Biochar production apparatus and biochar production method

Abstract

This technology provides a new way to enable continuous operation of the semi-carbonization process. [Solution] The biochar production apparatus 10 comprises a heat transfer medium heater 14 for heating the heat transfer medium Hm, a heat storage unit for keeping the heated heat transfer medium Hm warm and storing it, and a torrefaction unit for semi-carbonizing the biofuel Bf using the heat from the heat transfer medium supplied from the heat storage unit.

Description

[Technical Field]

[0001] This invention relates to a technology for producing biochar by partially carbonizing biofuels. [Background technology]

[0002] In recent years, with growing attention to climate change, there has been a demand for reducing carbon dioxide emissions. In this context, biofuels, which can achieve virtually zero carbon dioxide emissions, are attracting attention. However, if carbon dioxide is emitted during the manufacturing process of biofuels, they cannot be considered virtually zero. Furthermore, using biofuels as the energy source for biofuel production leads to a decrease in the amount of biofuel that can be produced, resulting in increased costs. Given these problems, producing biofuels using renewable energy sources is being considered.

[0003] Conventionally, torrefaction (partial carbonization) technology is known for decomposing organic matter in woody biomass by heating it to 200-300°C to produce a substance with a high carbon content. There are various methods for heating organic matter, but for example, a technology has been devised in which sunlight is concentrated on the surface of a pipe-shaped reactor containing a substrate made of biomass or other materials, thereby roasting and thermally decomposing the substrate (see Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5329556 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, heating biofuels using sunlight is not possible during bad weather or at night. Therefore, other heating methods are necessary, at least at night. By using heating methods that utilize external fuels or external power sources in combination, the semi-carbonization process of biofuels can be carried out continuously without interruption. On the other hand, using external fuels or external power sources at night leads to increased costs for the semi-carbonization process.

[0006] This invention has been made in view of these circumstances, and one of its exemplary objectives is to provide a new technology that enables continuous operation of a semi-carbonization process. [Means for solving the problem]

[0007] To solve the above problems, a biochar production apparatus according to one aspect of the present invention comprises a heating unit for heating a heat transfer medium, a heat storage unit for maintaining the temperature and storing the heated heat transfer medium, and a torrefaction unit for semi-carbonizing biofuel using the heat from the heat transfer medium supplied from the heat storage unit.

[0008] According to this embodiment, even under conditions where the heating unit that heats the heat transfer medium does not function adequately, the biofuel can be semi-carbonized using the heat of the heat transfer medium stored in the heat storage unit. Therefore, continuous operation of the semi-carbonization process can be achieved.

[0009] The heating section may be configured so that the heat transfer medium is heated by energy obtained from sunlight. This allows the heat required to partially carbonize the biofuel to be obtained using sunlight, a natural energy source, instead of fuel.

[0010] The system may further include a combustion section for burning the exhaust gas discharged from the torrefaction section. The heat storage section may be configured such that the stored heat transfer medium is heated using the waste heat from the combustion section. This allows the exhaust gas from the torrefaction section to be used to heat the heat transfer medium stored in the heat storage section, thus enabling the heat transfer medium to be heated without requiring additional electricity or fuel, and improving the overall heat utilization efficiency of the system.

[0011] The biochar production apparatus may further include a power generation unit that generates power using the exhaust gas discharged from the fractionation unit. The power generation unit may supply the generated power as the power used by the biochar production apparatus. Thereby, at least a part of the power of the biochar production apparatus can be provided without separately procuring power and fuel for the power generation unit from the outside.

[0012] The fractionation unit may further include a fuel supply unit that supplies biofuel. The power generation unit may supply the power used for the power of the fuel supply unit. Thereby, the power used for the power of the fuel supply unit can be supplied without separately procuring power and fuel for the power generation unit from the outside.

[0013] The fractionation unit may further include a heat medium supply unit that supplies a heat medium. The power generation unit may supply the power used for the power of the heat medium supply unit. Thereby, the power used for the power of the heat medium supply unit can be supplied without separately procuring power and fuel for the power generation unit from the outside.

[0014] The biochar production apparatus may further include an external fuel storage unit that stores external fuel. The power generation unit may generate power using the external fuel supplied from the external fuel storage unit at the start of the biochar production apparatus. The external fuel storage unit may stop supplying the external fuel to the power generation unit after power generation using the exhaust gas becomes possible in the power generation unit. In a situation where no exhaust gas is generated in the fractionation unit as at the start of the biochar production apparatus, power generation using the exhaust gas cannot be performed in the power generation unit. Therefore, until power generation using the exhaust gas becomes possible, the external fuel stored in the external fuel storage unit can be used to generate the power required for the apparatus. Also, after power generation using the exhaust gas becomes possible, consumption of the external fuel can be suppressed.

[0015] The fractionation unit may perform semi-carbonization of the biofuel when the heat medium stored in the heat storage unit exceeds a predetermined temperature. Thereby, semi-carbonized biofuel can be stably produced.

[0016] Another aspect of the present invention is a method for producing biochar. This method semi-carbonizes biofuel using heat supplied from a heat storage unit that maintains and stores the heat of a heat transfer medium heated by solar energy.

[0017] According to this embodiment, even under conditions where the heating unit that heats the heat transfer medium does not function adequately, the biofuel can be semi-carbonized using the heat of the heat transfer medium stored in the heat storage unit. Therefore, continuous operation of the semi-carbonization process can be achieved. [Effects of the Invention]

[0018] According to the present invention, a new technology can be realized that enables continuous operation of the semi-carbonization process. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram showing an example of the general configuration of a biochar production apparatus according to the first embodiment. [Figure 2] This is a schematic diagram illustrating an example of a specific configuration of the heating section according to the first embodiment. [Figure 3] This is a schematic diagram illustrating an example of a specific configuration of a processing unit according to the first embodiment. [Figure 4] This figure shows an example of the external shape of a torrefaction furnace. [Figure 5] This is a schematic diagram showing an example of the interior of a torrefaction reactor. [Figure 6] This figure shows the first half of a flowchart illustrating an example of a biochar production method according to the first embodiment. [Figure 7] This figure shows the latter half of a flowchart illustrating an example of a biochar production method according to the first embodiment. [Figure 8] Figure 1 is a schematic diagram showing the general configuration of an example of a biofuel production plant equipped with a biochar production device. [Figure 9] This is a schematic diagram showing the general configuration of an example of a biochar production apparatus according to the second embodiment. [Modes for carrying out the invention]

[0020] The embodiments will be described below with reference to the drawings. In the following embodiments and their modified examples, substantially identical components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0021] (First Embodiment) Figure 1 is a schematic diagram showing an example of the schematic configuration of a biochar production apparatus according to the first embodiment. The first embodiment is an example of a specific embodiment corresponding to each claim. The correspondence between the constituent elements described in the claims and the configuration described in the first embodiment is described below. The heat storage unit described in the claim corresponds to the high-temperature reservoir 16, and the torrefaction unit described in the claim corresponds to the torrefaction furnace 18. The combustion unit and the power generation unit described in the claim correspond to the gas generator with the same configuration. The fuel supply unit described in the claim corresponds to the processing unit 20. The heat transfer medium supply unit described in the claim corresponds to the pump 24. The external fuel storage unit described in the claim corresponds to the gas storage unit 26. The heat transfer medium and biofuel in the claims correspond to the heat transfer medium Hm and biofuel Bf, respectively.

[0022] Sorghum is cultivated in sorghum field F adjacent to plant 100 (see Figure 8), which will be described later. The mature sorghum is harvested at the required time, and the leaves and stems, after being harvested for their edible seeds, are washed, cut, dried, and processed into pellets before being supplied to a designated reactor. Other resource crops besides sorghum include grasses such as Erianthus, Giant Miscanthus, and Napier Grass. In addition, the leaves and stems of bananas, corn, and sugarcane may also be used as cellulosic raw materials. Rice and wheat husks may also be used. Biochar is a plant-derived charcoal such as wood charcoal or bamboo charcoal, and can be described as a solid material produced by heating biomass at a temperature of about 200-400°C under an oxygen concentration controlled to a level that does not cause combustion.

[0023] The biochar production apparatus 10 according to this embodiment is a self-sustaining apparatus that is independent of the external power grid and can achieve continuous operation of the semi-carbonization process while minimizing fuel consumption for semi-carbonization. The biochar production apparatus 10 comprises a heat transfer medium heater 14 as a heating unit for heating the heat transfer medium Hm, a high-temperature reservoir 16 as a heat storage unit for maintaining and storing the heated high-temperature heat transfer medium Hm, and a torrefaction furnace 18 as a torrefaction unit for semi-carbonizing the biofuel Bf using the heat from the heat transfer medium Hm supplied from the high-temperature reservoir 16. Figure 2 is a schematic diagram illustrating an example of a specific configuration of the heating unit according to the first embodiment. In this embodiment, sunlight reflected by a number of heliostats 22a (concentrating mirrors 22) whose reflective surfaces move in accordance with the movement of the sun irradiates the concentrating unit 14b at the top of the heat collection tower 14a, thereby heating the heat transfer medium Hm.

[0024] Torrefaction is a thermochemical treatment that takes place at 200-320°C in an oxygen-free atmosphere, resulting in the browning of the substance before the reaction due to the Maillard reaction. The main reactions involve the partial decomposition of cellulose, hemicellulose, and lignin, and the release of water and volatile substances. This process results in a mass loss of about 20% (on a dry basis) and a heat loss of about 10%, but with little change in volume.

[0025] Figure 3 is a schematic diagram illustrating an example of a specific configuration of the processing unit according to the first embodiment. Sorghum S harvested from the sorghum field F is cut into predetermined shapes by a cutter 20a in the processing unit 20, ultrasonically cleaned in a washing machine 20b, dried in a drying oven 20c, formed into pelletized biofuel Bf in a forming device 20d, and the formed biofuel Bf is supplied to the torrefaction furnace 18. Here, the heat required to heat the drying oven 20c is supplied via a heat transfer medium Hm. As described above, the heat transfer medium heater 14 is configured so that the heat transfer medium Hm is heated by energy (solar heat) obtained from sunlight concentrated by the concentrating mirror 22. In this way, the biochar production apparatus 10 according to this embodiment obtains the heat required to semi-carbonize the biofuel using natural energy, namely sunlight, instead of fuel.

[0026] The heated heat transfer medium Hm is used to transport the heat required in various subsequent processes. For example, the heat transfer medium Hm circulates through the heat transfer medium circulation path C1 when the pump 24 is driven, supplying the heat necessary for roasting (partial carbonization) of the biofuel Bf in the torrefaction furnace 18. Furthermore, the heat transfer medium Hm also supplies the heat necessary for drying the biomass in the drying furnace of the processing unit 20.

[0027] Incidentally, heating the biofuel Bf using sunlight is not possible during bad weather or at night. Therefore, other heating means are necessary, at least at night. In this embodiment, the biochar production apparatus 10 solves this problem by providing a high-temperature reservoir 16 that temporarily stores heat. In other words, even under conditions where the heat transfer medium heater 14 that heats the heat transfer medium Hm is not functioning properly, the biofuel Bf can be semi-carbonized using the heat from the heat transfer medium Hm stored in the high-temperature reservoir 16. Therefore, continuous operation of the semi-carbonization process can be achieved.

[0028] Examples of heat transfer fluids (Hm) include DOWTHERM (registered trademark, manufactured by Dow Chemical) and MARLOTHERM (registered trademark, manufactured by Sasol). The material used for the heat transfer fluid (Hm) should be appropriately selected according to the optimal operating temperature of the torrefaction furnace 18, but for example, it should be usable in the range of 200 to 400°C. More preferably, a material usable in the range of 250 to 350°C should be used as the heat transfer fluid (Hm).

[0029] The biochar production apparatus 10 further includes a gas storage unit 26 for temporarily storing exhaust gas Eg discharged from the torrefaction furnace 18, and a gas generator 28 for generating electricity by burning the exhaust gas Eg. The exhaust gas Eg from the gas generator 28 supplies heat to the heat transfer medium Hm via a heat exchanger 30, accompanied by waste heat Eh. In other words, the high-temperature reservoir 16 is configured so that the stored heat transfer medium Hm is heated using the waste heat Eh from the gas generator 28. In this way, since the exhaust gas Eg from the torrefaction furnace 18 can be used to heat the heat transfer medium Hm stored in the high-temperature reservoir 16, the heat transfer medium Hm can be heated without requiring new electricity or fuel, improving the overall heat utilization efficiency of the biochar production apparatus 10. The exhaust gas Eg contains, for example, hydrogen, methane, carbon monoxide, carbon dioxide, etc., and is supplied back to the torrefaction furnace 18 via the heat exchanger 30. This reduces the oxygen concentration in the torrefaction furnace 18.

[0030] Furthermore, the gas generator 28 also functions as a power generation unit that burns exhaust gas (e.g., hydrogen or methane) discharged from the torrefaction furnace 18 to generate electricity. The gas generator 28 supplies the generated electricity to various parts of the biochar production apparatus 10 (torrefaction furnace 18, processing unit 20, etc.). This ensures that at least a portion of the power supply for the biochar production apparatus 10 can be covered without the need to separately procure electricity or fuel for the gas generator 28 from an external source. The gas generator 28 may also be a fuel cell, in which case heat is emitted from the chemical reaction between hydrogen and oxygen.

[0031] The processing unit 20 also functions as a fuel supply unit that supplies biofuel Bf to the torrefaction furnace 18. The gas generator 28 supplies electricity Ep used to power the various parts of the processing unit 20 and the torrefaction furnace 18. The pump 24 functions as a heat transfer medium supply unit that supplies heat transfer medium Hm to the torrefaction furnace 18. This allows the processing unit 20 and the pump 24 to be powered by electricity Ep used to power them without the need to separately procure electricity or fuel for the gas generator 28 from an external source. In addition, a backup power source 32 such as a fuel cell or storage battery may be provided as an emergency power source. The backup power source 32 may also be connected to a grid or solar cells.

[0032] (Torrefaction furnace) Next, the details of the torrefaction furnace described above are illustrated below. Figure 4 shows an example of the external shape of the torrefaction furnace 18. Figure 5 is a schematic diagram showing an example of the interior of the torrefaction furnace 18. The torrefaction furnace 18 has a cylindrical casing 18b with a space 18a inside. Multiple pipes are connected to the casing 18b through which various substances flow in and out.

[0033] The biofuel piping 18c is for supplying biofuel Bf, supplied from the processing unit 20, to space 18a. The biochar piping 18d is for supplying biochar Bc, which is semi-carbonized from the biofuel Bf heated / stirred in space 18a, to the coal-fired power plant 12. The deoxygenated gas piping 18e is for supplying decarbonized gases such as hydrogen, methane, carbon monoxide, and carbon dioxide from the heat exchanger 30 to space 18a. The exhaust gas piping 18f is for supplying exhaust gas Eg to the gas storage unit 26. The heat transfer medium inlet piping 18g is for supplying heat transfer medium Hm from the high-temperature reservoir 16 to heat the atmosphere of space 18a from the outside. The heat transfer medium outlet piping 18h is for supplying the heat transfer medium Hm, which has heated space 18a from the outside, to the processing unit 20 or returning it to the heat transfer medium heater 14. Space 18a is equipped with a stirring device 38 driven by electricity Ep generated by the gas generator 28. The stirring device 38 promotes partial carbonization by stirring the biofuel Bf in the space 18a.

[0034] Next, the operation of the biochar production apparatus 10 during startup (cold start) will be described. When the biochar production apparatus 10 is started, the gas generator 28 starts generating electricity when it is supplied with exhaust gas Eg stored in the gas storage unit 26, which also functions as an external fuel storage unit. Alternatively, the gas generator 28 may use a fuel other than exhaust gas Eg when the biochar production apparatus 10 is started. The biochar production apparatus 10 operates the torrefaction furnace 18 and pump 24 with the power generated by the gas generator 28, and after sufficient exhaust gas Eg is supplied from the torrefaction furnace 18 to the gas generator 28 and power generation becomes possible, the supply of fuel from the gas storage unit 26 is stopped.

[0035] In situations where no exhaust gas E is generated in the torrefaction furnace 18, such as when the biochar production apparatus 10 is started, the gas generator 28 cannot generate electricity using the exhaust gas E. Therefore, until power generation using the exhaust gas E becomes possible, the gas storage unit 26 can generate the electricity necessary for the apparatus using the exhaust gas E previously stored. Furthermore, once power generation using the exhaust gas E becomes possible, the consumption of fuel stored in the gas storage unit 26 can be reduced.

[0036] In addition, when the heat medium Hm stored in the high-temperature reservoir 16 exceeds a predetermined temperature (for example, 300°C), the torrefaction furnace 18 according to the present embodiment performs semi-carbonization of the biofuel Bf. As a result, semi-carbonized biofuel can be stably produced.

[0037] (Biochar production method) Next, the biochar production method according to the present embodiment will be described. FIG. 6 is a diagram showing the first half of a flowchart for explaining an example of the biochar production method according to the first embodiment. FIG. 7 is a diagram showing the second half of a flowchart for explaining an example of the biochar production method according to the present embodiment. Note that the arithmetic processing and discrimination processing in each step of the following flowchart are executed by a control device composed of an electronic circuit such as a CPU or an IC.

[0038] In addition, the meanings of variables and constants in each formula in the arithmetic processing and judgment processing are as follows. M: Time mass flow rate of the heat medium A: Loss inside the roasting furnace + heat exchange loss, etc. Q T : Heat quantity required per unit mass of roasted sorghum C P : Heat capacity of the heat medium S: Unit time input biomass mass ΔT2: Supply heat temperature - heat medium temperature T m : Heat medium temperature T r : Reaction temperature Q Es : Stored heat quantity Q Ec : Recovered heat quantity Q tc : Torrefaction heat quantity W ts : Heat supply quantity W n : Required electric power

[0039] The flowcharts shown in Figures 6 and 7 indicate that the biochar production process begins when a signal to produce biochar is input to the biochar production apparatus 10. The control device receives weather forecast information (solar radiation (KW / m²)). 2 Based on the solar heat generated (temperature T of the heat transfer medium), the amount of heat stored in the high-temperature reservoir 16 up to time t is estimated (temperature T of the heat transfer medium). m ) is predicted (Step S01). Next, it is determined whether or not torefacturing at time t is possible (Step S02). The determination in Step S02 is based on equation (2). Equation (2) is obtained by expanding the relationship in equation (1).

[0040] Q T ×A×S×t>((T r -T m )×C P ×M×t) Equation (1) T m >T r -(Q T ×A×S×t) / C P ×M×t Formula (2)

[0041] For example, the temperature T of the heat transfer medium Hm m If equation (2) is satisfied (Y in step S02), the process of estimating the amount of gas stored for power is performed (step S09). Meanwhile, the temperature T of the heat transfer medium Hm m If equation (2) is not satisfied (N in step S02), additional heat is needed, and the amount of fuel stored for the heat source is estimated (step S03). The amount of fuel stored (amount of gas stored in the gas storage unit 26) is estimated by the amount of stored heat Q. Es And, the amount of heat recovered Q Ec The amount of heat required for torrefaction is determined based on equation (3). The amount of heat required for torrefaction is determined based on equation (4).

[0042] Q Es +Q Ec >Q tc Formula (3) W ts ×t = ΔT² × C P ×M×t=Q T ×A×S×t=Q tc Formula (4)

[0043] In other words, Q is an example that satisfies equation (3). Es +Q Ec >Q tc The decision is made based on whether or not the condition (step S04) is met. If equation (3) is met (Y in step S04), it is assumed that fuel can be supplied and the external heat source is started (step S06). On the other hand, if equation (3) is not met (N in step S04) and external fuel supply is not possible (N in step S18), the processing of this flow is stopped. On the other hand, if external fuel supply is possible (Y in step S18), fuel is supplied from the outside (step S05) and the external heat source is started (step S06).

[0044] Subsequently, the valve of the heat transfer medium storage unit (such as the high-temperature reservoir 16) is closed, and the supply of the heat transfer medium is shut off (step S07). Heating of the heat transfer medium is also shut off (step S08). In step S09, the amount of electricity gas stored is estimated, and it is determined whether electricity gas supply is possible (step S10). The determination of whether electricity gas supply is possible or not is based on the following equation (5).

[0045] Q Es +Q Ec -Q tc >W n ×t Equation (5)

[0046] In other words, if equation (5) is satisfied (Y in step S10), the generator is started, assuming that a gas supply for electricity is possible (step S12). On the other hand, if equation (5) is not satisfied (N in step S10), it is determined whether an external power supply is possible, and if an external power supply is not possible (N in step S19), the processing of this flow is stopped. On the other hand, if an external power supply is possible (Y in step S19), power is supplied externally (step S11). Once the generator is started and power is supplied to the torrefaction device (torrefaction furnace 18), the torrefaction device (torrefaction furnace 18) is started (step S13).

[0047] Subsequently, pelletized biofuel Bf is fed into the torrefaction furnace 18 at a predetermined pace (S [kg / h]) (step S14), and torrefaction (partial carbonization) is performed (step S15). Also, the gas generated during torrefaction is recovered (step S16). Then, it is determined whether or not to terminate the production of the desired biochar (step S17). If the production of the desired biochar is terminated (N in step S17), the process returns to step S01 and continues. On the other hand, if the production of the desired biochar is terminated (Y in step S17), the biochar production process is terminated.

[0048] In this embodiment, the torrefaction temperature in the torrefaction furnace 18 is in the range of 225°C to 275°C, with approximately 250°C being preferred. The proportion of biochar produced is approximately 0.6 to 0.95 kg from 1 kg of biomass fuel, preferably in the range of 0.7 to 0.9 kg. The preferred torrefaction temperature varies depending on the biomass fuel material and environment, so it is desirable to adjust it appropriately while monitoring the biochar yield.

[0049] Figure 8 is an example of the application of the first embodiment and is a schematic diagram showing the general configuration of a biofuel production plant equipped with the biochar production apparatus shown in Figure 1. The plant 100 shown in Figure 8 is equipped with a biochar production apparatus 10 that semi-carbonizes pellets made from sorghum, a resource crop that is a type of biomass Bm, to produce high-energy-density biofuel (biochar). The biochar Bc produced by the biochar production apparatus 10 is supplied to a coal-fired power plant 12.

[0050] Plant 100 generates electricity at a coal-fired power plant 12 using bio-coal Bc produced by the bio-coal production device 10. The generated electricity may be used to power the various parts of Plant 100, or it may be connected to the grid and transmitted to the outside. Plant 100 is equipped with a gasifier / converter 34. Sorghum harvested from the sorghum field F is processed into biofuel Bf in the processing unit 36 ​​and supplied to the gasifier / converter 34. The gasifier / converter 34 is supplied with biofuel Bf and high-temperature exhaust gas Eg (waste heat Eh) produced by the coal-fired power plant 12, and methanol etc. is synthesized in a reactor containing a catalyst. At that time, the pitch P produced in the gasifier / converter 34 is supplied to the coal-fired power plant 12 as fuel along with bio-coal Bc.

[0051] As described above, sunlight is concentrated to heat and store heat in a heat transfer medium. Then, torrefaction is performed using the stored heat transfer medium, which allows for stable production when manufacturing biochar using unstable natural energy. In addition, carbon dioxide emissions during biochar production can be significantly reduced. Furthermore, by constructing a coal-fired power plant and a gasifier / converter adjacent to the farm, in addition to the biochar production apparatus of the first embodiment, a plant capable of operating independently can be constructed even in remote areas where electricity supply is difficult.

[0052] (Second embodiment) Figure 9 is a schematic diagram showing the general configuration of an example of a biochar production apparatus according to the second embodiment. In the following description, the same reference numerals are used for components that are the same as those in the biochar production apparatus 10 shown in Figure 1, and their explanations will be omitted as appropriate. The main feature of the biochar production apparatus 50 shown in Figure 9 is that it uses exhaust gas Eg, which has undergone heat exchange between the heat medium Hm and the heat exchanger 30, rather than a heat medium Hm heated using sunlight, to supply heat for use in the torrefaction furnace 18 and processing unit 20.

[0053] Unlike the first embodiment, the torrefaction furnace 18 does not have a heating mechanism using a heat transfer medium. Instead, it roasts the biofuel by directly blowing high-temperature gas, heated in the heat exchanger 30, onto the biofuel. For this reason, the heat exchanger 30 absorbs and heats a large amount of air (for example, to over 300°C). The heated air is then mixed with exhaust gas Eg from the gas generator 28 and supplied to the torrefaction furnace as needed.

[0054] As a result, similar to the biochar production apparatus 10 shown in Figure 1, even under conditions where the heat transfer medium heater 14 that heats the heat transfer medium Hm is not functioning properly, the biofuel Bf can be semi-carbonized by indirectly utilizing the heat of the heat transfer medium Hm stored in the high-temperature reservoir 16. Therefore, continuous operation of the semi-carbonization process can be achieved. In addition, the exhaust gas Eg of the gas generator 28 is at a relatively high temperature of about 600°C (500-700°C), so the heat of the exhaust gas Eg can be used to heat the heat transfer medium Hm via the heat exchanger 30. Therefore, the amount of heat stored in the high-temperature reservoir 16 can be increased without using solar energy.

[0055] As described above, according to the second embodiment, the gas is heated by a heat exchanger using the heat stored in the high-temperature reservoir 16. Since the semi-carbonization is then performed with the heated gas, there is no need to configure a mechanism for heating with a heat transfer medium in the torrefaction furnace. Therefore, existing torrefaction furnaces can be used as is.

[0056] It should be noted that the present invention is not limited to the embodiments and modifications described above, and the components can be modified and implemented without departing from the spirit of the invention. Various inventions may be formed by appropriately combining the multiple components disclosed in the embodiments and modifications described above. In addition, some components may be deleted from all the components shown in the embodiments and modifications described above. [Explanation of Symbols]

[0057] 10 Biochar production equipment, 12 Coal-fired power generation, 14 Heat transfer fluid heater, 16 High-temperature reservoir, 18 Torrefaction furnace, 20 Processing unit, 22 Focusing mirror, 24 Pump, 26 Gas storage unit, 28 Gas generator, 30 Heat exchanger, 32 Backup power supply, 34 Gasifier / Converter, 36 Processing unit, 50 Biochar production equipment, 100 Plant.

Claims

1. A heating unit that heats the heat transfer medium, A heat storage unit that maintains and stores the temperature of the heated heat transfer medium, A torrefaction unit that semi-carbonizes biofuel using the heat of a heat transfer medium supplied from the heat storage unit, A biochar production device equipped with the following features.

2. The biochar production apparatus according to claim 1, characterized in that the heating section is configured such that the heat transfer medium is heated by energy obtained from sunlight.

3. The system further comprises a combustion section for burning the exhaust gas discharged from the torrefaction section, The biochar production apparatus according to claim 1 or 2, characterized in that the heat storage section is configured such that the stored heat transfer medium is heated using the waste heat from the combustion section.

4. The system further includes a power generation unit that generates electricity using exhaust gas discharged from the torrefaction unit, The biochar production apparatus according to claim 1 or 2, characterized in that the power generation unit supplies the generated electricity as electricity used by the biochar production apparatus.

5. The torrefaction section is further provided with a fuel supply unit that supplies biofuel, The biochar production apparatus according to claim 4, characterized in that the power generation unit supplies electricity used to power the fuel supply unit.

6. The torrefaction section is further provided with a heat transfer medium supply unit that supplies a heat transfer medium, The biochar production apparatus according to claim 4, characterized in that the power generation unit supplies electricity used to power the heat transfer medium supply unit.

7. It further includes an external fuel storage unit for storing external fuel, The power generation unit generates electricity using external fuel supplied from the external fuel storage unit when the biochar production apparatus is started. The biochar production apparatus according to claim 4, characterized in that the external fuel storage unit stops supplying the external fuel to the power generation unit after the power generation unit becomes capable of generating electricity using the exhaust gas.

8. The biochar production apparatus according to claim 1 or 2, characterized in that the torrefaction unit performs partial carbonization of the biofuel when the heat transfer medium stored in the heat storage unit exceeds a predetermined temperature.

9. A method for producing biochar that semi-carbonizes biofuel using heat supplied from a heat storage unit that maintains and stores the heat transfer medium heated by solar energy.

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