Pellet storage method and pellet storage equipment

Abstract

To provide a method for storing biomass-derived pellets that can suppress spontaneous combustion when the pellets are stored. [Solution] A method for storing pellets, comprising: a deposit formation step of stacking biomass-derived pellets to form a pellet deposit; and a suppression material placement step of placing a water vapor adsorption suppression material on at least one of the surfaces of the formed pellet deposit and the deposit in the process of stacking the pellets, wherein the water vapor adsorption suppression material is a material that suppresses the adsorption of water vapor generated from the pellet deposit.

Description

Technical Field

[0001] The present invention relates to a method for storing pellets and pellet storage equipment.

Background Art

[0002] In recent years, biomass fuels have been studied in order to reduce the emissions of CO2, which is considered to be a cause of global warming. Although burning biomass generates CO2, since plants absorb CO2 and grow, the use of biomass fuels made from materials such as wood does not change the amount of CO2 in the atmosphere as a whole (carbon neutral). If this biomass fuel is used as fuel for a power plant, it is expected to significantly reduce CO2 emissions compared to a power plant that uses conventional fossil fuels such as coal. In addition, although the spread of renewable energy such as solar power generation and wind power generation is also being promoted, compared to those that depend on natural conditions (such as sunlight and weather), biomass fuel can be stored in a silo or the like, so flexible power generation according to power demand is also possible (supply-demand adjustment function). Therefore, it is a renewable energy that is excellent in that it can be operated in the same way as a conventional thermal power plant using fossil fuels.

[0003] On the other hand, since biomass has the property of being easily self-heating, technologies for enhancing the safety of biomass are being studied. For example, Patent Document 1 discloses a biomass storage device. This biomass storage device includes a storage container that stores either one or both of herbaceous biomass and woody biomass, and reduction environment formation prevention means for suppressing the growth of microorganisms in the storage container. As the reduction environment formation prevention means, means for blowing a gas (for example, an oxidizing gas and an inert gas, etc.) at a temperature above the growth limit temperature of microorganisms adhering to the biomass from vertically below the upper surface of the biomass stored in the storage container is described. Furthermore, Non-Patent Document 1 describes the results of an investigation into the spontaneous combustion mechanism when wood pellets are stored, as well as a method for evaluating their spontaneous combustion properties. Non-Patent Document 2 describes a method for evaluating the spontaneous heating properties when coal is stored. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-118187 [Non-patent literature]

[0005] [Non-Patent Document 1] "Investigation on the Spontaneous Combustion Potential of Wood Pellet Storage," Masayoshi Kimoto, Masami Tozawa, Research Report: M08022, Central Research Report of Electric Power Industry, May 2009. [Non-Patent Document 2] "Study on methods for evaluating spontaneous heating in coal storage management," Masaharu Matsumoto, 55th Coal Science Conference (Kitakyushu City), October 29, 2018. [Overview of the project] [Problems that the invention aims to solve]

[0006] Biomass is used as fuel and as an energy source for biomass power generation. Biomass pellets used as fuel may be stored on the ground, in silos, warehouses, or containers until they are ready for use, and during storage, spontaneous heat generation from the biomass itself can occur, potentially leading to ignition. Non-patent document 1 describes a mechanism by which spontaneous combustion of wood pellets occurs through microbial fermentation and natural oxidation. However, including this document, there are no actual cases of reproducing and verifying the phenomenon from microbial fermentation to ignition (details will be discussed later). The technology described in Patent Document 1 focuses on suppressing the growth of microorganisms attached to biomass and does not take into account the phenomenon of natural oxidation. Furthermore, the technology described in Patent Document 1 requires means to suppress the growth of microorganisms in the container containing the biomass (means to prevent the formation of a reducing environment), which makes the equipment complicated. In recent years, fires caused by the spontaneous heating of wood pellets have been reported at biomass power plants. There is a pressing need for the development of safer methods and equipment for storing biomass pellets.

[0007] The object of the present invention is to provide a method for storing biomass-derived pellets and a pellet storage facility that can suppress spontaneous combustion when storing biomass-derived pellets. [Means for solving the problem]

[0008] [1] A method for storing pellets, A sediment formation process involves stacking biomass-derived pellets to form a pellet deposit, The process includes a step of placing a water vapor adsorption suppressing material on the surface of at least one of the formed pellet deposits and the deposits in the process of stacking the pellets, The water vapor adsorption suppressing material is a material that suppresses the adsorption of water vapor generated from the pellet deposit. How to store pellets. [2] The suppression material placement step is a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit, The method for storing the pellets described in [1] above. [3] The suppression material placement step is a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit and on the surface of the deposit in the process of stacking the pellets. The method for storing pellets as described in [1] or [2] above. [4] If the suppression material placement step includes a step of placing a water vapor adsorption suppression material on the surface of the deposits in the process of stacking the pellets, The aforementioned suppression material placement step is performed two or more times during the stacking process. A method for storing pellets as described in any one of the above items [1] to [3]. [5] The suppression material placement step is a step of placing the water vapor adsorption suppression material along the contours of the formed pellet deposit and the deposit in the process of being piled up. A method for storing pellets as described in any one of the above items [1] to [4]. [6] The water vapor adsorption suppressing material is one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. A method for storing pellets as described in any one of the above items [1] to [5]. [7] The hydrophobic substance is one or more selected from the group consisting of heavy oil, light oil, petroleum-based residue oil, vegetable oil, waste plastic oil, waste tire oil, and biotar. The method for storing the pellets described in [6] above. [8] The hydrophobic substance is a vegetable oil. The method for storing the pellets described in [7] above. [9] The pellet piles are at least one of the following: open-air pellet piles, pellet piles stacked in silos and warehouses, and pellet piles stacked in containers. A method for storing pellets as described in any one of the above items [1] to [8].

[10] The pellet is at least one selected from the group consisting of woody biomass pellets, herbaceous biomass pellets, crop residue biomass pellets, and palm oil biomass pellets. A method for storing pellets as described in any one of the above items [1] to [9].

[11] The pellets are woody biomass pellets. The method for storing pellets as described in

[10] above.

[12] A pellet storage facility, A means of stacking biomass-derived pellets in a storage area to form a pellet deposit, The storage area comprises means for placing a water vapor adsorption suppressing material in at least a portion of the storage area, The storage location is at least one of an open storage area, a silo, a warehouse, and a container. The water vapor adsorption suppression material is a means for suppressing the adsorption of water vapor generated from the pellet deposit. Pellet storage equipment.

[13] The water vapor adsorption suppression material is one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. The method for storing pellets according to

[12] above.

Advantages of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a method for storing pellets and pellet storage equipment that can suppress spontaneous ignition when storing biomass-derived pellets.

Brief Description of the Drawings

[0010] [Figure 1] A diagram for explaining the mechanism by which pellets stacked on a pellet deposit spontaneously ignite. [Figure 2] A schematic diagram of a spontaneous heat generation test apparatus. s [Figure 3] A graph showing the results of the spontaneous heat generation test for Samples 1 to 2. [Figure 4] A graph showing the results of the spontaneous heat generation test for Test Examples 1 to 4. [Figure 5] A diagram for explaining the first example of the storage method according to this embodiment. [Figure 6] A diagram for explaining the second example of the storage method according to this embodiment. [Figure 7] A diagram for explaining the third example of the storage method according to this embodiment. [Figure 8] A scanning electron micrograph of a cross-section perpendicular to the longitudinal direction of the pellet. [Figure 9] A graph showing the relationship between the coating rate of palm oil and the specific surface area of the pellet when the pellet is coated with palm oil.

Modes for Carrying Out the Invention

[0011] In this specification, a numerical range represented by "~" means a range that includes the number written before "~" as the lower limit and the number written after "~" as the upper limit. In this specification, mass percentage concentration (unit: mass%) and weight percentage concentration (unit: weight%) are the same value.

[0012] [First Embodiment] [Storage method for pellets] The pellet storage method according to this embodiment (hereinafter also referred to as "the storage method according to this embodiment") comprises a deposit formation step of stacking biomass-derived pellets to form a pellet deposit, and a suppression material placement step of placing a water vapor adsorption suppression material on at least one of the surfaces of the formed pellet deposit and the deposit in the process of stacking the pellets. The water vapor adsorption suppression material is a material that suppresses the adsorption of water vapor generated from the pellet deposit.

[0013] In the storage method according to this embodiment, the water vapor adsorption suppressing material is placed on at least one of the formed pellet deposits and the deposits in the process of stacking the pellets. Typically, pellets are aggregates of wood powder, with a fine internal structure. Furthermore, by partially carbonizing the biomass, fine pores are created in the wood powder itself. Such pellets are thought to have a large surface area, making them more susceptible to water vapor adsorption. Figure 8 is a scanning electron microscope image of a cross-section of the pellet perpendicular to its longitudinal direction. The observation conditions were an acceleration voltage of 15 kV and a magnification of 20x. The pellet was made from acacia and was semi-carbonized. Figure 8 shows that the pellets have continuous fine grain boundaries. Therefore, by reducing the surface area of ​​the pellets, the amount of water vapor adsorbed is expected to decrease, and consequently, the generation of heat of adsorption can be suppressed. Figure 9 is a graph showing the relationship between the palm oil coating rate and the specific surface area of ​​the pellets when they are coated with palm oil. The pellets are the same as those used in Figure 8. Palm oil is an example of a hydrophobic substance. The palm oil coating rate is measured using the same method as described later for "coverage rate of the semi-carbonized pellet surface". Figure 9 shows that coating the pellets with palm oil reduces their specific surface area to more than 1 / 5 of its original size. Therefore, when a water vapor adsorption inhibiting material is placed on the surface of the pellet deposit, water vapor that moves from the deeper part of the pellet deposit to the surface is less likely to be adsorbed by the water vapor adsorption inhibiting material. Thus, even when water vapor moves from the deeper part of the pellet deposit to the surface, events (3) to (5) described below are less likely to occur. Furthermore, when a water vapor adsorption inhibiting material is placed on the surface of a pellet deposit during its stacking process, water vapor generated in the deeper parts of the pellet deposit becomes less likely to be adsorbed by the water vapor adsorption inhibiting material. As a result, the water vapor tends to remain near where the water vapor adsorption inhibiting material is placed. This is thought to make it more difficult for water vapor to move from the deeper parts of the pellet deposit to the surface. As described later, the movement of water vapor from the deeper parts of the pellet deposit to the surface is considered to be a factor that causes spontaneous combustion of pellets. Therefore, according to the storage method of this embodiment, spontaneous combustion can be suppressed when pellets are stored.

[0014] The water vapor adsorption suppression material is preferably one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. The coated pellets are preferably made from biomass. It is preferable that the water vapor adsorption suppressing material is not removed from the pellet deposit when the pellets in the pellet deposit are used as fuel. In other words, it is preferable that the water vapor adsorption suppressing material is not removed from the pellet deposit and is used for combustion together with the pellets. Further details regarding water vapor adsorption suppression materials will be provided later.

[0015] Biomass-derived pellets are not particularly limited as long as they contain biomass. The biomass content in the pellets is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit for the biomass content in the pellets is 100% by mass. Hereinafter, biomass-derived pellets may be simply referred to as pellets or biomass pellets. When pellets are used as fuel, it is preferable that the biomass in the pellets is semi-carbonized. "Partial carbonization," also known as "torrefaction," is a process that increases the carbon content by heating biomass to between 200°C and 350°C, or by steam explosion, which decomposes volatile components (low-boiling point components). When biomass is gradually heated, carbonization begins above 200°C, generating pyrolysis gases. Although the weight of the biomass decreases, the calorific value increases due to carbonization, thus improving the energy density per unit weight. Semi-carbonized pellets can be obtained, for example, by (i) heating biomass pellets at a temperature between 200°C and 350°C, or by (ii) molding semi-carbonized biomass powder into pellets. The semi-carbonized biomass powder in (ii) above can be obtained by known methods (such as steam explosion of biomass). For molding into pellets, known pelletizers can be used. Heating of biomass pellets and steam explosion to obtain semi-carbonized biomass powder can be carried out using known methods and reactors.

[0016] The pellet piles are preferably at least one of the following: pellet piles piled up on the ground, pellet piles piled up in silos and warehouses, and pellet piles piled up in containers. Pellet deposits may be formed outdoors or indoors (e.g., in dome-shaped or warehouse-shaped structures).

[0017] Spontaneous combustion of biomass often occurs when the biomass itself generates heat, causing its temperature to rise and eventually leading to ignition. Possible causes of biomass self-heating include oxidation, microbial fermentation, water adsorption, and water vapor adsorption. Biomass ultimately ignites due to oxidation, but since oxidation reactions are slow at room temperature, it is thought that some other factor must be involved to accelerate the oxidation process to a sufficient rate in order for spontaneous combustion to occur.

[0018] For example, Non-Patent Literature 1 proposes a mechanism of spontaneous combustion in which, at around room temperature, the heat generated by fermentation by microorganisms attached to the biomass raises the temperature of the biomass (fermentation exothermic reaction), and from that temperature, the temperature of the biomass continues to rise until oxidation proceeds at a sufficient rate (oxidation exothermic reaction) (see Figure 2.5 in Non-Patent Literature 1).

[0019] However, the inventors have observed that heat-treated semi-carbonized pellets generate heat even when they are not exposed to the external environment and have low moisture content after production. Believing that this cannot be explained solely by microbial fermentation, they investigated the effect of water vapor.

[0020] The inventors of this invention, using the spontaneous heating test apparatus shown in Figure 2 (with a configuration similar to the adiabatic heating test apparatus described in Non-Patent Literature 2), found that when water vapor was added to dry pellets at around room temperature, the temperature of the pellets rose by more than 10°C in about 8 hours (see Figure 3). As a result, they hypothesized that the oxidation rate was greatly increased by the rise in pellet temperature due to the water vapor, and that this could serve as a model for spontaneous combustion from room temperature.

[0021] In actual biomass storage sites, it is assumed that both high-moisture areas (humid areas) and relatively dry areas (dry areas) exist, and that the movement and adsorption of water vapor between these areas causes a temperature rise from room temperature (see Figure 1).

[0022] Therefore, we believe that if the movement of water vapor can be suppressed, the onset of spontaneous heating can be suppressed, which will lead to a reduction in the rate at which oxidation becomes the dominant process, and ultimately to the suppression of spontaneous combustion. This led to the completion of the present invention.

[0023] Based on the analysis results described below, the inventors inferred that the movement of water vapor from the deeper layers to the surface layers of the pellet deposit is a factor that causes the pellets to spontaneously ignite. Specifically, they inferred the following events (1) to (5). Figure 1 is a diagram illustrating the mechanism by which pellets piled up in a pellet deposit spontaneously combust (events (1) to (5) below). Figure 1 shows a state in which pellets are piled up on the ground, forming a pellet deposit.

[0024] Event (1): Once a pellet deposit is formed and a certain period of time has passed, the surface layer of the pellet deposit is exposed to sunlight and wind, causing the moisture content of the pellets deposited on the surface layer to decrease. In Figure 1, this surface region is labeled as the "Pellet Drying Region DR1". On the other hand, since the inner part of the pellet deposit is not exposed to air, the moisture content of the pellets deposited in the inner part is more easily maintained (less likely to change). In Figure 1, this inner region is labeled as the "pellet wet region WR1". Event (2): Moisture (water vapor) moves from the inner part of the pellet deposit (pellet wet region WR1) to the surface part of the pellet deposit (pellet dry region DR1). Event (3): Pellets in the pellet drying region DR1 (hereinafter also referred to as dried pellets) adsorb water vapor, generating heat of adsorption (see Figures 3-4 below). Event (4): The generated heat is transferred to another dry pellet in the pellet drying region DR1. Event (5): The heated dry pellets oxidize and spontaneously ignite.

[0025] <Analysis results on the mechanism of spontaneous combustion> First, I will explain the spontaneous heating test apparatus. Figure 2 is a schematic diagram of a spontaneous heating test apparatus (adiabatic heating test apparatus). The spontaneous heating test apparatus 300 comprises a constant temperature bath 50, a gas supply unit 80, a gas preheating unit 44, and a reactor 70A. The gas supply unit 80 includes a first flow path 91 through which oxygen gas flows, a second flow path 92 through which nitrogen gas flows, a third flow path 93, a fourth flow path 94, and a plurality of switching valves BV. The first flow path 91 contains a mass flow controller (MFC1) and a gate valve SV1. The second flow path 92 contains a gas flow meter 82 and a gate valve SV2. The third flow path 93 contains a humidifier 84 (for example, a water bubbling device) and a hygrometer 86 downstream of the humidifier 84. The gas preheating section 44 is made of copper pipes. The gas preheating section 44 receives heat from the constant temperature bath 50 as the test gas (nitrogen gas or oxygen gas containing water vapor) supplied from the gas supply section 80 passes through the copper pipes, preheating the test gas to the same temperature as the constant temperature bath 50.

[0026] Reactor 70A is designed to be filled with sample 52. A lid 72A is placed on top of reactor 70A, and a gas supply pipe 64, a gas exhaust pipe 66, and a thermocouple 53 are positioned through this lid 72A toward the interior of reactor 70A. The gas supply pipe 64 extends to position E. Inside reactor 70A, the sample 52 is placed sandwiched between quartz wool 74 and 75 to ensure that the flow of the test gas is as uniform as possible. The constant temperature bath 50 is equipped with a heater (not shown). The heater's temperature is controlled by a temperature controller 46 so that it is equal to the temperature of the thermocouple 53 (the temperature of the sample 52). In other words, the temperature of the constant temperature bath 50 is controlled to be the same as the temperature of the thermocouple 53.

[0027] The spontaneous heating test is conducted by maintaining a simulated insulated state inside reactor 70A. During the spontaneous heating test, the test gas supplied from the gas supply unit 80 has its humidity measured by a hygrometer 86, is preheated to the same temperature as the constant temperature bath 50 in the gas preheating unit 44, then flows through the gas supply pipe 64 and is introduced into the reactor 70A, where it is released at position E (bottom of reactor 70A). The released test gas comes into contact with the lower quartz wool 75, then rises and flows through the sample 52 filled in reactor 70A, passes through the upper quartz wool 74, and is discharged from the gas discharge pipe 66. The nitrogen gas used in the test is introduced into reactor 70A by flowing through the second channel 92, the fourth channel 94, and the gas supply pipe 64 in that order. The oxygen gas to which saturated water vapor has been added is introduced into reactor 70A by flowing through the first channel 91, the third channel 93, and the gas supply pipe 64 in that order.

[0028] (Exothermic heating by water vapor) The spontaneous heat generation test was performed on samples 1 and 2 using the following method. The results are shown in Figure 3. Sample 1 consisted of semi-carbonized biomass powder (particle size 200 μm or less), and Sample 2 consisted of semi-carbonized biomass pellets (cylindrical shape, 8 mm in diameter, 10 mm to 30 mm in length). The type of biomass was acacia.

[0029] (Sample 1) Prior to the experiment, sample 1 was dried at 70°C under vacuum for 3 days to adjust the moisture content of the biomass powder to 0%. 200g of sample 1 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 34°C, measurement of the sample temperature was started.

[0030] (Sample 2) Prior to the experiment, sample 2 was dried at 70°C under vacuum for 3 days to adjust the moisture content of the biomass pellets to 0%. 200g of sample 2 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 40°C, the nitrogen gas was switched to oxygen gas with saturated water vapor (50 mL / min), and the measurement of the sample temperature was started. The measurement was stopped when the sample temperature reached 150°C.

[0031] (result) As shown in Figure 3, the time required to heat up to 150°C was significantly shorter for the biomass pellets to which water vapor was introduced (Sample 2) compared to the biomass powder to which water vapor was not introduced (Sample 1). In the case of Sample 2, it is thought that adsorption heat (coagulation heat) was generated when water vapor was adsorbed (or coagulated) onto the pellet surface at temperatures below 60°C. Furthermore, in Sample 2, the initial temperature rose by more than 10°C in a short time (approximately 8 hours), which is thought to have accelerated subsequent oxidation.

[0032] (The effect of water vapor on the moisture content of pellets) Spontaneous heat generation tests were conducted using biomass pellets according to the following test examples 1-4. The results are shown in Figure 4. Prior to the experiment, biomass pellets were dried at 70°C under vacuum for 3 days to adjust their moisture content to 0%. This was used as Sample 3. Sample 3 was prepared under the same conditions as Sample 2, with the moisture content of the biomass pellets adjusted to 0%. Prior to the experiment, biomass pellets were dried in the sun (indoors) to adjust their moisture content to 2%. This was used as Sample 4.

[0033] (Test Example 1) 200g of sample 3 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 52°C, measurement of the sample temperature was started. The measurement was terminated when the sample temperature reached 150°C.

[0034] (Test Example 2) 200g of sample 3 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 40°C, the nitrogen gas was switched to oxygen gas with saturated water vapor added (50 mL / min), and the measurement of the sample temperature was started. The measurement was terminated when the sample temperature reached 150°C.

[0035] (Test Example 3) 200g of sample 4 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 45°C, the nitrogen gas was switched to oxygen gas with saturated water vapor added (50 mL / min), and the measurement of the sample temperature was started. The measurement was terminated when the sample temperature reached 150°C.

[0036] (Test Example 4) 200g of sample 4 was packed into reactor 70A, and nitrogen gas was supplied to reactor 70A from gas supply unit 80 (50 mL / min). When the sample temperature reached 45°C, measurement of the sample temperature was started. However, in the case of test example 4, the measurement was stopped after 7 days because the sample temperature did not rise.

[0037] (result) As shown in Figure 4, in a comparison between Test Example 1 and Test Example 2, which used biomass pellets with a moisture content of 0%, Test Example 2, in which steam was introduced, showed a significantly shorter heating time to 150°C compared to Test Example 1, in which steam was not introduced. In Test Example 3, which used biomass pellets with a moisture content of 2%, the temperature initially rose by nearly 10°C due to adsorption heat after the introduction of steam. The temperature then gradually increased for approximately 25 days, finally reaching 150°C over 30 days. In Test Example 3, it is considered that the biomass pellets transitioned to autonomous oxidation during the period of gradual temperature increase over approximately 25 days. In Test Example 4, which used biomass pellets with a moisture content of 2% and did not introduce water vapor, the sample temperature actually decreased. This is thought to be because the water in the pellets evaporated, and the heat of vaporization caused the temperature to drop.

[0038] The relationship between the events (1) to (5) inferred by the inventor and the aforementioned analysis results will be explained. Regarding events (1) to (3): The biomass pellets in the pellet wet region WR1 in Figure 1 correspond to the biomass pellets in Test Example 3, and the biomass pellets in the pellet dry region DR1 in Figure 1 correspond to the biomass pellets in Test Example 1. As shown in Figure 4, when moisture (water vapor) moves from the pellet wet region WR1 to the pellet dry region DR1 (Test Example 3 → Test Example 1), the dry pellets in the pellet dry region DR1 (Test Example 1) adsorb the water vapor, generating heat of adsorption. As a result, the temperature of the pellets rises rapidly (Test Example 1 → Test Example 2). Regarding events (4) and (5): The heat generated by the aforementioned adsorption heat is transferred to the surrounding dry pellets. The heated dry pellets are then oxidized, leading to spontaneous combustion.

[0039] Each step of the storage method according to this embodiment will be described.

[0040] <Deposit formation process> In the storage method according to this embodiment, the deposit formation step is a step of piling up biomass-derived pellets to form a pellet deposit. Known methods can be used as means for forming the pellet deposits. Means of forming pellet deposits include, for example, stackers, excavators, cranes, conveyors, and wheel loaders (so-called bulldozers). If the pellet storage location is a silo, warehouse, or container, the pellets may be dropped into the silo, warehouse, or container using known transport equipment (e.g., a belt conveyor).

[0041] <Suppression material placement process> In the storage method according to this embodiment, the suppression material placement step is the step of placing a water vapor adsorption suppression material on the surface of at least one of the formed pellet deposits and the deposits in the process of stacking pellets.

[0042] <Water vapor adsorption inhibiting material> The water vapor adsorption suppression material is preferably one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances.

[0043] (Coated pellets) We will refer to semi-carbonized pellets coated with a hydrophobic substance as coated pellets. The hydrophobic substance permeates into the pores inside the coated pellets, making the entire pellet hydrophobic. Therefore, by placing coated pellets on at least one surface of the pellet deposit or the deposit in the process of stacking pellets, the adsorption of water vapor generated from the pellet deposit can be suppressed. In addition, because the coating suppresses contact between the pellet surface and oxygen, the coated pellets themselves have an effect of suppressing spontaneous combustion.

[0044] Coated pellets are obtained by first obtaining semi-carbonized pellets using the method described in (i) or (ii) above, and then coating at least a portion of the surface of the semi-carbonized pellets with a hydrophobic substance.

[0045] (Hydrophobic substances) The hydrophobic substances are not particularly limited, but examples include heavy oil, light oil, petroleum-based residue oil, vegetable oil, biotar, waste plastic oil, waste tire oil, kerosene, and mineral oil. Hydrophobic substances may be used individually or in combination of two or more types. Examples of heavy oils include asphalt, coal tar, atmospheric residue (AR), and vacuum residue (VR). Examples of light oils include naphtha, heavy cracked diesel fuel (HCO3), undesulfurized vacuum diesel fuel (VGO), light diesel fuel (LGO), desulfurized vacuum diesel fuel (VHHGO), and heavy diesel fuel (HGO). Examples of petroleum-based residual oils include cracked residue oil (CLO), atmospheric residue oil (RC), desulfurized residue oil (DSRC), undesulfurized vacuum residue oil (VC), and ethylene bottom oil. CLO (Clean Oil Lot) is the residue oil produced when heavy oil is broken down, and specifically refers to the vacuum cracked residue oil obtained at an oil refinery. Examples of vegetable oils include olive oil, corn oil, sesame oil, rice oil, soybean oil, rapeseed oil, palm oil, coconut oil, sunflower oil, safflower oil, cottonseed oil, coconut oil, and vegetable oils. Biotar is a distillate obtained by heating materials such as wood to 300°C or higher in an oxygen-free environment.

[0046] The hydrophobic substance is preferably one or more selected from the group consisting of heavy oil, light oil, petroleum-based residue oil, vegetable oil, waste plastic oil, waste tire oil, and biotar. In this embodiment, the hydrophobic substance is preferably a vegetable oil. The hydrophobic substance is more preferably one or more selected from the group consisting of asphalt, coal tar, CLO, rapeseed oil, palm oil, coconut oil, and biotar.

[0047] In coated pellets, the coverage rate (area %) of the surface of the semi-carbonized pellets with hydrophobic material is preferably 50 area % or more, more preferably 60 area % or more, even more preferably 70 area % or more, and even more preferably 80 area % or more. Furthermore, the coverage rate (area %) of the semi-carbonized pellet surface with hydrophobic material is preferably 95 area % or less, more preferably 90 area % or more, and even more preferably 85 area % or more. The upper limit of the coverage rate (area %) is 100 area %. The coverage rate of the semi-carbonized pellet surface by hydrophobic material is calculated by measuring the specific surface area with nitrogen gas using a gas / vapor adsorption measuring device (Microtrac-Bel). The specific surface area with nitrogen gas is calculated using the BET method.

[0048] Coating methods include, for example, spraying, applying, or vapor-depositing a coating solution containing a hydrophobic substance onto the surface of the semi-carbonized pellets, or immersing the semi-carbonized pellets in a coating solution containing a hydrophobic substance. The coating solution is preferably (C1) a hydrophobic solution containing a hydrophobic substance and a solvent, (C2) an emulsion containing a hydrophobic substance, water and an emulsifier, (C3) a melt containing a molten hydrophobic substance, or (C4) a "spreading agent-containing melt" containing a molten hydrophobic substance and a spreading agent. The coating solution may be composed substantially of only a hydrophobic substance (for example, at a concentration of 99% by mass or more). Organic solvents (such as aromatics (e.g., toluene), alcohols (e.g., ethanol), ethers, n-hexane, and cyclohexane) are used as solvents. The hydrophobic substance content relative to the total mass of the coated pellets is preferably 1.0% by mass or more and 30.0% by mass or less, and more preferably 1.0% by mass or more and 20.0% by mass or less.

[0049] The coated pellets are composed of semi-carbonized pellets, and the surface of the semi-carbonized pellets is coated with a hydrophobic substance. It is believed that the hydrophobic substance penetrates not only the surface of the semi-carbonized pellets but also into the pores inside the coated pellets. Since the coated pellets have a smaller surface area than uncoated pellets (see Figure 9), water vapor adsorption can be reduced, and consequently, the generation of adsorption heat can be suppressed. Therefore, by placing coated pellets on the surface of at least one of the pellet deposits and the deposits in the process of stacking pellets, the adsorption of water vapor generated from the pellet deposits can be suppressed.

[0050] (Hydrophobic substances as materials that suppress water vapor adsorption) A hydrophobic substance may be used as a water vapor adsorption suppression material. The hydrophobic substance may be a liquid hydrophobic substance as exemplified above (hereinafter also referred to as a hydrophobic liquid) or a solid hydrophobic substance (hereinafter also referred to as a hydrophobic solid). When the water vapor adsorption suppressing material is a hydrophobic liquid, the suppressing material placement step is preferably a step of applying (e.g., by spraying and scattering) one of the aforementioned coating liquids (C1) to (C4) to at least one of the surfaces of the formed pellet deposit and the deposit in the process of stacking the pellets. As a result, the surface of the pellet to which the coating liquid has been applied is coated with a hydrophobic liquid, at least partially, thus achieving the same effect as the coated pellets described above.

[0051] When the water vapor adsorption suppressing material is a hydrophobic solid, the suppressing material placement step is to place the hydrophobic solid on at least one of the surfaces of the formed pellet deposit and the deposit in the process of stacking the pellets. Examples of hydrophobic solids include hydrophobic polymers and hydrophobic inorganic materials. The shape of the hydrophobic solid is not particularly limited, but it is preferably at least one of granular material, sandy material, fragments, and rod-shaped material. Furthermore, the hydrophobic solid may be a material such as granular material, sandy material, fragments, or rod-shaped material with the aforementioned hydrophobic liquid coated on its surface. The hydrophobic solid is preferably a combustible material from the viewpoint of burning it together with the fuel pellets, but it may also be a non-combustible material. Non-combustible materials are discharged as ash after combustion. When the water vapor adsorption suppression material includes a non-combustible material, the content of the non-combustible material is preferably 3% by mass or less relative to the total biomass pellets contained in the pellet deposit. When the content of the non-combustible material is 3% by mass or less, the low ash content, which is an advantage of biomass pellets as fuel, can be maintained.

[0052] When the water vapor adsorption suppressing material is a coated pellet and a hydrophobic solid, means for arranging the water vapor adsorption suppressing material include, for example, a crane, a stacker craner, a wheel loader, a belt conveyor, a stacker, and an excavator. If the water vapor adsorption suppression material is a hydrophobic liquid, for example, a known nozzle can be used.

[0053] In the storage method according to this embodiment, the suppression material placement step is preferably a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit. In the storage method according to this embodiment, the suppression material placement step is preferably a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit and on the surface of the deposit in the process of stacking pellets. In the storage method according to this embodiment, if the suppression material placement step includes a step of placing a water vapor adsorption suppression material on the surface of the pile during the stacking of the pellets, In the storage method according to this embodiment, the process of placing the suppressing material is preferably carried out two or more times during the stacking process. That is, it is preferable to place two or more water vapor adsorption suppressing materials on the stacked material. The types of the two or more water vapor adsorption suppressing materials may be the same or different. In the storage method according to this embodiment, the suppression material placement step is preferably a step of placing a water vapor adsorption suppression material along the contours of the formed pellet deposit and the deposit in the process of being stacked. In this case, it is preferable that the water vapor adsorption suppression material is placed in an area ratio of 70% to 100% of the total exposed area of ​​the formed pellet deposit. This area ratio is more preferably 80% to 100%, and even more preferably 90% to 100%. Similarly, it is preferable that the water vapor adsorption suppressing material is arranged in an area ratio of 70% to 100% of the total exposed area of ​​the deposits being piled up. More preferably, this area ratio is 80% to 100%, and even more preferably 90% to 100%.

[0054] In the storage method according to this embodiment, it is also preferable that the water vapor adsorption suppressing material be arranged horizontally to the bottom surface of the pellet stack in the process of being piled up. In this case, it is preferable that the water vapor adsorption suppressing material be arranged in an area ratio of 70% to 100% of the total horizontal exposed area of ​​the stack in the process of being piled up. More preferably, this area ratio is 80% to 100%, and even more preferably 90% to 100%. Furthermore, when the water vapor adsorption suppressing material is arranged horizontally to the bottom surface of the pellet stack in the process of being piled up, it is preferable that the water vapor adsorption suppressing material be arranged at intervals of 0.5 m to 5.0 m from the bottom surface of the pellet stack towards the top, and more preferably at intervals of 1.0 m to 5.0 m.

[0055] In the storage method according to this embodiment, if the suppression material placement step includes a step of placing a water vapor adsorption suppression material on the surface of a pile that is being stacked, a pellet pile can be obtained by further stacking pellets on top of the placed water vapor adsorption suppression material (see the second and third examples of the storage method described later). As a "means for further stacking pellets on top of the placed water vapor adsorption suppressing material," the same means as the "means for forming a pellet deposit" described above can be used.

[0056] <After the sediment formation process has been completed> In one embodiment of the storage method according to this embodiment, after the deposition process is carried out, the pellet deposition has a pellet-dry region mainly composed of pellets with a moisture content of less than 6% by mass, and a pellet-wet region mainly composed of pellets with a moisture content of 6% by mass or more. In this specification, the main component means a component whose proportion to the total mass of the target area is 50% by mass or more. The moisture content of the pellet can be measured by known methods. In one embodiment of the storage method according to this embodiment, the pellet drying region is a region that occurs on the surface side of the pellet deposit when the moisture content of the pellets present in the surface layer of the pellet deposit becomes lower than the moisture content of the pellets immediately after the formation of the pellet deposit. The pellet-wet region is an area where the moisture content of the pellets does not change easily immediately after the formation of the pellet deposit, and specifically, it is an area that occurs towards the inner side of the pellet deposit.

[0057] In the storage method according to this embodiment, the area that may become a pellet-wet region is preferably 30% to 90% of the total volume of the pellet deposit. In one embodiment of the storage method according to this embodiment, the water vapor adsorption suppressing material is arranged to cover at least a portion of the area that may become a pellet wet area. In one embodiment of the storage method according to this embodiment, the water vapor adsorption suppressing material is arranged to cover at least a portion of the area that may become a pellet drying area. In one embodiment of the storage method according to this embodiment, the water vapor adsorption suppressing material is arranged to cover the areas that may become pellet wet regions and the areas that may become pellet dry regions, respectively.

[0058] Figure 5 illustrates a first example of the storage method according to this embodiment. Figure 5 shows a pellet storage facility 1. The storage facility 1 includes a first stacker 60A and a second stacker 60B. The first stacker 60A is an example of a means for forming a pellet deposit, and the second stacker 60B is an example of a means for arranging a water vapor adsorption suppression material. In the case of Figure 5, the water vapor adsorption suppression material is coated pellets 20. The pellets 10 are piled up on the ground. The first stacker 60A comprises a main body 61A and a supply unit 62A for supplying pellets 10. The second stacker 60B comprises a main body 61B and a supply unit 62B for supplying coated pellets 20. In storage facility 1, the pellets 10 are stored, for example, as follows: First, the first stacker 60A forms the first deposit 100a by supplying pellets 10 from the supply unit 62A toward the ground. Next, the second stacker 60B places the coated pellets 20 from the supply unit 62B onto the surface (exposed surface) of the first deposit 100a, following the contour of the first deposit 100a. This ultimately forms the second deposit 100b as a pellet deposit. The height of the second deposit, 100b, is, for example, between 1m and 30m.

[0059] In Figure 5, pellet deposit 100 schematically shows the state after a certain period of time has elapsed since the formation of the second deposit 100b using the method of the first example. As a result of the aforementioned event (1), the pellet deposit 100 has a pellet-drying region DR2 on the surface side and a pellet-wet region WR2 on the inner side.

[0060] According to the storage method of the first example, water vapor that moves from the back to the surface of the pellet deposit 100 is less likely to be adsorbed by the coated pellets 20. As a result, the water vapor is either trapped in the back or diffused into the atmosphere through the gaps in the coated pellets 20, suppressing the generation of heat of adsorption. This makes it less likely for events (3) through (5) described above to occur, even when water vapor moves from the back to the surface of the pellet deposit 100. According to the storage method described in the first example, spontaneous combustion of pellets can be suppressed when they are stored. Furthermore, according to the storage method described in the first example, the effect can be observed even when large quantities of pellets are stored.

[0061] (Second example of storage method) Figure 6 illustrates a second example of the storage method according to this embodiment. Figure 6 shows the pellet storage facility 1A. Storage facility 1A has the same configuration as storage facility 1 in the first example. The storage method for the second example using storage facility 1A is the same as the storage method for the first example, except that the coated pellets 20 are placed horizontally on the ground, the coated pellets 20 are placed twice on the piles that are being stacked, and the pellets 10 are stacked in a truncated cone shape until the second set of coated pellets 20 are placed. As shown in Figure 6, in the storage method of the second example, the first sediment 101a, the second sediment 101b, the third sediment 101c, and the fourth sediment 101d are formed in order, and finally the fifth sediment 101e is obtained as a pelletized sediment. The coated pellets 20 are placed on the horizontally exposed surfaces of the first sediment 101a and the third sediment 101c with respect to their respective bottom surfaces (ground).

[0062] In Figure 6, pellet deposit 101 schematically shows the state after a certain period of time has elapsed since the formation of the fifth deposit 101e using the method of the second example. As a result of the aforementioned event (1), the pellet deposit 101 has a pellet-drying region DR3 on the surface side and a pellet-wet region WR3 on the inner side. In the pellet deposit 101, the coated pellets 20 are arranged at intervals D1 from the top T1 to the bottom B1 of the pellet deposit 101. The interval D1 is preferably 0.5m or more and 5.0m or less.

[0063] According to the storage method of the second example, by placing coated pellets 20 on the horizontal surfaces of the first deposit 101a and the third deposit 101c, respectively, during the stacking of pellets 10, water vapor generated in the deeper part of the pellet deposit 101 is less likely to be adsorbed by the coated pellets 20. As a result, the water vapor tends to remain near where the coated pellets 20 are placed, and consequently, the movement of water vapor from the deeper part of the pellet deposit 101 to the surface is suppressed. According to the storage method described in the second example, spontaneous combustion of pellets can be suppressed when they are stored. Furthermore, according to the storage method described in the second example, the effect can be observed even when large quantities of pellets are stored.

[0064] (Example 3 of storage methods) Figure 7 illustrates a third example of the storage method according to this embodiment. In the third example, we will describe an example in which pellets 10 and coated pellets 20 (an example of a water vapor adsorption suppression material) are stacked alternately inside a silo 40. The capacity of a silo 40 is typically between 10 tons and 10,000 tons. Figure 7 shows the pellet storage facility 1B. The storage facility 1B includes a silo 40 for storing pellets 10, a first conveyor 31 for transporting pellets 10 and loading them into the silo 40, a second conveyor 32 for transporting coated pellets 20 and loading them into the silo 40, a third conveyor 33, a fourth conveyor 34, and a fifth conveyor 35 for discharging the pellets 10 and coated pellets 20 stored in the silo 40 to the outside of the silo 40. Furthermore, the roof section 40A of the silo 40 is provided with an inlet 42 into which the pellets 10 and coated pellets 20 are fed, and a sprinkler 55 for spraying water into the silo 40 in emergencies as needed. The bottom wall 40B of the silo 40 is provided with an outlet 45 into which the pellets 10 and coated pellets 20 are discharged. Both the inlet 42 and the outlet 45 are configured to be openable and closable. The first conveyor 31 is an example of a means for forming pellet deposits, and the second conveyor 32 is an example of a means for arranging water vapor adsorption suppression material. In storage facility 1B, the first conveyor 31 and the second conveyor 32 are operated in sequence to form a pellet deposit inside the silo 40. First, the first conveyor 31 is operated to load the pellets 10 into the silo 40, thereby forming the first pellet deposit 10a. Next, the second conveyor 32 is operated to load the coated pellets 20 into the silo 40, thereby forming the first coated pellet deposit 20a. Subsequently, by sequentially adding pellets 10 and coated pellets 20 in the same manner, a second pellet deposit 10b and a second coated pellet deposit 20b are formed, and finally a pellet deposit 200a (first pellet deposit 10a, first coated pellet deposit 20a, second pellet deposit 10b, and second coated pellet deposit 20b) is obtained.

[0065] In Figure 7, pellet deposit 200 schematically shows the state after a certain period of time has elapsed since pellet deposit 200a was formed using the third example method. As a result of the aforementioned event (1), the pellet deposit 200 has a pellet-drying region DR4 on the surface side (the side of the second pellet deposit 10b) and a pellet-wet region WR4 on the inner side. The first coated pellet deposit 20a is arranged at intervals D2 from the bottom surface B2 to the top surface T2 of the pellet deposit 200. The interval D2 is preferably 0.5m or more and 5.0m or less.

[0066] In the third example, by placing coated pellets 20 (second coated pellet deposit 20b) on the surface of the pellet deposit 200, water vapor that moves from the inner part of the pellet deposit 200 to the surface is less likely to be adsorbed by the second coated pellet deposit 20b, and the surface of the pellet deposit 200 is less likely to dry out. As a result, it is thought that events (3) through (5) described above are less likely to occur. Furthermore, in the third example, by placing coated pellets 20 (first coated pellet deposit 20a) in the first pellet deposit 10a during the stacking of pellets 10, water vapor generated in the deeper part of the pellet deposit 200 is less likely to be adsorbed by the first coated pellet deposit 20a. As a result, the water vapor tends to remain near where the first coated pellet deposit 20a is placed, and consequently, the movement of water vapor from the deeper part of the pellet deposit 200 to the surface is thought to be suppressed. According to the storage method described in the third example, spontaneous combustion of pellets can be suppressed when they are stored. Furthermore, according to the storage method described in the third example, the effect can be observed even when large quantities of pellets are stored.

[0067] The storage methods according to this embodiment are not limited to the first to third examples. In the first to third examples, the same means were used for forming the pellet deposit and for arranging the water vapor adsorption suppression material, but different means may be used for each. For example, in the first example, the means for forming the pellet deposit may be a stacker, and the means for arranging the water vapor adsorption suppression material may be an excavator. In the third example, a storage facility 1B having one silo was described, but the storage facility 1B may have multiple silos. In this case, it is preferable that the multiple silos are connected to each other by a conveyor for transporting pellets and a conveyor for transporting water vapor adsorption suppression material.

[0068] [Second Embodiment] [Pellet storage facilities] The pellet storage facility according to the second embodiment comprises means for stacking biomass-derived pellets in a storage area to form a pellet deposit, and means for placing a water vapor adsorption suppressing material in at least a part of the storage area, wherein the storage area is at least one of the ground, a silo, a warehouse, and a container, and the water vapor adsorption suppressing material is means for suppressing the adsorption of water vapor onto the pellets. The water vapor adsorption suppression material is preferably one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. The storage equipment according to the second embodiment is, for example, the storage equipment 1, 1A, and 1B shown in Figures 5 to 7.

[0069] According to the storage facility of the second embodiment, by providing means for arranging a water vapor adsorption suppression material, the movement of water vapor from the back of the pellet deposit to the surface can be suppressed. As a result, spontaneous combustion can be suppressed when pellets are stored. The storage equipment according to the second embodiment is used, for example, when implementing the storage method of the first embodiment described above. Therefore, the water vapor adsorption suppressing material, the means for arranging the water vapor adsorption suppressing material, etc., used in the storage equipment according to the second embodiment can be the same as those used in the first embodiment.

[0070] The configurations common to the embodiments described above will now be explained.

[0071] <Biomass> In the storage method according to this embodiment, the pellet is preferably at least one selected from the group consisting of woody biomass pellets, herbaceous biomass pellets, crop residue biomass pellets, and palm oil biomass pellets, and is more preferably woody biomass pellets. The pellets may include woody biomass, herbaceous biomass, crop residue biomass, and palm biomass, as well as cellulose products and pulp products.

[0072] In this specification, agricultural crop residue biomass means anything other than the edible portion. In this specification, palm biomass means agricultural waste from palm trees.

[0073] Examples of woody biomass include coniferous trees (e.g., Japanese cedar, pine, cypress, and fir) and broad-leaved trees (e.g., acacia, eucalyptus, birch, black locust, beech, zelkova, katsura, paulownia, rubber tree, and camphor tree). Woody biomass may also include construction waste (e.g., cut scraps, wood chips and sawdust generated at processing plants), forest residues, thinned timber, and bamboo. Examples of herbaceous biomass include grass, naturally growing plants, and artificially planted plants. Herbaceous biomass may also include hemp, cotton, rice straw, rice husks, wheat straw, bamboo grass, Napier grass, sorghum, and Japanese pampas grass.

[0074] Examples of agricultural crop residue biomass include leaves, fruit clusters, stems, roots, and other non-edible parts of crops. Examples of such crops include wheat, corn, potatoes, sugarcane (including bagasse), and bananas.

[0075] Examples of palm oil biomass include palm kernel shells (PKS), empty fruit bunches (EFB), and palm trunks. The biomass described above may be used individually or in combination of two or more types.

[0076] In this embodiment, the semi-carbonized pellets have a high proportion of fixed carbon. The proportion of fixed carbon is the value of fixed carbon determined by industrial analysis. The industrial analysis value is measured in accordance with JIS M8812 (2004). The proportion of fixed carbon (by mass) in the semi-carbonized pellets is preferably 20% or more, more preferably 20% to 40%, and even more preferably 20% to 35%.

[0077] In this embodiment, the pellets are typically cylindrical, preferably with a diameter of 5 mm to 10 mm and a length of 5 mm to 50 mm. In this embodiment, the pellets include briquettes. Briquettes are typically cylindrical, tablet-shaped, charcoal-shaped, cubic, or rectangular, and a volume of 1 mL to 1 L is convenient for use.

[0078] In this embodiment, the pellets may contain other components. Examples of other components include emulsifiers, spreading agents, binders, and various additives. In this embodiment, the pellets may contain coal. If the pellets contain coal, the ratio of coal to biomass in the pellets (coal / biomass) is preferably 0 / 100 to 75 / 25 by mass ratio, and more preferably 0 / 100 to 50 / 50.

[0079] In this embodiment, the pellets can be widely used as fuel in power plants, steel mills, factories, and the like. [Explanation of Symbols]

[0080] 1,1A,1B...Storage equipment, 10...Pellets, 10a...First pellet deposit, 10b...Second pellet deposit, 20...Coated pellets, 31~35...Conveyor, 40...Silo, 40A...Roof section, 40B...Bottom wall, 42...Inlet, 44...Gas preheating section, 45...Outlet, 46...Temperature controller, 50...Constant temperature bath, 52...Sample, 53...Thermocouple, 55...Sprinkler, 60A,60B...Stacker, 61A,6 1B...Main body, 62A, 62B...Supply unit, 64...Gas supply pipe, 66...Gas discharge pipe, 62A...Supply unit, 70A...Reactor, 72A...Lid, 74, 75...Quartz wool, 80...Gas supply unit, 82...Gas flow meter, 84...Humidifier, 86...Hygrometer, 91~94...Flow path, 100, 101, 200, 200a...Pellet deposit, 100a~100b, 101a~101e...Deposit, 300...Spontaneous exothermic testing device.

Claims

1. A method for storing pellets, A sediment formation process involves stacking biomass-derived pellets to form a pellet deposit, The process includes a step of placing a water vapor adsorption suppressing material on the surface of at least one of the formed pellet deposits and the deposits in the process of stacking the pellets, The water vapor adsorption suppressing material is a material that suppresses the adsorption of water vapor generated from the pellet deposit. How to store pellets.

2. The aforementioned suppression material placement step is a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit, The method for storing pellets according to claim 1.

3. The aforementioned suppression material placement step is a step of placing a water vapor adsorption suppression material on the surface of the formed pellet deposit and on the surface of the deposit in the process of stacking the pellets. A method for storing pellets according to claim 1 or claim 2.

4. If the suppression material placement step includes a step of placing a water vapor adsorption suppression material on the surface of the deposits in the process of stacking the pellets, The aforementioned suppression material placement step is performed two or more times during the stacking process. A method for storing pellets according to any one of claims 1 to 3.

5. The aforementioned suppression material placement step is a step of placing the water vapor adsorption suppression material along the contours of the formed pellet deposit and the deposit in the process of being piled up. A method for storing pellets according to any one of claims 1 to 4.

6. The water vapor adsorption suppressing material is one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. A method for storing pellets according to any one of claims 1 to 5.

7. The hydrophobic substance is one or more selected from the group consisting of heavy oil, light oil, petroleum-based residue oil, vegetable oil, waste plastic oil, waste tire oil, and biotar. The method for storing pellets according to claim 6.

8. The aforementioned hydrophobic substance is a vegetable oil. The method for storing pellets according to claim 7.

9. The aforementioned pellet piles are at least one of the following: pellet piles piled up in the open, pellet piles piled up in silos and warehouses, and pellet piles piled up in containers. A method for storing pellets according to any one of claims 1 to 8.

10. The aforementioned pellet is at least one selected from the group consisting of woody biomass pellets, herbaceous biomass pellets, crop residue biomass pellets, and palm oil biomass pellets. A method for storing pellets according to any one of claims 1 to 9.

11. The aforementioned pellets are wood-based biomass pellets. The method for storing pellets according to claim 10.

12. A pellet storage facility, A means of stacking biomass-derived pellets in a storage area to form a pellet deposit, The storage area comprises means for placing a water vapor adsorption suppressing material in at least a portion of the storage area, The aforementioned storage location is at least one of the following: open storage, silos, warehouses, and containers. The water vapor adsorption suppressing material is a means for suppressing the adsorption of water vapor generated from the pellet deposit. Pellet storage facility.

13. The water vapor adsorption suppressing material is one or more selected from the group consisting of coated pellets coated with a hydrophobic substance and hydrophobic substances. A pellet storage apparatus according to claim 12.

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