Biochar production system and biochar production method

Abstract

To provide a biochar production system and biochar production method that can produce biochar of higher quality while suppressing carbon dioxide emissions, even when producing biochar from biomass with a high moisture content. [Solution] The biochar production system 1 comprises a drying section 33 for drying high-moisture biomass, a high-moisture biomass carbonization section 34 for carbonizing the high-moisture biomass dried in the drying section 33, and a low-moisture biomass carbonization section 24 for carbonizing low-moisture biomass, which has a lower moisture content than high-moisture biomass, separately from the high-moisture biomass. The drying section 33 uses the pyrolysis gas generated in the low-moisture biomass carbonization section 24 to dry and / or carbonize the high-moisture biomass. The pyrolysis gas generated in the low-moisture biomass carbonization section 24 is used for drying the high-moisture biomass by the drying section 33 and / or for carbonizing the high-moisture biomass by the high-moisture biomass carbonization section 34.

Description

Technical Field

[0001] The present invention relates to a biochar production system and a biochar production method.

Background Art

[0002] Conventionally, a technique for producing biochar, which is a carbide of biomass, has been known. Since biochar has the effect of storing carbon dioxide, it is useful for reducing carbon dioxide in the atmosphere. In addition, biochar has the effect of improving physical properties of soil such as water permeability, water retention, and air permeability, and by using it in agriculture and the like, improvement of crop growth and increase in yield can be expected.

[0003] As a document describing a technique related to the production of biochar, for example, there is Patent Document 1. Patent Document 1 describes a technique of heating and drying woody biomass using a heat medium and carbonizing the dried woody biomass by pyrolysis.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, as described in Patent Document 1, the carbonization of biomass requires heating the biomass at low oxygen concentrations and high temperatures. When producing biochar from biomass with a high moisture content, a significant amount of heat is consumed in drying the biomass, requiring even more heat for carbonization. For this reason, fossil fuels such as kerosene are sometimes used to obtain the heat necessary for carbonizing high-moisture biomass. Although biochar that stores carbon dioxide is produced, the use of fossil fuels in its production results in the emission of carbon dioxide. In some cases, high-moisture biomass is mixed with low-moisture biomass for carbonization, but since the suitable carbonization conditions differ between high-moisture and low-moisture biomass, the quality of the biochar tends to deteriorate.

[0006] The present invention aims to provide a biochar production system and a biochar production method that can produce biochar of higher quality while suppressing carbon dioxide emissions, even when producing biochar from biomass with a high moisture content. [Means for solving the problem]

[0007] (1) The biochar production system is a biochar production system for producing biochar of a first biomass having a predetermined moisture content, comprising: a drying section for drying the first biomass; a first carbonization section for carbonizing the first biomass dried in the drying section; and a second carbonization section for carbonizing a second biomass having a lower moisture content than the first biomass separately from the first biomass, wherein the pyrolysis gas generated in the second carbonization section is used for drying the first biomass by the drying section and / or for carbonizing the first biomass by the first carbonization section.

[0008] (2) The biochar production system described in (1) further includes a preheating unit that preheats the second biomass before it is carbonized by the second carbonization unit, and utilizes the pyrolysis gas generated in the first carbonization unit for preheating the second biomass by the preheating unit.

[0009] (3) A biochar production method is a biochar production method for producing biochar of a first biomass having a predetermined moisture content, comprising: a drying step of drying the first biomass; a first carbonization step of carbonizing the first biomass dried in the drying step; and a second carbonization step of carbonizing a second biomass having a lower moisture content than the first biomass separately from the first biomass, wherein the pyrolysis gas generated in the second carbonization step is used for drying the first biomass in the drying step and / or carbonizing the first biomass in the first carbonization step.

[0010] (4) The biochar production method described in (3) further includes a preheating step of preheating the second biomass before the second carbonization step, wherein the pyrolysis gas generated in the first carbonization step is used to preheat the second biomass in the preheating step. [Effects of the Invention]

[0011] According to the present invention, even when producing biochar from biomass with a high moisture content, it is possible to obtain biochar of higher quality while suppressing carbon dioxide emissions. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing a biochar production system according to the first embodiment. [Figure 2A] This figure shows the relationship between the processing volume of low-moisture biomass, carbonization temperature, combustion site temperature, and waste heat. [Figure 2B] Figure 2A shows a table illustrating the various conditions for carbonization of high-moisture biomass supplied with waste heat, and whether or not carbon neutralization is possible. [Figure 3] This is a flowchart showing the procedure for the biochar production method according to the first embodiment. [Figure 4] This is a schematic diagram showing a biochar production system according to the second embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0014] The biochar production system 1 according to the first embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing the biochar production system 1.

[0015] The biochar production system 1 according to the present embodiment separately carbonizes a first biomass with a predetermined moisture content (hereinafter referred to as high-moisture biomass) and a second biomass with a lower moisture content than the first biomass (hereinafter referred to as low-moisture biomass), and produces biochar that is a carbide of high-moisture biomass (hereinafter referred to as high-moisture-derived biochar) and biochar that is a carbide of low-moisture biomass (hereinafter referred to as low-moisture-derived biochar).

[0016] The biochar production system 1 is a system that can reduce the amount of carbon dioxide emitted during the carbonization of high-moisture biomass by using the pyrolysis gas generated during the carbonization of low-moisture biomass for the production of high-moisture-derived biochar.

[0017] The moisture content of the high-moisture biomass is preferably 60% to 80% by mass. Examples of the high-moisture biomass include wood chips, food residues generated in food factories, livestock manure, and sewage sludge.

[0018] The moisture content of the low-moisture biomass is preferably 10% to 20% by mass. Examples of the low-moisture biomass include rice husks, straws such as rice and wheat, and nut shells such as palm nuts.

[0019] The biochar production system 1 includes a low-moisture-derived biochar production unit 2, a high-moisture-derived biochar production unit 3, a heat transfer mechanism 4, and a control device 5.

[0020] The low-moisture-derived biochar production unit 2 includes a low-moisture biomass supply unit 21, a low-moisture-derived biochar production unit 20, a low-moisture-derived biochar recovery unit 22, an exhaust heat recovery boiler 26, and an exhaust duct (not shown).

[0021] The low-moisture biomass supply unit 21 supplies low-moisture biomass to the low-moisture-derived biochar production unit 20. The low-moisture biomass supply unit 21 has a hopper 211 in which low-moisture biomass is stored, and a conveyor 212 that supplies the low-moisture biomass discharged from the hopper 211 to the low-moisture-derived biochar production unit 20. The supply amount of the low-moisture biomass from the low-moisture biomass supply unit 21 to the low-moisture-derived biochar production unit 20 may be controlled by the control device 5.

[0022] The low-moisture-derived biochar production unit 20 is a device that produces low-moisture-derived biochar, which is a carbide of low-moisture biomass. As shown in FIG. 1, the low-moisture-derived biochar production unit 20 has a cylindrical main body 200. The low-moisture biomass supplied from the low-moisture biomass supply unit 21 is introduced into one side (the left side in FIG. 1) in the axial direction (hereinafter also referred to as the axial direction X) of the main body 200, and is transferred toward the other side (the right side in FIG. 1) while being heated.

[0023] The means for transferring the low-moisture biomass in the low-moisture-derived biochar production unit 20 is not particularly limited. For example, the low-moisture biomass may be transferred by a conveyor provided in the main body 200, or a plurality of fins, spirals, etc. may be provided on the inner peripheral surface of the main body 200, and the main body 200 may be rotated to transfer it.

[0024] Note that only low-moisture biomass is supplied to the low-moisture-derived biochar production unit 20, and high-moisture biomass is not supplied. That is, only the second biochar is produced in the low-moisture-derived biochar production unit 20. Therefore, only biomass with the same moisture content or the same type of biomass is carbonized, so it can be uniformly carbonized at a temperature suitable for the biomass, with little variation in characteristics and structure, and higher-quality biochar can be produced.

[0025] The low-moisture biochar production unit 20 includes a preheating unit 23, a low-moisture biomass carbonization unit (second carbonization unit) 24, and a combustion unit 25, each located in one of three regions that divide the main body 200 in the axial direction X. As shown in Figure 1, the preheating unit 23, the low-moisture biomass carbonization unit 24, and the combustion unit 25 are located in this order from one side to the other of the main body 200. The preheating unit 23, the low-moisture biomass carbonization unit 24, and the combustion unit 25 are interconnected and configured to allow air and gas to flow across their respective regions.

[0026] The preheating unit 23 preheats the low-moisture biomass supplied from the low-moisture biomass supply unit 21 to a predetermined temperature. The predetermined temperature is preferably, for example, the ambient temperature at startup of the device to about 100°C, and more preferably, a temperature that can preheat the low-moisture biomass to just before the evaporation of water contained in the low-moisture biomass begins. The generation of pyrolysis gas varies depending on the biomass composition, such as the content of cellulose, semicellulose, lignin, etc., contained in the biomass, but it starts at about 200°C. The temperature at the boundary between the preheating unit 23 and the low-moisture biomass carbonization unit 24 may be, for example, 200°C.

[0027] The preheating unit 23 preheats the low-moisture biomass mainly using heat generated by electricity supplied to the biochar production system 1 from an external source and heat from pyrolysis gas returned from the combustion unit 25, which will be described later. The preheating unit 23 may also be configured to preheat the low-moisture biomass by utilizing heat transferred from the high-moisture biochar production unit 3.

[0028] Furthermore, the electricity supplied to the biochar production system 1 is preferably electricity generated using renewable energy sources such as wind or solar power, in order to reduce carbon dioxide emissions associated with biochar production.

[0029] The low-moisture biomass carbonization section 24 further heats the low-moisture biomass preheated in the preheating section 23, and carbonizes it by thermal decomposition to produce low-moisture biochar. The produced low-moisture biochar is transferred to the low-moisture biochar recovery section 22. The thermal decomposition gas generated by the carbonization of the low-moisture biomass is supplied to the combustion section 25.

[0030] Furthermore, since the area where low-moisture biomass is preheated in the open, interconnected space within the cylindrical main body 200 becomes the preheating section 23, and the area where low-moisture biomass is carbonized becomes the low-moisture biomass carbonization section 24, the boundary between the preheating section 23 and the low-moisture biomass carbonization section 24 in the axial direction X does not need to be clearly defined. In other words, the preheating section 23 and the low-moisture biomass carbonization section 24 are not clearly distinguished in terms of the device configuration.

[0031] The low-moisture biomass carbonization section 24 is maintained at a predetermined carbonization temperature and oxygen concentration necessary for carbonizing low-moisture biomass. The carbonization temperature is preferably around 350°C to 1000°C, although this depends on the desired quality of the low-moisture biochar and the acceptable carbonization time.

[0032] Here, if the carbonization temperature of biomass is high, thermal decomposition occurs actively, reducing the yield of biochar. On the other hand, thermal decomposition releases hydrogen and oxygen, improving the carbon ratio, which is the proportion of carbon in the remaining biochar. As the proportion of solid carbon in the so-called carbonized state increases, the long-term retention rate of carbon in the soil increases when applied to farmland. It also shortens the time required for carbonization. Conversely, if the carbonization temperature is low, the time required for carbonization increases, the carbonization rate decreases, and when applied to farmland, decomposition by microorganisms in the soil becomes more likely, resulting in a low long-term retention rate of carbon in the soil. For these reasons, when applying low-moisture-content biochar to farmland, a carbonization temperature of around 600°C to 800°C is preferable.

[0033] Methods for carbonizing low-moisture biomass within the low-moisture biomass carbonization section 24 include a method in which a portion of the low-moisture biomass is spontaneously combusted and the heat generated by this combustion is used to carbonize other low-moisture biomass, and a method in which the low-moisture biomass is not spontaneously combusted.

[0034] When a portion of the low-moisture biomass is to be spontaneously combusted, the amount of oxygen necessary for the spontaneous combustion of the low-moisture biomass may be supplied, and after the oxygen consumption due to spontaneous combustion, carbonization may be carried out in a vegan state (for example, with an oxygen content of about 5 vol% or less, preferably 1 vol% or less) within the low-moisture biomass carbonization section 24. In this case, during normal operation, the low-moisture biomass carbonization section 24 mainly uses the heat obtained from the spontaneous combustion of a portion of the low-moisture biomass within the low-moisture biomass carbonization section 24 and the combustion of pyrolysis gas in the combustion section 25, and, if necessary, the heat generated by electricity supplied to the biochar production system 1 from the outside to carbonize the low-moisture biomass.

[0035] If the low-moisture biomass is not allowed to spontaneously combust in the low-moisture biomass carbonization section 24, carbonization may be carried out in an oxygen-rich state as much as possible within the low-moisture biomass carbonization section 24. In this case, during normal operation, the low-moisture biomass carbonization section 24 carbonizes the low-moisture biomass mainly using heat obtained from the combustion of pyrolysis gas in the combustion section 25, and, if necessary, heat generated by electricity supplied to the biochar production system 1 from the outside. Note that if the low-moisture biomass is not allowed to spontaneously combust, oxygen is not required in the low-moisture biomass carbonization section 24 except to secure the heat required for carbonization.

[0036] The combustion unit 25 has a combustion furnace 251 as a combustion field and an air supply unit (not shown), and burns the pyrolysis gas supplied from the low-moisture biomass carbonization unit 24 to the combustion furnace 251. The combustion unit 25 supplies the air necessary for the combustion of the pyrolysis gas to the combustion furnace 251 from the air supply unit. The pyrolysis gas burned in the combustion furnace 251 becomes hotter than the pyrolysis gas before combustion and is sent to the high-moisture biochar production unit 3 via the heat transfer mechanism 4 described later, and is used for the production of high-moisture biochar. In addition, a portion of the burned pyrolysis gas is returned from the combustion furnace 251 to the low-moisture biomass carbonization unit 24 and the preheating unit 23, and after being used to heat the low-moisture biomass in the low-moisture biomass carbonization unit 24, it is sent to the waste heat recovery boiler 26. In this embodiment, a portion of the burned pyrolysis gas is sent to the high-moisture biochar production unit 3 via the heat transfer mechanism 4 described later, and is also used for the production of high-moisture biochar.

[0037] In the waste heat recovery boiler 26, steam is generated by heat exchange between the supplied pyrolysis gas exhaust and circulating water. The generated steam is used for power generation, etc. The exhaust gas discharged from the waste heat recovery boiler 26 is discharged to the outside through an exhaust duct (not shown).

[0038] The high-moisture-derived biochar production unit 3 will now be described. The high-moisture-derived biochar production unit 3 comprises a high-moisture-derived biomass supply unit 31, a high-moisture-derived biochar production unit 30, a high-moisture-derived biochar recovery unit 32, a waste heat recovery boiler 36, and an exhaust duct (not shown).

[0039] The high-moisture biomass supply unit 31 supplies high-moisture biomass to the high-moisture biochar production unit 30. The high-moisture biomass supply unit 31 includes a hopper 311 for storing high-moisture biomass and a conveyor 312 for supplying the high-moisture biomass discharged from the hopper 311 to the high-moisture biochar production unit 30. The amount of low-moisture biomass supplied from the high-moisture biomass supply unit 31 to the high-moisture biochar production unit 30 may be controlled by the control device 5.

[0040] The high-moisture biochar production unit 30 is a device for producing high-moisture biochar, which is a carbonized product of high-moisture biomass. As shown in Figure 1, the high-moisture biochar production unit 30 has a cylindrical main body 300. The main body 300 is arranged in parallel with the main body 200 in a direction perpendicular to the axial direction of the main body 200 (hereinafter referred to as the orthogonal direction Y). The axial directions of the main body 300 and the main body 200 are substantially the same, and they are arranged to be close to each other. The high-moisture biomass supplied from the high-moisture biomass supply unit 31 is introduced into the other side of the axial direction X (right side in Figure 1), heated, and transported toward one side (left side in Figure 1). That is, the biochar production system 1 of this embodiment is configured such that the direction in which high-moisture biomass is transported within the main body 300 of the high-moisture biochar production unit 30 is opposite to the direction in which low-moisture biomass is transported within the main body 200 of the low-moisture biochar production unit 20.

[0041] The means for transporting high-moisture biomass in the high-moisture biochar production section 30 are not particularly limited. For example, high-moisture biomass may be transported by a conveyor installed inside the high-moisture biochar production section 30, or it may be transported by rotating the cylindrical portion of the high-moisture biochar production section 30 by providing multiple fins or spirals on the inner surface of the high-moisture biochar production section 30.

[0042] Furthermore, only high-moisture biomass is supplied to the high-moisture biochar production unit 30; low-moisture biomass is not supplied. In other words, the high-moisture biochar production unit 30 produces only high-moisture biochar. Therefore, since only biomass with similar moisture content is carbonized, it can be carbonized uniformly at a temperature suitable for the biomass, resulting in less variation in properties and structure, and enabling the production of higher-quality biochar.

[0043] The high-moisture biochar production unit 30 includes a drying unit 33, a high-moisture biomass carbonization unit (first carbonization unit) 34, and a combustion unit 35, each located in one of three regions that divide the main body 300 in the axial direction X. As shown in Figure 1, the drying unit 33, the high-moisture biomass carbonization unit 34, and the combustion unit 35 are arranged in this order from one side to the other of the main body 300. The drying unit 33, the high-moisture biomass carbonization unit 34, and the combustion unit 35 are interconnected, and are configured to allow air and gas to flow across their respective regions.

[0044] The drying section 33 dries the high-moisture biomass supplied from the high-moisture biomass supply section 31. The temperature inside the drying section 33 is preferably, for example, 100°C or higher. If it is desired to suppress the generation of pyrolysis gas in the drying section 33, the temperature inside the drying section 33 is preferably 100°C to 200°C. The temperature at the boundary between the drying section 33 and the high-moisture biomass carbonization section 34 may be, for example, 200°C. The drying section 33 dries the low-moisture biomass mainly using heat generated by electricity supplied to the biochar production system 1 from the outside, or heat transferred from the low-moisture biochar production unit 2 via the heat transfer mechanism 4.

[0045] The high-moisture biomass carbonization section 34 heats the high-moisture biomass dried in the drying section 33 and carbonizes it through thermal decomposition to produce high-moisture biochar. The produced high-moisture biochar is transferred to the high-moisture biochar recovery section 32. The thermal decomposition gas generated by the carbonization of the high-moisture biomass is supplied to the combustion section 35.

[0046] Furthermore, since the area where low-moisture biomass is dried in the open, interconnected space within the cylindrical main body 300 becomes the drying section 33, and the area where high-moisture biomass is carbonized becomes the high-moisture biomass carbonization section 34, the boundary between the drying section 33 and the high-moisture biomass carbonization section 34 in the axial direction X does not need to be clearly defined. In other words, the drying section 33 and the high-moisture biomass carbonization section 34 are not clearly distinguished in terms of the device configuration.

[0047] The high-moisture biomass carbonization section 34 is maintained at a predetermined carbonization temperature and oxygen concentration necessary for carbonizing high-moisture biomass. The carbonization temperature is preferably around 350°C to 1000°C, although this depends on the desired quality of the high-moisture biomass and the acceptable carbonization time. For example, when applying high-moisture biomass to farmland, the carbonization temperature is preferably around 600°C to 800°C, similar to low-moisture biomass.

[0048] Methods for carbonizing high-moisture biomass within the high-moisture biomass carbonization section 34 include a method in which a portion of the high-moisture biomass is spontaneously combusted and the heat generated by this combustion is used to carbonize other high-moisture biomass, and a method in which the high-moisture biomass is not spontaneously combusted.

[0049] When a portion of high-moisture biomass is to be spontaneously combusted, the amount of oxygen necessary for the spontaneous combustion of the high-moisture biomass may be supplied, and after oxygen consumption due to spontaneous combustion, carbonization may be carried out in a vegan state (for example, with an oxygen content of about 5 vol% or less, preferably 1 vol% or less) within the high-moisture biomass carbonization section 34. In this case, during normal operation, the high-moisture biomass carbonization section 34 carbonizes the high-moisture biomass mainly using the heat obtained from the spontaneous combustion of a portion of the high-moisture biomass within the high-moisture biomass carbonization section 34 and the combustion of pyrolysis gas in the combustion section 35, and, if necessary, the heat generated by electricity supplied to the biochar production system 1 from the outside. When high-moisture biomass is spontaneously combusted, the high-moisture biomass is pre-adjusted in the drying section 33 to a moisture content that allows for spontaneous combustion, for example, a moisture content similar to that of low-moisture biomass.

[0050] If the high-moisture biomass is not allowed to spontaneously combust in the high-moisture biomass carbonization section 34, carbonization may be carried out in a state of oxygen saturation as much as possible within the high-moisture biomass carbonization section 34. In this case, during normal operation, the high-moisture biomass carbonization section 34 carbonizes the high-moisture biomass mainly using heat obtained from the combustion of pyrolysis gas in the combustion section 35, and, if necessary, heat generated by electricity supplied to the biochar production system 1 from the outside.

[0051] The combustion unit 35 includes a combustion furnace 351 and an air supply unit (not shown), and burns the pyrolysis gas supplied from the high-moisture biomass carbonization unit 34 to the combustion furnace 351. The combustion unit 35 supplies the air necessary for the combustion of the pyrolysis gas to the combustion furnace 351 from the air supply unit. The pyrolysis gas burned in the combustion furnace 351 becomes hotter than the pyrolysis gas before combustion and is returned from the combustion furnace 351 to the high-moisture biomass carbonization unit 34 and the drying unit 33. After the heat of the burned pyrolysis gas is consumed to heat the high-moisture biomass in the high-moisture biomass carbonization unit 34 and the drying unit 33, it is sent to the waste heat recovery boiler 36. In this embodiment, a portion of the burned pyrolysis gas is sent to the low-moisture biochar production unit 2 via a heat transfer mechanism 4 (described later) and is also used for the production of low-moisture biochar.

[0052] In the waste heat recovery boiler 36, steam is generated by heat exchange between the supplied pyrolysis gas exhaust and circulating water. The generated steam is used for power generation, etc. The exhaust gas discharged from the waste heat recovery boiler 36 is discharged to the outside through an exhaust duct.

[0053] Next, the heat transfer mechanism 4 will be described. The heat transfer mechanism 4 is a mechanism for exchanging heat between the low-moisture biochar production unit 2 and the high-moisture biochar production unit 3. The heat transfer mechanism 4 in this embodiment has a first heat transfer mechanism 41 and a second heat transfer mechanism 42.

[0054] The first heat transfer mechanism 41 transfers heat from the pyrolysis gas in the low-moisture biomass carbonization section 24 to the high-moisture biochar production unit 3. In this embodiment, the first heat transfer mechanism 41 is connected to the combustion furnace 251 and is a gas flow path such as piping that supplies the pyrolysis gas burned in the combustion furnace 251 to the high-moisture biochar production section 30.

[0055] For example, the first heat transfer mechanism 41 may be configured to transfer heat from the pyrolysis gas burned in the combustion furnace 251 to the drying section 33 by bringing the pyrolysis gas into contact with the outer peripheral wall 301 of the main body 300 on the drying section 33 side. Alternatively, the first heat transfer mechanism 41 may be configured to supply the pyrolysis gas burned in the combustion furnace 251 into the main body 300 on the drying section 33 side. With the first heat transfer mechanism 41, the drying section 33 can dry the first biomass using the pyrolysis gas generated in the low-moisture biomass carbonization section 24.

[0056] Alternatively, for example, the first heat transfer mechanism 41 may be configured to transfer heat from the pyrolysis gas burned in the combustion furnace 251 to the high-moisture biomass carbonization section 34 by bringing the pyrolysis gas burned in the combustion furnace 251 into contact with the outer peripheral wall 301 of the main body 300 on the high-moisture biomass carbonization section 34 side. Alternatively, for example, the first heat transfer mechanism 41 may be configured to supply the pyrolysis gas burned in the combustion furnace 251 into the main body 300 on the high-moisture biomass carbonization section 34 side. With the first heat transfer mechanism 41, the high-moisture biomass carbonization section 34 can carbonize high-moisture biomass using the pyrolysis gas generated in the low-moisture biomass carbonization section 24.

[0057] Alternatively, for example, the first heat transfer mechanism 41 may be configured to transfer heat from the pyrolysis gas, which is burned in the combustion furnace 251, to the drying section 33 and the high-moisture biomass carbonization section 34 by bringing the pyrolysis gas into contact with the outer peripheral wall 301 of the main body 300 on the drying section 33 and high-moisture biomass carbonization section 34 sides. Alternatively, for example, the first heat transfer mechanism 41 may be configured to supply the pyrolysis gas, which is burned in the combustion furnace 251, into the main body 300 on the drying section 33 and high-moisture biomass carbonization section 34 sides. The pyrolysis gas generated in the low-moisture biomass carbonization section 24 by the first heat transfer mechanism 41 can be used for drying the high-moisture biomass by the drying section 33 and for carbonizing the high-moisture biomass by the high-moisture biomass carbonization section 34.

[0058] The second heat transfer mechanism 42 transfers the heat from the pyrolysis gas burned in the combustion section 35 to the low-moisture biochar production unit 2. In this embodiment, the second heat transfer mechanism 42 is a gas flow path such as piping that communicates with the high-moisture biomass carbonization section 34 and supplies the pyrolysis gas burned in the high-moisture biomass carbonization section 34 to the low-moisture biochar production section 20. For example, the second heat transfer mechanism 42 may be configured to transfer the heat from the pyrolysis gas burned in the high-moisture biomass carbonization section 34 to the preheating section 23 by bringing the pyrolysis gas burned in the high-moisture biomass carbonization section 34 into contact with the outer peripheral wall 201 of the main body 200 on the preheating section 23 side. Alternatively, for example, the second heat transfer mechanism 42 may be configured to supply the pyrolysis gas burned in the high-moisture biomass carbonization section 34 into the main body 200 on the preheating section 23 side. The second heat transfer mechanism 42 allows the preheating section 23 to preheat low-moisture biomass using the pyrolysis gas generated in the high-moisture biomass carbonization section 34.

[0059] The control device 5 is an arithmetic unit composed of a processor, which reads various programs and data from the memory unit (not shown) and performs predetermined data processing. The processor is, for example, a CPU (central processing unit), MPU (micro processing unit), SoC (system on a chip), DSP (digital signal processor), GPU (graphics processing unit), VPU (vision processing unit), ASIC (application specific integrated circuit), PLD (programmable logic device), or FPGA (field-programmable gate array).

[0060] The control device 5 is connected to the low-moisture biomass supply unit 21, the high-moisture biomass supply unit 31, the combustion unit 25, and the air supply unit of the combustion unit 35, etc., in a manner that allows communication. Based on the moisture content of the low-moisture biomass and high-moisture biomass to be carbonized, the carbonization temperature required for biochar production, etc., the control device 5 controls the amount of low-moisture biomass supplied to the low-moisture biochar production unit 20, the amount of high-moisture biomass supplied to the high-moisture biochar production unit 30, the amount of air supplied to the combustion furnaces 251 and 351, etc.

[0061] When producing biochar by carbonizing high-moisture biomass, the high water content of the biomass means that a large amount of heat is consumed due to the heat of vaporization of the water, requiring the generation of more heat to produce biochar. For this reason, it is necessary to increase the temperature inside the combustion furnace 351 by introducing fossil fuels such as kerosene, and to raise the temperature of the pyrolysis gas after combustion to a higher temperature. However, the use of fossil fuels increases carbon dioxide emissions.

[0062] On the other hand, when carbonizing low-moisture biomass, the amount of heat consumed due to the heat of vaporization of water is small because the biomass contains less water. Therefore, the biomass can be carbonized with less heat compared to high-moisture biomass. As a result, sufficient heat can be supplied to the low-moisture biomass without introducing fossil fuels into the combustion furnace 251 during steady-state operation, and there is even a tendency for excess heat to be generated.

[0063] In this embodiment, carbonization of high-moisture biomass and low-moisture biomass is performed simultaneously in different devices, and the pyrolysis gas generated from the carbonization of low-moisture biomass is used for drying the high-moisture biomass in the biochar production process. As a result, the heat consumed in drying the high-moisture biomass can be covered by the heat generated by the pyrolysis gas produced in the low-moisture biochar production unit 2, reducing the amount of heat that needs to be generated in the high-moisture biochar production unit 3. Therefore, the amount of carbon dioxide emissions associated with the carbonization of high-moisture biomass can be reduced. This reduction in carbon dioxide emissions increases the likelihood of achieving carbon neutrality, where the amount of carbon dioxide stored by the produced biochar exceeds the amount of carbon dioxide emitted during the biochar production process.

[0064] An example of a simulation of the heat balance when surplus waste heat generated in the production of low-moisture biochar is used in the production of high-moisture biochar will be explained with reference to Figures 2A and 2B. Figure 2A is a diagram showing the relationship between the amount of low-moisture biomass processed, the carbonization temperature, the combustion field temperature, and the waste heat. Figure 2B is a table showing the various conditions for carbonization of high-moisture biomass and the feasibility of carbon neutrality when the surplus heat shown in Figure 2A is supplied. Note that in the simulations shown in Figures 2A and 2B, the heat loss due to the equipment is assumed to be 20%.

[0065] As shown in Figure 2A, when carbonizing rice husks with a moisture content of 15% by mass and a carbonization temperature of 600°C to 800°C at a processing rate of 20 kg / h, the temperature of the combustion field can be raised to 1050°C simply by introducing air into the combustion field. As a result, biochar is produced in proportion to the processing volume, and 36 kJ / s of excess heat is generated.

[0066] When wood chips with a moisture content of 70% by mass are carbonized under the conditions shown in Figure 2B, using the surplus heat supply shown in Figure 2A, if the processing rate is less than or equal to the rice husk processing rate shown in Figure 2A, for example 15 kg / h, it tends to be possible to produce biochar in proportion to the processing rate without inputting fossil fuels such as kerosene into the combustion field, although this depends on the carbonization temperature.

[0067] Next, the biochar production method of this embodiment will be described with reference to Figure 3. Figure 3 is a flowchart showing an example of the procedure for the biochar production method according to this embodiment.

[0068] The biochar production method includes a low-moisture biomass supply step S11, a preheating step S12, a second carbonization step S13, a high-moisture biomass supply step S22, a drying step S23, and a first carbonization step S24. The low-moisture biomass supply step S11, the preheating step S12, and the second carbonization step S13 are steps for producing second biochar and are performed using the low-moisture biochar production unit 2. The high-moisture biomass supply step S22, the drying step S23, and the first carbonization step S24 are steps for producing high-moisture biochar and are performed using the high-moisture biochar production unit 3.

[0069] As shown in Figure 2, in the low-moisture biomass supply process S11, low-moisture biomass is supplied from the hopper 211 of the low-moisture biomass supply unit 21 to the preheating unit 23 of the low-moisture biochar production unit 20.

[0070] In the preheating step S12, the low-moisture biomass supplied to the preheating unit 23 in the low-moisture biomass supply step S11 is preheated to a predetermined temperature. At this time, the pyrolysis gas generated in the first carbonization step S24 may also be used to preheat the low-moisture biomass.

[0071] In the second carbonization step S13, the low-moisture biomass preheated in the preheating step S12 is separated from the high-moisture biomass and carbonized in the low-moisture biomass carbonization section 24. In the second carbonization step S13, the pyrolysis gas generated during the carbonization of the low-moisture biomass is also burned in the combustion section 25 and sent to the high-moisture biochar production unit 3. Subsequently, the process from the low-moisture biomass supply step S11 to the second carbonization step S13 is repeated until the production of the second biochar is completed.

[0072] As part of the process for producing high-moisture biochar, it is first determined whether or not the second carbonization process S13 is in progress (step S21). If the second carbonization process S13 is not in progress (NO in step S21), the process in step S21 is repeated after a predetermined time has elapsed. On the other hand, if the second carbonization process S13 is in progress (YES in step S21), the process moves on to the high-moisture biomass supply process S22.

[0073] In the high-moisture biomass supply process S22, high-moisture biomass is supplied from the hopper 311 of the high-moisture biomass supply unit 31 to the drying unit 33 of the high-moisture biochar production unit 30.

[0074] In the drying process S23, the high-moisture biomass supplied to the drying section 33 in the high-moisture biomass supply process S22 is dried. In the drying process S23, the high-moisture biomass is dried mainly using the heat from the pyrolysis gas generated in the first carbonization process S24 and burned in the combustion section 35. At this time, the pyrolysis gas generated in the second carbonization process S13 and burned in the combustion section 25 is also used to dry the high-moisture biomass. As a result, the amount of heat that needs to be generated for the production of high-moisture biochar in the high-moisture biochar production unit 3 can be reduced, and carbon dioxide emissions can be reduced.

[0075] In the first carbonization step S24, the high-moisture biomass dried in the drying step S23 is separated from the low-moisture biomass and carbonized in the high-moisture biomass carbonization section 34. In the first carbonization step S24, the carbonization of the high-moisture biomass is carried out using the pyrolysis gas generated during the carbonization of the high-moisture biomass and burned in the combustion section 35. Subsequently, the process from step S21 to the first carbonization step S24 is repeated until the production of biochar derived from high-moisture biomass is completed.

[0076] In the example shown in Figure 3, the high-moisture biomass supply process S22 was performed after the process in step S21. However, if the process in step S21 is performed after the process in the high-moisture biomass supply process S22, and the second carbonization process S13 is in progress, the process may be moved to the drying process S23.

[0077] Next, the biochar production system 1A according to the second embodiment will be described with reference to Figure 4. Note that components similar to those in the first embodiment may be denoted by the same reference numerals and their descriptions may be omitted.

[0078] The biochar production system 1A comprises a low-moisture biochar production unit 2A, a high-moisture biochar production unit 3A, a heat transfer mechanism 4A, a control device 5, and an insulating structure 6.

[0079] The high-moisture biochar production unit 3A comprises a high-moisture biomass supply unit 31, a high-moisture biochar production unit 30A, a high-moisture biochar recovery unit 32, a waste heat recovery boiler 36, an exhaust duct (not shown), and a pyrolysis gas bypass line 38.

[0080] The high-moisture biochar production unit 30A is a device for producing high-moisture biochar, which is a carbonized product of high-moisture biomass. As shown in Figure 4, the high-moisture biochar production unit 30A has a cylindrical main body 300A. High-moisture biomass supplied from the high-moisture biomass supply unit 31 is fed into the other side in the axial direction X (right side in Figure 4) and transported toward one side (left side in Figure 4) while being heated. The drying unit 33, the high-moisture biomass carbonization unit 34, and the combustion unit 35 are in communication with each other and are configured to allow air and gas to flow across their respective areas.

[0081] As shown in Figure 3, the main body 200A of the low-moisture-content biochar production unit 20A, which will be described later, is housed inside the main body 300A.

[0082] The pyrolysis gas bypass line 38 is connected to the main body 300A and is a pipe that extends from the high-moisture biomass carbonization section 34 or drying section 33 side of the main body 300A to above the conveyor belt 312 of the high-moisture biomass supply section 31. This configuration allows the pyrolysis gas, which is burned after being used for carbonization of high-moisture biomass, to be blown onto the high-moisture biomass before it is introduced into the drying section 33, thereby pre-drying the high-moisture biomass.

[0083] The low-moisture biochar production unit 2A comprises a low-moisture biomass supply unit 21, a low-moisture biochar production unit 20A, a low-moisture biochar recovery unit 22, a waste heat recovery boiler 26, and an exhaust duct (not shown).

[0084] The low-moisture biochar production unit 20A is a device for producing secondary biochar, which is a carbonized product of low-moisture biomass. As shown in Figure 4, the low-moisture biochar production unit 20A has a cylindrical main body 200A. Low-moisture biomass supplied from the low-moisture biomass supply unit 21 is fed into one side in the axial direction X and transported toward the other side while being heated.

[0085] The low-moisture biochar production section 20A includes a preheating section 23, a low-moisture biomass carbonization section 24, and a combustion section 25, each located in one of three regions that divide the main body section 200A in the axial direction X. As shown in Figure 4, the preheating section 23, the low-moisture biomass carbonization section 24, and the combustion section 25 are located in this order from one side to the other of the main body section 200A. The preheating section 23, the low-moisture biomass carbonization section 24, and the combustion section 25 are interconnected, and are configured to allow air or gas to flow across their respective regions.

[0086] The main body 200A is housed within the main body 300A with its axial direction substantially aligned with that of the main body 300A. Furthermore, the biochar production system 1A is configured such that the direction in which high-moisture biomass is transported within the main body 300A of the high-moisture biochar production section 30A is opposite to the direction in which low-moisture biomass is transported within the main body 200A of the low-moisture biochar production section 20A.

[0087] As shown in Figure 3, the combustion section 25 and the low-moisture biomass carbonization section 24 on the combustion section 25 side are located within the area where the drying section 33 is provided in the main body section 300A, and the preheating section 23 is located within the area where the combustion section 35 and the high-moisture biomass carbonization section 34 are provided in the main body section 300A.

[0088] The outer periphery wall 201A of the main body 200A has an insulated section 41A where an insulating material 202 is placed, and a non-insulated section 42A where the insulating material 202 is not placed, and which allows heat from inside the main body 200A to be transferred to the main body 300A via the outer periphery wall 201A. Examples of insulating materials 202 include brick-type materials, ceramic-type materials, and high-temperature heat-resistant metal-type materials.

[0089] The heat insulating section 43 is formed on the central side in the axial direction X of the outer peripheral wall 201A. Specifically, the heat insulating section 43 is positioned on the side of the preheating section 23 on the low-moisture biomass carbonization section 24 side of the outer peripheral wall 201A and on the side of the low-moisture biomass carbonization section 24 on the preheating section 23 side. As a result, even in areas of the low-moisture biomass carbonization section 24 that are far from the combustion section 25 where the temperature of the pyrolysis gas tends to drop, heat can be contained within the main body section 200A, so that the temperature of the low-moisture biomass carbonization section 24 can be efficiently maintained above the carbonization temperature.

[0090] Non-insulating sections 44 are formed on both ends of the outer peripheral wall 301A in the axial direction X. Specifically, the non-insulating sections 44 are located on the low-moisture biomass supply section 21 side of the preheating section 23 and on the combustion section 25 side of the combustion section 25 and low-moisture biomass carbonization section 24 in the outer peripheral wall 301A. With this configuration, heat from the pyrolysis gas burned can be transferred to the drying section 33 of the high-moisture biomass production section 30A via the non-insulating sections 44 on the combustion section 25 side, and the transferred heat can be used to dry the high-moisture biomass in the drying section 33. Therefore, the amount of heat required for drying and carbonizing the high-moisture biomass can be supplied from the low-moisture biomass production section 20A, so the temperature of the combustion section 35 can be raised with less energy. Furthermore, heat from the pyrolysis gas burned in the combustion section 35 can be transferred from the combustion section 35 of the high-moisture biochar production section 30A to the preheating section 23 via the non-insulating section 44 on the low-moisture biomass supply section 21 side of the preheating section 23, and the transferred heat can be used to preheat the low-moisture biomass in the preheating section 23. In other words, the heat transfer mechanism 40A according to this embodiment is composed of the positional relationship between the insulating section 43 and the non-insulating section 44, and the main body section 200A and the main body section 300A. Alternatively, the configuration may be such that heat from the pyrolysis gas burned in the high-moisture biomass carbonization section 34 of the high-moisture biochar production section 30A can be transferred via the non-insulating section 44 on the combustion section 25 side.

[0091] The thermal insulation structure 6 is a box-shaped structure in which thermal insulation material is placed at least on its outer wall 60. Inside the thermal insulation structure 6 are the high-moisture biochar production section 30A, the low-moisture biochar production section 20A, the high-moisture biomass supply section 31, at least on the high-moisture biochar production section 30A side of the conveyor belt 312, and the pyrolysis gas bypass line 38. This reduces heat loss discharged to the outside from the biochar production system 1A and reduces the amount of energy required for carbonization of low-moisture and high-moisture biomass.

[0092] According to the embodiments described above, the following effects are achieved.

[0093] Biochar production systems 1 and 1A are biochar production systems 1 and 1A for producing biochar from high-moisture biomass, comprising: a drying section 33 for drying high-moisture biomass; a high-moisture biomass carbonization section 34 for carbonizing the high-moisture biomass dried in the drying section 33; and a low-moisture biomass carbonization section 24 for carbonizing low-moisture biomass, which has a lower moisture content than high-moisture biomass, separately from the high-moisture biomass. The drying section 33 utilizes the pyrolysis gas generated in the low-moisture biomass carbonization section 24 for drying and / or carbonizing the high-moisture biomass. The pyrolysis gas generated in the low-moisture biomass carbonization section 24 is used for drying the high-moisture biomass by the drying section 33 and / or for carbonizing the high-moisture biomass by the high-moisture biomass carbonization section 34.

[0094] This allows the heat from the pyrolysis gas generated during the carbonization of low-moisture biomass to be used for drying high-moisture biomass, thereby reducing the amount of external energy required for the carbonization of high-moisture biomass. As a result, the amount of carbon dioxide emissions associated with the carbonization of high-moisture biomass can be reduced. Furthermore, since low-moisture biochar and high-moisture biochar are carbonized separately, carbonization can be performed at a temperature suitable for the biomass being carbonized, resulting in the production of more uniform and higher-quality biochar. Note that "separately" does not mean that the timing of carbonization of high-moisture and low-moisture biomass is different, but rather that the areas in which carbonization takes place are different for high-moisture and low-moisture biomass. For example, in the embodiment described above, high-moisture biomass is carbonized in the area within the main body sections 300 and 300A, while low-moisture biomass is carbonized in the main body sections 200 and 200A, which are separate areas from the area in which high-moisture biomass is carbonized.

[0095] Furthermore, the biochar production systems 1 and 1A further include a preheating unit 23 that preheats the low-moisture biomass before it is carbonized by the low-moisture biomass carbonization unit 24, and utilize the pyrolysis gas generated in the high-moisture biomass carbonization unit 34 for preheating the low-moisture biomass by the preheating unit 23.

[0096] This allows the pyrolysis gas generated from the carbonization of high-moisture biomass to be used to preheat low-moisture biomass, thus enabling the production of biochar with higher thermal efficiency.

[0097] The biochar production method is a biochar production method for producing biochar from high-moisture biomass, and includes a drying step for drying high-moisture biomass, a first carbonization step for carbonizing the high-moisture biomass dried in the drying step, and a second carbonization step for carbonizing low-moisture biomass, which has a lower moisture content than the high-moisture biomass, separately from the high-moisture biomass, wherein the pyrolysis gas generated in the first carbonization step is used for drying the high-moisture biomass in the drying step and / or for carbonizing the high-moisture biomass in the first carbonization step.

[0098] This allows the heat from the pyrolysis gas generated during the carbonization of low-moisture biomass to be used for drying high-moisture biomass, thereby reducing the amount of external energy required for the carbonization of high-moisture biomass. As a result, the amount of carbon dioxide emissions associated with the carbonization of high-moisture biomass can be reduced. Furthermore, since low-moisture biochar and high-moisture biochar are carbonized separately, carbonization can be performed at a temperature suitable for the biomass being carbonized, resulting in the production of more uniform and higher-quality biochar.

[0099] Furthermore, the biochar production method further includes a preheating step that preheats the low-moisture biomass before the second carbonization step, and the pyrolysis gas generated in the first carbonization step is used to preheat the low-moisture biomass in the preheating step.

[0100] This allows the pyrolysis gas generated from the carbonization of high-moisture biomass to be used to preheat low-moisture biomass, thus enabling the production of biochar with higher thermal efficiency.

[0101] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified as appropriate.

[0102] In the above embodiment, the heat from the pyrolysis gas generated and burned during the carbonization of high-moisture biomass was transferred to the low-moisture biochar production unit 2 and used for preheating the low-moisture biomass. However, the heat from the pyrolysis gas generated and burned during the carbonization of high-moisture biomass may not be transferred to the low-moisture biochar production unit 2 and may not be used for preheating. For example, in the first embodiment, the heat transfer mechanism 4 may have only a first heat transfer mechanism 41 and no second heat transfer mechanism 42. Also, for example, in the second embodiment, the non-insulating portion 44 may be formed only on the combustion portion 25 side of the low-moisture biomass carbonization portion 24 in the outer peripheral wall 201A, and not on the preheating portion 23 side. That is, the insulating portion 43 may be formed in the outer peripheral wall 201A from the preheating portion 23 to the portion of the low-moisture biomass carbonization portion 24 other than the combustion portion 25 side.

[0103] In the above embodiment, the biochar production systems 1 and 1A were equipped with waste heat recovery boilers 26 and 36, respectively. However, it is also possible to have a configuration in which waste heat recovery boilers 26 and 36 are not provided, and steam is not generated using the waste heat discharged from the carbonization equipment such as the low-moisture biochar production section 20 and 20A and the high-moisture biochar production section 30 and 30A, but the waste heat is recovered in its entirety and then directly supplied to the outside. [Explanation of Symbols]

[0104] 1.1A Biochar Production System 23 Preheating section 24. Low-moisture biomass carbonization section (second carbonization section) 33 Drying section 34. High-moisture biomass carbonization section (1st carbonization section)

Claims

1. A biochar production system for producing biochar from a first biomass having a predetermined moisture content, A drying section for drying the first biomass, A first carbonization section carbonizes the first biomass that has been dried in the drying section, The apparatus comprises a second carbonization section that carbonizes a second biomass having a lower moisture content than the first biomass separately from the first biomass, A biochar production system in which the pyrolysis gas generated in the second carbonization section is used for drying the first biomass by the drying section and / or carbonizing the first biomass by the first carbonization section.

2. The system further includes a preheating unit that preheats the second biomass before it is carbonized by the second carbonization unit, The biochar production system according to claim 1, wherein the pyrolysis gas generated in the first carbonization section is used for preheating the second biomass by the preheating section.

3. A method for producing biochar from a first biomass having a predetermined moisture content, A drying step for drying the first biomass, A first carbonization step in which the first biomass dried in the drying step is carbonized, The process includes a second carbonization step in which a second biomass having a lower moisture content than the first biomass is carbonized separately from the first biomass, A method for producing biochar, wherein the pyrolysis gas generated in the second carbonization step is used for drying the first biomass in the drying step and / or for carbonizing the first biomass in the first carbonization step.

4. The process further includes a preheating step of preheating the second biomass before the second carbonization step, The biochar production method according to claim 3, wherein the pyrolysis gas generated in the first carbonization step is used to preheat the second biomass in the preheating step.

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