Fuel mixture comprising marine fuel and lignin

Abstract

Fuel mixture comprising; (a) from 80% by weight to 99.99% by weight, preferably from 85% by weight to 99.95% by weight, of marine fuel; (b) from 0.01% by weight to 20% by weight, preferably from 0.05% by weight to 15% by weight, of liquid or solid lignin; the sum of (a) + (b) being equal to 100; wherein said marine fuel has the following characteristics: - a density, at 15°C, comprised between 890 kg / nr and 1010 kg / m3, preferably comprised between 910 kg / m3 and 991 kg / m3; - a kinematic viscosity, at 50 C, comprised between 6 mm2 / s and 700 mm2 / s, preferably comprised between 20 mm2 / s and 500 mm2 / s; - a total quantity of post-hot filtration sediments (TSA - Total Sediment Aged) less than or equal to 0.1% m / m; - an acidity (TAN - Total Acid Number) less than or equal to 2.5 mg KOH / g, preferably comprised between 0.05 mg KOH / g and 2.4 mg KOH / g; - a Conradson carbon residue (CCR) less than or equal to 20% m / m. Said fuel mixture can advantageously be used, as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

Description

[0001] FUEL MIXTURE COMPRISING MARINE FUEL AND LIGNIN

[0002] DESCRIPTION

[0003] The present invention relates to a fuel mixture comprising marine fuel and lignin.

[0004] More particularly, the present invention relates to a fuel mixture comprising marine fuel and liquid or solid lignin, in specific quantities, said marine fuel having specific characteristics.

[0005] Said fuel mixture can advantageously be used, as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

[0006] The present invention also relates to the use of said fuel mixture as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

[0007] There are two basic types of marine fuel: distillate-based marine fuel, also known as marine diesel [“Marine Gas Oil” (MGO) or “Marine Diesel Oil” (MDO)]; or residual marine fuel [“Residual Marine Fuel Oil” (RMFO)], also known as heavy marine fuel oil [“Heavy Marine Fuel Oil” (HMFO)].

[0008] Large ocean-going vessels have relied on residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)], to power large combustion engines for over 50 years.

[0009] However, the high content of heavy substances, and in particular aromatic- based substances (for example, polynuclear aromatic compounds, asphaltenes) residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)] may be critical for optimal combustion in the combustion engines in which it is used. For this reason, it is important to evaluate the OCR parameter (“Conradson carbon residue”) representative of the coke forming tendency. Specifically, the CCR parameter is indicative of the formation of carbonaceous deposits that occur on the injectors, on the pistons, on the piston rings that might give rise to tribological phenomena (abrasive wear) and delayed combustion (greater flame area in the cylinder), with a reduction in the lubricating power exerted by the oil. Reducing this parameter therefore means not only improving the combustion of the fuel, but also extending the life of the engine itself.

[0010] Lignin is one of the most industrially accumulated waste materials. The main source of lignin waste (the second most common natural polymer on the planet, after cellulose) comes from the paper industry. However, its disposal is very complicated and is presently carried out by means of incinerators, which are able to drastically reduce the volume thereof, while recovering energy. However, this process involves the production of contaminants in both gaseous and solid form, with consequent emissions of carbon dioxide (CO2) and carbon monoxide (CO). The remaining amount of lignin produced comes mainly from biorefineries, i.e., from biological processes such as, for example, treating lignocellulosic biomass in order to obtain biofuels. In said processes, cellulose is extracted with the aim of obtaining glucose, which is then used in the fermentation process from which bioalcohol, in particular bio-ethanol, is obtained, with the consequent high added value. However, lignin remains a by-product and is disposed of, again, by incineration. The extraction of lignin from lignocellulosic biomass, which can be carried out by means of various technologies, for example, by chemical, physical, biological or mechanical means, is in fact necessary before subjecting said lignocellulosic biomass to the enzymatic hydrolysis process to obtain glucose, in order to avoid the inhibition of the enzymes usually used in said process.

[0011] Processes for obtaining bio-oil from lignin for the production of bio-fuels, especially diesel and naphtha cutting, are known in the art.

[0012] For example, U.S. Patent Application US 2020 / 0231879 relates to a process for producing a distilled fuel from lignin comprising: preparing a biomass-derived lignin solvent; dissolving the lignin in the biomass-derived lignin solvent; and separating undissolved lignin from mineral matter to produce synthetic crude oil (“syncrude”).

[0013] International patent application WO 2019 / 053287 relates to a process for producing crude oil from lignin (“Crude Lignin Oil” - CLO), said process comprising the steps of providing a feedstock rich in lignin and subjecting it to a treatment in a polar organic solvent selected from, for example, alcohols, ketones, esters, or mixtures thereof, in the absence of an effective amount of a reaction promoter, such as a heterogeneous and / or homogeneous catalyst and / or hydrogen, and providing a lignin-based composition, said treatment comprising the step of contacting said lignin-rich feedstock with a polar organic solvent under the following operating conditions: temperature up to 210 C, pressure less than 50 bar and residence time up to 240 minutes, wherein the weight / volume (w / v) ratio between the lignin (in the lignin-rich feedstock) and the organic solvent is comprised between 1 : 1.5 and 1 : 15, or between 1 :2 and 1 : 10, or between 1 :2 and 1 :5. The crude lignin oil (CLO) obtained from the aforesaid process is said to be particularly useful as a fuel or as a chemical component.

[0014] The use of lignin as an additive in fuels is also known.

[0015] For example, European patent application EP 3045513 relates to a process for producing substantially diesel-soluble lignin-based liquid fuel comprising the steps of:

[0016] (i) providing lignin-rich solid residues from lignocellulosic biomass feedstock that has been hydrothermally pre-treated and subsequently subjected to hydrolysis by cellulase enzyme;

[0017] (ii) subjecting the lignin-rich solid residue to solvolysis in ethanol or methanol in the absence of an effective amount of added catalyst or added H2gas, with a water content of between 0.1% by weight and 15% by weight and a w / w ratio of solid to solvent comprised between 0.025 and 0.160, at a temperature comprised between 370 C and 420 C, for a period comprised between 200 minutes and 280 minutes; and

[0018] (iii) recovering the liquid product from the solvolysis mixture as a heavy liquid fraction having a boiling point above 120 C remaining after distillation of one or more light fractions, wherein the O:C ratio of the recovered heavy liquid fraction is less than 0.25.

[0019] Also described is a lignin-diesel liquid fuel comprising diesel oil or marine diesel [“Marine Diesel Oil” (MDO)] to which lignin-based liquid fuel obtained from the above reported process has been added between 1% by weight and 25% by weight.

[0020] European Patent EP 3307751 relates to a composition for use in refinery processes for producing fuels, comprising lignin and a solvent, wherein the lignin comprises more than one C7 alkyl group connected to the lignin through a linker group, wherein some of the linker groups are ethers and some are esters; and wherein the solvent comprises a carrier liquid selected from hydrocarbon oil, crude oil, bunker oil, mineral oil, fatty acid or esterified fatty acid.

[0021] US patent application US 2011 / 239973 relates to a fuel mixture used for combustion comprising a suspension of combustible solid powder and liquid fuel, wherein said combustible solid powder comprises a powder selected from lignin, nitrification products of biomass and total biomass powder or any combination thereof and said liquid fuel comprises a fuel selected from petrol, kerosene, diesel oil, heavy oil used for combustion, emulsified heavy oil and absolute ethanol or any combination thereof. The aforesaid patent application also relates to a method for using and producing said fuel mixture, as well as to an engine using said mixture and to a needle valve and a plunger for said engine.

[0022] The aforesaid fuel mixture could be used as a substitute for the current liquid fuel for combustion engines and have advantages, including important characteristics of energy saving, environmental protection, safety and low costs.

[0023] From the above, in order to obtain fuel mixtures comprising lignin, modified lignin is used or, if lignin is used as such, said fuel mixtures require complex, energy-intensive production processes and the use of special engines. Furthermore, there is no specific menti on in the aforesaid documents of fuel mixtures comprising marine fuel, in particular residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)] and lignin as such, nor is there any mention of the ability of lignin to reduce the Conradson carbon residue (CCR) of said fuel mixtures without adversely affecting the remaining characteristics.

[0024] The Applicant has posed the problem of finding a fuel mixture comprising a specific marine fuel, in particular a residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)] and lignin as such, which can be obtained through a simple, low energy consumption process, and which presents an improvement in the Conradson carbon residue (CCR) without negatively affecting the remaining characteristics such as, for example, the sulphur content.

[0025] The Applicant has now found a fuel mixture comprising marine fuel, in particular residual marine fuel [Residual Marine Fuel OiI (RMFO) or Heavy Marine Fuel Oil (HMFO)], and liquid or solid lignin, in specific quantities, said marine fuel having specific characteristics. Said fuel mixture can be obtained through a simple, low energy consumption process, and shows an improvement in the Conradson carbon residue (RCC) compared to the starting marine fuel, without negatively affecting the remaining characteristics such as, for example, the sulphur content. Said fuel mixture can advantageously be used, as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

[0026] The object of the present invention is therefore a fuel mixture comprising:

[0027] (a) from 80% by weight to 99.99% by weight, preferably from 85% by weight to 99.95% by weight, of marine fuel;

[0028] (b) from 0.01% by weight to 20% by weight, preferably from 0.05% by weight to 15% by weight, of liquid or solid lignin; the sum of (a) + (b) being equal to 100; wherein said marine fuel has the following characteristics: a density, at 15 C, comprised between 890 kg / m3and 1010 kg / m3, preferably comprised between 910 kg / m3and 991 kg / m3; a kinematic viscosity, at 50 C, comprised between 6 mm2 / s and 700 mm2 / s, preferably comprised between 20 mm2 / s and 500 mm2 / s; a total quantity of post-hot filtration sediments (TSA - Total Sediment Aged) less than or equal to 0.1% m / m; an acidity (TAN - Total Acid Number) less than or equal to 2.5 mg KOH / g, preferably comprised between 0.05 mg KOH / g and 2.4 mg KOH / g; a Conradson carbon residue (CCR) less than or equal to 20% m / m.

[0029] For the purpose of the present description and of the following claims, the characteristics of the marine fuel have been measured in accordance with standard ISO 8217:2017.

[0030] For the purpose of the present description and of the following claims, the definitions of the numeric ranges always include the extremes unless specified otherwise.

[0031] For the purpose of the present description and of the following claims, the terra “comprising” also includes the terms “which essentially consists of’ or “which consists of’.

[0032] For the purpose of the present description and of the following claims, the term “solid lignin” means lignin in powder form.

[0033] In accordance with a preferred embodiment of the present invention, said marine fuel is a residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)].

[0034] In accordance with a preferred embodiment of the present invention, said liquid lignin is Kraft lignin.

[0035] Kraft lignin is a product deriving from the paper industry and is obtained through the “Kraft Process”.

[0036] For the purpose of the present description and of the following claims, the term “Kraft lignin” means the scrap of the paper industry that comprises lignin originating from the “kraft black liquor”. The “kraft black liquor” is an alkaline aqueous solution of lignin residues, hemicellulose and inorganic chemicals used in a kraft pulp production process. The “kraft black liquor” deriving from the pulping process comprises components from different species of soft and hard wood in various proportions. Lignin can be separated from the “kraft black liquor” by means of various techniques including, for example, precipitation and filtration. Lignin usually begins to precipitate at pH values below 11 - 12. Different pH values can be used to precipitate lignin fractions with different properties. These lignin fractions differ from each other by molecular weight distribution, for example, weight-average molecular weight (Mw) and number-average molecular weight (Mn), polydispersity (i.e., Mw / Mnratio), hemicellulose, and extractive contents. The molar mass of lignin precipitated at a higher pH value is greater than the molar mass of lignin precipitated at a lower pH value. Further, the molecular weight distribution of the lignin fraction precipitated at a lower pH value is broader than the molecular weight distribution of the lignin fraction precipitated at a higher pH value. Precipitated lignin can be purified from inorganic impurities, hemicellulose and wood extracts using acid washing steps. Further purification can be obtained by filtration.

[0037] In accordance with a preferred embodiment of the present invention, in the case of using the liquid lignin, said fuel mixture comprises:

[0038] (a) from 80% by weight to 99.99% by weight, preferably from 85% by weight to 99.95% by weight, of marine fuel;

[0039] (b) from 0.01% by weight to 20% by weight, preferably from 0.05% by weight to 15% by weight, of liquid lignin; the sum of (a) + (b) being equal to 100.

[0040] In accordance with a preferred embodiment of the present invention, said solid lignin may be selected, for example, from: pre-treated lignin from biorefinery, i.e. deriving from a process in which the starting lignocellulosic biomass is subjected to a steam explosion process to separate the cellulosic matrix from the lignin which is subsequently subjected to a purification stage obtaining dried and purified lignin; non-pretreated lignin, coming from biorefinery, i.e. deriving from a process in which the starting lignocellulosic biomass is subjected to a steam explosion process to separate the cellulosic matrix from the lignin which is used as such without being subjected to a purification stage.

[0041] Preferably, said lignocellulosic biomass can be selected, for example, from: vegetables expressly grown for energy use such as, for example, miscanthus, panicum (Panicum virgatum), common cane (Arundo donax}. vegetables not expressly grown for energy use such as, for example, sorghum (for example, sorghum fibres); scraps (panels) (oilseed pressing panel cakes or oilseed squeezing panel cakes) deriving from the pressing of plant seeds such as, for example, camelina, brassica, soybean, sunflower, canola, safflower, flax. Hevea, castor, cotton, Crambe; scraps, residues and waste products deriving from agriculture, such as, for example, guayule, maize (for example, maize stalks, maize cobs), soybean, cotton, flax, rapeseed, wheat (for example, wheat straw), rice (for example, rice straw, rice chaff, rice husk), sugar cane (for example, sugar cane straw, sugar cane bagasse), palm (for example, palm leafs, palm trunks, palm mibrids, palm empty fruit bunches); scraps, residues and waste products deriving from forestation, forestry, or wood processing such as, for example, poplar, alder, birch; scraps from agri-food products intended for human consumption or animal husbandry ; residues, not chemically treated, from the paper industry; waste coming from the separate collection of solid urban waste (for example, urban vegetal origin waste, paper); algae such as, for example, microalgae or macroalgae, in particular macroalgae.

[0042] In accordance with a preferred embodiment of the present invention, said solid lignin can be subjected to a preliminary grinding process before being used. Preferably, said lignin can be ground until obtaining particles with a diameter comprised between 30 μm and 500 μm, more preferably comprised between 50 μm and 400 μm.

[0043] In accordance with a preferred embodiment of the present invention, in the case of using solid lignin, said fuel mixture comprises:

[0044] (a) from 90% by weight to 99.99% by weight, preferably from 94% by weight to 99.95% by weight, of marine fuel;

[0045] (b) from 0.01% by weight to 10% by weight, preferably from 0.05% by weight to 6% by weight, of solid lignin; the sum of (a) + (b) being equal to 100.

[0046] In accordance with a further preferred embodiment of the present invention, said liquid or solid lignin can be used in mixture with at least one polar solvent selected, for example, from: mono- or poly-alcohols such as, for example, methanol, ethanol, glycerin; ketones such as, for example, acetone, methylketone; ethers such as, for example, methyl ethyl ether, methyl tert-butyl ether.

[0047] In accordance with a further preferred embodiment of the present invention, in said liquid or solid lignin / at least one polar solvent mixture, said liquid or solid lignin may be present in an amount comprised between 5% by weight and 70% by weight, preferably comprised between 10% by weight and 60% by weight, with respect to the total weight of said liquid or solid lignin / at least one polar solvent mixture.

[0048] In accordance with a preferred embodiment of the present invention, in the case of using said liquid or solid lignin / at least one polar solvent mixture, said fuel mixture comprises:

[0049] (a) from 80% by weight to 99% by weight, preferably from 85% by weight to 98.5% by weight, of marine fuel;

[0050] (b) from 1% by weight to 20% by weight, preferably from 1.5% by weight to 15% by weight, of liquid or solid lignin / at least one polar solvent mixture; the sum of (a) + (b) being equal to 100.

[0051] The fuel mixture subject-matter of the present invention can be obtained by directly mixing the liquid or solid lignin in the marine fuel, at a temperature comprised between 25 C and 290°C, preferably comprised between 30°C and 280°C, for a time comprised between 10 minutes and 180 minutes, preferably comprised between 15 minutes and 160 minutes.

[0052] Alternatively, the fuel mixture subject-matter of the present invention can be obtained by mixing the liquid or solid lignin / at least one polar solvent mixture in the marine fuel, at a temperature comprised between 25°C and 290°C, preferably comprised between 30°C and 280°C, for a time comprised between 10 minutes and 180 minutes, preferably comprised between 15 minutes and 160 minutes.

[0053] As mentioned above, said fuel mixture can advantageously be used, as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

[0054] Accordingly, it is a further object of the present invention the use of the fuel mixture as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

[0055] As mentioned above, the fuel mixture subject-matter of the present invention has an improvement of the Conradson carbon residue (CCR) compared to the starting marine fuel. The improvement of the Conradson carbon residue (CCR) was evaluated in accordance with the following equations:

[0056] 1-2

[0057] Mixtures of marine fuel and solid ligni

[0058] Pre-treated solid lignin from a biorefinery, i.e. deriving from a process in which the starting lignocellulosic biomass was subjected to a steam explosion process to separate the cellulosic matrix from the lignin which is subsequently subjected to a purification stage, obtaining dried and purified lignin, comprising oligomers in quantity equal to about 7% by weight with respect to the total weight of the dry lignin, and marine fuel (the quantities are reported in Table 1), were placed in a 1 -litre flask: the whole was kept, under stirring, at 100°C, for 120 minutes, obtaining a fuel mixture that was subjected to characterization in accordance with standard ISO 8217:2017,

[0059] In Example 1 and Example 2, two different marine fuels BTZ (FUEL OIL 380 - 0.5% S RMG 380 - Eni S.p.A) (BTZ 1 in Example 1 and BTZ 2 in Example 2) having the characteristics reported in Table 1 (measured in accordance with standard ISO 8217:2017) were used.

[0060] Also solid lignin was subjected to characterization in accordance with standard ISO 8217:2017. es 3-5

[0061] Mixtures of marine fuel and solid lignin / polar solvent mixture

[0062] For this purpose, the following mixtures were prepared.

[0063] 2.5 g of pretreated solid lignin from a biorefmery obtained as described in Example 1 and 2.5 g of glycerin (Merck) were placed in a 1-litre reactor (the amounts are reported in Table 1): the whole was kept, under stirring, at 100 C, for 120 minutes, obtaining a solid lignin / glycerin mixture that was subjected to characterization in accordance with standard ISO 8217:2017 (Mix 1).

[0064] Mix 2 and Mix 3 were also prepared, operating as follows. 2.5 g of pre-treated solid lignin from a biorefinery obtained as described in Example 1 and 2.5 g of acetone (Merck) were placed in a 1-litre flask: the whole was kept, under stirring, at 60 C, for 120 minutes, obtaining a solid lignin / acetone mixture (Mix 2). 2-5 g of pretreated solid lignin from a biorefinery obtained as described in

[0065] Example 1 and 2.5 g of ethanol (Merck) were placed in a 1-litre flask: the whole was kept, under stirring, at 70 C, for 120 minutes, obtaining a solid lignin / ethanol mixture (Mix 3).

[0066] Mix 1 (Example 3), or Mix 2 (Example 4), or Mix 3 (Example 5) and marine fuel BTZ 2 (FUEL OIL 380 - 0.5% S RMG 380 - Eni S.p.A), having the characteristics reported in Table 1 (measured in accordance with standard ISO 8217:2017) were placed in a 1-litre flask: the whole was kept, under stirring, for 120 minutes: at 100 C (Mix 1 - Example 3); - at 60 C (Mix 2 - Example 4); and at 70 C (Mix 3 - Example 5); obtaining a fuel mixture that was subjected to characterization in accordance with standard ISO 8217:2017.

[0067]

[0068]

Claims

CLAIMS1. Fuel mixture comprising:(a) from 80% by weight to 99.99% by weight, preferably from 85% by weight to 99.95% by weight, of marine fuel;(b) from 0.01% by weight to 20% by weight, preferably from 0.05% by weight to 15% by weight, of liquid or solid lignin; the sum of (a) + (b) being equal to 100; wherein said marine fuel has the following characteristics: a density, at 15°C, comprised between 890 kg / nri and 1010 kg / m3, preferably comprised between 910 kg / m3and 991 kg / m3; a kinematic viscosity, at 50 C, comprised between 6 mm2 / s and 700 mm2 / s, preferably comprised between 20 mm2 / s and 500 mm2 / s; a total quantity of post-hot filtration sediments (TSA - Total Sediment Aged) less than or equal to 0.1% m / m; an acidity (TAN - Total Acid Number) less than or equal to 2.5 mg KOH / g, preferably comprised between 0.05 mg KOH / g and 2.4 mg KOH / g; a Conradson carbon residue (CCR) less than or equal to 20% m / m.

2. Fuel mixture according to claim 1, wherein said marine fuel is a residual marine fuel [Residual Marine Fuel Oil (RMFO) or Heavy Marine Fuel Oil (HMFO)].

3. Fuel mixture according to claim 1 or 2, wherein said liquid lignin is Kraft lignin.

4. Fuel mixture according to any of the previous claims, wherein in the case of using liquid lignin, said fuel mixture comprises:(a) from 80% by weight to 99.99% by weight, preferably from 85% by weight to 99.95% by weight, of marine fuel,(b) from 0.01% by weight to 20% by weight, preferably from 0.05% by weight to 15% by weight, of liquid lignin; the sum of (a) + (b) being equal to 100.

5. Fuel mixture according to claim 1 or 2, wherein said solid lignin is selected from:pre-treated lignin from biorefinery, i.e. deriving from a process in which the starting lignocellulosic biomass is subjected to a steam explosion process to separate the cellulosic matrix from the lignin which is subsequently subjected to a purification stage obtaining dried and purified lignin, non-pretreated lignin, coming from biorefinery, i.e. deriving from a process in which the starting lignocellulosic biomass is subjected to a steam explosion process to separate the cellulosic matrix from the lignin which is used as such without being subjected to a purification stage.

6. Fuel mixture according to claim 5, wherein said lignocellulosic biomass is selected from: vegetables expressly grown for energy use such as miscanthus, panicum (Panicum virgatum), common cane (Arundo donax)\ vegetables not expressly grown for energy use such as sorghum, scraps (panels) (oilseed pressing panel cakes or oilseed squeezing panel cakes) deriving from the pressing of plant seeds such as, for example, camelina, brassica, soybean, sunflower, canola, safflower, flax. Hevea, castor, cotton, Crambe; scraps, residues and waste of products deriving from agriculture such as, for example, guayule, com, soybean, cotton, flax, rapeseed, wheat, rice, sugar cane, palm; scraps, residues and waste of products deriving from forestation, forestry, or wood processing such as poplar, alder, birch, scraps from agri-food products intended for human consumption or animal husbandry; residues, not chemically treated, from the paper industry; waste coming from the separate collection of municipal solid waste; algae such as microalgae or macroalgae, in particular macroalgae.

7. Fuel mixture according to claim 5 or 6, wherein before being used, said solid lignin is subjected to a preliminary grinding process.

8. Fuel mixture according to claim 1 or 2, wherein in the case of using solid lignin, said fuel mixture comprises:(a) from 90% by weight to 99.99% by weight, preferably from 94% by weight to 99.95% by weight, of marine fuel;(b) from 0.01% by weight to 10% by weight, preferably from 0.05% by weight to 6% by weight, of solid lignin; the sum of (a) + (b) being equal to 100.

9. Fuel mixture according to any of the previous claims, wherein said liquid or solid lignin is used in mixture with at least one polar solvent selected from: mono- or poly-alcohols such as methanol, ethanol, glycerin; ketones such as acetone, methyl ketone, ethers such as methyl ethyl ether, methyl tert-butyl ether.

10. Fuel mixture according to claim 9, wherein in said liquid or solid lignin / at least one polar solvent mixture, said liquid or solid lignin is present in an amount comprised between 5% by weight and 70% by weight, preferably comprised between 10% by weight and 60% by weight, with respect to the total weight of said liquid or solid lignin / at least one polar solvent mixture.

11. Fuel mixture according to claim 9 or 10, wherein in the case of using said liquid or solid lignin / at least one polar solvent mixture, said fuel mixture comprises:(a) from 80% by weight to 99% by weight, preferably from 85% by weight to 98.5% by weight, of marine fuel;(b) from 1% by weight to 20% by weight, preferably from 1.5% by weight to 15t% by weight, of liquid or solid lignin / at least one polar solvent mixture, the sum of (a) + (b) being equal to 100.

12. Use of the fuel mixture according to any one of claims 1 to 11, as such, or mixed with other renewable or fossil marine fuels, in combustion engines for ships.

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