Biomass utilization system and biomass utilization method

Abstract

A biomass utilization system 1 comprises a combustion furnace 10, a boiler 40, and a connection flow path 36. Second biomass is supplied, via a second biomass supply port 18 provided downstream of a first biomass supply port 17, to a carbonization region in which there is low-concentration oxygen gas which has a lower oxygen concentration air due to the combustion of the first biomass and which is heated by combustion of a first biomass. A product passes through the inside of the connection flow path 36. A carbonized material is continuously supplied, via airflow, from the combustion furnace 10 and toward the boiler 40.

Description

Biomass utilization system and biomass utilization method

[0001] The present disclosure relates to a biomass utilization system and a biomass utilization method.

[0002] The use of biomass instead of fossil fuels has been studied to reduce the amount of fossil fuel used. A conventional biomass utilization method involves pyrolyzing biomass and using pyrolysis gas, tar, and char in a pulverized coal-fired boiler.

[0003] Patent Document 1 discloses a biomass utilization device including a shaft-type pyrolysis furnace that discharges pyrolysis gas and pyrolysis tar from the furnace top and char from the furnace bottom, and a pulverized coal-fired boiler that burns pulverized coal to generate steam. The pyrolysis gas and pyrolysis tar are sent from the shaft-type pyrolysis furnace to the pulverized coal-fired boiler. The char produced in the shaft-type pyrolysis furnace is transported to a char treatment device and a coal crusher.

[0004] International Publication No. 2010 / 047042

[0005] In the biomass utilization device of Patent Document 1, the char treatment device has a coarse crushing device and a fine crushing device, and the char is crushed in the char treatment device and coal crushing device. Specifically, the char is crushed using a biaxial crusher, a hammer mill, or the like, and then crushed in the coal crushing device. The crushed char is then supplied to a pulverized coal-fired boiler. However, because crushers such as biaxial crushers and hammer mills crush the char by shearing, the crushing parts wear out quickly. Therefore, in the prior art, frequent maintenance of the crushing parts is required, which may result in long shutdown periods and high maintenance costs.

[0006] Therefore, the present disclosure aims to provide a biomass utilization system and a biomass utilization method that can reduce maintenance burden by reducing or not using crushing equipment or reducing wear on crushing parts, and that can continuously produce boiler fuel.

[0007] A biomass utilization system according to the present disclosure includes a combustion furnace having a first biomass supply port for supplying first biomass and including a combustion chamber for combusting the first biomass with air. The biomass utilization system also includes a boiler that burns a product containing charred material produced from a second biomass as fuel, and a connecting flow path connecting the combustion furnace and the boiler. The second biomass is supplied via a second biomass supply port located downstream of the first biomass supply port to a carbonization zone that is heated by combustion of the first biomass and contains low-oxygen gas whose oxygen concentration is lower than that of air due to the combustion of the first biomass. The product passes through the connecting flow path, and the charred material is continuously supplied from the combustion furnace to the boiler with the airflow.

[0008] The connecting flow path may include a crushing section that crushes the carbide by the flow of the air current.

[0009] The pulverizing section may include a confluence section where carbides flowing on the air current from the combustion furnace meet and collide with each other to be pulverized.

[0010] The combustion furnace may have a hearth.

[0011] The combustion furnace may be a fluidized bed furnace, a grate furnace, or a rotary furnace.

[0012] The combustion furnace is a fluidized bed combustion furnace including a fluidized bed, and the fluidized bed may contain at least one type of coal ash selected from the group consisting of clinker, cinder ash, and fly ash.

[0013] The products may include gas produced from the second biomass.

[0014] A biomass utilization method according to the present disclosure includes a step of combusting first biomass supplied to a combustion chamber of a combustion furnace with air. The biomass utilization method includes a step of supplying second biomass to a carbonization zone downstream of the first biomass, which is heated by the combustion of the first biomass and in which low-oxygen gas having a lower oxygen concentration than air due to the combustion of the first biomass is present. The biomass utilization method also includes a step of burning a product containing charred material produced from the second biomass as fuel in a boiler. The product passes through a connecting flow path connecting the combustion furnace and the boiler, and the charred material is continuously supplied from the combustion furnace to the boiler on an air current.

[0015] According to the present disclosure, it is possible to provide a biomass utilization system and a biomass utilization method that can continuously produce boiler fuel by reducing or not using crushing equipment or reducing wear on crushing parts, thereby reducing maintenance burden.

[0016] Fig. 1 is a schematic diagram showing a biomass utilization system according to one embodiment. Fig. 2 is a schematic diagram showing a combustion furnace according to one embodiment. Fig. 3 is a schematic diagram showing a boiler according to one embodiment. Fig. 4 is a schematic diagram showing a biomass utilization system according to one embodiment. Fig. 5 is a schematic diagram showing a biomass utilization system according to one embodiment.

[0017] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that the dimensional proportions of the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0018] First, a biomass utilization system 1 according to the first embodiment will be described with reference to Figures 1 to 3. As shown in Figure 1, the biomass utilization system 1 according to this embodiment includes a combustion furnace 10, a connecting flow path 36, and a boiler 40. The combustion furnace 10 is configured to combust the first biomass. The boiler 40 burns products containing charcoal generated from the second biomass as fuel. The connecting flow path 36 connects the combustion furnace 10 and the boiler 40, and the products pass through the connecting flow path 36, while the charcoal is carried by the air current and continuously supplied from the combustion furnace 10 to the boiler 40.

[0019] As shown in Figure 2, the combustion furnace 10 in this embodiment is a vertical fluidized bed combustion furnace. Although a vertical combustion furnace has the advantage of not requiring a large installation area, the combustion furnace 10 is not limited to a vertical combustion furnace and may be a horizontal combustion furnace. Furthermore, the combustion furnace 10 is not limited to a fluidized bed combustion furnace and may be a grate combustion furnace or a rotary combustion furnace such as a kiln combustion furnace.

[0020] The combustion furnace 10 includes a wind box 11 and a combustion chamber 12 located vertically above the wind box 11. The wind box 11 is a chamber for supplying combustion air. The combustion chamber 12 is a chamber for combusting the first biomass with air. The combustion furnace 10 has a hearth 15a. Because the combustion furnace 10 has the hearth 15a, the first biomass can be stably combusted in the combustion chamber 12. In this embodiment, the hearth 15a is a fluidized bed. Air is supplied to the fluidized bed by an air distribution plate 13. The wind box 11 and the combustion chamber 12 are separated by the air distribution plate 13. The air distribution plate 13 has a plurality of first air supply holes 14.

[0021] The plurality of first air supply holes 14 are first air supply ports that supply air to the combustion chamber 12. The air supplied through the first air supply holes 14 is primary air. The primary air is supplied to the bed material 15 and is mainly used for combustion. Air supplied from the air supply unit 20 is supplied to the combustion chamber 12 through the air box 11 and the plurality of first air supply holes 14. In this embodiment, the air diffusion system of the combustion furnace 10 is a dispersion plate type, but it may also be an air diffusion pipe type or a combination of these.

[0022] An air supply unit 20 is connected to the wind box 11. The air supply unit 20 includes an air flow path 21, an air intake 22, and a blower 23. The air flow path 21 is provided with the air intake 22 and the blower 23. The air flow path 21 is also provided with a flow rate adjustment damper 24 between the air intake 22 and the blower 23. The air flow path 21 is also provided with a flow rate adjustment damper 25 between the blower 23 and the wind box 11. By driving the blower 23 with the flow rate adjustment dampers 24 and 25 open, air can be continuously supplied from the air intake 22 to the wind box 11.

[0023] Within the combustion chamber 12, a bed material 15 is placed on the air distribution plate 13. The bed material 15 may contain inert particles such as silica sand. When air is supplied from the air box 11 to the combustion chamber 12 through the first air supply holes 14 of the air distribution plate 13, the bed material 15 becomes fluidized and forms a fluidized bed. The air ratio in the fluidized bed may be approximately 0.5 to 1.5. By setting this air ratio, it is possible to suppress ash melting and reduce agglomeration.

[0024] The combustion chamber 12 is provided with a second air supply port 16 , a first biomass supply port 17 , a second biomass supply port 18 a , and an exhaust port 19 .

[0025] The second air supply port 16 is a supply port that supplies air to the combustion chamber 12. The second air supply port 16 is provided on a side wall that constitutes the combustion chamber 12. The second air supply port 16 is provided vertically above the first air supply hole 14 and vertically below the second biomass supply port 18a and the exhaust port 19. The air supplied through the second air supply port 16 is secondary air. By supplying secondary air to the combustion chamber 12, staged combustion is possible, making it possible to appropriately adjust the temperature inside the furnace. In addition, the secondary air can also be used to adjust the oxygen concentration in the carbonization region, which will be described later.

[0026] An air flow path 21 is connected to the second air supply port 16. The air flow path 21 branches between the blower 23 and the flow rate control damper 25. A flow rate control damper 26 and a flow rate control damper 27 are provided in the branched air flow path 21. By driving the blower 23 with the flow rate control dampers 24, 26, and 27 open, air can be continuously supplied from the air intake 22 through the second air supply port 16 to the combustion chamber 12.

[0027] The first biomass supply port 17 is a supply port that supplies the first biomass to the combustion chamber 12. Because the first biomass can be supplied to the combustion chamber 12 via the first biomass supply port 17, the first biomass can be continuously supplied to the combustion chamber 12. Biomass is positioned as a renewable energy source, and from the perspective of carbon neutrality, it is believed that burning biomass does not lead to an increase in carbon dioxide released into the atmosphere.

[0028] The first biomass supply port 17 is provided on a side wall that constitutes the combustion chamber 12. The first biomass supply port 17 is provided vertically above the first air supply hole 14. A first biomass supply unit 30 that supplies the first biomass to the combustion chamber 12 of the combustion furnace 10 is connected to the first biomass supply port 17. The first biomass supplied to the combustion chamber 12 by the first biomass supply unit 30 is stirred together with the bed material 15 and combusted.

[0029] The second biomass supply port 18a is a supply port that supplies the second biomass into the combustion chamber 12. When the second biomass is supplied into the combustion chamber 12, carbonized material is produced in the combustion chamber 12. Since the second biomass can be supplied to the combustion chamber 12 via the second biomass supply port 18a, the second biomass can be continuously supplied to the combustion chamber 12. The second biomass supply port 18a is provided on a side wall that constitutes the combustion chamber 12. The second biomass supply port 18a is provided downstream of the first biomass supply port 17. Specifically, the second biomass supply port 18a is provided vertically above the first biomass supply port 17. The second biomass supply port 18a is also provided downstream of the first air supply hole 14. A second biomass supply unit 31 that supplies the second biomass to the combustion chamber 12 is connected to the second biomass supply port 18a. The second biomass supplied to the combustion chamber 12 by the second biomass supply unit 31 is carbonized as described below, and a carbonized material is produced from the second biomass.

[0030] The second biomass is heated by the combustion of the first biomass and supplied to a carbonization zone through the second biomass supply port 18a, where the carbonization zone is heated by the combustion of the first biomass and where low-oxygen gas, which has a lower oxygen concentration than air due to the combustion of the first biomass, is present. The carbonization zone is maintained at a temperature and low oxygen concentration suitable for producing char, and the second biomass is supplied in such a controlled atmosphere. The second biomass is heated by the high-temperature gas produced by the combustion of the first biomass. This allows stable pyrolysis of the second biomass, enabling stable production of char from the second biomass.

[0031] The properties of the produced carbonized material vary depending on conditions such as the type and drying state of the second biomass, the amount of second biomass supplied, the temperature of the carbonization zone, and the oxygen concentration in the carbonization zone, etc. Therefore, the conditions of the amount of second biomass supplied, the temperature of the carbonization zone, and the oxygen concentration in the carbonization zone may be determined in advance by a trial run depending on the properties of the carbonized material to be produced.

[0032] The exhaust port 19 is an exhaust port for discharging gas after the first biomass is burned. When char is produced from the second biomass in the combustion chamber 12, the char is also discharged through the exhaust port 19. The char can be discharged from the exhaust port 19 on the combustion gas whose volume has expanded due to combustion. The exhaust port 19 is provided vertically above the first air supply hole 14, the second air supply port 16, the first biomass supply port 17, and the second biomass supply port 18a. In this embodiment, the exhaust port 19 is provided in the ceiling that constitutes the combustion chamber 12, but may also be provided in a side wall of the combustion chamber 12. The exhaust port 19 is connected to a connecting flow path 36.

[0033] The first biomass and the second biomass may be the same type of biomass or different types of biomass. The biomass may include, for example, wood, herbs, livestock waste, household waste such as sewage sludge and septic tank sludge, and organic matter such as food waste. The biomass may include at least one of waste-based biomass and unused biomass. The waste-based biomass may include livestock waste such as chicken manure. The unused biomass may include at least one of inedible parts of agricultural crops, forestry residues, bamboo, and bamboo grass. The inedible parts of agricultural crops may include at least one selected from the group consisting of rice husks, rice straw, wheat straw, corn stalks, empty palm fruit bunches (EFB), old palm trees (OPT), and palm kernel shells (PKS). The biomass may include at least one of herbaceous biomass and woody biomass. The woody biomass may include at least one of thinnings and pruned branches. Among these, from the viewpoint of abundance, it is preferable that the biomass contains at least one selected from the group consisting of rice husks, rice straw, wheat straw, chicken droppings, corn stalks, bamboo, bamboo grass, thinning materials, and pruned branches.

[0034] The first biomass supply unit 30 and the second biomass supply unit 31 may each include a continuous supply type feeder such as a screw feeder or a table feeder. The first biomass supply unit 30 and the second biomass supply unit 31 may also include a weight feeder such as a loss-in-weight type feeder or a volumetric feeder. The amount of the second biomass supplied from the second biomass supply unit 31 may be 0.01 to 100 times, 0.1 to 30 times, or 2 to 10 times the amount of the first biomass supplied from the first biomass supply unit 30.

[0035] The second biomass supplied through the second biomass supply port 18a may be smaller in size than the first biomass supplied through the first biomass supply port 17. The particle diameter of the first biomass supplied through the first biomass supply port 17 is not particularly limited, but may be 1 mm to 2 mm. A particle diameter of 1 mm or more is economically advantageous, while a particle diameter of 2 mm or less is combustible. The particle diameter of the second biomass supplied through the second biomass supply port 18 is not particularly limited, but is preferably 1 mm to 5 mm from the viewpoint of transportability to the boiler 40. A particle diameter of 1 mm or more is economically advantageous, while a particle diameter of 5 mm or less is advantageous in transportability of the generated charcoal, although this depends on the shape of the charcoal. The particle diameter can be obtained by calculating the average length of the longest diameter of each particle.

[0036] The biomass utilization system 1 may include at least one selected from the group consisting of a magnetic separator, a wind separator, and a particle size separator (not shown). These separators can remove foreign matter such as metals and concrete fragments from the first biomass supplied by the first biomass supply unit 30 and the second biomass supplied by the second biomass supply unit 31.

[0037] The combustion furnace 10 may include a thermometer 34 that measures the temperature in the combustion chamber 12, vertically above the second air supply port 16 and vertically below the exhaust port 19. Measuring the temperature of the carbonization zone with the thermometer 34 makes it possible to easily control the carbonization temperature. The temperature of the carbonization zone may be approximately 700°C to 1200°C. By setting the temperature of the carbonization zone to 700°C or higher, carbonization can be easily promoted even when the second biomass contains a large amount of moisture. Furthermore, by setting the temperature of the carbonization zone to 1200°C or lower, it is possible to prevent components of the second biomass from partially melting and adhering to the inner wall of the combustion furnace 10.

[0038] The combustion furnace 10 may include an oxygen concentration meter 35 that measures the oxygen concentration in the combustion chamber 12, vertically above the second air supply port 16 and vertically below the exhaust port 19. Measuring the oxygen concentration in the carbonization region with the oxygen concentration meter 35 makes it possible to easily control the oxygen concentration. The oxygen concentration in the carbonization region may be approximately 0% to 7% by volume. By setting the oxygen concentration to 0% by volume or higher, carbonized material can be easily produced even when the second biomass has a high volatile content. Furthermore, by setting the oxygen concentration to 7% by volume or lower, the production of carbon dioxide due to combustion is promoted, making it possible to suppress a decrease in the amount of residual carbon.

[0039] The combustion furnace 10 and the boiler 40 are connected via a connection flow path 36. The product produced from the second biomass passes through the connection flow path 36, and the charred product is carried by the air current and continuously supplied from the combustion furnace 10 to the boiler 40. The connection flow path 36 connecting the combustion furnace 10 and the boiler 40 is not provided with a buffer or the like for storing charred product, and the charred product produced from the second biomass is continuously supplied to the boiler 40 together with the gas produced from the second biomass. In this embodiment, the connection flow path 36 branches, and the branched connection flow paths 36 are respectively connected to the multiple burners 43 of the boiler 40.

[0040] The connection flow path 36 is provided with a second biomass supply port 18b that supplies the second biomass into the connection flow path 36. When the second biomass is supplied into the connection flow path 36, a char is produced in the connection flow path 36. Specifically, the second biomass is supplied via the second biomass supply port 18b to a carbonization region where the second biomass is heated by the combustion of the first biomass and where a low-oxygen gas having an oxygen concentration lower than that of air is present due to the combustion of the first biomass. The connection flow path 36 is a high-temperature, low-oxygen atmosphere because gas from the combustion furnace 10 passes through it. By supplying the second biomass into such an atmosphere, a char can be stably produced from the second biomass, similar to when the second biomass is supplied into the combustion chamber 12 via the second biomass supply port 18a.

[0041] In this embodiment, the second biomass supply port 18 includes a second biomass supply port 18a provided in the combustion chamber 12 and a second biomass supply port 18b provided in the connection flow path 36. However, the second biomass supply port 18 may include only either the second biomass supply port 18a or the second biomass supply port 18b. In other words, it is sufficient for the second biomass supply port 18 to include at least either the second biomass supply port 18a or the second biomass supply port 18b.

[0042] The connecting flow path 36 may be provided with a third air supply port 37 that supplies air into the connecting flow path 36. The temperature inside the connecting flow path 36 may decrease due to energy consumption caused by pyrolysis of the second biomass. Furthermore, if the second biomass contains a large amount of moisture, thermal energy may be used to vaporize the moisture, causing the temperature inside the connecting flow path 36 to decrease. Therefore, by supplying air from the third air supply port 37 into the connecting flow path 36 and combusting part of the second biomass inside the connecting flow path 36, it is possible to suppress a decrease in the temperature inside the connecting flow path 36. This makes it possible to maintain the inside of the connecting flow path 36 at a temperature suitable for carbonization.

[0043] The third air supply port 37 may be provided in a position in the connecting flow path 36 closer to the second biomass supply port 18b than to the boiler 40. This makes it possible to widely create an atmosphere suitable for carbonization within the connecting flow path 36 from the second biomass supply port 18b to the boiler 40.

[0044] The air flow path 21 is connected to the third air supply port 37. The air flow path 21 branches between the blower 23 and the flow rate control damper 25. The branched air flow path 21 is provided with a flow rate control damper 26 and a flow rate control damper 28. By driving the blower 23 with the flow rate control damper 24, the flow rate control damper 26, and the flow rate control damper 28 open, air can be continuously supplied from the air intake port 22 through the third air supply port 37 into the connecting flow path 36.

[0045] The boiler 40 burns the product containing the char produced from the second biomass as fuel. The boiler 40 according to this embodiment can be an existing pulverized coal-fired boiler, coal-fired boiler, oil-fired boiler, or gas-fired boiler. The char contains char. The product may include, in addition to the char, gas and tar produced from the second biomass. The gas produced from the second biomass may include at least one selected from the group consisting of hydrogen, carbon monoxide, hydrocarbons such as methane, and tar.

[0046] The boiler 40 may combust the product produced from the first biomass as fuel in addition to the product produced from the second biomass. The first biomass is mainly combusted in the combustion furnace 10, but the product produced from the first biomass may also be continuously supplied from the combustion furnace 10 to the boiler 40 via the connecting flow path 36 as fuel for the boiler 40. The product produced from the first biomass may include char produced from the first biomass, gas and tar produced from the first biomass, etc. The gas produced from the first biomass may include at least one selected from the group consisting of hydrogen, carbon monoxide, hydrocarbons such as methane, and tar.

[0047] 1 and 3, the boiler 40 includes a furnace 41, a flue 42, and a burner 43. Combustion gas generated by burning a product as fuel in the burner 43 is discharged from the furnace 41 through the flue 42 to the outside.

[0048] The furnace 41 burns fuel to generate combustion heat. The furnace 41 according to this embodiment is a vertically shaped cylindrical structure, with the vertical length of the furnace wall being longer than the horizontal width. The furnace 41 is configured so that combustion gas generated by the combustion of the fuel rises within the furnace wall. The bottom 41a of the furnace 41 is connected to a clinker hopper (not shown), which stores clinker discharged from the bottom 41a of the furnace 41. The furnace 41 has a front wall 41b and a rear wall 41c disposed opposite the front wall 41b. Burners 43 are provided on the front wall 41b and the rear wall 41c.

[0049] The flue 42 is configured to guide combustion gas generated by the combustion of carbide-containing products in the furnace 41 out of the boiler 40. The flue 42 includes a horizontal flue 42a connected downstream of the furnace 41 and a rear flue 42b connected downstream of the horizontal flue 42a. The horizontal flue 42a is located downstream of the furnace 41 and is a section through which combustion gas discharged from the furnace 41 moves horizontally. The rear flue 42b is located downstream of the horizontal flue 42a and is a section through which combustion gas discharged from the horizontal flue 42a descends. Here, "downstream" refers to downstream in the flow direction of combustion gas during normal operation of the boiler 40. The flue 42 may be provided with a heat exchanger such as a superheater or a reheater. The combustion gas passing through the flue 42 may be treated in a treatment device such as a denitration device, a desulfurization device, or a dust removal device before being released into the atmosphere.

[0050] The burners 43 inject fuel together with air into the furnace 41 and combust the injected fuel within the furnace 41. The boiler 40 includes a plurality of burners 43, each of which is provided on a wall of the furnace 41. In this embodiment, a total of 18 burners 43 are provided on the front wall 41b of the furnace 41, with six burners 43 arranged horizontally and three rows in the vertical direction. Similarly, six burners 43 are provided horizontally and three rows in the vertical direction on the rear wall 41c of the furnace 41. Note that the front wall 41b and the rear wall 41c of the furnace 41 may be provided with air supply ports (not shown) that can supply air for two-stage combustion into the furnace 41.

[0051] In this embodiment, the product produced from the second biomass is supplied as fuel to all burners 43 provided in the boiler 40. However, it is sufficient if the product produced from the second biomass is supplied as fuel to at least some of the plurality of burners 43. For example, the product produced from the second biomass may be supplied to some of the plurality of burners 43, and a substance other than the product produced from the second biomass may be supplied to the remaining burners 43. Furthermore, each burner 43 may burn only the product produced from the second biomass as fuel, or may burn both the product produced from the second biomass and a substance other than the product produced from the second biomass as fuel. The substance other than the product produced from the second biomass may include, for example, at least one selected from the group consisting of coal, heavy oil, natural gas, petroleum refinery gas, blast furnace gas, coke oven gas, waste plastic, waste oil, and ammonia.

[0052] In this embodiment, an example has been described in which the boiler 40 includes the horizontal flue 42a and the rear flue 42b, but the boiler 40 is not limited to this configuration. The boiler 40 may be, for example, a tower boiler that does not include the horizontal flue 42a and the rear flue 42b. Furthermore, while Fig. 3 shows the opposed-fire boiler 40, the boiler 40 may also be a front-fire or swirl-fire boiler.

[0053] As described above, the combustion furnace 10 may be a fluidized-bed combustion furnace including a fluidized bed. In this embodiment, an example has been described in which the bed material 15 includes inert particles such as silica sand, forming a fluidized bed. However, the fluidized bed may also include coal ash. The coal ash may include at least one selected from the group consisting of clinker, cinder ash, and fly ash. By including coal ash in the fluidized bed, the coal ash, together with carbides, is continuously supplied from the combustion furnace 10 to the boiler 40 via the airflow. Coal ash can absorb substances that precipitate at low temperatures, such as tar, thereby preventing these substances from adhering to the inner surface of the connecting flow path 36. Biomass contains potassium and sodium, which lower the melting point of combustion ash. However, supplying coal ash increases the melting point of the ash, thereby preventing low-melting-point substances from cooling and adhering to the heat transfer surface. Clinker is agglomerated ash produced by boiler combustion. Cinder ash is coarse ash produced by boiler combustion. Fly ash is fine ash produced by boiler combustion. Coal ash is ash generated by combustion in a coal-fired boiler or a pulverized coal-fired boiler. The coal ash content in the fluidized bed may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% by mass. Ash other than coal ash may also be supplied to the fluidized bed. It is more effective to analyze the composition of such ash, determine whether it has properties that can be expected to have a melting point raising effect, and determine the mixing ratio in advance.

[0054] If necessary, the clinker may be crushed to a size of 1 mm to 3 mm, for example, and added to the fluidized bed in a sand-like state. By crushing the clinker to this size, the fluidity in the fluidized bed can be improved. Furthermore, by crushing the clinker to this size, the clinker particles collide with each other due to the flow of the fluidized bed and are further crushed, so that the clinker, together with the charcoal, is carried by the air current and continuously supplied from the combustion furnace 10 to the boiler 40. This makes it possible to prevent the ash of biomass, which has a low melting point, from adhering to the heat transfer surface and causing adverse effects.

[0055] Clinker may be supplied into the combustion furnace 10 when the combustion furnace 10 is extinguished. By supplying the clinker in this manner, the overall volume of the fluidized bed can be maintained within a predetermined range, and the amount of clinker supplied can be more accurately controlled. Furthermore, cinder ash and fly ash, which have small particle sizes, may be supplied mixed with at least one of the first biomass and the second biomass, or may be supplied alone to the connecting flow path 36. In this manner, the cinder ash and fly ash can be continuously supplied from the combustion furnace 10 to the boiler 40 along with the charcoal, carried by the airflow.

[0056] In this embodiment, one blower 23 is used to supply air to the biomass utilization system 1 through multiple air supply ports. However, blowers may be disposed upstream of the flow control dampers, and air may be supplied to the biomass utilization system 1 through each air supply port.

[0057] In order to suppress deposition of tar in the connecting flow passage 36, the connecting flow passage 36 may be formed as a double pipe or the like to suppress a decrease in temperature in the connecting flow passage 36.

[0058] [Second embodiment] Next, a biomass utilization system 1 and a biomass utilization method according to a second embodiment will be described with reference to Figure 4. As shown in Figure 4, in the biomass utilization system 1 according to the second embodiment, the connection flow path 36 includes a crushing section 39 that crushes carbonized material using an airflow. Unless otherwise specified, the other points are the same as those of the above embodiment, and therefore will not be described again.

[0059] In this embodiment, the crushing section 39 includes a branching section 39a, a confluence section 39b, and a flow path 39c connecting the branching section 39a and the confluence section 39b. The branching section 39a splits the char-containing product generated from the second biomass. At the confluence section 39b, the char-containing product split at the branching section 39a and flowing with the airflow joins. At the confluence section 39b, the char-containing product flowing with the airflow from the combustion furnace 10 joins and collides with the char-containing product, thereby being crushed.

[0060] In this embodiment, the pulverizing section 39 includes the confluence section 39b, which allows the carbide to be further pulverized. This allows the carbide to be further refined, which is expected to improve the transport efficiency of the carbide and the combustion efficiency of the carbide in the boiler 40. Note that in this embodiment, an example has been described in which the branch section 39a branches into two flow paths 39c. However, the number of flow paths 39c may be any plural number, such as an even number, and the branch section 39a may include three or more flow paths 39c.

[0061] In addition, in this embodiment, an example has been described in which the pulverizing section 39 includes the branch section 39a. However, the pulverizing section 39 may not include the branch section 39a, and the combustion furnace 10 and the junction section 39b may be connected by a plurality of connection flow paths 36. Even in this configuration, the carbide can be further pulverized.

[0062] In addition, in this embodiment, an example has been described in which the pulverizing section 39 includes the confluence section 39b. However, the pulverizing section 39 may also include a pipe bent at a right angle of 90 degrees. When the pipe for conveying the airflow is bent, the pipe is usually curved gently. However, by providing a pipe bent at a right angle of 90 degrees in the connecting flow path 36, the carbide can be caused to collide with the wall surface of the pipe, thereby promoting the pulverization of the carbide. In addition to these configurations, the pulverizing section 39 may also include a baffle plate or the like against which the carbide flowing on the airflow from the combustion furnace 10 collides and is pulverized.

[0063] As described above, in the biomass utilization system 1 according to this embodiment, the connection flow path 36 includes the crushing section 39 that crushes the charcoal by the flow of air. Therefore, the charcoal can be crushed with a simple configuration.

[0064] [Third embodiment] Next, a biomass utilization system 1 and a biomass utilization method according to a third embodiment will be described with reference to Figure 5. As shown in Figure 5, the biomass utilization system 1 according to the third embodiment includes a plurality of combustion furnaces 10, each of which is connected to a plurality of burners 43. Unless otherwise specified, the other points are the same as those of the above-described embodiments, and therefore will not be described again.

[0065] In this embodiment, the plurality of combustion furnaces 10 is composed of six combustion furnaces 10. As shown in Fig. 3, the boiler 40 according to this embodiment has three stages of burners 43 provided on the front wall 41b and three stages of burners 43 provided on the rear wall 41c. Of the six combustion furnaces 10, three combustion furnaces 10 are connected to the burners 43 on each stage on the front wall 41b via the connecting flow paths 36, and three combustion furnaces 10 are connected to the burners 43 on each stage on the rear wall 41c via the connecting flow paths 36.

[0066] In the biomass utilization system 1 according to this embodiment, the plurality of combustion furnaces 10 and the plurality of burners 43 are independently connected to each other via the plurality of connection flow paths 36. Therefore, by adjusting the flow rate of the product containing char supplied from each combustion furnace 10, it is possible to supply the boiler 40 with an amount of fuel according to the load of the boiler 40.

[0067] For example, the amount of product supplied from each combustion furnace 10 to the boiler 40 can be adjusted by increasing or decreasing the supply amount of the first biomass and the supply amount of the second biomass to each combustion furnace 10. In this case, it is preferable to adjust the ratio between the supply amount of the first biomass and the supply amount of the second biomass in consideration of the air ratio in the fluidized bed of the combustion furnace 10. Furthermore, by igniting or extinguishing some of the six combustion furnaces 10, it is possible to supply fuel to the boiler 40 in an amount corresponding to the load of the boiler 40. In this case, the operating conditions of each combustion furnace 10 may be substantially fixed.

[0068] Conventional gasification furnaces require a gasification furnace of the same level as the boiler 40 for gasification. On the other hand, in the biomass utilization system 1 according to this embodiment, the combustion furnace 10 generates a carbonization region where low-concentration oxygen gas exists, and the generated carbonized material is continuously supplied from the combustion furnace 10 to the boiler 40 by air currents. Therefore, the combustion furnace 10 can be made compact, and multiple combustion furnaces 10 can be easily connected to the burners 43 of the boiler 40, respectively.

[0069] In the present embodiment, an example has been described in which each combustion furnace 10 is connected to a burner 43 at each stage of the boiler 40. However, the biomass utilization system 1 is not limited to this configuration, and each combustion furnace 10 may be connected to each burner 43. For example, in the boiler 40 according to this embodiment, as shown in FIG. 3 , 18 burners 43 are provided on the front wall 41b and 18 burners 43 are provided on the rear wall 41c. That is, the combustion furnace 10 is composed of 36 combustion furnaces 10. Of the 36 combustion furnaces 10, 18 combustion furnaces 10 may be connected to each burner 43 on the front wall 41b via the connecting flow paths 36, and 18 combustion furnaces 10 may be connected to each burner 43 on the rear wall 41c via the connecting flow paths 36. Even in this configuration, by adjusting the amount of carbide-containing products supplied from each combustion furnace 10, it is possible to supply the boiler 40 with an amount of fuel corresponding to the load of the boiler 40.

[0070] As described above, the biomass utilization system 1 according to this embodiment includes a combustion furnace 10 having a first biomass supply port 17 for supplying first biomass and including a combustion chamber 12 for combusting the first biomass with air. The biomass utilization system 1 also includes a boiler 40 that burns a product containing charred material produced from a second biomass as fuel, and a connecting flow path 36 that connects the combustion furnace 10 and the boiler 40. The second biomass is supplied via a second biomass supply port 18 located downstream of the first biomass supply port 17 to a carbonization zone where the second biomass is heated by combustion of the first biomass and where low-oxygen gas having an oxygen concentration lower than that of air is present due to the combustion of the first biomass. The product passes through the connecting flow path 36, and the charred material is continuously supplied from the combustion furnace 10 to the boiler 40 by airflow.

[0071] The biomass utilization method according to this embodiment also includes a step of combusting, with air, first biomass supplied to the combustion chamber 12 of the combustion furnace 10. The biomass utilization method also includes a step of supplying second biomass to a carbonization zone downstream of the first biomass, which is heated by the combustion of the first biomass and in which low-oxygen gas having a lower oxygen concentration than air due to the combustion of the first biomass is present. The biomass utilization method also includes a step of combusting, as fuel in a boiler 40, a product containing charred material produced from the second biomass. The product passes through a connecting flow path 36 connecting the combustion furnace 10 and the boiler 40, and the charred material is continuously supplied from the combustion furnace 10 to the boiler 40 on an air current.

[0072] In the biomass utilization system 1 and biomass utilization method according to this embodiment, the second biomass is supplied to a carbonization zone where low-oxygen gas is present, and the boiler 40 burns the char-containing product produced from the second biomass as fuel. The product passes through the connecting flow path 36, and the char is continuously carried by the airflow and supplied from the combustion furnace 10 to the boiler 40. Therefore, according to the biomass utilization system 1 and biomass utilization method according to this embodiment, the char-containing product can be supplied directly to the boiler 40 and burned as fuel without having to crush the char using a crusher such as a biaxial crusher or hammer mill. Therefore, according to the biomass utilization system 1 and biomass utilization method according to this embodiment, the crushing equipment can be reduced or eliminated, or the wear on crushing parts can be reduced, thereby reducing the maintenance burden and enabling continuous production of boiler fuel.

[0073] Furthermore, in conventional gasification furnaces, sand is circulated for gasification, which can cause wear to the equipment. On the other hand, in the fluidized bed combustion furnace of this embodiment, the bed material 15 is simply flowing on the air distribution plate 13, so wear on the equipment is minimal. Therefore, the maintenance burden can be reduced compared to gasification furnaces.

[0074] The entire contents of Japanese Patent Application No. 2024-071144 (filing date: April 25, 2024) are incorporated herein by reference.

[0075] Although several embodiments have been described, the embodiments can be modified or varied based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined, unless they are mutually inconsistent.

[0076] The present disclosure can contribute, for example, to Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy for all" and Goal 13 "Take urgent action to combat climate change and its impacts" of the United Nations-led Sustainable Development Goals (SDGs).

[0077] REFERENCE SIGNS LIST 1 Biomass utilization system 10 Combustion furnace 12 Combustion chamber 15a Hearth 17 First biomass supply port 18 Second biomass supply port 36 Connecting flow path 39 Crushing section 39b Confluence section 40 Boiler

Claims

1. A biomass utilization system comprising: a combustion furnace having a first biomass supply port for supplying first biomass and including a combustion chamber for combusting the first biomass with air; a boiler for burning a product containing carbonized material produced from a second biomass as fuel; and a connecting flow path connecting the combustion furnace and the boiler, wherein the second biomass is heated by combustion of the first biomass via a second biomass supply port provided downstream of the first biomass supply port and is supplied to a carbonization region where low-oxygen gas having an oxygen concentration lower than that of the air due to the combustion of the first biomass is present, and the product passes through the connecting flow path, and the carbonized material is carried by an air current and is continuously supplied from the combustion furnace to the boiler.

2. The biomass utilization system according to claim 1, wherein the connecting flow path includes a crushing section that crushes the carbonized material by the flow of the air current.

3. A biomass utilization system as described in claim 2, wherein the crushing section includes a confluence section where the carbonized material flowing on the air current from the combustion furnace meets and collides with each other to be crushed.

4. A biomass utilization system according to any one of claims 1 to 3, wherein the combustion furnace has a hearth.

5. A biomass utilization system according to any one of claims 1 to 4, wherein the combustion furnace is a fluidized bed combustion furnace, a grate combustion furnace, or a rotary combustion furnace.

6. A biomass utilization system according to any one of claims 1 to 4, wherein the combustion furnace is a fluidized bed combustion furnace including a fluidized bed, and the fluidized bed contains at least one type of coal ash selected from the group consisting of clinker, cinder ash, and fly ash.

7. A biomass utilization system according to any one of claims 1 to 6, wherein the products include gas produced from the second biomass.

8. A method for utilizing biomass, comprising: a step of burning first biomass supplied to a combustion chamber of a combustion furnace with air; a step of supplying second biomass to a carbonization zone downstream of the first biomass, which is heated by the combustion of the first biomass and in which low-oxygen gas having an oxygen concentration lower than that of the air due to the combustion of the first biomass is present; and a step of burning a product containing charred matter produced from the second biomass as fuel in a boiler, wherein the product passes through a connecting flow path connecting the combustion furnace and the boiler, and the charred matter is carried by an air current and continuously supplied from the combustion furnace to the boiler.

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