Solid biomass fuel, solid biomass charcoal and manufacturing method thereof

Abstract

To provide a solid biomass fuel obtained from discarded coffee bean outer skin (silver skin), a solid biomass charcoal further carbonized from the biomass fuel, and a manufacturing method thereof.SOLUTION: The solid biomass charcoal consists of coffee bean outer skin detached during the roasting of raw coffee beans, wherein the coffee bean outer skin is pulverized from thin skin-like state to fine powder state and then 0.1 to 3% of lignin is added, and after extrusion molding by heating and compression, it is further carbonized by high temperature heating in an oxygen-free state in a charcoal kiln.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to solid biomass fuel obtained from coffee bean husks that are normally discarded, and to solid biomass charcoal obtained by carbonizing the biomass fuel and a method for producing the same. The solid biomass charcoal can be burned as a heat source in a charcoal roaster, helping to achieve carbon neutrality. [Background technology]

[0002] In order to maintain the natural environment on Earth, it is extremely important to achieve carbon neutrality, which can prevent environmental destruction. Since coffee is a commonly consumed beverage in large quantities all over the world, it would be extremely beneficial to effectively utilize the large amount of chaff, the thin, silver skin that covers the coffee beans and is removed during roasting. If biomass fuel or biomass charcoal can be obtained from these coffee bean husks, the carbon dioxide emitted from burning them would be the same amount as the carbon dioxide absorbed by the coffee plant during its growth, and would not increase greenhouse gas emissions, making it possible to achieve carbon neutrality.

[0003] Coffee is a commonly consumed beverage all over the world, and as such, the production volume of green coffee beans is enormous. Green coffee beans are the seeds of coffee cherries harvested from coffee trees, and are in their raw state after simply being hulled and refined to remove the parchment. Normally, they are shipped as green coffee beans from the producing area, and roasted in the consuming area to become coffee beans. When green coffee beans are roasted industrially in large quantities, the thin outer skin of the coffee beans, known as silver skin, is peeled off from the green coffee beans at a roasting temperature of 140-185°C, and floats in the air with the exhaust gas.

[0004] For example, when about 25 tons of green coffee beans are roasted per day, the amount of thin-skinned coffee bean husks reaches about 200 kg, and conventionally, the coffee bean husks are often discarded without being reused. Since a large amount of thin-skinned coffee bean husks are generated daily, the cost of disposing of them is considerably high, and therefore it is desirable to reduce the disposal cost of coffee bean husks and, if possible, to effectively reuse the coffee bean husks.

[0005] As an example, in JP 2005-35401 A, in order to effectively utilize the outer skins of coffee beans, the outer skins are chopped, crushed, and extracted to produce a caffeine composition, which, when added in an appropriate amount to cosmetics or food and beverages, exerts antibacterial and antioxidant effects. This caffeine composition is blended with fats and oils, waxes, fatty acids, surfactants, alcohols, esters, etc., which are normally used in cosmetics, and is used as a cosmetic, food and beverage, pharmaceutical, or antioxidant. These products can be produced by normal methods except that they contain a predetermined amount of the caffeine composition.

[0006] If we expand this type of proposal from coffee bean husks to coffee cherries and raw coffee beans, Japanese Patent No. 3375566 relates to a method for producing porous charcoal, in which the raw natural organic materials, including wood, bamboo, and fruit shells, are compressed at high pressure to densify the tissue, and then pyrolyzed and carbonized. In addition, Japanese Patent Publication No. 2019-502013 shows a means for producing solid biofuel from coffee extract residue (WCG), making effective use of the millions of tons of coffee extract residue discharged each year when producing instant coffee. Fillers and binders are added to the coffee extract residue containing moisture, which is then pressed into pellets or briquettes, which are then burned as biofuel in a biomass boiler system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-35401 A [Patent Document 2] Patent No. 3375566 [Patent Document 3] Special table 2019-502013 publication Summary of the Invention [Problem to be solved by the invention]

[0008] In reality, when green coffee beans are roasted industrially in large quantities, thin coffee husks peel off from the green coffee beans and float in the air, so they are collected in an exhaust duct and then simply disposed of. Since a considerable amount of thin coffee bean husks are generated daily, the cost of disposing of them becomes quite high, and while there have been some proposals regarding the treatment of green coffee beans, there have been almost no proposals regarding thin coffee bean husks, and in addition, there are no proposals that are practically effective at all.

[0009] JP 2005-35401 A is not an invention related to biomass fuel, but is an additive that is added in an appropriate amount to cosmetics, food, and beverages, in which coffee bean husks are chopped, crushed, and extracted to produce a caffeine composition. Even if this caffeine composition has antibacterial and antioxidant properties, it is still unclear in what manner and to what extent these properties function, and it is necessary to consider the effects on taste and skin, and it is also impossible to ignore the presence or absence of side effects from adding it to cosmetics, food, and beverages.

[0010] On the other hand, although it is not related to the reuse of thin-skinned coffee bean husks, in Patent No. 3375566, fruit shells such as coffee cherries are compressed at high pressure and carbonized. Thin-skinned coffee bean husks are not fruit shells with hard fibrous tissue, so even if dried coffee husks are simply compressed at high pressure, the fibrous tissue cannot be densified, and this method cannot be applied to coffee husks. In addition, in JP2019-502013, when producing solid biofuel from coffee extract residue, a filler, a binder, etc. are added to the coffee extract residue containing moisture and formed into pellets, etc. This solid fuel is burned in a biomass boiler system, so its uses are limited, and while a solid object such as coffee extract residue can be formed just by pressing, coffee bean husks are dry thin skin bodies and cannot be formed into pellets, etc. just by pressing.

[0011] The present invention proposes a new mode of utilization of coffee bean husks that are normally discarded, and aims to provide a solid biomass fuel that can efficiently obtain solid fuel from thin coffee bean husks and a method for producing the same. Another aim of the present invention is to provide solid biomass charcoal that produces almost no soot during combustion by carbonizing the solid biomass fuel and is suitable as fuel for charcoal-burning roasters and a method for producing the same. [Means for solving the problem]

[0012] The solid biomass fuel according to the present invention is made from coffee bean husks that are peeled off during roasting of green coffee beans, and the coffee bean husks are pulverized from a thin skin state into a fine powder, to which 0.1 to 3% lignin is further added and extrusion molded by heating and pressurization.

[0013] Furthermore, the solid biomass charcoal according to the present invention is made from coffee bean husks that are peeled off during roasting of green coffee beans, and the coffee bean husks are pulverized from a thin skin state into a fine powder, to which 0.1 to 3% lignin is added, and the husks are extrusion-molded by heating and pressurization, and then further heated at high temperatures in an oxygen-free environment in a charcoal kiln to be carbonized.

[0014] In the present invention, when carbon neutrality is achieved by using the solid biomass charcoal described in claim 2 as a heat source for a charcoal roaster when roasting green coffee beans, almost no soot is generated when the solid biomass charcoal is burned.

[0015] In the method for producing solid biomass fuel according to the present invention, coffee bean husks peeled off during roasting of green coffee beans are collected, and an aqueous solution in which lignin or another binding promoter is dissolved is sprayed onto the thin-skinned coffee bean husks to add 0.1 to 3% lignin or another binding promoter, and the coffee bean husks are pulverized from the thin skin state into a fine powder, and then the coffee bean husks are extruded under heat and pressure to solidify them into a pellet or the like.

[0016] Furthermore, in the method for producing solid biomass charcoal according to the present invention, coffee bean husks peeled off during roasting of green coffee beans are collected, and an aqueous solution in which lignin or another binding promoter is dissolved is sprayed onto the thin-skinned coffee bean husks to add 0.1 to 3% lignin or another binding promoter. The coffee bean husks are then pulverized from their thin state into a fine powder, and the coffee bean husks are then extruded under heat and pressure to solidify them into a pellet shape or the like. The coffee bean husks are then heated to a high temperature of about 800°C in an oxygen-free environment in a charcoal kiln, and unnecessary organic matter is discharged as carbon monoxide, thereby carbonizing the coffee bean husks.

[0017] Preferably, the rate of spraying of the aqueous solution in which lignin or another binding promoter is dissolved is 10 to 15% relative to the coffee bean husks. Effect of the Invention

[0018] The solid biomass fuel of the present invention can be efficiently obtained from thin coffee bean husks that would otherwise be discarded, and can be used as a normal heat source as is. As a result, not only is the disposal cost of coffee bean husks generated during roasting unnecessary, but there is also the advantage that it can be sold as solid fuel.

[0019] The solid biomass charcoal according to the present invention can be produced by carbonizing solid biomass fuel by heating it to a high temperature of about 800°C in an oxygen-free state in a charcoal kiln. Since the solid biomass charcoal according to the present invention does not emit soot like coal during combustion, it can be used as a heat source for a charcoal roaster, and can achieve carbon neutrality in roasting green coffee beans. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic explanatory diagram showing an embodiment in which an aqueous solution of lignin is sprayed onto coffee bean husks. [Diagram 2] FIG. 1 is a cross-sectional view showing a main part of a grind mill that can be used in the present invention. [Diagram 3] FIG. 1 is a schematic cross-sectional view illustrating a charcoal kiln that can be used in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The solid biomass fuel according to the present invention is made of coffee bean husks that are peeled off during roasting of green coffee beans. Green coffee beans are the seeds of coffee cherries harvested from coffee trees, and are in their raw state after only the parchment has been removed. In green coffee beans, the husks refer to the thin layer (silver skin) commonly known as chaff that covers the inside of the green coffee beans, and are peeled off from the coffee beans during roasting.

[0022] The thin-skinned coffee bean husks are peeled off from the green coffee beans at a roasting temperature of 140-185°C and float in the air with the exhaust gas, so they are collected in the exhaust duct and separated and recovered by a cyclone separator. For example, coffee bean husks contain 12-20% crude fiber as a pulp component, 6.5% pectin, 10-14% free fiber, 11-12% crude protein, 6-7% ash, 1.3% caffeine, 2.6% chlorogenic acid, 1.8-8.6% tannin, 17.5% lignin, and 1.6% caffeic acid.

[0023] The green coffee beans used in the present invention are not particularly limited to a particular type, but it is generally desirable to use green coffee beans of the Arabica or Robusta species. The amount of husks in green coffee beans varies slightly depending on the type of coffee, with around 0.9% of the green bean weight being recovered for Brazilian Arabica beans and around 0.3% for Vietnamese Robusta beans. In the case of the present applicant, when roasting approximately 25 tons per day, around 200 kg of coffee bean husks are recovered.

[0024] The obtained coffee bean husks are in the form of amorphous thin skins when collected and must be ground into a uniform fine powder, and this grinding operation is preferably carried out using a known grind mill 1 as shown in Figure 1, which continuously pressurizes the coffee bean husks to solidify them into pellets or briquettes. In general, the solidification of plant fibers is greatly influenced by lignin, pectin, fibrous substances, etc., and the action of lignin, the main component of lignified cell walls in wood or straw, is required to re-solidify the coffee bean husks that have once been peeled off and broken into pieces.

[0025] An example of an applicable grind mill 1 is the Grind Mill Momigalite Production Machine (manufactured by Tromso Agricultural Machinery). In the grind mill, for example, a roll grinder rolls on a circular plate with through holes of 8 mm or 12 mm diameter at regular intervals, and the coffee bean husks enter the gap between the circular plate and the roll grinder, and are extruded from each through hole by the pressing force to become pellets or the like.

[0026] Although the grind mill 1 can continuously pulverize and solidify the coffee bean husks, the coffee bean husks are very light, dry, and contain a large amount of air, so that when the husks are ground down in the mill housing, frictional heat is generated, which may cause a fire, and if the coffee bean husks become too hot due to this frictional heat, the lignin content decreases, making solidification difficult. If the coffee bean husks are simply processed into pellets or briquettes by pressing alone, as in JP2019-502013, the shaping will be insufficient and there is also a risk of fire.

[0027] Generally, lignin, which promotes the binding of lignified fibers, is contained in wood at 20-35% and in herbaceous plants at 15-25%. If the fibers are not sufficiently bound and solidification is difficult, it is possible to consider adding an appropriate amount of lignin or other binding promoters. Lignin acts as an adhesive that connects lignified cells to each other, and it ensures the binding of finely powdered coffee bean husks compared to other binding promoters. When producing solid fuel, other binding promoters may be used in addition to lignin. Examples of other binding promoters include polysaccharides such as starch, glycerol, natural paraffin, lignosulfonate, and vegetable oil.

[0028] When extrusion-molding the coffee bean husks into pellets or briquettes, it is preferable to add moisture to the husks in order to more reliably achieve pulverization and solidification, since the husks are dry. Water can be supplied to the coffee bean husks by directly spraying water on the pulverized coffee bean husks themselves. The water spray rate is 10 to 15% with respect to the coffee bean husks, and for example, 5 liters is added to 40 kg of the husks to set the water spray rate at 12.5%. In this case, if the water spray rate is less than 10%, solidification is likely to be difficult, and if it exceeds 15%, the solidification is delayed due to excess moisture.

[0029] Lignin, such as powder, is preferably dissolved in water and added to the coffee bean husks; adding it to the coffee bean husks by watering makes it easier for the lignin to spread throughout the husks, and the same goes for other binding promoters. Lignin is heated in the presence of water and softens and becomes fluid, thereby facilitating the formation of the coffee bean husks and compensating for the loss of lignin components due to frictional heat. Replenishing lignin or other binding promoters can supplement the adhesive strength of the finely divided coffee bean husks together with water.

[0030] The amount of lignin or other binding promoter added is preferably 0.1 to 3% relative to the coffee bean husks. If the addition rate is less than 0.1%, it will be difficult to solidify in the grinding mill, and if it exceeds 3%, the additive will be excessive, resulting in high costs. In general, the amount of lignin added to the coffee bean husks is more preferably 0.15 to 1%, and if another binding promoter is added, the amount should be slightly higher, at 2 to 3%.

[0031] The aqueous solution in which lignin or other binding promoters are dissolved is preferably sprayed onto the thin-skinned coffee bean husks before they are fed into the grind mill. For example, when the husk raw material containing the lignin-dissolved water is fed into the grind mill and extruded from the heater tunnel under a certain pressure at a heating temperature of about 180 degrees, the lignin acts as a melted adhesive and the husks are solidified to form a woody solid biomass fuel. In FIG. 1, water 3 is added to the coffee bean husks 2 fed into the grind mill 1, and the coffee bean husks 2 are continuously sprayed with water via a pressure tank 5 containing water in which lignin is dissolved. Also, if the heating temperature is the same but the pressure is made very strong to bring the state closer to that of coal, so-called biomass coke can be obtained.

[0032] The obtained solid biomass fuel can be used as a normal heat source, and if it is further converted into coke, it can be used for coke roasting, which is offered by some hamburger chains, etc. However, even if it is converted into coke, it retains properties similar to coal fuel and is prone to generating smoke during combustion, so when it is used in a charcoal roaster, it is not preferable because unnecessary soot may adhere to the roasted coffee beans.

[0033] This solid biomass fuel can be further processed into solid biomass charcoal by heating it to about 800°C in an oxygen-free environment in a charcoal kiln, emitting unnecessary organic matter as carbon monoxide and carbonizing it. In Figure 3, Tromso's original charcoal kiln is shown as an example of a usable charcoal kiln 7. The obtained solid biomass charcoal does not emit soot like coal when burned. This solid biomass charcoal can be used as a heat source for a charcoal roaster, since all heat sources for charcoal roasted coffee by the Coffee Association are said to be from charcoal combustion, but the type of charcoal is not mentioned, and so it can be used as a heat source for a charcoal roaster, achieving carbon neutrality in roasting green coffee beans. EXAMPLES

[0034] Next, the present invention will be described based on examples, but the present invention is not limited to these examples. 25 tons of raw coffee beans were roasted at a temperature of 140 to 185°C per day using a direct-fire charcoal / gas roaster installed in the applicant's factory, and the thin-film-like coffee bean husks that peeled off during the roasting were collected. The coffee bean husks floated in the air together with the exhaust gas, so they were collected in the exhaust duct and separated by a cyclone separator, allowing 200 kg to be collected.

[0035] On the other hand, 200 g of lignin powder is dissolved in 5 L of water to obtain an aqueous solution containing 4% lignin. As the dry lignin powder, a brown powder with the trade name: Lineo (manufactured by Stora Enso) is used.

[0036] As shown in Figure 1, 40 kg of coffee bean husks 2 were used for the experiment, and were fed into a known grind mill 1, a grind mill-momighalite production machine (product name: TRM-120JPF, manufactured by Tromso Agricultural Co., Ltd.), while at the same time, 5 liters of an aqueous solution containing 4% dissolved lignin was uniformly sprayed onto the 40 kg of coffee bean husks using a pressure tank 5.

[0037] The Grind Mill Momigalite Production Machine has a processing capacity of about 120 kg / h, and the roll grinder rolls on a circular plate with 8 mm or 12 mm diameter holes at regular intervals to grind the coffee bean husks. The coffee bean husks enter the gap between the circular plate and the roll grinder, and are extruded from each hole by the pressing force to form pellets.

[0038] Assuming that the production of coffee bean husks reaches 1500 kg in about one month, the amount of lignin required will be 7.5 kg. EXAMPLES

[0039] A mill device 10 as shown in Fig. 2 may be used as the grind mill 2. The mill device 10 includes a fine grinding section 12 that pulverizes coffee bean husks into fine powder, and a heating and compressing section 14 that heats and compresses the finely ground coffee bean husks to produce bio-coke. The fine grinding section 12 includes a rotor 16 that can rotate around the rotor shaft, and a housing 18 having an accommodation recess 17 that opens in the horizontal direction, and the rotor 16 is accommodated in the accommodation recess 17 so that the rotor shaft 20 faces horizontally.

[0040] The rotor 16 is conical in shape with a diameter gradually decreasing toward the tip, and its outer circumferential surface is formed with a plurality of ridges that extend helically at a predetermined twist angle along the rotor shaft 20. The inner circumferential surface of the housing 18 is formed with a plurality of cutting edges that extend helically at a predetermined twist angle along the rotor shaft 20, and the cutting edges are spiral in the opposite direction to the respective ridges. A communication hole 22 that communicates with the accommodation recess 17 is formed in the upper part of the housing 18.

[0041] A funnel-shaped hopper 24 that opens in the vertical direction is attached to the periphery of the upper opening of the communication hole 22, and when coffee bean husks are dropped into the hopper 24 from above, they are supplied to the accommodating recess 17 through the communication hole 22. A discharge hole 28 that has a circular cross section and extends along the rotor shaft 20 and communicates with the accommodating recess 17 is formed in the housing 18 at a position corresponding to the tip of the rotor 16. Meanwhile, a gear box 26 that rotates the rotor 16 around the rotor shaft 20 is fixed to the housing 18 so as to cover the opening of the accommodating recess 17, and the housing 18 and the gear box 26 form a rotor accommodating space.

[0042] In the fine grinding section 12, the coffee bean husks supplied from the communication hole 22 to the rotor accommodating space are finely ground by the ridges and cutting edges due to the rotation of the rotor 16 into fine powder, and the fine powder is moved towards the discharge hole 28. A screw conveyor 32 is disposed inside the rear end side of the cylinder 30. The obtained fine powder is successively extruded from the other end of the cylinder 30 via the screw conveyor 32 and cooled, and the lignin in the fine powder solidifies to obtain pellets 34. The pellets 34 are then cut at predetermined intervals by a known cutter (not shown).

[0043] The pellet-shaped solid biomass fuel produced by the mill device 10 is further heated to approximately 800°C in an oxygen-free environment in a charcoal kiln 7 (Fig. 3), and after the temperature rises to approximately 800°C, the heating is maintained for approximately 90 minutes and then cooled for 24 hours. This high-temperature heating causes unnecessary organic matter to be discharged from the solid biomass fuel as carbon monoxide, and the solid biomass fuel is carbonized and processed into solid biomass charcoal.

[0044] The obtained solid biomass charcoal produces almost no soot like coal when burned. This solid biomass charcoal can be used as a heat source for a charcoal roaster, achieving carbon neutrality in roasting green coffee beans. [Explanation of symbols]

[0045] 1. Grind Mill 2 Coffee bean husks 5. Pressurized Tank

Claims

1. This solid biomass fuel is made from coffee bean husks that are peeled off during roasting of green coffee beans, the coffee bean husks being pulverized from a thin skin state into a fine powder, to which 0.1 to 3% of lignin has been added, and which has been extruded by heating and pressurizing.

2. This solid biomass charcoal is made from coffee bean husks peeled off during roasting of green coffee beans, the coffee bean husks being pulverized from a thin skin state into a fine powder, to which 0.1 to 3% of lignin has been added, which is then extruded by heating and pressurizing, and then further carbonized by heating at high temperatures in an oxygen-free environment in a charcoal kiln.

3. When roasting green coffee beans, carbon neutrality is achieved by using the solid biomass charcoal described in claim 2 as a heat source for a charcoal roaster, and almost no soot is generated when the solid biomass charcoal is burned.

4. A method for producing a solid biomass fuel, comprising recovering coffee bean husks peeled off during roasting of green coffee beans, spraying an aqueous solution in which lignin or another binding promoter is dissolved onto the thin-skinned coffee bean husks to add 0.1 to 3% of lignin or another binding promoter, pulverizing the thin-skinned coffee bean husks into a fine powder, and further solidifying the coffee bean husks into pellets or the like by extrusion molding under heat and pressure.

5. A method for producing solid biomass charcoal, comprising the steps of: recovering coffee bean husks peeled off during roasting of green coffee beans; spraying an aqueous solution in which lignin or another binding promoter is dissolved onto the thin-skinned coffee bean husks to add 0.1 to 3% of lignin or another binding promoter; pulverizing the thin-skinned coffee bean husks into a fine powder; and solidifying the coffee bean husks into a pellet-like form by extrusion molding under heat and pressure. The pellets are then heated to a high temperature of about 800°C in an oxygen-free state in a charcoal kiln, and carbonized by discharging unnecessary organic matter as carbon monoxide.

6. The method according to claim 4 or 5, wherein the water spray rate of the aqueous solution in which lignin or another binding promoter is dissolved is 10 to 15% relative to the coffee bean husks.

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