petroleum origin.

[0118] The characteristics of base A are detailed in Table I below:

[0119] [Table I]

[0120] This base is made up of 98.9% by mass of paraffins, of which 95.2% iso-paraffins (hereinafter i-paraffins) and 3.7% by mass of n-paraffins.

[0121] Its exact composition in terms of paraffins (excluding naphthenes) is detailed, in % mass, in Table II below:

[0122] [Table II]

[0123] The characteristics of base B are detailed in Table III below:

[0124] [Table III]

[0125] The characteristics of the C base are detailed in Table IV below:

[0126] [Table IV] Fuel compositions were prepared by mixing the bases A, B and C described above, in the proportions indicated in Table V below:

[0127] [Table V]

[0128] Compositions C0 and C3 are representative of the prior art, compositions C1 and C2 are in accordance with the invention.

[0129] Evaluation of compositions as pilot fuel in a mixed-fuel engine

[0130] The compositions described above were tested for pilot injection in a light vehicle diesel engine, the characteristics of which are detailed below (with reference to the operating speed of the engine fueled 100% by diesel fuel at full load), and which was adapted to be able to operate in mixed fuel mode with ammonia as the main fuel:

[0131] - 4-cylinder engine as standard

[0132] - Cylinder capacity: 1.5L

[0133] - Bore: 76.0 mm

[0134] - Stroke: 80.5 mm

[0135] - Direct injection at 2000 bars; piezoelectric

[0136] - Nominal power: 84 kW at 4000 rpm

[0137] Here, ammonia is injected indirectly into the combustion chamber.

[0138] The engine was set to a speed of 2000 rpm and two load levels: full load (20 bar effective mean pressure) and half load (10 bar effective mean pressure). The measurement of the concentration of unburned hydrocarbons in the exhaust gases was carried out by flame ionization detection (FID), in accordance with the method defined in EN 25140: 2010. The results obtained under full load conditions (2000 rpm, 20 bar) are presented in Table VI below, at different quantities of pilot injection of each composition (quantities expressed in milligrams per stroke - mg / cp - i.e. the mass of fuel introduced into the engine at each opening of the injector): [Table VI]

[0139] The results obtained under half-load conditions (2000 rpm, 10 bar) at different degrees of pilot injection phasing are presented in Table VII below: [Table VII]

[0140] * Pilot injection phasing before the end of the compression stroke in crankshaft degrees.

[0141] The results presented in Tables VI and VII above show that the implementation of the pilot fuels according to the invention (C1 and C2) makes it possible to obtain a reduction in unburned hydrocarbon emissions, compared to the comparative pilot fuel CO. During these tests, measurements of nitrogen oxide (NOx) emissions were also carried out in accordance with standard EN 14792, under full load conditions (2000 rpm, 20 bar) at different pilot injection pressures.

[0142] The results obtained are presented in Table VIII below:

[0143] [Table VIII]

[0144] These results show that the implementation of the pilot fuels according to the invention (C1 and C2) makes it possible to obtain a reduction in nitrogen oxide emissions, compared to the comparative pilot fuel C3.

Claims

CLAIMS 1. Use, for pilot injection in a mixed fuel engine, of a fuel composition comprising: a) at least 30% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and resulting from a process for hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols; and b) at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

2. Use according to the preceding claim, characterized in that the paraffinic hydrocarbon base(s) (a) are derived from the transformation of biological raw materials.

3. Use according to any one of the preceding claims, characterized in that the paraffinic hydrocarbon base(s) (a) consist of hydrogenated fatty acids and / or hydrogenated fatty acid esters (HEFA), and preferably hydrotreated vegetable oils (HVO).

4. Use according to any one of the preceding claims, characterized in that the fuel composition has an eco-material content of at least 50% by mass, preferably at least 60% by mass, more preferably at least 70% by mass, relative to the total mass of the composition.

5. Use according to any one of the preceding claims, characterized in that the paraffinic hydrocarbon base(s) (a) contain at least 60% by mass of iso-paraffins, preferably at least 70% by mass of iso-paraffins and more preferably at least 80% by mass of iso-paraffins, relative to the total mass of the base(s) (a).

6. Use according to any one of the preceding claims, characterized in that the composition comprises at least 40% by mass, preferably at least 50% by mass, relative to the total mass of the composition, of one or more paraffinic hydrocarbon bases (a).

7. Use according to any one of the preceding claims, characterized in that the composition comprises the base(s) (b) in a content within the range from 15 to 70% by mass, preferably from 20 to 70% by mass, more preferably from 30 to 60% by mass, better still from 40 to 60% by mass, and better still from 50 to 60% by mass, relative to the total mass of the composition.

8. Use according to any one of the preceding claims, characterized in that the composition comprises at least one base (b) consisting of a mixture of fatty acid methyl esters (EMAG).

9. Use according to any one of the preceding claims, characterized in that the fuel composition further comprises at least one additional base consisting of a cut of liquid hydrocarbons of petroleum origin, chosen from middle distillates whose distillation interval at atmospheric pressure is in the range from 100 to 500°C, preferably from 120 to 450°C, preferably from 190 to 400°C, preferably from 210 to 350°C, more preferably from 220 to 330°C; and more preferably at least one fuel base of petroleum origin chosen from diesel fuels.

10. Use according to the preceding claim, characterized in that said additional base represents from 5 to 50% by mass, preferably from 10 to 40% by mass, more preferably still from 20 to 30% by mass, relative to the total mass of the composition.

11. Use according to any one of claims 1 to 8, characterized in that the fuel composition comprises as sole bases the base(s) a) of paraffinic hydrocarbons and the base(s) b) consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

12. Use according to any one of the preceding claims, characterized in that the fuel composition further comprises one or more additional additives, different from the methyl and ethyl esters of fatty acids (b), preferably chosen from cetane index increasing additives, detergent additives, anti-foam additives, demulsifying additives, antioxidants, anti-oxidants, chelating agents, anti-corrosion agents, dispersants, tracers, biocides, reodorants, friction modifiers, lubricity additives or smoothness additives, anti-wear agents and / or conductivity modifying agents.

13. Use according to any one of the preceding claims, characterized in that the fuel composition is used in combination with another fuel chosen from ammonia, methanol and liquefied natural gas, preferably from ammonia and methanol.

14. Use according to any one of the preceding claims, characterized in that the mixed fuel engine is a spark ignition engine or a compression ignition engine, preferably a compression ignition engine, and more preferably a compression ignition marine engine.

15. Method of operating a mixed fuel engine comprising: i) initiating combustion by injecting into the engine a pilot fuel composition comprising: a) at least 30% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and resulting from a process for hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols; and b) at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; and ii) fueling the combustion by injecting into the engine a main fuel composition, different from the pilot fuel.

16. Method according to the preceding claim, characterized in that the main fuel is chosen from ammonia, methanol and liquefied natural gas, preferably from ammonia and methanol.

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