Coffee Grounds solid fuel pellet for suppressing clinker formation and method for manufacturing the same

Abstract

A coffee grounds solid fuel pellet that suppresses clinker formation and a method for manufacturing the same are provided. The coffee grounds solid fuel pellet comprises 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles in multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dots on the surface of the coffee grounds and the white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles. The coffee grounds solid fuel pellet according to the present invention causes the ash generated after combustion to collapse into a brittle powder form without forming a continuous glassy framework, thereby suppressing the formation of clinker, which was a problem in conventional coffee grounds pellets, and preventing clogging of the combustion chamber.

Description

Technology Field

[0001] The present invention relates to a solid fuel pellet of coffee grounds that suppresses the generation of clinker and a method for manufacturing the same. More specifically, the invention relates to a solid fuel pellet of coffee grounds that suppresses the generation of clinker, which is formed by the clumping of ash after the combustion of coffee grounds, and a method for manufacturing the same that suppresses the generation of clinker, thereby causing the ash to break easily. Background Technology

[0002] Organic waste generated across industry, agriculture, and daily life increases the burden of disposal, yet it can serve as a valuable energy source when properly recycled. In particular, coffee grounds, which are produced in large quantities during food manufacturing, exhibit a relatively high calorific value, making them highly promising as a solid fuel. Accordingly, attempts have been made to manufacture coffee grounds into pellets for use in existing wood pellet stoves. Coffee ground pellets offer the advantages of easy raw material procurement and the ability to utilize the existing distribution infrastructure and combustion equipment of wood pellets.

[0003] Typically, wood pellet stoves are designed so that pellets stored in a hopper are fed into the combustion grate by gravity, and after combustion, the ash falls downward through the grate's opening. Wood pellets facilitate continuous combustion because they contain low ash content and the ash breaks down easily into powder, preventing the combustion grate from clogging. However, coffee grounds pellets have a strong tendency for ash to melt and aggregate to form clumps (clinker) during combustion due to the influence of oil and inorganic components. This clinker hardens and remains on the combustion grate, blocking it, hindering the fall of new pellets, and reducing air supply, thereby causing operational issues such as combustion instability and flame extinction. The formation of such clinker is a major obstacle to the practical application of coffee grounds pellets.

[0004] In the past, methods were proposed to add wood powder, agricultural by-products, charcoal, and fine charcoal powder to coffee grounds; however, even with the addition of these additives, the ash properties were not improved, or pellet strength and moldability were reduced, making commercialization difficult. In particular, as the proportion of various additives increased, the proportion of the main ingredient, coffee grounds, decreased significantly, resulting in a problem where the purpose of utilizing coffee grounds was not met.

[0005] Therefore, there was a need to develop solid fuel pellets that use coffee grounds as the main raw material, but do not clog the combustion chamber by breaking down the ash into powder instead of clumping into clinker after combustion. In addition, there was a demand for the development of economically viable coffee grounds pellets that can be used in existing wood pellet facilities without modification and can be manufactured stably through a conventional pellet molding process. Prior art literature

[0006] Korean Patent Publication No. 10-1831607, (December 23, 2018) The problem to be solved

[0007] The technical objective of the present invention is to solve these problems by providing a coffee grounds solid fuel pellet that suppresses the formation of clinker, which is formed when ash clumps together after the combustion of coffee grounds, and a method for manufacturing such a pellet that suppresses the formation of clinker, thereby causing the ash to break easily.

[0008] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0009] The coffee grounds solid fuel pellet that suppresses clinker generation according to the present invention comprises 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and the white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles, such that the ash generated after combustion does not form a continuous glassy framework but collapses into a brittle powder form.

[0010] The average particle size of the coffee grounds and the white charcoal is 2 mm or less, and the ratio of the particle size of the white charcoal to the particle size of the coffee grounds (white charcoal particle size / coffee grounds particle size) is 0.5 to 3.0, and the solid fuel pellets have a cylindrical shape with a diameter of 5 to 6 mm and a length of 10 to 25 mm, and the moisture content can be maintained at 10 weight% or less.

[0011] A method for manufacturing solid fuel pellets from coffee grounds that suppresses clinker generation according to the present invention comprises: (a) a step of preparing in powder form 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and the white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles; (b) a step of uniformly mixing the coffee grounds, the white charcoal, and the starch-based binder to form a mixed powder; (c) a step of feeding the mixed powder into a pellet molding machine to form a primary pellet in the form of a pellet; and (d) a step of drying the primary pellet to manufacture solid fuel pellets.

[0012] In step (a) above, the moisture content of the coffee grounds can be maintained at 15 to 20 weight%, in step (c) above, the moisture content of the primary pellets can be maintained at 10 to 15 weight%, and in step (d) above, the moisture content of the solid fuel pellets can be maintained at 10 weight% or less.

[0013] In step (b) above, the coffee grounds and the starch-based binder can be uniformly pre-mixed first, and then the white charcoal can be added stepwise thereafter so that the white charcoal is multi-point dispersed within the continuous phase of the coffee grounds.

[0014] The average particle size of the coffee grounds and the white charcoal is 2 mm or less, and the ratio of the particle size of the white charcoal to the particle size of the coffee grounds is 0.5 to 3.0, and in step (d), the solid fuel pellets have a cylindrical shape with a diameter of 5 to 6 mm and a length of 10 to 25 mm, and the moisture content can be maintained at 10 weight% or less. Effects of the invention

[0015] Although the coffee grounds solid fuel pellet according to the present invention has coffee grounds as its main component, it significantly suppresses the formation of clinker, which was a problem in conventional coffee grounds pellets, so that after combustion, the ash does not remain as lumps on the combustion mesh but is easily broken into a powder state and falls easily through the combustion mesh.

[0016] In addition, coffee grounds solid fuel pellets can be used as fuel for continuous combustion in facilities using grate-type combustion grates, such as general wood pellet stoves and boilers, without separate structural changes or special operating conditions.

[0017] In particular, in so-called inverted combustion stoves where pellets automatically fall from the hopper into the combustion chamber by their own weight, the problem of new pellets supplied from the top getting caught in the clinker pile and failing to descend is resolved because the ash falls smoothly below the combustion grate after combustion, thereby improving automatic feeding performance and continuous operation.

[0018] In addition, since the ash remains in powder form rather than lumps, cleaning is easy, and the user can significantly reduce the hassle and work time required to forcibly remove clinker from the combustion mesh with a tool.

[0019] Meanwhile, since food waste such as coffee grounds, which is generated in large quantities, can be stably converted into fuel through the solid fuel pellets of the present invention, it can contribute to reducing the burden of waste treatment while increasing the utilization of biomass energy resources. Brief explanation of the drawing

[0020] FIG. 1 is a perspective view illustrating the appearance of a coffee grounds solid fuel pellet according to one embodiment of the present invention. Figure 2 is a photograph of the ash after combustion of conventional coffee grounds solid fuel pellets. Figure 3 is a photograph of the ash after combustion of coffee grounds solid fuel pellets according to one embodiment of the present invention. FIG. 4 is a flowchart of the manufacturing process of coffee grounds solid fuel pellets according to one embodiment of the present invention. Figure 5 is a photograph showing the raw materials for coffee grounds solid fuel pellets prepared according to the process of Figure 4. Figure 6 is a photograph showing the mixing of raw materials for coffee grounds solid fuel pellets according to the process of Figure 4. Figure 7 is a photograph showing the process of molding the raw material for coffee grounds solid fuel pellets according to the process of Figure 4. Figure 8 is a photograph showing the drying of raw materials for coffee grounds solid fuel pellets according to the process of Figure 4. Specific details for implementing the invention

[0021] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the claims. Throughout the specification, the same reference numerals refer to the same components.

[0022] Hereinafter, a coffee grounds solid fuel pellet that suppresses clinker generation according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0023] First, referring to FIG. 1, the coffee grounds solid fuel pellet (1) of the present invention forms a continuous phase (hereinafter referred to as "continuous phase") based on coffee grounds (10) in powder form, and exists as a dispersed phase in which white charcoal (30) is dispersed in the form of fine particles in powder form within the continuous phase of coffee grounds (10). Meanwhile, the structure has a starch-based binder (20) distributed as a film or dot on the surface of the coffee grounds (10) and white charcoal (30) particles. The coffee grounds solid fuel pellet (1) is preferably formed into a cylindrical shape with a diameter of about 5 to 6 mm and a length of about 10 to 25 mm.

[0024] The coffee grounds solid fuel pellet (1) of the present invention comprises coffee grounds (10), white charcoal (30), and a starch-based binder (20), and the respective mixing ratios are set in the range of 73 to 83 parts by weight of coffee grounds (10), 16 to 24 parts by weight of white charcoal (30), and 1 to 3 parts by weight of starch-based binder (20). The coffee grounds solid fuel pellet (1) maintains the characteristics of a solid fuel with coffee grounds as the main component, while exhibiting the characteristic that the ash does not remain as a clinker (lump) after combustion but collapses into a brittle powder, is advantageous for molding, and has the mechanical strength required during use.

[0025] Coffee grounds (10) are the main fuel component that determines the calorific value and combustion characteristics, and must be included in a sufficient proportion of the entire coffee grounds solid fuel pellet (1). If the amount of coffee grounds (10) included in the coffee grounds solid fuel pellet (1) decreases to less than 73 parts by weight, the proportion of white charcoal (30) becomes relatively high, weakening its significance as a coffee grounds-based fuel. In particular, from the perspective of environmental policy regarding the recycling of food by-products into fuel, problems may arise that make it difficult to be recognized as eco-friendly energy. Conversely, if the amount of coffee grounds (10) included in the coffee grounds solid fuel pellet (1) exceeds 83 parts by weight, the inherent low-melting-point ash characteristics of the coffee grounds (10) become dominant, and despite the mixing of white charcoal (30), the ash forms a continuous glassy framework, causing a problem in which clinker is generated.

[0026] White charcoal (30) leaves brittle ash that breaks easily after combustion and serves to cut the continuous skeleton of ash formed by the coffee grounds (10) from the inside. If the mixing ratio of white charcoal (30) included in the coffee grounds solid fuel pellet (1) is lowered to less than 16 parts by weight, the density of the dispersed phase of white charcoal (30) within the continuous phase of the coffee grounds (10) is lowered, so the continuous path of the coffee grounds (10) ash is not effectively cut, and the risk of ash remaining as lumps on the combustion network increases. Conversely, if the white charcoal (30) included in the coffee grounds solid fuel pellet (1) is excessively included in excess of 24 parts by weight, contact between white charcoal (30) particles increases, creating a possibility of forming a continuous phase, which may result in problems such as reduced strength, molding instability, and increased costs. Therefore, white charcoal (30) is included in the coffee grounds solid fuel pellet (1) in an amount of 16 to 24 parts by weight to achieve a clinker suppression effect, improved moldability, and strength maintenance.

[0027] The starch-based binder (20) provides a bond between the coffee grounds (10) and white charcoal (30) particles during molding, and at the same time, it decomposes at a relatively low temperature during combustion, rapidly releasing the bonding force and making the ash structure brittle and prone to collapse. If the starch-based binder (20) included in the coffee grounds solid fuel pellet (1) is less than 1 weight part, the mechanical strength of the molded pellet becomes insufficient, causing it to break during handling or increase dust generation, and it is difficult to maintain the originally intended microstructure during combustion. Conversely, if the starch-based binder (20) included in the coffee grounds solid fuel pellet (1) exceeds 3 weight parts, there is a risk that the binder residue will increase, the amount of ash after combustion will increase, or the ash characteristics will change, contributing to the formation of lumps. Therefore, the range of 1 to 3 weight parts, which is the component ratio of the starch-based binder (20) included in the coffee grounds solid fuel pellet (1), balances moldability and ash behavior after combustion.

[0028] As a representative embodiment of the present invention, the coffee grounds solid fuel pellet (1) uses 78 parts by weight of coffee grounds (10), 20 parts by weight of white charcoal (30), and 2 parts by weight of a starch-based binder (20). This mixing ratio suppresses the generation of clinker, maintains pellet strength, and provides particularly excellent results in terms of calorific value. Conventional coffee grounds pellets composed of 98% by weight of coffee grounds and 2% by weight of starch have a calorific value of approximately 5,230 kcal / kg, whereas the coffee grounds solid fuel pellet (1) according to one embodiment of the present invention consists of 78% by weight of coffee grounds, 20% by weight of white charcoal, and 2% by weight of a starch-based binder, and has a calorific value of approximately 5,850 kcal / kg. That is, the coffee grounds solid fuel pellet (1) according to the present invention has a higher calorific value than conventional coffee grounds pellets, so it has excellent characteristics as a fuel, and because of its high calorific value and excellent combustion persistence, it can significantly reduce the possibility of clinker generation. However, the above representative embodiment is an exemplary embodiment exhibiting the best effect within the formulation ratio of the present invention, and may be appropriately modified and implemented by those skilled in the art within the aforementioned scope.

[0029] As illustrated in FIG. 1, the coffee grounds solid fuel pellet (1) of the present invention has coffee grounds (10) forming a continuous phase and white charcoal (30) existing as a dispersed phase. In order to actually implement the coffee grounds solid fuel pellet (1), it is necessary to limit the relationship between the particle size of each powder and the dimensions of the pellet. Limiting the average particle size of the powder-form coffee grounds (10) and the powder-form white charcoal (30) to 2 mm or less is intended to ensure that a sufficient number of particles are included within the cross-section of the pellet with a diameter of 5 to 6 mm, so that the coffee grounds (10) form a continuous matrix without interruption and the white charcoal can be dispersed at multiple points. If the particle size of either the coffee grounds (10) or the white charcoal (30) is excessively large, it will exist only as a few large lumps inside the pellet, which may cause the continuous phase and dispersed phase structure to collapse, or cause problems such as clogging of the equipment during molding or cracking of the pellet.

[0030] In addition, setting the ratio of the particle size of the white charcoal (30) powder to the particle size of the coffee grounds (10) powder (white charcoal particle size / coffee grounds particle size) to a range of 0.5 to 3.0 is a condition to maintain molding stability while sufficiently securing the role as a dispersed phase through the balance of particle sizes of the two components. If the particle size of the white charcoal (30) is excessively small compared to the particle size of the coffee grounds (10) (white charcoal particle size / coffee grounds particle size is less than 0.5), the requirements for binder and moisture increase, and an excessively dense structure is formed, which may make it difficult to discharge combustion gases. Conversely, if the particle size of the white charcoal (30) is too large compared to the particle size of the coffee grounds (10) (white charcoal particle size / coffee grounds particle size is greater than 3.0), the white charcoal (30) exists only as a few large particles, weakening the function of breaking the continuous framework of the coffee grounds (10) ash at various points, and may only cause local cracks or a decrease in strength. Therefore, the above ratio range contributes to maintaining a balanced microstructural role of coffee grounds (10) and white charcoal (30).

[0031] Meanwhile, the dimensions and moisture content of the coffee grounds solid fuel pellet (1) itself also have an important influence on combustion behavior and device suitability. The reason for forming it into a cylindrical shape with a diameter of 5 to 6 mm and a length of 10 to 25 mm is primarily to ensure compatibility with existing equipment and supply stability.

[0032] In terms of moisture content, managing the moisture content of the final coffee grounds solid fuel pellet (1) to 10 weight% or less is intended to ensure storage stability and combustion reproducibility. If the moisture content of the coffee grounds solid fuel pellet (1) is high, there is a concern regarding the proliferation of microorganisms, deterioration, and condensation during storage and transportation, and during combustion, heat is consumed first by the evaporation of moisture, which may reduce flame stability. Conversely, if the moisture content of the coffee grounds solid fuel pellet (1) is lowered excessively, moldability deteriorates, and the pellet may easily break and turn into dust. Therefore, maintaining the moisture content of the coffee grounds solid fuel pellet (1) to 10 weight% or less, particularly around 8 to 10 weight%, allows for maintaining storage stability and molding strength in balance.

[0033] The coffee grounds solid fuel pellet (1) of the present invention, due to the aforementioned composition, microstructure, dimensions, and moisture content conditions, causes the ash to collapse into a brittle powder form after combustion without forming a continuous glassy framework. Referring to FIG. 2, in the case of conventional coffee grounds pellets, the ash originating from coffee grounds melts and clumps together on the combustion net due to the influence of low-melting point components to form clinker. As shown in FIG. 2, when the ash cools, it clumps together to form hard clinker, causing a problem of blocking the combustion net.

[0034] On the other hand, in the coffee grounds solid fuel pellet (1) of the present invention, during the combustion process, the white charcoal (30) dispersion phase acts as an initiation point for internal cracks, and the starch-based binder (20) is thermally decomposed at a relatively low temperature, thereby releasing the binding of the ash structure, so that the ash is divided into small fragments and falls as powder-like ash.

[0035] As shown in FIG. 3, the coffee grounds solid fuel pellet (1) forms finely ground powder-like ash after combustion, so that ash lumps do not accumulate on the upper surface of the combustion mesh and the ash continuously falls down to the ash tray, thereby maintaining the effective airflow area of ​​the combustion mesh opening for a long time. Accordingly, the supply of combustion air is maintained stably, and new pellets fall smoothly from the upper hopper to the combustion mesh by gravity, and the continuous operation of the stove or boiler is greatly improved. In addition, the need for frequent manual cleaning to remove clinker is reduced, which has the effect of reducing the user's maintenance burden.

[0036] As described above, the coffee grounds solid fuel pellet (1) of the present invention uses coffee grounds (10) as the main fuel, and by appropriately setting the composition ratio, particle size, pellet dimensions, moisture content, and microstructure, it solves the problems of clinker generation and combustion mesh clogging that were issues with conventional coffee grounds pellets, and provides a fuel that can be stably used in existing wood pellet facilities.

[0037] Hereinafter, with reference to FIGS. 4 to 8, a method for manufacturing solid fuel pellets that suppress clinker generation according to one embodiment of the present invention will be described in detail.

[0039] 1. Raw Material Powder Preparation Step (Management of Raw Material Conditions and Moisture Content)

[0040] First, referring to FIGS. 4 and 5, coffee grounds (10), white charcoal (30), and a starch-based binder (20) are prepared in powder form (S100). These coffee grounds (10) are food waste generated after the production of coffee beverages, and if necessary, natural drying or artificial drying is performed to adjust the moisture content to a range of 15 to 20 weight%. Maintaining the moisture content of the coffee grounds (10) at 15 to 20 weight% ensures appropriate plasticity during molding, while suppressing molding defects (internal pores, cracks) caused by excessive moisture and preventing spoilage or mold growth during storage. If the moisture content of the coffee grounds (10) is too low, less than 15 weight%, the powder becomes excessively dry, so the bonds between particles are not sufficiently formed during molding compression, and the mechanical strength of the pellets decreases, leading to increased breakage and dust generation during handling.

[0041] In addition, if the moisture content of the coffee grounds (10) exceeds 20 weight%, the coffee grounds (10) themselves become sticky, making it easy for bridging or clogging to occur inside the pellet molding machine, and increasing the likelihood of cracks occurring due to moisture movement during the drying process after molding.

[0042] It is preferable to grind and sieve the coffee grounds (10) powder and white charcoal (30) powder so that their average particle size is 2 mm or less. By limiting the average particle size of the coffee grounds (10) powder and white charcoal (30) powder, a sufficient number of coffee grounds (10) particles are contained within the cross-section of a pellet with a diameter of 5 to 6 mm to form a continuous phase, and at the same time, white charcoal (30) particles can also exist as a dispersed phase throughout the inside of the pellet.

[0043] If the average particle size of the coffee grounds (10) powder is coarse to the extent that it exceeds 2 mm, a small number of large particles exist inside the pellet, which acts as a crack initiation point during molding and does not result in a uniform continuous phase and dispersed phase structure.

[0044] On the other hand, if only excessively fine powder of coffee grounds (10) is used, the molding pressure and binder requirements increase, and the wear of the molding machine accelerates, so the process burden may increase. Therefore, considering the characteristics of the equipment and raw materials, an average particle size of substantially 2 mm or less, preferably 100 to 800 μm, can be selected.

[0045] White charcoal (30) can be wood-based white charcoal with high fixed carbon content and low ash content, and is prepared as a powder of 2 mm or less, similar to coffee grounds (10). It is desirable to control the particle size so that the average particle size ratio (white charcoal particle size / coffee ground particle size) of the white charcoal (30) powder and the coffee grounds (10) powder is in the range of 0.5 to 3.0. By ensuring that the difference in size between the two particles is not too large, the white charcoal is evenly dispersed within the continuous phase of the coffee grounds during molding, and the white charcoal (30) acts appropriately as a crack initiation point in the ash structure after combustion. If the white charcoal (30) particles are too small compared to the coffee grounds (10) particles (white charcoal particle size / coffee grounds particle size is less than 0.5), the binder and moisture requirements increase due to excessive fineness, and an over-dense structure may be formed. Conversely, if the white charcoal (30) particles are too large (white charcoal particle size / coffee grounds particle size exceeds 3.0), a small number of large particles may exist inside the pellet, making it difficult to cut the continuous skeleton of ash made of coffee grounds at multiple points.

[0046] The starch-based binder (20) can be prepared in the form of corn starch, potato starch, or modified starch thereof, and can be used in a powder state or, if necessary, in a slurry state mixed with a small amount of water. The mixing ratio of the starch-based binder (20) is set to be in the range of 1 to 3 parts by weight relative to the sum of the coffee grounds (10) and white charcoal (30). This provides a condition in which sufficient binding force is imparted during molding, while the starch-based binder is thermally decomposed at a relatively low temperature during combustion, thereby releasing the binding force and making the ash brittlely prone to disintegration.

[0048] 2. Preliminary mixing and main mixing steps (mixing sequence for forming dispersion structure)

[0049] Referring to FIGS. 4 and 6, coffee grounds (10), white charcoal (30), and a starch-based binder (20) are then uniformly mixed to form a mixed powder (S200). At this time, it is important that the coffee grounds (10), white charcoal (30), and the starch-based binder (20) are each prepared in powder form and are uniformly mixed to form a homogeneous mixed powder.

[0050] In order to increase the dispersion of white charcoal (30) in a mixed powder composed of coffee grounds (10), white charcoal (30), and a starch-based binder (20), a two-step mixing method is preferred in which the coffee grounds (10) and the starch-based binder (20) are mixed first, and then the white charcoal (30) is added later.

[0051] First, the coffee grounds (10) and the starch-based binder (20) are pre-mixed so that the starch-based binder (20) is evenly coated on the surface of the coffee grounds (10) particles, and then white charcoal (30) is added stepwise from the rear end and mixed. The mixing method is advantageous for forming a dispersed phase structure in which the white charcoal (30) is evenly distributed in a dot-like manner within the continuous phase of the coffee grounds (10).

[0052] Specifically, a starch-based binder (20) is added to the coffee grounds (10) powder, and then stirred for a certain period of time in a paddle mixer or ribbon blender, etc., so that the binder is attached to each individual coffee grounds (10) particle in the form of a film or dots. Subsequently, instead of adding the entire amount of white charcoal (30) powder at once, mixing is continued while adding it in two or more separate additions. This method ensures that the white charcoal (30) particles do not clump in specific areas but are dispersed at multiple points throughout the entire continuous layer of coffee grounds (10). During this process, a small amount of water may be sprayed as needed to adjust the moisture content of the entire mixture to an appropriate range, and it is preferable to control the amount of moisture in the mixing stage by calculating inversely so that the moisture content of the primary pellet after molding becomes 10 to 15 weight percent.

[0053] It is desirable that the mixed powder, upon completion of uniform mixing, exhibits a uniform color and texture when viewed with the naked eye, and that the white charcoal (30) or starch-based binder (20) is not clumped together in specific areas. If the mixing time is too short, the white charcoal (30) may aggregate locally and be present in excessive amounts only in certain areas, and if it is too long, the raw material may be damaged or pulverized, which may increase the required amount of molding energy and starch-based binder (20). Therefore, an appropriate mixing time can be set according to the equipment and batch scale.

[0055] 3. Pellet molding stage (primary pellet formation and moisture content adjustment)

[0056] Referring to FIGS. 4 and 7, the mixed powder is fed into a pellet molder and extruded into cylindrical primary pellets while passing through a die with a diameter of 5 to 6 mm (S300). The die temperature and roller pressure of the pellet molder are set so that the starch-based binder (20) is activated. When the starch-based binder (20) is activated, a bonding force is generated between the coffee grounds (10) and white charcoal (30) particles. For example, the die temperature is typically 80 to 120, which is above the gelatinization temperature of the starch-based binder (20). When maintained within a certain range, the starch-based binder (20) partially gelatinizes during molding, forming an adhesive layer that fills the spaces between the particles. The adhesive layer can secure the initial mechanical strength of the coffee grounds solid fuel pellet (1). However, these temperature conditions are merely one example and can be appropriately changed depending on the type of binder and equipment characteristics.

[0057] During the molding process, it is desirable to maintain the moisture content of the primary pellets in the range of 10 to 15 weight percent. This is because if the primary pellets are too dry immediately after molding, cracks are likely to occur while passing through the die, and if the moisture content is too high, problems such as deformation after the pellets escape or stickiness of the molded body surface may occur. By comprehensively considering moisture adjustment during the mixing stage, compression heat inside the molding machine, and moisture evaporation, process conditions can be set so that the moisture content of the primary pellets falls within the above range. The molded primary pellets are cut automatically or manually to a length of approximately 10 to 25 mm, and this length is a range that takes into account the structure of the combustor hopper and conveying screw, as well as supply stability.

[0059] 4. Drying and cooling stage (final pellet moisture content and structural stabilization)

[0060] Referring to FIGS. 4 and 8, the primary pellet is transferred to a drying device and undergoes a drying step in which the moisture content is reduced to 10 weight% or less through hot air drying or natural drying to produce coffee grounds solid fuel pellets (1) (S400). By maintaining the moisture content of the coffee grounds solid fuel pellets (1) at 10 weight% or less, storage stability and combustion reproducibility can be secured. The moisture content of the coffee grounds solid fuel pellets (1) is set to 10 weight% as an upper limit value to ensure long-term storage stability and to stabilize the temperature rise and flame formation at the beginning of combustion.

[0061] If the drying temperature is excessively high during the drying process, the structure of the starch-based binder (20) may change excessively or the volatile components of the coffee grounds (10) may be lost. Therefore, it is desirable to set the drying conditions within a range where the internal temperature of the coffee grounds solid fuel pellet (1) does not overheat.

[0062] Meanwhile, the dried coffee grounds solid fuel pellets (1) may undergo an additional cooling step as needed to lower the temperature to near room temperature, and then an additional sorting process may be added. Through this process, damaged pellets and excessively long or short pellets can be removed to ensure product uniformity.

[0063] The coffee grounds solid fuel pellet (1) manufactured through this process has a structure in which the coffee grounds (10) serve as a continuous phase base connecting the entire structure, white charcoal (30) is dispersed in multiple points within the continuous phase of the coffee grounds (10) in the form of fine particles, and a starch-based binder (20) exists as a film or point on the surface of each particle, thereby stably realizing a microstructure. In addition, the mechanical strength, dimensional stability, storability, and combustion reproducibility of the coffee grounds solid fuel pellet (1) are ensured in balance through moisture content control and particle size conditions.

[0064] The coffee grounds solid fuel pellet (1) formed by the above manufacturing method induces the ash from the coffee grounds (10) to be divided into a number of brittle fragments by the thermal decomposition of the white charcoal (30) dispersion phase and the starch-based binder (20) before the ash forms a low-melting point glassy framework during combustion, and after combustion, the ash does not remain as a lump of clinker on the combustion net but falls easily as powder. Therefore, the above manufacturing method can be understood as a means to reproducibly implement a microstructure and compositional state that exhibits the function of suppressing clinker generation, going beyond a simple procedure of molding solid fuel pellets.

[0065] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. Explanation of the symbols

[0066] 1: Coffee grounds solid fuel pellets 10: Coffee grounds 20: Starch-based binder 30: White charcoal

Claims

Claim 1 A coffee grounds solid fuel pellet comprising 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles, wherein the average particle size of the coffee grounds and the white charcoal is 2 mm or less, and the ratio of the particle size of the white charcoal to the particle size of the coffee grounds (white charcoal particle size / coffee grounds particle size) is 0.5 to 3.0, and the solid fuel pellet has a cylindrical shape with a diameter of 5 to 6 mm and a length of 10 to 25 mm, and the moisture content is maintained at 10 weight% or less, thereby suppressing the generation of clinker in which the ash produced after combustion does not form a continuous glassy skeleton but collapses into a brittle powder form. Claim 2 delete Claim 3 delete Claim 4 (a) preparing in powder form 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and the white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles; (b) uniformly mixing the coffee grounds, the white charcoal, and the starch-based binder to form a mixed powder; (c) feeding the mixed powder into a pellet molding machine to form a primary pellet in the form of a pellet; and (d) drying the primary pellet to manufacture solid fuel pellets; wherein, in step (a), the moisture content of the coffee grounds is maintained at 15 to 20 weight%, and in step (c), the moisture content of the primary pellet is maintained at 10 to 15 weight%, and in step (d), the solid fuel A method for manufacturing coffee grounds solid fuel pellets that suppresses clinker formation while maintaining the moisture content of the pellets at 10 weight% or less. Claim 5 (a) preparing in powder form 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and the white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and the white charcoal particles; (b) uniformly mixing the coffee grounds, the white charcoal, and the starch-based binder to form a mixed powder; (c) feeding the mixed powder into a pellet molding machine to form a primary pellet in the form of a pellet; and (d) drying the primary pellet to manufacture solid fuel pellets; wherein, in step (b), the coffee grounds and the starch-based binder are first uniformly pre-mixed, and then the white charcoal is subsequently added stepwise to mix so that the white charcoal is multi-point dispersed within the continuous phase of the coffee grounds, thereby suppressing the formation of clinker. Method for manufacturing solid fuel pellets. Claim 6 (a) preparing in powder form 73 to 83 parts by weight of coffee grounds forming a continuous phase, 16 to 24 parts by weight of white charcoal existing as a dispersed phase in the form of fine particles at multiple points within the coffee grounds, and 1 to 3 parts by weight of a starch-based binder distributed as a film or dot on the surface of the coffee grounds and white charcoal, which is activated by high temperature and high pressure upon compression to impart bonding between the coffee grounds and white charcoal particles; (b) uniformly mixing the coffee grounds, white charcoal, and starch-based binder to form a mixed powder; (c) feeding the mixed powder into a pellet molding machine to form a primary pellet in the form of a pellet; and (d) drying the primary pellet to manufacture solid fuel pellets; wherein the average particle size of the coffee grounds and white charcoal is 2 mm or less, and the ratio of the particle size of the white charcoal to the particle size of the coffee grounds is 0.5 to 3.0, and in step (d), the solid fuel pellets have a diameter A method for manufacturing coffee grounds solid fuel pellets that suppress clinker formation, having a cylindrical shape of 5~6 mm and a length of 10~25 mm and maintaining a moisture content of 10 weight% or less.

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