Method for producing solid biomass fuel

Abstract

A method for recycling polyethylene terephthalate (PET) to produce bis(2-hydroxyethyl) terephthalate (BHET) includes the steps of: (a) depolymerizing PET in the presence of ethylene glycol and a catalyst system, preferably in two depolymerization reactors in series, to form a depolymerized mixture containing BHET; (b) crystallizing a precipitate containing BHET from the depolymerized mixture; (c) dissolving the precipitate in a protic solvent, preferably water but also methanol, to form a solution containing BHET; (d) removing impurities from the solution to form a purified solution containing BHET; and (e) crystallizing a purified product containing BHET from the purified solution. Apparatus suitable for such a method, and the use of urea in the catalyst system, are also provided accordingly.

Description

Technical Field

[0001] The present invention relates to a method for producing solid biomass fuel and to the solid biomass fuel produced by said method. Furthermore, the present invention relates to a combustion method comprising the step of burning said solid biomass fuel so as to generate energy.

Background Art

[0002] Coal-fired power generation is used in power plants and industrial processes throughout the world. Coal and other fossil fuels are non-renewable energy resources. Over the past few decades, it has been required to reduce the consumption of coal in coal-fired power plants and instead use renewable resources for energy.

[0003] Fuels derived from biomass are an example of renewable energy sources that can be used to replace or at least partially replace coal. Biomass-derived fuels can be burned in the presence of oxygen in a combustion method for generating energy in a power plant. Biomass-derived fuels can be burned in traditional power plants originally designed for coal combustion, or biomass-derived fuels can be burned, in particular, in power plants built specifically for biomass combustion. Certain forms of biomass can be mixed with coal and burned in the same combustion method within a power plant. Such a method is known as co-firing of biomass with coal. In order to be suitable for co-firing with coal, biomass-derived combustion typically must have certain characteristics, such as a certain level of quality and homogeneity regarding properties. For example, biomass fuel containing particles of homogeneous size, density, moisture content, etc. is particularly desirable for the co-firing method. It is also desirable that the biomass fuel contains a low level of ash. The level of ash in biomass-derived fuels is typically higher than the level in coal.

[0004] Various methods for generating solid biomass fuel from biomass sources are known. WO 2014 / 087949 pamphlet discloses a method for generating solid biomass fuel, which includes steam-exploding a biomass source and then forming it into biomass blocks, and then heating the blocks so that biomass fuel is formed. The aim of this method is to produce biomass fuel that has sufficient handleability during storage and reduced chemical oxygen demand (COD) in the drainage during storage. The biomass source used in this method is palm kernel shell.

[0005] WO 2016 / 056608 pamphlet discloses a method for manufacturing solid biomass fuel, which is constructed based on the teachings of WO 2014 / 087949 pamphlet and does not require a steam-exploding step to generate fuel. This method includes a forming step of crushing a biomass source and then compressing it into biomass blocks, and then heating the biomass blocks. The biomass sources taught for use in the method are trees such as beech, betula, sugi, hinoki, European larch, almond old wood, almond shell, acacia xylem, acacia bark, walnut shell, sago palm, empty fruit bunch, meranti, and rubber.

[0006] WO 2017 / 175733 pamphlet discloses a similar method that includes a forming step of crushing a biomass source and then compressing it into biomass blocks, and then heating the biomass blocks. The method of WO 2017 / 175733 pamphlet aims to provide biomass fuel that exhibits low disintegration and achieves a reduction in COD in the drainage when exposed to rainwater. The biomass source used in this method is selected from rubber tree, acacia, meranti, eucalyptus, teak, and a mixture of larch, spruce, and oak.

[0007] Pamphlet of International Publication No. 2019 / 069849 aims to provide a biomass fuel that is easy to transport and store and has resistance to spontaneous combustion during storage. The biomass fuel includes a step of pulverizing a biomass source and then compressing and molding it into a biomass block, and is produced by a method of heating the biomass block thereafter. The biomass source for generating the fuel is selected from rubber tree, acacia tree, radiata pine, a mixture of larch, spruce and birch, and spruce, pine and fir.

[0008] Pamphlet of International Publication No. 2019 / 069860 discloses an apparatus for generating biomass solid fuel. This apparatus includes a carbonization furnace for carbonizing a formed biomass product to obtain biomass solid fuel. This apparatus further includes a yield calculation unit, a temperature measurement unit, and a control unit. The control unit controls the heat applied to the carbonization furnace based on the spontaneous combustion characteristics of the biomass fuel. The formed biomass product is formed by pulverizing a biomass source into pellets and then molding the pellets into formed biomass fuel. The biomass source is selected from rubber tree, acacia, dipterocarp, radiata pine, a mixture of larch, spruce and birch, or a mixture of spruce, pine and fir.

[0009] Pamphlet of International Publication No. 2018 / 181919 discloses a method different from those discussed above for generating solid biomass fuel. This method involves a step of hydrothermal carbonization of biomass in which a biomass source is pressurized in hot water so that the biomass is carbonized. This method has been reported to provide a biomass fuel with high yield, reduced manufacturing cost, and high pulverizability. The biomass source is selected from shells, palm kernel shells, coconut, bamboo, empty fruit bunches, mangoes, and eggplants.

[0010] International Publication No. WO 2017 / 175737 discloses a cooling device for cooling carbonized biomass. This device improves the cooling efficiency of semi-carbonized molded biomass. This device cools the biomass by spraying water. The cooler includes a vibrating flat plate and a spray section for spraying water onto the flat plate. The biomass fuel is produced by the same method as discussed above. The sources of biomass for producing the biomass fuel are Pinus densiflora, Betula platyphylla, Cryptomeria japonica, Chamaecyparis obtusa, Pinus sylvestris, almond old wood, almond shell, acacia xylem, acacia bark, walnut shell, sago palm, empty fruit bunch, meranti, and rubber tree.

[0011] Finally, International Publication No. WO 2014 / 050964 discloses a method for improving the grindability of biomass so that it can be pulverized together with coal. This method involves raising the moisture content of the pulverized lignocellulosic biomass to 10 - 50%, densifying the biomass to have a density of 0.55 g / cm 3 or more, and then subjecting the biomass to roasting. Examples of sources of biomass include wood chips, bark, sawn timber, and wood shavings.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0013] The inventors of the present invention recognize that the solid biomass fuels and methods for their production discussed in the above documents have various problems related to them. For example, all of the biomass sources described in the above documents are typically plants and trees that only exist naturally and are not easily cultivable and harvestable on a commercial scale. The inventors recognize that it is advantageous to have a biomass source that can be easily grown, harvested, or available on a commercial scale. It is also advantageous to have a biomass source that can be grown and harvested so that the quality and specific characteristics of the biomass source can be controlled. It would also be advantageous to have an alternative biomass source that does not require large-scale logging to provide a sufficient amount of biomass source for use as fuel.

[0014] In addition, the inventors have found that the biomass sources described in the above documents, all of which contain woody materials or similar materials, form particles with low homogeneity when subjected to conventional pulverization techniques known in the art. Furthermore, pulverizing the biomass source is costly due to the nature of wood and wood-like materials being difficult to pulverize. The inventors of the present invention recognize that it is advantageous to have a biomass source that can be more easily pulverized by conventional pulverization techniques known in the art and forms particles of a more homogeneous size when pulverized.

[0015] In addition, the inventors have found that solid biomass fuels prepared from biomass sources discussed in the above literature and prepared by the methods in the above literature do not have sufficient waterproof characteristics. Since solid biomass fuels need to be dry (or at least sufficiently dry) when used in combustion methods (either alone or in co-firing with coal), waterproof characteristics are important for solid biomass fuels. Biomass fuels are frequently exposed to moisture during storage or transportation (e.g., from rainwater). Therefore, biomass fuels with increased water resistance are desirable.

[0016] The inventors also recognize that the biomass fuel production methods described in the above literature do not provide fuels with sufficient quality and uniformity. In particular, the methods discussed above do not provide sufficient control over the density of the biomass during the molding step.

Means for Solving the Problems

[0017] The present invention addresses the problems discussed above in relation to previous methods. The inventors of the present invention have surprisingly found that certain biomass sources useful for providing solid biomass fuels can be grown and harvested on a commercial scale. By doing so, a defined and consistent biomass source can be provided in the growth cycle for fuel production. In addition, growing and harvesting the biomass source on a commercial scale allows for control of the quality and uniformity of the biomass source, for example, by cultivation and breeding techniques.

[0018] In addition, the inventors of the present invention have also found that solid biomass solid fuels can be produced using certain biomass sources that are agricultural waste products.

[0019] In addition to the above, the inventors of the present invention have also found that by changing the shaping step and / or the heating step of the method, biomass fuel having improved water resistance characteristics can be provided. By adapting and controlling the shaping step and the heating step of the method of the present invention, the quality and uniformity of the solid biomass fuel product are improved, and certain physical characteristics that are highly preferable for use in the combustion method are imparted to the solid biomass fuel product. Further, by adapting the shaping step and the heating step, it has been found that the yield of the solid biomass fuel is increased, and characteristics that facilitate transportation and storage are imparted to the fuel. The inventors have found that the nature of the biomass source and the specific characteristics of the shaping and heating steps act together to provide an excellent biomass fuel product for use in the combustion method that exceeds what is known in the art.

[0020] According to a first aspect of the present invention, there is provided a method for producing solid biomass fuel, comprising: (i) preparing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight; (ii) pulverizing the one or more biomass sources to provide a pulverized biomass powder having an average particle diameter (D50) of 1000 μm to 20,000 μm; (iii) compressing the pulverized biomass powder to provide a compressed biomass powder having a moisture content of less than 30% by weight; (iv) drying the compressed biomass powder to provide a dried compressed biomass powder; (v) shaping the dried compressed biomass powder to provide a shaped biomass product; (vi) heating the shaped biomass product at a temperature of 160°C to 420°C for a period of 0.25 to 5 hours to provide solid biomass fuel; and (vii) removing dust particles from the solid biomass fuel The method is provided.

[0021] Typically, the one or more biomass sources include gramineous plants, rice husks, yams, straws, corn cobs, or any combination thereof. In embodiments, the one or more biomass sources include agricultural waste.

[0022] Typically, the one or more biomass sources include gramineous plants in an amount of 20% to 80% by weight, and one or more of rice husks, yams, straws, corn cobs, or any combination thereof.

[0023] Preferably, the one or more biomass sources include gramineous plants. More preferably, the one or more biomass sources include plants of the genus Pennisetum. Most preferably, the one or more biomass sources include Pennisetum sinese Roxb.

[0024] In certain embodiments, the one or more biomass sources consist of, consist essentially of, or include (i) gramineous plants such as plants of the genus Pennisetum, such as Pennisetum sinese Roxb, (ii) a mixture of rice husks and yams, (iii) a mixture of straws and yams, and (iv) a mixture of corn cobs and yams.

[0025] Typically, step (i) of preparing the one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight includes (a) compressing the one or more biomass sources so as to have a moisture content of less than 50% by weight, and / or (b) comminuting the one or more biomass sources so as to have an average particle diameter (D50) of 30,000 μm to 60,000 μm. Preferably, the method includes both step (a) and step (b). More preferably, the method includes step (a) of compressing the one or more biomass sources before step (b) of comminuting the one or more biomass sources.

[0026] Typically, the moisture content of one or more biomass sources is 30% to 50% by weight.

[0027] Typically, step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder includes drying the compressed biomass powder such that the dried compressed biomass powder has a moisture content of 10% to 18% by weight, preferably 12% to 15% by weight.

[0028] Typically, step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder further includes mixing the compressed biomass powder particles while drying.

[0029] Typically, step (v) of molding the dried compressed biomass powder includes adapting the molding step such that the density of the molded biomass product is controlled, and optionally, adapting the molding step such that the density of the molded biomass product is controlled includes controlling the compression ratio of the mold used in the molding step.

[0030] Typically, an additive is added to the dried compressed biomass powder before step (v) of molding the dried compressed biomass powder. Preferably, the additive increases the yield of the molded biomass product.

[0031] Typically, step (vi) of heating the molded biomass product is performed for a period of 0.4 to 2.5 hours, and / or step (vi) of heating the molded biomass product includes heating the molded biomass product to a temperature of 180°C to 350°C, optionally 210°C to 280°C.

[0032] Preferably, step (vi) of heating the molded biomass product includes heating the molded biomass product under conditions for inducing roasting of the molded biomass product.

[0033] Preferably, step (vi) of heating the shaped biomass product is adapted such that the uniformity of the solid biomass fuel is controlled, and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes performing step (vi) in an apparatus that rotates while heating the shaped biomass product, and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes controlling the speed or direction of rotation of the shaped biomass product, and optionally, rotating the shaped biomass product in both counterclockwise and clockwise directions in the apparatus.

[0034] Typically, this method further includes a step of cooling the solid biomass fuel after step (vi) of heating and before step (vii) of removing dust particles from the solid biomass fuel.

[0035] Typically, step (vii) of removing dust particles from the solid biomass fuel includes removing dust particles from the solid biomass fuel using a screen. Preferably, the screen has a void size of 3 mm to 8 mm, and preferably, the screen has a void size of 4 mm to 6 mm.

[0036] Typically, the bulk density of the solid biomass fuel determined by DIN EN 15103 is 0.58 kg / l to 0.8 kg / l, preferably 0.6 kg / l to 0.75 kg / l, and most preferably 0.60 to 0.70 kg / l.

[0037] Typically, the mechanical durability of the solid biomass fuel determined by DIN EN 15210-1 is 95% or more, 96% or more, 97% or more, or 98% or more.

[0038] In some embodiments of this method, one or more biomass sources and the solid biomass fuel are as follows: (i) One or more biomass sources include, or consist essentially of, Gramineae plants such as plants of the genus Pennisetum, for example Pennisetum cinese Roxb, and the solid biomass fuel has a bulk density of 0.60 kg / L to 0.65 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more. (ii) One or more biomass sources include a mixture of rice husks and yam, and the solid biomass fuel has a bulk density of 0.58 kg / L to 0.63 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more. (iii) One or more biomass sources include a mixture of straw and yam, and the solid biomass fuel has a bulk density of 0.60 kg / L to 0.64 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more. (iv) One or more biomass sources include a mixture of corn cobs and yam, and the solid biomass fuel has a bulk density of 0.62 kg / L to 0.66 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more. The bulk density is determined according to DIN EN 15103, and the mechanical durability is determined according to DIN EN 15210-1.

[0039] Typically, the total dry sulfur content of the biomass solid fuel is 0.15 wt% or less, preferably 0.12 wt% or less, and most preferably 0.10 wt% or less, and the total dry sulfur content is determined according to DIN EN 15289.

[0040] Typically, the total dry hydrogen content of the biomass solid fuel is 5 wt% or more, preferably 5 wt% to 10 wt%, more preferably 5 wt% to 7 wt%, and the total dry hydrogen content is determined according to DIN EN 15104.

[0041] Typically, the total dry oxygen content of the biomass solid fuel is 36 wt% or more, preferably 38 wt% to 42 wt%, more preferably 38 wt% to 40 wt%, and the total dry oxygen content is determined according to DIN EN 15296.

[0042] Typically, the total dry carbon content of the biomass solid fuel is 36 wt% or more, preferably 38 wt% to 48 wt%, more preferably 39 wt% to 45 wt%, and the total dry carbon content is determined by DIN EN 15104.

[0043] Typically, the total dry nitrogen content of the biomass solid fuel is less than 0.8 wt%, preferably less than 0.7 wt%, more preferably less than 0.6 wt%, and the total dry nitrogen content is determined by DIN EN 15104.

[0044] Typically, the solid biomass fuel has a water resistance of up to 20 days, preferably up to 30 days, more preferably up to 40 days.

[0045] Typically, the chemical oxygen demand (COD) of the solid biomass fuel, when immersed in water, is 5000 ppm or less, preferably 4000 ppm or less, most preferably 3000 ppm or less, and the chemical oxygen demand is determined by GB / 11914-89.

[0046] Typically, the fixed carbon content of the solid biomass fuel is 25 wt% or more, preferably 28 wt% to 35 wt%, more preferably 30 wt% to 33 wt%, and the fixed carbon content is determined by DIN EN 51734.

[0047] Typically, the ash content of the solid biomass fuel is less than 20 wt%, preferably less than 18 wt%, most preferably less than 16 wt%, and the ash content is determined by EN 14775 at 550 °C.

[0048] Typically, the volatile matter content of the solid biomass fuel is 42 wt% to 70 wt%, more preferably 48 wt% to 75 wt%, and the volatile matter content is determined by DIN EN 15148.

[0049] Typically, solid biomass fuel has a moisture content of less than 8% by weight, preferably less than 7% by weight, and most preferably less than 6% by weight, and the moisture content is determined according to DIN EN 14774.

[0050] Typically, biomass solid fuel has a calorific value of 4300 kcal / kg to 6500 kcal / kg, and the calorific value is determined according to DIN EN 14918.

[0051] Typically, the bulk density of the formed biomass product is A, and the bulk density of the biomass solid fuel is B, and B / A is 0.55 to 1, and the bulk density is determined according to DIN EN 15103.

[0052] Typically, the material derived from biomass is present in the solid biomass fuel in an amount of at least 95% by weight of the total fuel content of the solid biomass fuel.

[0053] According to a second aspect of the present invention, there is provided a solid biomass fuel obtainable or obtained by a method according to any of the preceding claims.

[0054] According to a third aspect of the present invention, there is provided a solid biomass fuel derived from one or more biomass sources, wherein the one or more biomass sources are (i) plants of the genus Pennisetum, such as Pennisetum cinese Roxb, comprising, consisting of, or consisting essentially of these, (ii) a mixture of rice husk and yam, comprising, consisting of, or consisting essentially of the mixture, (iii) a mixture of straw and yam, comprising, consisting of, or consisting essentially of the mixture, (iv) a mixture of corn cobs and yam, comprising, consisting of, or consisting essentially of the mixture, (v) a mixture of Pennisetum cinese Roxb and rice husk, comprising, consisting of, or consisting essentially of the mixture, (vi) A solid biomass fuel is provided that comprises, consists of, or consists essentially of a mixture containing a plant of the genus Pennisetum, such as a mixture of Pennisetum cinese Roxb and straw, or (vii) A solid biomass fuel is provided that comprises, consists of, or consists essentially of a mixture containing a plant of the genus Pennisetum, such as a mixture of Pennisetum cinese Roxb and corn cob, A solid biomass fuel is provided.

[0055] Typically, the one or more biomass sources include a grass, rice husk, yam, straw, corn cob, or any combination thereof. In embodiments, the one or more biomass sources include agricultural waste.

[0056] Typically, the one or more biomass sources include a grass in an amount of 20 wt% to 80 wt% and one or more of rice husk, yam, straw, corn cob, or any combination thereof.

[0057] Preferably, the one or more biomass sources include a grass. More preferably, the one or more biomass sources include a plant of the genus Pennisetum. Most preferably, the one or more biomass sources include Pennisetum cinese Roxb.

[0058] In certain embodiments, the one or more biomass sources comprise, consist of, or consist essentially of (i) a grass such as a plant of the genus Pennisetum, such as Pennisetum cinese Roxb, (ii) a mixture of rice husk and yam, (iii) a mixture of straw and yam, and (iv) a mixture of corn cob and yam.

[0059] Typically, the moisture content of the one or more biomass sources is 30 wt% to 50 wt%.

[0060] Typically, the bulk density of solid biomass fuel determined by DIN EN 15103 is 0.58 kg / l to 0.8 kg / l, preferably 0.6 kg / l to 0.75 kg / l, and most preferably 0.60 to 0.70 kg / l.

[0061] Typically, the mechanical durability of solid biomass fuel determined by DIN EN 15210-1 is 95% or more, 96% or more, 97% or more, or 98% or more.

[0062] In some embodiments of this method, one or more biomass sources and solid biomass fuel are as follows: (i) One or more biomass sources include, or consist essentially of, Gramineae plants such as plants of the genus Pennisetum, for example Pennisetum cinese Roxb, and the solid biomass fuel has a bulk density of 0.60 kg / L to 0.65 kg / L and the mechanical durability of the solid biomass fuel is 95% or more. (ii) One or more biomass sources include a mixture of rice husks and yam, and the solid biomass fuel has a bulk density of 0.58 kg / L to 0.63 kg / L and the mechanical durability of the solid biomass fuel is 95% or more. (iii) One or more biomass sources include a mixture of straw and yam, and the solid biomass fuel has a bulk density of 0.60 kg / L to 0.64 kg / L and the mechanical durability of the solid biomass fuel is 95% or more. (iv) One or more biomass sources include a mixture of corn cobs and yam, and the solid biomass fuel has a bulk density of 0.62 kg / L to 0.66 kg / L and the mechanical durability of the solid biomass fuel is 95% or more. The bulk density is determined by DIN EN 15103, and the mechanical durability is determined by DIN EN 15210-1.

[0063] Typically, the total dry sulfur content of the biomass solid fuel is 0.15 wt% or less, preferably 0.12 wt% or less, and most preferably 0.10 wt% or less, and the total dry sulfur content is determined by DIN EN 15289.

[0064] Typically, the total dry hydrogen content of the biomass solid fuel is 5 wt% or more, preferably 5 wt% to 10 wt%, more preferably 5 wt% to 7 wt%, and the total dry hydrogen content is determined by DIN EN 15104.

[0065] Typically, the total dry oxygen content of the biomass solid fuel is 36 wt% or more, preferably 38 wt% to 42 wt%, more preferably 38 wt% to 40 wt%, and the total dry oxygen content is determined by DIN EN 15296.

[0066] Typically, the total dry carbon content of the biomass solid fuel is 36 wt% or more, preferably 38 wt% to 48 wt%, more preferably 39 wt% to 45 wt%, and the total dry carbon content is determined by DIN EN 15104.

[0067] Typically, the total dry nitrogen content of the biomass solid fuel is less than 0.8 wt%, preferably less than 0.7 wt%, more preferably less than 0.6 wt%, and the total dry nitrogen content is determined by DIN EN 15104.

[0068] Typically, the solid biomass fuel has a water resistance of up to 20 days, preferably up to 30 days, more preferably up to 40 days.

[0069] Typically, the chemical oxygen demand (COD) of the solid biomass fuel, when immersed in water, is 5000 ppm or less, preferably 4000 ppm or less, and most preferably 3000 ppm or less, and the chemical oxygen demand is determined by GB / 11914-89.

[0070] Typically, the fixed carbon content of the solid biomass fuel is 25% by weight or more, preferably 28% to 35% by weight, more preferably 30% to 33% by weight, and the fixed carbon content is determined by DIN EN 51734.

[0071] Typically, the ash content of the solid biomass fuel is less than 20% by weight, preferably less than 18% by weight, most preferably less than 16% by weight, and the ash content is determined by EN 14775 at 550 °C.

[0072] Typically, the volatile matter content of the solid biomass fuel is 42% to 70% by weight, more preferably 48% to 75% by weight, and the volatile matter content is determined by DIN EN 15148.

[0073] Typically, the solid biomass fuel has a moisture content of less than 8% by weight, preferably less than 7% by weight, most preferably less than 6% by weight, and the moisture content is determined by DIN EN 14774.

[0074] Typically, the biomass solid fuel has a calorific value of 4300 kcal / kg to 6500 kcal / kg, and the calorific value is determined in accordance with DIN EN 14918.

[0075] Typically, the bulk density of the formed biomass product is A, and the bulk density of the biomass solid fuel is B, and B / A is 0.55 to 1, and the bulk density is determined in accordance with DIN EN 15103.

[0076] Typically, the material derived from biomass is present in the solid biomass fuel in an amount of at least 95% by weight of the total fuel content of the solid biomass fuel.

[0077] According to a fourth aspect of the present invention, there is provided a combustion method including the step of burning the solid biomass fuel according to the second and third aspects of the present invention so as to generate energy.

[0078] In one embodiment, solid biomass fuel is co-fired and combusted with fossil fuel. Preferably, the fossil fuel includes coal.

[0079] In one embodiment, the PM1.0 emission of the method is less than 175 mg / kg, preferably less than 150 mg / kg.

[0080] According to a fifth aspect of the present invention, there is provided the use of the solid biomass fuel according to the second and third aspects of the present invention as fuel in a combustion method.

[0081] Preferably, the combustion method includes the step of co-firing solid biomass fuel with fossil fuel. Preferably, the fossil fuel is coal.

[0082] In one embodiment, the PM1.0 emission of the method is less than 175 mg / kg, preferably less than 150 mg / kg.

[0083] According to a sixth aspect of the present invention, there is provided the use of one or more biomass sources for producing solid biomass fuel, wherein the one or more biomass sources are (i) plants of the genus Pennisetum, such as Pennisetum cinese Roxb, comprising, consisting of, or consisting essentially of these, (ii) a mixture of rice husk and yam, comprising, consisting of, or consisting essentially of the mixture, (iii) a mixture of straw and yam, comprising, consisting of, or consisting essentially of the mixture, (iv) a mixture of corn cob and yam, comprising, consisting of, or consisting essentially of the mixture, (v) a mixture of plants of the genus Pennisetum, such as Pennisetum cinese Roxb and rice husk, comprising, consisting of, or consisting essentially of the mixture, (vi) a mixture of plants of the genus Pennisetum, such as Pennisetum cinese Roxb and straw, comprising, consisting of, or consisting essentially of the mixture, or (vii) a mixture of plants of the genus Pennisetum, such as Pennisetum cinese Roxb and corn cob, comprising, consisting of, or consisting essentially of the mixture.

[0084] Preferably, the one or more biomass sources are as described above according to the first and third aspects of the present invention.

[0085] Preferably, the use includes using the one or more biomass sources in the method according to the first aspect of the present invention.

[0086] Preferably, the solid biomass fuel is as described above according to the first and third aspects of the present invention.

[0087] According to a seventh aspect of the present invention, there is provided a pretreatment method for pretreating one or more biomass sources for use in the production of solid biomass fuel, (i) preparing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight; (ii) pulverizing the one or more biomass sources to provide a pulverized biomass powder having an average particle diameter (D50) of 1000 μm to 20,000 μm; (iii) compressing the pulverized biomass powder to provide a compressed biomass powder having a moisture content of less than 30% by weight; and (iv) drying the compressed biomass powder to provide a dried compressed biomass powder The pretreatment method including is provided.

[0088] Typically, step (i) of preparing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight includes (a) compressing one or more biomass sources so as to have a moisture content of less than 50% by weight and / or (b) comminuting one or more biomass sources so as to have an average particle diameter (D50) of 30,000 μm to 60,000 μm. Preferably, this method includes both step (a) and step (b). More preferably, this method includes step (a) of compressing one or more biomass sources before step (b) of comminuting one or more biomass sources.

[0089] Typically, the moisture content of one or more biomass sources is 30% to 50% by weight.

[0090] Typically, step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder includes drying the compressed biomass powder so that the dried compressed biomass powder has a moisture content of 10% to 18% by weight, preferably 12% to 15% by weight.

[0091] Typically, step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder further includes mixing the compressed biomass powder particles while drying.

[0092] Typically, one or more biomass sources are as discussed above according to the first and third aspects of the present invention.

[0093] Typically, the pretreatment method is performed before the method of producing a solid biomass fuel, and the method of producing a solid biomass fuel includes a step of molding or heating the dried compressed biomass powder. Preferably, the method of producing a solid biomass fuel is as discussed above according to the first aspect of the present invention.

[0094] According to an eighth aspect of the present invention, there is provided a post-treatment method for post-treating a solid biomass fuel, the post-treatment method including a step of removing dust particles from the solid biomass fuel.

[0095] Preferably, the step of removing dust particles from the solid biomass fuel includes removing dust particles from the solid biomass fuel using a screen. More preferably, the screen has a void size of 3 mm to 8 mm, and preferably, the screen has a void size of 4 mm to 6 mm.

[0096] Typically, the step of removing dust particles from the solid biomass fuel includes subjecting the solid biomass fuel to vibration, rotation, rolling, or any combination thereof.

[0097] Preferably, the post-treatment method is performed after a method for generating the solid biomass fuel from one or more biomass sources, and the method for generating the solid biomass fuel includes a step of molding or heating. More preferably, the method for generating the solid biomass fuel is as discussed above according to the first aspect of the present invention.

[0098] Preferably, the solid biomass fuel is as discussed above according to the second and third aspects of the present invention.

Brief Description of the Drawings

[0099] Here, the present invention will be described with reference to the accompanying drawings by way of example.

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Figure 26

Mode for Carrying Out the Invention

[0100] Biomass source One or more sources of biomass used in accordance with the present invention may be any of those discussed above. Typically, one or more sources of biomass include agricultural waste. As used herein, the term "agricultural waste" typically refers to plant-based waste products generated as by-products of agricultural operations. For example, agricultural waste may include plant-based products left over after harvesting, or unwanted components of harvested plant-based products. One or more sources of biomass preferably include gramineous plants. Gramineous plants can be agricultural waste generated as by-products of agricultural operations, or excess gramineous plants left over after growing for a specific purpose. Alternatively, gramineous plants may be grown and harvested specifically for use as a source of biomass, particularly for solid biomass fuel. Alternatively, gramineous plants may be naturally occurring gramineous plants.

[0101] A preferred form of gramineous plant for use in accordance with the present invention is a plant of the genus Pennisetum. Pennisetum is a widespread genus of gramineous plants that grows naturally in the tropical and temperate regions of the world. A preferred plant of the genus Pennisetum for use in accordance with the present invention is the plant Pennisetum cinese Roxb. A photograph of the plant Pennisetum cinese Roxb is shown in FIG. 1.

[0102] Other sources of biomass that can be used in accordance with the present invention include rice husks, yams, straw, and corn cobs. These sources of biomass can be produced as agricultural waste, as by-products of agricultural operations. Alternatively, these sources of biomass may be grown specifically for the purpose of serving as feedstock for the preparation of biomass solid fuel. Corn cobs are a specific example of a material that can be produced as agricultural waste. For example, corn may be grown and harvested for human consumption. When processing corn plants for human consumption, the process may involve removing the edible corn from the inedible corn cobs. Thus, corn cobs are agricultural waste products. In some embodiments, one or more sources of biomass include, consist of, or consist essentially of rice husks, yams, straw, corn cobs, or any combination thereof. For example, one or more sources of biomass may include, consist of, or consist essentially of rice husks and yams, straw and yams, or corn cobs and yams.

[0103] If one or more sources of biomass include a grass and one or more additional sources of biomass, the one or more sources of biomass can contain any particular amount of grass, such as from 5 wt% to 95 wt%. Typically, when one or more sources of biomass include a grass and one or more additional sources of biomass, the grass is present in an amount from 10 wt% to 90 wt%, 20 wt% to 80 wt%, 30 wt% to 70 wt%, or 40 wt% to 60 wt% of the total amount of the one or more sources of biomass.

[0104] In certain embodiments, one or more sources of biomass include, consist of, or consist essentially of from 20 wt% to 80 wt% of a grass, such as a grass of the genus Pennisetum, such as Pennisetum cinese Roxb, and from 20 wt% to 80 wt% of straw, corn cobs, rice husks, or any combination thereof.

[0105] Each of the one or more biomass sources discussed above can be obtained or harvested by conventional methods known in the art.

[0106] As used herein, the term "comprising" is used to mean that any additional unspecified components may be present. As used herein, the term "consisting" is used to mean that no additional components other than those specifically recited may be present. As used herein, the term "consisting essentially of" is used to mean that additional unspecified components may be present, but these components do not substantially affect the essential characteristics of the composition.

[0107] As discussed above, the one or more biomass sources used in the present invention can be grown and harvested on a commercial scale and have been found to provide an increase in the quality and control of specific characteristics of the biomass source compared to materials used in the prior art. The use of said materials also avoids environmental damage associated with the use of trees, such as the necessary logging. The above advantages are particularly relevant to the use of grasses, yams, corn cobs, and rice husks, and in particular to grasses of the genus Pennisetum, such as Pennisetum cinese Roxb.

[0108] Surprisingly, it has also been found that the use of the one or more biomass sources used in the present invention is easier to pulverize than the previously used materials such as wood. This reduces the cost of the pulverization process. In particular, grasses do not need to be pulverized to the same extent as previously used materials such as wood.

[0109] The use of the materials of the present invention also provides a mix of more homogeneous particle sizes when pulverized, as compared to the materials previously used. Without being limited by theory, it is believed that this confers advantageous properties on the final solid fuel product, such as higher uniformity and continuity of the biomass fuel product. This is desirable in combustion methods for a number of reasons.

[0110] The inventors of the present invention recognize that the use of Gramineae plants is particularly useful as a source of biomass. In particular, Gramineae plants of the genus Pennisetum, such as Pennisetum cinese Roxb, are particularly useful. Pennisetum cinese Roxb has been found to be a fast-growing, high-yielding hybrid Gramineae plant. It is not genetically modified and, when grown, poses no ecological risk to the surrounding environment. Since it can grow under a variety of soil conditions, it will not compete with food crops for available land. Furthermore, Pennisetum cinese Roxb is a short-term, fast-growing crop that can be harvested in the first year after planting. In contrast, other crops, such as switchgrass, bamboo, and various other crops, have low yields and cannot be harvested until 2, 3, or 4 years after planting. Pennisetum cinese Roxb has been found to be harvestable for biogas production 40 days after planting once it has grown to a height of 1 meter, and then can be harvested again every 25 - 30 days. For the production of biomass pellets and other forms of solid fuel, for example in the method of the present invention, Pennisetum cinese Roxb has been found to be harvestable 195 days after planting once it has grown to a height of 4 meters, and then can be harvested again every 120 days. Thus, the high growth rate of this plant provides a continuously growing source of biomass.

[0111] Despite the advantages described above in relation to the use of gramineous plants such as Pennisetum cinese Roxb and other biomass sources described above, the inventors recognize that problems associated with the use of such biomass sources lie in that they typically contain very large amounts of moisture. For example, typically, the moisture content of freshly harvested Pennisetum cinese Roxb is over 70% by weight when harvested in autumn or winter. As a biomass source for direct use in a molding or roasting process for producing solid biomass fuel, this moisture content is too high. Therefore, it is necessary to reduce the moisture content of the biomass source before such steps. Conventional drying processes may be used. However, a drawback associated with conventional drying processes, such as drying in sunlight, is that the process takes a long time. Furthermore, due to weather uncertainties, the ideal drying time may vary and be difficult to predict. When left in sunlight for a long time to dry, the biomass source may rot, which may affect the quality of the final product when the biomass source is converted into solid fuel. More technically advanced drying methods may be used, but the process is typically costly and reduces the economic viability of the overall process.

[0112] Therefore, the inventors recognize that there is a need in the art for a method of producing solid biomass fuel using materials such as those discussed above, which preferably and economically reduces the moisture content of the biomass source before steps such as heating and molding steps that convert the biomass source into solid biomass fuel. In other words, the inventors recognize that there is a need in the art for a method of pretreating one or more biomass sources such that the moisture content of the biomass is reduced before converting the biomass source into biomass solid fuel. The above need is provided by the method of the present invention.

[0113] Preparation of one or more biomass sources As discussed above, the method of the present invention includes the step of providing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight.

[0114] One or more of the biomass sources may be sized by standard techniques known in the art. The biomass may be sized to have an average particle diameter (D50) of 30,000 μm to 60,000 μm, for example, an average particle diameter of 40,000 μm to 50,000 μm.

[0115] Typically, one or more biomass sources are prepared as particles having a size in the above range by introducing them into a conventional chipping device, although this will of course depend on the particular biomass source. For example, if the biomass source occurs naturally and the particles have a size in the above range, chipping will not be necessary. In the case of Pennisetum cinese Roxb, this plant may be supplied to a conventional chipping device known in the art to reduce the plant to particles of the size discussed above. Thus, in some embodiments, the method of the present invention may include the step of comminuting one or more biomass sources to have an average particle diameter (D50) of 30,000 μm to 60,000 μm.

[0116] The step of providing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight may also include the step of compressing the one or more biomass sources. This compression step typically squeezes moisture from the one or more biomass sources such that the moisture content of the one or more biomass sources is reduced to less than 50% by weight. Thus, in a preferred embodiment, the step of providing biomass having the particle size discussed above includes the step of compressing one or more biomass sources having a moisture content of more than 70% by weight such that after compression, the moisture content of the one or more biomass sources is less than 50% by weight.

[0117] In a preferred embodiment, once chipped and / or compressed, the one or more biomass sources may contain 30% to 50% by weight moisture, such as 30% to 40% by weight, or 40% to 50% by weight, or 30% to 45% by weight.

[0118] In a preferred embodiment, the step of providing biomass having the particle size discussed above includes both the step of compressing the biomass and the step of chipping the biomass.

[0119] The steps of chipping and compressing may be performed using separate devices. Alternatively, these steps may be performed in a single device configured for both chipping and compressing biomass. For example, a rolling device with a motor suitable for compressing biomass may be installed on a conveyor belt that supplies a conventional chipping device. In this regard, the biomass source is compressed before entering the chipper. Devices suitable for performing the steps of compressing and chipping one or more biomass sources are known in the art. An example of a device used for chipping is shown in FIG. 23. Chipping devices such as those shown in FIG. 23 typically operate on the principle that the material enters the chipper through a conveying system such as a conveyor belt that supplies the material through a supply port. The material is then cut into chips by a high-speed rotating blade (not shown) and a blade (not shown) attached to the base of the machine. The functions of the mechanism and similar chipping mechanisms are known to those skilled in the art.

[0120] An example of a device used for the compressing step is shown in FIG. 24.

[0121] As discussed above, in some embodiments, a rolling device such as that shown in FIG. 24 may be installed on a conveyor belt to compress the source material, and then the source material may be fed into a chipping device such as that shown in FIG. 23.

[0122] Micronization of Biomass Step (ii) includes micronizing one or more biomass sources to provide a micronized biomass powder having an average particle diameter (D50) of 1000 μm to 20,000 μm.

[0123] The biomass source can be pulverized into biomass powder by standard techniques known in the art. The biomass source can be pulverized such that the biomass powder has an average particle diameter (D50) of 1000 μm to 20,000 μm. Typically, one or more biomass sources are pulverized to have an average particle diameter of 1000 μm to 18,000 μm, 1000 μm to 15,000 μm, 1000 μm to 10,000 μm, or 1,000 to 5000 μm. Alternatively, the biomass can be pulverized to have an average particle diameter of 10,000 μm to 20,000 μm, 10,000 μm to 18,000 μm, or 10,000 μm to 15,000 μm. As discussed above, by pulverizing a specific biomass source for use in the present invention, a biomass powder is provided that has a smaller and advantageous particle size distribution than that provided by pulverizing previously known biomass sources. This is particularly true for gramineous plants such as Pennisetum cinese Roxb.

[0124] Compression of Biomass Powder Step (iii) includes compressing the pulverized biomass powder to provide a compressed biomass powder having a moisture content of less than 30% by weight.

[0125] This compression step may involve compressing the biomass powder using a suitable device known in the art. An example of such a device is shown in FIG. 25. Such a device operates by compressing the biomass powder with a hydraulic compression device. The material can be inserted into the perforated container shown in FIG. 25. The material may then be subjected to hydraulic compression by the hydraulic compression device, and water exits the perforated container through the holes in the mesh.

[0126] Another device that can be used to compress the biomass powder is the device shown in FIG. 26, which is a screw hydraulic press. The material to be compressed is introduced into a spiral extrusion container. The moisture exiting the material is squeezed through a screen mesh by the rotation of a motor-driven spiral screw.

[0127] As discussed above, it has been found that by performing a compression step after micronizing the biomass, a compressed biomass powder having an even lower moisture content is provided. Typically, the moisture content of the compressed biomass powder is less than 30% by weight, for example less than 25% by weight, or less than 20% by weight. Reducing the moisture of the biomass during the compression step is important because the biomass has a lower moisture content at the start of the subsequent drying step. In this way, the drying step is accelerated because less moisture needs to be removed from the biomass.

[0128] By chipping and compressing the biomass to have a particle size of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight, then micronizing the biomass to form a biomass powder, and then compressing the biomass powder again to form a compressed biomass powder having a moisture content of less than 30% by weight, it has been found to be a more efficient and economical way to reduce the moisture content of the biomass than performing the steps in a different order or removing any of the steps. For example, it has been found that by chipping the biomass and compressing it to less than 50% by weight moisture before micronization, a more effective micronization step results. Similarly, by performing these steps before the subsequent compression step, the biomass powder is compressed to an even lower moisture content than can be obtained by performing the steps of this method in a different order or omitting any particular step. As a result, these combined steps provide a compressed biomass powder product having a low level of moisture for the drying step, improving the efficiency and economy of the drying method.

[0129] Drying of the Compressed Biomass Powder In step (iv) of this method, the biomass is dried. The step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder includes drying the compressed biomass powder such that the dried compressed biomass powder has a moisture content of 10% to 18% by weight, preferably 12% to 15% by weight.

[0130] The step of drying the biomass powder may also include mixing the compressed biomass powder with one or more additional biomass sources. For example, if one or more biomass sources include at least two biomass sources, two or more biomass sources can be mixed during any step of the method of the present invention, but preferably, one or more biomass sources are mixed during the drying step of the method of the present invention. In some embodiments, the compressed biomass powder is mixed with an additional biomass source that is also a compressed biomass powder prepared using the steps of the method described herein. In other embodiments, one or more additional biomass sources are not processed as described herein. For example, the compressed biomass powder prepared as described herein may be mixed with one or more additional biomass sources prepared by different methods, such as micronizing without compressing, or methods that are not any of these steps.

[0131] The compressed biomass powder may be dried using any suitable method, such as using a standard drying cylinder known in the art. Preferably, the drying step is carried out in a drying device including a rotary drying drum. The rotation of the rotary drying drum can be used to mix the compressed biomass powder with one or more additional biomass sources described above. Preferably, the rotary drying drum includes lifting plates. The lifting plates continuously lift the material while rotating the drying cylinder. Surprisingly, the inventors of the present invention have found that the mixing of one or more biomass powders is improved by using a rotary drying cylinder having lifting plates to dry one or more biomass powders together with additional materials or to mix two or more biomass powders.

[0132] Molding of the dried compressed biomass powder The dried compressed biomass powder is molded to provide a molded biomass product. The molding step may be carried out according to any biomass molding technique known in the art in any molding device known in the art and may include an extrusion molding system. Preferably, the molding step is carried out in a compression mold. Preferably, the compression mold includes a molded article escape hole. The molding step may be carried out using the apparatus described in Chinese Patent No. 105435708.

[0133] Preferably, the molding step includes molding the dried compressed biomass powder into pellets. Thus, in a preferred embodiment, the molded biomass product and the solid biomass fuel product constitute biomass pellets.

[0134] Although it is known to form biomass powder to produce a formed biomass product, the inventors of the present invention have surprisingly found that by adapting the forming step such that the density of the formed biomass product generated from the step is controlled within a certain range, certain advantageous properties are imparted to the final solid biomass fuel product. In particular, it has been found that by controlling the forming step such that the density of the formed biomass product is in the range of 1.0 to 1.2 kg / L, advantageous properties are imparted to the final biomass fuel product. Preferably, the forming step is controlled such that the density of the formed biomass product is in the range of 1.0 kg / L to 1.2 kg / L.

[0135] The forming step can be controlled in various ways. When the forming process involves the use of a compression mold, the density is controlled by using a compression ratio of 3.8 to 6.5. Typically, the smaller the compression ratio, the lower the density of the formed biomass product. However, the larger the compression ratio, the lower the yield of the formed biomass product.

[0136] The compression ratio for a compression mold having a formed product escape hole can be defined as the ratio of the length to the diameter of the formed product escape hole.

[0137] Figure 2 shows an example of a compression mold that can be used according to the present invention. After inserting the dry compressed biomass product into the inside of the mold, it is pushed out from the inside of the mold by pressure so as to exit through the formed product escape hole in the figure. The pressure ratio is shown in the figure as the ratio of the length to the diameter of the formed product escape hole.

[0138] In the method of the present invention, preferably, step (v) of forming the dry compressed biomass powder includes adapting the forming step such that the density of the formed biomass product is controlled within the range of 1.1 kg / L to 1.2 kg / L. Preferably, a compression mold is used and the density is controlled by controlling the compression ratio of the compression mold. More preferably, the compression ratio is 3.8 to 6.5.

[0139] By controlling the density of the molded biomass product during the molding step, surprisingly, it has been found that an increase in water resistance is provided to the final biomass fuel product. Preferably, the solid biomass fuel product produced from the molded biomass product having a density in the range of 1.1 kg / L to 1.2 kg / L is sufficiently water-resistant for up to 20 days, preferably up to 30 days.

[0140] Preferably, before step (v) of molding the dry compressed biomass powder, an additive is added to the dry compressed biomass powder. The additive is considered to improve the molding process and increase the yield of the molded biomass product produced from the molding step. Suitable additives are known in the art and include, but are not limited to, starch or starch derivatives.

[0141] Figure 3 is a graph showing the productivity on the Y-axis with respect to the compression ratio on the X-axis for the molded biomass product produced according to the method of the present invention. The biomass source here consists of Pennisetum cinese Roxb.

[0142] Figure 4 shows the difference in yield after the molding step when an additive is included compared to when no additive is included during the molding step, and the supply source of one or more biomasses consists of Pennisetum cinese Roxb. It can be seen that a higher yield is obtained when an additive is added to the dry compressed biomass before molding.

[0143] Figure 5 is a graph showing the density on the Y-axis (kg / L) with respect to the compression ratio on the X-axis for the molded biomass product produced according to the method of the present invention, and the biomass source consists of Pennisetum cinese Roxb.

[0144] Typically, in addition to additives such as those discussed above, no other fuel sources are added to the dry-compressed biomass powder during the forming step. Thus, the formed biomass product of the forming step contains only materials derived from biomass as fuel sources in the solid biomass fuel. For example, when forming dry-compressed biomass powder into pellets, typically no other fuel sources are added to the dry-compressed biomass product before forming so that the solid biomass fuel pellets produced at the end of this process contain only fuel sources derived from biomass. Thus, in a preferred embodiment, the solid biomass fuel comprises at least 50% by weight of the total fuel content of the fuel, such as at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, preferably at least 95% by weight of materials derived from biomass.

[0145] When the term total fuel content of the solid fuel is used herein, it is intended to refer to the components of the solid fuel that are combustible materials such as biomass-derived materials and coal. The term fuel content with respect to the solid fuel is not intended to include additives that may be present in the solid fuel pellet and that do not produce energy by their own combustion.

[0146] The forming step has also been found to enhance the water resistance properties of the final biomass solid fuel product. The increase in density that occurs during the forming step means that water penetrates less easily into the higher density formed biomass product particles.

[0147] Furthermore, as the product densifies, more biomass is concentrated inside the formed product and is no longer in direct contact with water.

[0148] Heating of the formed biomass product Heat the shaped biomass product so that solid biomass fuel is produced. The heating is performed at a temperature of 160°C to 420°C for a period of 0.25 to 5 hours. Preferably, the step of heating the shaped biomass product is performed for a period of 0.4 to 2 hours. Preferably, the step of heating the shaped biomass product includes heating the shaped biomass product to a temperature of 180°C to 350°C, more preferably 210°C to 280°C.

[0149] Preferably, step (vi) of heating the shaped biomass product includes heating the shaped biomass product under conditions for inducing roasting of the shaped biomass product. Roasting is a gentle pyrolysis process in which heating is performed in a low-oxygen atmosphere, such as an atmosphere with an oxygen content of less than 10%. Suitable conditions and processes for roasting are known in the art. Accordingly, preferably, step (ii) of heating the shaped biomass product includes roasting.

[0150] The heating step may be performed in any device known in the art suitable for heating the shaped biomass product. For example, the heating step may be performed in the device disclosed in European Patent Application Publication No. 3287509 (A1) using the disclosed process conditions.

[0151] Preferably, step (vi) of heating the shaped biomass product is adapted such that the uniformity of the solid biomass fuel is controlled, and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes performing step (vi) in a device that rotates the shaped biomass product while heating it, and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes controlling the speed or direction of rotation of the shaped biomass product, and optionally, rotating the shaped biomass product in both counterclockwise and clockwise directions in the device. The uniformity of the solid biomass fuel is also optimized by the heating temperature and duration discussed above.

[0152] If the method of the present invention includes a step of cooling after the step of heating the biomass, the cooling step may include rotating the solid biomass fuel. The biomass may be rotated in a suitable apparatus, such as that disclosed in European Patent Application Publication No. 3287509 (A1). Preferably, both the step (vi) of heating and the step of cooling the biomass include rotating the biomass. When rotating the biomass in either the cooling step or the heating step, the biomass may be rotated in different directions, such as both clockwise and counterclockwise in a continuous cycle.

[0153] The term "uniformity" of the solid biomass product refers to a solid biomass fuel or a formed biomass product having constant or similar properties from end to end of each particle of the solid biomass fuel or formed biomass product, and from end to end of a plurality of particles within a bulk sample of the solid biomass fuel product or formed biomass product. For example, but not limited to, particle density, ease of combustion of the particle, chemical composition of the particle, and water resistance properties of the particle. Uniformity is a highly desirable property for biomass fuels for use in the combustion process.

[0154] The inventors have also found that controlling the heating step as discussed above further aids in providing a solid biomass fuel product having enhanced water resistance properties compared to prior art biomass fuels. During the heating step, hydrophilic compounds present in the biomass powder that absorb water decompose. Further, the heating step causes the oil present in the biomass powder to move to the outside of the biomass powder particles, increasing the hydrophobicity of the particles.

[0155] Removal of dust particles from solid biomass fuel The method of the present invention involves the step of removing dust particles from solid biomass fuel. The inventors of the present invention have found that in biomass solid fuel production methods known in the art, a significant amount of dust adheres to the solid biomass fuel. This dust is a problem because it can contaminate the air during the transportation and packaging of the solid biomass fuel. The dust can also contaminate the local environment. Furthermore, when stored in open air, the dust particles form white mold, which affects the performance and quality of the solid biomass fuel. Therefore, it is beneficial to remove the dust on the surface of the particles of the solid biomass fuel.

[0156] The inventors of the present invention have found that the dust on the surface of the biomass solid fuel particles can be removed by inducing friction between the particles. For example, by means such as vibrating or rotating the solid biomass fuel particles, friction can be induced to remove the dust adhering to the particles. Therefore, step (vii) of removing dust from the solid biomass particles preferably includes inducing friction between the particles of the solid biomass fuel. Preferably, step (vi) of removing dust from the solid biomass particles includes subjecting the particles to vibration, rotation, rolling, or any combination thereof.

[0157] Apparatus suitable for performing rolling, rotation, and vibration of solid biomass fuel particles are known to those skilled in the art and are shown in FIGS. 7 and 8. Step (vii) of removing dust particles from the solid biomass fuel may include removing dust particles from the solid biomass fuel using a screen. Preferably, the screen has a void size of 2 mm to 10 mm, more preferably 3 mm to 8 mm, and most preferably 4 mm to 6 mm. Dust particles mixed in the solid biomass fuel particles can be separated from the solid biomass fuel by passing through the screen. Larger solid biomass fuel particles do not pass through the screen and are thus separated from the dust particles. Apparatus and methods suitable for performing the screening step are known to those skilled in the art and any of the said suitable apparatus may be used. For example, a device using screening, rolling, and rotation of solid biomass fuel may be used to remove dust particles from the solid biomass fuel. In the use of such a device, the solid biomass fuel may be placed on the screen, and the screen may be driven by the operation of a motor to roll and rotate on the axis. During the rolling / inclination and rotation of the screen, the material on the sieve surface of the screen is turned over. Some materials pass through the screen and are separated from the materials that do not pass through the screen. By the rolling and rotation of the screen, the materials stuck in the voids of the screen fall, thereby preventing clogging of the voids of the screen. Alternatively, a device for vibrating and screening solid biomass fuel particles may be used. In this case, the screen may be vibrated using a motor, whereby the material on the screen surface is thrown up. By this process, small particles attached to large particles are released and can then pass through the voids in the screen. An example of a device that separates large particles from small particles using a screen and vibration, where the small particles may or may not be attached to the large particles, is the device taught in Chinese Utility Model Registration No. 201324717.

[0158] Accordingly, a preferred method of the present invention comprises subjecting solid biomass fuel particles to one or more of rolling, rotation, and vibration so as to induce friction between the solid biomass fuel particles, and removing dust particles adhering to the solid biomass fuel particles from the particles. This method then preferably comprises subjecting a mixture of the solid biomass fuel particles and the dust particles to the screening step discussed above to remove the dust particles from the solid biomass fuel particles. Accordingly, the removal step (vii) is an effective post-treatment for removing dust from the particles of the solid biomass fuel.

[0159] Pretreatment and post-treatment The steps (v) and (vi) discussed above of molding and heating so as to form solid biomass fuel can typically be considered the main production steps of converting one or more biomass sources into solid biomass fuel.

[0160] In contrast, the steps (i) to (iv) of preparing, pulverizing, compressing, and drying the biomass are a method of pretreating one or more biomass sources, and can be considered a method of pretreating the one or more biomass sources (in the form processed as dry-compressed biomass powder) before converting them into solid biomass fuel through the steps of molding and heating. Accordingly, the present invention provides the pretreatment method discussed above. The pretreatment method comprises the steps (i) to (iv) of preparing, pulverizing, compressing, and drying the biomass. These steps may be the same as the steps (i) to (iv) discussed above in the context of the method according to the present invention for producing solid biomass fuel.

[0161] The pretreatment method of the present invention is preferably carried out before steps (v) to (vii) discussed above, which is a method for producing solid biomass fuel. However, this is not essential, and the pretreatment method of the present invention may be carried out before any method for converting one or more biomass sources into solid biomass fuel. Preferably, the pretreatment method is carried out before a method for producing solid biomass fuel, which includes a step of molding, a step of heating, or both a step of molding and a step of heating.

[0162] As used herein, the term "pretreatment" refers to a process carried out to condition the starting material in a method for converting one or more biomass sources into solid biomass fuel. Preferably, the term "pretreatment" refers to treating the biomass source starting material before a method for converting the biomass source into solid biomass fuel, which method involves a step of molding or a step of heating.

[0163] Step (vii) discussed above, which removes dust particles from solid biomass fuel, can be considered a post-treatment step of solid biomass fuel. Therefore, the present invention provides the post-treatment method discussed above.

[0164] The post-treatment method of the present invention is preferably carried out after steps (v) to (vi) or steps (i) to (vi) discussed above, which is a method for producing solid biomass fuel. However, this is not essential, and the post-treatment method of the present invention may be carried out after any method for converting one or more biomass sources into solid biomass fuel. Preferably, the post-treatment method is carried out after a method for producing solid biomass fuel, which includes a step of molding, a step of heating, or both a step of molding and a step of heating.

[0165] As used herein, the term "post-treatment" refers to a method performed on solid biomass fuel after it has been produced from one or more biomass sources. Preferably, the term "post-treatment" refers to treating the biomass source starting material after the method of converting the biomass source into solid biomass fuel, the method involving a step of forming or heating.

[0166] Solid biomass fuel product The solid biomass fuel product may have any of the physical characteristics discussed above.

[0167] As discussed above, the biomass solid fuel of the present invention preferably includes pellets. The pellets may be of any suitable size. Preferably, the pellets have a diameter of 3 mm to 100 mm, more preferably 5 mm to 8 mm. Preferably, the pellets have a length of 20 mm to 60 mm, more preferably 30 mm to 50 mm. As discussed above, surprisingly, the solid biomass fuel product of the present invention has been found to have enhanced water resistance characteristics compared to solid biomass fuel products produced by prior art methods. This is thought to be due to the forming and / or heating steps being controlled as discussed above. The inventors have found that prior art biomass fuels are only sufficiently water resistant for up to 10 days. In contrast, the solid biomass fuel product of the present invention has been found to be sufficiently water resistant for up to 20 days, preferably 30 days, more preferably 40 days.

[0168] The water resistance characteristics of the solid biomass fuel are determined by the standard test of the Energy Research Centre of the Netherlands (ECN), described in more detail below.

[0169] The moisture content of the biomass solid fuel of the present invention can also be determined by the standard ECN test method. The moisture content of the solid biomass fuel of the present invention is typically 3 to 8 wt%, preferably 4 to 7 wt%, more preferably 4 to 6 wt%.

[0170] The solid biomass fuel of the present invention has also been found to have unexpectedly high mechanical durability. The mechanical durability is typically over 95%. This is advantageous because it has been found that biomass pellets with a mechanical durability of over 95% can be stored outdoors without damage for a period of up to two months. In contrast, biomass pellets with a mechanical durability of less than 95% are typically damaged by rainfall and cannot be stored outdoors. Thus, high mechanical durability is a further advantage of the biomass pellets of the present invention.

[0171] A further advantage associated with the high durability of the solid biomass fuel particles is that, if the pellets are broken in any way by force, they break into larger pieces than pellets with low mechanical durability. This minimizes the risk of dust explosion, if any.

[0172] As discussed above, in a preferred embodiment, typically, in addition to additives such as those discussed above, no other fuel source is added to the heated biomass product during the forming step. Thus, the solid biomass fuel typically contains only materials derived from biomass as the fuel source in the solid biomass fuel. For example, when forming the heated biomass product into pellets, typically no other fuel source is added to the heated biomass product prior to forming such that the solid biomass fuel pellets produced by the forming step contain only the fuel source derived from biomass.

[0173] Thus, in a preferred embodiment, the solid biomass fuel comprises at least 50% by weight of the total fuel content of the fuel, such as at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, preferably at least 95% by weight of materials derived from biomass. If the source of one or more biomasses consists of or consists essentially of rice husks, the biomass solid fuel comprises at least 95% by weight of the total fuel content of the fuel of materials derived from biomass.

[0174] Combustion method The products of the present invention can be used in a variety of different combustion methods. The suitability of said products for use in a particular method will be apparent to those skilled in the art. For example, the biomass fuel of the present invention may be used alone in a combustion method in a power plant or in an industrial process. Alternatively, the biomass product of the present invention may be used in a combustion method together with additional fuels such as coal in co-firing.

[0175] Advantageously, the products of the present invention have been found to provide very low PM1.0 emissions when compared to other biomass fuels known in the art. In addition, the PM1.0 emissions of this method are less than those of methods involving the combustion of coal.

[0176] Advantageously, due to the improved physical properties of the biomass fuel of the present invention, it has been found that the biomass is particularly suitable for co-firing with coal. For example, due to the improved quality and uniformity of the product, the biomass fuel of the present invention can be co-fired with coal particularly well. The improved water resistance properties of the biomass fuel of the present invention also mean that it is particularly suitable for co-firing the biomass with coal and making storage and transportation easier due to its water-resistant nature.

Examples

[0177] The method according to the present invention was carried out. The source of biomass was only Pennisetum cinese Roxb. The temperature of the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

[0178] A photograph of the solid product is shown in Figure 6.

Examples

[0179] The method according to the present invention was carried out. The biomass source was 75% by weight of Pennisetum cinese Roxb and 25% by weight of rice husks. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0180] The method according to the present invention was carried out. The biomass source was 50% by weight of Pennisetum cinese Roxb and 50% by weight of rice husks. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0181] The method according to the present invention was carried out. The biomass source was 25% by weight of Pennisetum cinese Roxb and 75% by weight of rice husks. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0182] The method according to the present invention was carried out. The biomass source was 75% by weight of Pennisetum cinese Roxb and 25% by weight of straw. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0183] The method according to the present invention was carried out. The biomass source was 50% by weight of Pennisetum cinese Roxb and 50% by weight of straw. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0184] The method according to the present invention was carried out. The biomass source was 25% by weight of Pennisetum cinese Roxb and 75% by weight of straw. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0185] The method according to the present invention was carried out. The biomass source was 75% by weight of Pennisetum cinese Roxb and 25% by weight of corn cobs. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0186] The method according to the present invention was carried out. The biomass source was 50% by weight of Pennisetum cinese Roxb and 50% by weight of corn cobs. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

Example

[0187] The method according to the present invention was carried out. The biomass source was 25% by weight of Pennisetum cinese Roxb and 75% by weight of corn cobs. The temperature in the heating step was 220°C to 280°C for a period of 0.4 to 2 hours. After the heating step, the solid biomass fuel product was cooled.

[0188] Characteristics evaluation of the solid biomass fuel produced in Examples 1 to 10 The bulk density (kg / L) of the solid biomass fuel prepared in Examples 1 to 10 was measured using DIN EN 15103 and is shown in Figure 9.

[0189] The durability of the solid biomass fuel prepared in Examples 1 to 10 was determined according to DIN EN 15210-1 and is shown in Figure 10.

[0190] The sulfur content of the solid biomass fuels prepared in Examples 1 to 10 is shown in Fig. 11. The sulfur content is determined according to DIN EN 15289.

[0191] The hydrogen content of the solid biomass fuels prepared in Examples 1 to 10 is shown in Fig. 12. The hydrogen content was determined according to DIN EN 15104.

[0192] The oxygen content of the solid biomass fuels prepared in Examples 1 to 10 is shown in Fig. 13. The oxygen content was determined according to DIN EN 15296.

[0193] The carbon content of the biomass solid fuels prepared in Examples 1 to 10 is shown in Fig. 14. The carbon content is determined according to DIN EN 15104.

[0194] The nitrogen content of the biomass solid fuels prepared in Examples 1 to 10 is shown in Fig. 15. The nitrogen content is determined according to DIN EN 15104.

[0195] The fixed carbon content of the biomass solid fuels prepared in Examples 1 to 10 is shown in Fig. 16. The fixed carbon content is determined according to DIN EN 51734.

[0196] The ash content of the biomass solid fuels prepared in Examples 1 to 10 is shown in Fig. 17. The ash content was determined at 550 °C according to DIN EN 14775.

[0197] The moisture content of the biomass solid fuels prepared in Examples 1 to 10 is shown in Fig. 18. The water content was determined according to DIN EN 14774-2.

[0198] The volatile matter content of the solid biomass fuels prepared in Examples 1 to 10 is shown in Fig. 19.

[0199] The PM1.0 emissions of the biomass solid fuels produced in Examples 1 to 10 are shown in FIG. 20. The PM1.0 emissions were determined by the standard method of the German ECN test institute.

[0200] In the above figure, the product of Example 1 is represented as A, the product of Example 2 is represented as B, the product of Example 3 is represented as C, the product of Example 4 is represented as D, the product of Example 5 is represented as E, the product of Example 6 is represented as F, the product of Example 7 is represented as G, the product of Example 8 is represented as H, the product of Example 9 is represented as I, and the product of Example 10 is represented as J.

Example

[0201] The solid biomass fuel of Example 1 was tested in an artificial climate experiment and exposed to an artificial climate chamber for 10 days. This test is an ECN standard test for evaluating the moisture content of biomass fuel particles.

[0202] The results of this test are shown in FIG. 21. The results in FIG. 21 show that for each of the biomass products A to J, the equilibrium moisture uptake of the biomass particles stabilized at about 7 to 9 wt% after exposure for about 14 days at 27 °C and 90% relative humidity. This is a low moisture content of the biomass fuel particles, indicating that the biomass particles are very hydrophobic and very water-resistant compared to biomass solid fuels known in the art.

[0203] In a second experiment in the climate chamber, the biomass solid fuel was immersed in water at a temperature of 27 °C for 15 minutes and then exposed to the climate chamber. After immersion in water, the moisture content of the sample was 90 wt%. After 10 days of exposure in the climate chamber, the moisture content of the fuel stabilized at around 7.8% - 8%. The results are shown in FIG. 22.

Claims

1. A method for producing solid biomass fuel, comprising: (i) preparing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight; (ii) pulverizing the one or more biomass sources to provide a pulverized biomass powder having an average particle diameter (D50) of 1000 μm to 20,000 μm; (iii) compressing the pulverized biomass powder to provide a compressed biomass powder having a moisture content of less than 30% by weight; (iv) drying the compressed biomass powder to provide a dried compressed biomass powder; (v) molding the dried compressed biomass powder to provide a molded biomass product; (vi) heating the molded biomass product at a temperature of 160°C to 420°C for a period of 0.25 to 5 hours to provide solid biomass fuel; and (vii) removing dust particles from the solid biomass fuel. (vii) removing dust particles from the solid biomass fuel The method as described above.

2. (i) the one or more biomass sources include agricultural waste; (ii) the one or more biomass sources include gramineous plants, rice husks, yams, straws, corn cobs, or any combination thereof; and / or (iii) the one or more biomass sources include gramineous plants in an amount of 20% to 80% by weight and one or more of rice husks, yams, straws, corn cobs, or any combination thereof. The method according to claim 1.

3. The method according to claim 1, wherein the one or more biomass sources include gramineous plants, the gramineous plants include plants of the genus Pennisetum, and optionally, the one or more biomass sources include Pennisetum cinese Roxb.

4. (a) the one or more biomass sources include, consist of, or consist essentially of (i) gramineous plants such as plants of the genus Pennisetum, e.g., Pennisetum cinese Roxb, (ii) a mixture of rice husks and yams, (iii) a mixture of straws and yams, or (iv) a mixture of corn cobs and yams; and / or (b) the moisture content of the one or more biomass sources is 30% to 50% by weight. The method according to claim 1.

5. Step (i) of preparing one or more biomass sources having an average particle diameter (D50) of 30,000 μm to 60,000 μm and a moisture content of less than 50% by weight includes (a) compressing the one or more biomass sources so as to have a moisture content of less than 50% by weight and / or (b) comminuting the one or more biomass sources so as to have an average particle diameter (D50) of 30,000 μm to 60,000 μm, the method according to claim 1.

6. Step (iv) of drying the compressed biomass powder to provide a dried compressed biomass powder includes drying the compressed biomass powder so that the dried compressed biomass powder has a moisture content of 10% to 18% by weight, the method according to claim 1.

7. Step (v) of molding the dried compressed biomass powder includes adapting the molding step so that the density of the molded biomass product is controlled, and optionally, adapting the molding step so that the density of the molded biomass product is controlled includes controlling the compression ratio of the mold used in the molding step, the method according to claim 1.

8. (a) Step (vi) of heating the molded biomass product is carried out for a period of 0.4 to 2.5 hours, and step of heating the molded biomass product includes heating the molded biomass product to a temperature of 180°C to 350°C, and / or (b) after step (vi) of heating and before step (vii) of removing dust particles from the solid biomass fuel, The method according to claim 1 further includes a step of cooling the solid biomass fuel.

9. Step (vi) of heating the formed biomass product is adapted such that the uniformity of the solid biomass fuel is controlled, and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes, in an apparatus for rotating while heating the formed biomass product, performing step (vi), and optionally, adapting step (vi) such that the uniformity of the solid biomass fuel is controlled includes controlling the speed or direction of rotation of the formed biomass product, and optionally, rotating the formed biomass product in both counterclockwise and clockwise directions in the apparatus, according to the method of claim 1.

10. Step (vii) of removing dust particles from the solid biomass fuel includes removing dust particles from the solid biomass fuel using a screen, and the screen has a void size of 3 mm to 8 mm, according to the method of claim 1.

11. The bulk density of the solid biomass fuel determined by DIN EN 15103 is 0.58 kg / l to 0.8 kg / l, and / or the mechanical durability of the solid biomass fuel determined by DIN EN 15210-1 is 95% or more, according to the method of claim 1.

12. (i) One or more biomass sources include or consist essentially of gramineous plants such as plants of the genus Pennisetum, for example Pennisetum sinense Roxb, the solid biomass fuel has a bulk density of 0.60 kg / L to 0.65 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more, (ii) One or more biomass sources include a mixture of rice husks and yam, the solid biomass fuel has a bulk density of 0.58 kg / L to 0.63 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more, (iii) One or more biomass sources include a mixture of straw and yam, the solid biomass fuel has a bulk density of 0.60 kg / L to 0.64 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more, or (iv) One or more biomass sources include a mixture of corn cobs and yams, the solid biomass fuel has a bulk density of 0.62 kg / L to 0.66 kg / L, and the mechanical durability of the solid biomass fuel is 95% or more. The bulk density is determined by DIN EN 15103, and the mechanical durability is determined by DIN EN 15210-1. The method according to claim 1.

13. (i) The total dry sulfur content of the biomass solid fuel is 0.15% by weight or less, and the total dry sulfur content is determined by DIN EN 15289. (ii) The total dry hydrogen content of the biomass solid fuel is 5% by weight or more, and the total dry hydrogen content is determined by DIN EN 15104. (iii) The total dry oxygen content of the biomass solid fuel is 36% by weight or more, and the total dry oxygen content is determined by DIN EN 15296. (iv) The total dry carbon content of the biomass solid fuel is 36% by weight or more, and the total dry carbon content is determined by DIN EN 15104. (v) The total dry nitrogen content of the biomass solid fuel is less than 0.8% by weight, and the total dry nitrogen content is determined by DIN EN 15104. (vi) When the chemical oxygen demand (COD) of the solid biomass fuel is immersed in water, it is 5000 ppm or less, and the chemical oxygen demand is determined by GB / 11914-89. (vii) The fixed carbon content of the solid biomass fuel is 25% by weight or more, and the fixed carbon content is determined by DIN EN 51734. (viii) The ash content of the solid biomass fuel is less than 20% by weight, and the ash content is determined by EN 14775 at 550 °C, and / or (ix) The volatile matter content of the solid biomass fuel is 42% by weight to 70% by weight, and the volatile matter content is determined by DIN EN 15148. The method according to claim 1.

14. The solid biomass fuel has a moisture content of less than 8% by weight, and the moisture content is determined by DIN EN 14774, and / or the solid biomass fuel has a calorific value of 4300 kcal / kg to 6500 kcal / kg, and the calorific value is determined according to DIN EN 14918. The method according to claim 1.

15. The bulk density of the shaped biomass product is A, the bulk density of the biomass solid fuel is B, B / A is from 0.55 to 1, the bulk density is determined in accordance with DIN EN 15103, and / or the material derived from biomass is present in the solid biomass fuel in an amount of at least 95% by weight of the total fuel content of the solid biomass fuel, the method according to claim 1.

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