Lignin pellets

Abstract

A method for producing lignin pellets is disclosed. The lignin pellets include lignin in an amount of 90-99.99 wt.% based on a total weight of the lignin pellets. The method includes providing a lignin powder, mixing an additive with the lignin powder to provide a mixed lignin powder, and subjecting the mixed lignin powder to a pelletizing process to provide lignin pellets, the lignin pellets having a diameter of 2.5-8 mm. Additionally, lignin pellets, products, and uses of the lignin pellets are disclosed.

Description

[Technical field]

[0001] The present disclosure relates to a method for producing lignin pellets. The present disclosure further relates to the use of lignin pellets in products. [Background technology]

[0002] Pellets are made from compressed organic matter or biomass. They can be made, for example, from industrial waste and by-products, food waste, agricultural residues, energy crops, and virgin wood. Wood pellets are a type of pellet that are generally made from compressed sawdust. However, there is still a need for further biopellets that have properties that make them suitable for, for example, transportation, storage, and use. The pellets must be able to maintain their shape and not break during transportation or storage. They must also be able to withstand temperature and moisture changes during transportation and storage. Summary of the Invention

[0003] A method for producing lignin pellets is disclosed. The lignin pellets contain lignin in an amount of 90-99.99% by weight based on the total weight of the lignin pellets. The method comprises: providing a lignin powder having a dry matter content of 80-99%; mixing the additive with the lignin powder to provide a mixed lignin powder, wherein the amount of the additive mixed with the lignin powder is 0.1 to 10 wt. % based on the total weight of the mixed lignin powder; subjecting the mixed lignin powder to a pelletizing process at a temperature of 50-90° C. and a pressure of 5.0-9.0 MPa to provide lignin pellets; Including, The diameter of the lignin pellets is 2.5 to 8 mm.

[0004] Further disclosed is a lignin pellet, the lignin pellet comprising lignin in an amount of 90-99.9% by weight based on the total weight of the lignin pellet, at least one additive, and having a diameter of 2.5-8 mm.

[0005] Further disclosed is a product comprising lignin pellets as defined herein and particulates in an amount of up to 7% by weight based on the total weight of the lignin pellets and particulates.

[0006] Further disclosed is the use of lignin pellets as defined herein for the manufacture of a product comprising lignin pellets and particulates in an amount of up to 7% by weight based on the total weight of the lignin pellets and particulates.

[0007] The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate one embodiment. [Brief description of the drawings]

[0008] [Figure 1] 1 shows the results of the durability test in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A method for producing lignin pellets is disclosed, wherein the lignin pellets contain lignin in an amount of 90-99.99% by weight based on the total weight of the lignin pellets. The method comprises: providing a lignin powder having a dry matter content of 80-99%; mixing the additive with the lignin powder to provide a mixed lignin powder, wherein the amount of the additive mixed with the lignin powder is 0.1 to 10 wt. % based on the total weight of the mixed lignin powder; subjecting the mixed lignin powder to a pelletizing process at a temperature of 50-90° C. and a pressure of 5.0-9.0 MPa to provide lignin pellets; Including, The diameter of the lignin pellets is 2.5 to 8 mm.

[0010] Further disclosed is a lignin pellet having a diameter of 2.5 to 8 mm, comprising lignin in an amount of 90 to 99.9% by weight based on the total weight of the lignin pellet and at least one additive.

[0011] Further disclosed is a product comprising lignin pellets as defined herein and particulates in an amount of up to 7% by weight based on the total weight of the lignin pellets and particulates.

[0012] Further disclosed is the use of lignin pellets as defined herein for the manufacture of a product comprising lignin pellets and particulates in an amount of up to 7% by weight based on the total weight of the lignin pellets and particulates.

[0013] In one embodiment, the bulk density of the lignin pellets is 0.4-0.7 kg / L. The bulk density of the lignin pellets can be used to describe the quality of the pellets. The bulk density can be determined using a Powtec SMG 697 machine according to ISO standard 697:1981. First, a clean, empty tray is weighed to the nearest 0.1 g and the tray is placed in the correct position. The lignin pellets are poured into the hopper of the machine while the locking plate is set to block the lignin pellet outlet. When the hopper is full, the locking plate is moved quickly to allow the material to spill out of the lower tray. When ready, the surface of the tray is smoothed with a straightedge and weighed again. This is repeated twice for each type of lignin pellet. The bulk density of the sample is calculated according to the following formula:

number

[0014] Generally, pellets are produced by compressing a raw material or mixture. The mixture is fed into a press where it is squeezed through a die with holes of the required size. During production, a certain amount of fines, i.e., broken up raw material, may be formed and ultimately present in the pellets. When lignin is pelletized, the pressure and temperature of the pelleting process affect the mixture, causing it to plasticize slightly and form a natural "glue" that holds the pellets together as it cools.

[0015] The inventors have surprisingly found that the methods disclosed in this disclosure can produce lignin pellets that are durable for transportation and storage in bulk, for example in big bags, silos, and the like.

[0016] In one embodiment, the lignin pellets are dispersible. The lignin pellets may be dispersible as is or after crushing. The inventors have surprisingly found that by producing lignin pellets as disclosed in the present disclosure, it is possible to produce lignin pellets that are hard enough to be stored and transported in bulk without adverse effects, but at the same time are inherently easily dispersible for further use.

[0017] In one embodiment, the method includes producing lignin pellets comprising lignin in an amount of 92-98 wt%, or 95-97 wt%, based on the total weight of the lignin pellets.

[0018] The method includes providing lignin in powder form, i.e. lignin powder. The particle size of the lignin used in powder form may meet the criteria that at least 80% by weight of the lignin passes through a 200 μm sieve. That is, 95% by weight of the lignin particles have a size of 200 μm or less. In one embodiment, the particle size of the lignin used in powder form meets the criteria that at least 95% by weight of the lignin passes through a 200 μm sieve, or a 100 μm sieve, or a 50 μm sieve, or a 32 μm sieve.

[0019] In one embodiment, the method includes providing a lignin powder with a dry matter content of 85-95%, or 88-90%. The dry matter content may be determined by drying a sample on an open dish in a heating chamber until the mass of the sample is constant (1 g, 105 °C, 3 h). The dry matter content is the ratio of the mass of the sample after drying to the mass of the sample at the time of sampling.

[0020] Supplying lignin powder with a dry matter content of 80-99% has the added utility of being able to produce lignin pellets that are durable enough for storage and transport, by influencing the amount of fines in the lignin pellets.

[0021] In the present context, the term "lignin" may refer to lignin derived from any suitable lignin source. In one embodiment, the lignin is essentially pure lignin. The expression "essentially pure lignin" should be understood to mean lignin with a purity of at least 70%, or at least 90%, or at least 95%, or at least 98%. Essentially pure lignin may contain up to 30%, or up to 10%, or up to 5%, or up to 2% of other components and / or impurities. Examples of such other components include extractives and carbohydrates, such as hemicellulose.

[0022] The lignin may contain less than 30% by weight, or less than 10% by weight, or less than 5% by weight, or less than 3% by weight, or less than 2.5% by weight, or less than 2% by weight of carbohydrates. The amount of carbohydrates present in the lignin can be measured by high performance anion exchange chromatography with a pulsed amperometric detector (HPAE-PAD) according to standard SCAN-CM 71.

[0023] The ash content of the lignin may be less than 7.5% by weight, or less than 5% by weight, or less than 3% by weight, or less than 1.5% by weight. The ash content can be determined as follows: First, the dry solids content of the sample is determined in an oven at 105 °C for 3 hours. A ceramic crucible is preheated to 700 °C for 1 hour and weighed after cooling. The sample (1.5 g to 2.5 g) is weighed into a ceramic crucible. The rimmed crucible is placed in a cold oven. The temperature of the oven is increased as follows: 20 to 200 °C, 30 min → 200 to 600 °C, 60 min → 600 to 700 °C, 60 min. Burning is continued without a lid at 700 °C for 60 min. The crucible is allowed to cool in a desiccator and a few drops of hydrogen peroxide (H2O2, 30%) are added to the sample before burning in an oven at 700 °C for 30 min. If there are still dark spots in the ash, repeat the hydrogen peroxide treatment and combustion. Cool the crucible and weigh. All weighings are done to the nearest 0.1 mg after cooling in a desiccator. Calculating the results Ash content (%)=(100a×100) / (b×c) During the ceremony, a is the weight of ash (g), b is the weight of the sample (g), c is the dry solids content (%) of the sample. The ash content of a sample refers to the mass of the sample remaining after combustion and annealing, expressed as a percentage of the dry matter content of the sample.

[0024] In one embodiment, the lignin is industrial lignin. In the context of this specification, the term "industrial lignin" may refer to lignin derived from lignin in any biomass by any technological process. In one embodiment, industrial lignin is lignin obtained from an industrial process.

[0025] The lignin used to prepare the binder composition may be selected from the group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitation lignin, biomass-derived lignin, lignin from alkaline pulping process, lignin from soda process, lignin from organosolv pulping, lignin from alkaline process, lignin from enzymatic hydrolysis process, and any combination thereof. In one embodiment, the lignin is wood lignin. The lignin may be derived from softwood, hardwood, annual plant, or any combination thereof.

[0026] "Kraft lignin" is herein to be understood as lignin derived from Kraft black liquor, unless otherwise specified. Black liquor is an alkaline aqueous solution of lignin residues, hemicellulose, and inorganic chemicals used in the Kraft pulping process. Black liquor from the pulping process contains components derived from various softwood and hardwood species in varying proportions. Lignin can be separated from the black liquor by various techniques, e.g., precipitation and filtration. Lignin usually starts 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 their molecular weight distribution, e.g., Mw and Mn, polydispersity, hemicellulose, and extractive content. The molar mass of lignin precipitated at higher pH values ​​is greater than that of lignin precipitated at lower pH values. Also, the molecular weight distribution of the lignin fraction precipitated at lower pH values ​​is broader than that of the lignin fraction precipitated at higher pH values. The precipitated lignin can be purified from inorganic impurities, hemicellulose, and wood extractives using an acidic wash step. Further purification can be accomplished by filtration.

[0027] The term "flash precipitated lignin" is to be understood herein as lignin precipitated from black liquor in a continuous process by lowering the pH of the black liquor stream to the precipitation level of the lignin using a carbon dioxide-based acidifying agent, preferably carbon dioxide, under the influence of an overpressure of 200-1000 kPa, and by suddenly releasing the pressure to precipitate the lignin. A process for the production of flash precipitated lignin is disclosed in Finnish Patent Application No. 20106073. The residence time in the above process is less than 300 seconds. Flash precipitated lignin particles with a particle size of less than 2 μm form agglomerates, which can be separated from the black liquor using, for example, filtration. The advantage of flash precipitated lignin is its high reactivity compared to normal kraft lignin. Flash precipitated lignin can be purified and / or activated as required for further processing.

[0028] Lignin can be derived from an alkaline process, which can begin with liquefying the biomass with strong alkali, followed by a neutralization process. After alkaline treatment, the lignin can be precipitated as described above.

[0029] Lignin can be derived from steam explosion, a pulping and extraction technique that can be applied to wood and other fibrous organic materials.

[0030] "Biorefinery lignin," as used herein, unless otherwise specified, should be understood to be lignin that can be recovered from a refining facility or process in which biomass is converted into fuels, chemicals, and other materials.

[0031] "Supercritically separated lignin" is herein to be understood, unless otherwise specified, as lignin that can be recovered from biomass using supercritical fluid separation or extraction techniques. Supercritical conditions correspond to temperatures and pressures above the critical point of a given substance. At supercritical conditions, no distinct liquid or gas phases exist. Supercritical water extraction or supercritical fluid extraction is a method of breaking down biomass and converting it into cellulose sugars by using water or liquids under supercritical conditions. The water or liquid acting as a solvent extracts the sugars from the plant's cellulose, leaving the lignin as solid particles.

[0032] The lignin may be derived from a hydrolysis process. The lignin derived from a hydrolysis process may be recovered from a paper pulp process or a wood chemical process.

[0033] The lignin may be derived from the organosolv process, which is a pulping technique that uses organic solvents to solubilize the lignin and hemicellulose.

[0034] In one embodiment, the lignin comprises kraft lignin, such as softwood kraft lignin. In one embodiment, the lignin is softwood kraft lignin. In one embodiment, the lignin is a combination of softwood lignin and hardwood lignin. In one embodiment, up to 30% by weight, or up to 25% by weight, or up to 10% by weight, or up to 5% by weight of the lignin is derived from hardwood.

[0035] The weight average molecular weight of the softwood kraft lignin may be 2500 to 9000 Da, or 3000 to 8000 Da, or 3500 to 7000 Da. The polydispersity index of the lignin, e.g., kraft lignin, may be 2.9 to 6.0, or 3.0 to 5.0, or 3.2 to 4.5.

[0036] Weight average molecular weight can be measured using gel permeation chromatography (GPC) equipped with a UV detector (280 nm) as follows: Dissolve the sample in 0.1 M NaOH. Filter the sample solution through a 0.45 micron PTFE filter. Measurements are performed in a sulfonated styrene-divinylbenzene copolymer matrix in 0.1 M NaOH eluent using a PSS MCX precolumn, 1000 Å and 100 000 Å columns (0.5 mL / min, T=30 °C). Molecular weight distribution of the sample is calculated relative to polystyrene sulfonate Na standards (6 pieces) Mw 891-65400. Values ​​of Mw (weight average molecular weight) and Mn (number average molecular weight), polydispersity index (PDI, Mw / Mn) are reported based on two parallel measurements.

[0037] The amount of alkali-insoluble matter of softwood kraft lignin may be less than 10%, or less than 5%, or less than 0.5%. The amount of alkali-insoluble matter may be determined as follows: First, the dry solids content of the sample is determined in an oven at 105 °C for 3 hours. 100 g of the sample is dissolved in 277 g of aqueous NaOH solution (pH 12-13) at 50-60 °C by mixing for 30 minutes. The solution is filtered in a Büchner funnel through a glass filter. The residue on the filter is washed with 0.1 M NaOH and finally with water. The filter together with the residue is dried in an oven and then weighed. The amount of alkali-insoluble matter is then calculated as follows: Alkali-insoluble matter (%) = [Weight of filter and residue (dry) (g) - Weight of filter] / [Weight of sample (g) x Dry solids content of sample (%)]

[0038] The amount of condensed syringyl groups in the softwood kraft lignin may be less than 3.0 mmol / g, or less than 2.5 mmol / g, or less than 2.0 mmol / g, as determined by 31P NMR. The amount of aliphatic OH groups in the softwood kraft lignin may be less than 3.0 mmol / g, or less than 2.5 mmol / g, as determined by 31P NMR. The amount of guaiacyl OH in the softwood kraft lignin may be at least 1.5 mmol / g, as determined by 31P NMR.

[0039] Measurements performed by 31P NMR spectroscopy after phosphitylation can be used for the quantification of functional groups (aliphatic and phenolic hydroxyl groups, as well as carboxylic acid groups). Sample preparation and measurements are performed according to the method by Granata and Argyropoulos (Granata, A., Argyropoulos, D., J. Agric. Food Chem. 1995, 43:1538-1544). An accurately weighed sample (about 25 mg) is dissolved in N,N-dimethylformamide and mixed with pyridine and the internal standard solution (ISTD) endo-N-hydroxy-5-norbornene-2,3-dicarboximide (e-HNDI). The phosphitylation reagent (200 μL) 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosphorane is slowly added and finally 300 μL of CDCl3 is added. NMR measurements are performed immediately after the addition of the reagent. The spectra are measured on a spectrometer equipped with a probe head optimized for broadband detection.

[0040] In one embodiment, providing the lignin powder comprises subjecting the lignin powder to a drying treatment. Drying the lignin powder may have the additional utility of allowing the production of lignin pellets with suitable strength or durability. Using a lignin powder with too low a dry matter content may result in lignin pellets that exhibit too low a durability for storage, transport and / or further use. Drying the lignin powder may be performed, for example, by thermal drying. Providing the lignin powder may comprise subjecting the lignin powder to a drying treatment, for example at a temperature of 70-140° C., providing a lignin powder with a dry matter content of 80-99%, or 85-95%, or 88-90%.

[0041] The drying process can be carried out in a drying device, such as an infrared dryer, a microwave dryer, an indirect dryer, a direct dryer, a paddle dryer, a flash dryer, a fluidized bed dryer, a cyclone dryer, an air dryer, an air grinder, a rotor mill, a centrifugal mill, an air turbulence mill, or an air turbulence dryer. Combinations of these can also be used.

[0042] In one embodiment, providing the lignin powder does not include drying the lignin powder.

[0043] In one embodiment, the amount of additive mixed into the lignin powder is 0.1-5 wt.%, or 0.5-3 wt.%, or 0.7-2.5 wt.%, or 1-1.8 wt.%, based on the total weight of the mixed lignin powder. This amount of additive used has the added benefit of having essentially no adverse effect on the end use of the lignin pellets produced. The ability to use less additive has an additional beneficial effect on costs, which are lower. In one embodiment, the amount of additive is 0.1-5 wt.%, or 0.5-3 wt.%, or 0.7-2.5 wt.%, or 1-1.8 wt.%, based on the total weight of the lignin pellets.

[0044] The additives may be selected from the group consisting of starches, such as potato starch and corn starch; modified starches; carboxymethylcellulose (CMC); guar gum (guar); carboxymethyl starch (CMS); lignosulfonates, such as ammonium lignosulfonate and calcium lignosulfonate; polyethylene glycol (PEG); diethylene glycol (DEG); glycols; glycerol; bentonite and other inorganic components; oils, such as vegetable oils; flours, such as potato flour, rapeseed flour, and potato skin residues; other flours from plant-based residues; sodium silicate; polyvinyl alcohol (PVA); and proteins.

[0045] In one embodiment, the additive is at least one of carboxymethylcellulose, lignosulfonate, polyethylene glycol, guar gum, polyvinyl alcohol (PVA), and bentonite. In one embodiment, the additive is at least one of carboxymethylcellulose, polyvinyl alcohol (PVA), and bentonite. In one embodiment, the additive is carboxymethylcellulose, polyvinyl alcohol (PVA), and bentonite.

[0046] In one embodiment, the method includes mixing a lubricant with the lignin powder before subjecting the mixed lignin powder to a pelleting process. The lubricant can be water. In one embodiment, the method includes mixing a lubricant with the lignin powder before subjecting the mixed lignin powder to a pelleting process, the lubricant being water, and the amount of water mixed with the lignin powder is 1-10 wt%, or 2-7 wt%, or 4-6 wt%, based on the total weight of the mixed lignin powder. Using water as a lubricant has the added benefit of lubricating the lignin without spreading it evenly throughout the lignin powder. Thus, the lubricant can aid in the formation of pellets of the lignin powder during the pelleting process. Water can also act as a plasticizer. Using water can further have the added benefit of preventing or reducing friction during the pelleting process, allowing lower temperatures to be used.

[0047] The pelleting process may be carried out at a temperature of 50-90°C, or 60-88°C, or 65-87°C, or 70-86°C, or 75-85°C, or 78-82°C. The pelleting process may be carried out under a pressure of 5.5-9.0 MPa, or 5.6-8.0 MPa, or 5.7-6.5 MPa, or 5.8-0.62 MPa. The above temperatures and pressures used during the pelleting process have the added utility of ensuring that the lignin pellets have a hardness value or durability suitable for further use.

[0048] The pelletizing process can be carried out in a pelletizing device, an example of which is a flat die pellet press or a ring die pellet press.

[0049] Flat die pellet presses, also known as flat die pellet mills, use a flat die with a slot. Powder is introduced at the top of the die, and as the die rotates, rollers press the powder through holes in the die. A cutter on the other side of the die separates the exposed pellets from the die.

[0050] The basic pelletizing principle of a ring die pellet mill is a simple operation: a mass of feedstock is distributed onto the inner surface of a rotating perforated die in front of each roll, which compresses the mass of feedstock and presses it into the holes in the die to form pellets.

[0051] The diameter of the lignin pellets can be 2.5-8mm, or 3.0-7.5mm, or 3.5-7mm, or 4-6.5mm, or 4.5-6mm. Providing lignin pellets with a minimum diameter of 2.5mm has the added utility of producing durable lignin pellets.

[0052] In one embodiment, in the pelleting process, up to 7% by weight of fines are formed in the lignin pellets, based on the total weight of the lignin pellets and fines. Thus, an amount of fines of up to 7% by weight may be formed in the lignin pellets produced or supplied. In the pelleting process, up to 7% by weight, or up to 6% by weight, or up to 5% by weight, or up to 4% by weight of fines may be formed in the lignin pellets, based on the total weight of the lignin pellets and fines. Thus, the product as defined herein may contain up to 7% by weight, or up to 6% by weight, or up to 5% by weight, or up to 4% by weight of fines, based on the total weight of the lignin pellets and fines. The amount of fines may be determined by using a test sieve (Retsch) with an opening width of 1.4 mm, placed on the empty bowl at the bottom of a laboratory sieve shaker (Retsch). A sample of 500 g of the produced pellets is weighed and poured onto the sieve, and a lid is placed. The shaker is then set to vibrate at a speed of 50 Hz for 3 minutes, after which the remaining sample on the sieve and the fine fraction on the bottom bowl are weighed. Alternatively, sieving can be done manually by shaking 5-10 times in a circular motion. The fine content is expressed as a percentage based on the following formula:

number

[0053] The inventors have surprisingly found that by using the additive and optional lubricant, lignin pellets can be provided that, as a result of the pelletizing process, the amount of fines in the lignin pellets is sufficiently low to provide durable lignin pellets that can, for example, be stored and transported without adversely affecting the lignin pellets.

[0054] In one embodiment, the durability of the supplied lignin pellets decreases by less than 8% units, or less than 7% units, or less than 6% units, or less than 5% units, or less than 4% units, or less than 3% units, or less than 2% units, or less than 1.5% units after storing the lignin pellets for 24 hours at 85% relative humidity and 40° C. Relative humidity (RH) is the ratio of actual water vapor pressure to the saturated water vapor pressure at the current temperature.

[0055] The durability of lignin pellets can be measured by a method based on the principles of ISO 17831-2:2015 (Determination of mechanical durability of pellets and briquettes. Part 2: Briquettes), with the following differences: the lignin pellets are subjected to controlled impacts by collision against each other and against the wall of a rotating test chamber. The test apparatus (or drum) is constructed from a 15.4 liter barrel, the inner surface of which is fitted with two metal baffles, parallel to the axis of the drum and facing each other. A 500 g sample of lignin pellets (sieved according to the method described above to determine the amount of fines) is weighed (to the nearest 0.1 g) and placed in the drum, which is closed. For rotation, the drum is placed on two rotating rollers equipped with an electric motor that can be driven constantly at about 36 revolutions per minute. The lignin pellets are allowed to rotate for 30 minutes, after which the drum is opened and the sample is poured onto a laboratory sieve shaker equipped with a test sieve with an opening width of 1.4 mm, and the same procedure as described above for the determination of the amount of fines is repeated.

[0056] The durability is calculated from the mass of the sample remaining after separation of the abraded microfractured particles according to the following formula: The mechanical durability of the pellets is calculated using the following formula:

number

[0057] The durability loss of the supplied lignin pellets can then be calculated using the following formula: Loss of durability (in %) = 100% - (DU (%) of lignin pellets after exposure to moisture / DU (%) of produced lignin pellets before exposure to moisture) x 100%.

[0058] The method disclosed herein has the additional utility of allowing the production of lignin pellets with high lignin content. It has been expected that pelletizing powders with high lignin content would result in lignin pellets that are too hard and plastic-like, which may not be usable for further applications. Thus, unexpectedly, the inventors have found a method for producing high lignin content pellets with properties suitable for further applications.

[0059] The lignin pellets disclosed in the present application have the additional utility of being easily transportable. The lignin pellets have the additional utility of being sufficiently hard so that they can be stored in large quantities, for example in large storage bags or silos. The lignin pellets have the additional utility of being dispersible. EXAMPLES

[0060] Reference will now be made in detail to various embodiments.

[0061] The following description discloses some embodiments based on the present disclosure in detail so that those skilled in the art can utilize those embodiments. Not all steps or features of the embodiments are described in detail because many of the steps or features will be apparent to those skilled in the art based on the present specification.

[0062] Example 1 - Production of lignin pellets and their testing In this example, samples of lignin pellets were prepared with varying amounts and additives used. In all samples, the lignin powder was: softwood kraft lignin with a dry matter content of about 90% measured at 105° C. and a particle size that met the criteria that at least 95% by weight of the lignin would pass a 32 μm sieve. The following additives were used in the following amounts: [Table 1]

[0063] The samples were prepared by mixing 10 kg of dry lignin powder (moisture content (MC) 10 wt%) with water and additives in a high-speed Cyclomix 50 mixer (Hosokawa Micron BV) to adjust the moisture content of the lignin and to mix the additives uniformly. Water was added to adjust the moisture content of the lignin to 18 wt% to reduce the risk of excessive temperature and dusting during pelleting. The additives were added as shown in Table 1 relative to the weight (g) of the lignin powder with adjusted moisture content. First, the dry lignin powder and additives were inserted into the mixer container and conditioned with nitrogen (2-3 bar) for 1 min to reduce the risk of dust explosion. The mixer was then started and set to a rotation speed of 30 Hertz (Hz), and water was poured continuously into the dry mixture through a hole in the lid of the container. Once the addition of water was completed, mixing was continued for 1 min, after which the mixture was transferred to another container.

[0064] The mixed lignin powder was then subjected to a pelleting process carried out in a pilot-sized flat die pellet press (model 14-175, KAHL) equipped with two rollers with a diameter of 130 mm. A pellet matrix with a die diameter of 4 mm and a die length of 16 mm (ratio of 1:4) was selected for the experiments. The roller spacing was adjusted to 0.1-0.2 mm. Prior to pelleting, the matrix was warmed by feeding moist and / or slightly oily sawdust into the press until an output temperature of approximately 30-40 °C was reached. To complete the warming stage, several kilos of test points of lignin were circulated through the press to reach a pellet temperature of 57-65 °C. The temperature was observed by a handheld laser thermometer immediately after the pellets were extruded from the matrix. From the tests for the particular lignin type and moisture content used, a pelleting threshold of 57-65 °C was found to be optimal.

[0065] The pellet press was frictionally heated at a rate of 63 Hz, and once a threshold was reached, the rate was reduced to 40 Hz to slow further heating, thus generating all test points under uniform conditions of a 40 Hz rate and temperatures between 57 and 65°C.

[0066] The formed samples of the supplied lignin pellets were subjected to the following measurements:

[0067] Pellet fines content As described herein, the amount of fines was determined by using a laboratory sieve shaker (Retsch) with a test sieve (Retsch) of 1.4 mm opening width placed over an empty bowl.

[0068] durability The durability of the lignin pellets was measured as described herein.

[0069] Durability after exposure to moisture Lignin pellets were conditioned in a climate chamber to simulate high humidity and high temperature storage conditions and their effect on the durability of the pellets. For example, conditions were set at 85% relative humidity (RH) and 40°C to represent weather conditions that might be found in South America.

[0070] Before starting the experiment, the pellets were kept in closed containers at laboratory storage conditions of approximately 20 °C and RH 20-30%. For the climate chamber (CLIMACELL® Evo), two 500 g portions from each type of lignin pellet were weighed to the nearest 0.1 g and placed into individual aluminum trays without lids. The weight of each empty aluminum tray was also recorded. The pellets were then transferred to the climate chamber and conditioned for 24 h.

[0071] After treatment, each tray of pellets was weighed and their mass change calculated (weight after climate chamber - weight before climate chamber). The pellets were then immediately tested for durability as described above.

[0072] The results are shown in FIG. 1 and the table below. [Table 2]

[0073] The smaller the durability loss value after exposure to moisture, the more stable the lignin pellets are.

[0074] solubility Lignin pellets were dissolved in NaOH (0.1 M) to determine the solubility. Solutions were prepared at a concentration of 1% by adding pellets (1 g ± 0.1 g) to a fixed volume of the respective organic solvent (100 mL) at room temperature (25 °C). The solutions were then magnetically stirred for 1 h before being filtered (Paper541, Whatman / GE Healthcare, China), placed in aluminum trays, and dried overnight (approximately 18 h) at 60 °C in a drying oven. This procedure was repeated for a second sample for each type of pellet.

[0075] The solubility was determined based on the insoluble residue according to the following formula:

number

[0076] The results are shown in the table below. [Table 3]

[0077] From the above results it can be concluded that the produced lignin pellets are easily dispersible.

[0078] Example 2 - Production of lignin pellets In this example, lignin pellet samples were prepared using softwood kraft lignin with a dry matter content of approximately 90% when measured at 105°C and a particle size that met the criteria that at least 95% by weight of the lignin would pass a 32 μm sieve.

[0079] Carboxymethylcellulose was used as an additive in an amount of 3 wt% based on the total weight of the mixed lignin powder. Samples were prepared by mixing 1000 kg of dry lignin powder (moisture content 10 wt%) with water and additives. The moisture content of the mixed lignin powder was 15%.

[0080] The mixed lignin powder was then subjected to a pelleting process carried out in a pellet press 33-390 (Amandus Kahl GmbH). The pellet press was heated to 40 Hz. A temperature of 83°C and an oil pressure of 6.5 MPa were used for the pelleting process. Pellets with a diameter of 4 mm were formed.

[0081] The bulk density of the pellets was 0.58 kg / L, the moisture content was 14 wt.%, and the amount of fines in the lignin pellets was 1.5% (in this test, a 2.8 mm sieve was used instead of the 1.4 mm mentioned above, and sieving was performed manually).

[0082] Example 3 - Production of lignin pellets In this example, lignin pellet samples were prepared using softwood kraft lignin with a dry matter content of approximately 85% measured at 105°C and a particle size that met the criteria that at least 95% by weight of the lignin would pass a 32 μm sieve.

[0083] Carboxymethylcellulose was used as an additive in an amount of 3 wt% based on the total weight of the mixed lignin powder. The samples were prepared by mixing the dry lignin powder (moisture content 10 wt%) with the additive. The mixed lignin powder was then subjected to a pelletizing process.

[0084] It is obvious to those skilled in the art that with the advancement of technology, the basic concept can be implemented in various ways. Therefore, the embodiments are not limited to the above examples. Instead, the embodiments can vary within the scope of the claims.

[0085] The above-mentioned embodiments may be used in any combination with each other. Some of the embodiments may be combined to form further embodiments. The methods, lignin pellets, products, and uses disclosed herein may include at least one of the embodiments described herein above. It will be understood that the benefits and advantages described above may relate to one embodiment or to several embodiments. The embodiments are not limited to those that solve any or all of the problems described or those that have any or all of the benefits and advantages described. It will be further understood that a reference to "an" item refers to one or more of such items. The term "comprising" is used herein to mean including one or more subsequent features or one or more operations without excluding the presence of one or more additional features or operations.

Claims

1. 1. A method for producing lignin pellets, wherein the lignin pellets comprise lignin in an amount of 90 to 99.9 wt. % based on a total weight of the lignin pellets, the method comprising: providing a lignin powder having a dry matter content of 80-99%; mixing an additive with the lignin powder to provide a mixed lignin powder, wherein the amount of the additive mixed with the lignin powder is 0.1 to 10 wt % based on the total weight of the mixed lignin powder; subjecting the mixed lignin powder to a pelletizing treatment at a temperature of 50 to 90°C and a pressure of 5.0 to 9.0 MPa to provide lignin pellets; Including, The method wherein the lignin pellets have a diameter of 2.5 to 8 mm.

2. 10. The method of claim 1, comprising producing lignin pellets comprising lignin in an amount of 92 to 98 wt. %, or 95 to 97 wt. %, based on the total weight of the lignin pellets.

3. 10. The method of claim 1, comprising providing a lignin powder having a dry matter content of 85-95%, or 88-90%.

4. 2. The method of claim 1, wherein the amount of additive mixed with the lignin powder is 0.1 to 5 wt.%, or 0.5 to 3 wt.%, or 0.7 to 2.5 wt.%, or 1 to 1.8 wt.%, based on the total weight of the mixed lignin powder.

5. 10. The method of claim 1, wherein the additive is at least one of carboxymethyl cellulose, lignosulfonate, polyethylene glycol, guar gum, polyvinyl alcohol, and bentonite.

6. 2. The method of claim 1, comprising mixing a lubricant with the lignin powder before subjecting the mixed lignin powder to the pelletizing process, wherein the lubricant is water, and the amount of water mixed with the lignin powder is 1 to 10 wt %, or 2 to 7 wt %, or 4 to 6 wt %, based on the total weight of the mixed lignin powder.

7. 2. The method of claim 1, wherein the bulk density of the lignin pellets is 0.4 to 0.7 kg / L.

8. 2. The method of claim 1, wherein the lignin pellets have a diameter of 3.0 to 7.5 mm, or 3.5 to 7 mm, or 4 to 6.5 mm, or 4.5 to 6 mm.

9. 10. The method of claim 1, wherein the pelletizing process forms up to 7 wt. % of fines in the lignin pellets based on the total weight of the lignin pellets and fines.

10. 10. The method of claim 1, wherein the durability of the supplied lignin pellets decreases by less than 8% units, or less than 7% units, or less than 6% units, or less than 5% units, or less than 4% units, or less than 3% units, or less than 2% units, or less than 1.5% units after storing the lignin pellets at 85% relative humidity and a temperature of 40°C for 24 hours, as determined according to the durability test described herein.

11. 1. A lignin pellet comprising lignin in an amount of 90 to 99.9 wt. % based on the total weight of the lignin pellet, and at least one additive, and having a diameter of 2.5 to 8 mm.

12. 12. The lignin pellet of claim 11, which is dispersible.

13. 12. The lignin pellet of claim 11, wherein the diameter of the lignin pellet is 3.0 to 7.5 mm, or 3.5 to 7 mm, or 4 to 6.5 mm, or 4.5 to 6 mm.

14. 12. The lignin pellet of claim 11, wherein the additive is at least one of carboxymethyl cellulose, lignosulfonate, polyethylene glycol, guar gum, polyvinyl alcohol, and bentonite.

15. 12. The lignin pellet of claim 11, wherein the lignin pellet has a decrease in durability of less than 8% units, or less than 7% units, or less than 6% units, or less than 5% units, or less than 4% units, or less than 3% units, or less than 2% units, or less than 1.5% units after storing the lignin pellet at 85% relative humidity and a temperature of 40°C for 24 hours, as determined according to the durability test described herein.

16. 12. Lignin pellets according to claim 11, wherein the amount of additive is 0.1 to 10% by weight relative to the total weight of the lignin pellets.

17. 17. A product comprising lignin pellets according to any one of claims 11 to 16 and fine particles in an amount of up to 7% by weight, based on the total weight of the lignin pellets and the fine particles.

18. Use of lignin pellets according to any one of claims 11 to 16 for the manufacture of a product comprising lignin pellets and fine particles in an amount of up to 7% by weight, relative to the total weight of the lignin pellets and the fine particles.

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